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/ 
 
 PHYSICAL GEOGRAPHY 
 
 WILLIAM MOEEIS DAVIS 
 
 ■PROFESSOK OF PHYSICAL GEOGKAPHY IN HAKVABD UNIVERSITY 
 
 ASSISTED BY 
 
 WILLIAM HENRY SNYDER 
 
 MASTEK Ijr SCIENCE IN WORCESTER ACADEMY 
 
 Boston, U.S.A., and London 
 GINN & COMPANY, PUBLISHERS 
 
 1898 
 
 L. 
 
A OSS 
 
 ■J) ^7 
 
 21889 
 
 Entered at Stationers' Hall 
 
 Copyright, 1898, by 
 WILLIAM MOKRIS DAVIS 
 
 ALL RIGHTS RESERVED 
 
 '^*^7''''^^nfr^t>S^^$'^*^ 
 
 •» * r 
 
 ^ ^ 
 
PREFACE. 
 
 The successful development of Geography, considered 
 as the study of the earth in relation to man, must be 
 founded on Physical Geography, — or Physiography, as 
 it is coming to be called, — the study of man's physical 
 environment. No rational or scientific advance can be 
 made in the former without an appropriate preparation 
 in the latter. The earth's physical features must not 
 only be described, — they must be explained, so that the 
 understanding shall aid the memory in holding them in 
 mind. They must not be presented apart from the man- 
 ner in which they affect man's ways of living ; attention 
 must frequently be drawn to the association of human 
 conditions with the environment by which they have been 
 determined, in order to form the habit of looking at the 
 features of the earth as prime factors in guiding the 
 development of mankind. In brief, physiographic facts 
 should be traced back to their causes and forward to their 
 consequences ; and thus the phrase " causes and conse- 
 quences " comes to serve as a touchstone by which the 
 treatment of the subject may be tested. 
 
 It does not, however, seem advisable to make this test 
 absolute in an elementary book, for the causes 'of certain 
 important facts may be complicated, as is the case with 
 the atmospheric circulation ; or unknown, as in the con- 
 
•^ PREFACE. 
 
 fio-uration of the continents and in the uplift and depres- 
 sion of the lands; and the consequences of other facts 
 may be indirect or remote, as with the temperature of 
 the deep sea and the configuration of the sea bottoms. 
 Yet in all these cases the facts are so inherently physio- 
 graphic that they should not be omitted. Nevertheless 
 the test of " causes and consequences " has been, as far 
 as practicable, applied in the preparation of this book. 
 
 The subject of Physical Geography, or Physiography, 
 may be naturally divided into four parts : the earth as a 
 globe, the atmosphere, the oceans, and the lands. Extra- 
 neous subjects, however interesting or important in them- 
 selves, such as the non-geographical elements of astronomy, 
 the principles of physics, and the divisions of geological 
 time, are carefully excluded. When so much space is 
 demanded for the due consideration of strictly physio- 
 graphic matter, none can be afforded for irrelevant topics. 
 An examination of the book under such index headings 
 as agriculture, animals, forests, plants, etc., will show that 
 the organic environment of man, a large subject in itself, 
 is by no means neglected. It is touched upon because 
 it affords many excellent illustrations of the manner in 
 which the earth's physical features determine the distri- 
 bution of plants and animals, as well as of man ; but the 
 actual distribution of plants and animals, like that of 
 land forms or of nations, is not considered. 
 
 Regarding the earth as a globe, it is hoped that the 
 observational exercises suggested in the Appendix may 
 be undertaken even before geometry is studied; for in 
 no other way can so clear an understanding of such topics 
 as the form, size, and rotation of the earth, with their 
 
PBEFACE. V 
 
 applications in latitude and longitude, be obtained. Ob- 
 servational work of this kind may be mucli strengthened 
 if it is led up to by simple observations of the stars 
 in earlier years. Attention may be directed to the para- 
 graphs on the origin of the earth's shape, and the conse- 
 quences of its shape, size, and rotation, as illustrations of 
 the method of treatment above referred to. 
 
 The thorough study of the atmosphere demands a 
 knowledge of physics such as cannot be assumed on 
 the part of those for whom this book is intended. For 
 this reason the chapter on the atmosphere is made brief 
 and elementary. It should be supplemented by local 
 observations and by the construction and study of weather 
 maps, as suggested in Appendixes H and I. The atmos- 
 phere is of geographical importance chiefly through weather 
 and climate, and these subjects are repeatedly touched 
 upon in later chapters. 
 
 The study of the ocean affords less opportunity for 
 observation than the other divisions of the subject, but 
 its relation to climate is of great importance, the mono- 
 tony of the sea bottom may be effectively presented in 
 contrast with the variety of the lands, and the topics of 
 waves and tides are of much disciplinary value. 
 
 The lands have come to be the seat of the highest forms 
 of plant and animal life, as well as the home of man, 
 because of the variety of physical conditions that they 
 afford. It is therefore fitting that the largest part of a 
 book on Physical Geography should be devoted to this 
 part of the subject. Moreover, great progress has been 
 made in explaining the forms of the land during the 
 last half of the nineteenth century, and thus it has now 
 
VI PREFACE. 
 
 become possible to classify and describe land forms with 
 something of scientific accuracy. But as this method of 
 treatment is to a certain extent novel, it is entered upon 
 with careful choice of simple forms, such as coastal plains, 
 which are susceptible of elementary treatment, and the 
 first examples are presented deliberately. The meaning 
 of the various details of form is thus made so manifest 
 as to establish the expectation that all land forms may, 
 in due order, be rationally explained. At the same time 
 the products characteristic of various land forms, together 
 with the control that they exert over the location of settle- 
 ments and the distribution of industries, are directly asso- 
 ciated with the forms themselves, in order to emphasize 
 their human relations. In addition to the ideal type 
 forms that are frequently introduced, abundant reference 
 is made to actual examples of the types, and practical 
 value is thus given to a treatment that would otherwise 
 be too theoretical. Nearly every place thus mentioned 
 can be located by means of the small regional maps in 
 the text, or upon the maps at the end of the book; the 
 subject is thus made definite and specific. 
 
 Technical terms are avoided in nearly all cases. Geo- 
 logical processes, such as deformation and denudation, are 
 presented in as simple a manner as possible ; emphasis is 
 always given to the physiographic forms resulting from 
 the processes, and not to the processes themselves. The 
 insertion of a chapter on rivers and valleys in the latter 
 part of the book does not mean that these important 
 topics have not been encountered earlier ; they have been 
 mentioned wherever needed in connection with the pre- 
 ceding chapters, but certain features especially associated 
 
PREFACE. vii 
 
 with rivers are best taken up independently after the more 
 important land forms have been described, and to these 
 Chapter IX is devoted. 
 
 The study of the text on land forms should be supple- 
 mented as far as possible by appropriate observations in 
 the field. Nearly all schools can make occasional excur- 
 sions in which some of the activities of the lands (p. 99) 
 and some examples of typical land and water forms may 
 be examined. It is especially desirable that, at such times, 
 comparisons should be made between the locality visited 
 and its representation on the best available large scale 
 map, in order that some real appreciation of the art of 
 map reading may be acquired. After such a beginning 
 the maps referred to in Appendix M will have a greatly 
 increased value as illustrations of typical land forms not 
 accessible in the home district. For the same reason 
 written descriptions of localities visited should be pre- 
 pared by teacher and students ; thus the descriptions of 
 remote localities referred to in Appendix L will gain 
 increased reality. Photographs of scenes familiar on 
 home excursions will give a new value to photographs of 
 distant scenes, especially if both are exhibited by lantern 
 projection. 
 
 The opening paragraphs of each chapter are intended 
 to serve as reading lessons rather than as texts for study 
 and recitation. An outline of the subject may be pre- 
 sented in a brief course by omitting more or less of the 
 smaller-type text. The chapters on the Waste of the 
 Lands and the Chmatic Control of Land Forms may be 
 omitted in a short course. The topics discussed in the 
 Appendixes may be entirely disregarded if they seem too 
 
viii PEE FACE. 
 
 difficult for the pupils who are using the book ; they will, 
 on the other hand, be found useful extensions of the text 
 for more advanced classes. 
 
 The author has had the advantage of association with 
 Mr. W. H. Snyder, master in Science in Worcester (Mass.) 
 Academy, whose experience in teaching has been of much 
 assistance in adapting the text to the needs of secondary 
 schools. The proof-sheets have been examined by Mr. 
 M. Grant Daniell, late principal of Chauncy-Hall School, 
 Boston, Mr. W. C. Moore, instructor in Science in the 
 Salem (Mass.) Normal School, and Mr. H. C. Wood, in- 
 structor in Physical Geography in the Cleveland (Ohio) 
 High School, to whom the thanks of the author are due 
 for many valuable suggestions. 
 
 Cambridge, Mass., 
 September, 1898. 
 
CONTENTS, 
 
 CHAPTER PAGE 
 
 I. Introduction ......... 1 
 
 11. The Earth as a Globe ...... 8 
 
 III. The Atmosphere ........ 18 
 
 IV. The Ocean 57 
 
 V. The Lands 91 
 
 VI. Plains and Plateaus . . ". , . . . 113 
 
 VII. Mountains 159 
 
 VIII. Volcanoes 199 
 
 IX. Rivers and Valleys . . . . . . . 222 
 
 X. The Waste of the Land 263 
 
 XL' Climatic Control of Land Forms 297 
 
 XII. Shore Lines 347 
 
 Appendixes ......... 385 
 
 Index 419 
 
 Reference Maps ........ 430 
 
LIST OF ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 1. Dwarfs in the Equatorial Forest 3 
 
 2. Eskimo hunting Walrus 5 
 
 3. Eclipse of the Moon, showing the Curved Edge of the Earth's 
 
 Shadow 11 
 
 4. Height of Land and Depth of Sea compai'ed to Curvature of 
 
 Earth's Surface 14 
 
 5. Meridians and Parallels 17 
 
 6. Bedouins of the Sahara 18 
 
 7. Barometer 23 
 
 8. Grizzly Bears suffocated in Death Gulch, Yellowstone Park . . 26 
 
 9. Direct and Oblique Bays 26 
 
 10. The Comey Self-Recording Thermometer 27 
 
 11. Chart of Mean Annual Temperatures 28 
 
 12. Illustration of an Isothermal Line 29 
 
 13. The Planetary Circulation of the Atmosphere 30 
 
 14. Wet- Weather Streams of the Tarso Mountains, Sahara ... 31 
 
 15. Spiral Wind Courses 33 
 
 16. Isotherms for January 34 
 
 17. Isotherms for July 35 
 
 18. Diagrams of Terrestrial Winds for January and July .... 37 
 
 19. Winds of January 38 
 
 20. Winds of July . 39 
 
 21. Winds of the Atlantic Ocean in January and July 40 
 
 22. Chart of Equal Annual Range of Temperature 42 
 
 23. Monsoons of Northern Summer 43 
 
 24. Monsoons of Southern Summer 43 
 
 25. Chart of Annual Rainfall 46 
 
 26. Weather Map (first day) 50 
 
 27. Weather Map (second day) 50 
 
 28. Weather Map (third day) 51 
 
 29. Weather Map (fourth day) 51 
 
 30. An Ocean Steamship 57 
 
xii LIST OF ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 31. Land and Water Hemispheres 60 
 
 32. Sounding Instrument and Water Bottle 61 
 
 ■ 33. Deep-Sea Thermometers . . 61 
 
 34. Dredge ......'..' 62 
 
 35. Curves of Ocean Temperaturej i . . ' . ...."'... 64 
 
 36. A Vessel beset hy Pack Ice 65 
 
 37. An Iceberg 66. 
 
 38. Globigerina .................. 68 
 
 39. Temperatures of the Caribbean Sea 69 
 
 40. Section of Continental Shelf 70 
 
 41. Orbital Movement of Water in Waves 72 
 
 42. Surf 75 
 
 43. Chart of Ocean Currents 77 
 
 44. Displacement of a Vessel by Currents 78 
 
 45. Drift of Floating Objects by Currents 78 
 
 46. Currents of the Indian Ocean in July 80 
 
 47. Currents of the Indian Ocean in January 80 
 
 48. Temperatures on the Atlantic 82 
 
 49. High Tide 83 
 
 50. Low Tide 84 
 
 51. Diagram showing Progression of High Tide up a Bay . ... 85 
 
 52. Diagram of Tide Waves 85 
 
 53. The Tidal Wave, or Bore, in the Seine 87 
 
 54. A Floating Jellyfish 88 
 
 55. Deep-Sea Fish 89 
 
 56. Deep-Sea Crustacean '.X- -i ^ • t '• •■ • 89 
 
 57. Deep-Sea Sponge .•:...... 90 
 
 58. Height of Land and Depth of the Sea 94 
 
 59. A Quarry showing Weathered Rock 100 
 
 60. Granite 101 
 
 61. Pebbly Sandstone 102 
 
 62. Limestone with Fossil Shells 102 
 
 63. Beavers 107 
 
 64. Caribou 108 
 
 65. Jaguar 108 
 
 66. Tiger 109 
 
 67. Cassowary 109 
 
 68. Kangaroo 110 
 
 69. Southern New Jersey 113 
 
LIST OF ILLUSTRATIONS. xiii 
 
 FIG. PAGE 
 
 70. The Beach, Atlantic City, New Jersey 115 
 
 71. Mountains bordering the Sea . . . . .• . . . ." . . 117 
 
 72. Narrow Coastal Plain 119 
 
 73. Coastal Plain of Mexico 121 
 
 74. Coastal Plain of India 122 
 
 75. Broad Coastal Plain 123 
 
 76. Coastal Plain of the Carolinas ........ . . . 124 
 
 77. North Carolina Truck Farm . 126 
 
 78. Artesian Well 127 
 
 79. Diagram of. the Fall-Line . 128 
 
 80. Embayed Coastal Plain 129 
 
 81. A Branch of Chesapeake Bay, Maryland 131 
 
 82. A Belted Coastal Plain 132 
 
 83. The Coastal Plain of Alabama 134 
 
 84. Pine Forest on Coastal Plain, Alabama 135 
 
 85. Ancient Coastal Plain of Wisconsin 136 
 
 86. Ancient Coastal Plain of Ontario and New York 138 
 
 87. Diagram of Ancient Coastal Plain of Middle England . . . 139 
 
 88. A Plateau in Arizona 141 
 
 89. Diagram of Narrow Canyon ............ 142 
 
 90. Diagram of Widened Canyon 143 
 
 91. Diagram of a Waterfall in a Canyon 144 
 
 92. The Allegheny Plateau 147 
 
 93. Canyon of Kanawha River in Allegheny Plateau, West Virginia 148 
 
 94. The Enchanted Mesa, New Mexico 151 
 
 95. The Ozark Plateau, Missouri 154 
 
 96. Section of the Ozark Plateau 154 
 
 97. Broken Plateaus 155 
 
 98. Diagram of Blocked Plateaus 156 
 
 99. Hurricane Ledge 157 
 
 100. The Himalaya Mountains 159 
 
 101. Block Mountains 161 
 
 102. Mountains of Southern Oregon 162 
 
 103. A Dissected Mountain Range, Utah 165 
 
 104. Fractured Slopes of Rock Waste at Base of Mountain Range, 
 
 Nevada 166 
 
 105. Diagram of the Jura 168 
 
 106. Diagram of the Black Hills 170 
 
 107. Deadwood, a Mining Town in the Black Hills 171 
 
xiv LIST OF ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 108. Peaks of the Central Alps 172 
 
 109. An Alpine Ridge of Slanting Layers 173 
 
 110. An Avalanche Path, Selkirk Range, Canada 178 
 
 111. Path of an Ice Tall in the Alps 179 
 
 112. A Mountain of Down-Folded Layers 180 
 
 113. A Landslide in the Himalaya 182 
 
 114. Ibex 186 
 
 115. The Mountains of North Carolina 187 
 
 116. The Piedmont Belt, Virginia 189 
 
 117. Map of the Piedmont Belt, Virginia ....:.... 189 
 
 118. Diagram of the Allegheny Mountains, Pennsylvania . . . 190 
 
 119. Gorge of the Rhine in the Slate Mountains, Germany . . . 191 
 
 120. The Upland of New England, with Monadnock in the Distance 192 
 
 121. Valley of the Deerfield in the New England Upland .... 193 
 
 122. Model of Embayed Mountains 195 
 
 123. Diagram of Baraboo Ridge, Wisconsin 197 
 
 124. Vesuvius in Eruption 200 
 
 125. Monte Nuovo 202 
 
 126. The Cinder Cone and Lava Flow, California 204 
 
 127. Excavations in Herculaneum 206 
 
 128. A Volcanic Island (section and plan) 209 
 
 129. Lava Flows on the Plateaus of Arizona 210 
 
 130. The Lava Plateau of Idaho, Oregon, and Washington . . . 211 
 
 131. Diagram of a Caldera 212 
 
 132. Deception Island, a Volcanic Caldera (plan and section) . . 213 
 
 133. The Cone of Vesuvius in the Caldera of Monte Somma . . 213 
 
 134. Contour Map of Mount Shasta, California 214 
 
 135. Mount Shasta . 215 
 
 136. Mount Hood 215 
 
 137. Contour Map of Crater Lake, Oregon 216 
 
 138. Mount Johnson, near Montreal, Canada 217 
 
 139. Volcanic Necks, Arizona 217 
 
 140. Dissected Lava Plateau of Southern India 218 
 
 141. Diagram of a Young Volcano in the Background, changed by 
 
 Erosion to Lava-Capped Mesas in the Foreground . . . 220 
 
 142. Diagram of Dike and Mesa 221 
 
 143. Mohawk Valley ■ 223 
 
 144. Diagram of Cavern and Sink Hole 225 
 
 145. Natural Bridge, Syria 226 
 
LIST OF ILLUSTRATIONS. XV 
 
 FIG. PAGE 
 
 146. Diagram showing Distribution of Ground Water 227 
 
 147. A Geyser 229 
 
 148. Niagara Falls 231 
 
 149. Falls of the Yellowstone River 2-35 
 
 150. Diagram of Torrent with Falls and Reaches 236 
 
 151. Diagram of a Straight Valley 240 
 
 152. Diagram of a Crooked River widening its Valley .... 241 
 
 153. Contour Map of the Missouri River Valley 242 
 
 154. A Meandering River on the Plain of Hungary 244 
 
 155. Meanders of the Mississippi 245 
 
 156 a, b, c. Diagrams of a Shifting Divide 247 
 
 157. Diagram of Shifting River Divides 248 
 
 158. Diagram of Rearranged River Courses 248 
 
 159. Boundary of Georgia and South Carolina 249 
 
 160. Outline Map of Eastern France and Western Germany . . 249 
 
 161. Irregular Course of the Meuse in its Meandering Valley . . 250 
 
 162. Diagram Of a Narrowed Spur 253 
 
 163. Diagram of a Cut-Off Spur 254 
 
 164. Entrenched Meanders of the Neckar 254 
 
 165. Entrenched Meanders of the Moselle 255 
 
 166. Transverse and Longitudinal Streams 256 
 
 167. Transverse and Longitudinal Valleys 256 
 
 168. Watergap of the Susquehanna in North Mountain, Pennsylvania 257 
 
 169. Contour Map of the Susquehanna Watergap in North Momi- 
 
 tain, Pennsylvania . .' 257 
 
 170. Map of Narragansett Bay 260 
 
 171. The Hudson River, looking North from West Point . . . 261 
 
 172. Rock Waste on Mountain Slopes 264 
 
 173. A Lake-Floor Plain <' 265 
 
 174. Cliff and Talus 269 
 
 175. Land Slides in the San Juan Mountains, Colorado .... 270 
 
 176. The Slope of Pikes Peak 272 
 
 177. Alluvial Fans 276 
 
 178. An Eroded Valley 278 
 
 179. A Filled Valley 279 
 
 180. Flood Plain of Red River, Louisiana 280 
 
 181. A Terraced Valley 281 
 
 182. A Lake-Floor Plain . 281 
 
 183. A Warped Valley 282 
 
xvi LIST OF ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 184. A Waste-Filled Basin, Southern California 282 
 
 185. A Plain of Mountain Waste, Southeastern California . . . 283 
 
 186. A Meandering River, Vale of Kashmir 284 
 
 187. The Green River Basin, Wyoming 285 
 
 188. The Mississippi Flood Plain 287 
 
 189. View of River-Made Plain of Northern India 290 
 
 190. The Valley of California 291 
 
 191. The Delta of the Mississippi 293 
 
 192. Torrent Fan, Lake Geneva 295 
 
 193. Flood in Cherry Creek, Denver, Colorado . . , 300 
 
 194. Diagram of the Colorado River Delta 302 
 
 195. A River Valley in Desert Mountains, Peru 302 
 
 196. Bad Lands 303 
 
 197. The Waste-Filled Floor of Death Valley, Southeastern California 308 
 
 198. Half-Buried Mountain Range, Nevada 309 
 
 199. Home of the Farmer Ant 310 
 
 200. Diagram of Outward Drainage of Interior Basin, Himalaya . 312 
 
 201. Diagram of a Waste-Filled Trough . 313 
 
 202. Sand Dunes in Sahara 315 
 
 203. Buffalo 316 
 
 204. Loess Beds, Yellovv^ River Basin, China 317 
 
 205. Lakes Bonneville and Lahontan 319 
 
 206. The Yucca .320 
 
 207. Camel 321 
 
 208. El Kantara Oasis, Algerian Sahara 323 
 
 209. Rosegg Glacier in the Alps 327 
 
 210. Viesch Glacier in the Alps 328 
 
 211. Glacial Moraines, Sierra Nevada, California 331 
 
 212. Glaciated Area of the Northern United States 332 
 
 213. Diagram of an Ice Sheet 333 
 
 214. Diagram of a Retreating Ice Sheet 333 
 
 215. Glacial Moraines, North Dakota 335 
 
 216. An Esker 336 
 
 217. A Glacial Boulder 337 
 
 218. A Drumlin 338 
 
 219. The Glacial Lake Agassiz 340 
 
 220. Lake in the Adirondacks, New York 342 
 
 221. Ice- Worn Rocks, Coast of Maine . 344 
 
 222. Sea Cliffs, Grand Manan, New Brunswick ....... 348 . 
 
LIST OF ILLUSTRATIONS. xvii 
 
 PIG. PAGE 
 
 223. Diagrams of Coastal Plain Shore Lines 351 
 
 224. The Hooked Spit of Cape Lookout 352 
 
 225. A Tidal Inlet and Delta 353 
 
 226. The Sea Cliffs of Normandy 355 
 
 227. Valleys in the Cliffed Uplands of Normandy 356 
 
 228. Diagram of an L'regular Shore Line 358 
 
 229. A Delta in a Norwegian Fiord 359 
 
 230. The " Old Man of Hoy " 361 
 
 231. Cliffs and Deltas on an Irregular Shore Line 362 
 
 2.32. A Curved Shore Line 363 
 
 233. Diagram of a Eetreating Shore Line 364 
 
 234. Gibraltar 366 
 
 235. Easdale 367 
 
 236. Headlands and Bays 368 
 
 237. The Coast Platform of Norway 369 
 
 238. Deltas of the Texas Coast 371 
 
 239. Mangrove Tree 373 
 
 240. A Fringing Reef 374 
 
 241. A Barrier Reef 375 
 
 242. Part of the Great Barrier Reef of Australia . . . . . . 376 
 
 243. Diagram of Part of a Barrier Reef 377 
 
 244. Diagram of Part of an Elevated Reef 377 
 
 245. Diagram of Part of a Denuded Reef enclosed by a Barrier Reef 378 
 
 246. Diagram of Part of a Drowned Reef 378 
 
 247. A Large Atoll 379 
 
 248. An Atoll or Coral Island 380 
 
 249. Metia, an Elevated Coral Island 382 
 
 250. A Small Atoll 383 
 
 251. Globular Form of Earth shown by Visibility of Stars . . . 385 
 
 -" 252. Sun Altitudes on the Two Slopes of a Hill 386 
 
 --''^53. Sun Altitudes measured in a School Yard 386 
 
 254. Sun-Circle Method of Measuring Latitude 390 
 
 255. Latitude on a Spheroidal Earth 391 
 
 256. The Stereographic Projection 394 
 
 257. The Mercator Projection ,. 395 
 
 258. The Conical Projection 395 
 
 259. Representation of Relief by Hachures 396 
 
 260. Lines of Equal Magnetic Variation 399 
 
 261. The Tidal Problem 406 
 
ACKNOWLEDGMENTS OF ILLUSTRATIONS. 
 
 The following acknowledgments are due for the illustrations used in 
 this book. The sources of a very few cannot at present be determined 
 and are not acknowledged. 
 
 Adams, Prof. F. D., Fig. 138. 
 
 Caroline Island Eclipse Expedition, Fig. 248. 
 
 Dana, Coral Islands, Fig. 249. 
 
 Davis, Elementary Meteorology, Figs. 11, 16, 17, and 22. 
 
 Frye, Complete Geography, Figs. 30, 36, 53, 63, 64, 65, 66, 68, 84, 114, 
 115, 121, 136, 174, 189, 203, 204, 207, 209, 210, 222. 
 
 Gardner Collection of Photographs, Harvard University, Figs. 37, 42, 
 49, 50, 59, 100, 107, 108, 109, 113, 116, 120, 124, 127, 135, 143, 145, 147, 
 148, 149, 168, 171, 172, 176, 195, 197, 208, 218, 220, 229, and 242. 
 
 Giekie, Scenery of Scotland, Fig. 2-30. 
 
 Harvard College Astronomical Observatory, Fig. 3. 
 
 Harvard College Botanical Department, Fig. 206. 
 
 Harvard Geographical Models, Figs. 71, 72, and 122. 
 
 Heine, Prof., Fig. 111. 
 
 Knott, L. E., Apparatus Co., Figs. 7 and 10. 
 
 Lummis, Fig. 94. 
 
 Maryland Geological Survey, Fig. 81. 
 
 Mayer, A. G., Fig. 239. 
 
 Mississippi River Commission, Fig. 155. 
 
 Nansen, Eskimo Life, Fig. 2. 
 
 North Carolina Geological Survey, Fig. 77. 
 
 Eeport of the Challenger Expedition, Fig. 38. 
 
 Richards, Prof., Fig. 193. 
 
 Schirmer, Le Sahara, Fig. 6. 
 
 Schmidt's Atlas of Vesuvius, Figs. 125 and 133. 
 
 Stieler's Hand Atlas, Figs. 14 and 234. 
 
 Thomson, Voyage of Challenger, Fig. 34. 
 
 Three Cruises of the Blake, Figs. 55, 56, and 57. 
 
 Topographical Map of the German Empire, Figs. 164 and 165. 
 
 Topographical Map of France, Fig. 161. 
 
 U. S. Coast Survey, Figs. 191, 224, and 225. 
 
 U. S. Geological Survey, Figs. 8, 88, 93, 95, 99, 104, 126, 129, 134, 137, 
 139, 153, 169, 175, 196, 205, 211, 212, and 215. 
 
 Woodworth, W. McM., Fig. 54. 
 
PHYSICAL GEOGRAPHY. 
 
 c«3j@<oo 
 
 CHAPTER I. 
 INTRODUCTION. 
 
 The Relation of Man to the Earth. 
 
 Physical Geography treats of the many kinds of sur- 
 roundings that man finds in different parts of the world. 
 It describes the various features of the earth that influence 
 the manner in which man lives upon it. Hence it must 
 consider the form of the earth as a whole, the climates of 
 its different parts, the movements of its ocean waters, and 
 the forms of its lands ; it must give some account of the 
 rocks and soils that are characteristic of different kinds of 
 land forms, and it must explain the physical agencies that 
 control the distribution of plants and animals. When 
 the more important elements of this great subject are 
 learned, a good understanding may be gained of the way 
 in which climate, land forms, and other features of the 
 earth exercise a control over the habits and customs of 
 mankind. 
 
 For example, high temperatures must prevail around 
 the equator of a globe rotating and warmed like the earth 
 by the rays of a hot sun. The warm and moist air of the 
 equatorial belt will frequently be cloudy, and rain will 
 
2 . PHYSICAL GEOGRAPHY. 
 
 be plentiful. Vegetation will thrive in a region always 
 warm and moist; animal life will be abundant; but the 
 heat and dampness of the climate, the heavy forest growth, 
 and the abundance of animal life make such a region 
 unfavorable to the higher development of man. No people 
 native to the equatorial forests have ever advanced by 
 their own unaided efforts far towards the conditions of 
 civilization. 
 
 On the other hand, it will be found that on a globe 
 rotating like the earth a low temperature must prevail in 
 the polar regions where sunshine is weak, and snow will 
 be more common there than rain. As the snow gathers 
 on the polar lands and its under part is compacted into 
 ice, much of the surface will be frozen and barren. Plants 
 cannot flourish in so wintry a region, and land animals 
 cannot be numerous. It is easy to understand that the 
 people inhabiting polar lands must be surrounded by 
 unfavorable conditions, so that they cannot rise above a 
 low condition of life. 
 
 The following paragraphs present special illustrations 
 of these principles. 
 
 The Dwarfs of the African Forests. — The equatorial 
 belt of Africa is in large part a densely forested wilderness. 
 Tall trees spread their branches aloft, shading the ground 
 all the year with their heavy foliage. Vines and creepers 
 climb the trees and hang from bough to bough in great 
 festoons, and the shady and damp ground is covered by a 
 thick undergrowth of bushes with stems and branches so 
 closely interlaced that it is almost impossible to make 
 one's way through them without cutting a passage. Even 
 
INTRODUCTION. 
 
 the wild animals of the forest go and come by paths that 
 they keep open by frequent passing. Objects near at 
 hand are hidden from sight ; the explorer cannot tell 
 what is ahead of him in the gloom of the forest until he 
 is close upon it. Vegetation is here so luxuriant that it 
 is a burden upon the people who live amid its abundant 
 growth. 
 
 Some of the savages of this great forest are Dwarfs, 
 from three to four and a half feet in height. They do 
 
 Fig. 1. — Dwarfs in the Equatorial Forest. 
 
 not try to make clearings and to cultivate fields, but 
 search out the more open parts of the forest and build 
 their villages where the undergrowth is least dense. They 
 
4 PHYSICAL GEOGRAPHY. 
 
 have some trade with other tribes, but live chiefly by 
 hunting wild game, which is generally plentiful and of 
 great variety. Although entirely ignorant of many simple 
 arts practised by the people of more open countries, the 
 Dwarfs are expert in all the ways of forest life. They 
 can travel quickly through the woods, knowing all the 
 paths and open places. They protect their villages from 
 the attacks of neighboring tribes by planting sharpened 
 stakes in the paths that lead to them. They dig pitfalls 
 in the narrow forest paths, covering them with sticks and 
 leaves, and in this way capture even the larger wild ani- 
 mals. They prepare a poison from certain plants, and tip 
 their spears and arrows with it ; and in spite of their 
 small size, they are formidable enemies. 
 
 The Eskimos of Greenland. — How strikingly different 
 are the conditions of life in the cold, desolate regions of 
 Greenland ! Most of the land there is covered, all the 
 year round with ice and snow — a vast cold desert. A 
 narrow belt along the coast is free from snow in summer, 
 and here live a few tribes of Eskimos ; but the ground is 
 so barren that they get little support from it. The only 
 tree-like plants are of stunted growth, seldom over two or 
 three feet high. The herbage consists chiefly of mosses 
 and lichens, which grow for a time in summer when the 
 frozen ground is thawed for a few inches below the sur- 
 face. A small supply of wood comes from the trunks of 
 trees that are occasionally drifted by ocean currents from 
 warmer regions to Arctic shores ; but there is so little of 
 it that many articles which might be made of wood else- 
 where are here made from the bones of sea animals. 
 
INTRODUCTION. 
 
 Fig. 2. — Eskimo hnnting WalrDS. 
 
 The Eskimos travel in sleds drawn by dogs over the 
 snow-covered land or the frozen sea. They make slender 
 canoes, called kayaks, which they paddle very skilfully 
 when hunting seals and 
 walruses. Until visited 
 by Europeans and Ameri- 
 cans, the Eskimos were 
 as ignorant of the rest of 
 the world as were the 
 African Dwarfs; yet so 
 well have they learned to 
 take every advantage of 
 their frigid surroundings that they survive where men 
 from a more civilized nation, unused to living in so bar- 
 ren a region, might perish. 
 
 The Relation of Man to his Surroundings. — These brief 
 accounts of the Dwarfs and the Eskimos show very 
 clearly that, as a rule, the local features of the regions 
 in which they live exercise a strong control over their 
 manner of living. The Eskimos know nothing of forests, 
 pitfalls, and poisoned arrows. The Dwarfs know nothing 
 of snow and ice, sleds, kayaks, and harpoons. But each 
 of these groups of people has become well practised in 
 certain habits and customs that enable them to secure 
 food, shelter, and reasonable safety of life ; and these 
 habits and customs are closely related to the surroundings 
 in which they have been acquired. 
 
 The further the world is examined, the more general 
 this rule is found to be. Whether we read about the 
 wandering herdsman on the plains of western Siberia, or 
 
6 PHYSICAL GEOGRAPHY. 
 
 about the fisherman who sails to the banks of Newfound- 
 land, man is everywhere found making an effort to gain the 
 best advantage from his surroundings. In one region he 
 may be a savage, living in the rudest manner, ignorant of 
 all but the simplest arts ; each individual working in about 
 the same way as any other in the search for food and 
 shelter. Here the relation of man's habits to his sur- 
 roundings is easily understood. In another region he may 
 be one of a civilized nation, where great progress has been 
 made in the arts and sciences, and where each individual 
 gains his livelihood not by working independently, but by 
 doing -something that will serve the needs of many other 
 persons besides himself. Here the relation between man's 
 way of living and his surroundings may be very compli- 
 cated, but it may always be discovered by careful study. 
 
 Causes and Consequences. — It is the plan of this book 
 on Physical Geography to explain the cause or origin of 
 the more important kinds of physical features of the earth, 
 and to trace them to their consequences as seen in the 
 conditions of mankind. For example, deep valleys among 
 high mountains will be found to have their origin in the 
 long-continued action of weather and streams; The people 
 who live in such valleys are, in consequence of the enclo- 
 sure by lofty ridges, comparatively secluded from the rest 
 of the world ; hence they generally preserve old-fashioned 
 ways of living, which the peoj)le of a more open country 
 have given up for newer ways. Bays are in most cases 
 to be explained as drowned valleys ; that is, they result 
 from a slow sinking of the land, by which the waters of 
 the ocean are allowed to advance on the continental 
 
INTRODUCTION. 7 
 
 borders; the advance is further along the valleys than 
 elsewhere, and thus bays are formed on the coast line. 
 The quiet water of bay heads offers protected harborage 
 to shipping ; hence populous commercial cities are often 
 found bordering bay heads. The fine and deep soil of 
 many prairies is the sediment deposited on the bottom of 
 ancient lakes whose waters were long ago drained away ; 
 the soil of other prairies has been formed in an even more 
 peculiar manner. Pasturage and food plants thrive in fine 
 soil if the climate is favorable; hence the prairies of the 
 Mississippi valley, in the mid-temperate zone, have come 
 to be occupied by a great agricultural population. 
 
 There are numerous features of the world whose causes 
 and consequences are as striking and as important as those 
 just mentioned. Many of them will become familiar to 
 the student of this book. Many others will be found 
 if the student, when travelling over the world in later 
 years, seeks to understand the relation of man to the 
 earth. 
 
CHAPTER II. 
 THE EARTH AS A GLOBE. 
 
 The Relation of the Earth to Other Bodies. 
 
 Relation of the Earth to the Sun Few of the dis- 
 coveries ever made by man have been more ojoposed to 
 his early beliefs than that the earth turns on its axis once 
 a day, and that it moves around the sun once a year ; for 
 nothing is more natural than to suppose that the firm earth 
 stands still in the center of the universe, and that all the 
 bodies of the sky turn around it. What is more difficult 
 than really to conceive that we turn "upside down" every 
 day without knowing it, and that we are always rushing 
 along, 18.5 miles a second, or over one and a half million 
 miles a day, on our great annual journey of over 600,000,- 
 000 miles around the sun? 
 
 The sun, glowing with extreme heat, has the enormous 
 diameter of 866,500 miles. If the earth were placed at 
 the sun's center, and the moon were moving around the 
 earth at its present distance of 240,000 miles, the sun 
 would still reach almost 200,000 miles beyond the moon 
 on all sides. Even at the great distance of 93,000,000 
 miles, the sun gives abundant heat and light to the earth. 
 So huge a body is a fitting center for the earth to move 
 around. 
 
 The stars are distant suns, so exceedingly remote that a 
 ray of light, which travels from tlie sun to the earth in 
 
THE EARTH AS A GLOBE. 9 
 
 eight minutes, would be about three and a half years on 
 the journey to us from the nearest star. Many of the 
 stars are believed to be larger than the sun. 
 
 Relation of the Earth to Other Planets. — There are a 
 number of other bodies which, like the earth, move around 
 the sun. To the naked eye they look like stars, brighter 
 or fainter, according to their size and their distance from 
 the sun ; the telescope shows them to be of globular form. 
 Some of them are smaller, some larger than the earth. 
 Some of them turn on their axes more rapidly than the 
 earth, some much less rapidly. Some of them are nearer 
 to the sun than the earth is and some of them are further 
 away. Some of them move around the sun in a shorter 
 period and some in a longer period than that of the earth's 
 journey. These bodies are called planets. The brightest 
 are called Venus, Mars, Jupiter, and Saturn. It is thus 
 seen that the earth is not a solitary body, unlike all 
 others, but that it occupies an intermediate position in a 
 large family of bodies. 
 
 The sun and the planets form a group of bodies called 
 the solar system. As the stars resemble the sun in many 
 ways, it is believed that each star may be accompanied by 
 a larger or smaller family of planets ; hence the number 
 of earth-like bodies in the universe is probably very large. 
 
 Age of the Earth. — It is impossible to say what the age 
 of the earth and the solar system is, but it should be 
 reckoned in millions and millions of years. There is every 
 reason to believe that the sun and the planets existed for 
 an indefinitely long time before the earth was inhabited by 
 
10 PHYSICAL GEOGRAPHY. 
 
 plants and animals, and it is well proved that plants and 
 animals lived upon the earth for a vast length of time 
 before man appeared. It seems entirely possible that 
 other planets than the earth may have once been, or may 
 now be, occupied by inhabitants of some kind. 
 
 As the solar system has existed for so long a time in 
 the past, it may be expected to endure for an indefinitely 
 long time to come. Even after the sun has lost its heat 
 in the remote future, the planets may continue to wheel 
 around it, cold and lifeless. The part of a planet's exist- 
 ence during which it is inhabitable by life of any kind is 
 probably a relatively small fraction of the whole. It is 
 well that man, whose power over the other occupants of 
 the earth has come to be so great, should sometimes be re- 
 minded that the time during which he has been the chief 
 of its inhabitants covers a very small part of its history. 
 
 The Shape and Size of the Earth. 
 
 Shape of the Earth. — The people of savage races, 
 when they think at all about the shape of the earth, 
 generally believe it to be a great plain, broken by hills 
 and mountains and surrounded by the sea ; for that is the 
 appearance of the lands when seen from some high point, 
 with mountains rising to greater heights, lowlands extend- 
 ing to the seashore, and the ocean stretching beyond. 
 
 The people of an ignorant race usually regard the place 
 where they dwell as the center of the great earth plain. Of 
 the ocean they know little ; its further parts are invisible and 
 mysterious, and its limits are thought to be of a different 
 nature from the safe and solid lands. 
 
THE EARTH AS A GLOBE. 
 
 11 
 
 Among the earliest observations that led to a knowl- 
 edge of the true form of the earth are those made by 
 Greek philosophers in the fourth century, B.C. It was 
 noticed that in travelling a -few hundred miles north new 
 groups of stars came in sight over the northern horizon, 
 while stars that had been in sight over the southern hori- 
 zon could no longer be seen. When travelling south, 
 changes of the opposite kind were observed. It was 
 therefore concluded that the 
 surface of the earth must be 
 convex instead of flat, and 
 that the earth as a whole 
 must, be a sphere. (See Ap- 
 pendix A.) 
 
 The great philosopher, 
 Aristotle, who flourished 
 about the middle of the fourth 
 century, B.C., said that the 
 earth must be a sphere be- 
 cause when the earth's shadow 
 falls on the moon, causing a 
 lunar eclipse, the edge of the 
 shadow is a curved line. He added that the earth cannot 
 be a very large sphere, for otherwise the change in the 
 position of stars with respect to the horizon would not be 
 JO soon evident to one travelling north or south. 
 
 Fig. 3. — Eclipse of the Moon, showing the 
 Curved Edge of the Earth's Shadow. 
 
 The familiar argument for the globular form of the earth, 
 based ou the disappearance of the lower part of distant objects 
 at sea, was not mentioned by ancient writers until about the 
 beginning of the Christian era. 
 
12 PHYSICAL GEOGRAPHY. 
 
 Size of the Earth. — The earliest recorded measure men 
 of the size of the earth was made by a Greek philosopher 
 in the third century, B.C., who showed its diameter to be 
 about 8000 miles. (See Appendix B.) The knowledge 
 thus gained by the ancients concerning the shape and size 
 of the earth was afterwards forgotten for many centuries, 
 and was not regained until about the time of Columbus. 
 Since then voyages have been repeatedly made around the 
 earth, and its size has been accurately measured. 
 
 About two centuries ago it was discovered that the 
 earth is not a perfect sphere, but is very slightly flattened 
 at the poles. This was explained by Newton as a result 
 of the earth's rotation, and it may be taken as one of the 
 best proofs that the earth, and not the sky, turns round 
 once a day. 
 
 The distance from the earth's center to either pole is about 
 thirteen miles less than to the equator. This is so little in a 
 globe nearly 8000 miles in diameter, that if a curve were 
 drawn to represent the polar flattening, the unaided ey« 
 could not detect its difference from a circle. The most care- 
 ful measurements make the distance from center to pole 
 20,855,121 feet, and to the equator 20,926,062 feet. The 
 avera2:e diameter of the R'lobe is 7912 miles. 
 
 Origin of the Earth's Shape. — The eruption of hot lavas 
 from volcanoes supports the belief that the inner part of 
 the earth is so hot that the rocks there would yield 
 they were pressed more in one direction than in anoth 
 If the earth ever had an irregular shape, the higher pa: 
 would sink down on the yielding interior, and the lower 
 parts would be bulged out until the form became globular 
 and the pressure was everywhere balanced. 
 
 oi 
 
THE EARTH AS A GLOBE. 13 
 
 ■ Even if the entire earth were as cold as its outer part 
 (commonly called the crust), it could not preserve a very 
 irregular shape, for its inner rocks would not be strong 
 enough to withstand the unequal pressures that would exist 
 beneath the higher and lower parts. 
 
 But even if cold and rigid from surface to center, an irregu- 
 lar form could not endure ; for the surface rocks would decay 
 and crumble under the attack of the weather, and the loose 
 rock waste thus formed would be washed from the heights 
 into the hollows. The earth is so old that, whatever shape 
 it may have once had, and however cold and rigid its rocks, 
 it would long ago have been worn nearly smooth and 
 round. 
 
 It will be seen in a later chapter that all the higher parts 
 of the lands to-day, plateaus, mountains, and volcanoes, have 
 gained their height late in the earth's history. It may be 
 hundreds of thousands of years since they were formed, but 
 they are nevertheless young in the earth's measure of time. 
 If it had not been for the various forces by which the shape 
 of the earth's crust has been slightly changed, raising plateaus 
 and building mountains here and there, now and then, in its 
 long history, the surface of the earth would be much smoother 
 than it now is. 
 
 Consequences of the Size and Shape of the Earth. — The 
 
 earth is so large that savage peoples, even on the same 
 continent, may remain for centuries in ignorance of each 
 other. Each people comes to have its own way of doing 
 things appropriate to its surroundings. Thus differences 
 f language and customs have originated. But since rail- 
 ads and steamships have been invented by civilized 
 ]|eople in modern times, the earth may be considered a 
 relatively small planet. An active traveller may visit 
 nearly all its larger districts in his adult years. 
 
14 
 
 PHYSICAL GEOGRAPHY. 
 
 The civilized nations liave become well acquainted with 
 each other. They now maintain an international postal 
 service, by which nearly 200,000 post-offices are placed 
 in communication with each other. The Roman alpha- 
 bet is used by many nations, although their languages 
 may be different. The use of Arabic numerals is 
 even more extended. The metric system of weights 
 and measures is already widely introduced, and will 
 probably be adopted by all advanced nations in the 
 twentieth century. 
 
 Althougli the entire earth is large, if compared with the 
 size of a single state, the people of many distant countries 
 sell their home products to each other. The products of 
 remote regions are thus exchanged, even from as far as the 
 opposite sides of the earth. The wheat of one country fur- 
 nishes flour to another. Australian wool and meat are sold 
 in the markets of London. A. voyage round the world has 
 come to be regarded as hardly more than a pastime. 
 
 Although the lands have many mountains and valleys, 
 the general surface of the continents and oceans does not 
 depart greatly from the form of a smooth globe, as shown 
 
 100 MILES 
 
 Fig. 4. — Height of Land and Depth of Sea compared to Curvature of Earth's Surface. 
 
 in Fig. 4. This is most fortunate, for on a very unevei 
 and irregularly shaped earth long ascents and descents be 
 tween the higher and lower parts would make travel am 
 transportation enormously difficult and sometimes utterly 
 impossible. 
 
THE EABTH AS A GLOBE. '15 
 
 It is the attraction of the earth, or terrestrial gravity, 
 that causes bodies to have weight and to fall when not 
 supported. Recognizing the earth to be a globe, " down " 
 is towards its center, in the direction that bodies are pulled 
 by its attraction; "up" is away from the earth's center, 
 or against the pull of gravity. A level surface, like that 
 of a body of water at rest, is at right angles to up-and- 
 down, or vertical, lines. 
 
 The curved surface of the ocean is level, for it is every- 
 where at right angles to the direction of gravity. 
 
 It has been proved by experiment that the stems and 
 trunks of plants grow " up," because the force of gravity acts 
 downward. Even on hillsides trees tend to grow erect, and 
 not square out from the sloping surface. Branches, like those 
 of the spruce, that turn upward when young often droop 
 when old, owing to the long-continued action of gravity. 
 
 Many parts of the skeleton of man and animals, as well as 
 many of the muscles of the body, are especially developed to 
 bear the strain that is exerted upon them by the downward 
 weight of the body. The habit of lying down to sleep has 
 been formed partly in order to rest the muscles that are in 
 action while standing. 
 
 The Earth's Rotation and its Consequences. — The turn- 
 ing, or rotation, of the earth on its axis from west to east 
 gives us the impression that the sun, moon, and stars 
 move around the earth from east to west. One may gain 
 a false impression of the same kind while looking from 
 the window of a smoothly running train, when it may 
 almost seem as if the landscape moved backward instead 
 of the train forward. 
 
 The succession of sunlight and darkness, or day and 
 night, has given man and many animals the habit of 
 
16 PHYSICAL GEOGRAPHY. 
 
 working by day and resting by night. The period of the 
 earth's turning furnishes a natural unit of time, easily 
 recognized and counted, and everywhere constant. 
 
 Clocks and watches are regulated so as to keep time with 
 the turning of the earth. The hour hand turns once for the 
 average time of daylight and once for the average time of 
 darkness. 
 
 The rotation of the earth, causing sunrise and sunset, 
 suggests a natural system of directions even to many sav- 
 age tribes. The cardinal points, east and west, north and 
 south, are in a general way recognized by most people of 
 the world. 
 
 The sun rises through the eastern half of the sky during 
 the morning and sinks through the western half of the sky 
 in the afternoon. Midday is the moment when the sun passes 
 the north and south line that divides the eastern from the 
 western half of the sky. The sun then reaches the greatest 
 height above the horizon ; and hence at this moment a verti- 
 cal rod casts the shortest shadow. 
 
 Consequently, a true north line may be determined by 
 noting the direction of the shortest shadow cast by a vertical 
 rod. The north line thus determined would, if followed, lead 
 to the north pole ; a line in the opposite direction, to the south 
 pole. All such lines are called meridians, or midday lines. 
 When continued they form circles running around the globe 
 and intersecting at the poles. 
 
 Lines drawn at right angles to the meridians run east and 
 west. Such lines form circles parallel to one another, never 
 intersecting ; they are therefore called parallels. The parallel 
 that lies midway between the poles is called the equator, 
 because it divides the earth into equal parts, called the north- 
 ern and southern hemispheres. 
 
THE EARTH AS A GLOBE. 
 
 17 
 
 J^ovf'i^fc 
 
 A network of meridians and parallels may be in imagi- 
 nation drawn upon the earth's surface so as to divide it 
 in a regular manner with relation to the poles and equator. 
 It is in reference to these lines 
 that directions are accurately de- 
 fined and the relative positions 
 of various points determined by 
 explorers and surveyors. Thus 
 great advantage is taken of the 
 simple globular form and of the 
 regular rotation of the earth. 
 
 \\ \ \ PIxrallel / 
 
 ^outh i'ul" 
 
 Fig. 6. — Meridians and Parallels. 
 
 Land surveys, by which the 
 boundary lines of farms and house 
 lots are marked out, are best made 
 with reference to the local meridian. Navigators constantly 
 have occasion to determine their position with respect to the 
 network of meridians and parallels, in order to avoid islands 
 and headlands and to reach their desired ports. (See Ap- 
 pendix C.) 
 
 The boundaries of thinly settled parts of civilized nations 
 and states are often defined by -meridians and parallels, as 
 between the western parts of the United States and Canada, 
 as well as between many of the states themselves, and between 
 the various parts of Canada and of Australia. 
 
 (Further account of the earth as a globe is given in the 
 Appendices C, D, E.) 
 
CHAPTER HI. 
 THE ATMOSPHERE. 
 
 The Relation of Man to Climate. 
 
 The Bedouins of the Sahara. — The uplands and low- 
 lands of a great part of northern Africa receive so little 
 rainfall that their surface is dry and barren, forming the 
 great desert of Sahara. Cultivation of the ground is 
 impossible, except close to the dwindling streams, which 
 
 Fig. 6. — Bedouins of the Sahara. 
 
 wither away as they flow from the higher ground where 
 most of the little rain falls. Nearly all the region is unin- 
 habited, — a desolate waste of rock, stones, and sand, — 
 but here and there the under soil in the low ground is 
 moist enough to support a scanty growth of grass, which 
 gives subsistence to the horses and camels of the wander- 
 ing tribes of Bedouins. These people must frequently 
 
THE ATMOSPHERE. 19 
 
 move from place to place to avoid, starvation; hence they 
 do not build houses, but live in tents that can be easily- 
 carried about as they wander from one pasture ground to 
 another. As a result of their wandering habits, they 
 have come to be excellent horsemen and show great 
 endurance in surviving the hardships that they must 
 often suffer. But, on account of being nearly destitute, 
 they have the habit of taking what they want from any 
 passing travellers whom they can plunder. They have 
 thus preserved into modern times a rude manner of life 
 that must have been universal in the early history of 
 mankind, but that has been given up in recent centuries 
 by the people of more advanced nations, where theft is 
 now punished as a crime. 
 
 One might expect that the Bedouins, on learning some- 
 thing of the rest of the world from the traders of passing 
 caravans, would wish to leave the barren Sahara for more 
 fertile lands. On the contrary, so accustomed are they 
 to a wandering life that they have no desire to change it. 
 They persevere in the miserable conditions of the desert, 
 content with their own ways and disliking the intrusion 
 of strangers. Their manner of living is, like that of the 
 Dwarfs in the equatorial forests and of the Eskimos in 
 Greenland, another example of the great influence that 
 climate exerts on the habits and customs of mankind. 
 Just as the warm and moist climate of the equatorial forest 
 and the frigid climate of Greenland are natural results of 
 the form and rotation of the earth, so the dry climate of 
 the Sahara is a natural result of the movements of the 
 atmosphere on the rotating earth, warmed around the 
 equator by a hot sun. 
 
20 PHYSICAL GEOGRAPHY. 
 
 Climate and Commerce. — The growth and distribution 
 of plants are controlled by temperature and rainfall. Tea, 
 coffee, cane-sugar, cotton, and bananas are the products of 
 plants that flourish best in a warm and rather moist cli- 
 mate. The less intelligent peoples of the cooler and drier 
 parts of the world know nothing about these useful pro- 
 ducts, and use something else in their place ; but the more 
 intelligent peoples of such regions, once having learned 
 how valuable these plant products are, take great trouble 
 to procure them. An important part of commerce is the 
 traffic in articles of food raised in distant parts of the 
 world. Tea is carried overland from China to Russia; a 
 railroad now in construction will soon make this trade 
 more active. Great cargoes of tea are shipped from China 
 and Japan to our Pacific ports, and then sent forward in 
 long freight trains over the mountain passes to the prairies 
 and the eastern states. Steamships run from the West 
 Indies to our Atlantic ports, laden with tropical fruits. 
 The cotton crop of the southern states has been for many- 
 years their most valuable product. All of it was formerly, 
 and most of it is still, sent to the mills of Old and New 
 England, where thousands of persons gain a living by 
 spinning thread and weaving cloth; but in recent years 
 some of the crop has been manufactured in southern mills. 
 Many articles of clothing, the sails of ships, and the tents 
 of armies are made from the cotton fiber. New inventions 
 often increase the demand for the cloth and promote the 
 cultivation of the cotton fields ; none being more notable 
 than the bicycle, whose rubber tires have a layer of cotton 
 duels:. Thus the climate, the commerce, and the industries 
 of the world are intimately associated. 
 
THE ATMOSPHERE. 21 
 
 Effects of Weather Changes. — Even temporary weather 
 changes may be of great importance when the ordinary 
 variations of temperature, rainfall, and wind are exceeded. 
 In summer hot winds blowing from the southwest some- 
 times blight the crops of Kansas and Nebraska. In winter 
 cold winds occasionally sweep down from the northwest 
 and carry freezing temperatures as far as Florida, ruining 
 the orange crop. Unusual drought may injure the growth 
 of wheat, as during the winter and spring of 1898 in 
 California. Excessive rains may flood the lowlands near 
 the greater rivers, as along the lower Mississippi in the 
 spring of 189T, when an area of 13,000 square miles (as 
 much as that of Massachusetts and Connecticut, and 
 more than that of all Belgium) was overflowed, and the 
 destruction of live stock and crops caused losses exceed- 
 ing $12,000,000. Violent winds may beat down the 
 cornfields in their path, and the loss thus occasioned on 
 a farm may prevent the purchase of better farming 
 machinery for the next year. Storms at sea may help to 
 turn the course of history, as when a gale aided in dis- 
 persing the Spanish " Armada " on the British coast in 
 1588, during the reign of Queen Elizabeth. 
 
 The harmful happenings of wind and rain are not to be 
 prevented ; but it is possible that the injury they sometimes 
 cause may be lessened when their coming is better fore- 
 told, and when protection against their dangers is better 
 planned. The prediction of cold winds by the Weather 
 Bureau often gives farmers and merchants warning in 
 time to guard their property against freezing. Irrigating 
 canals, leading water from streams out upon dry fields, 
 decrease the dangers of droughts ; famines are thus averted 
 
22 PHYSICAL GEOGEAPHY. 
 
 in the great population of India. Dikes built near the 
 banks of rivers prevent their overflow; the twentieth cen- 
 tury may see the Mississippi thus controlled, as the Rhine 
 has been controlled in the nineteenth century. Storms at 
 sea have lost more than half their dangers, partly because 
 sea-going vessels are now much stronger than formerly, 
 partly because the movements of storms are now better 
 known, so that their coming can be foreseen and their 
 greatest fury avoided. An early navigator might have 
 steered his vessel into the midst of a hurricane ; the mod- 
 ern sea captain has been taught how to turn to one side 
 of its probable course. 
 
 Weather changes are by no means always unfavorable. 
 An early spring, a warm summer, and a sufficient rainfall 
 promote an abundant harvest; and in such a season of 
 plenty the farmer receives a good return for his labor. 
 He is then enabled to carry out improvements in his farm 
 buildings, to clear and plow new fields. Years of pros- 
 perity are thus connected with years of good weather, and 
 great as well as small events are influenced by them. 
 
 The Atmosphere. 
 
 The Atmosphere is a light and transparent mixture of 
 gases known as air. It rests on the lands and seas, 
 forming the outermost part of the earth. Many processes 
 that take place on the surface of the lands and seas result 
 from the action of the atinosphere. The waves and cur- 
 rents of the oceans are caused by the winds ; the soil that 
 covers the greater part of the lands results from the decay 
 of the underlying rocks chiefly through the chemical 
 
THE ATMOSPHERE. 
 
 23 
 
 action of moist air. Rainfall, so important in many ways, 
 is entirely supplied by moisture carried from the oceans 
 by the movements of the atmosphere. 
 
 The atmosphere far overtops the highest mountains. Me- 
 teors, or "falling stars," — small scraps of matter dashing 
 toward the earth from distant space, — some- 
 times burn at heights of over a hundred miles, 
 showing that some air reaches that great altitude. 
 
 Cloud, haze, and dust make the lower air tur- 
 bid, and often cut off a great part of the sui 
 rays; but when the atmosphere is clear, even tl 
 faint light of stars penetrates its entire depth. 
 
 Pressure of the Atmosphere. — Although t] 
 air is invisible, it is attracted by the earth ai I 
 exerts a pressure on the surface upon which 
 rests. This pressure is about a ton on a squa 
 foot. The pressure on a man's body amouni 
 to several tons ; but this is not felt, because tl 
 air within the body exerts a correspondii 
 pressure outward. The air is so easily mov( I 
 that little resistance is noticed when walkir 
 through it, but fast trains on railroads a 
 much impeded by the resistance of the a 
 that they have to push aside. 
 
 The pressure of the atmosphere is determini 1 
 by the barometer, in which the air pressure 
 balanced by that of a column of mercury about 
 thirty inches high. The ordinary changes of 
 atmosphei^ic pressure, such as accompany changes ^'e- ''■ 
 
 of weather, are seldom more than a fifteenth of 
 the total pressure. If a barometer is carried up a mountain, 
 leaving much of the atmosphere beneath it, the pressure of 
 
24 PHYSICAL GEOGRAPHY. 
 
 the overlying atmosphere is found to be much reduced. An 
 ascent of a thousand feet causes a lowering of about an inch 
 in the barometric column. Even the slight loss of pressure 
 caused by going from the ground floor to the top of a build- 
 ing is easily recognized with a good instrument. 
 
 Although very light, the air supports the flight of birds 
 and insects. The wind drives sailing vessels and windmills ; 
 it carries about myriads of germs and pollen grains, as well 
 as particles of mineral dust. In dry regions, where the land 
 is not covered with vegetation, the shape of the surface is 
 changed by the long-continued action of the wind in drifting 
 sand and dust from place to place. 
 
 Air is extremely elastic, changing its volume with every 
 change of pressure. Its lower part is compressed by the 
 weight of the overlying part, so that a cubic foot of air 
 at sea level weighs about 0.075 pound, while at three 
 miles above sea level its weight would be only half as 
 much; and at an altitude of a hundred miles the air must 
 be almost imperceptible. 
 
 Men and animals living on high plateaus have become 
 accustomed to the rarity of the air around them. There are 
 villages on the plateau of Tibet where the density of the air 
 is little more than two-thirds that at sea level. Mountain 
 climbing above altitudes of 20,000 feet is almost impossible 
 from the difficulty of breathing the thin upper air. 
 
 It is by slight wave-like movements in the air that sound 
 is transmitted. So easily is the air disturbed that a locust 
 (cicada) may set hundreds of tons of air vibrating perceptibly 
 to our nerves of hearing. When the volcano Krakatoa, be- 
 tween Java and Sumatra, exploded in August, 1883, sounds 
 were heard for 3000 miles, and atmospheric waves, detected 
 by slight changes of pressure in barometers, passed three 
 times round the earth. 
 
THE ATMOSPHERE. 25 
 
 Composition of Air. — Air consists of a uniform mixture 
 of gases, in wliich a small and variable quantity of water 
 vapor is usually present. The gases are nitrogen, about 
 four-fiftlis ; oxygen, about one-fifth ; argon, carbonic acid, 
 krypton, and some others, each a hundredth or less. 
 
 Nitrogen is found , in much larger share in the air than in 
 all the rest of the earth, but it does not seem to be actively 
 useful. Argon and krypton, recently discovered, are at present 
 known only in the atmosphere. 
 
 Water vapor, originally supplied by evaporation from the 
 oceans, is the source of rainfall and the supply of all streams. 
 The air feels damp or dry according to the amount of water 
 vapor that it contains. When damp in hot weather, the air is 
 sultry and uncomfortable ; when damp in cold weather, it is 
 chilly and disagreeable. The same temperatures would be 
 much more easily borne if the air were dry. 
 
 All plants and animals take in air and use some of its 
 oxygen to combine with part of their substance in a very 
 slow combustion, which produces a slight amount of heat 
 but no fire. Thus all forms of life, animal and vegetable, 
 gain the energy with which they are enabled to perform 
 their life work. 
 
 Plants do much less work and use much less oxygen than 
 animals. The process of taking in a portion of air and giving 
 out the unused part along with the products of the slow 
 internal combustion (water vapor and carbonic acid) is called 
 respiration, or breathing. It continues day and night. The 
 organs of respiration differ greatly in different forms of life, 
 but the process is much alike in all. 
 
 Fire is the result of an active combination of some combus- 
 tible substance with the oxygen of the atmosphere. The heat 
 thus developed may convert water into steam, and the expansive 
 
26 
 
 PHYSICAL GEOGRAPHY. 
 
 force of the steam may be used to drive engines and many 
 kinds of machinery. 
 
 Carbonic acid, although a small part of the atmosphere, 
 is of great impor- 
 tance as the chief 
 food of plants. It 
 is taken in by the 
 green cells and de- 
 composed under 
 the action of sun- 
 light, part of it 
 (carbon) being re- 
 tained to unite 
 with the sap and 
 form the tissue 
 of the plant, part 
 (oxygen) being 
 given out again. 
 
 Fig. 8. 
 
 Grizzly Bears suffocated in Death Gulch, 
 Yellowstone Park. 
 
 Carbonic acid is suffocating if present in much larger 
 quantity than usual. It is given forth from the ground in 
 
 Fig. 9. — Direct and Oblique Says. 
 
 certain parts of the world, as in Death gulch, Yellovt^stone 
 Park. Grizzly bears often lose their lives in this ravine. 
 
THE ATMOSPHERE. 
 
 27 
 
 Temperature of the Atmosphere. — ^The temperature of 
 the land and sea surface and of the lower atmosphere is 
 controlled by the sun's rays. Hence higher temperatures 
 must prevail around the equatorial belt, where the sun 
 shines more directly upon the earth's surface ; and areas 
 of low temperature must be found around the poles, 
 where the sun's rays are oblique, as shown in Fig. 9. 
 Belts of stronger, medium, and 
 weaker sunshine are thus de- 
 fined, which are known as the 
 torrid, temperate, and frigid 
 zones. (See Appendix F.) 
 Fortunately the cold or frigid 
 areas around the poles occupy 
 a relatively small part of the 
 world. 
 
 The temperature of the air 
 may be measured by a ther- 
 mometer suspended so as to be 
 protected from direct sunshine 
 and from rain or snow. If 
 placed outside of a window, it should be on the north side 
 of the building, where currents of warm air escaping from 
 windows beneath cannot affect it. Some thermometers are 
 arranged so as to give a continuous temperature record in a 
 curve drawn on a sheet of paper ; such instruments are called 
 thermographs, one pattern being shown in Fig. 10. 
 
 The temperature of the air is not much affected by the 
 direct action of the sun's rays ; it is controlled largely by the 
 temperature of the land or sea surface on which the air rests. 
 Zones of high and low temperature are therefore found in the 
 lower atmosphere from the equator to the poles, but the upper 
 atmosphere is everywhere cold. At the height of ten or more 
 
 Pig. 10. 
 
 - The Comey Self-Eecordlng 
 Thermometer. 
 
28 
 
 . PHYSICAL GEOGRAPHY. 
 
 miles, the air above the equator is probably little warmer than 
 that over the poles. 
 
 Temperature Charts. — The distribution of the average 
 temperatures for the year is shown on the chart of the 
 world, Fig. 11. A line drawn near the earth's equator, 
 through the middle of the belt of greatest heat, is called 
 
 Fig. 11. — Chart of Mean Annual Temperatures. 
 
 the heat equator, the average temperature of which is about 
 80°. From the heat equator the temperature decreases 
 toward each pole at the rate of about a degree of the 
 Fahrenheit thermometer scale to a degree of latitude. 
 
 The distribution of temperature on charts, such as Fig. 11, 
 is indicated by lines drawn through places having the same 
 temperature, and separating regions of higher and lower tem- 
 perature. Fig. 12 gives the degrees of temperature prevailing 
 over the middle and eastern United States on a certain morn- 
 ing. The broken line is drawn so as to separate all places 
 
THE ATMOSPHERE. 
 
 29 
 
 -7-9 -<i> 
 
 having higher temperatures than 40° from those having lower 
 temperatures. Similar lines may be drawn for temperatures 
 of 10°, 20°, 30°, 50°, and 60°. Such lines are called isothermal 
 (equal temperature) lines, or isotherms. 
 
 Circulation of the Atmosphere. — Cold air from the polar 
 regions, being heavier than the warm lower air of the torrid 
 zone, continually 
 tends to creep under 
 it ; and the warm air 
 thus lifted up tends to 
 overflow towards the 
 poles. A permanent 
 interchanging move- 
 ment, or circulation, is 
 thus established in the 
 atmosphere between 
 the warmer and colder 
 parts of the earth. 
 On account of the 
 earth's rotation, the 
 air currents, or winds, 
 do not flow directly north and south, but are turned some- 
 what to the east or west. (See Appendix G.) 
 
 A circulation will be established by opening a door between 
 two rooms, one warm and the other cold. The cold air will 
 creep into the lower part of the warm room, while the warm air 
 will spread into the upper part of the cold room. The move- 
 ment may be shown by the drift of smoke from a smouldering 
 match. If the cold air is warmed as it enters the warm room, 
 and the warm air cooled as it enters the cold room, the circu- 
 lation will continue indefinitely. 
 
 Fig. 12. — niustration of an Isothermal Line. 
 
30 
 
 PHYSICAL GEOGRAPHY. 
 
 Planetary Winds. — The most important members of 
 the atmospheric circulation on our planet may be briefly 
 described as follows. The trade winds blow from about 
 latitude 28° N. and g. 
 obliquely towards the equa- 
 tor, in the northern hemi- 
 sphere from the northeast, 
 in the southern from the 
 southeast.^ The prevail- 
 ing westerly winds blow 
 from a westerly source, but 
 with a slight inclination 
 towards the pole, over the 
 greater part of the tem- 
 perate zones. The polar 
 winds, occupying rela- 
 tively small areas around each pole, are little known. 
 Belts of light, variable winds and frequent calms lie 
 between the several belts of steadier winds. All 
 these are members of what may be called the planetary 
 circulation. 
 
 The trade winds are so called from the constancy with 
 which they follow a steady or " trade " course. Their 
 velocity is from ten to thirty miles an hour. They give 
 fair weather, seldom interrupted by storms, and generally 
 dry unless a mountain range rises across their path. Low- 
 lands over which they blow are made desert by the drying 
 action of their warm air. The African Sahara and the 
 central Australian deserts are thus explained. 
 
 Fig. 13. — The Planetary Circulation of the 
 Atmosphere. 
 
 1 Winds are named from the point of the compass from which they 
 blow. 
 
THE ATMOSPHERE. 
 
 31 
 
 When sailing vessels enter the trade-wind belt, they may- 
 count upon making good headway. If sailing with the winds, 
 extra sails are often rigged out on the ends of the yards, and 
 thus aided by a broadened stretch of canvas, the vessels speed 
 along day and night. 
 
 Where the trade winds encounter mountain ranges, they 
 . are forced to ascend the .side on which they approach. As 
 they rise the air expands, cools, and becomes cloudy and rainy. 
 The eastern slope of the Andes about the headwaters of the Ama- 
 zon, the mountains 
 along the east coast of 
 Brazil under the south- 
 east trades, and the 
 eastern slopes of the 
 highlands of Mexico 
 and Central America 
 under the northeast 
 trades, thus receive a 
 good amount of rain- 
 fall (80 to 100 inches 
 a year). All these 
 mountain slopes bear 
 heavy forests. (See 
 Appendix H.) 
 
 The further slope 
 of the mountains, where the winds descend, is relatively dry 
 and barren, as on the western side of the Peruvian Andes. 
 
 Even in the Sahara the few mountains that interrupt the 
 general surface receive a sufficient rainfall to permit tree 
 growth; but the streams supplied on the mountain sides 
 wither away after descending to the lower desert. 
 
 The prevailing westerlies are much less regular than the 
 trades. They may weaken to less than ten miles an hour, 
 or strengthen to gales of sixty miles an hour. They often 
 shift from their general course to take part in irregular 
 
 Fig. 14. 
 
 - Wet-Weather Streams of the Tarso Mountains, 
 Sahara. 
 
32 PHYSICAL GEOGBAPHY. 
 
 movements, indicated in the temperate latitudes of Fig. 13. 
 It is chiefly to these great whirl-like movements that the 
 frequent changes of weather in temperate latitudes are due. 
 
 The lands under the westerly winds are generally well 
 watered, especially on bold coasts east of the oceans. Abun- 
 dant rainfall is received on the mountainous Pacific slopes of 
 North and South America in middle latitudes, but the oppo- 
 site slopes are comparatively dry. In these latitudes the 
 western slope of the mountains is heavily forested, while 
 the eastern slope has an open tree growth, or none. The 
 distribution of forests over the great American mountain sys- 
 tem thus gives striking illustration of the relation of timber 
 supply to winds and rainfall. 
 
 The belt of calms and light breezes in the neighborhood 
 of the equator, between the inflowing trade winds, is called 
 the doldrums^ or equatorial calm belt. It is prevailingly 
 cloudy ; rain falls every day or two, especially in the late 
 afternoon or night. The lands are heavily forested under 
 this warm and moist belt, and agriculture is difficult from 
 the very luxuriance of vegetation. 
 
 Sailing vessels bound across the equator are frequently 
 becalmed for several days in the doldrums. They must then 
 take advantage of every light breeze to push onward and reach 
 the trade winds beyond. The dull sky, the sultry air, and the 
 glassy sea make the delay all the more vexatious. 
 
 The rain of the doldrums results from the slow ascent of 
 the warm air supplied by the inflowing trade winds. The 
 lower air is raised to greater and greater height by the inflow 
 of more air beneath from both sides ; it expands as it rises, 
 cools as it expands, becomes cloudy as it cools, and thus gives 
 forth plentiful rain. Violent thunderstorms are frequently 
 formed in the great cloud masses of the calm belt. 
 
< 
 
 THE ATMOSPHERE. 
 
 33 
 
 An ill-defined belt of light breezes and occasional calms, 
 known as the horse latitudes or tropical calm belt, lies in 
 each hemisphere between the trades and the prevailing 
 westerlies. Here the weather is generally fair and dry. 
 
 The lower winds blow obliquely away from this belt on 
 both sides, and air must descend from aloft to supply their 
 currents. As the air slowly settles down, it is compressed by 
 the weight of that which rolls in on top of it ; as it is com- 
 pressed, it is warmed ; and as it is warmed, any clouds that it 
 may have contained are dissolved ; hence clear, fair weather 
 is prevalent in this belt. 
 
 Storms of the "Westerly Winds. — The irregular winds 
 by which the prevailing westerlies are so often interrupted 
 sometimes have an in- 
 ward, sometimes an out- 
 ward, spiralling move- 
 we?i^,asinFig.l5. They 
 are like great, slow- 
 turning whirls, 500 to 
 1000 miles in diameter. 
 When blowing outward, 
 the winds are light and 
 the weather is fair. 
 When blowing inward, 
 the weather is cloudy 
 and wet, and the winds may gain a stormy strength, 50 
 to 80 miles an hour on land, and sometimes over 100 
 miles an hour at sea. 
 
 Both classes of whirls travel 500 to 1000 miles a day 
 in an easterly direction, with the general drift of the 
 atmosphere in temperate latitudes. They may strengthen 
 
 Fig. 15. — Spiral Wind Courses. 
 
34 
 
 PHYSICAL GEOGRAPHY. 
 
 and increase in area for a time, then weaken and fade 
 away; their duration being from a few days to two or 
 three weeks, and their distance of travel from 5000 to 
 15,000 miles. 
 
 The great whirls in the westerly winds are well shown 
 on the daily weather maps published by the U. S. Weather 
 Bureau, from which Figs. 26 to 29 are reduced. The direc- 
 tion in which the whirls turn in the northern hemisphere is 
 opposite to that in the southern. 
 
 Fig. 16. — Isotherms for January. 
 
 The pressure of the atmosphere is less tlian usual about 
 the central part of the inward whirls, and greater than usual 
 in the outward whirls. Hence they are often called low- 
 pressure and high-pressure areas. They have also been 
 named cyclonic and anticy clonic areas from the curving 
 movement of their winds. 
 
 The small and very destructive whirling storms, commonly 
 called cyclones in the United States, are better named to7'- 
 nadoes. Their winds probably reach a velocity of 200 miles 
 
THE ATMOSPHERE. 
 
 35 
 
 an hour. Tliey should not be confused with the large, slow- 
 whirling cyclonic areas here ^escribed. 
 
 Change of Seasons. — The earth moves around the sun 
 once a year. For six months in each year (March 20 to 
 September 22, or September 22 to March 20), one hemi- 
 sphere receives a greater amount of sunshine than the 
 other ; it may then be called the summer hemisphere, while 
 the other is called the winter hemisphere. (See Appendix F.) 
 
 Fig. 17. — Isotherms for July. 
 
 During the summer half-year the heat equator moves a 
 moderate distance from the geographic equator into the 
 summer hemisphere, the high temperatures of the torrid 
 zone advance towards middle latitudes, and the ligor of 
 polar cold is lessened. In the Avinter half-year the j)olar 
 cold is extreme, low temperatures advance over the middle 
 latitudes, and the heat on the border of the torrid zone is 
 tempered. 
 
36 PHYSICAL GEOGEAPHY. 
 
 Ill both hemispheres the succession of higher and lower 
 temperatures during the year produces the change of seasons. 
 The winter months in tlie nortliern hemisphere are December, 
 January, and February (these being the summer months of 
 the southern hemisphere) ; the spring months are March, 
 April, and May ; the summer months, June, July, and Au- 
 gust; the autumn or fall months, September, October, and 
 ISTovember. 
 
 The change of temperature with the seasons is much less 
 marked in the torrid zone than nearer the poles. In the 
 temperate zone the summer half-year is the time of plant 
 growth, and is therefore the season of greater activity in all 
 industries immediately, connected with agriculture. 
 
 One of the most interesting consequences of the advance 
 of summer temperatures into higher latitudes is the passage 
 of migratory birds, familiar to every lover of outdoor nature. 
 The approach of winter is accompanied by the return of the 
 birds to warmer latitudes. 
 
 Terrestrial Winds. — The strength of the planetary 
 winds and the boundaries of their belts vary with the 
 seasons, as shown in Fig. 18. Thus modified, the winds 
 may be called terrestrial, as belonging to the earth rather 
 than to j)lanets in general. In the winter heraisphere the 
 difference of temperature between equator and pole is 
 strengthened, and the velocity of the winds is therefore 
 increased. This is especially true of the prevailing west- 
 erlies, where winter is the stormy season. The trade winds 
 show a less distinct seasonal change of strength. 
 
 The tropical calms move toward the equator in winter 
 and toward the pole in summer (ST^ Fig. 18). Any 
 country over which the calms migrate will have the west- 
 erlies and their storms in winter, and the drying trades in 
 summer. 
 
THE ATMOSPHERE. 
 
 37 
 
 This is the case Avith southern California, central Chile, 
 and the Mediterranean countries of southern Europe and 
 northern Africa. These countries are said to have a sub- 
 tropical climate. 
 
 As countries in the subtropical belts are dry in the growing 
 season, agriculture generally requires the aid of irrigation 
 (watering the fields by canals led from streams or reservoirs). 
 The same is true of regions traversed by winds that have just 
 crossed a mountain range, as in the western interior of the 
 United States. 
 
 The calms and rains of the doldrums migrate north and 
 south with the lieat equator. The regions of rainfall thus 
 controlled form the subequatorial belts (SQ, Fig. 18). 
 
 Fig. 18. — Diagrams of Terrestrial Winds for January and July. 
 
 The plains of the Orinoco in Venezuela receive a plentiful 
 rainfall in July and August, but in December and January 
 they are relatively dry. In the wet season cattle find abun- 
 dant pasture on the uplands ; in the dry season they are driven 
 into the valleys. On the plains between the headwaters of 
 the Amazon and Parana, the months of wet and dry seasons 
 are reversed from those of "Venezuela (Figs. 19 and 20). 
 
38 
 
 PHYSICAL GEOGEAPHY. 
 
 The Sudan, between the Sahara and the equatorial for- 
 ests of Africa, is a region of summer rains, with open tree 
 growth or grassy plains. The western Sahara, between the 
 reach of the subtropical (winter) rains on the north and the 
 subequatorial (summer) rains on the south, gives no important 
 river to the Atlantic along a thousand miles of coast line. 
 The rise of the Nile in Egypt from June to September results 
 from the northward advance of the equatorial rains over the 
 upper part of its basin, as in Fig. 20. 
 
 Another remarkable result of the migration of the doldrum 
 
 kr^^"^^^:rv-. 
 
 ■Ov f -e T o =5 ''r^ v"^ \ w 
 
 EST^ERLY WIND 
 
 North! !^r~s T > t r a d \ e / n /n 
 
 ^1 .^ \ Ll/. 
 
 
 O =! f." Y 
 
 "^X-V'/r X>^/iVG- * "r "- 'l'(f - 
 
 Fig. 19. — winds of January. 
 
 belt is seen in the change in the direction of the trade winds 
 when they cross the geographic equator on the way to the 
 heat equator (Figs. 18 to 20). The northeast trade is extended 
 into a northwest wind in the southern summer, the south- 
 east trade into a southwest wind in the northern summer. 
 Thus on both sides of the equator, in the narrow subequatorial 
 belts where this relation appears, the winds alternately blow 
 from opposite directions as the seasons change. Winds of 
 this kind are called monsoons. 
 
 Tropical Hurricanes. — Thunderstorms are of frequent 
 
THE ATMOSPHERE. 
 
 39 
 
 occurrence in the doldrums over the oceans. When the 
 doldrum belt migrates to its furthest distance from the 
 equator, north or south, larger storms with whirling winds, 
 known as hurricanes or tropical cyclones, are occasionally 
 developed, as if from overgrown thunderstorms. 
 
 After being started in the doldrums, hurricanes travel 
 along a curved path near the western border of the ocean, 
 and in a week or two reach the temperate zone, increasing in 
 size, but generally decreasing in violence as they advance. 
 
 Fig. 20. — Winds of July. 
 
 Formerly great destruction was wrought on vessels at sea by 
 these storms ; but now that the season of occurrence (late 
 summer), the usual path, and the behavior of the winds of 
 hurricanes have been learned, and now that vessels are built 
 larger and stronger, losses at sea are much less serious than 
 they were a century ago. 
 
 When hurricane winds blow over islands in the torrid ocean, 
 they may cause much damage to vessels in the harbors by 
 driving them ashore ; and to settlements by destroying their 
 plantations. Cocoanut palms may thus be stripped of their 
 
40 
 
 PHYSICAL GEOGBAPET. 
 
 grgat leaves, after which they require a number of years of 
 growth before again bearing the fruit of which so many 
 uses are made. 
 
 Irregular Development of the Terrestrial Winds. — The 
 irregular arrangement of land and water pi-events the 
 regular development of the terrestrial wind system, and 
 gives rise to certain changes in wind direction over each 
 ocean and continent. 
 
 The heat equator generally stands north of the geographic 
 equator over the Pacific Ocean, especially over its middle and 
 eastern parts. (This is chiefly because more cold water is 
 brought towards the equator by ocean currents from the south 
 than from the north.) During the northern summer a south- 
 west monsoon is imperfectly developed within the northern 
 
 Fig. 21. — Winds of the Atlantic Ocean in January and July. 
 
 subequatorial belt of the Pacific ; during the southern sum- 
 mer a northwest monsoon makes its appearance only in the 
 western part of the southern belt (Fig. 19). 
 
 In the Atlantic also the heat equator is prevailingly north 
 of the geographic equator. (This is for the same reason as 
 
THE ATMOSPHERE. 41 
 
 in the Paci^c.) The southeast trade wind is extended into the 
 northern subequatorial belt during the northern summer ; but 
 the northeast trade wind does not reach the corresponding 
 southern belt during the southern summer. 
 
 The continents lie somewhat across the paths of the 
 terrestrial winds, and interfere with their regular flow. 
 Hence branch winds connect the trades and the wester- 
 lies, and great wind eddies blow more or less distinctly 
 around each ocean basin, especially in the summer hemi- 
 sphere, as in Figs. 19 to 21. 
 
 The North Atlantic wind eddy is so distinct that the Pyr- 
 enees and Atlas mountains are more rainy on their northern 
 than on their southern slopes. On the Pacific West of North 
 and South America the eddying winds blow towards the equa- 
 tor across the subtropical belts. 
 
 Annual Range of Temperature. — The air over the lands 
 is warmer in summer and colder in winter than that over 
 the oceans in the same latitudes. Places in the interior 
 of continents, therefore, have a much stronger change of 
 seasons than those on continental borders or on islands. 
 
 The difference between the average temperatures of the 
 warmest and coldest months is shown in Fig. 22. It is gen- 
 erally less than 10° over the torrid oceans, and less than 20° 
 over most of the temperate oceans. On land the range is 
 stronger. Central Australia and the interior of the Sahara 
 have a range of over 30°. Over most of the United States 
 the range reaches 30° to 60° ; over a belt of land from Hud- 
 son Bay into Alaska the range is more than 80°. Over the 
 greater part of Europe- Asia the range exceeds 40° ; and in 
 northeastern Siberia it exceeds 100°. 
 
 In regions of the greatest range the winters are so cold 
 that the ground is frozen to a depth of 100 feet or more. In 
 
42 
 
 PHYSICAL GEOGRAPHY. 
 
 winter ice is so hard that the runner of a skate does not hold 
 upon it ; wood is too hard to be chopped with the axe. In 
 summer thawing reaches only a few feet below the surface. 
 
 As the air over the continents is alternately warmer and 
 colder than that over the surrounding oceans, the winds 
 
 XINE3 OF 
 
 EQUAL ANKCAL KANGE 
 OF TE31PERATCRE, ^ 
 
 Fig. 22. — Chart of Equal Annual Range of Temperature. 
 
 tend to blow inward towards continental centers in sum- 
 mer, and outward from them in winter. The terrestrial 
 circulation is much complicated by this tendency. 
 
 In winter, when the winds tend outward from land to sea, 
 the far inland regions have much dry and clear weather ; in 
 summer, when winds blow inward, the lands have a greater 
 share of clouds and rain. 
 
 The summer inflow from sea to land strengthens the wind 
 eddies on the western side of the oceans. For example, in 
 July and August a prevailing southerly wind blows from the 
 Gulf of Mexico up the Mississippi valley, increasing the rain- 
 fall of the region that it reaches. In winter the outflow from 
 
THE ATMOSPHERE, 
 
 43 
 
 Fig. 23. — Monsoons of Northern Sanimer. 
 
 the continent tends to counteract the eddy ; at that season 
 the winds of the Mississippi valley are prevailingly from a 
 northern source, and 
 the rainfall is light. 
 
 Southern and 
 eastern Asia ex- 
 hibit these features 
 on a large scale. In 
 summer the winds 
 blow obliquely 
 towards the con- 
 tinent from the 
 Indian and Pacific 
 oceans, giving a heavy rainfall on the more mountainous 
 slopes. In winter the winds blow obliquely outward from 
 the continents, and the lands are then relatively dry. 
 These changing winds are known as the Asiatic monsoons. 
 
 The monsoons of 
 the Indian Ocean are 
 the most remarkable 
 of the world. In 
 the northern sum- 
 mer (Fig. 23) they 
 seem to be a great 
 extension of the 
 southeast trades, 
 turned into a south- 
 west wind after 
 crossing the equa- 
 tor, and becoming somewhat irregular in direction on reaching 
 the lands. In the southern summer (Tig. 24) the northeast 
 trade wind not only occupies its usual belt, but appears to be 
 extended across the equator into the southern hemisphere, 
 
 Fig. 24. — Monsoons of Southern Summer. 
 
44 PHYSICAL GEOGRAPHY. 
 
 where it is turned to a northwest wind. The primitive sailing 
 vessels of the Indian Ocean in earlier centuries, poorly adapted 
 for sailing against the wind, made voyages only as the monr 
 soons favored their courses, — going outward from India to 
 Africa in one half-year, and returning in the next. 
 
 The east coast of the Malay peninsula is beaten by heavy 
 surf under the northeast monsoon, and then the native fisher- 
 men stay ashore. But under the southwest rnonsoon, an off- 
 shore wind, the water is comparatively smooth, and large fleets 
 of fishing boats put out to sea with their palm-leaf sails. 
 
 Winds on Land. — The winds are not so strong or so 
 regular on the uneven lands as on the level seas. In val- 
 leys the winds are much influenced by the direction of the 
 enclosing slopes. Hence observers in a rugged country 
 may often recognize the general direction of the winds 
 better by watching the drift of the clouds than by noting 
 the position of their wind vanes. 
 
 The air over the lands is cooler and heavier than that 
 over the sea at night, but warmer and lighter by day. 
 Hence the wind tends to blow alternately off and on shore 
 on many coasts, such winds being known as land and sea 
 breezes. 
 
 On the coasts in the torrid zone the sea breeze is welcome, 
 as it tempers the excessive heat of the day on land. The 
 same is true of summer weather in the temperate zone. On 
 the coast of Peru the fishermen sail off shore in the morning 
 with the land breeze, and return in the afternoon with the sea 
 breeze. 
 
 Daytime winds. — In fair, warm weather the lower air 
 lying on the land becomes unduly heated by day, as compared 
 to the overlying air. Overturnings are thus produced, and 
 the faster-moving currents from aloft are brought down to 
 
THE ATMOSPHERE, 45 
 
 the surface. Hence on land the winds of daytime are com- 
 monly stronger than those of the night. This is prevailingly 
 the case through the year on torrid lands ; it is characteristic 
 of summer weather in the temperate zone, but is less noticed 
 in winter. At sea no such daily change in the strength of 
 the wind occurs. 
 
 Rainfall. — Rain, snow, hail, and sleet are all included 
 under the general term rainfall. The explanation already 
 given of the winds has shown how closely the amount and 
 season of rainfall are connected with the circulation of the 
 atmosphere. It is largely in this way that the prevailing 
 winds are important in controlling the distribution of 
 vegetation, and thus of population. 
 
 Snow is formed when the moisture of the air is condensed 
 at temperatures below the freezing point (32°). Rain occurs 
 when the moisture of the atmosphere is condensed into drops 
 at temperatures above the freezing point, or when the snow- 
 flakes of lofty clouds descend into the warmer lower atmos- 
 phere, where they melt before reaching the ground. Sleet 
 is half-melted snow. Hail occurs chiefly in summer, when 
 the ascending air currents of lofty thunderstorms carry rain- 
 drops so far upward that they are frozen before they fall. 
 (See Appendix H.) 
 
 The amount of rain is determined by measuring the depth 
 of water that is collected in a vessel having vertical sides, 
 called a rain gauge. Snow should be melted before it is 
 measured. An annual total of 18, 20, or more inches is 
 necessary for agriculture, as over the great prairie region of 
 the Mississippi and Ohio valleys from the 95th meridian 
 eastward. If the annual amount is between 18 and 10 
 inches, agriculture requires irrigation, as on a large part 
 of the Great Plains east of the Rocky mountains, and 
 over large areas in the basins of Utah and Nevada; but 
 
46 
 
 PHYSICAL GEOGRAPHY. 
 
 scattered grass sufficient for cattle ranges may grow in such 
 regions. If the annual total is under 12 or 10 inches, there 
 will not be water enough for irrigation, unless it is supplied 
 by a large river that rises in a moister climate, as in parts 
 of Arizona and southeastern California, 
 
 The distribution of rainfall over the world, represented 
 in Fig. 25, shows that the greater amounts occur in the 
 subequatorial belts, and on mountain slopes ascended by 
 
 Fig. 25. — Chart of Annual Kainfall. 
 
 Dark shading, heavy rainfall (over 100 inches) ; medium shading, moderate rainfall ; 
 light shading and blank, light rainfall (generally under 20 inches). 
 
 the trade winds or the prevailing westerlies. The dry and 
 desert regions of the world are either lowlands of the 
 trade-wind belt, like the Sahara and central Australia, or 
 continental interiors crossed by the westerly winds. The 
 greater part of western Europe and of eastern North 
 America are fortunate in receiving a plentiful but not 
 excessive rainfall. 
 
 The heaviest rainfall in the world occurs on the southern 
 slopes of the Himalaya, north of tlie Bay of Bengal. Here 
 
THE ATMOSPHERE. 47 
 
 the rainfall of a single year would measure 35 or 40 feet 
 in depth, and much more than half of this amount falls 
 during the summer half-year when the southerly monsoon is 
 blowing. On the bold southwest coast of India an annual 
 fall of over 30 feet has been measured. 
 
 In the polar regions the annual snowfall, melted, would 
 seldom exceed 15 inches of water, and would frequently 
 be less than 10. This is because the cooling of cold air does 
 not condense much moisture from it. In the torrid zone the 
 equatorial rains are heavier, because the cooling of warm air 
 produces an -abundant condensation of moisture. 
 
 Dew and Frost. ■ — Dew is a deposit of moisture on the 
 ground, or on loose objects like leaves and sticks lying on 
 the ground. It is formed when the ground becomes cool 
 enough at night to chill the air near it so as to change some 
 of the water vapor that it contains into the liquid form. 
 
 The temperature at which dew begins to be formed is called 
 the dew point. It may be determined by experiment as fol- 
 lows : half fill a tin cup with water whose temperature is 
 about like that of the air. Then slowly pour in ice-water, 
 stirring it with a thermometer. When the outer surface of 
 the cup is clouded by a deposit of moisture, the temperature 
 of the water gives a close indication of the dew point. 
 
 When moisture is condensed upon the ground at tem- 
 peratures below the freezing point, it forms frost. Thus 
 frost on the ground corresponds to snow in the air, and 
 dew corresponds to rain. 
 
 Dew and frost are in part supplied from water vapor in 
 the air that lies near the ground, in part by vapor that rises 
 through the soil from its deeper and moister parts. In the 
 daytime the vapor from the soil escapes into the warm air ; 
 
48 PHYSICAL GEOGRAPHY. 
 
 but at night, when the ground is colder at the surface than 
 beneath, the rising vapor is condensed. Dewdrops found on 
 the blades of grass and on the living leaves of plants close 
 to the ground are in large part supplied by the water that the 
 plants bring up from the ground through the roots. In the 
 daytime the moisture evaporates from the leaves, but at 
 night it may collect upon them in drops. 
 
 Dew and frost are formed more abundantly on clear and 
 calm nights than on cloudy and -windy nights ; for under 
 the latter conditions the ground is not much cooled, while 
 under the former conditions it may cool at night to a tem- 
 perature 30° or 50° below that which it had under noon- 
 day sunshine. 
 
 Weather Changes. — The term weather includes all the 
 atmospheric conditions that an observer may feel or see, — 
 hot or cold, clear or cloudy, dry or wet, windy or calm. 
 
 In the torrid zone the weather is marked by regular 
 changes from day to night ; the changes are small at sea 
 and greater on land, and they are seldom interrupted by 
 storms. In the summer of temperate latitudes the same 
 is largely true, although hot and cold periods give variety 
 to the regular succession of day-and-night changes. In 
 winter the weather of temperate latitudes is largely con- 
 trolled by the passage of cyclonic and anticyclonic areas, 
 which are then numerous and large, and the control by the 
 change from day to night is relatively indistinct. 
 
 In frigid latitudes the change of weather from day to night 
 is always weak compared to the changes caused by the passage 
 of the great atmospheric whirls. 
 
 A comparison of the changes of local weather with the 
 atmospheric conditions shown on the official United States 
 
THE ATMOSPHERE. 49 
 
 weather maps discloses many problems of interest. (See 
 Appendix I.) The summer season of the central and east- 
 ern United States offers many examples of southerly 
 winds, under whose influence the weather becomes warmer 
 day after day, sometimes reaching an oppressive degree of 
 heat. At the same time the day-and-night control is 
 distinct, giving higher temperature, stronger wind, and 
 greater cloudiness under the action of the sun than in 
 darkness. Then, as the distribution of pressure is altered 
 by the eastward drifting of cyclonic and anticyclonic areas, 
 the wind changes to northwest, and the temperature falls 
 for a few days to a moderate degree. 
 
 In winter the irregular weather changes are stronger 
 and more frequent than in summer. They may overcome 
 the regular day-and-night changes. A mild spell of south- 
 erly winds with cloudy weather near a cyclonic center 
 may be quickly followed by a change to northwest winds 
 and clearing weather, accompanied by a rapid fall of tem- 
 perature to a low degree, this fall being known as a cold 
 wave. 
 
 The coldest winter weather usually occurs during 
 periods of light winds or calms, under the influence of 
 the central part of an anticyclonic area. The sky is then 
 very clear, and the ground and the lower air are reduced 
 to extremely low temperatures by cooling through the 
 long quiet night. 
 
 The changes of weather caused by the passage of a suc- 
 cession of high and low pressure areas over the central 
 and eastern part of the United States are illustrated in 
 Figs. 26 to 29 for four successive days. 
 
 At first the central area of low pressure, with rain and 
 
50 
 
 PHYSICAL GEOGRAPHY 
 
 Fig. 26. — Weather Map (first day). 
 
 whirling winds, lies 
 in western Iowa and 
 Missouri, while clear 
 or fair weather pre- 
 vails over the Atlan- 
 tic slope around an 
 area of high pressure 
 with outflowing 
 winds. 
 
 A day later the 
 rainy area has 
 reached the southern 
 Great Lakes ; clouds 
 are spreading east- 
 ward as far as New 
 England, while clear 
 weather with northwest winds is extending from the Great 
 Plains towards the Mississippi. 
 
 On the third day the vsiiny area that at first lay over Iowa 
 has reached the lower 
 Great Lakes and the 
 northeastern states ; 
 a great extent of 
 country in the Mis- 
 sissippi valley and 
 the southern states 
 has clear and fair 
 weather around a 
 center of high pres- 
 sure in western Ten- 
 nessee, while a new 
 area of clouds appears 
 on the western plains. 
 On the fourth day 
 the first cloudy area 
 has nearly disappeared in the northeast, and the second, with 
 
 Fig. 27. —Weather Map (second day). 
 
THE ATMOSPHERE. 
 
 51 
 
 Fig. 28. — Weather Map (third day). 
 
 its central low pres- 
 sure, whirling winds, 
 and rainy area, is ap- 
 proaching the lower 
 Mississippi; the 
 region of clear and 
 fair weather stretches 
 from Minnesota to 
 Florida, with a center 
 of high pressure in 
 North Carolina. 
 
 The succession of 
 weather changes pro- 
 duced at any one 
 place, as Washington 
 or St. Louis, by the 
 eastward passage of these areas of high and low pressure 
 may be inferred from the diagrams. 
 
 Changes of weather in the Mississippi and Ohio valleys 
 are favored by the great extent of open plains from the Gulf 
 of Mexico to the Arctic. The winds of cyclonic and anti- 
 cyclonic areas are 
 thus allowed free pas- 
 sage from regions 
 that, especially in 
 winter, have very dif- 
 ferent temperatures. 
 
 In western Europe 
 weather changes are 
 not so strong or so 
 frequent as in the 
 central and eastern 
 United States, but 
 they are of the same 
 general order. The 
 
 Fig. 29. — Weather Map (fourth day). JiiUrOpean COUl WaVC 
 
52 PHYSICAL GEOGRAPHY. 
 
 does not come from the northwest, where the Atlantic is 
 tempered by the extension of the Gulf Stream, but from the 
 continental area on the northeast. 
 
 Weather predictions, as published by the Weather 
 Bureau, are based on maps like those of the preceding 
 figures, but much larger and more detailed ; observations 
 for the maps are gathered by telegraph from all parts 
 of the country. 
 
 Under such conditions as those of Fig. 29, continued fair 
 weather would be predicted for the Atlantic states, warmer 
 weather with increasing cloudiness and rain for the Ohio 
 valley and southern states, and clearing weather with lower 
 temperature for the southwest. 
 
 Climate. — The general succession of weather changes 
 through the year, averaged for many years, constitutes the 
 climate of a region. The five zones into which the earth 
 is commonly divided need further subdivision in order to 
 correspond to the many well-marked types of climate in 
 different lands and seas. 
 
 The trade-wind belt at sea has the simplest climate in the 
 world, with small daily and yearly changes of temperature. 
 The steady wind and fair weather of almost any day gives a 
 fair example of the year. Lowlands under the regular trade 
 winds suffer greater daily and yearly changes of temperature, 
 with light rainfall. 
 
 ■ The subequatorial belt has distinct seasonal changes, as 
 the clouds and rains of the heat equator move away and give 
 place to the dry trade winds. On or near the geographic 
 equator certain places have two wet and two dry seasons in a 
 year ; for the heat equator crosses them twice, and between 
 its visits they are occupied first by the northeast and then by 
 the southeast trade winds. 
 
THE ATMOSPHERE. 53 
 
 The subtropical belts have a distinct variation of tempera- 
 ture between the warmer and colder parts of the year ; in 
 summer they have the mild and regular climate of the trade 
 winds ; in winter the more irregular and stormy climate of 
 the westerly winds. 
 
 The south temperate zone is mostly an oceanic belt. 
 The changes of . air temperature with the seasons are 
 small, because the water surface warms and cools so little 
 in summer and winter. Its winds are more stormy in 
 winter, less stormy in summer ; never very hot or extremely 
 cold, but for the most part chill, damp, and blustering. 
 Islands near 50° S. are hardly habitable, not that the 
 winters are too severe, although cloudy and wet, but that 
 the summers are too inclement. 
 
 The north temperate zone contains large areas of land 
 and water, and the climates of its various parts are there- 
 fore very unlike. The parallel of 50° N. crosses regions 
 whose climates are so different that they would hardly 
 have been placed under a single zone had they been 
 studied before being named. 
 
 Beginning in the moderate climate of the Korth Atlantic, 
 the parallel of 50° N. enters the favorable climate of middle 
 Europe, where the last thousand years have witnessed the great- 
 est human progress in the arts and sciences that the world 
 has ever known. It crosses the broad deserts of central Asia, 
 where the scattered population is held down in barbarism 
 chiefly by severe and unfavorable climatic conditions. 
 
 The broad North Pacific has a climate as moderate as that 
 of the North Atlantic. Passing the tempered and moist cli- 
 mate of the coast belt of British Columbia, and crossing the 
 snowy mountain ranges beyond, the severe interior climate of 
 middle Canada is reached, with extremes of temperature, sum- 
 
54 PHYSICAL GEOGRAPHY. 
 
 mer and winter, only less than those of inner Asia. As far 
 as habitability is concerned, the middle north temperate zone 
 contains climatic differences almost as great as those found in 
 passing from the equator to the pole. 
 
 Relation of Climate and Vegetation. — The plants that 
 so generally cover the surface of the lands grow by taking 
 food from the air and the soil. Full-grown plants pro- 
 duce seeds, most of which fail for one reason or another 
 to grow ; but the others, germinating at a less or greater 
 distance from their source, give rise to a new generation 
 of plants, which produce seeds in their turn. In this way 
 all kinds of plants might in time be distributed all over 
 the world, if certain barriers did not oppose their progress. 
 
 Young plants growing from heavy seeds, like nuts, slowly 
 spread away from the parent plant. Plants growing from 
 light seeds, especially from such as are carried by the wind, 
 like those of the dandelion, the thistle, and the fireweed, are 
 very rapidly diffused. 
 
 Oceans and mountain ranges are the chief visible bar- 
 riers to the diffusion of plants, but these are not so 
 important as the invisible barriers of climate. Seeds 
 might be carried by winds or birds across an arm of the 
 sea or over a mountain range ; and if the climate is fitting 
 at the end of their journey the seeds would grow and the 
 plants would take possession of the new home offered 
 them. But, however actively seeds are distributed, plants 
 cannot invade a region whose climate is unfit for their 
 growth. 
 
 . Plants like palm trees, that flourish in the torrid zone, 
 spread into lands in higher latitudes on both sides of the 
 equator until they reach regions where the summers are too 
 
THE ATMOSPHERE. 55 
 
 cool for their growth. Plants like corn and wheat, that 
 occupy the temperate zones, are limited to belts on whose 
 polar side the summer is too brief and cool, and on whose 
 equatorial side the summer is too hot for their wider 
 extension. 
 
 Plants that need a plentiful rainfall cannot spread into 
 those regions in which the winds fail to supply rain, even if 
 the temperature is fitting. Thus corn, which grows so luxu- 
 riantly in the Ohio, and middle Mississippi valleys, cannot be 
 raised on the dry western plains without the aid of irrigation. 
 On the other hand, many kinds of thorny cactus plants are 
 found on the dry plains, but they cannot invade the moister 
 regions further east. 
 
 Relation of Climate and Animals. — Land animals, like 
 plants, tend to spread over all parts of the earth to which 
 they have access ; the limits of their distribution are con- 
 trolled partly by climate and partly by food supply, which 
 in turn depends on climate. Like plants, animals are 
 limited on the polar side of their range chiefly by insuffi- 
 cient heat in summer, and on the equatorial side by exces- 
 sive heat in summer. Within the belt thus defined by 
 the values of summer temperatures the distribution of ani- 
 mals is largely controlled by food supply. 
 
 Animals subsist either on animal or vegetable food ; but 
 flesh-eating animals, like the lion, often devour plant-eating 
 animals, like the antelope ; and thus in the end all animals 
 depend for food directly or indirectly on plants, and the dis- 
 tribution of plants has already been shown to depend on 
 climate. 
 
 The study of climate is therefore not only of importance 
 in itself, but also from the control that it exerts over the 
 
56 PHYSICAL GEOGRAPHY. 
 
 distribution of plants and animals, and thus indirectly 
 over the distribution and occupations of mankind. 
 
 Climate and Man. — Those parts of the torrid zone that 
 have a moist climate support a luxuriant plant growth 
 and contain a great variety of animals ; but they are not 
 favorable to the development of the civilized races of 
 man. In dry deserts and in the polar regions it is so 
 difficult to gain a living that human progress is hindered. 
 As a result of the generally small land areas of the south 
 temperate zone the great ocean preserves a uniformly 
 inclement climate, where man finds little opportunity 
 for development. 
 
 In those parts of the spacious north temperate lands, 
 where the climate is neither too dry nor too severe, there 
 is the great advantage of a winter that is cold enough to 
 require the storage of food, and of a summer that is warm 
 enough to provide the food to be stored. There can be 
 little doubt that the habits of industry and thrift here 
 made necessary, but not too difficult, have been of great 
 importance in bringing civilization out of savagery. 
 
CHAPTER IV. 
 THE OCEAN. 
 
 The Exploration op the Ocean. 
 
 Man's conquest of the ocean is one of his greatest 
 triumphs. With wonderful daring and skill he has 
 ventured to trust himself on the perilous waters. Un- 
 dismayed by dangers and losses, he has persevered 
 
 Fig. 30. — An Ocean Steamship. 
 
 through centuries of effort, invention, and discovery, and 
 now he travels almost as safely by sea as by land. He 
 no longer relies upon the wind or oar to propel him, 
 but with metal hull and tireless engines he defies the 
 storms and uses the pathless ocean as a natural high- 
 way in spite of its great perils. To-day the iron steam- 
 
58 PHYSICAL GEOGRAPHY. 
 
 ship, a product of many highly developed arts, crosses the 
 trackless seas so surely and quickly that the people of 
 nations on the opposite sides of an ocean are coming to 
 feel almost like neighbors. The length of a trip between 
 the United States and Europe is so well timed that the 
 date of arrival at its end is almost as regular as the date 
 of sailing at its beginning. 
 
 The thoughtful traveller reflects on the many lines of 
 human progress that have led to the possibility of his voy- 
 age. How little was it imagined when iron was first 
 smelted from its ore, thousands of years ago, that the 
 heavy metal would one day be used to build the safest 
 kind of ships ! When the ancient Greeks watched the 
 movements of the sun and stars, and studied the proper- 
 ties of angles and circles, how little did they realize that 
 from such beginnings the navigator would some day learn 
 to guide himself across the broad seas ! Even as lately as 
 when the steam engine was invented, little more than a 
 century ago, no one supposed that steamships would so 
 generally take the place of sailing vessels as they now do. 
 
 Although a dweller on the lands, man has sailed over 
 nearly all parts of the oceans. The narratives of exploring 
 voyages, like that of Darwin's "Voyage around the World," 
 present many volumes of entertaining and instructive read- 
 ing. The shores of continents and islands have been care- 
 fully surveyed and mapped. Soundings have been taken 
 in the . shallower waters near the lands, to discover any 
 hidden reefs that might endanger passing vessels. Sea 
 captains on voyages in all parts of the world have faith- 
 fully observed the direction and strength of the winds, so 
 that advantage might be taken of them to shorten the 
 
THE OCEAN. 59 
 
 voyages of sailing vessels. The currents of the ocean 
 have been charted, so that they should not drift a vessel 
 unawares out of its course. Tides have been measured at 
 many ports, so that the time of high water may be calcu- 
 lated in advance ; -the master of a vessel may now learn 
 from his tide tables at what hour of any day he will find 
 high water on approaching the shallow entrance of a har- 
 bor. Even the depths of mid-ocean have been measured, 
 and the bottom has been found a safe ground on which 
 to lay submarine cables. As a result of this brave prog- 
 ress, commerce has been greatly developed between distant 
 parts of the world. 
 
 The Physical Features of the Ocean. 
 
 Form of the Ocean. — The ocean is a sheet of salt 
 water, clear and blue, covering about three-quarters of 
 the earth's surface to an average depth of about two miles. 
 It lies in broad depressions between the continental masses, 
 its shallow edges lapping over the land margins. 
 
 A vast water area, comprising the Pacific and Antarctic 
 oceans, covers nearly half the globe. Its surface is broken 
 only by Australia, the Antarctic lands, and many small 
 islands. A short Indian arm extends from this great 
 oceanic area into the space between Africa and Australia ; 
 and a long, relatively narrow Atlantic arm runs between 
 the Old and New Worlds, ending in the gulf-like Arctic 
 Ocean around the North Pole. 
 
 The outline and distribution of the ocean should be studied 
 on a globe. It may then be seen that the surface of a hemi- 
 sphere whose pole is near New Zealand is nearly all water j 
 
60 
 
 PHYSICAL GEOGRAPHY. 
 
 while the opposite hemisphere contains all the large land 
 areas, except Australia, the Antarctic lands, and the extremity 
 of South America. It is not a little curious to note that near 
 the pole of the land hemisphere stands the greatest city of 
 the world, the capital of the empire whose colonies are more 
 widely spread than those of any other nation. 
 
 The Ocean as a Highway. — The lands are widely sepa- 
 rated by the oceans, and navigation of the " high seas " 
 
 ^^jsaj^ssj^^ 
 
 ^-^^^* 
 
 Fig. 31. — Land and Water Hemispheres. 
 
 requires great skill and is fraught with many dangers. 
 But the oceans are a ready-made highway, where move- 
 ment is easy and open to all comers, and the winds furnish 
 free motive power to sailing vessels. Hence transportation 
 in ocean-going vessels is very economical. Before rail- 
 roads were invented, the two sides of the North Atlantic 
 were in more active communication by sea than the two 
 sides of any continent overland. Since railroads have 
 been extensively built, inland transportation has greatly 
 increased; but a great part of international commerce is 
 still carried on across the oceans. 
 
THE OCEAN. 
 
 61 
 
 Exploration of the Ocean. — The earlier exploration of 
 the ocean discovered its continental shore lines and its 
 islands. Exploration in the latter part of the nineteenth 
 century has penetrated its depths and reached its bottom. 
 
 Soundings are now made with much accuracy, even to depths 
 of four miles or more. Fine steel wire is used for a line ; the 
 sinker is a heavy iron ball that is automatically detached 
 
 Fig. 32. — Sounding Instrument and Water 
 Bottle. 
 
 Fig. 33. — Deep-Sea Thermometers. 
 
 on touching the bottom ; then the wire is rapidly reeled in 
 by steam power. A sounding of 3000 fathoms (one fathom 
 equals six feet) can be completed in about an hour. 
 
 The temperature of the deep water is taken by self-regis- 
 tering thermometers. They must be protected by an outer 
 glass tube against the tremendous pressure of the deep water. 
 Samples of water are obtained from various depths by the use 
 of brass tubes, called " water bottles," sent down open, but 
 automatically closed when reeling in begins. 
 
62 
 
 PHYSICAL GEOGRAPHY. 
 
 Specimens of the ocean bottom are gathered by dredges ; 
 
 wire rope is needed to haul up the ton or more of material 
 
 that they take in while dragged on the sea floor at depths 
 
 of one, two, or even three miles. Nets are sometimes attached 
 
 to the rope for the chance of catching 
 
 I animals at different depths. The best 
 
 nets are closed while sinking and rising, 
 
 being opened only while trolling at the 
 
 greatest depth that they reach. 
 
 '1 
 
 T 
 
 Fig. 34. — Dredge. 
 
 Ocean Depths. — Soundings have 
 shown that the ocean basins are com- 
 paratively steep-sided and flat-floored. 
 The greatest depth yet found is 5155 
 fathoms (30,930 feet) in the South 
 Pacific, near the Fiji Islands. Another 
 place of great depth in the Pacific, 
 over 4600 fathoms, lies northeast of 
 Japan. 
 
 The deepest sounding yet made in 
 the Atlantic is 4561 fathoms, in a local depression about 
 100 miles north of Puerto Rico, West Indies. The 
 Atlantic is generally less deep along its middle (1500 
 to 2000 fathoms) than on either side (2500 to 3000 
 fathoms), the shallower middle part being sometimes 
 called a " ridge " or " swell." 
 
 Composition and Density. — The mineral substances dis- 
 solved in ocean water constitute about three per cent of 
 its weight ; their presence makes it heavier than pure water 
 in the proportion of 1.026 to 1.000. Although water is 
 easily moved, it is very little reduced in volume even 
 when compressed by great forces. Hence, in spite of the 
 
THE OCEAN. 63 
 
 great pressure of the upper layers of the ocean on those 
 beneath, the ocean is of nearly uniform density from top 
 to bottom. Anything that is heavy enough to sink at the 
 top will sink all the way to the bottom. 
 
 The ocean contains a great variety of substances in solu- 
 tion, for it has received everything that streams have dis- 
 solved and carried from the lands for ages past. Common 
 salt makes three-quarters of the dissolved substances. An 
 important but much less plentiful dissolved substance is 
 limestone, of which many sea animals make their shells or 
 skeletons. 
 
 A small quantity of atmospheric gases is found dissolved 
 in sea water, even in its deepest parts. It is upon the oxygen 
 thus supplied that fish and most other marine animals depend 
 for " breathing " ; but whales and other mammals living in the 
 ocean come to the surface for air. 
 
 Ocean Temperatures. — ■ The surface layers of the ocean 
 vary in temperature with latitude, reaching about 80° 
 around the equator, and being reduced to 30° or 28° in 
 the polar regions. The great body of the deep ocean is 
 cold in all latitudes ; its temperature is about 30° in high 
 latitudes and 35° or 40° in the torrid zone. 
 
 When exploring vessels dredge in torrid oceans, the sedi- 
 ments brought up from the bottom have a temperature near 
 freezing, strangely in contrast with that of the objects on 
 shipboard under a hot sun. 
 
 The sun's rays have small effect on ocean water at depths 
 below 100 or 150 fathoms. At greater depths the ocean 
 must be nearly dark, with hardly perceptible difference 
 between day and night, or between winter and summer. 
 
64 
 
 PHYSICAL GEOGRAPHY. 
 
 The temperature at any point in the great body of the 
 deep ocean is nearly constant. 
 
 In Fig. 35 depth is measured downward, and temperature 
 horizontally. Curve ABC shows the change of temperature 
 
 with depth in the torrid 
 
 30 (? 
 
 500 
 H 
 
 1000 
 
 1500 
 
 J 
 
 2000; 
 
 TEMPERATURE t^ttttjt • .i . 
 
 40 50 D 60 70 jg^ 80 occans ; DUF, m the tem- 
 
 ^/ ^.iy perate oceans ; and GHJiu 
 
 ^.""^ .--":.'^ the frigid oceans. Below 400 fath- 
 
 / y' 4 oms the curves are all much alike. 
 
 El 
 
 M\ 
 
 F 
 
 The daily and annual range of tempera- 
 ture in the ocean surface is very small, 
 seldom more than 3° and 15°, respectively. 
 As the temperature of the lower air is 
 largely controlled by that of the surface 
 on which it rests, the climate of mid-ocean 
 islands and of continental borders where 
 the prevailing winds blow ashore is free 
 from great changes of temperature between 
 winter and summer. 
 
 Salt water contracts and increases in 
 density down to its freezing point, 28°. 
 Hence the cooled surface water of high 
 latitudes sinks to great depths and creeps 
 very slowly towards the equator ; thus the low tempera- 
 ture of the great body of the ocean is accounted for. 
 
 A movement in the deep waters is also proved by the pres- 
 ence of dissolved oxygen in specimens of water brought up in 
 " water bottles " from great depths. The oxygen is gained 
 from the atmosphere, and as the animals of the deep sea 
 use it in ''breathing," the supply would long ago have been 
 exhausted had it not been renewed. (See Appendix K.) 
 
 Fig. 35. — Curves 
 
 of Ocean 
 
 Temperatures. 
 
THE OCEAN. 
 
 65 
 
 Fresh water is unlike salt water in being densest at 39°. 
 On being warmed or cooled from this temperature it expands 
 and becomes lighter.' Hence in winter, when all the water 
 of a lake has been cooled to 39°, further cooling affects only 
 the surface water, which then soon freezes. 
 
 Ice -in the Ocean. — The ice formed from salt water 
 expands a little as it freezes, and therefore floats. The ice 
 
 rig. 36. — A Vessel teset by Pack Ice. 
 
 thus formed in the polar oceans is known as floe ice; it 
 may reach a thickness of from 3 to 7 feet in a single 
 winter. 
 
 Great fields of floe ice drift with the winds and currents. 
 They may thus be torn apart or crushed together. When 
 two floes collide, pack ice of very irregular surface is formed ; 
 it may reach a thickness of over 100 feet. 
 
 In the return of Greely's expedition to the Arctic regions 
 in 1883, his boats were frequently in danger of being crushed 
 
66 
 
 PHYSICAL GEOGRAPHY. 
 
 when ice fields drifted together, closing the water passage he 
 had been following. 
 
 Smooth floe ice is easily crossed on sleds. The Eskimos 
 make winter journeys upon it. Where packed, it may be im- 
 passable. It was on account of the roughness of ridged pack 
 ice that Nansen had to turn back from his " dash for the pole," 
 in latitude 86° 13' N., longitude 96° E., on April 8, 1895. 
 
 Fig. 37. —An Icetierg. 
 
 When two large fields of pack ice drift together, a vessel 
 between them would be crushed, unless of great strength, 
 and shaped so as to escape by rising. Nansen's vessel, the 
 " Fram," was especially constructed to withstand great pres- 
 sure, and so survived the dangers to which it was exposed. 
 
 Icebergs in the North Atlantic are fragments of glaciers 
 formed on Arctic lands, chiefly Greenland; they are of 
 fresh water. The tabular icebergs of the Antarctic Ocean 
 are fragments of a heavy sheet of ice that is believed, to 
 rest upon land or upon a shallow ocean bottom around the 
 
THE OCEAN. 67 
 
 south pole. Some of these ice blocks measure a mile or 
 more on a side, and 1200 to 1500 feet in thickness. The 
 height of icebergs above the sea is about one-sixth or one- 
 seventh of their depth below the surface. 
 
 Collision with an iceberg is one of the dreaded dangers of 
 navigation in high latitudes. In the southern oceans drifting 
 icebergs reach latitude 60°, or. even 40°. In the North Atlan- 
 tic they reach latitude 45° southeast of Newfoundland, but 
 they are absent from the northwestern coast of Europe even in 
 latitude 70°, on account of the warm water there prevailing. 
 They are wanting in the North Pacific, except in the bays of 
 the Alaskan coast. 
 
 The Ocean Bottom, — '■ The greater part of the deep ocean 
 bottom is a comparatively even plain of soft ooze ^ of simi- 
 lar composition and form over great areas. The plain rises 
 and falls gently in broad swells, but is not varied by hills 
 and valleys of uneven form. Its smoothness is due to the 
 slow but long-continued gain of material chiefly from the 
 surface and in small part from the margins. 
 
 No mountain ranges with sharp peaks and ridges separated 
 by deep passes and valleys have yet Iseen discovered on the 
 open ocean floor far from the continents. But Cuba and some 
 of the neighboring islands in the West Indies seem to be the 
 crests of a mountain range, whose western extension forms 
 submarine ridges in the northern Caribbean, dividing it into 
 a number of deep basins, and connecting the islands with 
 Central America.- 
 
 Volcanic and coral islands are the most abrupt forms of the 
 deep ocean. Volcanic cones sometimes rise above the ocean 
 surface, forming lofty mountains, as in the Hawaiian Islands ; 
 sometimes they are known only by soundings. 
 
 1 rine-textured deep-sea deposits of animal origin are called ooze ; if 
 derived from the wash of the lands, they are called muds. 
 
68 PHYSICAL GEOGRAPHY. 
 
 The calcareous (limy) ooze which covers a large part of 
 the ocean floor consists of the minnte shells, more or less 
 decayed, of simple animal forms that live at or near the sur-, 
 face. One of these, highly magnified, is shown in Fig. 38. 
 In greater depths than 3000 fathoms the ooze is commonly 
 replaced by a reddish clay, which is believed to be a very 
 
 Fig. 38. — Globigerina (magnified 100 times). 
 
 slowly accumulating deposit of insoluble substances that 
 remain after the calcareous material of the minute shells is 
 dissolved in the deep-sea water. 
 
 *' The monotony, dreariness, and desolation of the deeper 
 parts of this submarine scenery can scarcely be realized. The 
 most barren terrestrial districts must seem diversified when 
 compared with the vast expanse of ooze which covers the 
 deeper parts of the ocean," 
 
THE OCEAN. 
 
 69 
 
 Mediterraneans. — .Besides the open oceans thus far con- 
 sidered, there are several deep seas, more or less separated 
 from the oceans by land barriers. The most important of 
 these is the classic Mediterranean (the sea " in the middle 
 of the lands "), averaging nearly as deep as the great 
 oceans, but connected with the Atlantic only by the 
 narrow and shallow strait of Gibraltar. 
 
 Other similar mediterranean seas are the Caribbean and 
 the Mexican (deep central part of the Gulf of Mexico). 
 The former has many inlets from the Atlantic between 
 the various islands of its eastern rim ; it is divided into 
 
 CARIBBEAN SEA 
 
 70-80^ 
 
 ATLANTIC OCEAN 
 
 70-80° 
 
 Fig. 39. — Temperatures of the Caribtean Sea. 
 
 several deep compartments by ranges of the West Indian 
 submarine mountain range. The latter is a single basin. 
 
 Several mediterraneans of moderate size are found east of 
 Asia. The Japan, China, Sulu, Banda, and Celebes seas are 
 the most important ; they are imperfectly enclosed from the 
 Pacific by island chains. 
 
 The deep water of mediterraneans is warmer than that of 
 the adjacent oceans, as shown in Fig. 35, KLM. The tem- 
 perature of the Caribbean Sea is 39^° at great depths, as in 
 Fig. 39, this being the temperature of the adjacent Atlantic at 
 the depth from which the water in the Caribbean is supplied ; 
 for the deepest connecting channel, east of Puerto Eico, has a 
 temperature of 39-g-° at its bottom, 900 fathoms. The deep 
 Atlantic is several degrees colder. 
 
 The Mediterranean has a constant temperature of 55° from 
 a depth of about 250 fathoms to the bottom (over 2000 
 
70 
 
 PHYSICAL GEOGEAPHY. 
 
 fathoms), this being somewhat colder than the adjacent 
 Atlantic at the depth of the shallow entrance near the strait 
 of Gibraltar.^ In winter the northern Mediterranean is of 
 uniform temperature from toj) to bottom ; hence it is believed 
 that this sea repeats the condition of the oceans in accumu- 
 lating in its greatest depths the coldest water that is supplied 
 at the surface. 
 
 Continental Shelves. — The ocean often overlaps the 
 borders of the continental masses in a comparatively shal- 
 low belt of water, at whose outer edge the depth is com- 
 
 Continent 
 
 ts Shallow Water on 
 
 <<? Continental Shelf 
 
 Deep Water 
 
 Fig. 40. — Section of Continental Shelf. 
 
 monly about 100 fathoms ; thence it rapidly sinks to the 
 deep ocean floor. These shallow bottoms are known as 
 continental shelves. The water on the shelf is often 
 greenish from fine suspended sediment, unlike the clear 
 deep blue water of the open ocean and the yellowish water 
 opposite the mouths of great rivers, such as the Amazon 
 and the Hoangho. 
 
 The gravel, sand, and clay washed from the lands are 
 more or less moved about by waves, currents, and tides on 
 the continental shelves. Thus they are slowly ground 
 finer and finer, and their finest particles are gradually 
 moved outward to deeper water. They are seldom found 
 
 1 The water in tlie strait is over 400 fathoms deep ; a less depth is 
 found a short distance westward. 
 
TSE OCEAN. ■ 71 
 
 in dredgings over 200 miles from shore ; for the most part 
 they are carried a less distance. In the course of ages the 
 sediments thus accumulating may form successive layers 
 or strata hundreds of feet thick, including many shells and 
 other relics of marine life. 
 
 The lowland borders of continents are often built of layers 
 of sand and clay frequently containing marine fossils ; thus 
 suggesting that a former sea bottom has there been raised to 
 a land surface. 
 
 A well-defined continental shelf, from 50 to 100 or more 
 miles in width, stretches along the eastern side of North 
 America from JSTewfoundland to Florida, and thence around 
 the Gulf of Mexico. The British Isles stand upon a conti- 
 nental shelf that borders mid-western Europe. The Malayan 
 and Australian islands surmount broad shelves between Asia 
 and Australia, separated by a belt of deeper water. 
 
 Continental shelves are of great importance as the chief 
 fishing grounds of the world. The European ports around 
 the. North Sea send out hundreds of fishing vessels to its 
 shallow waters. The rich fishing grounds of the New- 
 foundland Banks attracted many fishermen from the Old 
 World over three centuries ago. 
 
 Waves. - — When the wind blows over the sea, the water 
 gains an undulating motion, forming waves that advance 
 with the movement of the wind. Although the wave form 
 moves forward, the water only oscillates up and down, 
 back and forth, without progressive motion. The stronger 
 the wind, the higher the crests and the lower the troughs 
 of the waves ; and the greater their length or distance from 
 crest to crest, the deeper their disturbance extends beneath 
 the surface, and the faster their progressive motion. 
 
72 
 
 PHYSICAL GEOGRAPHY. 
 
 Great waves formed in the open ocean by gales and 
 hurricanes are often called seas. Their height from 
 trough to crest reaches 30 or 40, but seldom exceeds 50 
 feet. Their length varies from 300 to 1500 feet or 
 more, and their velocity from 20 to 60 miles an hour. 
 The interval between the passage of successive crests, or 
 the period of the wave, is seldom more than 10 seconds. 
 
 Fig. 41. — Orbital Movement of Water in Waves. 
 
 The water particles in waves move forward in the crest 
 (Fig. 41), downward on the back, backward in the trough, 
 and upward in the front of the next wave. Hence each 
 particle moves around a curved path every time that a 
 wave passes by ; the movement of the wave being con- 
 stantly in one direction, wliile the water particles rise and 
 fall, advance and retreat, at a much less speed. 
 
 The waving of a field of grain under the wind may be taken 
 as an illustration to show the relation of the curved-path 
 movement of the particles to the forward progress of the 
 
THE OCEAN. 73 
 
 waves. The independence of wave and water movement may 
 be seen on a river surface when the wind is blowing up stream"; 
 or at the mouth of a harbor when the wind is blowing on shore 
 while the tide is running out. 
 
 It is fortunate that only the shape of great waves has a 
 rapid forward movement, while the water oscillates at a mod- 
 erate rate. If the water moved forward with the waves, ves- 
 sels would be swept thousands of miles from their courses and 
 thrown violently on the shores ; the ocean would not be 
 navigable. 
 
 In the construction of ocean steamers and war vessels 
 it is important that the period in which they naturally 
 roll (like the period of a swinging pendulum) shall be 
 longer than that of any waves they are likely to meet; 
 for if the two periods agreed, the repeated action of the 
 waves might make the vessel roll more and more until it 
 capsized. 
 
 A small quantity of oil poured on the sea spreads 
 rapidly and reduces the violence of the waves in a storm. 
 A gale ordinarily forms ripples and small waves on the 
 backs of greater waves, and causes the crests of great seas 
 to curl over, so that they would break with destructive 
 strength on the deck of a vessel. At such a time a film 
 of oil decreases the catch of the wind on the water and 
 prevents the large waves from curling and breaking. 
 
 Many accounts of the use of oil in storms have been pub- 
 lished by the United States Hydrographic Office, Washing- 
 ton. They show that, when a vessel is headed towards the 
 wind (" hove to ") and heavy seas come on board over the 
 bow, a little oil allowed to drip from a bag will spread even 
 towards the wind, forming a smooth surface or <' slick"; and 
 the waves entering the slick will decrease in height and cease 
 breaking over the deck. 
 
74 PHYSICAL GEOGRAPHY. 
 
 When a vessel is running with, the wind, iieavy seas some- 
 times come aboard over the stern ; but if a little oil is allowed 
 to drip overboard, the slick spreads out like a fan across the 
 wake, and the great seas are roimded off as they run into it, 
 so that the vessel rides them without difficulty. 
 
 Great waves, travelling 20 to 60 miles an hour, soon 
 run out of the storm that forms them and swing far 
 across the ocean, preserving their length and velocity, but 
 diminishing in height. In this reduced form a wave is 
 called a swell. 
 
 In calm weather the ocean surface may be smooth and 
 glassy, but not absolutely level and quiet ; for it is never free 
 from the slow heaving and sinking of fading swells from 
 distant storms. A vessel becalmed in the doldrums always 
 swings idly to and fro as the swell rolls by. 
 
 When the swell runs into shoaling water near land, its 
 velocity decreases ; its crest rises, and its trough sinks, 
 thus making its height greater ; the front becomes steeper 
 than the back ; and on reaching a sloping shore the crest 
 curls forward and dashes upon the beach, forming surf or 
 breakers. 
 
 The surf is like a mill in which rocks, gravel, and sand on 
 the shore are ground finer and finer. During storms surf 
 exerts an enormous force capable of moving blocks of rock 
 10 or more feet in diameter. 
 
 Exposed coasts may be beaten by a heavy surf while 
 the neighboring sea is unruffled by the wind. The surf 
 is then derived from a broad swell, which comes from the 
 great waves of a storm that may be 1000 or more miles 
 away. 
 
THE OCEAN. 
 
 75 
 
 The great hurricane -of Sept. 3-12, 1889, while on its way 
 from the West Indies to the Carolina coast, produced a 
 destructive surf on the coast of ISTew Jersey while the storm 
 area was still a thousand miles distant. At St. Helena, a 
 lonesome island in the South Atlantic, boats from vessels at 
 anchor in the harbor frequently cannot reach the shore in 
 
 Fig. 42. — Surf. 
 
 fair weather on account of the " rollers," or heavy surf, on the 
 beach. The swell that produces this surf is believed to come 
 from storms in temperate latitudes of the North Atlantic. 
 
 Earthquake Waves. — When an earthquake, caused by 
 some disturbance in the earth's crust, occurs beneath the 
 sea, the whole body of the ocean above it is moved 
 slightly, -and the movement then spreads away on all 
 sides in long, low waves that travel with great speed. 
 When nearing the shore, the speed and length of the 
 
76 PHYSICAL GEOGEAPRY. 
 
 wave are decreased, but the height is greatly increased. 
 The wave may then rush far in on a lowland coast, caus- 
 ing great destruction. 
 
 The tremendous explosive eruption on the volcanic island 
 Krakatoa, between Java and Sumatra, in August, 1883, pro- 
 duced waves that spread far around the world. Their aver- 
 age velocity of progression was nearly 400 miles an hour. 
 On distant coasts their rise and fall was slight ; but on coasts 
 near Krakatoa the waves rushed upon the land with a height 
 of from 50 to 80 feet, flooding the lowlands, sweeping away 
 many villages, and drowning thousands of the inhabitants. 
 A large vessel was carried a mile and a half inland and 
 stranded 30 feet above sea level. 
 
 An earthquake in the North Pacific produced a destructive 
 wave, 10 to 50 or more feet high, on the coast of northern 
 Japan in the evening of June 15, 1896. The coast was laid 
 waste for 175 miles. The few persons who saw the wave and 
 survived it reported that the sea first drew back about a 
 quarter of a mile, and then came rushing in like a black wall, 
 gleaming with phosphorescent light and overwhelming the 
 shore. On the open coast the sea became quiet in a few 
 minutes after the wave broke ; but in bays the water surged 
 and swirled for half an hour. The outline of the shore was 
 changed in many places ; many villages were destroyed, and 
 thousands of acres of arable land were laid waste. Thousands 
 of fishing boats were crushed or carried away ; 27,000 persons 
 lost their lives, and 60,000 survivors were left homeless. 
 
 It is thought that earthquake waves are sometimes pro- 
 duced, by great masses of fine sediments sliding down the 
 slopes of continental shelves. In Japan many earthquakes 
 are ascribed to this cause. Telegraph cables lying on such 
 slopes are especially subject to injury ; when raised for re- 
 pairs, they are found torn, as if violently dragged with the 
 slidinar sediments. 
 
THE OCEAN. 
 
 77 
 
 Ocean Currents. — The upper waters of the ocean, to a 
 depth of 50 or 100 fathoms, move slowly in the general 
 direction of the prevalent winds, thus forming currents 
 that circulate about the great oceanic areas. The outline 
 diagram of ocean currents (Fig. 43) shows that each of 
 
 Fij. 43. — Chaxt of Ocean Currents. 
 
 the great oceans possesses a great eddy-like current that 
 moves slowly around it, leaving the central waters rela- 
 tively quiet. 
 
 If an observer stood in the center of an oceanic eddy in 
 the northern hemisphere, the currents would pass around him 
 from left to right ; in the southern hemisphere, from right to 
 left. 
 
 The eddying currents are the chief natural basis for sub- 
 dividing the great oceanic area into the six oceans ; the North 
 and South Pacific, the North and South Atlantic, and the 
 Indian oceans, each has its own great eddy ; while the 
 Antarctic Ocean has a great eddy around the south pole, 
 joining the eddies of the three southern oceans. The Arctic 
 also has a current about the pole, joining that of the North 
 
78 
 
 PHYSICAL GEOGRAPHY. 
 
 Atlantic, somewhat like the two loops of a figure 8 ; but the 
 Arctic should be classified as a large sea or gulf, rather than 
 as an ocean. 
 
 A current that advances slowly in a broad and shallow 
 sheet at a rate of 10 or 15 miles a day, like that which 
 
 crosses the middle North 
 Atlantic, shouldbe called 
 a drift. A current that 
 flows rapidly in a com- 
 paratively narrow pas- 
 sage, with a velocity of 
 50 or more miles a day, 
 like that issuing from 
 the Gulf of Mexico 
 strait of Florida, should be called a stream. 
 
 Fig. 44. 
 
 - Displacement of a Vessel by 
 Currents. 
 
 ^Wi^ 
 
 through th€ 
 
 It is important that the masters of vessels should be ac- 
 quainted with the movements of ocean currents. In cloudy 
 and foggy weather, 
 when observations of 
 the sun cannot be 
 made to determine lati- 
 tude and longitude, a 
 vessel might be drifted 
 out of its expected 
 course if no allowance 
 were made for the 
 movement o*f the 
 waters. Thus if, in- 
 tending to follow the 
 course MahcN (Fig. 
 44), a vessel were 
 drifted to the course 
 MABCB, it would pass dangerously near the headlands at B 
 
 Fig. 45. — Drift of floating Objects by 
 Currents. 
 
THE OCEAN. 79 
 
 and C, and might even run ashore. Wrecks on the southwest 
 coast of Ireland have not infrequently been due to this cause. 
 
 The drift of abandoned wrecks, whose positions are noted 
 by passing vessels, gives indications of the movements of cur- 
 rents. The angular lines in Fig. 45 show the drift of several 
 wrecks. The broken lines indicate the drift of many logs 
 from a great timber raft that was abandoned in a storm while 
 on the w-ay from the Canadian Provinces to New York, Decem- 
 ber, 1887. 
 
 Thousands of bottles have been thrown into the sea, with 
 record of the time and place where they have been set adrift, 
 and request that the finder shall report the time and place of 
 their discovery, afloat or ashore. The dotted lines of Fig. 45 
 give a few inferred " bottle tracks." 
 
 In Hansen's famous attempt to reach the north pole he 
 sailed eastward along the northern coast of Asia and turned 
 northward into a region of ice fields, where his vessel was 
 caught between two floes. He then drifted with the ice, 
 expecting that the Arctic current would carry him past the 
 pole towards Greenland. Had he gone further east before 
 turning north, a closer approach to the pole might have been 
 made. 
 
 The remarkable correspondence between the course of 
 the oceanic eddies (Fig. 43) and the course of the prevail- 
 ing winds over the oceans, as shown in the charts, Figs. 
 19 and 20, points to the winds as the cause of the cur- 
 rents. Like the circulation of the atmosphere, the eddy- 
 ing of the upper waters of the oceans must be regarded as 
 a characteristic habit of a globe having large oceans, a 
 mobile atmosphere, and a warm equatorial zone. 
 
 The belief that the winds cause the currents is confirmed 
 by the way in which the surface drift of the waters may be 
 for a time brushed to one side of its usual course, or even 
 reversed, during a storm. 
 
80 
 
 PHYSICAL GEOGRAPHY. 
 
 Fig. 46. 
 
 ■ Currents of the Indian Ocean 
 in July. 
 
 The currents of the Indian Ocean, with its gulfs on the 
 north of the equator, show an extraordinary variation in 
 
 direction, following the 
 change in the blowing of 
 the monsoons. During 
 the northern summer, 
 when the southwest mon- 
 soon is developed north 
 of the equator (Fig. 23), 
 the waters under it have 
 a general eastward mo- 
 tion, as in Fig. 46. Dur- 
 ing the southern summer, 
 when the northwest mon- 
 soon is developed south 
 of the equator (Fig. 24), 
 the waters under it also 
 move eastward, while on 
 the north of the equator the currents run in a general westerly 
 direction under the north- 
 east monsoon of that re- 
 gion, as in Fig. 47. 
 
 East-flowing currents of 
 this kind near the equator 
 are called counter cur- 
 rents, because they move 
 in a direction opposite to 
 that of the equatorial 
 members of the great 
 eddies. 
 
 The several parts of 
 the various eddies may 
 receive special names. 
 Those parts which run 
 westward, near and about parallel to the equator, are called 
 
 Fig. 47. — Currents of the Indian Ocean 
 ' in January. 
 
TRE OCEAN. 81 
 
 the equatorial currents. The eastern part of the South 
 Pacific eddy is called the Humboldt, or Peruvian, current; 
 it brings a great body of cool water from far southern lati- 
 tudes, and keeps the temperature about the Galapagos 
 Islands (west of Peru) so low that coral reefs, such as 
 abound in the equatorial Pacific further west, are not 
 found on their shores. 
 
 The name Gulf Stream, in the Atlantic, should be 
 properly limited to the narrow, deep, and rapid current 
 issuing from the Gulf of Mexico, where its velocity reaches 
 80 or 90 miles a day; but it is popularly extended far 
 northeast over the broad, shallow, and slow-moving drift 
 on the northern side of the North Atlantic eddy, and even 
 along its branch, past Norway. This extension of the 
 current is not a stream at all, and it includes much water 
 that passed outside of the West Indies and not through 
 the Gulf of Mexico. 
 
 Sailing vessels should take advantage of winds and cur- 
 rents in shaping their courses. If bound from the United 
 States to far South American ports, they should cross the 
 equator well to the eastward, so as to avoid being carried 
 backward by a strong current past the Guiana coast, where 
 the winds may fail in the doldrums. A ship sailing from an 
 Atlantic port to Australia should round Cape of Good Hope 
 and take advantage of favorable winds and currents in the 
 southern Indian Ocean about latitude 50°. On the homeward 
 voyage favoring winds and currents would be found in the 
 same latitude of the South Pacific, towards Cape Horn. 
 
 Currents and Temperatures. — Certain ocean currents 
 carry warm water poleward; others carry cold water 
 equatorward, thus causing an irregular arrangement of 
 sea-surface temperatures. The eddying winds over the 
 
82 
 
 PHYSICAL GEOGBAPHT. 
 
 several oceans and the bordering continents cause similar 
 irregularities in atmospheric temperatures. In a general 
 way the eddying of the waters and winds narrows the 
 warm belts on the eastern side of the torrid oceans, and 
 widens the temperate belts on the eastern side of the 
 oceans in middle latitudes. 
 
 The effect of currents and winds in disturbing the even 
 arrangement of temperatures is much less distinct in the 
 southern hemisphere, where only one continent extends over 
 50° from the equator, than in the northern hemisphere, where 
 the continents almost enclose the polar sides of the oceans. 
 The eastern drift of the far southern surface waters (forming 
 the Antarctic circum polar eddy) is little interrupted, and 
 the temperature belts follow close along the parallels of 
 latitude. 
 
 The temperature belts of the North Atlantic are more 
 disarranged than those of any other ocean. This is because 
 of the shape of its shores. It gains 
 a large branch current from the 
 South Atlantic, thus giving it an 
 undue amount of warm water in the 
 neighborhood of the West Indies; 
 a great branch of its eastward drift 
 turns northeast, past the British 
 Isles and Norway; and a cold cur- 
 rent, returning from the Arctic 
 regions, flows past Labrador and 
 Newfoundland. The belt of tem- 
 perate climate (Fig. 48) is broadly 
 spread over the western coast of 
 the Old World between latitudes 30° and 60°. The same 
 
 Fig. 48. 
 
 Temperatures on the 
 Atlantic. 
 
THE OCEAN. 
 
 83 
 
 climatic belt is compressed between latitudes 30° and 45° 
 on the eastern coast of North America. 
 
 Florida and Nova Scotia differ as much in mean annual 
 temperature as Morocco and Norway. Labrador is a bleak, 
 desolate region very thinly inhabited, while England, in the 
 same latitude on the opposite side of the Atlantic, has a mild 
 climate and a dense population. The chilling northeast wind 
 of New England is part of a cyclonic whirl, supplied by air 
 that has been lying over the cold Labrador current. 
 
 Tides. — Regular movements of the ocean, rising and 
 falling on the shores twice in a little more than a day, 
 are called tides. In the open ocean tides are not per- 
 ceived ; in many bays the tidal change of level, or range, 
 
 
 Fig. 49. — High Tide, 
 
 reaches 10, 20, or more feet. The change of level is 
 accompanied by currents — flood tide running in from the 
 open ocean, ebb tide running out again. A brief period 
 of quiet or slack water occurs when flood changes to ebb, 
 or ebb to flood. 
 
84 
 
 PHYSICAL GEOGRAPHY. 
 
 Fig. 50. — Low Tide. 
 
 The following table and diagram (Fig. 51) give the time 
 of high and low water and the direction and velocity of flood 
 and ebb currents for several stations in a large bay, which lead 
 to a number of important conclusions. 
 
 The interval or period between the times of successive high 
 tides is constant at all stations, being 12 hours 26 minutes. 
 
 The range of the tide increases from the entrance towards 
 the head of the bay, and then diminishes up the tidal river or 
 estuary further inland. 
 
 The rise and fall are of equal duration at outlying stations, 
 low tide occurring at mid-interval between high tides ; but 
 near the head of the bay the rise is more rapid than the fall, 
 
 Sta- 
 tion. 
 
 2 S 
 
 Rise. 
 
 Cur- 
 rent. 
 
 
 O H 
 
 Fall. 
 
 Cur- 
 rent. 
 
 
 li 
 
 Rise. 
 
 
 li.m. 
 
 
 
 h.m. 
 
 h.m. 
 
 
 
 h.m. 
 
 h.m. 
 
 
 A 
 
 0.05 
 
 2 ft. 
 
 Im. 
 
 3.10 
 
 6.20 
 
 2 ft. 
 
 Im. 
 
 9.25 
 
 12.30 
 
 2 ft. 
 
 B 
 
 2.10 
 
 3 
 
 2 
 
 5.15 
 
 8.25 
 
 3 
 
 2 
 
 11.25 
 
 14.35 
 
 3 
 
 C 
 
 2.55 
 
 3 
 
 2 
 
 6.10 
 
 9.10 
 
 3 
 
 2 
 
 12.20 
 
 15.20 
 
 3 
 
 D 
 
 4.25 
 
 4 
 
 2 
 
 8.05 
 
 11.50 
 
 4 
 
 2 
 
 14.20 
 
 16.50 
 
 4 
 
 E 
 
 8.30 
 
 5 
 
 3 
 
 12.35 
 
 16.40 
 
 5 
 
 3 
 
 18.50 
 
 20.55 
 
 5 
 
 F 
 
 15.05 
 
 6 
 
 3 
 
 19.30 
 
 0.00 
 
 6 
 
 3 
 
 1.45 
 
 3.30 
 
 6 
 
 G 
 
 22.20 
 
 6 
 
 3 
 
 3.10 
 
 7.55 
 
 6 
 
 3 
 
 9.20 
 
 10.45 
 
 6 
 
 J 
 
 4.00 
 
 4 
 
 2 
 
 8.20 
 
 12.45 
 
 4 
 
 2 
 
 14.35 
 
 16.25 
 
 4 
 
THE OCEAN. 
 
 85 
 
 and low tide occurs nearer the following than the preceding 
 high tide. 
 
 Dotted lines are drawn in Pig. 51 to indicate the inferred 
 position of high tide in the bay at the even hours. The 
 advance of high tide is then seen to be about 50 miles an hour 
 in the deeper water off-shore, but only 10 miles or less in the 
 shallow water near the bay head. 
 
 The flood and ebb currents run past the outlying stations 
 (A, B) for some time before and after high water. At the 
 head of a little bay, like L, slack water occurs at high and 
 low tide ; flood currents run while the tide rises, and ebb 
 currents while it falls. 
 
 Fig. 51. 
 
 - Diagram showing FrogTessioii of High 
 Tide up a Bay. 
 
 When high water occurs in the entrance to the bay, the 
 high waters of two preceding tides are near the head of the 
 bay, as shown in section in Fig. 52. Many actual examples 
 illustrating these phenomena may be found in the Charts and 
 the Tide Tables published by the U. S. Coast Survey. 
 
 Birjh 
 
 Bioh 
 
 D 
 
 c 
 
 B 
 
 A nigh 
 
 ^si. si^ 
 
 \^f5/^tacfc Mean siaclc'-^ 
 Ebb 
 
 ^ Loio 
 
 
 
 -" Slack 
 
 
 
 'Ebb 
 
 
 
 Fig. 52. — Diagram of Tide Waves. 
 
86 PHYSICAL GEOGRAPHY. 
 
 It appears from the foregoing that tides resemble waves 
 in many ways. High tide is the crest of the long, flat 
 tidal wave ; low tide is the trough. Tidal currents cor- 
 respond to the curved-path movements of water in ordinary 
 waves. The change in the range, velocity, and form of 
 the tide, as it advances up a bay, may be compared to the 
 change in the behavior of the ocean swell as it runs ashore. 
 
 Cause of the Tides. — The regular arrival of wave-like 
 tides on all ocean shores leads to the belief that the whole 
 ocean must be undulating. The tide waves in the open 
 ocean must have a less range and a greater velocity than 
 the tide waves near shore ; but the period must everywhere 
 be 12 hours 26 minutes. The undulation of the oceans 
 must be caused by some disturbing force that acts in the 
 same period as that of the tides. 
 
 The apparent daily movement of the moon carries it 
 from one side of the earth to an opposite position in 12 
 hours 26 minutes ; and this fact suggests that the moon is 
 the cause of the tides. The power of the moon to produce 
 the tides can be reasonably explained as a result of the 
 attraction that it exerts on the earth and the oceans. 
 
 It was known to the ancient inhabitants of Great Britain 
 in the time of Julius Csesar, almost 2000 years ago, that 
 there was some relation between the moon and the tides ; but 
 Newton, the great English mathematician and astronomer, 
 first gave about two centuries ago a clear explanation of 
 the process by which the moon can produce tides. (See 
 Appendix J.) 
 
 Tides are beneficial in maintaining a circulation in bays 
 and harbors where the waters might otherwise be almost 
 
THE OCEAN. 
 
 87 
 
 stagnant. At high water a harbor will admit vessels of a 
 larger size than could enter if the ocean level did not 
 change ; but at low water the harbor may be inaccessible 
 except to much smaller vessels. 
 
 In funnel-shaped bays or estuaries the tidal range becomes 
 large, and flood and ebb currents are very strong, making 
 navigation difficult or even dangerous. The tidal range 
 
 Fig. 53. — The Tidal Wave or Bore in the Seine. 
 
 sometimes exceeds 50 feet at the head of the Bay of Fuudy 
 and of the Bristol channel ; here the flood current rushes in 
 like foaming surf. The estuary of the Seine in France has 
 a similar surf-like tide, shown in Fig. 53. Such surf-like 
 tides are called bores. 
 
 Many curious tidal phenomena are found on shore lines of 
 different forms. At New York a high tide entering from the 
 harbor reaches the rocky narrows of Hell Gate when a low 
 tide arrives through Long Island sound; and six hours later 
 a low tide from the harbor meets a high tide from the sound. 
 Thus a rapid current is caused to flow back and forth in the 
 narrow passage, which was dangerous to vessels until the 
 channel was widened by blasting away its reefs. A current 
 of this kind is sometimes called a tidal race. 
 
88 PHYSICAL GEOGRAPHY. 
 
 Faint tides are observable in large lakes. In Lake Michi- 
 gan at Chicago, and in Lake Superior at Duluth, the strongest 
 tides have a range of about three inches, but they are usually 
 marked by an irregular rise and fall of the water due to 
 on-shore and off-shore winds. 
 
 Life in the Ocean. — The surface layers of the open 
 ocean possess a considerable variety of animal life, from 
 
 large mammals like 
 whales to minute or- 
 ganisms (Fig. 38) whose 
 tiny shells are so plenti- 
 fully strewn over the 
 ocean floor. The former 
 occur in moderate num- 
 bers; the latter are 
 countless. The distri- 
 bution of surface life is 
 determined chiefly by 
 differences of tempera- 
 ture from the torrid to 
 the frigid zones. Those 
 forms which swim or are 
 drifted freely by the 
 currents are found over 
 vast areas. 
 
 In fair weather the surface waters are sometimes alive with 
 minute, jelly-like forms. In the warmer seas the phosphores- 
 cent light which these simple organisms produce wheu dis- 
 turbed, as in rippling waves or in the wake of a vessel, makes 
 the water glow at night. 
 
 The relatively quiet water about the central part of the 
 great surface eddies generally contains a considerable quan- 
 
 Fig. 54. — A Floating Jellsrfish. 
 
THE OCEAN. 
 
 89 
 
 tity of. floating seaweed, or sargassuvi ; hence these central 
 areas are called sargasso seas. The sargasstcm is believed to 
 be derived from shallow marginal waters, where it grows on 
 
 Fig. 55. — Deep-Sea Fish, x J. 
 
 the bottom. A great variety of small animals live on the 
 floating weed, and a certain kind of fish uses it as a " nest " 
 for its eggs. 
 
 The deep ocean floors have no plants. They are in- 
 habited by a considerable variety of animals, such as fish, 
 crabs, shellfish, starfish, etc. ; but the forms of life are here 
 much less varied and less numerous 
 than in the shallower waters near the 
 shore. 
 
 The animals of the deep sea live under 
 enormous pressure, even several tons to 
 a square inch. But just as land animals 
 have air within their bodies, and thus 
 withstand the pressure of the atmosphere, 
 so sea animals are permeated by fluids, 
 and thus unconsciously support the heavy 
 pressure of the ocean. 
 
 While many deep-sea animals are 
 blind, it is curious that some have well- 
 developed eyes, and are ornamented by 
 colors in elaborate patterns. Hence there 
 must be some light in the ocean abysses. It may be sup- 
 plied by phosphorescent animals, of which there are many 
 kinds in the deep sea. 
 
 Fig. 56. —Deep-Sea 
 Crustacean. X }. 
 
90 
 
 PHYSICAL GEOGRAPHT. 
 
 
 The intermediate depths of the ocean, between the upper 
 part and the bottom, are prevailingly without life — a great 
 desert space, cold, quiet, and mono- 
 tonous. 
 
 The shallow waters of the ocean 
 
 margin teem with plants and animals. 
 
 Many animals, such as sponges, 
 
 5,-j corals, and barnacles, are fixed to the 
 
 bottom ; they need not move about in 
 
 t-«.<=^4^'W seaich for food, because the moving waters 
 
 j'fJ/Ti bring it to them. Nearly all the plants of 
 
 ■■^f^ the sea are of a comparatively simple kind, 
 
 If^i^Mfj without flowers or seeds. The shallow waters 
 
 aie the fishing grounds of the sea, and furnish 
 
 impoitant supplies of food to the neighboring 
 
 lands. 
 
 The animals of the shallow sea margins ex- 
 hibit gi eater variety from place to place than is 
 found among those of the open surface or of the 
 deep floor. A notable peculiarity of the shallow 
 waters in the polar regions is an abundance of 
 seaweeds similar to those of low latitudes ; while 
 the plants that grow on Arctic lands, chiefly mosses and 
 lichens, are very unlike the land plants of warmer latitudes. 
 
CHAPTER V. 
 THE LANDS. 
 
 The Changes of the Lands. 
 
 The form of the lands varies greatly from place to place. 
 Here we find endless variety, in contrast with the wonder- 
 ful uniformity prevailing in the oceans. As a result of 
 this variety, thg conditions of life are very different for 
 people on broad plains far inland, in deep valleys among 
 lofty mountains, near haTbors of the seacoast, or on lonely 
 islands in mid-ocean. The people of a savage tribe, living 
 in any one of these homes and knowing little or nothing 
 of the rest of the world, might contentedly remain ignorant 
 of the way in which the forms of the land around them 
 were produced. The people of a civilized nation, learn- 
 ing much about all parts of the world from explorers and 
 travellers, and perceiving that the way in which the people 
 of different nations live is largely controlled by their geo- 
 graphical surroundings, naturally inquire about the origin 
 of highlands and lowlands, of mountains and valleys. 
 
 During the nineteenth century, land forms have been 
 studied attentively and much has been learned about their 
 origin. The most important general result of this study 
 is that the forms of the land as we now see them are found 
 to be the effect of slow changes continued for thousands 
 and thousands of years. It is at first difficult to realize 
 that the crust of the earth, seemingly so solid, neverthe- 
 
92 PHYSICAL GEOGRAPHY. 
 
 less slowly rises or falls, now revealing the bottom of a 
 shallow ocean border as a land surface, now submerging a 
 low continental border beneath the sea; but there can be 
 no question that such movements have repeatedly taken 
 place, and that they are even now in slow progress. It is 
 hard to believe that deep valleys have been worn between 
 high mountain ridges by nothing more than the long- 
 A3ontinued action of rills and streams such as are still at 
 work ; but the attentive observer must notice that active 
 streams wear their channels, and receive the waste of the 
 land that is washed from the enclosing valley slopes ; and 
 great results must follow from these processes if they are 
 long continued. The more the world is studied, the more 
 certain it becomes that changes of these kinds are ordinary, 
 not extraordinary, events in the history of the earth. 
 
 The time required for all these changes can hardly be 
 calculated ; it must be vast beyond comprehension. All 
 the centuries of human history are only long enough to 
 discover small changes in land forms. The lowlands that 
 guided the migrations of the early races of men across the 
 continents, and the mountains that stood in their way, are 
 lowlands and mountains still; yet in the history of the 
 earth lowlands have over and over again been slowly up- 
 lifted to mountain height, and mountains have repeatedly 
 been very slowly worn down to lowlands. Such changes in 
 the expression of the face of the earth must have required 
 periods of many million years, compared to which man's 
 life on the earth is but a brief interval. But only when 
 the forms of the land are recognized as the result of long 
 changes can the lands be properly understood as the home 
 of man. 
 
the lands. 93 
 
 Physical Features of the Lands. 
 
 Area of the Lands. — The globular earth is uneven 
 enough to raise somewhat more than a quarter of its sur- 
 face slightly above the oceans in broad land areas, called 
 continents. The continents, covered only by the atmos- 
 phere, present many contrasts to the deep sea floors cov- 
 ered by the oceans; and these contrasts have for long 
 ages been of the greatest importance in determining the 
 geographical conditions of animal and vegetable life on 
 the globe, as they have in recent ages determined the 
 geographical conditions of man. 
 
 The area of the globe is about 197,000,000 square miles. 
 The lands occupy somewhat more than 50,000,000 square 
 miles ; their total area remains uncertain until the polar regions 
 are fully explored. Six-sevenths of the, land area are in the 
 land hemisphere, where the ocean occupies little more than 
 half the surface. The lands in the water hemisphere occupy 
 only about one-fifteenth of the surface. 
 
 The greatest islands are near the continents, as in the 
 archipelago north of North America, the West Indies, New- 
 foundland, the British Isles, and the Malayan-Australasian 
 archipelago. Most of these islands stand upon continental 
 shelves, and are separated from the continents only by shal- 
 low water. The numerous oceanic islands, distant from con- 
 tinents, are of small "total area (about 40,000 square miles). 
 
 The five continents differ greatly in size, arrangement 
 of parts, and degree of separation. It is not possible in 
 the present state of knowledge to give a precise definition 
 of a continent, other than to say that it is a large area of 
 land. 
 
94 
 
 PHYSICAL GEOGRAPHY. 
 
 Asia and Europe form a single continent, often called 
 Eurasia ; but on account of their great extent, and still more 
 because of their great differences with regard to human his- 
 tory, it is convenient to regard each of them as a "grand 
 division " of land. 
 
 Height of the Lands. — The highest mountain peaks, 
 25,000 to 29,000 feet, do not rise above sea level so much 
 as the greatest ocean depths sink below it, and the aver- 
 age elevation of the lands (2400 feet =735 meters) is 
 much less than the average depth of the oceans. 
 
 METERS 
 ;,000 
 
 4,000 
 
 4,000 
 
 Fig. 58. — Height of Land and Depth of the Sea. 
 
 Fig. 58 exhibits the share of high and low land, and of 
 deep and shallow ocean, the whole area of the earth being 
 measured by the breadth of the figure. It is thus seen that 
 most of the land surface is but little above sea level, while most 
 of the sea floor lies deep below the sea surface. 
 
 30,0UU • 
 
 
 
 r 
 
 20,000 ■ 
 
 
 
 
 10,000 • 
 
 
 
 
 
 LAND 
 
 
 SEA LEVEL 
 
 
 10,000 
 
 \ 
 
 OCEAN 
 
 20,000 
 30,000 - 
 
 
 
 ^^ "^^^ 
 
 Continental Outline. — Africa and South America are 
 similar in having simple outlines, with few large bays, 
 peninsulas, and outlying islands. North America and 
 
TSE LANDS. 95 
 
 Eurasia are alike in having irregular outlines, with many 
 large bays and peninsulas, and with numerous outlying 
 islands. Europe is rich in arms of the sea entering far 
 into the land, like the North, Baltic, and Adriatic seas. 
 
 Continents are generally broader in the north than in the 
 south. This is distinctly seen in South America, North Amer- 
 ica, and Africa. Land arms are more frequently directed 
 southward than northward, as in Florida and Lower Califor- 
 nia, and in many peninsulas from Spain to Farther India. 
 
 The grouping of the continents is very irregular and follows 
 no known law. The lands occupy an irregular belt stretching 
 from Cape Horn to Cape of Good Hope, broad across the mid- 
 dle of the continents, narrow at their ends, broken at Bering 
 Strait, and with a half-submerged arm reaching out to Australia. 
 
 The earth as a whole, being of globular form, may be 
 treated as a body of regular shape, its different parts from 
 equator to poles being marked off by a simple system of paral- 
 lels and meridians. The atmosphere, covering the entire earth, 
 may be for the most part treated in belts, the members of the 
 wind system and other climatic features being arranged nearly 
 parallel to the equator, but made somewhat irregular by the 
 interference of the continents. 
 
 The ocean, covering the greater part of the earth, exhibits 
 a well-marked system of surface movements that are roughly 
 symmetrical on both sides of the equator. The lands are so 
 irregularly distributed and so uneven in surface that no simple 
 description can be given of their outline or their form. 
 
 Changes of Continental Outline. — The form of the lands 
 and the outline of their shores seem at first sight to be 
 unchangeable. But the more the world is studied, the 
 more certain it becomes that slow changes are going on in 
 the shape of the earth's crust, and that the outline of the 
 continents is subject to change as the continental masses 
 
96 PHYSICAL GJEOGRAPHT. 
 
 very slowly rise or sink. Thus in the course of long ages 
 the geography of the world may be greatly altered. 
 
 Slight movements of elevation or depression, such as have 
 often happened in the earth's long history, may slowly drown 
 a lowland on a continental border, or gradually reveal a part 
 of a continental shelf as a plain bordering higher land. 
 These movements are so slow that they are hardly percep- 
 tible in the course of a century ; but when continued for 
 hundreds of centuries they cause changes of great importance 
 in the geography of the lands. 
 
 It has been discovered that a large part of North America 
 had a land existence at an early stage in the earth's history, 
 uncounted millions of years ago, and that it was afterwards 
 submerged ; for wide-spread rock layers formed of bedded 
 sediments and containing fossils of sea animals are found 
 overlying and burying an ancient land surface with hills and 
 valleys. In still later times the continent has suffered many 
 small changes of altitude, sometimes sinking so that a sea of 
 moderate depth overspread its borders, sometimes rising again 
 so that the land extended beyond the present shore line, but 
 in a general way retaining its ancient outline. 
 
 The same may be said of a considerable part of Eurasia, 
 and of certain parts of other continents. Hence it is coming 
 to be believed that, on the whole, continents are elevations in 
 the earth's crust that have for long ages stood higher than 
 the deep ocean floors. 
 
 Changes in continental outline are so slow that they 
 have seldom been detected by direct observation ; but this 
 is chiefly because delicate observations of shore lines have 
 been made only within the last century or two. 
 
 If the ancients had been as attentive to geographical as to 
 astronomical problems, it can hardly be doubted that many 
 
THE LANDS. 97 
 
 distinct changes in the level of the land and in the position of 
 shore lines would have been found between the time of ancient 
 G-reece and to-day. 
 
 Observations in the last hundred years or more give reason 
 to believe that the coasts of Massachusetts and New Jersey 
 are now sinking (one or two feet a century), and that much 
 of the_ coast of Sweden is rising (maximum, three feet a cen- 
 tury). The coast of the Netherlands is sinking a foot a 
 century, and its fields near the shore, 15 to 20 feet below the 
 sea level, are diked to keep the water off. - Many geographical 
 proofs of change of level will be given in later pages. 
 
 The globular form and regular rotation of the earth as 
 a whole seem to be permanent features of our planet. The 
 belt-like arrangement of the winds seems to be as enduring 
 as the shining of the sun. The eddying of the oceans 
 must be affected by the outline of the continents ; yet as 
 long as the sun shines, the earth rotates, and the winds 
 blow, the eddies must turn regularly to the right or left, 
 according to their hemisphere. But the outline of the 
 lands is subject to many changes that seem to be without 
 system. 
 
 There will always be doldrums around the equator, and 
 westerly winds in temperate latitudes. There will always be 
 a current entering the torrid zone on the eastern side of the 
 oceans. But in other ages Asia and Europe may have been 
 or may come to be separated by the submergence of the plains 
 from the Black Sea to the Arctic; and Asia and Australia 
 may be united by the elevation of the sea floor between them. 
 Hence, although the continents seem to be the most perma- 
 nent features of the earth's surface, they may be long outlived 
 by the systematic movements of the ocean currents and the 
 winds. 
 
98 PHYSICAL GEOGBAPRY. 
 
 Variety of Land Surface. — The surface of the continents 
 possesses great variety of form and composition, in strong 
 contrast to the monotony of the broad sea floors. Rocks 
 and soils, as well as mountains, valleys, and plains, differ 
 from place to place. Peaks and ridges of resistant rocks, 
 slopes and valleys underlaid with weak rocks and covered 
 with soils of gravel, sand, and clay ; these and many other 
 differences give great variety to the lands. 
 
 Mountain ranges are characteristic of the continents 
 rather than of the sea floors, where plains of vast extent 
 prevail. But mountain ranges occasionally rise from the 
 sea bottom, showing their crests above the surface, as in 
 the West Indies. Submerged ranges may yet be discov- 
 ered by soundings among the island groups of the Pacific. 
 
 The continental shelves overlapped by some of the oceans 
 have something of the variety of the lands from which they 
 receive washings of gravel, sand, and clay. Volcanoes and 
 their lavas are among the few features possessed in common 
 by the deep sea and the dry lands. 
 
 Climate of the Lands. — The conditions of the land sur- 
 face vary greatly under different conditions of weather and 
 climate. Heavy rains are followed by clear sky; strong 
 winds by light winds or calms. A bare desert surface in 
 the torrid zone may be heated at noon above 150°, and 
 may cool nearly to freezing the next night. In the frigid 
 zone the frozen soil may thaw and warm at the surface 
 during summer, but it will be intensely frozen again, even 
 to 80° below zero, the next winter. 
 
 Variations of temperature, so distinct at the land surface, 
 rapidly decrease under ground. Af; a depth of 4 or 5 feet 
 
THE LANDS. 99 
 
 daily changes are hardly perceptible ; at a depth of 20 or 30 
 feet there is but little variation from the mean temperature 
 of the year (about 80° in the torrid zone, near zero in far 
 northern lands). 
 
 In northeastern Siberia, where the ground is frozen to a 
 depth of 300 to 500 feet, grass and bushes grow when the soil 
 thaws for a few feet in summer ; but large trees are wanting. 
 The mammoth, an animal resembling a hairy elephant, but no 
 longer found living, has sometimes been preserved in the frozen 
 beds of sand and gravel that border some of the Siberian 
 rivers, where it was buried at the time of river floods centuries 
 ago. 
 
 On descending beneath the land surface, as in deep mines, 
 the crust of the earth is found to be about 1° warmer 
 for every 60 feet of descent ; but this rate varies in differ- 
 ent regions. Hot springs, geysers, and volcanoes all indicate 
 the occurrence of high temperatures deep under ground ; 
 hence it is believed that the great body of the earth beneath 
 its cool outer part or crust is glowing hot, and less rigid than 
 if it were cold. In spite of the great store of heat within, 
 the temperature of the surface is hardly affected by that of the 
 interior, but depends almost wholly on sunshine. 
 
 Activities of the Lands. — In nothing do the continents 
 differ more strikingly from the sea floors than in the activ- 
 ity of the various processes that go on upon the lands, and 
 in the rapidity of the changes that the processes produce. 
 The surface rocks split apart when water freezes in their 
 crevices, or they rust under the chemical action of air and 
 water. A sheet of loosened rock waste is thus formed 
 over most of the land surface. The various processes by 
 which rock waste is produced are known under the gen- 
 eral term weathering. Weathering varies greatly under 
 different climates and with different rocks. 
 
100 
 
 PHYSICAL GEOGRAPHY. 
 
 In the dry, mild, and equable climate of Egypt, ancient 
 statues have been but slightly weathered in several thousand 
 years. A great stone monument, 60 feet high, known as Cleo- 
 patra's Needle, brought from Egypt to New York in. 1880, was 
 so much affected by the weather in a single winter that it was 
 necessary to coat its surface with a preservative substance. 
 
 In Egypt it had stood 
 over 3000 years with 
 little change. 
 
 Under the heavy 
 rainfall and luxuriant 
 vegetation of the equa- 
 torial forests, weather- 
 ing advances with com- 
 parative rapidity ; it is 
 aided by the products 
 of decomposing vege- 
 table matter. On ex- 
 posed mountain peaks 
 and in high latitudes, 
 where the temperature 
 frequently rises or falls 
 past the freezing point, frost is active in splitting rock masses 
 to smaller and smaller fragments. 
 
 Although acting slowly, weathering accomplishes great 
 results in the long course of the earth's history. The occur- 
 rence of soil, in which the roots of so many useful plants 
 grow, and the form of the land surface, which constantly 
 exerts so great an influence on the manner of man's living, 
 are both due in large part to the work of the slow but 
 persevering attack of the atmosphere on the rocks of the 
 lands. 
 
 Every rock ledge or quarry offers opportunity for observing 
 this widespread process. The weathering of the older grave- 
 
 Fig. 59. — A Quarry showing Weathered Kock. 
 
THE LANDS. 
 
 101 
 
 Fig. 60. — Granite. 
 
 stones in cemeteries may frequently be noticed. In cities the 
 different amounts of weathering on old and new stone build- 
 ings, or in buildings of different kinds of stone, serve to illus- 
 trate in a simple way the 
 changes that occur on a 
 much greater scale all over 
 the lands. 
 
 Varieties of Rocks. — 
 
 The rocks of the earth's 
 crust are of many differ- 
 ent kinds, and vary 
 greatly in their resistance 
 to weathering. Granite, 
 consisting of crystalline 
 grains of several min- 
 erals (quartz, feldspar, 
 and mica) closely bound together, is one of the more 
 resistant rocks ; but the weathering of one of its minerals 
 (feldspar) unbinds its parts, and it slowly crumbles to a 
 gravelly soil. 
 
 Quartz is easily recognized by its glassy lustre and its hard- 
 ness. It will strike fire with steel, and was employed for this 
 purpose before matches were invented. Feldspar is not quite 
 so hard; its color is usually gray or pink, and it splits with 
 a smoother face than quartz. Mica has the property of split- 
 ting into very thin elastic scales. 
 
 Sandstone, composed chiefly of grains of quartz, is resist- 
 ant when the grains are well cemented together, but weak 
 when they are imperfectly cemented. 
 
 Sandstone is formed from the waste of such rocks as gran- 
 ite. The sand is washed into the sea or other body of water. 
 
102 
 
 PHYSICAL GEOGRAPHY. 
 
 Fig. 61. —Pebbly Sandstone. 
 
 and is there spread out in layers which may in the course of 
 
 ages accumulate to great thickness. Infiltering waters, carry- 
 ing some mineral 
 substance in solu- 
 tion, deposit it be- 
 tween the grains and 
 bind them more or 
 less perfectly to- 
 gether. Pebbles are 
 often found in sand- 
 stones, giving them 
 a coarse texture. 
 
 The finer waste 
 from such rocks as 
 granite forms muddy 
 deposits when it set- 
 tles in quiet water. 
 The grains are here 
 
 much smaller than those of sandstone, and the rocks thus 
 
 formed, known as shale and slate, are generally of small or 
 
 moderate resistance. 
 
 Shaly sandstone is a rock 
 
 intermediate between a 
 
 fine shale and a granular 
 
 sandstone. 
 
 Limestone is gener- 
 ally formed of the re- 
 mains of the shells or 
 skeletons of sea ani- 
 mals, more or less 
 broken to fragments or 
 even ground to powder 
 in the waves of shallow waters. It often includes shells 
 and corals as fossils, as in Fig, 62. It is not so resistant 
 
 Fig. 62. — Limestone with Fossil Shells. 
 
THE LANDS. 103 
 
 to the weather as granites or dense sandstones, and is 
 much more soluble in water than other rocks. 
 
 Some limestones are formed of the fine ooze that accumu- 
 lates on the ocean bottom from the shells of minute animals 
 like the globigerina (Fig. 38) that float near the surface when 
 living. Limestone of this kind is called chalk. 
 
 There are manj'- kinds of lavas that have been pushed 
 out from the hot interior of the earth through the colder 
 crust. Basalt, a dark and dense lava, is one of the most 
 resistant rocks of this kind. 
 
 When lavas are blown with explosive violence from vol- 
 canoes, they are shattered to fragments. Deposits formed of 
 such fragments may be much less resistant to weathering than 
 heavy sheets of dense lava that, after flowing quietly from a 
 volcano, solidify as they cool. 
 
 The Wasting of the Lands. — Surface water, supplied 
 by rain or melting snow, washes the finer rock waste down 
 the slope of the land to the valley floors or to the streams, 
 and the streams bear the waste along their channels, thus 
 sweeping it from one place and spreading it over another, 
 or washing it to the sea. Where streams run, they rasp 
 their channels with the rock grains that they bear along, 
 and valleys are thus slowly worn in the surface of the 
 land. The higher the land, the deeper the valleys may 
 be cut. 
 
 Large valleys, receiving many smaller branching valleys 
 and ravines that dissect the surface of the land and lead 
 streams from higher to lower ground, are among the most 
 characteristic features of the continents. They are the result 
 of stream action, and cannot occur on the deep sea floor. 
 
104 PHYSICAL GEOGRAPHY. 
 
 They are sometimes found beneath sea level, extending for- 
 ward from the present coast line across the shallow conti- 
 nental shelf ; they are then taken as proof of the depression 
 of that part of the continent. 
 
 The winds act with great effect on bare surfaces, sweep- 
 ing finer rock waste into drifts (dunes), and raising the 
 dust aloft to settle far away. Waves, currents, and tides 
 wear the edge of the land and the shallow continental 
 margins, cutting cliffs and building sand reefs along the 
 shores. 
 
 The wet-weather streams of roadsides and the waves on 
 the shores of ponds or reservoirs exhibit in a small way the 
 processes characteristic of large rivers and oceans. The dif- 
 ferent effects of winds on dusty roads, on grassy fields, or on 
 forested surfaces, illustrate the contrast that prevails between 
 wind action in dry and in moist regions. 
 
 The sea floor is enduringly quiet and silent. The tides of 
 the deep sea are very faint. The creeping of cold polar water 
 towards the equator must be almost imperceptible. Chemical 
 changes of the bottom deposits are slight. The gain of the 
 bottom by the steady shower of organic remains from the sur- 
 face must be very feeble, and the change of form by this gain 
 must be exceedingly slow. 
 
 Although the changes produced in the form of the lands 
 by weathering and washing are slow, they have been so 
 long continued that marvellous results have, been pro- 
 duced. Not only are the lands dissected where deep 
 valleys have been worn in plateaus and mountains, but 
 whole mountain ranges have been worn down to lowlands. 
 The forms of the land to-day can be appreciated only 
 when it is seen that they are the present stage of a long 
 series of changes. The description and explanation of 
 
THE LANDS. 105 
 
 land forms thus considered is the object of the greater 
 part of this book. 
 
 The general wasting of a land surface is slow, but local 
 changes are easily noted by the attentive observer. Roads are 
 gullied by wet-weather streams. Much soil may be washed 
 from a plowed hillside in a single rainstorm. Landslides pro- 
 duce striking changes on mountain slopes and in the valleys 
 below. Cataracts like Niagara wear back their cliffs even more 
 than a foot a year. Deltas grow forward into lakes and seas 
 so as to gain perceptibly in a century. Ostia, once the port of 
 ancient Rome, is now over a mile inland from the advancing 
 front of the Tiber delta. Sea cliffs may be cut back by the 
 waves ; the exposed eastern bluff of Cape Cod, Mass., is 
 retreating at an average rate of three feet a year. 
 
 The general process of wasting and washing, by which the 
 surface structures are slowly worn away and the deeper and 
 deeper structures of the earth's crust are attacked, is called 
 denudation, or erosion. Its rate varies greatly with rock struc- 
 ture, slope, and climate. The lower Mississippi carries enough 
 land waste to. lower its whole basin an inch in about three 
 centuries. An inch in from one to ten centuries may be taken 
 as a rough value of denudation averaged for large areas. 
 
 Opportunity for Varied Forms of Life. — The land sur- 
 face, unless too cold, too dry, or too bare of rock waste 
 (soil), is well covered with vegetation, the larger part of 
 which consists of flowering plants, much more highly 
 organized than the plants of the sea. 
 
 Land plants gain their food from the soil through their 
 roots, and from the atmosphere through their leaves, and thus 
 utilize the rock waste and the air with which the rock crust of 
 the land is covered. Sea plants make little use of the deposits 
 gained by the sea margin, and take their food chiefly from 
 minerals and gases dissolved in sea. water. 
 
106 PHYSICAL GEOGRAPHY. 
 
 Land animals are numerous, varied, and as a whole 
 highly organized. They exceed the animals of the deep 
 sea floor in variety of structure and habit. They are 
 exceeded in number only by the animals of the shallow 
 sea margins or of the open sea surface. 
 
 Many animals of the sea are attached to the bottom, like 
 corals ; others move slowly, like starfish and shellfish ; still 
 others float with the drifting waters, having little movement 
 of their own, like jellyfish. Only the more highly organized, 
 like many fish, swim rapidly. But nearly all land animals 
 move about actively, walking, running, or flying. 
 
 The larger and more important land animals (mammals 
 and birds) are warm-blooded. The only warm-blooded ani- 
 mals of the sea (whales, porpoises, etc.) are believed to be 
 the descendants of remote land ancestors, gradually modified 
 for marine life, but retaining many resemblances to the forms 
 from which they are derived. 
 
 The rock waste of the land has come to be the dwelling- 
 place of certain forms of land life, such as earthworms, many 
 kinds of insects, and certain mammals, like the moles. Many 
 animals, such as ants, many kinds of bees and wasps, prairie 
 dogs, foxes, etc., burrow in the finer waste. Other animals, 
 such as snakes, find shelter in the hollows between coarse 
 fragments of rock waste. 
 
 Apparently owing to the greater mobility of air than of 
 water, many land animals have developed organs for the pro- 
 duction of sound, the most remarkable sounds being the songs 
 of birds and the speech of man. The animals of the sea are, 
 with hardly an exception, silent. 
 
 Floating and swimming sea animals are of about the same 
 weight as the water that they displace. Birds and insects are 
 much heavier than the air in which they fly ; and flying must 
 be regarded as indicating a much higher development than 
 swimming, . . 
 
THE LANDS. 
 
 107 
 
 The higher development and the much greater intelli- 
 gence of many land animals than of sea animals should 
 be regarded as a result of the greater variety of physical 
 conditions found on the lands than in the seas. 
 
 The class of insects, almost limited to the lands, furnishes 
 many examples of extraordinary instinct, as with bees and 
 ants. Nest building by birds, house building by beavers, 
 " homing " of pigeons, 
 and trailing (by scent) 
 of dogs, are examples 
 of highly developed in- 
 stincts that have no 
 parallel among the in- 
 habitants of the sea. 
 
 The physical condi- 
 tions of the deep sea are 
 more varied than those 
 of the lands only in 
 
 respect to the variations of pressure. Land animals are sub- 
 ject at sea level to an atmospheric pressure of about a ton to 
 the square foot of surface. This pressure decreases with 
 altitude, but few animals climb or fly high enough to reduce 
 it by half. In the sea the pressure is increased a ton per 
 square foot by descending a little more than 30 feet; and 
 many sea animals have a vertical range of much greater 
 measure. 
 
 Distribution of Life. — The distribution of plants and 
 animals can be explained only when it is understood that 
 the members of every living species are descended from a 
 long line of ancestors. Related species, such as the vari- 
 ous antelopes or the hawks, are believed to have sprung 
 from a single species ; their existing differences are due 
 to gradual variations by which they have become better 
 
 Fig. 63.— Beavera. 
 
108 
 
 PHYSICAL GEOGRAPHY. 
 
 Fig. 64. — Caribou. 
 
 adapted to their slowly changing surroundings through 
 
 long ages of the earth's history. 
 
 Among the many changes of surroundings none have 
 
 been more important than variations in the outline and 
 
 form of the lands such as may 
 have been caused by the slow 
 raising or wearing down of 
 mountain ranges, or by the 
 slow elevation or depression of 
 a continental border. Conti- 
 nents, once connected, may have 
 been divided by the depression 
 and submergence of the lower 
 lands; the descendants of a 
 common stock would then be 
 separated into two families. 
 
 The longer the time since such a separation, the more the 
 
 descendants of one family may vary from those of the other. 
 For example, the reindeer of northern Europe and the 
 
 caribou of far northern Amer- 
 ica are so much alike that a 
 
 recent connection of the lands 
 
 on which they are found must 
 
 be inferred. Again, the puma 
 
 and jaguar of middle latitudes 
 
 in the New World are cat-like 
 
 animals, and resemble the lion, 
 
 tiger, and leopard of similar 
 
 latitudes in the Old World in 
 
 so many ways that naturalists have been led to believe they 
 
 must be descended from the same stock. Hence in some 
 
 '^^Jw. 
 
 Fig. 65. — Jaguar. 
 
THE LANDS. 
 
 109 
 
 rig. 66.— Tiger. 
 
 former time the Old and New Worlds must have been 
 connected in latitudes where the ancestors of these ani- 
 mals could pass from one 
 region to the other. But 
 the American forms are 
 now so unlike the others 
 that a long time must have 
 elapsed since the continents 
 were separated. 
 
 Life on Islands. — Islands that rise from continental 
 shelves are occupied by many plants and animals similar 
 to those of the neighboring main- 
 land. It is inferred from this that 
 the continental mass once stood 
 higher, and that the continental 
 shelf was then a lowland on which 
 the present islands rose as hills or 
 mountains. 
 
 Various species of cassowaries 
 (ostrich-like birds) are found in 
 Australia and the islands to the 
 north, each land area having its own 
 species. Erom this it is argued that 
 the common ancestors of all these 
 species occupied the region when the 
 continental mass stood higher and 
 the mainlands and islands were connected by the lowland of 
 the present continental shelf. Since then the region has 
 been depressed, the lowland flooded by the sea, and the islands 
 separated from Australia and from each other. The differences 
 between the various species of cassowaries must have arisen 
 since they were separated by the drowning of the lowlands. 
 
 Fig. 67. — CaBSOwary. 
 
110 
 
 PHYSICAL GEOGRAPHY. 
 
 Australia, the most isolated continental region of the east- 
 ern hemisphere, has no true mammals but is the chief home 
 of marsupials (pouched mammals), like the kangaroo, once 
 widespread over the world, as is shown by their fossils in rock 
 layers, but now hardly surviving elsewhere. ISTew Guinea and 
 several other islands north of Australia, separated from the 
 mainland by a shallow sea, are also occupied by similar mar- 
 supials, thus confirming 
 the recent connection of 
 these lands as indicated 
 by the cassowaries. Asia 
 has no marsupials, but 
 many large mammals. 
 The neighboring islands 
 on the southeast, rising 
 from a broad continental 
 shelf, possess many sim- 
 ilar mammals; hence 
 here also the islands must 
 have been recently con- 
 nected with the continent. 
 But the Asian and Australian regions must have been long 
 divided, as their animals are very unlike ; the division must 
 have followed the deep-water line between Celebes and aSTew 
 Guinea, known as '' Wallace's line," from its discoverer. 
 
 An island is so distinctly separated from the rest of the 
 lands, that the Latin word for island (insula) gives us the 
 words "insulate" and "isolate," meaning to place apart or 
 alone. 
 
 Fig. 68. — Kangaroo. 
 
 Islands that rise from the deep ocean floor far from the 
 continents have no large native animals, but are occupied 
 by such forms of animals and plants as might have readied 
 them by flying, swimming, or floating from the nearest 
 larger land. 
 
THE LANDS. Ill 
 
 The Azores, a group of mid-ocean volcanic islands in the 
 North Atlantic, are so called from the hawks that were com- 
 mon upon them when they were discovered by voyagers from 
 Europe. The Galapagos islands, of similar origin, in the 
 Pacific west of Peru, are named from the tortoises that abound 
 upon them. 
 
 Races of Man. — The homes of the races of man, together 
 with their remarkable differences of language, religion, and 
 form of government, correspond in a general way to the 
 division of the lands into continents. Hence it may be 
 believed that the separation of the continents by the oceans 
 has been the chief cause of the division of mankind into 
 several races. 
 
 Through the greater part of man's existence on the earth 
 his condition has been uncivilized, and his migrations have 
 been of the primitive sort now seen among peoples still sav- 
 age or barbarous, like the wandering Bedouins of the Sahara, 
 or the forest tribes of the Amazon basin. Thus distributed, 
 man has come to be divided into several races, with many 
 branches, stocks, and families. It should not be assumed that 
 all mankind can be divided into a few well-defined races. 
 
 The greatest of the continents, Eurasia, contains two 
 races. The European race, generally white but with 
 some dark-skinned families, has its home in Europe, 
 part of Africa north of the Sahara, and southwestern 
 Asia. The leading nations of this race are the most 
 advanced peoples of the world, having developed liberal 
 governments in which the rights of the people are con- 
 sidered, and having advanced greatly in the cultivation of 
 the arts and sciences. 
 
 The Asian race is found in northeastern Asia; it is 
 often called the Yellow race. China contains the greatest 
 
112 PHYSICAL GEOGRAPHY. 
 
 number of this people. Although comparatively advanced 
 in many arts, the Asians have acquired little knowledge 
 of the sciences, and their governments are usually despotic. 
 America is the home of the American or Red race ; its 
 people is divided into many tribes, each of which is gov- 
 erned by a chief. Africa is the home of the African or Black 
 race, governed by despotic kings or chiefs. Australasia and 
 the peninsulas and islands of southeastern Asia include a 
 number of less important races. Few nations among these 
 races have made important advances toward civilization. 
 
 Within the last few centuries the means of ..travel over land 
 and sea have greatly increased, and to-day the races of man- 
 kind are by no means limited to the continents named above 
 as their homes. People of European ancestry are now the 
 chief part of the population in North and South America, 
 southern Africa, Australia, and ISTew Zealand, as well as in 
 Europe. The Chinese are by no means limited to northeast- 
 ern Asia, but are found in large numbers as merchants and 
 laborers in southeastern Asia, Australia, and elsewhere. 
 Many of the African race are now living in North and South 
 America. 
 
 It should be noticed that, while the people of the European 
 race are now widely distributed over all parts of the world, 
 and while Asians and Africans are found in large numbers 
 in other lands than their homes, none of the less advanced 
 races have migrated into Europe. 
 
CHAPTER VI. 
 PLAINS AND PLATEAUS. 
 
 The Geographical Control of Population. 
 
 Southern New Jersey. — If a traveller should descend 
 from the uplands of southeastern Pennsylvania, cross the 
 Delaware, and proceed over the lowlands of southern 
 
 Fig. 69. — Southern New Jersey. 
 
 New Jersey to the seashore, he might discover that many 
 geographical features, such as the forms of the land, the 
 arrangement of the streams, the mineral products, and the 
 
114 PHYSICAL GEOGRAPHY. 
 
 soils, are here grouped in belts, roughly parallel to the 
 coast line, as in Fig. 69. The upland belt on the border 
 of Pennsylvania has a rolling surface, diversified by nar- 
 row vallej'^s. The soil is good, and most of the upland is 
 cleared for farming. The rock beneath the soil is firm 
 and enduring; quarries are easily opened on the valley 
 sides, and many of the older farmhouses and barns are 
 built of stone thus provided. The streams afford water 
 power for mills, in which grain from the farms is ground. 
 A number of good-sized towns on the Delaware have 
 profited from the easy transportation afforded by river 
 steamboats. The open valley of this large river has long 
 been an important path of travel, a century ago by stage, 
 now by rail, on the line connecting the important cities 
 of Washington, Baltimore, Wilmington, Philadelphia, 
 Trenton, Newark, and New York. Next beyond the 
 Delaware there is a narrow lowland belt, free from firm 
 rocks but deeply underlaid by fine clay. Crockery, earth- 
 enware, terra-cotta, and bricks are made here for domestic 
 and industrial uses. Then follows a belt of slowly rising 
 ground ending in low hills, the most uneven part of south- 
 ern New Jersey. The headwaters of many short streams 
 rise among the hills and run northwest to the Delaware ; 
 between the streams the slope from the hills includes 
 much good farming country, and here are the best farms 
 in the southern part of the state. Beds of marl (limy 
 clay) occur in this belt, frequently containing shells of 
 sea animals. The marl is often dug out to serve as a 
 fertilizer on less productive soils. 
 
 The long gentle slope that leads from the hilly belt 
 southeast to the ocean has for the most part a deep sandy 
 
PLAINS AND PLATEAUS. 
 
 115 
 
 soil generally overgrown with pine forest, and so infertile 
 as to be hardly worth clearing. Here the population is 
 scanty. The surface is so flat that roads, and railroads 
 run for long distances on straight lines. Not a hill is to 
 be seen for many miles. A house or tower that rises over 
 the tree tops discloses " an unbroken extent of dark-green 
 pine forest as far as the limit of vision, stretching away in 
 
 Fig. 70. — The Beach, Atlantic City, New Jersey. 
 
 long, gentle swells," nearly as level as the ocean itself. 
 The streams flowing southeast are sluggisli, and afford 
 little or no water power. The boggy soil of their marshy 
 valleys is sometimes used for the cultivation of cranber- 
 ries. Nearer the shore the plain is somewhat interrupted 
 by shallow valleys, and its surface is more generally cleared 
 and farmed. Short arms of the sea enter the lower valleys, 
 giving harborage for small vessels, and many fishermen 
 live in the shore villages, A belt of shallow salt-water 
 
116 PHYSICAL GEOGRAPHY. 
 
 lagoons with extensive marshes of reeds border the main- 
 land for a breadth of about five miles. Finally come the 
 sand reefs, half a mile or more wide, enclosing the lagoons. 
 The surface of the reefs is occupied by gently rolling sand 
 hills drifted by the wind; the ocean border is smoothed' 
 into a broad beach by the heavy surf. Here thousands of 
 persons from the interior of the country spend their sum- 
 mer vacations, enjoying the mild temperature of the sea 
 breezes, bathing in the surf, and sailing and fishing in the 
 quiet waters of the lagoons, or on the rougher waters of 
 the ocean. 
 
 This simple example serves to illustrate the way in 
 which the physical features of a district exercise a control 
 over the distribution and occupations of its peoj^le. It is 
 not by accident that a large population has gathered on 
 the interior lowland belt, but because of the advantage 
 given by good soil on an open surface where movement 
 from place to place is easy. Many other examples of the 
 same kind may be found by the intelligent observer in 
 various parts of the world. The careful study of geog- 
 raphy therefore requires a good understanding of differ- 
 ent kinds of land forms, as well as a knowledge of their 
 soils and their products, in order to make clear the rela- 
 tion between man and his geographical surroundings. 
 
 The best method of gaining an understanding of land 
 forms is to study their origin. It would be easier to 
 remember the features of the successive belts described in 
 the preceding paragraphs if some explanation were given 
 of the way in which they have been produced. Explana- 
 tion as well as description is therefore important in 
 physical geography. 
 
plains and plateaus. 117 
 
 Coastal • Plains. 
 
 Introductory Example. — In certain parts of the world 
 the hills bordering a mountain range descend directly to 
 the seashore. Waves beat on the headlands, cutting cliffs 
 in their front. The larger rivers build deltas at their 
 mouths, and here the sea is bordered by low land. The 
 rock waste from the mountains and cliffs furnishes much 
 sediment for the smooth sea bottom. 
 
 This means that while the land has been worn and 
 roughened by the action of weather and streams, the sea 
 floor has been smoothed by the gain of land waste. The 
 
 Fig. 71. —Mountains bordering the Sea. 
 
 depth and number of the valleys show that already much 
 waste has been carried into the neighboring seas. The 
 dredge brings up gravel, sand, and mud from the sea bot- 
 tom, the texture of the sediments being finer as distance 
 from land and depth of water increase. 
 
118 PHYSICAL GEOGRAPHY. 
 
 A rugged land like this seldom supports a large population. 
 It is only in the valleys that strips of flat land, suitable for easy 
 occupation, can be found. Most of .the population is gathered 
 in villages near the mouths of the large rivers. Eoads cannot 
 easily follow the shore, for many of the cliffs are washed to 
 their base at every high tide. In passing from one valley 
 village to another the traveller must climb over a ridge. 
 Many dwellers in the shore villages are seafarers and fisher- 
 men, although there are few protected harbors, for the shore 
 line is comparatively straight. 
 
 The coast of California presents many stretches of this kind. 
 The Sierra Santa Lucia, south of Monterey, descends boldly to 
 the sea, its spurs being cut off in great cliffs. The shore is 
 thinly inhabited for a distance of 70 miles. 
 
 The Mediterranean coast from Nice past Genoa to Spezzia 
 is a famous example of this class, more densely populated than 
 usual. The mountain spurs rise rapidly from the water's edge; 
 the streams run like torrents to their very mouths. Little 
 villages nestle in the indentations of the coast, but their fish- 
 ing boats are unprotected in on-shore storms. The harbor of 
 Genoa is enclosed by an artificial breakwater. A railroad fol- 
 lowing this rugged shore is compelled to tunnel through many 
 headlands. No highway has yet been made along the shore 
 east of Genoa. Westward from Genoa to Nice, only with great 
 difiiculty and at great expense has a famous highway been 
 constructed aroimd or over the headlands. 
 
 Narrow Coastal Plains. — Fig. 72 exhibits a region 
 where the foothills of the mountains descend to a low- 
 land, and the lowland slopes gently to the sea. Such a 
 lowland is called a coastal plain. The gentle slope of the 
 plain is continued in the slowly deepening sea floor. The 
 form of the land may here be much more favorable to 
 human occupation than in the previous example. 
 
 The plain is divided into many similar strips by the 
 shallow valleys of streams that flow across it from the 
 
PLAINS AND PLATEAUS. 
 
 119 
 
 mountains. Each strip of the plain is so smooth and so 
 nearly level that a great part of the rainfall enters the 
 open soil, instead of running off in streams. The plain is 
 built of layers of gravel, sand, and clay, the uppermost 
 layer forming the surface of the plain. The pebbles in 
 
 Fig. 72. — Karrow Coastal Plain. 
 
 the gravel often resemble the harder rocks of the hilly 
 background ; the clay often contains shells similar to those 
 found in the neighboring sea. 
 
 Ravines are worn by wet-weather streams in the side slopes 
 of the plains between the larger valleys. Even the larger val- 
 leys have been carved by the rivers that flow through them. 
 In the future the plain will be more dissected; in the past it 
 was less dissected. Before any valleys were cut the different 
 parts of the plain were all united in a continuous, even surface. 
 
 In view of all this it must be concluded that the coastal 
 plain was once part of a shallow sea bottom, and that this 
 region was then like the sea-skirted mountains of the pre- 
 
120 PHYSICAL GEOGRAPHY. 
 
 ceding example. Since then the relative level of the land 
 and sea has been altered, and part of the smoothed sea 
 bottom is now laid bare to form the coastal plain. 
 
 As soon as this simple relation is recognized, the background 
 of hills and mountains is seen to be the source of the rock 
 waste of which the strata of the plain are built. The inner 
 boundary of the plain is the former shore line. The rivers 
 from the older land extend their courses across the new plain, 
 guided by its gentle slope to the new shore line. Some small 
 streams may rise on the plain and flow by shorter direct courses 
 to the sea. 
 
 As the region now stands higher than before, the rivers 
 tend to wear down their valleys to the new level of the 
 sea at their mouths ; the valley sides waste away, and thus 
 the valleys slowly become wider ; but the streams cannot 
 wear the valleys deeper than the surface of the sea at 
 their mouths. The level of the sea is therefore called 
 the baselevel of the region. As long as the land stands 
 in its present position, continually wasting under the de- 
 structive attack of the atmosphere, the plain surface will 
 in the course of ages be worn lower and lower, closer and 
 closer to the baselevel. In the coastal plain here figured 
 a good beginning of this great task is accomplished along 
 the line of the chief stream ; but the uplands between the 
 valleys are as yet hardly touched. 
 
 A simple method of describing land forms may be illus- 
 trated by means of this elementary example. The exist- 
 ing forms of the coastal plain must be treated as showing, 
 first, something of the original form of the plain; and, 
 second, the changes it has suffered under the attack of 
 weather and water. In this example the smooth surface 
 
PLAINS AND PLATEAUS. 
 
 121 
 
 of the plain between the valleys still preserves the original 
 form with insignificant change. The valley floors of the 
 extended rivers and the narrow ravines of the side streams 
 are changes from the original form. 
 
 The surface of each part of the plain is everywhere so much 
 alike in form and quality that villages may be located here 
 and there upon it without system. Roads run in straight lines 
 for long distances because they meet no obstacle. Boats on 
 the larger rivers coming from the mountains in the background 
 bring the products of mines 
 
 and quarries, of forests and 
 upland pastures. A city near 
 the sea serves as a market 
 for the agricultural products 
 of the plain, although these 
 are sometimes not of the best, 
 for the sandy soils may be 
 hardly worth tilling. 
 
 Sand reefs or beaches may 
 be formed by the waves a little 
 distance off-shore, built of sands 
 washed in from the sea floor at time of 
 storms. The reefs are covered with dunes 
 of sand blown up from the beach by the 
 winds, and enclose quiet, marshy lagoons. 
 Here or there the tide maintains a passage or inlet through 
 the reef, and villages spring up on the mainland near by, 
 whence fishermen go out in small boats to the shallow sea. 
 
 The eastern coast of Mexico in the neighborhood of Vera 
 Cruz is bordered by a low coastal plain (Fig. 73) about 50 
 miles widcj back of which the mountains rise rather abruptly. 
 The plain is called the " tierra caliente," or hot country. It 
 is sandy, malarial, and relatively infertile. Vera Cruz, the 
 chief port for the interior highlands, has a poorly protected 
 
 Fig. 73. — Coastal 
 Plain of Mexico. 
 
122 
 
 PHYSICAL GEOGRAPHY. 
 
 anchorage on the open shore. In the Mexican War (1847), 
 when Vera Cruz was captured, the Mexicans found no other 
 place for resistance on the smooth coastal plain, and therefore 
 concentrated their forces on the hilly border of the old land. 
 
 Here they entrenched 
 themselves on a spur 
 called Cerro Gordo, be- 
 tween two ravines that had 
 been deepened by streams 
 from the mountains after the 
 region was uplifted; and here- 
 decisive battle was fought. 
 3 uplands of the Dekkan in the 
 peninsula of India (Fig. 74) are bor- 
 dered on the east by a gently sloping 
 coastal plain, not more than 50 miles 
 wide. It consists of bedded gravels, 
 sands, and clays containing marine or 
 brackish-water shells. Large rivers, the 
 Godavari and Kistna, draining great areas of 
 the older land, have extended their course 
 across the plain and built projecting deltas at 
 its front. Madras,. the chief city of the plain, has 
 Coastal Hain no harbor ; it is difficult or impossible to land from 
 vessels during storms, except under the protection 
 of an artificial breakwater. 
 
 Broad Coastal Plains. — Fig. 75 represents a broader 
 coastal plain than the preceding example. The outer 
 part of this plain is much like the plain in Fig. 72 ; but 
 the inner part is more cut by ravines, and the larger rivers 
 have broader valleys than before. A greater change iii 
 the relative height of land and sea is indicated by the 
 greater height and breadth of the plain ; and a longer 
 time since the elevation of the inner than of the outer 
 
 Fig. 74. 
 
PLAINS AND PLATEAUS. 123 
 
 part must be inferred from the greater amount of work 
 done by the streams in carving their valleys and ravines. 
 
 The strata of an extensive coastal plain are often of coarser 
 texture near the former shore line, and of finer texture near 
 the present shore line. During the slow uplift of the plain, 
 
 Fig. 75. — Broad Coastal Plain. 
 
 different kinds of sediments may have been laid down near 
 the shore, as the sea retired from the plain. Hence the soils 
 of such plains are commonly of different kinds in the inner, 
 middle, and outer parts, being arranged in belts roughly 
 parallel to the length of the plain. 
 
 The Atlantic coastal plain of the southern states, of 
 which a characteristic portion is included in South Caro- 
 lina (Fig. 76), is roughly divisible, according to its form 
 and soil, into belts parallel to the shore line. At the same 
 time it is transversely divided into strips by the several 
 large rivers that are extended from the back country 
 (Piedmont belt), and by the many smaller branches of 
 these rivers that rise on the plain itself. 
 
124 
 
 PHYSICAL GEOGRAPHY. 
 
 The outer or coastal lowland is a smooth plain, with open 
 pine woods or grassy savannahs ; this division is about 50 
 miles wide, rising inland 2 or 3 feet to a mile. Its level 
 surface is very poorly drained. 
 
 Further inland the plain slowly rises with gently rolling 
 surface ; here the soil is better than in the first belt, and 
 much cotton is raised. Further inland still, the surface 
 becomes more sandy again and more hilly, giving extensive 
 views seaward across the lower plain. A hundred miles 
 inland a belt of hilly uplands stands 600 or 700 feet above 
 
 Fig. 76. — Coastal Plain of the Carolinas. 
 
 the sea, covered with pine forests. Here the original surface 
 of the plain is almost entirely destroyed by the action of 
 many streams in carving their valleys; and by the action of the 
 weather in opening the valley slopes ; and this part of 
 the plain may be described as " well dissected." Then come 
 the hills of the older land (the Piedmont belt, here not moim- 
 tainous, but of moderate relief), whence the strata of the plain 
 have received their sediments, and where the rivers are now 
 cutting down narrow valleys beneath their former valley 
 floors. 
 
PLAINS AND PLATEAUS. 125 
 
 The soil belts on this plain exert an important control over 
 the industries of the inhabitants. The less sandy soils are 
 occupied by cotton plantations ; the more sandy belts are 
 covered with extensive pine forests, furnishing much lumber 
 and a great amount of tar and turpentine. The moist swampy 
 soils near the coast are well adapted to the cultivation of rice. 
 The more limy parts of certain strata are dug up to fertilize 
 the more sandy fields, and the richest of these limy deposits 
 are exported to other states to be used as fertilizers. 
 
 The strata of the plain are generally of too loose a texture 
 to supply good building stone or material for making hard 
 roads ; the time that has passed since the strata were de- 
 posited has not been sufficient for their consolidation. There 
 are no metalliferous ores, and mining is unknown on plains 
 of this kind. 
 
 The rivers that are extended from the older land have 
 incised their valleys 400 or 500 feet in the inner part of 
 the plain, so that they cannot cut down closer to base- 
 level without losing the velocity they need in order to 
 carry along their load of waste. Their branches have 
 dissected the upland for several miles on each side, chang- 
 ing the original surface of the plain into an irregular and 
 hilly form. 
 
 Passing seaward the valleys become shallower, and the 
 uplands are less and less dissected. The rivers have developed 
 serpentine or meandering courses on the marshy valley floors. 
 Columbia lies on Congaree river, where it passes from the 
 older land to the dissected plain. Charleston and other ports 
 lie at the edge of the coastal lowland, on the widened courses 
 of certain rivers where the tide comes in from the sea. The 
 outer coastal plain is so even that its railroads run long 
 stretches without a curve. 
 
 In North Carolinia numerous farms on the coa,stal plain 
 furnish vegetables for the markets of northern cities. The 
 
126 
 
 PHYSICAL GEOGRAPHY. 
 
 lower part of the plain is so level that extensive swamps form 
 upon it ; for vegetation here hinders the run-off of the rain- 
 fall, and in course of time a deep boggy or peaty deposit has 
 accumulated. Water-loving trees, like the cypress and tupelo, 
 form the forest cover, delaying evaporation, and thus favor- 
 ing the swampy growth beneath. Here the forces that tend 
 
 Fig. 77. — North Carolina Truck Farm. 
 
 to wear down the land are so weak that they are overcome 
 by plant growth, and the land is built up. Artificial ditches 
 and canals may lead away the water, and some of the swamp 
 land has been farmed after clearing off the trees. 
 
 Artesian Wells. — Towns and cities near the shore line 
 of coastal plains frequently secure a good water supply by 
 sinking deep wells until a sandy layer between clayey 
 layers is reached 500 or 1000 feet below the surface. 
 The same sandy layer comes to the surface of the plain 
 many miles inland, where the land "is several hundred 
 feet higher than at the shore line. There much of the 
 
PLAINS AND PLATE AITS. 127 
 
 rainfall soaks into the sandy soil, and slowly follows 
 the descent of the open-textured sandy layer between the 
 close-textured clayey layers. When tapped by a deep 
 well, the water rises from the sandy layer, and may even 
 flow forth at the surface like a fountain ; for the level of 
 its discharge is much lower than that of its supply. Wells 
 of this kind are called artesian wells. 
 
 In Fig. 78, the layers reached by the wells lead ground 
 water from the inner part of the coastal plain toward the 
 ocean. The other layers are of close texture and contain 
 very little ground water. 
 
 Fig. 78. — Artesian Well. 
 
 Public health is promoted by the use of artesian well water, 
 which is much purer than the water of shallow wells on low 
 coastal plains. Numerous artesian wells are sunk on the 
 outer part of the Atlantic coastal plain of the United States. 
 Even the off-shore sand reefs may gain a supply of fresh water 
 from deep wells, as at Atlantic City, N. J. 
 
 The Pall-Line. — A large river whose course is extended 
 across a coastal plain often has a well-defined head of 
 navigation at low falls or rapids near the inner margin of 
 the plain. The falls occur where the entrenched river 
 passes from a steeper slope on the resistant rocks of the 
 older land to a nearly level channel excavated in the weak 
 strata of the plain. 
 
128 
 
 PHYSICAL GEOGRAPHY. 
 
 This may be accounted for as follows : BC (Fig. 79) was 
 the level of the sea while the strata of the coastal plain, 
 FBG, were accumulating on the submarine extension of the 
 old land, BG. Before the plain was uplifted, the larger 
 rivers had cut valleys of gentle slope, AB, leading to the 
 baselevel, B, at the shore line of that time. To-day DE is 
 baselevel. The larger river has already cut a nearly level 
 
 Fig. 79. — Diagram of the Fall-Line. 
 
 channel, HJ, in the weak strata of the plain, but has only 
 deepened its channel from AB to LNH in the harder old-land 
 rocks. As long as NH\% steep enough to make falls or rapids, 
 H is the head of navigation ; and a line joining such points 
 on successive larger rivers is called the fall-line. 
 
 In coastal plains of considerable breadth settlements 
 near the mouth and at the head of navigation on the 
 larger rivers often develop into important cities. The 
 lower city is the seaport of the region. The upper city 
 bears closer relation to local industries and traffic; it lies 
 in the midst of a diversified region, with strong water 
 power for manufacturing the varied products of rock and 
 soil. 
 
 The fall-line along the inner margin of the Atlantic coastal 
 plain of the United States is marked by important cities on 
 nearly every large river that crosses it. Trenton, Phila- 
 delphia (at the falls of the Schuylkill), Richmond, Raleigh, 
 
PLAINS AND PLATEAUS. 
 
 129 
 
 Camden, Columbia, and Augusta are all thus located. The 
 deep and narrow valleys of these rivers in the older land are 
 also conspicuous results of the elevation of the coastal plain. 
 
 Embayed Coastal Plains. — The region here figured does 
 not at first sight seem to belong to the family of coastal 
 plains. Long shallow arms of the sea enter between low 
 hilly arms of the land. Large rivers from the back coun- 
 try enter the heads of the long bays ; small streams from 
 every little valley between the hills of the land arms enter 
 little bays or coves on the sides of the larger bays. 
 
 The bay heads are occupied by marshy deltas ; the land 
 heads between the bays are nipped off in low cliffs showing 
 layers of sand and clay. The outer ends of the land 
 
 Fig. 80. — Embayed Coastal Plain. 
 
 arms, fronting the open ocean, are more or less cut off. 
 Sand reefs are stretched in even line, connecting the outer 
 headlands so that the sea has now access to some of the 
 bays only by narrow tidal inlets ; but the broader bays may 
 still be open to the ocean. 
 
130 PHYSICAL GEOGRAPHY. 
 
 This region, represents a. coastal plain whicli has been 
 partly sunk or " drowned " beneath the sea. Before drown- 
 ing, the valleys had been widely opened, and the plains 
 between them had been reduced to strips of hills. Now 
 the outer coastal lowland and the broad valley floors are 
 under water, the latter being occupied by the bays that 
 enter far toward the old land, while the hill strips stand 
 forth as ragged arms of the land. The former simple shore 
 line is thus exchanged for a very irregular shore line. 
 
 The relative change in the attitude of land and sea is here 
 opposite to that inferred in the previous examples. Since the 
 depression of the region, the land heads have been more or 
 less cut back by the waves, and the bay heads have been 
 somewhat hlled by marshy deltas. But the drowning cannot 
 have taken place long ago, as the earth counts time, for the 
 changes in the land heads and bay heads are of moderate 
 amount. Although at first not seeming to be related to other 
 examples of this series, this irregular land form is now seen 
 to be little removed from them. 
 
 The Atlantic coastal plain from Delaware bay to Pam- 
 lico sound presents many examples that fall under this 
 class. They are best seen about Chesapeake bay and the 
 lower Potomac, where the relief is stronger and the bays 
 are longer than further north and south. The outer shore 
 line is for the greater distance a smooth sand reef enclosing 
 a lagoon ; but at a few points the reef is exchanged for a 
 low bluff cut in an arm of the mainland, as in the south- 
 east corners of Delaware and Virginia. Low cliffs have 
 been cut in the little land heads and small marshes have 
 been formed in the little bay heads of the inner shore 
 line. 
 
PLAINS AND PLATEAUS. 
 
 131 
 
 Partly drowned coastal plains exert a peculiar control over 
 the distribution and occupation of their population. The 
 greater part of the valley lowlands is lost, and the people 
 must make the most of the hilly land arms that remain above 
 sea level. The axis of each of the larger arms is generally 
 followed by a main road, making its way from village to 
 village among the upland farms, and giving forth side roads 
 to the smaller land arms or to the little bay heads. 
 
 Villages are found on the more level parts of the upland 
 and on the better harbors of the bays. The shallow bays arc 
 
 Fig. 81. — A Branch of Chesapeake Bay, Maryland. 
 
 valuable for fishing grounds. More important centers of 
 population are found either near the heads of the larger bays, 
 where the large rivers come out from the back country and 
 reach tide water, or near the mouths of the bays where the 
 sand reefs are not continuous and the ocean is easily reached. 
 Baltimore and Norfolk are good examples of cities thus situ- 
 ated. The outer shore line is inhospitable ; its long sand 
 reef offers no landing place ; and the narrow tidal iiilets allow 
 entrance only to small-sized vessels. 
 
 In the early history of " tide-water Virginia," the numerous 
 drowned valleys afforded easier communication between the 
 
132 
 
 PHYSICAL GEOGRAPHY. 
 
 settlements than was found overland through the forests of 
 the coastal plain. 
 
 The interesting question of the origin of the forces suf- 
 ficient to deform the crust of the earth and to elevate or 
 depress a coastal plain cannot be well explained in the present 
 state of science. It is important that the student of physical 
 geography should recognize the facts of elevation and depres- 
 sion, and should understand the importance of such movements 
 in controlling the forms of the lands and in determining the 
 conditions of their inhabitants ; but the processes that cause 
 such movements must be left to the more advanced study of 
 geology. 
 
 Belted Coastal Plains. — Fig. 82 exhibits a district lying 
 between a hilly inner land and a new shore line,. in which 
 the strata have the same seaward slope that prevails in all 
 
 Fig. 82. — A Belted Coastal Plain. 
 
 coastal plains, but in which the form is novel. The district 
 may be divided into three longitudinal belts, each one 10, 
 20, or more miles wide ; the innermost (A) is a lowland of 
 
PLAINS AND PLATEAUS. 133 
 
 weak strata and fine deep soils ; tlie middle belt (B) is an 
 upland of firmer strata and thinner soils, several hundred 
 feet above the lowland; the outer belt (6^) is a smooth coastal 
 lowland. The several belts recall the belt-like arrange- 
 ment of soils described in the case of a broad coastal plain, 
 but this example is peculiar in having the middle belt 
 occupied by an upland that runs about parallel to the shore 
 line and stands between an inner and an outer lowland. 
 The upland descends by a rather steep slope facing inward 
 to the inner lowland, and by a long, gentle, outlooking 
 slope to the coastal lowland.^ 
 
 The reason for this arrangement of upland and lowland is 
 that the undermost layers of the coastal plain are weaker than 
 the middle layers ; hence the under layers, which reach the 
 surface of the plain near its inner border, are already worn 
 down to a lowland, while the more resistant middle layers 
 preserve an upland height. 
 
 The drainage of a belted coastal plain possesses some 
 peculiar features. The larger rivers, extended from the 
 inner hills, still run directly to the sea, passing across the 
 inner lowland in shallow open valleys, and trenching 
 through the upland belt in deep narrow valleys. Smaller 
 streams are extended from the older land to the inner 
 lowland, there turning to the right or left and forming 
 longitudinal streams that run about parallel to the upland 
 belt until they reach a large transverse river. The longi- 
 tudinal streams are also joined by short streams that flow 
 down ravines in the in-facing slope of the upland belt. 
 
 1 An upland of this kind may be called, a cuesta, following a name of 
 Spanish origin used in New Mexico for low ridges of steep descent on one 
 side and gentle slope on the other. 
 
134 
 
 PHYSICAL GEOGRAPHY. 
 
 When these arrangements of form, soil, and drainage are 
 well marked, the distribution and occupations of the people 
 become closely sympathetic with them. The outer coastal 
 lowland has its fishermen and sailors, with ports at the river 
 mouths and villages on the smaller streams ; it also has 
 interests in pastures, forests, and farms. 
 
 The inner lowland is generally an agricultural district, 
 often of great fertility. It provides a longitudinal inland 
 pathway of even surf ace, often followed by highways and rail- 
 roads. The junction of longitudinal streams with a large 
 transverse river makes an attractive place for settlement; it 
 
 has convenient relations with 
 the old land and the inner low- 
 land, with the advantage of open 
 passage to the sea. Water power 
 may be furnished by rapids at 
 the fall-line. 
 
 The upland belt is more sparsely 
 populated ; its thinner soils may 
 hardly repay cultivation, and 
 much of it may remain forested. 
 
 The coastal plain of Ala- 
 bama (Fig. 83), part of the ex- 
 tension of the Atlantic coastal 
 plain around the border of the 
 Gulf of Mexico, possesses an 
 upland belt and an inner low- 
 land. The older land is the 
 southern end of the Appalachian mountains, here of no 
 great height ; it is a region of resistant rocks containing 
 iron ore and coal beds, which support the important indus- 
 tries of mining, smelting, and manufacturing. The strata 
 of the coastal plain are generally still of loose texture, 
 
 ULF OF M E X J a O'^^-^^ c^ 
 
 Fig. S3. — The Coastal Plain of Alabama. 
 
Plains and plateaus. 
 
 135 
 
 those of the upland belt behig the firmest. They contain 
 marine fossils, some of the strata being largely composed 
 of shells. 
 
 The inner lowland is worn down so smooth and level that 
 the rainfall is drained slowly from its surface; the roads are 
 nearly impassable in wet weather. It is called the " Black 
 prairie " from tlie dark 
 color of its rich £ i 
 weathered from the w( 1 
 underlying limestoi 
 This belt includes i i 
 best cotton district of ^ Ii 
 state, the cities of Mem 
 gomeiy and Selma k 
 withm it r , ^ 1 i>* S- «S '« 
 
 The upland, local' ';^^y, j,^^, ifj .'l^^' ')l^x.]l^ 
 known as the Chun t- /^''Milivl- V''^- r flu #1 
 
 "I • - 
 
 ■*'-»wV 
 
 Fig. 84. — Pine Forest on Coastal Plain, Alabama. 
 
 nugga ridge, ascends rather abruptly 200 feet above the low- 
 land ; it is upheld by a stratum of more resistant limestone. 
 I^umerous short streams run down the infacing slope to the 
 inner lowland, wearing short valleys and fringing the inner 
 margin of the upland with hills. The '' hill prairies " lie on 
 the broad upland surface. 
 
136 
 
 PHYSICAL GEOGRAPHY. 
 
 The outer slope descends gradually to tlie " coastal prairies," 
 the surface being dissected by small streams in shallow valleys. 
 Extensive pine forests occur here as well as on the upland. 
 Mobile, an important port of the Gulf coast east of the Mis- 
 sissippi, lies on the slightly drowned lower course of the 
 united rivers of the region. 
 
 Ancient Coastal Plains. — In Wisconsin, far inland from 
 the ocean, the northern part of the state is occupied by 
 
 rugged highlands 
 of resistant rocks. 
 Adjoining on the 
 south and east are 
 jDlains and uplands 
 arranged in belts, 
 their rock layers 
 sloping gently 
 away from the 
 highlands and lap- 
 ping on one an- 
 other like great 
 shingles. 
 
 Fragments of the 
 highland rocks are 
 found in the lower members of the overlapping strata ; numer- 
 ous marine fossils, like corals and shellfish, occur in many 
 layers. All the layers are well consolidated; the firmer ones 
 form the uplands, with distinct infacing slope and very gentle 
 outward descent ; the weaker layers underlie the plains. 
 
 Although the sea may now be a thousand miles away, the 
 belts of upland and plain are easily seen to be similar to the 
 belted coastal plains already described, while the rugged high- 
 lands stand in the relation of the older land from which the 
 strata of the plains and uplands were long ago derived. 
 
 Fig. 85. — Ancient Coastal Plain of Wisconsin. 
 
PLAINS AND PLATEAUS. 137 
 
 Tlie strata here observed are generally so well cemented 
 that they must be much more ancient than those of the earlier 
 examples ; a long period in the earth's history is needed for 
 infiltering waters to bind together sediments grain by grain. 
 Some of the strata are crossed by fissures containing lead ore 
 in quantities sufiS-cient for profitable mining. This also sug- 
 gests great age ; for a vast duration of time is necessary to 
 gather the minerals of the ore from the surrounding strata 
 through which they were originally scattered, and to concen- 
 trate them i^ fissures by the action of slowly infiltering waters. 
 The seashore is now a great distance away, and this also 
 implies a long time during which the continent has grown to 
 its present dimensions by repeated uplifts. 
 
 In view of all this it must be concluded that this is not 
 a modern but an ancient coastal plain ; that is, a region 
 that began its history as a coastal plain ages ago in the 
 earth's history, and that has since then been built into the 
 interior of the continent by successive uplifts and addi- 
 tions to the margin of the growing continental area. The 
 upper layers of the original coastal plain have been greatl}^ 
 worn away, and a considerable part of the highland border 
 is stripped of the strata that once lapped over it. 
 
 Artesian wells are as important a source of water supply on 
 ancient as on modern coastal plains. Many such wells have 
 been bored in southern Wisconsin. 
 
 In passing southward from Canada to western Pennsylvania 
 one crosses an ancient coastal plain with its strata dipping 
 gently southward, and bearing various signs of early origin. 
 The highlands of Canada are the older land. Next comes an 
 inner lowland, the Ontario lowland plain, in part occupied by 
 Lake Ontario. Then follows the Niagara upland belt formed 
 on the firm limestone beds of that name, and famous for the 
 gorge cut by the great cataract. A second lowland, the Erie 
 lowland plain, stands a little higher than the first, partly 
 
138 
 
 PHYSICAL GEOGBAPHY. 
 
 occupied by Lake Erie ; and finally conies a rather strong 
 infacing slope ascending to a dissected uj)land, the northern 
 part of the Allegheny plateau. 
 
 The Niagara upland fades eastward as its limestone layer 
 thins out, and is not seen beyond Rochester, where the 
 Ontario and the Erie lowlands come together. The Allegheny 
 
 plateau weakens west- 
 ward, and is not trace- 
 able beyond Cleve- 
 land. Eastward it 
 becomes stronger; 
 the irregular infacing 
 slope is much dis- 
 sected by valleys, and 
 frequently consists of 
 several successive 
 benches. It extends 
 to the bold Helder- 
 berg escarpment 
 southwest of Albany 
 
 Fig. 86. — Ancient Coastal Plain of Ontario and New York. (SCC -tig. vZ), WJiere 
 
 the Adirondacks rep- 
 resent the older land and the Mohawk valley is the narrow 
 inner lowland. 
 
 The rugged highlands of Canada and the Adirondacks are 
 heavily forested. The Allegheny plateau is so hilly that its 
 population is relatively small. The Ontario and Erie plains, 
 where not drowned by their lakes, contain a thriving popula- 
 tion. The Mohawk valley in particular has long served as a 
 path of travel and transportation. The Erie Canal connects 
 the tidal Hudson with Lake Erie. Important railroads follow 
 the same course. The southern part of the lowland has thus 
 come to be the seat of many cities in a rich agricultural popu- 
 lation. Albany, Schenectady, Utica, Syra-cuse, Auburn, Roches- 
 ter, Buffalo, Erie, and Cleveland all lie on the plain near the 
 border of the plateau. 
 
PLAINS AND PLATEAUS. 
 
 139 
 
 A beautiful example of an ancient coastal plain is found in 
 England. Its successive features are encountered while pass- 
 ing from the older land of Wales to London and down the 
 Thames to the North Sea. They are roughly shown in Fig. 87, 
 where the heights are much exaggerated. Here, curiously 
 enough, the mountainous older land (A) lies next to the 
 Atlantic, and the coastal plain slopes toward the continent of 
 Europe. The plain no longer retains anything of its original 
 surface, unless in parts of eastern England, where the latest 
 
 ^^^^^ft 
 
 
 ^^^ 
 
 c 
 
 D 
 
 
 .___£;_^ 
 
 ^?S^l^efe§vS^^^ 
 
 ■ 
 
 
 M 
 
 R 
 
 Hi 
 
 Fig. 87. — Diagram of Ancient Coastal Plain of Middle England. 
 
 elevation has added a young coastal lowland (F) to the former 
 land area. Nearer the older land there are two well-defined 
 upland belts, the Cotswold (C) and Chiltern (E) hills; and 
 two lowlands, those of Worcester (B) and Oxford (D). All 
 these features have a considerable extension to the northeast 
 and southwest, with varying strength and expression. 
 
 Inland Plains and Plateaus. — The relation of certain 
 regions, composed of nearly horizontal rock layers, to an 
 older land is not so simple as in the plains thus far 
 described. Several examples of this kind will be given 
 in which the older land need not be considered. 
 
 Young Plains The great plain of western Siberia, in 
 
 latitude 60° to 60° N., stands at a moderate altitude above 
 
140 PHYSICAL GEOGRAPHY. 
 
 sea level, and preserves an even surface over hundreds of 
 miles. Vast areas, stretching further than the eye can 
 reach, are monotonous in the extreme, almost as uniform 
 in soil as in surface. The flat areas between the streams 
 are as yet practically undivided among the rivers, having 
 no distinct lines of water parting and no distinct channels 
 of water discharge. Marshes, alternately wet and dry in 
 winter and summer, and many shallow lakes lie in faint 
 depressions ; as if slight inequalities in the original sur- 
 face of the plain had not yet been drained by river action. 
 The valleys are few and far between; they can never be 
 cut deep while the region stands low. They are narrow; 
 hence the rivers have as yet worked only for a compara- 
 tively short time in the earth's history. The plains are 
 still young. 
 
 The more northern part of the central plains is forested ; 
 but about latitude 50° to 55° the plains have a lighter rainfall 
 and are treeless ; clothed with thin grass in summer ; cold, 
 barren, and wind-swept in winter. Taken with similar low 
 plains further north and south, the vast area from the Caspian 
 Sea to the Arctic differs much less in form than in climate ; 
 they are frozen in the north, parched in the south, temperate 
 in the middle. 
 
 The plains have long been the home of wandering tribes, 
 whose wealth is not in fixed possessions, but in herds and 
 flocks driven from place to place for pasture. The people live 
 in tents, and move about without definite limits to their lands. 
 Every man is necessarily a horseman, competent in nearly all 
 the arts of a wandering life. The horse, descended from a 
 long line of prehistoric ancestors on open plains, has lost the 
 lateral movement of the limbs that climbing and flesh-eating 
 animals possess, but has at the same time gained in speed and 
 endurance, thus becoming the mainstay of wandering tribes. 
 
PLAINS AND PLATEAUS. 
 
 141 
 
 Young Plateaus. — Fig. 88 represents part of an exten- 
 sive upland or plateau that is traversed by deep and narrow 
 valleys or canyons branching in various directions. The 
 plateau is built of horizontal rock layers of various kinds, 
 well shown in the canyon walls. The broad upland has a 
 comparatively even surface, often so monotonous that it 
 receives less attention from explorers than the canyons 
 that dissect it. The irregular course of the canyons indi- 
 
 Fig. 88. —A Plateau in Arizona. 
 
 cates that the rivers which cut them had no well-defined 
 slope on the original upland to guide their flow. The 
 irregular branching of the side canyons shows that it has 
 been about as easy for the streams to wear back the head- 
 water ravines in one direction as in another. 
 
 The great altitude of the uppermost stratum, forming the 
 general surface of the upland, and the depth to which the 
 canyons have been worn down by the rivers prove that 
 the whole region has been broadly uplifted from the sea in 
 which the strata were laid down. 
 
142 
 
 PHYSICAL GEOGRAPHY. 
 
 In regions of this kind some of the side canyons are 
 still so narrow that the stream occupies all the space at 
 the base of their walls ; it flows mostly on bare rock with 
 rapid descent. Such a stream is deepening its valley by 
 grinding the rock bed with the fragments of rock waste 
 that it washes down. Other valleys are somewhat broader, 
 part of their floor being occupied by narrow strips of 
 
 Fig. 89. — Diagram of Narrow Canyon. 
 
 flood plain, overflowed by the river at the time of high 
 water. Here the river has almost ceased to deepen the 
 valley; the slope of its channel just gives it velocity 
 enough to wash along, the waste that is weathered from 
 the valley walls and worn from the side canj^ons. 
 
 Although a great deal of work has been done in cutting 
 down and widening these canyons, it is manifest that a 
 vastly greater work still remains to be done before the 
 broad mass of the plateau is worn down close to base- 
 level ; hence a plateau of this kind must be called young, 
 however deep its canyons may be. 
 
PLAINS AND PLATEAUS. 
 
 143 
 
 In the narrower canyons the descent from the plateau leads 
 down over a succession of cliffs and slopes. The cliffs are 
 the edges of resistant layers (b, c, d, e, Fig. 89) ; they, advance 
 around every spur and turn into every side ravine, but always 
 follow the level of the guiding layer. The slopes follow the 
 weak layers ; they are covered with coarse rock waste, or 
 talus, weathered from the cliffs above. The rock waste 
 weathers and falls from each cliff", and rolls, washes, and 
 
 Fig. 90. — Diagram of Widened Canyon, 
 
 creeps down each slope to the top of the cliff next below, 
 where it falls again; thus at last reaching the stream, where 
 its finer parts are rapidly washed away. Thus the cliffs and 
 slopes wear back or retreat, and the canyon widens. 
 
 As a canyon widens, the thickest and strongest cliff-maker 
 (c, Fig. 90) wears back more slowly than the thinner, less 
 resistant cliff-makers. The less resistant cliffs below the 
 stronger one wear back till they nearly or quite disappear 
 beneath the talus, as a, h. The faster retreat of the less 
 resistant upper cliff d leaves a platform or bench sloping 
 gently forward from the base of the talus to the top of the 
 stronger cliff c. In the same way a platform stretches for- 
 
144 PHYSICAL GEOGRAPHY. 
 
 ward from the base of the talus of c to the top of the cliff d. 
 Fine waste from the talus is washed forward across the plat- 
 form. 
 
 The steeper streams of young plateaus leap in rapids or 
 falls where they descend across the edges of cliff-making 
 strata. The streams rasp and cut back the fall-making 
 strata with the waste that they carry, and the falls there- 
 fore retreat up stream. In the larger rivers the falls are 
 worn back and extinguished while the plateau is still 
 young. In the smaller streams falls may survive until 
 the plateaus are thoroughly dissected. 
 
 Fig. 91 is a section along a stream in a plateau, in which a 
 fall occurs at B. The fall will be extinguished when it is 
 
 Fig. 91. — Diagram of a Waterfall in a Canyon. 
 
 worn back so far up stream that the backward extension BD 
 of the river bed AB intersects the top of the fall-making 
 stratum JECD. 
 
 The lofty plateaus of north Arizona, traversed by the 
 Grand Canyon of the Colorado from east to west (see 
 frontispiece), include many illustrations of this class of 
 forms. The Sheavwits plateau, at a general altitude 
 of 6000 feet, may be taken as a type example; it is cut 
 across by the western part of the canyon. 
 
 The arid climate of the plateau excludes nearly all vegeta- 
 tion, and lays bare the details of structure and form. The 
 region offers no temptation to settlement, however marvellous 
 
PLAINS AND PLATEAUS. 145 
 
 it is to the explorer. It is naked and desolate, occupied by a 
 few Sheavwits Indians, who subsist by " cultivating little 
 patches of corn, gathering seeds, eating the fruits and fleshy 
 stalks of cactus plants, and catching a rabbit or lizard now 
 and then ; dirty, squalid, but happy, and boasting of their 
 rocky land as the very Eden of the earth." 
 
 The great elevation of this plateau permits an exceptional 
 depth of canyon cutting. The massive strong and weak strata 
 of which the plateau is built produce strong cliffs and long 
 talus slopes on the canyon walls. Far down in the bottom of 
 the great trench runs the tawny Colorado, turbid with waste 
 that is showered from the walls in rocky avalanches or swept 
 in from side canyons by cloud-burst torrents. 
 
 Deep as the canyon is, it has been cut down only by the 
 river. There is no indication of clefts or fractures along 
 the river course. The strong rock layers in the walls weather 
 more slowly in the dry climate there prevailing than they 
 would in a wetter climate ; hence the plateau is advancing 
 with relative slowness toward a well-dissected form. 
 
 Unlike most great rivers, whose valleys serve as paths of 
 travel, the Colorado is almost inaccessible along its canyon. 
 Only one exploring party has successfully gone down the 
 canyon ; their narrative is a wonderful history of scientific 
 adventure. Once entering the canyon in their boats, retreat 
 was impossible against the swift current. Escape by climb- 
 ing the walls was hazardous. To descend the river was easy 
 on its smooth stretches, even though hemmed in by great 
 cliffs ; but cascades had to be passed where the most resistant 
 beds are not yet cut through, and rocky rapids obstruct the 
 channel where side canyons deliver heaps of boulders to 
 the main river. After many perils the party came out to the 
 open lower country, west of the Sheavwits plateau. 
 
 In the young stage of dissection plateaus are, as a rule, 
 occupied only on their upland surface. The elevation of 
 the upland is an advantage in the torrid zone, where the 
 
146 PHYSICAL GEOGRAPHY. 
 
 high temperature prevailing at sea level is willingly 
 exchanged by civilized races for more moderate tempera- 
 ture at altitudes of several thousand feet. But in the 
 temperate zone a high plateau is at a disadvantage from 
 the rigor of its winters as well as from its difficulty of 
 access. 
 
 The canyon-like valleys are obstacles to movement; 
 they serve as barriers (except to birds and winged seeds) 
 between the uplands on each side. They are seldom 
 inhabited, unless by the people of a persecuted tribe, who 
 sometimes take refuge as "cliff-dwellers" in the recesses 
 or caves that are often excavated between cliff base and 
 talus top. 
 
 Even in a moist climate the bare rocky cliffs of canyon 
 walls are in effect so many small deserts, almost free from 
 plant and animal life. The steeper talus slopes may support 
 trees and bushes ; where a little finer waste accumulates, 
 smaller plants may also grow. Caves and burrows among 
 loose rocks shelter many kinds of animals ; but a talus slope 
 is too steep and coarse textured for higher uses. Conquered 
 races, driven from wider possessions, may settle on the broader 
 upland platforms or on the flood plains of the more open 
 valleys ; but these surfaces are too limited in extent and, in 
 plateaus of strong relief, too isolated to attract the more 
 fortunate and powerful races. 
 
 Dissected Plateaus. — The rugged u^Dlands that extend 
 continuously from New York to Alabama, known as the 
 Catskill, Alleghen}^ and Cumberland plateaus, may here 
 be treated together under the second name. The whole 
 region consists of nearly horizontal strata. The hilltop 
 view generally discloses an even sky line, which may be 
 
PLAINS AND PLATEAUS. 
 
 147 
 
 taken roughl}^ to define a surface that once extended over 
 the whole region, before the valleys were carved. Thus 
 reconstructed, the upland surface would rise gradually 
 from Ohio and western Kentucky to the east and southeast, 
 reaching the greatest height 
 near its eastern margin, 
 where the plateau de- 
 scends abruptly to 
 the Appalachian 
 valleys 
 At pres 
 
 e nt 
 the up- 
 land surface 
 is thoroughly dis- 
 sected by branching 
 valleys. The region 
 should therefore not be 
 described simply as a plateau ; 
 it is a dissected plateau, in an ad- 
 vanced or mature stage of geographi- 
 cal development. The altitude of the 
 iginal upland in West Virginia (roughly 
 or 3500 feet) has been great enough to 
 Fig. 92. -The permit the erosion of valleys 1000 or more 
 ^lateau^ feet deep ; hence some of the intervening 
 plateau remnants have strong relief, and fairly 
 deserve the popular name of " mountains " locally applied 
 to them. 
 
 Many resistant sandstone layers stand out in cliffs, 10 to 
 50 feet high, running in bands around the spurs of the great 
 
148 
 
 PHYSICAL GEOGRAPHY. 
 
 hills. The weak strata occupy the intervening slopes, covered 
 with a thin stony soil, and supporting a vast forest. The hills 
 and spurs are all very much alike, for they are developed 
 by similar streams on similar structures. Every side valley 
 resembles all its neighboring fellows ; all the members of a 
 local tribe of small streams cascade down over the same number 
 of fall-making strata on their descent to the larger rivers. 
 
 In contrast to the previous example, this district has nearly 
 everywhere lost its once continuous upland surface, and is 
 
 rig. 93. — Canyon of Kanawha River in Allegheny Plateau, West Virginia. 
 
 now transformed into a hill-and- valley country. There are 
 many small cliffs instead of a few great ones ; hence platforms 
 are seldom developed to notable breadth. A great part of the 
 surface consists of hillside slopes. Drainage is not delayed 
 on extensive uplands, as in young plateaus ; but at times of 
 rain or late winter thaws, water is quickly shed from the hills, 
 and the main streams rise rapidly in destructive floods. 
 
 The forests retard but do not prevent the wash of waste 
 from the steep slopes ; denudation is actively advancing, and 
 the load of waste delivered to the rivers is greater than in the 
 youth of the region, when the upland was less dissected. 
 
PLAINS AND PLATEAUS. 149 
 
 As a whole, the Allegheny plateau is so rugged that its 
 population is small, being generally found on isolated 
 farms upon the disconnected uplands, in villages and occa- 
 sional small cities in the valleys, or gathered about mines 
 or other industrial works. The isolated hilltop farmers 
 cannot afford to construct and maintain good hillside 
 roads; it is difficult to haul upland products down bad 
 roads to village markets or to railroad stations; and it is 
 doubly difficult to haul supplies up to the farms. Life on 
 the uplands is laborious. 
 
 The hillsides are generally too steep for cultivation ; if 
 cleared, the soil is rapidly washed away. Wild animals, 
 such as deer and bear, long ago exterminated from the lower 
 country on the east and west, still find refuge here ; small 
 game is abundant, and hunting is almost as much of an occu- 
 pation to the " mountaineers " as farming. 
 
 The forests supply lumber to the more thickly settled com- 
 munities on the east and west. The numerous coal seams 
 (vegetable deposits in ancient marshes, now members of the 
 great series of horizontal strata that build the plateau) are 
 well exposed in the deej)-cut valleys, and are now extensively 
 mined. Iron ore occurs in certain strata. Eock oil and 
 natural gas are found by boring deep wells. It is chiefly in 
 connection with the industries dependent on these important 
 products that a larger population is to-day attracted to this 
 rough country. In the earlier history of the United States 
 the dissected plateau was (excepting the North Carolina 
 mountains) the most formidable barrier between the Atlantic 
 coastal plain and the open prairies of the Ohio valley. 
 
 Intercourse and traffic are still so difficult in the districts 
 of stronger relief, away from the lines of travel, that the 
 people are slow in acquiring the ways of civilization. Family 
 feuds are still maintained among the " mountaineers " of West 
 Virginia and Kentucky. As the uplands decrease in height 
 
150 PHYSICAL GEOGRAPHY. 
 
 westward, and the valleys become more open toward the Ohio 
 river, population increases ; but Pittsburg is a city of excep- 
 tional size in this region. Its growth in early years was 
 favored by its position with reference to the lower Ohio valley, 
 and in later years by the great stores of mineral wealth in the 
 surrounding country. 
 
 Parts of the Cumberland table-land have broad uplands 
 holding villages, and traversed by high-level roads. A very 
 rugged part of the plateau is known as the Catskill mountains, 
 in eastern New York ; the higher parts are forested and unin- 
 habited. The plateau here descends by a bold escarpment to 
 the Hudson valley. 
 
 Old Plateaus. — Broad plains of gently rolling surface, 
 drained by streams in wide-open, flat-floored valleys, are 
 sometimes surmounted by flat-topped " table-mountains." 
 Neighboring tables are of nearly uniform height, each one 
 being capped by a resistant cliff-making rock layer and 
 flanked by a sloping talus ; they differ chiefly in area and 
 outline. In the western United States tables of moderate 
 height are often given the Spanish name mesa (= table ; 
 pronounced may-sa) ; while the smaller mesas are known 
 by the French name butte (= target or landmark ; pro- 
 nounced bewt). 
 
 Mesas and buttes of this kind are the scattered rem- 
 nants of strata that once spread far and wide over the 
 region, forming an extensive plateau. The original surface 
 of the plateau may have been much higher than the tops 
 of the mesas ; for the uppermost strata may now be com- 
 pletely swept away. The valleys have widened so greatly 
 that their floors occupy a great part of the surface. A 
 region of this kind represents an approach to the old age 
 of a plateau. 
 
PLAINS AND PLATEAUS. 
 
 151 
 
 The plains of western New Mexico are surmounted by 
 numerous remnant mesas. Settlement here is chiefly limited 
 to the lower lands. The isolated mesas and buttes, risinsr 
 several hundred feet over the plain, are generally unin- 
 habited ; thus the old age of a plateau reverses the conditions 
 of its youth, in which the uplands alone could be easily 
 occupied. 
 
 The mesas of an old plateau are not, like the canyons of 
 a young plateau, obstacles to travel ; for while can^^ons are 
 continuous for long distances and are everywhere difficult to 
 cross, mesas are discontinuous, and many broad passages are 
 opened among them. They are occasionally occupied as 
 natural citadels by barbarous tribes. 
 
 One of the most remarkable remnants of an old plateau 
 is the so-called Enchanted Mesa of western New Mexico. 
 
 Fig. 94. — The Enchanted Mesa, New Mexico. 
 
 It rises more than 400 feet above the surrounding plain, 
 and although no longer inhabited, it was once occupied 
 by a tribe of Indians, who found safety on its almost 
 inaccessible summit. 
 
 Other mesas in New Mexico and Arizona are still occupied 
 by small tribes of Indians, whose compact groups of houses 
 
152 PHYSICAL GEOGRAPHY. 
 
 on the upland cannot, at a little distance, be distinguished 
 from the rock walls of the cliffs. They cultivate small patches 
 of corn on the lower ground, but do not venture to build settle- 
 ments there for fear of attack from more warlike tribes. 
 
 In the interior of British Guiana gigantic remnants of an 
 old plateau rise over the surrounding lower country. Huge 
 mesas are rimmed round by almost inaccessible cliffs that 
 stand above long talus slopes. One of the highest is Eoraima, 
 whose broad table is more than 2000 feet above its base. It 
 is uninhabited, and until recently had never been ascended. 
 The natives of the forested wilderness around it believe that 
 the upland is occupied by spirits. 
 
 Old Plains. — It may be imagined that, at a very late 
 stage of development, even tlie mesas and buttes of an 
 old plateau may be worn away, the whole region being 
 then reduced to a gently rolling lowland, a worn-down 
 plain, or " plain of denudation." ^ Many examples of this 
 kind are known, but most of them have been again 
 elevated, and are now undergoing a new series of changes. 
 
 Central Russia is a nearly level region of moderate 
 altitude. It is one of the largest known examples of a 
 worn-down plain. At first sight it might be mistaken 
 for a young plain, so nearly even is the greater part of its 
 surface ; but a closer examination reveals many features 
 that do not correspond with those of young plains. The 
 subsoil rocks still lie in almost horizontal layers, but they 
 do not consist of loose sands and clays. Many of them 
 have a rather firm texture, showing that they have existed 
 long enough to have their particles bound together by the 
 very slow action of infiltering waters. 
 
 1 A lowland of this kind may be called a "peneplain," because it is 
 an " almost plain " surface. 
 
PLAINS AND PLATEAUS. 153 
 
 Besides this, the surface of the plain does not agree with 
 the surface of the uppermost rock layer, as is the case 
 in young plains, but bevels across the nearly horizontal 
 layers at a faint angle, so that in passing from place to 
 place, different layers are exposed, causing advantageous 
 changes of soil and slight variations of form. 
 
 A region of this kind must have once had a much higher 
 surface ; it may have been high enough to deserve the name 
 plateau. As time passed, rivers must have at first cut narrow 
 valleys across it. Then many branching valleys must have 
 been carved among numerous hills, like those of West Virginia 
 to-day. Finally, the valleys became broader and broader by the 
 wasting of their sides, and even the remnant mesas and buttes 
 were worn away. The plateau must have then been a broad 
 lowland, on whose surface the rivers could cut down no deeper. 
 
 Yet to-day the rivers of central Russia flow in rather narrow 
 valleys of moderate depth. Hence it must be supposed that, 
 after the ancient plateau was worn down to a low plain, the 
 whole region was broadly uplifted, and thus the rivers 
 regained the power of carving valleys. In the present series 
 of changes the dissection of the plain has not advanced much 
 further than that of the young plains of western Siberia. 
 Like these, the Russian plains have a vast extent north and 
 south. The difference of climate between the northern and 
 southern parts, due to the globular form of the earth, exerts 
 a great control on their fitness for occupation. They are 
 frozen and barren in the north, where they are overlapped by 
 younger plains that slope to the Arctic shore ; here the popu- 
 lation is scanty. They are dry and barren in the southeast, 
 where they are overlapped by the young plains of southwestern 
 Siberia ; here wandering tribes drive their flocks from place 
 to place. The middle and next southern parts are the most 
 fertile and here a great agricultural and commercial population 
 is gathered in villages and cities, 
 
164 PHYSICAL GEOGRAPHY. 
 
 The greater part of Missouri is a worn-down plain, now 
 uplifted and again dissected. It is an agricultural district, 
 the broad uplands generally being occupied in preference 
 to the narrow valleys. The strata of the region are 
 gently arched, and their highest part is known as the Ozark 
 
 Fig. 95. — The Ozark Plateau, Missouri. 
 
 plateau. The sky line of the uplands represents the low- 
 land plain that was formed at the close of the previous 
 series of geographical changes. The valleys have been 
 carved since the region was again uplifted. 
 
 c d 
 
 Fig. 96. — Section of the Ozark Plateau. 
 
 The weaker layers (d, d, Fig. 96) have been broadly etched 
 out beneath the uplifted level (p, p) of the region. The 
 uplands (c, c) resemble the upland belts of belted coastal 
 plains in having a steep front, made very ragged by the dis- 
 section of many short but rapid streams ; a broad top, much 
 
PLAINS AND PLATEAUS. 
 
 155 
 
 broken by narrow valleys ; and a long sloping back. The 
 height of the uplands over the lower lands is from 100 to 300 
 feet ; their height above sea level reaches 1500 or more feet. 
 
 A similar description might be given to a large part of the 
 basin of the Ohio river. It is a region of moderate relief, 
 with the advantages of good soil and sufficient rainfall. 
 Hardly more than a wilderness at the time of the Kevolution 
 (1776), it is now occupied by a great agricultural population, 
 dotted here and there with large and growing cities, and 
 crossed in all directions by railroads. 
 
 Broken Plateaus. — The plateaus of northern Arizona, of 
 which the Sheavwits already described is one, stand in a 
 curious relation to one another. East of the Sheavwits 
 
 Fig. 97. —Broken Plateaus. 
 
 comes the Uinkaret, presenting the same upland (diver- 
 sified by volcanic cones and lava flows), and exposing the 
 same succession of cliffs and talus slopes in the canyon 
 walls; but the Uinkaret stands about 1800 feet higher 
 
156 
 
 PHYSICAL GEOGRAPHY. 
 
 than the Sheavwits. The two are separated by a high and 
 ragged cliff or escarpment, known as Hurricane ledge, 
 facing westward. 
 
 Tracing this cliff to the canyon, it is found to stand on 
 the line of a great north and south fracture, which divides 
 the whole mass of strata into two blocks; the eastern 
 block (Uinkaret) being lifted nearly 2000 feet higher than 
 
 the western (Sheavwits). 
 This is easily proved by 
 the displacement of the 
 various cliff-making 
 strata in the canyon 
 wall. Several other 
 similar plateau blocks 
 are found in this region. 
 
 The western boundary 
 of the Sheavwits plateau 
 {A, Fig. 98) is another 
 ragged west-facing cliff, 
 2000 or 3000 feet high, 
 and so bold that it pro- 
 vokes rainfall from winds 
 that must rise as they 
 pass over it. Settlers on the lower arid land use the 
 streams that descend from the gigantic ravines in the cliff 
 face to irrigate their ranches. Great volumes of rock waste 
 have been washed down from this bold escarpment upon the 
 lower land, to which the name of " Grand Wash " is therefore 
 given ; and the ragged bluffs of the escarpment are called the 
 Grand Wash cliffs. The Colorado river, coming out from the 
 canyon in the Sheavwits plateau to the lower land on the west, 
 follows a more ordinary valley of moderate depth and open 
 slope ; some of the same rock layers that cap the plateau are 
 
 Fig. 98. —Diagram of Blocked Plateaus. 
 
PLAINS AND PLATEAUS. 
 
 157 
 
 here seen low down along the river bank. Where the river 
 cuts the base of the Grand Wash cliffs, the fracture by which 
 the upper and lower blocks are displaced may be discovered 
 on the valley sides. 
 
 East of the Uinkaret (JB, Fig. 98) come several other 
 plateau blocks. The barren surface and varied form and 
 colors of the successive strata make the great fractures 
 between the several blocks plainly apparent to the observer 
 who looks from the brink of the canyon to its opposite wall. 
 The Kaibab (D) is so high (8000-9000 feet) that, unlike the 
 arid and barren plateaus on each side, its climate is moist ; 
 it has forests, park-like groves, and grassy glades well stocked 
 with game. The, canyon here has its greatest depth, cutting 
 down 6000 feet through the whole series of stratified rocks 
 into the foundation rocks of buried old-land at the bottom. 
 
 The ragged cliffs, by which the ascent is made from one 
 plateau to its highest neighbor, are features of a new 
 
 Fig. 99. — Hurricane Ledge — a Fault Cliff. 
 
 class. They are to-day undergoing active weathering and 
 wasting. In the past they were less ragged than now. 
 The fractures between the blocks are commonly known 
 
158 PHYSICAL GEOGRAPHY. 
 
 under the name of faults ; hence the term fault cliffs may 
 here be used. It is probable that the displacement or 
 faulting was gradual, and that the cliffs were somewhat 
 weathered even during the time of faulting. To-day they 
 may be called dissected fault cliffs. 
 
 It is truly remarkable how little attention the streams of 
 this region pay to the profound fractures by which the plateau 
 blocks are divided. The Grand Canyon, the most fissure- 
 like of all great river valleys, pursues its course entirely 
 regardless of the fissures that run across it. On the surface 
 of the plateaus the fissures are evident in the fault cliffs, now 
 somewhat weathered back from their original faces ; but they 
 are not followed by canyons. 
 
 The origin of the irresistible forces by which the plateau 
 blocks have been broken apart and uplifted is little under- 
 stood. It is undeniable that movements of uplift and dis- 
 placement have really occurred, producing great geographical 
 features in the wonderful plateau country of Arizona and 
 Utah, but the cause of the movements is an unsolved prob- 
 lem, worthy of attention from the advanced student of 
 geology. 
 
 The great plateau blocks of Arizona are set apart by their 
 generally dry climate, great altitude, and deep dissection from 
 the easily habitable parts of the world. Where their surface 
 is most rugged and inaccessible, unsubdued tribes of Indians 
 still preserve their savage ways, living in a most- primitive 
 fashion on isolated plateaus surrounded and trenched by 
 branching canyons. Travelling over the less dissected plateaus 
 is feasible with a proper outfit of horses and provisions and 
 with a good guide ; and no part of the world would better 
 repay a visit by a lover of the marvellous in nature than the 
 lofty Kaibab, where it is trenched by the mile-deep canyon. 
 
CHAPTER VII. 
 
 MOUNTAINS. 
 
 The Inspiration of Mountain Scenery. — Most of the peo- 
 ple of the world live on lands of moderate relief, where an 
 
 Fig 100 —The Himalaya Moontalna 
 
 abundant soil supplies the needs of agriculture, and where 
 travel and traffic are little obstructed. Rugged regions 
 repel rather than attract inhabitants. The people who 
 
160 PHYSICAL GEOGRAPHY. 
 
 live on lowlands liave, until modern times, usually looked 
 upon high mountains as places of danger. It has been 
 imagined that they were occupied by evil spirits, and that 
 it must be perilous to cross their high passes or to climb 
 their snow-clad peaks. Uncivilized people living in the 
 valleys among mountains seldom ascend higher than to 
 the pastures on the shoulders of the ridges, or to the low- 
 est notches by which the ranges are broken. But in the 
 eighteenth and nineteenth centuries a better understand- 
 ing of nature among civilized nations has led explorers to 
 press far into the deep valleys of mountains and to mount 
 their lofty peaks, until now a passion for mountain climb- 
 ing has arisen and many thousand travellers go every 
 summer into the most mountainous country that they can 
 reach, simply for the enjoyment of its scenery. 
 
 To one who has always lived in a low country, it is a 
 novel experience to climb a bold mountain slope and rise 
 high above the lower ground. A wide prospect is spread 
 out beneath and far away, where the hills and valleys, the 
 forests and fields, the roads and streams are displayed as 
 if on a map. The peaks above inspire the traveller with 
 an ambition to reach their highest point and see the 
 country beyond, with nothing but the sk}^ above him. A 
 new sensation is aroused by the grandeur of the view from 
 the summits. The massive vigor of the peaks and ridges 
 excites enthusiasm, and the least imaginative observer can 
 hardly fail to muse on the marvellous processes of nature 
 that have brought such forms into being. The mountain 
 climber who enters with sympathy into the life of the 
 mountains, and who looks upon them as they, had they 
 but eyes, might look on each other, gains a new under- 
 
MOUNTAINS. 
 
 161 
 
 standing of the world he lives in, a better and broader 
 understanding than he had before. He may then appre- 
 ciate the feeling of a guide in the Alps who once said to 
 a traveller : "■ I like to be on a mountain ; one has no evil 
 thoughts there." 
 
 The Life Histoey of Mountains. 
 
 Block Mountains: Young Stage. — In southern Oregon 
 and the adjoining parts of California and Nevada there 
 are many long narrow mountain ridges, extending about 
 
 Fig. 101. — Block Mountains. 
 
 north and south. Each ridge is a few miles wide, 10 to 
 40 or more miles long, and 1000 or more feet high. 
 The ridges are steep or cliff-like on one side, of gentler 
 slope on the other, and are separated by flat trough-like 
 depressions of varying breadth and depth. 
 
 Each ridge consists of thick layers of rock, the surface 
 of the uppermost layer forming the back slope of the 
 ridge, while the cliff face breaks across the layers. The 
 rock layers are similar in all the rock faces, though the 
 ridges vary greatly in size. A general view of the country 
 
162 
 
 PHYSICAL GEOGRAPHY. 
 
 shows that the entire region was once a plain, but that it 
 is now broken into long narrow blocks, and that the blocks 
 are tilted one way and the other, so that their uplifted 
 edges form the mountain crests. 
 
 It is difficult to account for forces sufficient to break the 
 earth's solid crust in this way, but, as in the plateau blocks, 
 there can be no question that such forces have been at work, 
 
 and th at they have exerted 
 a great influence on geo- 
 graphical conditions. 
 
 Some of the ridges re- 
 tain the form of the tilted 
 blocks hardly changed by 
 weathering. Their back 
 slopes are smooth; their 
 cliffs have little talus at 
 the base. Others have 
 shallow gullies worn down 
 the back, while the cliffs 
 are indented by ravines, 
 and every ravine has a fan-like deposit of rock waste spread 
 out beneath it; between the fans the cliffs have a distinct 
 talus slope at their base. 
 
 On Satas ridge in southern Washington (^, Fig. 130), great 
 bodies of rock have fallen from the cliffs in huge landslides, 
 so steep was the face of the uplifted block. In one case a 
 landslide slipped down about 1000 feet from a cliff 2500 
 feet high, leaving a scar on the cliff half a mile long, and 
 plowing its way out on the plain below for nearly a mile. 
 The fallen mass is much broken, having a very irregular sur- 
 face. Around its margin is a rude semicircle of hills 200 
 feet high, consisting of the material of the plain pushed up 
 ahead of the slide. Although little weathered, the Indians 
 thereabouts have no tradition of its fall. 
 
 Fig. 102. —Mountains of Southern Oregon. 
 
MOUNTAINS. 163 
 
 The tilted blocks of Oregon are, on the whole, so little 
 worn that they must have been broken and tilted recently in 
 the earth's history. As some of them are more gullied and 
 ravined than others, the different blocks must have been 
 broken at different times. Some of the fans and talus slopes 
 of rock waste are slightly broken along the fracture lines at 
 the base of the cliffs ; hence the breaking and tilting of the 
 blocks must liave been progressive, and not all at once. The 
 fractures dividing the blocks must be deep, for hot springs 
 rise along their lines. 
 
 Earthquakes are not infrequent in this region ; hence it is 
 believed that the displacements are still in progress from 
 time to time ; a movement of even a few inches would suffice 
 to cause earth tremors, while a sudden start of a foot or more 
 would produce a violent and destructive shock for many miles 
 around. There is no sign that volcanic action has any con- 
 nection with the fractures and earthquakes of this region. 
 
 Here we have to do with a group of young mountains, 
 whose broken attitude was given very lately in the earth's 
 history. The ridges have a massive shape characteristic 
 of unworn forms, not yet ornamented by the varied details 
 of weathering and carving that they will gain when more 
 dissected. They are less beautiful than mountains of 
 greater height and more varied features, but they are of 
 great interest as examples of simple geographical forms. 
 Nowhere else in the world have mountains at once so 
 large and so young been discovered. 
 
 The drainage of this region is very simple, for the 
 streams follow the slopes produced by the tilting of 
 the mountain blocks. The smaller streams flow down the 
 slopes of the ridges. The larger streams flow along the 
 troughs in the direction of their slant to the deejjest 
 depressions, and there form shallow lakes and marshes. 
 
164 PHYSICAL GEOGRAPHY. 
 
 The finer waste from the ridges is spread evenly over the 
 lower parts of the troughs, concealing their rocky floor. 
 
 Like the rivers that are extended across young coastal 
 plains, the streams of the young ridges in Oregon flow in one 
 direction or another in consequence of the slopes given to the 
 land surface that they drain. 
 
 Certain features of the region depend on its arid climate. 
 The rainfall is light (15 inches or less a year), for the 
 lofty Cascade range on the west takes most of the moisture 
 from the Pacific winds. Few of the lakes are filled to over- 
 flowing ; they discharge their water supply by evaporation 
 into the dry air. Most of the lakes are therefore saline, and 
 the plains of fine waste about them are barren. 
 
 In dry seasons the lakes shrink ; some of them disappear, 
 leaving smooth floors of sun-baked clay. The bottom of the 
 troughs elsewhere and the lower slopes of the ridges are 
 clothed with bunch grass and sagebrush; the ridge slopes, 
 receiving more rainfall than the lower lands, support scattered 
 cedars, and the higher crests bear forests of pine and spruce. 
 Had the ridges not been uplifted, the trees that now grow on 
 them could not exist in this arid region. 
 
 Although the ridges are of moderate height, they repel the 
 few settlers in the region, whose ranches are all found in 
 the troughs. The thin grass supports herds of cattle, and 
 the streams sufiice for a little irrigation. Thus even in these 
 low young ridges the effect of mountains on the climate and 
 on the location of settlements is well shown. These effects 
 will be found to be much more striking in mountains of 
 greater height. 
 
 Dissected Block Mountains. — In Nevada and the adjoin- 
 ing parts of California and Utah there are many north- 
 and-south mountain ranges, adjoined by gravelly plains 
 that slope gently to flat troughs between the ranges. The 
 ranges are from 20 to 80 miles long, and from 5 to 20 
 
MOUNTAINS. 
 
 165 
 
 miles wide. Their summits rise from 5000 to 7000 feet 
 above the plains. They are generally steeper on one side 
 than on the other ; their crests are notched and uneven ; 
 
 Fig. 103. — A Dissected Mountain Range, TJtah. 
 
 their slopes are diversified by well-carved spurs between 
 deep valleys. Thus they possess much of the variety of 
 form commonly associated with mountains. 
 
 As compared with the ridges of southern Oregon, these 
 ranges are larger and more dissected ; but the two agree in 
 having a short and relatively abrupt slope on one side of the 
 crest line, and a long gentler slope on the other side. 
 
 The ranges of Nevada, like the ridges of Oregon, seem 
 to have been formed by the uplifting and tilting of long 
 narrow blocks, into which the region had been divided by 
 profound fractures ; but in Nevada the blocks must have 
 been larger and the displacements greater ; and thie break- 
 
166 
 
 PHYSICAL GEOGRAPHY. 
 
 ing and tilting must have begun earlier than in Oregon, 
 for the work of dissection is here much further advanced. 
 The ranges of Nevada are thoroughly or maturely dissected. 
 Yet, as in Oregon, earthquakes and broken fans of rock 
 waste give assurance that the mountains are still growing. 
 
 The blocks are now so deeply carved, and their outlines 
 are so irregular, that their original block form is hardly 
 recognizable. With this change, the mountains have become 
 much more beautiful, just as a carved statue is more beautiful 
 than a rough block of marble. The rock waste, worn from 
 
 Fig. 104. — Fractured Slopes of Kock Waste at Base of Mountain Range, Nevada. 
 
 the valleys in the mountains, forms extensive sloping gravel 
 plains in the troughs, accumulating to so great a depth as to 
 rise on the flanks of the mountains and thus diminish their 
 relief. 
 
MOUNTAINS. 167 
 
 The strong ranges of Nevada exhibit more distinctly than 
 the smaller ridges of Oregon the lower temperature, with 
 greater cloudiness and rainfall, that prevails on mountains 
 as compared with the plains between them. The rainfall in 
 the troughs is light, but storm clouds gather round the peaks 
 while the sun still shines on the plains. When the clouds 
 dissolve, the mountains have been refreshed by rain or 
 whitened with snow, while the plains may be as dry as 
 before. 
 
 Streams flowing from the mountains often wither away on 
 the plains. Settlements in Nevada are therefore generally 
 limited to a belt around the mountain base, where the streams 
 may irrigate fields. Some of the ranges contain valuable 
 ores ; mining towns have sprung up in their valleys. 
 
 Old Block Mountains. — In southeastern California there 
 are belts of rocky hills rising to moderate height over long 
 slopes of gravelly waste, beneath which a rocky floor is some- 
 times exposed in gullies. These hills are taken to be the 
 dwindling remnants of mountain ranges upraised so long ago 
 that now they are worn down to low relief. Their youth, in 
 uncarved blocks, is long past. Even their maturity, varied 
 by many ridges, spurs, and valleys, is remote. They are old 
 mountains, reduced to mere hills under the patient attack of 
 the weather. 
 
 Folded Mountains : Young Stage. — The Jura mountains, 
 lying along the border of France and Switzerland, consist 
 of a number of parallel arch-like ranges and trough-like 
 valleys trending about northeast and southwest. Each 
 range consists of a series of rock layers bent upwards; 
 each trough is underlaid by the same series of layers bent 
 downwards. Some of the uppermost layers have been 
 weathered off from the crest of the arches, while the edges 
 of the harder layers remain in flanking ridges. Waste 
 
168 
 
 PHYSICAL GEOGRAPHY. 
 
 from the arches has accumulated in the troughs here and 
 there, flooring them over with gravel and sand. 
 
 The rock layers of these mountains contain marine fossils ; 
 they must originally have been horizontal strata on the floor of 
 an ancient sea. Since then they have been crushed into their 
 arch-and-trough structure by a powerful side pressure. 
 
 The drainage of the Jura mountains is for the most 
 part like that of the Oregon ridges in following the slopes 
 of the deformed surface. Short streams run down the 
 
 Fig. 105. —Diagram of the Jura, a Folded Mountain Range. 
 
 sides of the arches, cutting ravines on the slopes, as shown 
 in the unshaded foreground of Fig. 105. Larger streams 
 gather on the trough floors, and escape at one end or the 
 other as opportunity offers. 
 
 Here and there a stream cuts across an arch, wearing a 
 deep gorge from one trough valley to the next, and exhibiting 
 
MOUNTAINS. 169 
 
 the arched structure, as in the middle ridge of Fig. 105. The 
 origin of these crosswise or transverse streams is not so 
 simple as that of the others. Some of the cross gorges are 
 cut where the arches are least uplifted, as if a sag in the crest 
 of the arch had located the transverse stream. In other cases 
 it seems as if the gorge had been cut down by its stream 
 about as fast as the arch was uplifted, thus indicating a slow 
 growth of the mountains. 
 
 As in all mountains of distinct relief, the form of the sur- 
 face exercises a strong control over the distribution, occupa- 
 tion, and movement of the population. The valley floors are 
 well settled ; villages often lie near the mouth of a transverse 
 gorge. Eoads are generally limited to the lengthwise and 
 crosswise valleys. By-ways and footpaths lead to the upland 
 fields and pastures. Little villages are sometimes found on 
 the tops of the broader arches. The steeper slopes are 
 generally forested. 
 
 ISTowhere else in the world have there been discovered 
 arches and troughs of so simple a pattern and so young a 
 stage as those of the Jura. The Oregon ridges and the Jura 
 folds are, as it were, elementary examples of mountain forms, 
 provided by nature for the better understanding of the com- 
 plicated examples of structure and form in greater mountain 
 ranges. 
 
 Domed Mountains. — The Black Hills of South Dakota 
 show a thick series of rock layers that have received a 
 dome-like structure by the upheaval of their foundation. 
 The dome is of oval outline, 100 miles north and south 
 by 50 miles east and west; in area about equal to that 
 of Connecticut. A great part of the covering layers has 
 been weathered and worn away during and after the time 
 of upheaval, and to-day the foundation rocks are exposed, 
 especially in the eastern half of the dome. If built up 
 
170 
 
 PHYSICAL GEOGRAPHY. 
 
 again, the height of the dome over the surrounding plains 
 would be about 6000 feet; to-day the highest summits are 
 only 2000 or 3000 feet above the plains, or about 7000 
 feet above sea level. 
 
 The edges of the more resistant sandstone layers, whose 
 higher part has been worn off from the dome, form ridges 
 that rim around the margin of the Hills. Many streams 
 have cut deep valleys leading outward in all directions 
 
 Fig. 106. — Diagram of the Black Hills. 
 
 from the central part of the dome, as if they had been 
 guided by the original slope of the uplifted surface. 
 They cut notches or water gaps in the rimming ridges. 
 
 The rolling treeless plains surrounding the Black Hills 
 have light rainfall and scanty grass. They are occupied, if 
 at all, by large ranches where cattle range freely, reaching a 
 stream once or twice a day. Approaching the Hills, the rim- 
 ming ridges rise around them too high and steep for easy 
 occupation. The valleys define lines of travel; the v/ater 
 gaps in the outer ridge are of especial importance as gate- 
 ways to the Hills. Next inside of the chief rimming ridge is 
 a valley that has been worn down on weak layers of red clays 
 
MOUNTAINS. 
 
 171 
 
 that here and there give a bright color to its soil ; hence its 
 name, the Eed valley. It is so continuous around the Hills 
 that the Indians called it the '' race course." 
 
 The central part of the dome still rises high enough to 
 compel an increase of rainfall from the passing winds. The 
 Hills are therefore clothed with dark forests (hence the name 
 Black Hills) and support an active lumber industry. 
 
 
 
 i 
 
 
 Fig. 107. — Seadwood, a Mining Town in the Black Hills. 
 
 The deeper valleys dissect even the foundation rocks, which 
 (as is often the case in ancient rocks uncovered from a long 
 burial) contain valuable deposits of gold and silver. Here 
 mining flourishes and settlements grow, crowded in the narrow 
 valleys. The mines need machine shops and smelting works, 
 and the industries thus created demand means of transporta- 
 tion. Two railroads have therefore been built from the central 
 states across the open country into the Black Hills ; their 
 trains resemble steamships crossing the sea-like plains to ports 
 in the island-like hills. 
 
172 
 
 PHYSICAL GEOGRAPHY. 
 
 Lofty Mountains. — Lofty mountain ranges, like certain 
 parts of the Rocky mountains, but better represented by 
 the Alps, the Caucasus, and the Himalaya, possess a great 
 
 Fig. 108. — Peaka of the Central Alps. 
 
 complexity of structure and exhibit a remarkable variety 
 of peaks, ridges, ravines, and valleys. Their higher central 
 peaks usually consist of resistant granite-like rocks, sur- 
 rounded by slanting layers of bedded rocks that rise in 
 great ridges. 
 
 These two parts once had a simple relation like that of 
 "foundation " and "cover," already seen in several examples ; 
 but now both the foundation rocks and the covering strata are 
 greatly deformed and dissected, as if repeatedly tilted in blocks, 
 uplifted in domes, and crushed in folds, and as if for a long 
 time vigorously attacked by weather and streams. 
 
 The majestic forms of lofty mountains usually depend 
 as much on their deep dissection by great valleys as on 
 their lofty uplift. Unlike the simple tilted blocks of 
 
MOUNTAINS. 
 
 173 
 
 Oregon, or the orderly folds of the Jura, the greater 
 ranges preserve little indication of their original form. 
 
 Lofty mountain ranges have a greater length than breadth. 
 They extend in a general way parallel to the trend of their 
 tilted blocks and folds, as if they represented a belt of 
 country where the crust of the earth had been crushed or 
 upheaved in escaping from enormous pressures from one side 
 or from beneath ; but the nature of the forces which produce 
 mountains is not fully understood. One of the most ingenious 
 and successful theories accounts for many ranges as great 
 disorderly folds formed in the outer crust of the earth, which 
 is thought to wrinkle here and there as it very gradually 
 settles down on the slowly cooling and contracting interior. 
 
 The discovery of marine fossils in the bedded rocks of high 
 Alpine ridges toward the close of the eighteenth century was 
 
 Fig. 109. — An Alpine Ridge of Slanting Layers. 
 
 received with great astonishment by the scientific men of the 
 time. The occurrence of fossils in so elevated a position was 
 one of the first generally accepted proofs of the changes that 
 
174 PHYSICAL GEOGRAPHY. 
 
 have gone on in the past, by which the present form of the 
 earth's surface has been fashioned. But not until the nine- 
 teenth century had well advanced was it generally under- 
 stood how much more the form of lofty mountains depends 
 on processes of land sculpture than on forces of uplift. 
 
 Peaks and Ridges. — The highest peaks and ridges of 
 lofty mountains generally consist of the most resistant 
 rocks. Their height is due in part to the great uplift the 
 whole range has suffered, and in part to their success in 
 resisting the attack of the weather, under which the 
 weaker rocks have greatly wasted away. The waste that 
 is shed from the peaks and higher ridges is quickly swept 
 down into the valleys, usually leaving the loftiest summits 
 bare and sharp. The spurs of the ridges are notched by 
 steep ravines, and deep valleys are worn between them. 
 Their varied form is chiefly due to elaborate carving. 
 
 The bare rocky peaks and ridges, rising into the cold 
 upper atmosphere, far above the limits of vegetation, are 
 silent deserts. The stillness is broken only by the rush 
 of storm winds and the roar of rockfalls and snowslides. 
 Not less barren are the snow fields and the talus slopes on 
 the higher mountain flanks, and the slanting reservoirs 
 . of ice and snow in the upper valley heads, from which ice 
 streams or glaciers slowly creep down to the lower valleys. 
 The lower slopes are generally forested. 
 
 Many summits in the Alps are so sharp that they are 
 called " needles " or ''horns." They rise as almost inacces- 
 sible peaks between the gnawing valley heads. Mt. Blanc, 
 the highest mountain of the range (nearly 16,000 feet) is of 
 dome-like form with a heavy snowcap, not yet sufficiently 
 dissected by valleys to develop sharp peaks. 
 
MOUNTAINS. 175 
 
 The Selkirk range of the Eocky mountains in Canada has 
 steep and bare rocky summits surmounting the long waste- 
 covered slopes that descend into the valleys. Having an 
 abundant snowfall, the range bears extensive snow fields and 
 glaciers. In the Rocky mountain ranges of Colorado the 
 snowfall is less plentiful, snow fields are scarce, and glaciers 
 are wanting. Long slopes of creeping waste cover the moun- 
 tain flanks far up towards the summits ; craggy peaks of sharp 
 form are less common than in the Selkirks or the Alps. 
 
 Climate of Mountains. — On extensive plains the cli- 
 mate — especially the temperature and rainfall — changes 
 very slowly from place to place, being nearly uniform for 
 hundreds of miles together. On the average, one must 
 travel from 30 to 60 miles poleward to find a difference 
 of 1° in mean annual temperature. The same difference 
 is found on niountains by an ascent of only 300 feet. 
 
 Broad plains may have only a scanty rainfall over 
 hundreds of miles together. On lofty mountains the rain- 
 fall rapidly increases with elevation. Not only because 
 they are high, but also because they receive much rain 
 and snow, high mountains are usually the sources of large 
 rivers. 
 
 Similarity of form and climate over broad plains makes 
 the conditions of life nearly uniform over great areas. In 
 mountains diversity of form and climate is found within 
 small distances, and strong contrasts in the conditions of life 
 are crowded close together. 
 
 On account of the lower temperature and the heavier 
 rainfall and snowfall of high mountains, their ■ animals and 
 plants are unlike those living on the surrounding lowlands. 
 On ascending the mountain flanks, hardy cone-bearing trees 
 succeed those needing a milder climate. As the limit of 
 
176 PHYSICAL GEOGRAPHY. 
 
 tree growth or " tree line " is approached, only stunted and 
 deformed trees survive. Then comes a belt in which the 
 slopes bear grass and Alpine flowers. (Alpine is used to 
 refer not only to the European Alps, but also to the animals 
 and plants of any lofty mountain.) Following this is the 
 snow line, above which some of the snow of one winter lasts 
 over the following summer, excluding plant life. The height 
 of the snow line is greatest in the torrid zone (18,000 to 
 20,000 feet) and decreases towards both poles, reaching sea 
 level in the frigid zones. It is remarkable that many plants 
 found near the snow line on mountains in the warmer zones 
 are also found near sea level in the frigid zone. 
 
 Mountains as Barriers. — High mountains serve as bar- 
 riers, separating the climates and the populations of their 
 opposite sides. The eastern slope of the equatorial Andes 
 has a moist climate because the damp winds from the 
 Atlantic, ascending and cooling, give forth a heavy rain- 
 fall there ; the western slope has a dry climate because the 
 same winds, descending and warming, not only give forth 
 no more rain, but eagerly take up whatever moistui-e they 
 find on the way. The eastern slope is densely forested ; 
 the western slope is for the greater part a desert, except 
 in vallej^s watered b}^ streams. 
 
 Moist winds from the Pacific give a plentiful rainfall 
 on the westward or windward slopes of the Sierra Nevada 
 and the Rocky mountains of the United States. The same 
 winds, descending on the eastern or leeward slopes, become 
 in winter unseasonably warm and dry (see Appendix H), 
 evaporating the light snow of the plains, and laying bare the 
 dry bunches of grass, greatly to the advantage of the cattle 
 feeding there. The dry wind is called the Chinook. A simi- 
 lar wind occurs in the northern valleys of Switzerland, where 
 it is called the Foehn. 
 
MOUNTAINS. 177 
 
 The great populations of India and China, representing 
 different races, are s,eparated by the Himalaya and other 
 ranges in southern Asia. They are thus so well held apart 
 that neither one has had an important influence on the other. 
 Lofty mountain ranges thus rank with the oceans in separat- 
 ing the inhabitants of the lands. 
 
 When low countries on opposite sides of a high range are 
 occupied by different peoples, the mountains commonly serve 
 as a natural boundary between the two countries. The range 
 as a whole may serve as a rough boundary between uncivi- 
 lized nations ; but between civilized nations the crest line 
 dividing the rivers of the opposite slopes is often accepted as 
 a more precise boundary, as in the Pyrenees between France 
 and Spain, where the river divide is generally adopted as the 
 national divide. 
 
 When the river divide departs from the main range that 
 it was supposed to follow before the mountains were explored, 
 the boundary question may give rise to dispute, as recently 
 between Argentina and Chile, where a number of Pacific rivers 
 rise on the pampas of Patagonia, and cut through the Andes in 
 deep gorges. 
 
 The difficulty of crossing lofty ranges gives great im- 
 portance to the notches or passes in their central ridges, 
 through which travel and traffic may go with less effort 
 than over their peaks. The heavy snows of the winter 
 may close the passes for several months. In earlier cen- 
 turies, when the passes were traversed only by paths, 
 houses of refuge were often maintained on the summit by 
 monks, as on the famous pass of St. Bernard in the Alps. 
 
 It is chiefly within the last hundred years that well-planned 
 roads have been constructed over the chief passes of various 
 Alpine ridges. The roads enter the mountains along the 
 larger valleys, and then zigzag up the steeper slopes. They 
 
178 
 
 PHYSICAL GEOGBAPHY 
 
 are carefully laid out so as not to exceed a certain moderate 
 grade, about five feet in a hundred. Certain passes are now 
 crossed even by railroads, the ascent from the valleys being 
 most ingeniously made by curves and ''loops." Sometimes 
 the last part of the ascent is avoided by tunnelling the ridge 
 under the pass, it being cheaper in the long run to bore 
 throusfh than to climb hiarher. 
 
 Avalanches. — The heavy snowfall of winter often over- 
 loads the snow banks on the higher slopes, and great 
 
 masses of snow 
 slide down to 
 lower levels. 
 Summer melt- 
 ing and rainfall 
 also cause slides 
 or avalanches 
 (aval : to the val- 
 ley). Sometimes 
 the snow mass 
 glides along the 
 sloping surface 
 
 Fig. 110. —An Avalanche Path, Selkirk Range, Canada. 
 
 at a moderate speed. Sometimes it leaps from cliffs, and 
 falls with a terrible velocity to the valleys below ; a vio- 
 lent blast of air bursts outward from beneath, overturning 
 trees hundreds of feet beyond the reach of the snow. 
 
 Certain villages in Alpine valleys carefully preserve a 
 patch of forest on the slope above them as a protection from 
 avalanches. Highways and railways on steep mountain 
 slopes must here and there be covered in by long snow 
 sheds, over which the snow may slide without blocking or 
 injuring the road. 
 
MOUNTAINS. 
 
 179 
 
 Heavy masses of ice are occasionally detached from gla- 
 ciers that end on steep slopes, forming " ice falls." These 
 are even more destructive than avalanches of snow. An ice 
 fall, over 5,000,000 cubic yards in volume, broke from a 
 glacier on the slope of the Altels (Fig. Ill ; see Fig. 109, 
 from a photograph taken before the fall) in the Alps in Sep- 
 
 rig. 111. —Path of an Ice Fall in the Alps. 
 
 tember, 1895. It ran down a steep slope two and a half 
 miles long, gathered about 1,300,000 cubic yards of rock 
 waste on the way, and then rushed across the valley floor, 
 dashing far up the opposite slope and falling back again, like 
 a wave from a cliff. A bench on the path of the sliding mass 
 caused it to leap forward, clear of the ground ; then falling, 
 the air beneath was violently driven away, blowing out frag- 
 ments of ice and rock and breaking down trees hundreds of 
 yards distant. 
 
 Valleys among Mountains. — One of the strongest char- 
 acteristics of thoroughly dissected, lofty mountains is the 
 activity with which the rock waste is weathered from the 
 peaks and cliffs, moved down the steep slopes, swept by 
 
180 
 
 PHYSICAL GEOGRAPHY. 
 
 the streams along the larger valleys, and washed out upon 
 or across the adjoining lowlands. The waste seems every- 
 where to be streaming (as the long-lived mountains might 
 say) down from the peaks and ridges. The elaborate 
 carving of the mountains has been accomplished by the 
 long duration of these active processes for ages past. 
 
 The greatest work of erosion is seen in the excava- 
 tion of the chief valleys and their innumerable branches. 
 Unlike young mountains, where the valleys generally 
 follow the troughs between the uplifted blocks or arches, 
 lofty mountains are dissected by valleys that often bear 
 little relation to the original depressions among the uplifts. 
 Just as the peaks and ridges result from the survival of 
 the more resistant rocks, so the valleys in thoroughly dis- 
 sected mountains generally result from wearing out the 
 weaker layers, which have been thoroughly sought for by 
 the destructive processes. 
 
 Some of the valleys among high mountain ranges may be 
 cut down deep beneath the troughs by which the streams 
 
 were originally lo- 
 cated. It is not 
 rare in greatly up- 
 lifted and deeply 
 dissected moun- 
 tains to find high 
 ridges bearing the 
 remnant of a down- 
 folded hard layer ; 
 the rock arches on 
 each side being now 
 worn down to deep valleys that have been excavated on 
 weak under-lay ers, as in Fig. 112. Thus an original valley 
 
 
 t- 
 
 
 Fig. 112. — A Mountain of Down-Folded Layers. 
 
MOUNTAINS. 181 
 
 floor has come to be a mountain ridge, while the adjoining 
 a.rches have been reduced to deep valleys. The importance 
 of erosion as a means of producing land forms and the great 
 depth to which valleys have been carved are seldom more 
 emphatically taught. 
 
 Valley floors among lofty mountains must be at a con- 
 siderable height above sea level, especially near their 
 heads; for as long as a great volume of waste is swept 
 from the upper slopes and washed by torrents down the 
 ravines and side valleys, even a good-sized river in a main 
 valley cannot cut its channel down to a faint slope, close 
 to sea level. The valley line must have a rather rapid 
 descent, 50 to 100 feet to a mile, in order to give the 
 river a velocity that will enable it to carry away the waste 
 that is washed into it. 
 
 In deep and narrow valleys the side slopes are sometimes 
 cut so steep that great rock masses may be detached from 
 the walls and slip to the bottom, forming landslides. This 
 is particularly common where the strata in the valley walls 
 slant into the valley. 
 
 In September, 1893, a great landslide occurred in the deep 
 valley of one of the upper branches of the G-anges in the 
 Himalaya, 150 miles above the city of Hardwar, where the 
 river emerges on the plains. In three days 800,000,000 tons 
 of rock fell with deafening noise, darkening the air with 
 dust, leaving a great bare cavity with steep walls several 
 thousand feet high to mark its source, and building a dam 
 nearly 1000 feet deep across the narrow valley floor. A lake 
 gradually formed on the up-stream side of the dam, and grew 
 to be four miles long before it overflowed about a year after 
 the slide. 
 
 In the mean time the danger that the lake might burst out 
 in a great flood being perceived by the British engineers in 
 
182 
 
 PHYSICAL GEOGRAPHY. 
 
 charge of the public works of India, the bridges in the lower 
 valley were removed ; safety marks were set up on the val- 
 ley sides, 100 or 200 feet above the ordinary river level, 
 indicating the height above which the flood would probably 
 not rise ; and a telegraph line was constructed from the dam 
 to Hardwar, to give prompt warning of the outburst. 
 
 Fig. 113. — A Landslide in the Himalaya. 
 
 The flood occurred at midnight, August 26-27, 1894. In 
 four hours about 400,000,000 cubic yards of water were dis- 
 charged, cutting down the dam nearly 400 feet, flooding the 
 valley to a depth of from 100 to 170 feet, and rushing forward 
 with a velocity of 20 miles an hour. Many miles of valley 
 road were washed away. Every vestige of habitation was 
 destroyed in villages along the Ganges above Hardwar. But 
 so well was the notice of danger given that only one man lost 
 
MOUNTAINS. 183 
 
 his life, and that because he would not heed the warning. 
 Under a less intelligent control, thousands of people must 
 have perished in such a catastrophe. 
 
 Lengthwise and Crossv/ise Valleys. — When a river has 
 cut down its valley floor to as moderate a slope as 
 the load of waste that it has to carry along will allow, 
 it may still wear away its banks, first on one side, then on 
 the other. Thus in the course of time the river broadens 
 the valley floor. This is es'^ecially true in a valley that is 
 worn down along a belt of weak rocks parallel to the gen- 
 eral trend of a mountain range ; for these rocks weather 
 and wash away at a comparatively rapid rate. 
 
 The crosswise valleys, by which the rivers of the long 
 inner valleys find outlets through enclosing ridges, are 
 often narrow and steep-walled gorges ; for the ridgemak- 
 ing rocks are resistant and weather slowly. The floor 
 of a crosswise or transverse valley may be hardly wider 
 than its stream; the walls rise steep from the water's 
 edge, leaving no room for a road or path on either side. 
 
 It is chiefly in the broader lengthwise valleys that moun- 
 tain peoples dwell. When the outlet valleys are narrow 
 gorges, the outer world has for centuries been reached only 
 by passes over the enclosing ridges ; but modern engineering 
 skill has sufficed to build and cut roads and railroads through 
 many gorges that were impassable a century ago. 
 
 Earthquakes of Growing Mountain Ranges. — The actual 
 process of bending and breaking the rock structures 
 within a mountain mass sometimes causes sudden snaps 
 and slips of a few inches or a few feet. Tremors of 
 greater or less strength then spread in all directions from 
 
184 PHYSICAL GEOGRAPHY. 
 
 the seat of disturbance, diminishing their intensity as 
 they advance. On reaching the earth's surface they are 
 felt as earthquakes, producing more or less destruction. 
 Shocks of this kind are comparatively common in most of 
 the lofty mountains of the world. 
 
 Earthquake tremors travel through the earth's crust with 
 great velocity — from 10 to 40 miles a minute ; but as in 
 the cases of water waves the actual movement of the earth 
 at any point may be only a few inches a second, backward 
 and forward. The shocks produced by earthquake waves are 
 most violent at places directly over the seat of chief disturb- 
 ance. They may be very faint, causing no damage. They 
 may be strong enough to be felt violently over hundreds of 
 square miles, less distinctly over many thousands, and very 
 faintly (by the aid of delicate instruments) all over the earth. 
 
 Earthquakes of moderate violence are still frequent in 
 the Alps, occurring 5 to 10 times a year. Five centuries 
 ago (1348) a violent earthquake in the eastern Alps caused 
 a great landslide by which a valley was barred across and a 
 lake formed up stream from the slide. Countless thousands 
 of shocks must have been produced during the long ages of 
 mountain growth. The association of earthquakes with the 
 young tilted-block ridges of Oregon, with the more mature 
 mountains of Nevada, and with vigorous ranges like the 
 Alps and the Himalaya, is a natural result of the continued 
 disturbance or growth of the mountains. 
 
 Inhabitants of Lofty Mountains. — The people vi^ho 
 to-day dwell in the valleys of lofty mountains are in 
 many cases the descendants of races who formerly occu- 
 pied the adjacent lower lands, from which they were 
 driven by conquering invaders. Secluded valleys among 
 mountains serve as refuges, where pursuit is too difficult 
 
MOUNTAINS. 185 
 
 to be profitable. There the weaker race long remains un- 
 molested, holding little intercourse with the outer world, 
 and preserving old forms of speech and old-fashioned 
 customs. The invaders occupy the neighboring open 
 country; they engage in traffic with the other parts of 
 the world and advance in new ways of living. 
 
 The Basques live in the northern valleys of the Pyrenees, 
 near the angle of the Bay of Biscay. They are probably 
 descendants of the Iberians, an ancient people who occupied 
 a large part of Spain and France, from which they were 
 driven by invaders even before Csesar made those countries 
 subject to Eome, nearly 2000 years ago. The Basque lan- 
 guage is the only surviving form of Iberian, and is entirely 
 unlike other European languages. 
 
 The Svanetians occupy deep inner valleys in the Cau- 
 casus mountains, with dijSiculty accessible from the outer 
 country. Their ancestors were an ancient people who occu- 
 pied a far more extensive territory, from which they were 
 driven back to the mountains many centuries ago. There 
 ancient customs and a peculiar language are preserved ; there 
 the people still live, entirely apart from the ways of modern 
 times. Although daring and patriotic, they are ignorant and 
 superstitious. Their wretched houses are dark and dirty ; 
 their roads are only rough tracks. Arts and industries are 
 of the simplest order ; traffic is only by barter. 
 
 The small country of Switzerland is largely mountain- 
 ous. Andorra, a very small independent country in the 
 Pyrenees between France and Spain, is a modern instance 
 of the many small political divisions that prevailed in 
 Europe during the middle ages. These two small moun- 
 tainous countries are in striking contrast to the vast extent 
 of the Russian dominions, of whose area so large a part 
 consists of plains of comparatively even surface. 
 
186 PHYSICAL GEOGRAPHY. 
 
 The broader valleys within high mountains afford many 
 favorable places for settlement and cultivation. The nar- 
 rower valley floors are frequently swept over by destruc- 
 tive floods ; here the lower slopes of the valley sides are 
 commonly selected as sites for villages, and it is often 
 necessary to make terraces on the mountain flanks in 
 order to gain flat patches of ground for cultivation. 
 
 During winter the valleys among lofty mountains may 
 receive a heavy snowfall ; then for a season the people and 
 their flocks are gathered in the villages. In summer, when 
 the snows are melted from the mountain sides, cattle, sheep, 
 and goats are driven up from the valleys to pasture on the grassy 
 slopes of the ridges, and hay is carried, often on the backs of 
 the mountaineers, down to the villages for winter need. 
 
 In the Alps the condition of the people has greatly 
 improved since it came to be the habit of tourists to make 
 excursions among the mountains. Excellent roads have been 
 built ; good hotels are to be found in little villages ; paths 
 lead far up on the mountains, where huts of refuge are con- 
 structed to shelter the more adventur- 
 ous mountain climbers. Entertainment 
 of strangers has come to be an almost 
 national industry. 
 
 Many animals survive in mountains 
 after retreating from the surrounding 
 lower ground. Various species of Ibex 
 (mountain-goat) are found on the moun- 
 tains of Eurasia, each range having its 
 own peculiar species. From a common 
 
 Fig. 114. — Ibes. ^ \ . . 
 
 ancestry on the intermediate lower 
 ground the descendants in each range have varied in their 
 own way, independently of the others. This is a remarkable 
 illustration of the effect of mountains in keeping their inhabi- 
 tants apart from the rest of the world ; it may be compared 
 with the effect of isolation on islands. 
 
MOUNTAINS. 
 
 187 
 
 Subdued Mountains. — There are certain mountain ranges 
 of moderate heiglit, in which sharp peaks are absent and 
 bold cliffs are rare. The slopes are of moderate steep- 
 ness, and rock waste covers them almost from base to 
 summit. Mountains of this kind do not reach upward 
 into a climate very unlike that of their base ; and if not in 
 a dry or a frigid region, they may be forest-clad to the top. 
 
 The earthquakes that are common in mountains of active 
 growth and the landslides that happen frequently in moun- 
 tains where the valley sides are still steep are rare or unknown 
 
 Fig. 115. — The Mountains of North Carolina. 
 
 in these mountains of gentler form. Unlike the vigorous 
 forms of lofty mountains in which uplift and erosion are still 
 active, the rounded forms of these mountains express subdued 
 strength, as if their high peaks and ridges had been greatly 
 worn away by the long-continued attack of the weather. They 
 may therefore be called subdued mountains. 
 
 The Blue Ridge and other mountains of North Carolina 
 are good examples of subdued mountains. No sharp peaks 
 tower into the sky. The summits generally rise dome-like 
 in rounded outline. Heavy forests clothe their slopes. 
 
188 PHYSICAL GEOGRAPHY. 
 
 As in all regions of rugged form, out of the way of easy 
 travel and active traffic, the people living in the valleys 
 among subdued mountains preserve older fashions than those 
 of the more open lower country. This is seen in the home- 
 spun clothing and in the manner of speech of the IS'orth 
 Carolina mountaineers. 
 
 The mountains of Wales make another group of subdued 
 forms, but more rugged than the mountains of North Caro- 
 lina. Here remain some of the descendants of the Britons 
 who were driven from the more open lowlands of eastern and 
 central England by Saxon 9,nd Xorman invaders, 1000 or 1500 
 years ago. The Welsh language, therefore, represents the 
 original language of Britain, while the English language is 
 a compound of the speech of the invading peoples. 
 
 The higher parts of subdued mountains remain wooded 
 long after the surrounding lowlands are cleared and culti- 
 vated. Hence many mountains of this kind in central 
 Europe are named for their forests, as the Schwarzwald of 
 Germany, literally Black Eorest, but better translated Black 
 mountains. Timber from the forests may be sawed by the 
 abundant water power in the valleys, and the lumber sent 
 out to the more populous lowlands. 
 
 Worn-down Mountains. — In certain parts of the world 
 ancient mountain ranges have been almost completely 
 worn away. Their disordered rocks, once rising in lofty 
 peaks and ridges, and perhaps bearing snow fields and 
 glaciers, have been reduced to an almost plain surface, 
 little above baselevel and everywhere open to settlement. 
 
 The Piedmont belt of Virginia, between the Blue Ridge and 
 the coastal plain, is in many respects an excellent example 
 of a worn-down mountain range. It is a plain, not monot- 
 onously smooth, but undulating in graceful swells between 
 gentle depressions. Bare ledges are seldom seen. The soil 
 
MOUNTAINS. 
 
 189 
 
 is deep, fine, and fertile, and the district is very generally- 
 occupied by farms. The height to which the rock masses 
 once rose a.bove the present surface is reasonably estimated 
 
 Tig. 116. — The Piedmont Belt, Virginia. 
 
 as at least one mile ; it may have been two or three. The 
 wearing down of these ancient mountains to the rolling plain 
 
 Fig. 117. —Map of the Piedmont Belt, Virginia. 
 
 of to-day has required a period of time compared to which 
 that occupied in cutting the Colorado canyon is a brief 
 interval. 
 
190 
 
 PHYSICAL GEOGRAPHY. 
 
 It often happens that the plain surface of a worn-down 
 mountain range is here and there surmounted by rounded 
 hills or low mountains, 1000 or more feet high, com- 
 posed of the most resistant rocks of the whole region. 
 These hills are the last remnants of the mountains that 
 once towered over the surface of to-day. They may be 
 called monadnocks, after a mountain of this kind in 
 southwestern New Hampshire. 
 
 Several monadnocks are scattered over the Piedmont plain 
 of Virginia, one being shown in Fig. 116. Sometimes the 
 remnant mountains have the form of long ridges. The Alle- 
 gheny mountains of Pennsylvania are ridges of this kind, 
 
 Fig. 118. — Diagram of the Allegheny Mountains, Pennsylvania. 
 
 formed of the most resistant sandstones of the region, while 
 the weaker rocks are worn, down lower, as in Fig. 118. 
 These mountains have been uplifted and worn down more 
 than once. 
 
MOUNTAINS. 
 
 191 
 
 It is generally the case that old-mountain lowlands are 
 now uplifted above the position in which they stood when 
 worn down, so that they form plateau-like uplands. Their 
 streams are thus revived into a new period of activity, 
 and at once proceed to trench and dissect the upland. Dis- 
 sected uplands of this kind, bearing monadnocks in greater 
 or less number, are very common geographical forms. 
 
 The Piedmont belt of Virginia now stands several hundred 
 feet above baselevel. It is cut across by a number of active 
 streams that flow in winding, rocky, steep-sided valleys, from 
 100 to 300 feet beneath the upland plain. It is here that the 
 tilted rock structures of the ancient mountains are best seen. 
 
 One of the finest examples of an uplifted old-mountain 
 lowland is found in the plateau-like Slate mountains of 
 
 Fig. 119. — Gorge of the Rhine in the Slate Mountains, Germany. 
 
 western Germany. The broadly undulating upland is 
 generally cleared and cultivated. Here and there the 
 more resistant rocks stand up in forest-clad monadnocks 
 (M, Fig. 119). The Rhine has cut a deep gorge directly 
 through the upland, and the side streams are cutting steep 
 ravines in the bordering slopes. 
 
 The valley of the Ehine here consists of an upper trough (T), 
 with a narrow gorge (6^) cut in its floor. The ruined castles 
 
192 PHYSICAL GEOGRAPHY. 
 
 for which the valley is famous stand on the edge of the 
 trough, overlooking the inner gorge. The uplift by which the 
 cutting of the narrow gorge has been permitted cannot have 
 taken place very long ago (as the old mountains would count 
 time), for the river has not yet had time to widen its valley 
 floor. Ledges that formed rapids in the channel have been 
 removed by blasting. 
 
 Soutliern New Hampshire and Vermont, central and 
 western Massachusetts, and all of Connecticut include 
 many uplands, above wliicli occasional monadnocks rise, 
 
 
 Fig. 120. — The TTpIand of New England, with Monadnock in the Distance. 
 
 and beneatli which numerous valleys are worn. When an 
 observer stands on the uplands, the sky line is seen to be 
 comparatively even and independent of the attitude of 
 the tilted rocks whose ledges crop out on the valley sides. 
 If the valleys were in imagination filled up again to the 
 level of the uplands, the worn-down plain of the ancient 
 mountains of New England would be restored. 
 
 The plain does not now stand close to the baselevel with 
 respect to which it was worn down. It has been uplifted into 
 a slanting position, so that it slowly rises from sea level at 
 Long Island sound to a height of from 1400 to 1600 feet on 
 
MOUNTAINS. 
 
 193 
 
 the northern boundary of central and western Massachusetts. 
 The valleys have been carved in consequence of this uplift. 
 They are shallow near the coast, but deep (800 to 1000 feet) 
 in the interior, where the upland is higher. They are narrow 
 where the rocks are resistant, but wide open where the rocks are 
 weaker. The chief of the wider valleys is that of the Connecti- 
 cut river, excavated along a belt of relatively weak sandstones. 
 The monadnocks that crown the uplands are forested and 
 
 f-^^^^t^ ^^^^.f^^pfi^ ,^1-^,0^^ ^^ 
 
 Fig. 121. — Valley of the Deerfield in the New England Upland. 
 
 uninhabited. The uplands have a scattered farming popula- 
 tion, here and there gathered in small villages. The valley 
 sides are generally wooded, but sometimes hold sloping fields. 
 The larger valleys contain many villages and cities, and lead 
 the chief roads and railroads. Here is gathered the more 
 active manufacturing and commercial population of New 
 England. The valley sides are often quarried for resistant 
 building stones, like granite ; the broad Connecticut valley 
 floor yields brown sandstones, easily cut and carved, and much 
 used for ornamental architecture. 
 
194 PHYSICAL GEOGRAPHY. 
 
 The Highlands of Scotland are a bolder example of an 
 old, worn-down mountain region, now uplifted again and 
 dissected by numerous deep valleys. Their sky line is 
 rather uneven, and it is not probable that the old moun- 
 tains were ever worn down very low ; yet the sky line is 
 smooth compared to the excessive breaking, tilting, and 
 folding that the ancient rocks of the Highlands have 
 suffered. The valleys are from 2000 to 3000 feet deep. 
 The smaller branch valleys are called glens. The moun- 
 tains of to-day are the result of cutting down the valleys 
 and glens between them, just as in the so-called " moun- 
 tains" of the dissected Allegheny plateau of West Virginia. 
 
 The form of the Highlands has for centuries had a strong 
 influence on the history of the Highlanders. Like so many 
 other moimtaineers, they are the descendants of an early 
 people driven from the Lowlands by invaders. Taking refuge 
 in the Highlands, they have not lived on the mountains, but 
 in the deep glens. Being thus divided into small communities 
 or clans, the members of each clan became closely associated 
 and devoted to their local leaders ; and this way of living has 
 given the word " clannish " to our language. It was difficult 
 to survive in their rugged country ; hence the survivors 
 became hardy and thrifty. The Lowlands on the south are 
 occupied by descendants of the invaders ; their people and 
 language are of different stocks from those of the Highlands. 
 Thus arose the long feuds between the Highlanders and 
 Lowlanders, narrated in Scott's novels and poems. Now 
 that warlike strife has ceased between them, and means of 
 travel have increased, many of the Highlanders have left 
 their rugged glens and emigrated to other parts of the world. 
 
 The ancient rocks of worn-down mountains often con- 
 tain deposits of rare minerals and valuable ores. These 
 
MOUNTAINS. 195 
 
 have been formed by slow chemical changes that went on 
 deep within the crust of the earth when the rocks now 
 visible were buried far beneath the surface. As a conse- 
 quence, mining often flourishes in regions of this kind. 
 
 The Erzgebirge, or Ore mountains, of Germany are a worn- 
 down and again uplifted ancient mountain range. Many 
 valuable minerals occur in their rocks, and mining has been 
 carried on there for a long time. Indeed, this art is so gener- 
 ally practised in the subdued or worn-down and uplifted 
 ancient mountains of Germany that the German word for 
 mining is Bergwerk, or mountain-work. 
 
 The gold-bearing veins in the Sierra Nevada of California 
 and in the Klondike district of Alaska both occur in ancient, 
 worn-down mountains, now uplifted and again more or less 
 dissected. The important deposits of iron ore in northern 
 Michigan and Minnesota are similarly situated. 
 
 Embayed Mountains. — A mountain range near a con- 
 tinental border will be partly covered by the sea if a 
 
 Fig. 122. — Model of Embayed Mountains. 
 
 movement of depression lowers the level of the land. 
 The effect thus produced will be similar to tliat observed 
 
196 PHYSICAL GEOGRAPHY. 
 
 in the half-drowned coastal plain already described. The 
 valley floors and mountain flanks will be submerged to a 
 greater or less depth, and many long bays will enter 
 between outstretching promontories and islands. The 
 wasting of the ridges still standing above sea level will 
 continue as before ; deltas will be formed at the bay heads, 
 and sea cliffs will be cut on the headlands, with reference 
 to the new baselevel. 
 
 A partly drowned mountainous district has a coast line 
 of great irregularity. The long bays, called fiords., pro- 
 vide many protected harbors, but their waters are often 
 inconveniently deep for anchorage, and the lands may be 
 too steep for easy settlement. The outlying islands tempt 
 exploration from the mainland. It may well be believed 
 that the art of navigation of the open sea was developed 
 by a people inhabiting an irregular coast. 
 
 The coast of British Columbia and southern Alaska is bor- 
 dered by high mountains, into whose valleys the sea now 
 enters in long fiords. Lateral ridges, separated from the 
 mainland by water channels or sounds, stand forth as islands. 
 A navigable " inner passage " is thus provided for steam 
 vessels, well protected from the rough water of the open 
 ocean. The steep mountain sides, descending rapidly beneath 
 the sea, generally offer no flat ground for settlement ; but 
 most of the fiords now contain delta plains where streams 
 enter their heads ; here villages find convenient sites. 
 
 Since the Highlands of Scotland were uplifted and dis- 
 sected, a moderate depression has submerged the lower valleys 
 and carried the sea against the mountain flanks, where strong 
 cliffs are already cut on the headlands by the stormy waters 
 of the Atlantic. The fiords occupying the submerged valleys 
 are here known as sea lochs (loch = lake). Although adding 
 greatly to the beauty of the scenery, the change has decreased 
 
MOUNTAINS. 197 
 
 the habitability of the coast region, for many valley floors 
 that might have been occupied by fields and villages are now 
 drowned. The deltas growing at the head of the sea lochs 
 form convenient plains for cultivation, but they are seldom 
 of great extent. 
 
 Example for Review. — The highlands of northern Wis- 
 consin are part of a very ancient mountain region that 
 was worn down to a lowland of moderate relief before 
 
 Fig. 123. — Diagram of Baraboo Ridge, Wisconsin. 
 
 the rock layers of the ancient coastal plain of southern 
 Wisconsin were formed. Their formation as marine sedi- 
 ments was permitted when the southern part of the old- 
 mountain region was depressed and drowned beneath an 
 ancient sea, the drowned old-mountain lowland serving 
 as the foundation on which the covering strata were laid 
 down. At that time a monadnock that rose above the 
 old-mountain lowland remained for a time as an outlying 
 island; but as the depression of the region continued, it 
 was drowned and finally buried beneath the sea-bottom 
 deposits. 
 
198 PHYSICAL GEOGRAPHY. 
 
 To-day tlie upper strata of tlie ancient coastal plain 
 have been greatly worn away in the central and southern 
 part of the state, and the long-buried monadnock is now 
 revealed again as an isolated mountain, known as Baraboo 
 ridge, rising boldly above the floor of the inner lowland. 
 
 The lowlands and uplands of the ancient coastal plain 
 are for the most part fertile farming districts ; the unburied 
 monadnock stands apart as a forested ridge, quarried for 
 its hard stone. It rises through the weak strata of the 
 inner lowland like a long-preserved monument of the earth's 
 early history. 
 
-f- 
 
 CHAPTER VIII. 
 
 VOLCANOES. 
 
 The Violent Peocesses oe Natuee. 
 
 Most of the processes of nature go on without vio- 
 lence. The usual movements of the winds and currents, 
 the flow and ebb of the tides, the rise and fall of the 
 lands, the weathering and washing of rock waste are all 
 so placid that we gain confidence in the earth as a safe 
 home to live in. But sometimes natural processes of a 
 more violent behavior are witnessed. Hurricanes and 
 tornadoes bring destructive winds and torrential rains, 
 flashes of lightning and peals of thunder. Landslides 
 rush down mountain sides, overwhelming the valleys 
 below. Now and then the rocky crust beneath us quivers 
 and trembles in earthquakes. Great waves occasionally 
 roll in from the sea and sweep over low coastal lands. 
 Here and there volcanoes burst forth with terrible com- 
 motion. Nature then seems frightful and desti'uctive. 
 Those who are overtaken by such disasters struggle 
 against them, hopefully awaiting the return of the more 
 peaceful conditions under which their habits of life have 
 been -formed, for man could not survive it if he were 
 always battling against the wilder forces of nature. 
 
 Of all natural catastrophes the explosive eruption of a 
 great volcano is the most terrible. The air resounds with 
 its roaring. The sky is darkened and the sun is hidden 
 
200 
 
 PHYSICAL GEOGRAPHY. 
 
 by clouds of dust blown from the crater. The sea is 
 burdened with floating ashes. Glowing streams of lava 
 ■flow down the flanks of the volcano, driving away every- 
 thing that can take flight before them. Even the earth 
 
 Fig. 124. —Vesuvius in Eruption. 
 
 around is made to tremble as the gases and the lavas burst 
 out from their deep sources. No wonder that ignorant 
 races of men have imagined struggling giants to be impris- 
 oned under active volcanoes, nor that even the most 
 learned are baffled when trying to account for these terrific 
 displays of natural forces. 
 
VOLCANOES. 201 
 
 But violent as a volcanic eruption may be, it weakens, 
 and in time ceases. The sky clears, the sun shines again, 
 and Nature once more goes on in her quiet tasks. As the 
 years pass by and a soil is formed on the weathered ashes 
 and lavas, plants clothe their surface and man comes to 
 dwell on the flanks of the volcanic mountain. The strug- 
 gling giant within is forgotten ; fields and villages occupy 
 the slopes that once trembled and glowed in eruption. 
 
 In the long history of the human race many disasters 
 from volcanoes and earthquakes have been encountered, 
 and the race has gradually gained in courage and intelli- 
 gence as these and other trials have been survived. Les- 
 sons of this kind are hard to learn, but they seem to be 
 among those that the earth has in store for us. 
 
 The Growth and Dissection of Volcanoes. 
 
 Young Volcanoes. — Volcanoes are formed by the ascent 
 of molten rock, called lava, through fractures or passages 
 leading from unknown depths through the earth's crust to 
 its surface, on the land or on the sea floor. The eruption 
 of the lava is generally accompanied by explosions of 
 steam and other gases. 
 
 The cause of volcanic eruptions still needs as much study as 
 that of the various displacements of the earth's crust referred 
 to on earlier pages. It is believed by many that the ascent 
 of molten lava from its deep source is chiefly caused by pres- 
 sures similar to those which cause movements in the earth's 
 crust. As the lava nears the surface and meets water in greater 
 or less quantities, explosions of steam take a violent part in 
 the eruptions. 
 
202 
 
 PHYSICAL GEOGBAPHY. 
 
 The early growtli of a volcano has occasionally been 
 observed. The outburst is preceded and accompanied by 
 earthquakes, which indicate the breaking of an upward 
 passage through the underground rocks, before hot lavas 
 make their appearance at the surface. When the eruption 
 is accompanied by gaseous explosions, much of the lava is 
 blown into fragments, of which the smaller are called ashes 
 or cinders. The larger blocks and the coarser ashes 
 accumulate in a conical heap, or volcano, frequently having 
 remarkable regularity of form, a cup-shaped hollow or 
 crater being kept open over the vent by the oiitbursting 
 gases. The finer ashes or dust may fall far a,way. When 
 the eruption is less violent, the lava runs forth more 
 quietly in a stream or flow following the slopes of the 
 ground. Explosive and quiet eruptions may alternate 
 in irregular succession. 
 
 Monte NuGvo (New Mountain) is a small volcano that was 
 formed on the north side of the Gulf of Naples in Italy in 
 1538. Earthquakes occurred thereabouts for two years before 
 
 the eruption, when in 
 a week's time a cone 
 was built up 440 feet 
 high, half a mile in 
 diameter at the base, 
 and with a crater over 
 400 feet deep. Masses 
 of lava "as large as 
 an ox " were shot into 
 the air by the bursting of great bubbles of gas or steam that 
 ascended through the lava in the vent. Finer ashes fell over 
 the country for several miles around. The people of the 
 neighboring villages fled in terror from their homes. 
 
 Fig. 125. — Monte Nuovo. 
 
VOLCANOES. 203 
 
 A greater eruption took.place in Mexico in 1759, when the 
 volcano Jorullo (pronounced Ho-rul-yo) was built on the cen- 
 tral plateau, burying fertile fields of sugar cane and indigo. 
 The outburst was preceded by earthquakes ; the eruption 
 continued half a year, building six cones and pouring out 
 extensive lava flows. The highest cone, Jorullo, rose 700 
 feet above the plateau. The flows retained a perceptible 
 heat for over 20 years. 
 
 Many examples might be given of marine eruptions. In 
 1867 a shoal was discovered among the Tonga Islands of the 
 Pacific (latitude 20° 20' S., longitude 175° 20' W.), the surround- 
 ing sea floor being about 1000 fathoms deep. In 1877 smoke 
 was seen ascending from the sea surface over the shoal. In 
 October, 1885, an island had been formed two miles long and 
 200 feet high. At this time a terrific eruption was in prog- 
 ress, enormous clouds of constantly changing form rising over 
 the island. The shocks of the explosions were felt on neigh- 
 boring islands, and the sound was heard 200 miles away. As 
 the island consisted chiefly of ashes, it has since then been 
 rapidly consumed by the waves and will soon disappear, 
 unless new eruptions occur. 
 
 Most volcanoes have not been observed in their early 
 growth, yet even if not now in eruption, so perfectly do 
 they correspond in form and structure with such examples 
 as Monte Nuovo and Jorullo that no doubt can remain as 
 to their origin. 
 
 In northern California there is a cinder cone of remark- 
 ably perfect form and certainly of recent date, although there 
 is no record of its eruption. The cone, built of loose ashes, 
 is 2000 feet in diameter at its base, and rises 640 feet to a 
 circular rim enclosing a crater 240 feet deep. It is perfectly 
 barren. Although of moderate height, its ascent is difiicult, 
 as the ashes slide under a man's weight. A stream of lava 
 emerges near the base of the cone, and, flowing westward into a 
 
204 
 
 PHYSICAL GEOGRAPHY. 
 
 neighboring valley, forms a lava field a mile wide and nearly 
 three miles long. The surface of the field is so covered with 
 great clinkery blocks of lava as to be almost impassable. It 
 is still unweathered and barren. The edge of the field is a 
 steep clinkery slope 100 feet high. It obstructs a stream 
 from the south, which forms Snag Lake, so called from the 
 dead trees still standing in it. The lake outlet runs north 
 along the west edge of the lava. On all sides the surface of 
 the country is covered with a layer of volcanic ashes and 
 
 Fig. 126. — Cinder Cone ajid Lava Flow, California. 
 
 dust, six or more feet deep near the cone, thinner and finer 
 further away, yet recognizable at a distance of eight miles. 
 From the size of trees growing on the ashes, it is estimated 
 that the cinder cone was built about 200 years ago. The 
 lava flow is younger, but none of the Indians or early 
 settlers thereabouts (1845) observed its eruption. 
 
 Volcanoes are unlike the structures thus far described, in 
 being composed of materials that have been forced up, 
 melted, through vents (pipes or fissures) in the rocky crust 
 of the earth and built upon a land surface or a sea floor. 
 They are peculiar in their relatively rapid formation, so 
 that much attention is attracted to their manner of growth. 
 Mountains of tilted or folded structure that still possess 
 their original form, little changed by denudation, are great 
 
VOLCANOES. 205 
 
 rarities. But many volcanoes have been built so rapidly 
 and so lately that their surface is very little affected by 
 weathering. 
 
 Great Volcanoes Many large volcanoes, whose first 
 
 eruption must have occurred many thousands of years 
 ago, are still active. After periods of more or less com- 
 plete rest, they burst forth again, blowing out showers of 
 ashes, building their cones to a height of 10,000 feet or 
 more, and adding new lava streams to their flanks, so as 
 to gain a diameter of 10 or 20 miles or more at the base. 
 The melted lava often breaks forth from the mountain 
 side and flows down to gentler slopes on the flanks and 
 out upon the surrounding country; thus the cone as a 
 whole comes to have concave slopes and a rudely bedded 
 structure of ashy and dense lavas. All the greater vol- 
 canoes of the world are the product of many eruptions. It 
 is probable that the periods of rest have been much longer 
 than the spasms of activity. 
 
 A rough classification of volcanoes groups them as active, 
 when they are frequently in eruption ; dormant (sleeping), 
 when now at rest, though giving signs in hot springs and sul- 
 phurous vapors that activity may be resumed ; and extinct, 
 when they give no indication of recent or future activity. It 
 is not possible to make certain distinction between the last 
 two classes ; great eruptions have taken place in volcanoes 
 after all signs of activity had ceased. 
 
 The steam issuing from a volcano is condensed in heavy 
 clouds. At night the glowing lava, white-hot in the 
 crater, yellow or red on the flanks of the cone, illuminates 
 the clouds, often giving the appearance of flames. Showers 
 
206 
 
 PHYSICAL GEOGRAPHY. 
 
 of ashes may bury villages, fields, and forests, as they 
 chance to fall. The commotion in the atmosphere during 
 a violent eruption often causes rainfall. The floods thus 
 supplied may be increased by the water from melted snow 
 on the upper slopes of the cone, and occasionally by hot 
 
 Fig. 127. — Excavations in Herculaneum. 
 
 water thrown out from the crater itself. The floods 
 gather the fresh-fallen dust and ashes, producing muddy 
 torrents that overwhelm the lower lands. 
 
 At the eruption of Conseguina, Central America, in 1835, 
 ashes destroyed trees and dwellings 25 miles south of the 
 volcano ; thousands of cattle and innumerable wild animals 
 and birds were killedi Lava blocks in fragments 5 or more 
 
VOLCANOES. 207 
 
 feet in diameter are strewn for 10 or 15 miles around the 
 great cone of Cotopaxi, Ecuador. 
 
 A tremendous eruption of Galung-gung, a forested volcano 
 in a populous part of Java, took place in 1822 ; torrents of 
 hot water, mud, and ashes rushed down the valleys, flooding 
 the rivers and drowning a great number of men and animals ; 
 for 24 miles not a trace of numerous villages and plantations 
 was left. 
 
 The first recorded eruption of Vesuvius, a.d. 79, darkened 
 the sky with its ashes. The ancient city of Pompeii was 
 buried in ashes and about 2000 persons (estimated at one- 
 fifteenth of the population) were killed. Herculaneum, near 
 by, was overwhelmed with torrents of ashy mud. After 
 being long forgotten and overgrown by modern villages, 
 parts of these cities have been laid bare by excavations in 
 this century, affording many illustrations of ancient architec- 
 ture and of ancient modes of living. 
 
 E|rthquakes in Volcanic Districts. — The shocks of a 
 violent eruption may shatter the volcano, breaking its sides 
 and causing great landslips. The earthquakes thus caused 
 are felt for many miles around the volcano. The explod- 
 ing gases produce thundering sounds, sometimes audible 
 for hundreds of miles. 
 
 Besides the earthquakes directly produced by the explosive 
 eruptions of volcanoes, it is probable that many other earth- 
 quakes in volcanic districts are the result of disturbances 
 within the crust of the earth not directly connected with 
 volcanic action. The numerous earthquakes of Japan and 
 Italy sometimes accompany eruptions, but are more frequently 
 independent of all visible eruptive action. 
 
 Great destruction is caused by earthquakes in regions that 
 are frequently shaken. In southern Italy 20,000 lives were 
 lost in the earthquake of 1688 ; 49 cities and villages were 
 
208 PHYSICAL GEOaRAPHT. 
 
 destroyed, and 93,000 persons were killed in the earthquake 
 of 1693 ; 32,000 persons were killed in a district having a 
 population of 166,000 by the earthquake of 1783. 
 
 Distribution of Volcanoes. — Volcanoes generally occur 
 near the sea coast or on the sea floor, but a considerable 
 number of cones and flows are known far in continental 
 interiors. Volcanoes are more numerous on the borders 
 of the Pacific Ocean and of the mediterranean seas than 
 on the coasts of the Atlantic, but many volcanic islands 
 are known in the Atlantic as well as in the Pacific and 
 Indian oceans. 
 
 It is estimated that over 300 volcanoes are now active, 
 about 100 of these standing on the continents. Nearly all 
 the high oceanic islands, far from the continents, are of vol- 
 canic origin. Soundings have discovered a number of conical 
 mountains rising from the sea floor, but not reaching the sur- 
 face ; their form leaves little doubt that they are volcanoes. 
 Dacia Bank, east of Madeira, rises with steep slope from the 
 Atlantic floor, over 1000 fathoms deep, to within 50 fathoms 
 of the surface. 
 
 In continental interiors extinct volcanoes, young cinder 
 cones, and barren lavas are known on the plateaus of Arizona, 
 300 miles from the ocean ; in Colorado, 800 or more miles 
 inland ; in Tibet, 500 or more miles inland. Several active 
 volcanoes in Mexico, Central America, and elsewhere are so 
 far from the coast that direct connection with sea water should 
 not be regarded (as it has been) necessary to eruptions. 
 
 Like other lofty mountains, volcanoes rise high enough to 
 possess different climates at successive heights. Mt. San 
 .Francisco, a volcano built on the plateau (5000 to 6000 feet 
 elevation) south of the Colorado canyon, rises 6000 feet 
 above the desert uplands and bears dense forests on its 
 slopes. ' Its summit ascends above the tree line, bearing 
 
 I 
 
VOLCANOES. 
 
 209 
 
 patches of snow most of the summer. Among the Alpine 
 plants there collected, nine are of the same species as those 
 living near sea level in Greenland. Lofty volcanoes near the 
 equator in South America and Africa bear snow on their 
 summits. 
 
 Islands formed by the growth of volcanoes in mid-ocean 
 are often bordered by wave-cut cliffs, so that it is almost 
 impossible to find a landing place on their shores. Being 
 nearly inaccessible, as well as 
 distant from the continents, they 
 are all the more lonesome. St. 
 Helena, a volcanic island in the 
 south torrid Atlantic, was for this 
 reason a well-chosen place for the 
 imprisonment of the emperor 
 Napoleon. 
 
 A remarkable instance of the 
 effect of isolation on the occu- 
 pants of a remote volcanic island 
 is seen in the language of the 
 people of Iceland. Icelandic, 
 Norwegian, Swedish, and Danish 
 were all one language a thousand 
 years ago ; but while the isolated Icelandic has preserved 
 its ancient form with slight change, the languages of the 
 continental countries have been much modified ; that of Den- 
 mark especially having been affected by the neighborhood of 
 Germany. 
 
 Fig. 128. 
 
 A Volcanic Island (section 
 and plan). 
 
 Lava Flows. — Great flows of lava sometimes run 
 beyond the base of the volcano in which they break 
 forth. Their surface is comparatively smooth, if it remains 
 unbroken after first cooling, but extremely ragged and 
 clinkery, if the first crust is repeatedly broken by con- 
 tinued movement. The edge of a clinkery flow may form 
 
210 PHYSICAL GEOGBAPHT. 
 
 a bluff 100 feet or more in height. On the Uinkaret 
 plateau of the Colorado canyon districts stands a throng 
 of volcanic cones, from which broad streams of lava 
 descend the bordering cliffs in black cascades and form 
 barren lava floods on the lower Sheavwits plateau on 
 the west. The eruptions are therefore younger than the 
 breaking of the plateaus. 
 
 In 1783 a great flood of ^lava rose from a deep fissure in 
 Iceland, the lava issuing tranquilly for the most part, flow- 
 
 Fig. 129. — Lava Flows on the Plateaus of Arizona. 
 
 ing away in vast sheets on each side, and advancing in 
 streams far along the lower valleys. Hundreds of small 
 cones were built over the fissure, which was 20 miles long. 
 In the course of ages successive lava floods of this kind have 
 built up the plateau of Iceland of generally level aspect, the 
 loose slaggy cones of earlier eruptions being gradually buried 
 under later sheets. 
 
 Two lava streams of the eruption of 1783 in Iceland flowed 
 down valleys 45 and 60 miles from their source, gaining a 
 depth of several hundred feet where the valleys were nar- 
 row, and spreading out in lake-like plains where the valleys 
 were open. The water of side streams was dammed and 
 
VOLCANOES. 
 
 211 
 
 rose in lakes. Twenty villages were destroyed by the floods 
 of lava or water ; 9000 persons (about one-seventh of the 
 island's population) and a great number of cattle perished, 
 not only at the time of the eruption, but afterwards during 
 a famine caused by the burial of the pastures and by the 
 desertion of the coast by fish. 
 
 The form assumed by successive lava flows in building a 
 plateau is sometimes imitated on a cold winter night when 
 trickling streams of water, supplied by daytime thawing, are 
 frozen as they advance. If the water is artificially colored 
 successive flows are made plainly visible. 
 
 Lava floods, thousands of square miles in area, have 
 been poured forth in Idaho, Oregon, and Washington, 
 where they form an extensive plateau in a broad depres- 
 sion among the surrounding mountains. As they cannot 
 be traced to any source in volcanic cones, they are thought 
 to have come from fissures now concealed and long unused. 
 
 Between the Columbia and Snake rivers, in eastern Wash- 
 ington, the plain surface of the lava flood meets the enclosing 
 mountain s'^ just as the sea 
 
 meets ahalf-drowned moun- 
 tain range. The lava forms 
 level bays between the 
 ridges ; the ridges stand 
 forth like promontories ; 
 outstanding peaks rise like 
 islands over the plain. A 
 rugged mountainous basin 
 has thus been converted 
 into a plateau. Part of 
 the lava plain has been up- 
 lifted in dome-like form to 
 a greater height than the 
 rest, and is now deeply dissected by valleys 
 called the Blue mountains (B, Fig, 130). 
 
 Pig. 130. — The Lava Plateau of Idaho, Oregon, 
 and WaBhington. 
 
 This part is 
 
212 
 
 PHYSICAL GEOGRAPHY. 
 
 Calderas. — In some volcanic regions the high central 
 part of a cone is replaced by a broad and deep basin, or 
 caldera, from 1 to 5 or more miles in diameter, only the 
 lower rim of the cone remaining. The inner walls of the 
 rim exhibit the broken edges of lava beds, which slope 
 outwards from the lost cone on whose flanks they were 
 formed. 
 
 Fig. 131. — Diagram of a Caldera. 
 
 When extensive deposits of lava blocks and ashes lie in 
 the surrounding country, it is thought that the cone was 
 destroyed and the caldera was formed chiefly by violent 
 explosive eruptions. When such deposits are absent, it is 
 thought that the caldera was formed by the caving in of the 
 central area, on account of the withdrawal of a large body of 
 lava from beneath. 
 
 The Azores, a group of volcanic islands in the North 
 Atlantic, contain a number of large calderas, whose floors 
 are partly occupied by villages and fertile fields and partly 
 
VOLCANOES. 
 
 213 
 
 by lakes. Other examples are known in Italy, the Hawaiian 
 islands, and elsewhere. 
 
 Deception island, in the .--''"' ""■. 
 
 South Shetland group, beyond 
 Cape Horn, is the high rim of 
 a caldera, breached on one side 
 by a narrow gap, which gives 
 entrance to a quiet circular 
 bay. Layers of ice are to be 
 seen between beds of ashes 
 and lava on the caldera walls. 
 
 The cone of Vesuvius has 
 been built in a large caldera of 
 more ancient origin. The cone 
 buries one side of the caldera 
 
 rim, the other side being known Fig. 132. - DeceptioB island, a voicamc 
 as Monte Somma. '^^"^''^ 'pi^" ^""^ section). 
 
 Dissected Volcanoes. — Active streams running down 
 the slope of volcanic cones carve ravines on their flanks. 
 Many ravines are formed during the periods of rest in the 
 growth of the great volcanoes, only to be filled again by 
 
 later eruptions of 
 lavas and ashes. 
 After eruptions 
 cease, the ravines 
 deepen more and 
 more, leaving sharp 
 ridges between 
 them, and at last 
 dissecting the cone so deeply as to leave little appearance 
 of its original shape. Hence, as in other geographical 
 forms, it is important to describe volcanoes with due 
 regard to their stage of growth or of decay. 
 
 Fig. 133. — The Cone of Vesuvius in the Caldera 
 of Monte Somma. 
 
214 
 
 PHYSICAL GEOGEAPHY. 
 
 Mt. Shasta, in northern California, is furrowed on all sides 
 by gigantic ravines, but its conical form is still well preserved 
 (Figs. 134, 135). Many meadows about its base mark the 
 site of lakes formed by lava-flow barriers, and now filled and 
 drained. The best agricultural land of the region is of this 
 origin. 
 
 Fig. 134. — Contour Map of Mount Shasta, CaUfomia. 
 
 Mt. Hood, Oregon, is so deeply dissected by radiating 
 valleys between sharp radial spurs that its form has become 
 very irregular, A number of extinct and more or less dilapi- 
 dated volcanic cones surmount the plateaus of Arizona and 
 New Mexico, Mts. San Francisco and Taylor being among 
 
VOLCANOES. 
 
 215 
 
 the best examples. The Cantal, an ancient Tolcanic cone 
 about 40 miles in diameter on the central plateau of France, 
 
 Fig. 135. — Mount Shasta. 
 
 is cut to pieces by radiating 
 valleys. Its present height is 
 but a small part of the original 
 height, judging by the atti- 
 tude of the slanting lava beds 
 in the radial ridges. A rail- 
 road and a highway, entering 
 by a valley from the southwest, 
 run almost through the center 
 of the dissected cone on a low 
 pass, and depart by a valley 
 to the northeast. 
 
 One of the most superb 
 calderas in the world is 
 that which contains "Crater 
 lake" in southern Oregon. 
 
 Fig. 136. — Mount Hood. 
 
216 
 
 PHYSICAL GEOGRAPHY. 
 
 Its sides were deeply scored by radial ravines before the 
 summit of the cone was destroyed in the production of 
 the caldera (probably by falling in), for the ravines as well 
 as the lava beds are distinctly cut off by the high cliffs of 
 the caldera wall. A little cone, built by a small eruption 
 after the caldera was made, forms Wizard island in the lake . 
 
 Fig. 137. — Contour Map of Crater Lake, Oregon. 
 
 Volcanic Necks and Dikes. — Even when the volcanic 
 cone is entirely worn away, the neck or column of lava that 
 rose through a tube-like passage from deep within the earth 
 may still be seen. The lava neck is often harder than the 
 enclosing rock, and it then retains a considerable height 
 above the surrounding worn-down surface, standing up as 
 a butte. In the same way, the lava that rose in a fissure 
 may in time come to stand up above the adjacent surface 
 like a natural wall, structures of this kind being called dikes. 
 
VOLCANOES. 
 
 217 
 
 The broad valley plain of the St. Lawrence in southern 
 Quebec is surmounted by a number of strong volcanic buttes 
 rising several hundred feet over the lowland, and visible 
 
 M&t^^^^ 
 
 Tig. 138. — Monnt Johnson, near Montreal, Canada. 
 
 for many miles across its flat surface. One of them gives 
 its name to the city of Montreal (Mount Eoyal). All of 
 them testify to the great denudation of the surrounding 
 
 Fig. 139. — Volcajiic Necks, Arizona. 
 
 region, for although the lavas rise high above the plain, they 
 give no evidence of surface overflows, such as must have 
 occurred if the region had had its present form at the time of 
 eruption. 
 
218 
 
 PHYSICAL GEOGRAPHY. 
 
 Volcanic necks are common on the plateaus of !N"ew Mexico 
 and Arizona, where they attain a height of from 1000 to 2000 
 feet above the surrounding surface, with diameters of a quarter 
 or a half mile. 
 
 Dissected Lava Plateaus. — The great lava plateau of 
 Idaho, Oregon, and Washington is trenched by many 
 rivers whose courses are extended across the upland from 
 their source in the adjoining mountains. The canyon 
 of Snake river, along the boundary between Idaho and 
 
 Fig. 140. — Dissected Lava Plateau of Southern India. 
 
 Washington, 4000 feet deep and 15 miles broad, rivals 
 the Colorado canyon, except in varied coloring. Buried 
 mountain peaks are revealed in the canyon walls ; one of 
 them rises 2500 feet above the river and is covered by 
 1500 feet of bedded lava. 
 
 Between some of the lava beds are laj^ers of sand and 
 gravel or of volcanic dust and ashes. Petrified tree stumps 
 and trunks occur in some of these layers, showing that there 
 was time enough in the intervals between successive lava 
 floods for the formation of soil and the growth of forests. 
 
VOLCANOES. 219 
 
 The young mountains of southern Oregon are broken and 
 tilted blocks of this great lava plain. 
 
 An extensive lava plateau occupies southwest India ; its 
 western margin is deeply dissected by streams fed by the 
 heavy rains of the summer monsoon. Here, as in Oregon, 
 the horizontal layers of dense lava form cliffs, while the 
 more ashy layers are weathered back into slopes and plat- 
 forms, thus imitating the forms of the dissected plateaus of 
 Arizona. 
 
 The Faroe islands (Danish, meaning sheep) are the half- 
 drowned remnants of a deeply dissected lava plateau origi- 
 nally resembling the lava plateau of Iceland, whose nearly 
 level lava beds form the tables of the several islands. The 
 exposed outer coasts are cut back into great cliffs from 
 1500 to 2000 feet high. The harborless outer islands are 
 reached with difficulty, their small population being often 
 storm-bound for weeks together. The eggs of sea birds 
 nesting on the cliffs constitute an important article of food 
 supply, and the bird rocks are valuable property for the vil- 
 lages to which they belong. The hardy custom of descending 
 to the nests by a rope let down from the cliff top is here 
 practised. 
 
 The Giant's Causeway in northern Ireland is on the margin 
 of a dissected lava plateau, whose cliffs descend boldly to the 
 sea. The name is given because the lava beds are cracked or 
 "jointed" so that their surface imitates an artificial pavement 
 or " causeway." 
 
 Lava Table-Mountains. — Lava flows occupying valleys 
 near the base of volcanoes frequently weather and waste 
 more slowly than the adjoining rocks. Hence as the 
 region is worn down it may happen that the flows come 
 to a stand above the adjacent country in the form of table- 
 mountains, or mesas, flat topped and rimmed around with 
 a cliff and talus slope. The volcano from which the flow 
 
220 
 
 PHYSICAL aEOGEAPBY. 
 
 issued may have been completely worn away, the table- 
 mountain standing quite apart from the neck or dike that 
 marks its source, as in Fig. 141. 
 
 Many lava flows of the extinct volcanic district in central 
 France are thus converted into flat-topped ridges and iso- 
 lated mesas. On one of the mesas the ancient Gauls built 
 
 Fig. 141. — Diagram of a Young Volcano in the Background, changed by EroBion to 
 Lava-Capped Mesas in the Foreground. 
 
 the town of Gergovia, where they long resisted the attack of 
 the Romans under Caesar, the cliff rim of the mesa serving 
 as a natural fortification. 
 
 A number of table-mountains capped with long lava flows 
 occur on the western slope of the Sierra Nevada of California. 
 The gravels that lie in the ancient valley troughs beneath 
 the lava flows have been mined for the grains of gold that 
 they contain. Human relics, chiefly in the form of stone 
 mortars, have been found in these gravels, showing that man 
 occupied the region long ago, before the time of the lava 
 eruptions. 
 
 Example for Review. — The gently rolling plains of 
 eastern Montana are trenched by the narrow and steep- 
 sided valleys of the Missouri river and its branches. The 
 
VOLCANOES. 221 
 
 upland surface is so even over large areas and so little 
 broken by valleys, except near the larger rivers, that it 
 might at first sight be taken for a young plain raised from 
 the sea in a recent stage of the earth's history. But here 
 and there buttes, dikes, and mesas of lava surmount the 
 plain, telling clearly that the surface of the region was 
 once much higher than now, for the dikes and buttes mark 
 fissures and tube-like passages that were once enclosed 
 by extensive rock layers, now removed, and the mesas 
 are the remnants of lava flows that ran down from some 
 
 Fig. 142. — Diagram of Dike and Mesa. 
 
 volcanic source to the lowest ground they could reach. 
 Hence the gently rolling plain must be an old, worn-down 
 surface, and when worn down it must have stood at a 
 moderate altitude above the sea. The narrow valleys 
 now cut beneath the denuded surface show that the 
 whole region has been broadly uplifted after it was worn 
 down. 
 
 The thin grass of the treeless plains gives pasture to 
 herds of cattle that range from stream to stream. The 
 dikes and mesas are rocky and barren. The valley floors 
 contain fertile fields of small breadth, and here the houses 
 and villages of the region are generally located. 
 
^ 
 
 CHAPTER IX. 
 
 RIVERS AND VALLEYS. 
 
 The Lifelike Behavior of Rivers. 
 
 It is natural that to one who is ignorant of the carving 
 of land forms from their youth through maturity to old 
 age the surface of the earth should seem lifeless, for it is 
 carved so slowly that even an old man can see no change 
 in the form of the hills and the valleys around the home 
 of his boyhood. But every one may recognize the lifelike 
 behavior of rivers. In possessing active movement they 
 imitate one of the most interesting " characteristics of ani- 
 mal life, and thus they seem to have a life of their own. 
 Ascend a river and trace its branches to their many sources, 
 even to the smallest brooks and rills ; they are all found 
 to be busy bearing tribute to the main stream. Follow 
 the river down its valley, and its growing volume, flowing 
 steadily onward, leads as if with conscious purpose to the 
 sea. The change of behavior from the active upper waters 
 to the sedate lower current suggests that we might 
 describe our own growth from youth to old age in terms 
 that apply to the " river of life." Indeed the part that 
 rivers take in the work of the world is so full of activity 
 that they enter the figures of poetic literature even more 
 than great mountains or vast oceans. 
 
 The more rivers are studied, the more wonderful their 
 place in the system of nature is found to be. They wash 
 
BIVER8 AND VALLEYS. 
 
 223 
 
 along in every part of their course some share of the waste 
 of the land on the way to the sea. They work untiringly. 
 Mountains may tower aloft where the crust of the earth 
 has been upheaved by irresistible forces from within ; but 
 the weather attacks them, the clouds gather around their 
 summits, rain and snow fall upon them, and the streams 
 and rivers bear off their waste until they are worn away. 
 
 Fig. 143. — The Mohawk Valley. 
 
 Only when all the hills are worn down can the rivers rest 
 from their labors ; and even then, if the lands are again 
 uplifted, the rivers will at once dutifully resume their 
 tasks. 
 
 The broad valleys that well-established rivers carve for 
 themselves in the lands are among the most attractive sites 
 for human settlements. They are somewhat protected from 
 inclement weather as compared to the adjoining uplands. 
 They are floored with an abundant soil of fine texture. 
 Their different parts are in easy communication with each 
 
224 PHYSICAL GEOGRAPHY. 
 
 other. Many roads and railways take advantage of the 
 low grades afforded by valleys that have been worn 
 through mountain ridges. Indeed so well are man's needs 
 supplied in fertile valleys, one might almost fancy that the 
 valleys had been carved by their rivers for man's benefit. 
 The truth is, however, that man often makes his home 
 in valleys simply because he there finds more favorable 
 surroundings than on the neighboring uplands. 
 
 The Movement of Water Underground. 
 
 Ground Water. — The water supplied by rain and snow 
 is disposed of in part by evaporating from the surface, in 
 part by running down the slopes of the land to the streams, 
 and in part by sinking beneath the surface ; the last part 
 is called ground water. 
 
 The proportions of these several parts vary under dif- 
 ferent conditions. The greater part of a light and long- 
 continued rain may pass into ground water, especially if 
 falling on a plain. A very heavy rain, or " cloud-burst," 
 falling on strong slopes, is nearly all disposed of by direct 
 run-off, causing sudden floods. 
 
 When the ground is frozen, little water can enter it ; hence 
 rivers rise in floods when deep snow is rapidly melted by a 
 heavy rain. In arid regions a great part of the rainfall may 
 dry off from the ground. 
 
 When a region has been thoroughly dissected, steep slopes 
 lead down to the streams. Then a large part of the rainfall 
 is discharged by direct run-off, and the streams rapidly change 
 in volume with every change from dry to wet weather. 
 
 Ground water is essential to the growth of plants, whose 
 roots must reach moist earth. Where grass and trees cover 
 
RIVERS AND VALLEYS. 
 
 225 
 
 the surface, much ground water taken in by their roots is 
 discharged into the air by evaporation from their leaves. 
 
 Loosely consolidated strata and deep rock waste take in 
 much ground water. Firm rocks, such as granites, allow but 
 little water to enter beneath the weathered waste on their 
 surface. A region underlain by heavy strata of limestone (a 
 comparatively soluble rock) may have many underground pas- 
 sages dissolved along the rock crevices ; thus, nearly all the 
 water may be .withdrawn from the surface. 
 
 Caverns. — Caverns in limestone districts are the result 
 of the solvent ac- 
 tion of underground 
 waters . The Mam- 
 moth cave of Ken- 
 tucky and the Luray 
 cavern of Virginia 
 are famous examples 
 of this class. Streams 
 gathering on the sur- 
 face descend to underground passages by sink holes or 
 swallow holes. After flowing underground for some dis- 
 tance, they may issue in an enlarged and turbid current 
 from the mouth of a cavern. 
 
 Fig. 144. — Diagram of Cavern and Sink Hole. 
 
 Several species of animals dwelling in the complete dark- 
 ness of caverns are blind, but their senses of hearing and 
 touch are highly developed. 
 
 Where sink holes and cavern drainage prevail, so much 
 water enters the ground that surface streams are compar- 
 atively I'are. When the sink holes or the underground 
 
226 
 
 PHYSICAL GEOGRAPHY. 
 
 passages become obstructed, ponds and lakes are formed 
 in the surface basins. 
 
 The limestone uplands of Kentucky and Tennessee exhibit 
 many of these features. The scarcity of surface water is 
 often an inconvenience. Florida has numerous sink-hole 
 ponds and lakes. The limestone uplands of Normandy in 
 northwestern France have many valleys ending in sink holes. 
 
 Fig. 145. — Natural Bridge, Syria. 
 
 As denudation progresses, the roof of a cavern may fall in 
 more or less completely. The beautiful Natural Bridge of 
 Virginia is the remnant of a cavern roof. Fig. 145 gives a 
 view of a natural bridge in Syria. 
 
 Springs. — Very little ground water remains perma- 
 nently beneath the land surface. Sooner or later, after 
 descending to less or greater depths, it comes to the sur- 
 face at a lower level than where it entered, emerging in 
 the form of springs and joining the run-off of streams. 
 
BIVERS AND VALLEYS. 
 
 227 
 
 Fig. 146.— Diagra-m showing Distribntion of Ground 
 Water (black). 
 
 The movement of ground water is comparatively slow 
 while percolating among the particles of rock waste or 
 through the crevices of rocks. Where a large part of the 
 rainfall enters the ground, the volume of the streams fed 
 by springs is less variable than where the rainfall is mostly 
 discharged by direct run-off during and shortly after a storm. 
 
 Ground vv^ater slowly moves from hills and slopes, 
 descending to lower 
 levels and accumu- 
 lating beneath the 
 lower ground. It 
 may, therefore, be 
 generally found near 
 the surface in val- 
 leys, where the soil 
 is usually damp. At the base of a slope, the ground water 
 may issue in a spring, supplying a small brook. Innu- 
 merable small springs occur unnoticed in the banks of 
 streams, increasing their volume. 
 
 In regions of sufficient rainfall and moderate relief, the 
 ground water may be reached at almost any point except 
 hill-tops by sinking wells to a depth of from 10 to 40 feet. 
 The bottom of the well should be a few feet deeper than the 
 level at which the trickling stream of ground water enters 
 it from the crevice, so as to accumulate water in sufficient 
 volume to supply ordinary domestic uses. 
 
 Ground water and spring water carry very little rock 
 waste (unless in solution), and are generally clear and 
 pure. For this reason wells and springs generally afford 
 a better water supply than the surface streams that receive 
 the wash of fields and meadows. 
 
228 PHYSICAL GEOGRAPHY. 
 
 In coastal regions ground water may flow forth as 
 springs directly into the sea, either on a sloping beach 
 near low-tide level, or at the bottom off-shore ; there they 
 sometimes have a current so abundant as to supply a col- 
 umn of fresh water that ascends through the heavier salt 
 water to the surface. 
 
 When a sloping coastal plain ends in a low bluff descend- 
 ing to a beach, fresh water may generally be found by dig- 
 ging a few feet beneath the base of the bluff. It is supplied by 
 the slow-creeping sheet of ground water on its way to the sea. 
 
 It is possible that feeble off-shore springs may rise into 
 sea water of a temperature less than 32°. The spring water 
 may then be frozen at the sea bottom. " Ground ice," some- 
 times noticed by fishermen to rise from the shallow sea 
 bottom in winter, may be thus explained. 
 
 Artesian wells, or deep borings to water-bearing strata 
 several hundred feet beneath the surface, are important 
 sources of water supply in many regions. They have been 
 described under coastal plains. It is essential that the water- 
 bearing strata should reach the surface and receive their rain- 
 fall at a higher level than that of the top of the well by which 
 they are tapped. (See Fig. 78.) 
 
 Charleston, Galveston, and many other coastal cities receive 
 much water supply from artesian wells. In eastern Mary- 
 land deep wells pierce strata that reach the surface and 
 receive their rainfall west of Chesapeake Bay ; they lead the 
 water beneath the nearly water-tight strata that floor the bay, 
 and it is still fresh when rising in the wells. Southern Wis- 
 consin and eastern Iowa have many artesian wells, supplied 
 by water-bearing strata that slope gently away from the older 
 land of northern Wisconsin. 
 
 Hot and Mineral Springs. — Ground water sometimes 
 descends deep beneath the surface, with a slow supply 
 
RIVERS AND VALLEYS. 
 
 229 
 
 from a large area, and then returns rather rapidly to the 
 surface along a rock fracture. The water may then 
 reach the surface in warm or hot springs, and bear an 
 unusual amount of dissolved mineral substances. Such 
 springs are frequently of medicinal value. 
 
 Springs of this kind are associated with disturbed rock 
 structures, as explained in con- 
 nection with the tilted block ridges 
 of Oregon. Saratoga Springs, 
 N. Y., White Sulphur Springs, 
 Va., Vichy in central France, and 
 Karlsbad in Bohemia are examples 
 of settlements determined chiefly 
 or wholly by the value of their 
 waters. These and many other 
 mineral springs occur on or near 
 lines of fracture in the earth's 
 crust. 
 
 Geysers. — In certain volcanic 
 regions the temperature of the 
 ground water may rise to or 
 above the boiling point. Steam 
 then issues with the water, often 
 in a more or less explosive man- 
 ner, and such steaming and 
 spouting springs are called gey- 
 sers. The geysers of Iceland have long been famous; 
 those of the Yellowstone Park are now the most celebrated 
 of the world. 
 
 The intermittent action of many geysers suggests that a 
 certain period of time (an hour or more) is necessary to warm 
 the new supply of water that enters the crevice of discharge 
 
 Fig. 147. —A Geyeer. 
 
230 PHYSICAL GEOGBAPHY. 
 
 after a previous supply has been blown out by steam. In tlie 
 deeper part of . the crevice the temperature of the boiling 
 point is higher than at the surface, on account of the pres- 
 sure of the water column. When the lower water readies its 
 boiling point, a great part of it is quickly converted into 
 steam, which blows the rest of the water out of the vent. 
 
 RivEES AND Valleys. 
 
 River Systems and their Parts. — A river is a stream of 
 vrater bearing the waste of the land from higher to lower 
 ground, and as a rule to the sea. A trunk stream and all 
 the branches that join it constitute a river system. 
 
 Stream is a general term, with little relation to size, Eill, 
 rivulet, brook, and creek apply to streams of small or moder- 
 ate size. River is generally applied to a trunk stream or to 
 the larger branches of a river system. 
 
 The land from which a river gathers its water and rock 
 waste is called its basin. The crest line between the 
 slopes leading to different streams or rivers is called a 
 divide. 
 
 On smooth plains and uplands there may be no noticeable 
 crest line separating the side streams of neighboring rivers. 
 Such surfaces may be described as tmdivided as to drainage. 
 Undivided areas are often found on young plains and pla- 
 teaus. When a plain or plateau is well dissected, numerous 
 subdivides are developed, as on the Allegheny plateau. The 
 rivers of vigorous mountains are sharply divided by the crest 
 lines of the lofty ridges between the deeply eroded valleys. 
 A worn-down region may have indistinct divides, as on the 
 Piedmont district of Virginia or on the uplifted but not yet 
 well-dissected plains of eastern Montana. 
 
BIVEBS AND VALLEYS. 
 
 231 
 
 Young Rivers. — The examples of land forms described 
 in earlier chapters have shown that when ja, region is first 
 raised from the sea, or when a former land surface is 
 uplifted, tilted, or folded, the streams as a rule follow the 
 lead of the land slopes, uniting here and there to form 
 rivers of larger and larger size. 
 
 Young rivers thus established proceed to cut down their 
 channels where the slope is steep enough to give them an 
 
 active current, by which the waste that they gather can be 
 washed along ; but where the slope is faint, or where they 
 enter a basin holding a lake, the streams lay down their 
 load of waste and build up the surface. 
 
 The coastal pampas of Buenos Ayres, Argentina, are nearly 
 level, but contain slight depressions that hold water in the 
 wet season, forming shallow lakes of small area. These 
 
232 PHYSICAL GEOGRAPHY. 
 
 basins appear to be faint hollows in the original surface of 
 the plain, not yet filled or drained. Their destruction is 
 slow, for the rainfall is moderate, the plains are low and 
 flat, and stream action is weak. 
 
 The St. Lawrence system, with its many lakes, falls, 
 and rapids, is a remarkable example of very immature 
 drainage. The outlet of Lake Superior is by the Sault 
 Sainte Marie (soo St. Mary). The outlet of Lake Erie is 
 Niagara, with its renowned cataract and rapids. The out- 
 let of Ontario is the St. Lawrence, with numerous rapids. 
 The lakes favor navigation, but the rapids and falls obstruct 
 it. Canals and locks have now been constructed, by which 
 the rapids and falls are passed. 
 
 The drainage of the highland of Canada between St. Law- 
 rence river and Hudson bay bears every mark of youth. 
 Lakes are very numerous and of irregular form. They 
 often have several outlets, no one stream having cut down 
 enough faster than the others to secure all the discharge. 
 The streams are frequently interrupted by rapids or falls 
 on rock ledges, in which channels are as yet cut only to 
 moderate depth. The rivers frequently split into two or 
 more channels, which reunite after wandering in independ- 
 ent courses for 10 or 20 miles across country. 
 
 This highland is a rugged, forested, and thinly populated 
 wilderness without roads. All travel is by canoes along the 
 water courses, and the canoes have to be carried past every 
 rapid and fall. The birch tree, from whose bark portable 
 canoes are made, is here as appropriate to the needs of the 
 inhabitants as the camel is to the dwellers in arid deserts. 
 
 The region of the great African lakes bears man}'" marks 
 of youthful drainage. The lake basins here indicate a break- 
 ing or warping of the earth's crust, like that in Arizona and 
 southern Oregon. The adjacent plateaus are bordered by 
 
RIVERS AND VALLEYS. 233 
 
 ragged fault cliffs. The Nile, flowing north from Lake Vic- 
 toria Nyanza, and the Shire, flowing south from Lake Nyassa, 
 are strong rivers of powerful current, descending over falls 
 and rapids, very busy in the work of deepening their valleys 
 and draining the lakes. 
 
 By long-continued action the path of a river will in 
 time be everywhere worn down or built up to such a slope 
 that the current will be just strong enough to carry the 
 load of waste that it receives. Such a river might be 
 described as passing from youth to maturity. 
 
 Lakes may be generally taken to indicate a youthful 
 drainage system, as in the examples just given. In time 
 they will be destroyed, partly by filling with the waste 
 that is brought by the inflowing streams ; partly by the 
 deepening of the outlet valley. Lakes should therefore 
 be regarded as only temporary features in the long life of 
 the river system to which they belong. The rivers may 
 remain long after the lakes disappear. 
 
 The distribution of lakes has already been considered in 
 connection with various land forms. The plains of western 
 Siberia and of Buenos Ayres possess lakes because they are 
 young lands. The depressions between the tilted lava blocks 
 of southern Oregon hold lakes because enough time has not 
 yet passed to enable the streams to fill and drain their basins. 
 Lava flows obstruct streams and for a time hold back lakes. 
 Lakes of other kinds will be described later. 
 
 As water stands nearly still in lakes, the arrangement 
 of its layers depends on their temperature. Fresh water 
 is densest at 39°. If warmed or cooled from this tem- 
 perature, it expands and becomes less dense. In freezing 
 it expands still more, and the ice floats buoyantly. 
 
234 PHYSICAL GEOGBAPHY. 
 
 In warm climates the lowest temperature of a lake sur- 
 face in the cool season determines the temperature that pre- 
 vails in the deep water through the year. In cool or cold 
 climates the deep water of large lakes is seldom colder 
 than 39°. The surface layers may be colder than 39° in 
 winter and warmer in summer. 
 
 The surface water of a lake will not freeze over unless the 
 whole water body can be reduced at least to 39°. Por this 
 reason small lakes may freeze, while large lakes near by 
 remain open through the winter. 
 
 Lakes act as filters to the streams that enter them, 
 decreasing their velocity and causing the stream-borne rock 
 waste to settle ; thus deltas are formed at the inlets, and 
 the lake bottom is strewn with fine waste or silt. 
 
 Lake Geneva receives the turbid Rhone at its east end, 
 where a large delta, 20 miles long, has grown a mile forward 
 since Eoman times. The lake bottom is a plain- of fine silt. 
 The Rhone at the outlet is wonderfully clear. 
 
 Lakes act as regulators of the discharge of their outflow- 
 ing rivers ; for the level of the lake changes little, whether 
 the inflowing -streams are flooded or low ; and hence the 
 outlet river has a relatively constant volume. 
 
 The Ohio without lakes and the St. Lawrence with five 
 great lakes are strongly contrasted in this respect. The 
 latter has no great floods. The floods of the former may rise 
 50 or 60 feet, spreading to 10 or 20 times the usual width of 
 the river. 
 
 Falls and Rapids. — It may sometimes happen that a 
 breaking or bending of the land surface makes a slope 
 steep enough to produce rapids or falls in the streams that 
 run from the higher to the lower area. 
 
BIVERS AND VALLEYS. 
 
 235 
 
 It is probable that falls were formed in the Colorado Hiver 
 at the points where it was crossed by the faults that sepa- 
 rated the uplifted plateau blocks. These falls must have 
 been rapidly worn away after each of the many slight move- 
 ments by which the blocks were probably displaced. 
 
 When a river is by any process turned across a new 
 path, it falls dov^^n any descending slopes that occur on 
 its course. Thus Niagara, v\^hen first taking its present 
 
 Fig. 149. — Falls of the Tellowstone Eiver. 
 
 course, fell over the blufC of the Niagara upland ; since 
 then the fall has cut back a gorge about seven miles long. 
 The larger or Canadian fall is now retreating two or three 
 feet a year at its middle. 
 
 The falls of the Yellowstone Eiver are of similar origin. 
 They now occur at the head of a deep canyon cut by the river 
 in the process of deepening its course. 
 
236 
 
 PHYSICAL GEOGRAPHY. 
 
 While a river is engaged in deepening its valley, it 
 often flows from a stronger to a weaker rock structure. It 
 will deepen the valley much more quickly in the latter 
 than in the former, and a rapid or fall will be formed on 
 
 Fig. 150. — Diagram of Torrent with Falls 
 and Reaches. 
 
 the slope produced between the two. Falls of this kind 
 are numerous, especially in dissected plateaus and in lofty 
 mountains. 
 
 In passing from old-land rocks to the weak layers of a 
 coastal plain a river develops rapids of moderate slope, as 
 has already been explained. 
 
 While the channel of a river is interrupted by many 
 rapids and falls, it is more serviceable as a source of water 
 power than as a waterway for large vessels. In the course 
 
RIVERS AND VALLEYS. 237 
 
 of time the rapids and falls will be worn down to an even 
 slope with the rest of the channel. A large river and its 
 branches in this condition permit the entrance of river 
 boats far inland. 
 
 The falls in the lower course of the Kongo indicate an 
 uplift of its basin so recent that even that great river has not 
 yet been able to wear the falls away. The Kongo has there- 
 fore been less available for exploration and commerce in 
 Africa than the Amazon and the Mississippi have been in 
 America. 
 
 Graded Rivers. — A stream wears down its course on 
 each weaker structure with reference to the next down- 
 stream harder structure, as in Fig. 160. It thus comes 
 to be divided into smooth reaches and plunging rapids or 
 falls. Many rivers in New England are in this condition. 
 The slope of a stream on a smooth reach is just sufficient 
 to give it a velocity by which it can wash forward its load 
 of waste. This part of the stream is then said to be 
 graded. 
 
 Rivers with reaches and falls furnish abundant water 
 power for factories, and hence manufacturing cities grow 
 up along them. Manchester, Lowell, and Lawrence on the 
 Merrimac, Eochester on the Genesee, Minneapolis on the 
 Mississippi, and many other cities are examples of this 
 kind. 
 
 When a river has been undisturbed by deformation of 
 its basin for a long period of time, few falls remain to 
 interrupt its course, and its graded reaches become longer 
 and longer. It is in this well-established condition that 
 many large rivers of the world are found. 
 
238 PHYSICAL GEOGRAPHY. 
 
 In vigorous mountains, where many successive uplifts 
 occur, even the large rivers are hardly able to grade their 
 courses during the pauses between the uplifts ; the small 
 branches are kept in a torrential condition. Only when 
 the last uplift was long ago, as in subdued mountains, 
 can the streams develop well-graded courses. 
 
 It is only in streams where valleys are not yet graded that 
 the observer may expect to see the stream at work deepening 
 its valley. No such action is perceptible in graded streams. 
 
 When a graded condition is reached in even the smaller 
 streams, the slope will be steepest near the headwaters 
 and least near the river mouth ; thus the profile of a well- 
 developed river is a curve of decreasing slope from head 
 to mouth. 
 
 The large volume of the lower part of a river enables it to 
 run rapidly even on a gentle slope. Its load is relatively 
 fine-textured and easily carried, having been ground finer 
 and finer while washing down from the upper valleys. 
 Every thread of the river current does its part of the work 
 of washing the load towards the sea. Under these favoring 
 conditions a faint slope will enable the river to do its work. 
 
 The small volume of a headwater stream permits friction 
 with the banks and bed greatly to retard its current. The 
 load that it receives from the valley slopes is relatively 
 plentiful, coarse, and difficult to drag along. The only 
 way in which a small stream can do its work under these 
 unfavorable conditions is by maintaining a steep slope. 
 
 A swift headwater stream ordinarily has so little fine 
 waste to carry that its water is clear ; the coarser waste is 
 dragged along its bed. Only at a time of flood does it become 
 turbid. The slow-moving waters in the lower course of a 
 flat-graded river gather so much fine silt that they are nearly 
 
BIVERS AND VALLEYS. 239 
 
 always somewhat turbid from suspended and slowly settling 
 sediments. 
 
 Water moves so easily that large rivers assume very faint 
 slopes ; the lower Mississippi has a descent of only 2 or 
 3 inches to the mile, yet it bears along a vast amount of 
 rock waste : 6700 million cubic feet of suspended silt, 750 
 million of silt dragged along the bottom, and 1400 million 
 of mineral substances in solution every year. 
 
 When a river system is found to possess graded valley 
 floors extending without break far up toward the heads of 
 its many branches, it must be concluded that the streams 
 have long been at work to produce so remarkable an 
 adjustment between volume, load, and slope. This beau- 
 tiful adjustment is one of the best proofs that valleys are 
 carved by the streams that drain them ; for by no other 
 process could the adjustment be produced. 
 
 The Development of Valleys. — While a young river is 
 deepening its valley, the valley sides are steep and the 
 valley bottom is no wider than the river channel. At 
 such a time the valley floor offers no attraction to settle- 
 ment, as it affords no level ground for roads or villages 
 near the river ; if built in such a valley, they must perch 
 on the side slope. If the valley is deep, it may act as a 
 barrier between the uplands on either side. 
 
 The dissected plateau known as the Mesa de Maya in 
 southern Colorado, fronting the Rocky mountains, affords 
 many examples of narrow young valleys in their relatively 
 inaccessible and unattractive stage. 
 
 Floods have little room to spread in a steep-sided valley ; 
 hence they rise rapidly on the valley walls, even 30 to 50 feet 
 in a day or two. Thus hemmed in a valley, the flood flows 
 
240 
 
 PHYSICAL GEOGRAPHY. 
 
 rapidly and sweeps away all obstacles, gradually subsiding as 
 its supply of water lessens. 
 
 It is for this reason difficult to maintain road bridges across 
 the streams of the Allegheny plateau ; the great expense of 
 building strong and high bridges cannot be borne by the scat- 
 tered population. The streams are therefore commonly crossed 
 by fording. At time of high water, travel is interrupted. 
 
 Thus far it has been implied that an active stream cuts 
 its channel directly downward and not at all sideways. 
 
 But at every bend a 
 
 stream tends to cut more 
 on the outer than on the 
 inner bank; hence as it 
 cuts down it also cuts 
 outward. 
 
 A perfectly straight 
 stream might cut verti- 
 cally downward. As the 
 valley sides wasted, the 
 valley would become wider 
 at the top, but not at the 
 bottom, as in Fig, 151 
 (a, b, c). 
 
 If no wasting of the 
 walls occurred, the trench 
 
 Fig. ISl.-Diagram of a straight VaUey. Q^f^ ]jj g, crOOkcd Stream 
 
 would slant outward at every turn, as in Fig. 152 (a). This 
 is sometimes seen to a slight degree in narrow gorges or 
 chasms, for the fastest current is not in mid-channel, but 
 runs near the outside of every turn ; hence there is more 
 wearing on the outer than on the inner side of the stream. 
 The valley walls waste while the trench deepens. When 
 grade is reached, the walls will have flared open ; but they 
 
RIVERS AND VALLEYS. 
 
 241 
 
 will be steep on the out- 
 side of every curve where 
 the stream has under-cut 
 the valley wall, as in Fig. 
 152 (b). Unsymmetrical 
 valley sides are formed in 
 this way ; sloping spurs 
 enter each curve opposite 
 cliff-like bluffs, and the 
 belt of country occupied 
 by the turns of the river 
 is broader than at first. 
 
 The Development of 
 Meanders. — When a 
 rivei" has graded, its val- 
 ley, it almost ceases to 
 cut dov^^nward, but it may- 
 still wear on the outer 
 bank of every turn, and 
 thus contmue to broaden 
 the belt that its valley 
 floor occupies. At the 
 same time the turns tend 
 to become smooth curves 
 of regular form, better 
 adapted to the regular 
 movement of the river. 
 
 - As- the outer bank of 
 a curving channel is cut 
 away, the inner bank is 
 filled up to flood level 
 with rock waste from 
 
 Fig. 152. — Diagrams of a Crooked Eiver widening 
 its Valley, 
 
242 
 
 PHYSICAL GEOGRAPHY. 
 
 further up stream. A strip of flood plain is thus developed 
 on the inner side of each curve, as in Fig. 152 (c); first 
 on one side and then on the other side of the river. 
 
 The north branch of the Susquehanna follows a deep and 
 winding valley through the Allegheny plateau in northern 
 Pennsylvania. It has begun to develop strips of flood plain 
 at the base of its sloping spurs ; steep cliffs rise above the 
 opposite river bank. The Osage river has worn an extremely 
 
 crooked valley in the 
 uplands of central Mis- 
 souri, and it is just be- 
 ginning to form narrow 
 strips of flood plain. 
 
 With continued ac- 
 tion the river con- 
 sumes more and more 
 of the spurs that enter 
 its cui'ved course, as 
 in Fig. 152 (^,e). In 
 time it obliterates 
 them, as in Fig. 152 
 (/). Then an open 
 flood plain is formed on which the river takes such a 
 curved course as suits its volume, with only occasional 
 constraint by tlie valley walls. The narrower the original 
 belt of turning, the narrower the flood plain at this stage 
 of development. 
 
 The lower Missouri has a valley floor about as broad as its 
 belt of curves. Villages grow on the uplands above points 
 where the river flows against the valley walls. The valley 
 
 Fig. 153. — Contour Map of the Missouri River Valley. 
 
BIVJEES AND VALLEYS. 243 
 
 of the Ohio above Cincinnati now retains only the blunt 
 remnants of the spurs that once entered its turns. 
 
 If a stream has a large load of coarse rock waste, its 
 graded flood plain must be relatively steep (a descent of 
 from 5 to 20 feet or more a mile). In this case the stream 
 does not turn far aside from a direct course along the flood 
 plain; but it is constantly embarrassed by the formation 
 of bars and islands of gravel and sand, splitting its current 
 into many shifting channels. 
 
 The Platte, fed by branches rising in the Rocky mountains 
 and gaining much waste from the weak strata of the Great 
 Plains, requires so steep a slope that it cannot cut a deep 
 valley, although the Plains in the upper part of its course are 
 high above baselevel. The river is like a braided network 
 of many channels. ' Many rivers flowing from the Alps to the 
 lower surrounding country are of this kind ; gravel bars and 
 islands lie between their divided channels. 
 
 If the waste borne by a river is of very fine texture, the 
 flood plain will have a very gentle grade, and the valley 
 ^will be cut down close to sea level. The slope down the 
 valley is then so faint that the river easily turns aside from 
 a direct course on its broadened flood plain, and in this 
 way (whatever its original course) develops a system of 
 serpentine curves or meanders, as in Fig. 152 («,/). 
 
 The Meander, a serpentine river of Asiatic Turkey, has 
 given name to this river habit. 
 
 On a nearly level flood plain any accidental obstacle may 
 divert a stream from a direct course and turn its current 
 toward one bank or the other. Thus turned, its wandering 
 will be increased by constantly cutting away its outer bank. 
 
244 
 
 PHYSICAL GEOGRAPHY. 
 
 Even if nearly straight in the beginning, it must come to 
 meander on a flat flood plain. 
 
 The size of the meanders increases with the volume of the 
 stream. A meadow 
 brook may swing 
 around curves meas- 
 uring only 40 or 50 
 feet across. The 
 curves of the lower 
 Mississippi are from 
 3 to 6 miles across. 
 The flatter the flood 
 plain, the greater the 
 arc of the meander 
 turning. The Koros 
 (Fig. 154), on the Plain of Hungary, has its meanders remark- 
 ably developed. 
 
 Fig. 154. — A Meandering Kiver on the Plain of Hungary. 
 
 Broad Valleys. — Wherever a meandering river swings 
 against its valley walls, they will be slowly consumed. 
 As the meanders slowly change their course through the 
 flood plain (Fig. 152, e, /), cutting away the valley walls 
 now here, now there, the flood plain gradually becomes 
 wider than the meander belt. 
 
 The Mississippi below Cairo has opened a flood plain from 
 20 to 60 miles wide, that is, five or more times wider than its 
 meander belt. Being a river of great volume, it has rapidly 
 advanced to a thoroughly mature stage of development, while 
 its small branches on each side are still young. 
 
 Many ISTew England streams meander on the flood-plained 
 reaches between their falls. 
 
 In the fine rock waste of a broad and flat flood plain, 
 a large river changes its course rapidly, taking material 
 
BIVEES AND VALLEYS. 
 
 245 
 
 from the outer banks, where its current is strong, and 
 depositing it further down stream on the inner banks, 
 where its current is weaker. 
 
 The breadth of the meander belt would in time become 
 excessive, if the necks of the flood-plain spurs between 
 adjoining meanders were not gradually narrowed and cut 
 through, the meander around the spur being then deserted 
 for a shorter and straighter course. 
 
 Large rivers, like the Mississippi, exhibit all stages of 
 this process. An abandoned 
 meander is occupied by nearly 
 stagnant water, more or less 
 completely separated from 
 the new and shorter channel 
 by deposits of silt in the ends 
 of its arms ; in time it becomes 
 an ox-bow lake. A group of 
 well-developed meanders may 
 be transformed into a com- 
 paratively straight stretch, 
 with abandoned meanders and 
 ox-bow lakes on each side. 
 
 A continuous and deep 
 channel is maintained by a 
 river near the outer bank of 
 a meander, but on the straighter stretches between two mean- 
 ders the channel is irregular and variable, being clogged with 
 many shifting bars and shoals. It is in these parts that the 
 navigation of a meandering river like the Mississippi is diffi- 
 cult. 
 
 When a valley floor is old enough to be widened and 
 when its walls are worn back to gentle slopes, it becomes 
 much more available for human uses than when young, 
 
 Fig. 155. — Meanders of the Mississippi. 
 
246 PHYSICAL GEOGRAPHY. 
 
 narrow, and steep-walled ; but its flood plain is exposed to 
 invasion by tbe shifting cbannel, and to overflow at time 
 of high Avater. 
 
 The shifting of the channel may be checked by ]irotect- 
 ing the outer bank with stone or wood work, but this is 
 expensive. Eising floods may be held back by dikes or 
 levees built on the plain a little distance from the river 
 banks. When the levees are overtopped or breached, wide- 
 spread floods may result, such as occurred on the Mississippi 
 flood plain in April, 1897, when about 14,000 square miles of 
 the plain (two-fifths of the entire area) were under water. 
 The value of live stock and crops lost in this flood was esti- 
 mated at $15,000,000 ; many thousand people were for a 
 time driven from their homes. 
 
 In March. 1890, a strong flood in the lower Mississippi 
 broke through the levees on the left bank, forming the ■'■' isita 
 crevasse " (a break on the Nita plantation), flooding the plain, 
 carrying river silt into the shallow waters of the Gulf, and 
 ruining the oyster beds east of the delta. 
 
 Shifting of Divides. — While a river is wearing down 
 its valley to a smooth grade, ravines are worn into the 
 valley sides. The ravines gradually lengthen headwards 
 and dissect the upland surface. As their size increases 
 they may be called branch valleys. 
 
 Many of the great ravines in the walls of the canyon of the 
 Colorado are of this origin. Most of the branch valleys of 
 dissected coastal plains, as in South Carolina, and of plateaus, 
 as in West Virginia, are formed in this way. 
 
 The headward growth of branch valleys is more rapid in 
 weak than in strong rock structures. It sometimes happens 
 that a branch valley gnaws its way headward along a belt 
 
RIVERS AND VALLEYS. 
 
 247 
 
 Fig. 156 a. — Diagram of a Shifting Divide (first stage). 
 
 of weak rocks ( Tf, Fig. 156), from the deep-cut valleys of a 
 large river (i?), and taps the side of a smaller river (aS'), 
 whose valley is not 
 cut so deep. The 
 upper waters of the 
 smaller river are then 
 turned to the large 
 river, and the lower 
 course [D) of the 
 smaller river is left 
 in diminished vol- 
 ume. As this change 
 progresses, the divide 
 is shifted from its or- 
 iginal position {AB) 
 and in time takes a 
 position {AC) across 
 the smaller valley 
 above the beheaded 
 stream {B). Still 
 further changes may 
 occur later. 
 
 Fig. 156 6. — Diagram of a Shifting Divide (second stage). 
 
 The arrangement of 
 streams on belted 
 coastal plains may be 
 explained as the result 
 of shifted divides. At 
 first the rivers that are 
 
 extended from the older land across the young coastal plain 
 follow independent courses to the sea. Branch valleys grow 
 out from the several rivers along the belt of weaker strata 
 on which the inner lowland is to be worn. A branch stream 
 
 Fig. 156 c— Diagram of a Shifting Divide (third stage). 
 
248 
 
 PHYSICAL GEOGRAPHY. 
 
 Fig. 158. —Diagram of Rearranged Kiver Courses. 
 
EIVERS AND VALLEYS. 
 
 249 
 
 :N0RTH CAROLINA 
 
 Fig. 159. — Boundary of Georgia and South Carolina. 
 
 (-E, Fig. 157) of the largest river (A) lias the advantage of 
 
 the greater depth to which the main valley is worn ; in time 
 
 it captures one after the other of the smaller streams (B, C, D) 
 
 and leads them along the 
 
 inner lowland to the main 
 
 river, leaving their lower 
 
 courses (F, G, Fig. 158) 
 
 beheaded. 
 
 The western angle of 
 
 South Carolina marks the 
 
 place where the former 
 
 upper waters of the Chat- 
 tahoochee river have been 
 
 captured by a branch of 
 
 the Savannah river. In 
 
 this case the advantage 
 
 enjoyed by the Savannah 
 
 resulted from its shorter 
 
 course to the sea, in consequence of which its headwaters 
 
 were enabled to erode 
 their valleys deeper 
 than the valley of 
 the Chattahoochee. A 
 state boundary has 
 thus been determined. 
 • Further beheading of 
 the Chattahoochee by 
 the Oconee may take 
 place in the future. 
 
 The city of Toul in 
 eastern France stands 
 at a sharp turn in the 
 Moselle river, where 
 its upper waters have 
 been captured from 
 
 Fig. 160 — Outline Map of Eastern France and Western ^ 
 
 Germany. the MeUSC, tO whlch 
 
250 
 
 PHYSICAL GEOGRAPHY. 
 
 they once belonged. Another branch of the Meuse has been 
 captured by the Aisne, a member of the Seine system. . Here 
 the captures seem to have taken place because the Meuse was 
 
 delayed in deepening 
 its valley on account 
 of having to cut a 
 deep gorge in the hard 
 rocks of the Ardennes 
 highlands, further 
 down stream. As a 
 consequence the small 
 meanders of the di- 
 minished Meuse no 
 longer fit the larger 
 meanders of its 
 swinging valley, as 
 shown in Fig. 161. 
 
 Mature Rivers. — 
 When a river and 
 its larger branches 
 have destroyed tlieir 
 lakes and falls and reduced their valleys to graded slopes ; 
 when the larger streams have broadened their valley floors 
 so that they can meander freely upon them in curves 
 appropriate to their volume ; and when the growth of 
 branch streams has shifted the divides so far that no fur- 
 ther changes of importance are to be expected, the river 
 system has reached the mature stage of its development. 
 
 A river system occupies so large a region that it cannot be 
 easily pictured in the mind ; but as its different parts are 
 patiently studied, and as an understanding of their wonderful 
 relations is gradually gained, the system as a whole may be 
 
 Fig. 161. 
 
 -Irregular Course of the Meuse in its Meandering 
 VaUey. 
 
RIVERS AND VALLEYS. 251 
 
 conceived. It will then be seen to be almost as marvellous 
 as any organic forms in its well-ordered arrangement of parts 
 and in their survival by reason of natural selection. 
 
 Mature rivers accomplisli the drainage of their basins 
 and the transportation of rock waste to the sea in the most 
 active and perfect manner. There remain no undivided 
 uplands from which a great part of the rainfall may be 
 returned to the atmosphere by evaporation. The largest 
 possible share of the rainfall is shed from the well-carved 
 surface of the land, and runs off in the streams with no 
 lingering delay in lakes or undue haste in falls. No 
 hard rock ledges remain in the lower courses to delay the 
 deepening of the upper valleys. Everywhere the waste of 
 the land is washed down the slopes to the streams, and 
 delivered in such quantity that the streams are kept work- 
 ing at their full capacity to transport the waste toward 
 the sea. 
 
 Old Rivers. — If no disturbance occurs, a maturely 
 developed river system passes by slow degrees into a 
 quiet old age. The hills waste away to fainter slopes and 
 yield less and less waste to the streams. The texture of 
 the waste becomes finer and finer. More of the waste is 
 carried in solution. As the work of carrying the waste is 
 thus made more easy, the meandering streams very slowly 
 wear their flood plains to gentler slopes, and in this way 
 always maintain a nice adjustment between their ability 
 to do work and the work that they have to do. 
 
 The extreme old age of a river system would be character- 
 ized by low and ill-defined divides between faint slopes lead- 
 ing to broad flood plains, on which the streams would meander 
 
252 PHYSICAL GEOGRAPHY. 
 
 with great freedom. An increasing share of the transported 
 "waste would be dissolved. A large amount of rainfall would 
 be lost by evaporation on the gentle slopes. 
 
 It is unusual to find an old river system. Tlie lower 
 trunks of large river systems often gain very gentle slopes 
 and free-swinging meanders, but before a correspondingly 
 advanced development is attained by all the small side 
 branches and the headwaters, movements of elevation or 
 depression generally occur with more or less tilting and break- 
 ing ; and in this way the rivers are made young again and set 
 to work at new tasks. 
 
 Revived Rivers. — At any stage of development the 
 region drained by a river may be uplifted to a greater 
 height above sea level. Then the river will at once begin 
 to cut its valley floor down to grade with respect to the 
 new baselevel. The renewed activity of such rivers sug- 
 gests that they should be called revived. One of the 
 first effects of revival and renewed dissection is to bring- 
 to life again the falls that had been worn down before the 
 region was uplifted. 
 
 The Great Ealls of the Missouri in eastern Montana occur 
 in a young valley, where the revived river is dissecting the 
 worn-down plains, now uplifted. jSTo falls could have existed 
 during the old age of the river, when it flowed across the 
 worn-down plains. The water power of the revived falls now 
 determines the site of the growing city of Great Falls, with 
 its important industrial works. 
 
 A common effect of revival is the erosion of a narrow 
 trench in the floor of a mature, well-opened valley. The 
 gorge of the Rhine, already described (Fig. 119), is an 
 example of this kind. 
 
RIVERS AND VALLEYS. 
 
 253 
 
 Kootenai river in the Rocky mountains of northern Mon- 
 tana, and. Fraser river in the mountains of British Columbia, 
 botli exhibit this combination of mature and young features. 
 The railroad that follows each valley is located on the former 
 valley floor, which now appears as a rock bench or terrace 
 above the present gorge. 
 
 Old rivers flowing across low worn-down mountains are 
 rare, but revived rivers flowing through gorges in uplifted 
 lowlands of this kind are common. The rivers of the 
 Piedmont district of Virginia (Fig. 116) are thus explained. 
 
 Entrenched Meanders. — If uplift permits a mature or 
 . old meandering river to entrench itself beneath its former 
 flood plain, its new valley will be regularly curved, instead 
 of irregularly crooked, as in its first youth. The meander 
 belt will be somewhat broadened as its curves are cut 
 down, for the river will cut outward as well as downward 
 at every turn. 
 
 The lower Seine in northwest France affords a beautiful 
 example of a narrow valley of regular serpentine curvature, 
 entrenched in the upland 
 (a worn-down plain, up- 
 lifted) of l^ormandy. 
 Above the reach of strong 
 tide, spurs of the upland 
 enter every loop of the 
 river. Nearer the mouth, 
 where rapid tidal currents 
 aid the action of the river, 
 the spurs of the upland 
 are almost obliterated, and the flood plain is broader. 
 
 The regular curves of the north branch of the Susquehanna 
 have probably been developed after the uplift of the worn- 
 down plain on ^hich the river formerly meandered. 
 
 Fig. 162. — Diagram of a Narrowed Spur. 
 
254 
 
 PHYSICAL GEOGBAPHY. 
 
 It sometimes happens that a revived river may wear through 
 
 the neck of one of the up- 
 land spurs that enter its 
 trenched course, and then 
 desert a roundabout course 
 for a more direct one (Figs. 
 162, 163). Eapids will 
 occur for a time at the 
 cut-off. The village of 
 Lauffen (Eapids), on the 
 
 Fig. 163. — Diagram of Cut-Off Spur. . ^ '^ 
 
 JSTeckar m south Germany, 
 gains water power from rapids of this kind. The former 
 course of the river is seen 
 in a meadow beautifully 
 curved around an isolated 
 hill, the cut-off end of an 
 upland spur (Fig. 164). 
 
 The Moselle in western 
 Germany (Fig. 160), sink- 
 ing its course in an uplifted 
 old-mountain plateau, has 
 a number of deeply incised 
 meanders (Fig. 165). In- 
 cised meanders and cut-off 
 spurs occur on the Alle- 
 gheny river above Pitts- 
 burg. Railroads following 
 an.incised meandering val- 
 ley often tunnel through 
 the narrow necks of the 
 spurs, thus anticipating 
 the behavior of the river 
 
 by many centuries. Fig. lei.— Entrenched Meanders of the Neckar. 
 
 Lengthwise and Crosswise Valleys. — Revived rivers 
 give a simple explanation of the origin of certain length- 
 
BIVERS AND VALLEYS. 
 
 255 
 
 wise and crosswise valleys. The former are often broad 
 lowlands with a deep soil weathered on weak underlying 
 rocks. The latter are 
 steep-sided gorges 
 cut in rugged, hard- 
 rock ridges or high- 
 lands. 
 
 For example, the 
 Delaware river gath- 
 ers many branches 
 from the open inner 
 valleys of northeast- 
 ern Pennsylvania, 
 and escapes by a deep, 
 narrow notch, called 
 the Delaware Water- 
 gap, in Kittatinny 
 mountain, at the 
 northwestern corner 
 of New Jersey. 
 
 In such cases the 
 rivers had their pres- 
 ent arrangement be- 
 fore the valleys were 
 excavated, when the 
 whole region stood 
 lower than now and a broad lowland spread far and wide 
 at about the level of the ridge crests and highland sum- 
 mits of to-day, as in Fig. 166. After the elevation of the 
 region, all the revived rivers began to wear down their 
 valleys. No branch stream could cut down faster or 
 deeper than the larger river that it enters. The inner 
 
 Fig. 165. — Entrenched Meanders of the Moselle. 
 
256 
 
 PHYSICAL GEOGRAPHY. 
 
 lengthwise streams could not deepen tlieir valleys faster 
 than the crosswise valley was deepened by the trunk river. 
 
 But the inner valleys 
 widen with relative 
 rapidity on their weak 
 rocks, and in time 
 become broad open 
 lowlands, while the 
 outlet valley still 
 
 Fig. 166. — Transverse and Longitudinal streams. vetaiTlS f\ O'OT'P'P-like 
 
 form in the resistant rocks which now stand up as a ridge 
 or belt of highlands, 
 as in Fig. 167. 
 
 This explanation 
 applies to the Susque- 
 hanna, cutting gaps in 
 the Allegheny ridges, 
 and to the Potomac, 
 
 cutting a deep passage ^'S. 167. -Transverse and Longitudinal Valleys. 
 
 in the Blue Eidge at Harpers Ferry, and draining the length- 
 wise Shenandoah valley in Virginia (Fig. 117). 
 
 Lakes in Warped Valleys. — In regions of relatively 
 active disturbance, like vigorous and growing mountain 
 ranges, the movements of the earth's crust may warp or 
 deform the surface so that one part of a valley is depressed 
 and another, further down stream, is elevated. A lake 
 will then be formed in the depressed part of the valley. 
 
 The basins of the larger lakes around the Alps are best 
 explained as warped valleys. Some of them are so deep that 
 the bottoms lie below sea level. In all examples of this kind 
 
RIVERS AND VALLEYS. 
 
 257 
 
 the lake must be regarded as short-lived compared to the 
 mountains around it. The inflowing streams form deltas at 
 
 Fig. 168. — Watergap of the Susquehanna in North Mountain, Pennsylvania. 
 
 the shore, and furnish fine silt with which the bottom is 
 strewn. The outflowing river cuts down its valley, and 
 lowers the level of the lake. In a short time, compared to 
 
 Fig. 169. — Contour Map of the Susquehanna Watergap in North Mountain, Pennsylvania. 
 
258 PHYSICAL GEOGRAPHY. 
 
 the life of the mountains, the lake will be destroyed, and the 
 river will resume its steady flow. 
 
 Antecedent Rivers. — At any stage in the history of a 
 river a tilting or uplifting movement of the earth's crust 
 may tend to reverse the slope of a part of its valley. If 
 the movement is too rapid for the river to overcome, its 
 current will be turned away to a new path, following the 
 slope of the uplifted surface. 
 
 This is usually the case, as has been shown in the moun- 
 tains of Oregon and Nevada, in the Black Hills dome, and in 
 the Jura arches. In lofty mountains of vigorous growth the 
 main range is usually the divide between river systems that 
 flow away to the lowlands on each side. 
 
 It may, however, sometimes happen that a large river is 
 powerful enough to maintain its path by cutting down the 
 uplifted part of its valley, and then it will not be displaced. 
 As such a river existed antecedent to the disturbance of 
 its basin, it may be called an antecedent river. 
 
 The Kanawha river has preserved its course through the 
 plateau of West Virginia in spite of the uplift by which the 
 plateau was raised 1000 feet more than the upper part of 
 the river was in Virginia and North Carolina. 
 
 Great rivers, like the Sutlej, gathered in the inner 
 valleys of the Himalaya and escaping to the plains of 
 northern India by "deep gorges, have maintained their 
 courses through the marginal ridges which have been 
 uplifted and added to the mountain system in a compara- 
 tively late stage of its history. 
 
EI VERS AND VALLEYS. 259 
 
 These rivers may therefore be called antecedent to the 
 marginal ridges. They have cut their outlet valleys down 
 as the ridges were upraised, much in the way that a circular 
 saw cuts its way through a log that is driven against it. 
 
 Before the last uplift of the plateau-like Slate mountains 
 (Fig. 119), now trenched by the middle Rhine, the river fol- 
 lowed its present path, as is shown by the trough in which the 
 young gorge is cut. It therefore appears to have maintained 
 its course in spite of an uplift across its path. It is an 
 antecedent river in this part of its length. 
 
 Engrafted Rivers. — When a region near the sea is 
 uplifted and a submerged continental shelf is laid bare as 
 a coastal plain, the rivers of the older land are extended 
 across it. It sometimes happens that several extended 
 rivers unite on their way to the sea, thus grafting upon 
 one trunk a number of previously independent river 
 systems. It is chiefly in this way that the greater 
 river systems of the world have reached their immense 
 development. 
 
 The uplift of the coastal plain that borders the Gulf of 
 Mexico has engrafted the White, Arkansas, Eed, and Tennes- 
 see rivers on the extended trunk of the Mississippi, whose 
 total drainage area now measures over 1,240,000 square miles. 
 
 By similar grafting the great rivers of Brazil have been 
 united with the lower trunk of the Amazon, giving it a basin 
 of 2,500,000 square miles. A further uplift would probably 
 make the Tocantins a regular member of the same system, to 
 which it is now imperfectly attached. 
 
 When large engrafted rivers grade their courses (and 
 this they do almost as fast as the new land is raised before 
 them), they become of importance as navigable waterways, 
 
260 
 
 PHYSICAL GEOGRAPHY. 
 
 reaching far into the interior of their basin. The navi- 
 gable rivers of the ^Nlississij^pi and Amazon systems 
 measure many thousand miles in length. 
 
 Dismembered Rivers. — When the sea advances on a 
 depressed region, the lower valley of a river system may 
 
 be submerged, forming an 
 estuar}* or bay. and leav- 
 ing the river branches to 
 enter the sea as independ- 
 ent river systems. The 
 entrance of navigable 
 arms of the sea far into 
 the lands nmj compen- 
 sate more or less full}- for 
 the drowning of the lower 
 varley floors, as in the 
 case of the St. Lawrence. 
 
 The small rivers that 
 enter Xarragansett bay, 
 E. I., f orined branches, be- 
 fore submergence, of what 
 may be called the Narra- 
 
 Fig. 170. -Map of Narragansett Bay. ganSCtt river SyStcm. All 
 
 the rivers of eastern Virginia and inner Maryland were 
 once united in a trunk river that flowed across what is now 
 part of the continental shelf, before its larger valleys were 
 drowned to form Chesapeake bay and the Potomac estuary 
 (Fig. 117). 
 
 A T L A 
 
 Example for Review. — The Hudson river drains a broad 
 interior valley, a part of the great lengthwise valley of the 
 
RIVERS AND VALLEYS. 
 
 26] 
 
 Appalachian mountain belt, occupied by farms all along 
 its extent. At Newburgh the river leaves the broad 
 valley and enters a deep steep-sided gorge in its famous 
 passage through the Highlands of southeastern New York, 
 an extension of the uplifted old-mountain plateau of 
 southern New Enpiand. 
 
 Fig. 171. — The Hudson River, looking North from West Point. 
 
 The difference in the dimensions of the broad and narrow 
 parts of the Hudson valley is an indication of the difference 
 in the ability of the underlying rocks to resist weathering. 
 The broad lengthwise valley was worn down no faster than 
 "the narrow crosswise gorge through which it is drained ; 
 but it widened much faster than the gorge because its rocks 
 are weaker than those of the Highlands. The waste from 
 the broad valley drained by the Hudson has been carried, 
 grain by grain, through the narrow gorge. 
 
 The large volume of the Hudson below Albany is due, 
 not to the rainfall on its basin, but to a moderate depres- 
 sion of the valley bottom beneath sea level, whereby it has 
 been drowned to a navigable depth. The former prolon- 
 
262 PHYSICAL GEOGRAPHY. 
 
 gation of the valley, excavated across the continental shelf 
 when the region stood higher, has been traced by sound- 
 ings for more than 100 miles off shore. The navigable 
 waters now entering through the Highlands have been of 
 great commercial advantage to New York city, whose 
 history must have been very different if the Hudson has 
 been as shallow in the Highland gorge as the Potomac is 
 in its gorge through the Blue Ridge below Harpers Ferry. 
 
 The lower branches of the Hudson are, strictly speaking, 
 independent rivers, now dismembered by the submergence of 
 the valley that was excavated by the trunk river of the system 
 to which they once belonged. 
 
CHAPTER X. 
 THE WASTE OF THE LAND. 
 
 Comparison of Waste Streams and Water Streams. 
 
 Much attention is given to the forms assumed by the 
 waters that flow from the lands to the sea. Surface and 
 ground water, springs, brooks, and rivers, falls and lakes 
 have thus been treated. A good share of attention should 
 also be given to the forms assumed by the waste of the 
 land on the way to the sea, from their beginning in the 
 layers of soil produced by the weathering of the rocky 
 structures of the earth's crust to their end in layers of 
 sediment spread upon the sea floor. 
 
 The movement of land waste is generally so slow that 
 it is not noticed. But when one has learned that many 
 land forms result from the removal of more or less waste, 
 the reality and the importance of the movement are better 
 understood. It is then possible to picture in the imagi- 
 nation a slow washing and creeping of the waste down the 
 land slopes ; not bodily or hastily, but grain by grain, 
 inch by inch ; yet so patiently that in the course of ages 
 even mountains may be laid low. 
 
 There are many resemblances between the movement of 
 water streams and of waste streams. Water flows along 
 stream and river channels, more rapidly at the surface, 
 more slowly at the bottom ; it is here delayed in lakes, 
 there hurried down rapids. Land waste may be thought 
 
264 
 
 PHYSICAL GEOGRAPHY. 
 
 of as moving in streams and sheets down every hillside 
 and along every valley, more rapidly at the surface of the 
 ground, more slowly at a depth of several feet ; more 
 
 Fig. 172— Rock Waste on Mountain Slopes. 
 
 rapidly on steeper slopes, more slowly on plains. The 
 shape of the land surface and its usefulness as a home 
 for man depend in no small degree on the character of 
 the sheet of waste with which it is clothed. 
 
THE WASTE OF THE LAND. 265 
 
 Flowing streams of water are valuable in many ways, as 
 affording water supply, water power, and water transpor- 
 tation. Creeping sheets and streams of waste are of even 
 greater value, for upon their surface the most useful plants 
 
 (lIlLmi. 'J_L/ VlAiiklL "Uih'iAgffJ\1l)lMi'iiftfl(';, iili'i 
 
 Fi' 173 — ^ LaL- "^loo'- Plain 
 
 grow, and upon plants all the higher forms of animal life 
 depend, directly or indirectly, for food. Many human 
 industries and arts are dependent upon the plants that 
 grow upon the slow-moving sheets and streams of waste. 
 
 The Forms Assumed by the Waste of the Land 
 ON THE Way to the Sea. 
 
 The Formation of Soil. — The decay of the rock crust 
 of the earth under the attack of the weather has already 
 been described as a characteristic of the lands. Nearly all 
 parts of the land would be covered with a sheet of waste 
 many feet deep, and bare ledges would be almost unknown, 
 if it were not for the movement of the waste after it has 
 been loosened. 
 
 Many processes aid in the production of rock waste. 
 Changes of temperature through day and night, in summer 
 
266 PHYSICAL GEOGRAPHY. 
 
 and winter, cause small movements in solid rock, and aid in 
 opening minute fractures near the surface. Water in rock 
 crevices expands as it freezes, and thus helps to wedge apart 
 adjacent blocks. 
 
 Most rocks suffer chemical changes under the action of 
 water and air, and as a rule these changes aid decay and 
 crumbling. The changes may go on as deep beneath the sur- 
 face as water and air can penetrate. They are delayed or 
 stopped when the ground water is frozen or wanting. They are 
 aided when the ground water carries down with it the products 
 of decomposing vegetation from the surface. Hence deep rock 
 decay is less active in frigid or arid than in moist torrid climates. 
 
 Where the land surface is well covered with its own 
 waste, a quarry {Fig. 59) or railroad cut may exhibit the 
 gradual change from the solid rock beneath to the fine 
 waste at the surface. While the rock is only divided into 
 large blocks by fine cracks or joints here and there, a 
 cubic inch of waste at the surface may be subdivided into 
 millions of minute particles. If plants have long grown on 
 the waste, it is darker near the surface than below, and the 
 darker part is then commonly called soil. 
 
 Soil is generally understood as including a share of vege- 
 table matter with rock waste, but some soils contain no 
 vegetable matter. 
 
 Some rocks may be slowly dissolved by water. Limestone 
 is the most important of these, and the origin of sinks and 
 caverns by solution has already been described. As the lime- 
 stone weathers and the soluble parts are slowly carried away, 
 much of the insoluble parts of the rock remain ; thus it may 
 happen that a blue limestone is covered with rusty clay waste. 
 A foot of the clay may represent 10 or 20 feet of rock. If the 
 clay is stripped off, the limestone is sometimes found etched 
 into curious irregular forms. 
 
THE WASTE OF THE LAND. 267 
 
 Where rock waste is formed on a slope, its finer particles 
 at the surface are washed down a little by the run-off of 
 every rain. Besides this the whole mass slowly creeps 
 down the slope, advancing faster at the surface and more 
 and more slowly beneath. 
 
 Every change of condition between cold and warm, dry and 
 wet, melted and frozen, that causes a gain .or loss of volume 
 in the rock waste aids its slow movement down hill. With 
 countless minute changes, every particle is led, slowly but 
 surely, from higher to lower ground. 
 
 The growth and decay of plant roots aid the downward 
 creeping of the waste. Earthworms, ants, and various bur- 
 rowing animals bring the smaller particles of waste to the 
 surface, and thus promote weathering and washing. 
 
 All causes of movement are greatest near the surface ; 
 hence the outer part of the waste sheet moves faster than 
 the under part. As gravity is more effective on steep than 
 on flat surfaces, the waste creeps faster on hillsides than on 
 nearly level plains. In both these respects waste streams 
 resemble water streams. 
 
 On surfaces of very gentle slope, such as plains of 
 moderate relief, the waste is removed so slowly that it 
 becomes unusually deep. The deeper the sheet of waste 
 becomes, the less active is the attack of the weather on the 
 under rock, and the slower the waste increases in depth. 
 The surface particles become finer and finer the longer 
 they are exposed; the finer they are, the more easily they 
 wash and creep away. In this way a balance may be 
 struck between slow removal at the surface and slow 
 production at the base of the waste. 
 
 It thus appears that plains favor human occupation, not 
 only because they may be easily traversed, but also because 
 
268 PHYSICAL GEOGRAPHY. 
 
 they usually possess a fine and deep soil. Fineness of 
 texture near the surface is of great advantage to many 
 plants, although unfavorable to certain kinds of trees. 
 The importance of such waste sheets to mankind can 
 hardly be overestimated. 
 
 The even surface of the lava plateau of southeastern Wash- 
 ington is covered with a heavy sheet of waste, at places 50 
 or more feet thick. Deep sections show hard black lava at 
 the base, gradually changing upwards to a yellowish decayed 
 mass, and becoming a very fine porous soil towards the surface, 
 where all traces of rock structure have disappeared. The soil 
 offers scarcely more resistance to the plow than so much meal. 
 Great wheat crops are raised upon it. 
 
 Local and Transported Soils. — Soils may be roughly 
 classified as local and transported. A local soil consists of 
 waste still lying upon or near the rock from which it was 
 weathered. A transported soil consists of waste that has 
 been carried a greater or less distance from the parent 
 rock. 
 
 In a region of local soils there may be a great difference 
 in the value of neighboring farms, according as they lie on 
 rocks that yield rich or ^ or soils. The famous Blue Grass 
 district of central Kentucky possesses a fertile soil weathered 
 from limestone. Adjoining on the south and east is a belt of 
 sandy rocks, where the soil is hardly worth cultivating. The 
 contrast in the value of the farms and in the condition of the 
 people of the two districts is very striking. The same con- 
 trast is to be seen in passing from the rich limestone soils 
 around Nashville in western Tennessee to the " barrens " on 
 the surrounding sandstones. 
 
 Meadows and valleys generally contain transported soils 
 supplied by the waste that is washed down from the adjoining 
 hillsides and from the upper part of the valley. 
 
THE WASTE OF THE LAND. 
 
 269 
 
 Transported soils usually possess a greater variety of com- 
 position than local soils, and are therefore more generally 
 suitable to varied crops. Further account of them will be 
 found under flood plains (p. 279), wind action (p. 316), and 
 glacial action (p. 335). 
 
 Rock Ledges and Cliffs. — On surfaces of steep descent, 
 such a,s occur along the fault cliffs of blocked plateaus, or 
 on the flanks of newly uplifted mountain masses, the waste 
 is rapidly moved downward, leaving the bare rock exposed 
 on the upper slopes. The steep sides of young valleys, 
 cut by vigorous streams in structures of any kind, are also 
 usually bare and rocky 
 on their upper slopes, 
 because the waste is 
 there removed as rap- 
 idly as it is supplied; 
 their lower slopes are 
 cloaked with sheets 
 and streams of loose 
 stone and gravel. 
 
 In contrast to the 
 deep and fertile waste 
 sheets of plains, the 
 steep and bare rock 
 ledges of plateaus and 
 mountains are "des- 
 erts." They are avoided ^'^- "*• ' """^ '""^ ''"^"" 
 by nearly all forms of plant and animal life. Lichens and 
 mosses may attach themselves here and there ; small plants 
 of higher order may gain root-hold in occasional crevices ; 
 lowly refugees, brute or human, may seek shelter in shallow 
 caverns beneath overhanging ledges ; but a steep and bare 
 rock surface is too sterile to attract numerous occupants. 
 
270 
 
 PHYSICAL GEOGRAPHY. 
 
 Land Slides. — Land slides from rocky cliffs may form 
 tumultuous heaps of waste beneath the cliffs, or may 
 spread smoothly along the valley floor. A slide may, in 
 its excess over the ordinary falls of small rock masses 
 from a cliff be compared to a cloud-burst flood in the 
 stream channel of an arid region. 
 
 ^L.' 
 
 gS"" 
 
 
 
 
 ^v^-:-;:^ 
 
 ^•iy,-A , ^ 
 
 "■ ■■.):^:4#i'tts^ 
 
 ^MMH^^ 
 
 pi-iSvSS^ 
 
 W 
 
 1^ 
 
 
 Wm 
 
 m 
 
 
 : : 
 
 " 
 
 W^^^^KK/U^^^^:^^*- '^S^ ^S^^l 
 
 
 J:>;;ffi^; 
 
 
 
 
 •-: ::1 
 
 M^2^ 
 
 Fig. 176. — Land Slides in the San Juan Mountains, Colorado. 
 
 Certain valleys of the Eocky mountains of southern Colo- 
 rado contain numerous slides of great dimensions. It is 
 thought that the slides may have been dislodged by earth- 
 quakes. Although soon overgrown with trees, they are easily 
 
THE WASTE OF THE LAND. 271 
 
 recognized by their hummocky form, and by their relation to 
 scarred cliffs on the overlying slopes. The slide shown in 
 the valley of Fig. 175 measures two and a half miles along 
 the mountain base. 
 
 Waste Slopes. — The rocky talus beneath the cliffs, 
 peaks, and ledges of high plateaus and lofty mountains 
 is a sheet of slowly moving waste. Its angle of descent 
 (generally from 30° to 40°, decreasing somewhat toward 
 the base) is delicately adjusted so as to strike a balance 
 between the supply and the removal of waste. 
 
 The active supply of coarse rock blocks from a high cliff 
 requires a steep slope in the talus below, for only on a steep 
 slope can the talus blocks be removed as fast as they are sup- 
 plied. A slower supply of finer waste allows the production 
 of a less steep talus. 
 
 Weathering goes on beneath the creeping talus, and the 
 waste thus supplied joins the rest in a slow movement 
 down the graded slope. An artificial cut may reveal the 
 dragged arrangement of the creeping waste sheet, the faster 
 movement of the surface parts being easily recognizable. 
 
 As mountains and plateaus become older, the peaks and 
 cliffs are more worn away and the waste sheet covers a 
 large part of the surface. It is for this reason that the 
 profiles of maturely dissected mountains present so many 
 lines of regular descent at a comparatively constant angle. 
 Only the strongest rocks still stand out in cliffs ; the less 
 resistant rocks are alreadj'^ worn back to smooth slopes, 
 almost wholly cloaked with sheets of creeping waste. 
 
 The great painters of several centuries ago sometimes rep- 
 resented mountains with fantastic and impossible outlines, in 
 which the steepness of the slopes was altogether unnatural. 
 
272 
 
 PHYSICAL GEOGRAPHY. 
 
 At that time the study of land forms had hardly begun. It is 
 still the habit in modern descriptions to exaggerate the steep- 
 ness of mountain slopes. In careful descriptions the propor- 
 
 Fig. 176. — The Slope of Pikes Peak. 
 
 tions of bare cliffs and of waste-covered slopes should be 
 accurately noted. The flanks of Pikes Peak consist in large 
 part of even waste-covered slopes, and illustrate the impor- 
 tance of this class of forms. 
 
 The cloak of rock waste on a graded mountain slope 
 weakens the attack of the weather on the rocks under- 
 neath the waste. The bare peaks and ledges that stand 
 out above the slant of the waste slope are unprotected, 
 and in spite of their resistant structure, they crumble away 
 with relative rapidity, until they are worn down to a slope 
 on which the waste sheet will lie. Hence in lofty moun- 
 tains the sharper peaks must be regarded as comparatively 
 short-lived forms. 
 
THE WASTE OF THE LAND. 273 
 
 In certain mountain ranges many peaks have an almost 
 equal altitude, differing only by a small part of their total 
 height. To an observer standing on one summit many others 
 seem to rise to about the same level, like wave-crests at sea. 
 It has been suggested that the approach to even height results 
 from the rapid weathering and destruction of the bare peaks 
 that rise to unusual heights above the slant line of the waste 
 slopes on the valley sides. The Rocky mountains and the 
 Alps present many cases of this kind. The slopes of the 
 dissected block mountains of Utah (Fig. 103) are generally 
 smoothly covered with waste, above which bare peaks seldom 
 rise to great height. 
 
 If for any reason the process of removal gain the advan- 
 tage on a waste-covered mountain side, the waste sheet 
 will be stripped away, exposing a bare rocky surface of 
 even slope. The weather will then actively attack the 
 uncovereii rock ; the weaker parts will be first hacked out, 
 changing the even slope to a ragged profile. In time a 
 new even slope will be established, and the surface will 
 be again covered with waste. 
 
 The. chief causes that lead to a stripping of a waste- 
 covered slope are : an uplift of the region and a revival 
 of the valley streams, whereby the valley is deepened and 
 the waste on the side slopes is quickly removed ; a tilt- 
 ing of the region, whereby certain slopes are made steeper 
 than before, and the forces of removal on them are 
 strengthened ; a change of climate, whereby the forest 
 cover is destroyed and the processes of washing and creep- 
 ing are allowed to remove much waste that was before 
 detained by tree roots. 
 
 When forests are extensively cut from waste-covered moun- 
 tain sides, a large part of the waste may be washed off, 
 
274 PHYSICAL GEOGRAPHY. 
 
 leaving great slopes of bare rock or of coarse stony waste. 
 Uncliecked torrents then cut gulches in the slopes and deso- 
 late the valley floors with the gravel and sand washed down 
 vipon them. Great injury has been done in this way in the 
 Alps and the Pyrenees. On some deforested mountain flanks 
 terraces have been built and trees planted to detain the waste 
 upon the slopes and to re-forest them. 
 
 It is probable that the successive processes of waste- 
 covering, stripping, and covering again may occur as many 
 times as vigorous mountains are disturbed by uplift or tilting. 
 When disturbances become less frequent, graded slopes may 
 be more continually developed ; then the more vigorous forms 
 are subdued and the old age of the mountains comes on. 
 
 As the old age of a land form is approached, bare ledges 
 decrease in size and number, rock waste is supplied less 
 rapidly, the waste-covered slopes are reduced to gentler 
 declivity, and the movement of waste upon them is 
 slower and slower. With longer exposure to the .weather 
 the surface waste becomes less stony ; and with slower 
 removal the waste cloak becomes thicker. Thus, as relief 
 decreases, a larger and larger part of the surface acquires 
 a soil suitable for cultivation; 
 
 There is a dissected upland of nearly horizontal strata 
 forming a district of gently rolling hills (an upland enclos- 
 ing an inner lowland) in southern Wisconsin, where the whole 
 surface is smoothly graded over with soil. . Hardly a ledge 
 is anywhere to be seen. The activity of the processes by 
 which the waste is supplied is everywhere equal to the activ- 
 ity of the processes by which it is urged to move down the 
 slopes. Along every downhill line the streams of waste are 
 creeping leisurely towards the valleys. But so slowly does 
 even the finer surface waste move that the district is clothed 
 with an abundant prairie vegetation, or yields a rich farm 
 harvest. 
 
THE WASTE OF THE LAND. 275 
 
 The Piedmont district of Virginia and the Carolinas, an old 
 worn-down mountain region, has a thick waste sheet with fine 
 surface soil on its flat interstream uplands. Deep cuts dis- 
 close a gradual change from firm rock, 20 to 50 feet under- 
 ground, to fine soil above, where only the least destructible 
 minerals (like quartz) remain in stony or gritty fragments. 
 
 The presence of vegetation is an important factor in 
 determining a balance between the process of waste supply 
 and removal. Hence even on surfaces of moderate relief 
 a change from grass or forest to plowed field calls for 
 constant vigilance on the part of the farmer, lest his 
 surface .soil be washed away. "Contour plowing" (fur- 
 rows running around the slopes in level lines) is then 
 recommended, so as to detain the surface wash. 
 
 If a small gully is cut in a hillside field by the run-off 
 of a heavy rain, it should be clogged with stone and brush 
 before it grows to ungovernable size. This matter is so 
 important that an illustrated chart in explanation of it has 
 been prepared for distribution by the U. S. Department of 
 Agriculture, Washington, D. C. 
 
 The Forms Assumed by Stream-Swept Waste. 
 
 Alluvial Fans of Torrents. — The waste that creeps and 
 washes down the sides of a valley is delivered to the 
 stream that follows the valley floor. The form then 
 taken by the waste depends largely on the behavior of the 
 stream. A torrent receiving much coarse waste from a 
 steep-sided ravine frequently sweeps so much of it into the 
 main valley that it cannot all be carried away by the master 
 river. The coarser part of the waste then accumulates in 
 
276 
 
 PHYSICAL GEOGRAPHY. 
 
 a cone-like form, known as an alluvial fan, spreading with 
 even slope from the ravine mouth into the main valley. 
 
 Alluvial fans have a steep slope when formed by small 
 torrents bearing a coarse and plentiful load. They have a 
 flat slope when formed by large streams with a fine-textured 
 load. They are small or wanting in very young valleys ; they 
 
 may grow to great size 
 
 
 in maturely developed 
 valleys. 
 
 As a young ravine 
 is gnawed into a lofty 
 slope, the fan at its 
 mouth may grow ac- 
 tively forward into the 
 main valley. The fan 
 then drives the master 
 river against the fur- 
 ther side of the valley, 
 where it under-cuts 
 the valley wall. The 
 fan still growing, the 
 river may be ob- 
 structed and thus re- 
 quired to spread over 
 the valley floor up 
 stream from the fan, 
 forming a shallow 
 lake, while on the 
 down-stream side the 
 river descends in rapids over the coarsest boulders brought 
 down by the torrent. 
 
 The growth of fans is well illustrated by those formed by 
 torrents entering the east end of Lake Geneva, Switzerland, 
 where excavations have discovered ruins of Eoman settle- 
 ments at a depth of 5 feet, and of the prehistoric "stone 
 
 Fig. 177. —Alluvial Fans. 
 
THE WASTE OF THE LAND. 277 
 
 age " at a depth of from 15 to 20 feet. Here fan building 
 has gone on at a rate of about 3 feet in 1000 years. 
 
 The channel of a torrent on its fan is enclosed by low 
 walls of coarse waste that is strewn on each side at time 
 of flood. The torrent is thus naturally diked. When a 
 great quantity of waste is brought from the upper slopes, 
 the channel may be choked near the head of the fan. The 
 torrent then switches off on a new course and enters the 
 main river at a new point on the margin of the fan. 
 
 Two-Ocean creek, a small stream in the Yellowstone park, 
 has built a fan that forms a part of the continental divide. 
 Sometimes the stream flows on an eastern radius that leads it 
 to Atlantic creek (Missouri-Mississippi system), sometimes on 
 a western radius, to Pacific creek (Columbia system). 
 
 In the Alps, villages are built and fields are cultivated on 
 the fans of large size. When the torrent of such a fan is 
 turned on a new course, it may flood fields and villages, caus- 
 ing much damage. A valley road traversing the fan is swept 
 away where the torrent then crosses it, while the bridge over 
 the former torrent channel is made useless. 
 
 Accidents of this sort are common in mountain regions. 
 In 1896 a stream entering a lake in Switzerland overflowed 
 its fan with a stony flood fed by a landslip in the head 
 ravine. It laid waste a strip 2 miles long and over 300 
 feet wide at the forward end, covering it with a layer of 
 stony mud 10 or 12 feet thick. The advance of this curious 
 flood was sometimes so slow that the grass on the fields in 
 front of it was saved by hasty mowing. Houses were pushed 
 out of place, a road and a railroad were buried. Por a time all 
 travel had to go by boat on the lake. The people who lived 
 on the fan had some compensation for their losses in carry- 
 ing the thousands of visitors to and from the scene of the 
 disaster. 
 
278 
 
 PHYSICAL GEOGRAPHY. 
 
 A torrent usually gives mucli ground water to the 
 loose-textured fan, and therefore decreases in volume on 
 passing out of its rock-walled ravine. The ground water 
 commonly reappears in springs near the base of the fan, 
 and the spring line is often marked by a peculiar vegetation. 
 
 Filled and Terraced Valleys. — When a young stream 
 has graded its channel, it begins to broaden its valley 
 floor and form a flood '■M^\\1\P"'\ 
 
 plain by swinging 
 from side to side, as 
 has already been ex- 
 plained. It may then 
 happen that the head- 
 waters and upper 
 branches, still gnaw- 
 ing into the uplands 
 and dissecting them 
 more and more thor- 
 oughly, bring a larger 
 load of waste down their numerous gulches and ravines 
 than the main stream can sweep down the moderate slope 
 that it has adopted. Some of the increasing load is then 
 laid down on the flood plain, steepening its slope, and 
 thus hurrying the river to a velocity that enables it to 
 carry the rest of the load. The flood plain thus grows 
 higher and builds up on the valley sides. A similar effect 
 is produced when the slope of the trunk river is lessened 
 by a warping or tilting of the region. 
 
 Fig. 178 illustrates a valley in steep mountains, cut down 
 by a strong river. By increase of load from the headwaters, 
 
 Fig. 178. —An Eroded Valley. 
 
THE WASTE OF THE LAND. 
 
 279 
 
 the river comes to be unable to carry along all the waste that 
 it receives. The valley is thus filled with a growing flood 
 plain, as in Fig. 179. The waste is here chiefly supplied 
 by the headwaters, 
 while in Fig. 177 it 
 comes chiefly from the 
 side streams. 
 
 The lower course of 
 the Missouri river 
 seems to flow on a grow- 
 ing flood plain, for its 
 alluvial deposits are 
 much deeper than its 
 channel; here the waste 
 is chiefly supplied from 
 the upper waters of the 
 main river. 
 
 Fig. 179.— A FiUed Valley. 
 
 Flood plains of gentle slope contain a deep layer of 
 fine rock waste, an excellent soil for plants. The deep 
 waste contains a large quantity of ground water. At 
 every flood a new layer- of waste is added to the surface, 
 and the finest particles sink with the water into the 
 ground. Thus the soil is naturally renewed, and its 
 fertility is long enduring. 
 
 The Eed river of Louisiana offers a remarkable illustration 
 of a growing flood plain. Its headwaters, gnawing into the 
 Llano Estacado of Texas, gather a greater amount of waste 
 than can be carried down the gently sloping valley that the 
 trunk river has . developed in Louisiana. The trunk river is 
 therefore slowly building up its flood plain. The building of 
 the flood plain is aided by the growth of the famous " Eed 
 river raft," an accumulation of many fallen tree trunks that 
 obstructs the river channel for a number of miles, dividing 
 
280 
 
 PHYSICAL GEOGRAPHY. 
 
 the current into many small channels, checking its flow, and 
 causing the waste brought from the upper valley to settle. 
 
 So rapidly does the Red river build up its flood plain that 
 its side streams cannot build up the plains in their valleys 
 
 at equal rate ; lakes, 
 therefore, gather in 
 the side valleys, like a 
 series of leaves along 
 the Red river stem. 
 
 After filling its 
 valley with waste for 
 a time, a river may 
 change its action and 
 entrench its course 
 in the built-up flood 
 plain. The part of 
 the plain then re- 
 maining above the 
 new valley floor is 
 commonly called an 
 alluvial terrace, or 
 simply a terrace (Fig. 
 181). The change 
 in the action of the 
 stream may be either 
 because the supply 
 of waste from the headwaters decreases, or because the 
 lower course of the valley is deepened, or because the slope 
 of the stream is increased by a warping of the region. 
 
 Terraces often afford excellent sites for villages, out of 
 reach of floods ; but they are generally less fertile than the 
 flood plains, for want of suflicient ground water. 
 
 Fig. 180. — Flood Plain of Red River, Louisiana. 
 
THE WASTE OF THE LAND. 
 
 281 
 
 Some of the inner valleys of the Himalaya, up stream 
 from deep gorges, have been heavily filled with waste, pro- 
 ducing plains several miles broad among the mountains. But 
 the warping that caused the filling seems to have weakened 
 or ceased long ago, for 
 the rivers have now 
 cut their outlet gorges 
 so deep that the former 
 flood plains are deeply 
 trenched, in some 
 places exposing their 
 layers of sand and 
 gravel to a depth of 
 3000 feet, and thus 
 forming gigantic ter- 
 races. 
 
 Fig. 181.— A Terraced Valley. 
 
 Waste-Filled Basins. — Where rivers have worked long 
 enough, they destroy the lakes of their youth, partly by 
 depositing sediment in the basins, partly by cutting down 
 
 the outlet ; that is, by filling and draining the lake basin. 
 The lake is then replaced by a plain watered by inflowing 
 streams from the head and side slopes, and drained by a 
 river which escapes through a narrow outlet valley, often 
 rock-walled and- gorge-like. 
 
 Lake Erie has a smooth floor covered with fine sediment. 
 When the lake waters are withdrawn by the sufficient lowering 
 
282 
 
 PHYSICAL GEOGRAPHY. 
 
 of their outlet, the lake floor will be revealed as a smooth 
 plain. 
 
 The best agricultural land in the neighborhood of Mount 
 Shasta, Cal., is found in the flat-bottomed basins, or '< meadows," 
 which represent the waste-covered floors of lakes that were 
 
 Fig. 183. — A Warped VaUey. 
 
 formed by lava-flow barriers from the neighboring volcano. 
 The discharge of some of the lakes is so recent that their 
 meadows are still too swampy for occupation. 
 
 The effect of warping movements of the earth's crust in 
 making streams lill up one part of their valley and wear 
 
 down another has 
 already been men- 
 tioned. Filled val- 
 leys and trenched 
 gorges of this 
 origin are charac- 
 teristic of lofty 
 ranges where 
 mountain growth 
 is still in progress. 
 The gorges are 
 often so steep as 
 to be impassable ; but the filled depressions are important 
 because they offer dwelling places to mountain peoples. 
 
 The upper Arkansas valley, back of the Front Eange of the 
 Eocky mountains, is a warped basin, floored by plains of waste 
 
 Fig. 184. — A Waste-Filled Basin, Southern California. 
 
THE WASTE OF THE LAND. 
 
 28J 
 
 that slope forward from the mountain sides. The river has 
 cut through the enclosing range in a deep canyon, called the 
 Royal Gorge, now followed by a railroad. In the future the 
 deepening of the canyon (where the river is now actively 
 wearing down the rocky bed) may permit the upper river to 
 dissect the basin plains ; but at present such dissection is 
 only just begun, dividing the valley into low bench-land and 
 flat flood plains. 
 
 Fig. 185. — A Plain of Mountain Waste, SontheaBtern California. 
 
 At first sight a warped and filled valley of this kind 
 would he taken to mark the place of an extinct lake ; but 
 it is very probable that in many cases the warping of the 
 valley was so slow that no lake was produced, the depres- 
 sion being filled and the uplift being cut down as fast as 
 the warping proceeded. 
 
 The waste from the mountains is here detained for a time 
 in its journey to the sea, and in this respect the waste of a 
 
284 
 
 PHYSICAL GEOGRAPHY. 
 
 filled basin resembles the water of a lake. But just as the 
 lake is short-lived compared to the mountains, so the waste- 
 filled basin is only a temporary feature. As the outlet valley 
 is deepened, the journey of the waste toward the sea will be 
 resumed, and in due time it will reach its goal. 
 
 
 i^l^^jz^t^j'? 
 
 ; >?*_>*-',^^:^ '^'is.ss^^-^'^M^- -%" 
 
 
 Fig. 186. — A Meandering River, Vale of Kashmir. 
 
 The Vale of Kashmir, enclosed by the outer ranges of 
 the Himalaya in northwest India, is a famous example of 
 this kind. It is a waste plain in a broad basin, of area 
 about equal to that of Connecticut, occupying a down- 
 warped district between lofty mountains. Many streams 
 gather from the mountains and unite to form the Jhelam 
 river, which meanders across the plain (Fig. 186) and 
 escapes from the west end of the vale by a deep gorge 
 through the enclosing range. 
 
 The outlet gorge has been cut a little below the general 
 level of the plain, allowing the streams to entrench their 
 courses to a moderate depth, and thus forming many fertile 
 
THE WASTE OF THE LAND. 
 
 285 
 
 flood plains. A shallow lake (Wular) lies near the outlet, as 
 if not yet filled, or as if lately produced by renewed warping. 
 Until recent years the only access to this beautiful vale 
 was by a high pass over the outer range ; but now a road 
 leading through the gorge has been made by British engi- 
 neers. Although difficult to construct and to maintain, it has 
 greatly facilitated traffic 
 
 and trade between the vale 
 and the outer plains. 
 
 The oval plain of Hun- 
 gary, about 200 miles in 
 diameter, is a fine example 
 of a filled basin enclosed 
 by mountains. The inflow- 
 ing rivers have cut down 
 their flood plains a little 
 below the level of the grav- 
 elly marginal slopes ; but 
 they wander freely over the 
 central plain of fine silts 
 (Fig. 154). The outlet, 
 where the Danube has cut 
 the gorge of the Iron Gate 
 through the Transylvanian 
 Alps, has long been ob- 
 structed by rocky rapids, 
 recently blasted away to improve navigation. Although the 
 plain has many resemblances to the floor of a former lake 
 basin, the deposits on its surface all appear to have been 
 formed by river action. 
 
 Green river basin in southwestern Wyoming is an exten- 
 sive depression measuring over 100 miles in diameter. Its 
 heavy deposits of waste, once washed in from the surround- 
 ing mountains, are now deeply dissected ; for the outflowing 
 Green river has cut a deep canyon through the enclosing 
 Uinta mountains on the south. The formerly even floor of the 
 
 Fig. 187. — The Green River Basin, Wyoming. 
 
286 PHYSICAL GEOGRAPHY 
 
 waste-filled basin has been converted into a dissected upland, 
 with valleys sometimes 1000 feet deep. Much of the long- 
 detained waste has gone forward again on its way to the sea. 
 Being dry as well as rugged, the basin is of little value for 
 settlement, except where beds of coal attract mining or where 
 irrigation is possible in the valleys. 
 
 Flood Plains of Large Rivers. — The flood plain of a 
 large river is formed at such a slope that its gain and loss 
 of waste are about equal. Loss is caused chiefly by cut- 
 ting away the outer bank of the curving channel, where 
 the current runs fastest. Gain is caused by adding waste 
 on the inner bank of the curves, where the current is 
 slowest ; and also at time of flood when the river deposits 
 much waste on the plam near the banks of the channel, 
 where the first loss of velocity in overflow greatly decreases 
 its carrying power. The flood plain is in this way built 
 up chiefly near the river, and its surface therefore has a 
 faint slope to the right and left of the channel banks. 
 
 On the Mississippi flood plain the slope away from the 
 river is 5 or 10 feet to a mile. This is much greater than 
 the slope down the flood plain, which is about half a foot to 
 a mile. 
 
 As a consequence of the gentle slope of a flood plain 
 away from the river banks, the sides of the plain are 
 poorly drained and are often occupied by back swamps. 
 Villages on broad flood plains are frequently located close 
 to the river bank, where the plain is highest. 
 
 A large river seldom receives small tributaries while flow- 
 ing through its flood plain ; for small streams cannot enter 
 it against the side slope of the plain. Indeed, many small 
 
THE WASTE OF THE LAND. 
 
 287 
 
 streams may rise on the plain and run obliquely away from 
 the main river, joining streams from the uplands, and fol- 
 lowing the lowest available channel 
 through the back swamps. 
 
 A remarkable example of this kind 
 is seen on the Mississippi flood plain, 
 where the trunk of the Yazoo river 
 system, gathering little branches from 
 the uplands on the east and from the 
 fiood-plain slope on the west, flows 
 about 180 miles through the back- 
 swamp district, unable to enter the 
 main river. The Yazoo might pursue 
 an independent course all the way to 
 the gulf, if the Mississippi did not 
 happen at present to swing across to 
 the bluffs at the eastern side of the 
 flood plain (where Vicksburg is located 
 in order to be near the river), and 
 there take in the Yazoo. 
 
 The waste on a flood plain rests 
 for long periods after it is deposited 
 at times of river overfloM^. When 
 the plain is cut away as the river 
 channel shifts, the waste moves a 
 less or greater distance forward to 
 another resting place, wearing and weathering finer and 
 finer as it travels slowly down the valley. 
 
 Fig. 188. — The Mississippi 
 Flood Plain. 
 
 The flood plain of the middle Rhine in western Germany 
 is a fertile belt of land, occupied by a large agricultural popu- 
 lation, between forested uplands on the east and west. The 
 river has been " corrected," that is, turned from its meander- 
 ing course into a nearly straight channel ; its banks are 
 
288 PHYSICAL GEOGRAPHY. 
 
 diked so as to prevent overflow. It is possible that another 
 century may see the vast flood plain of the Mississippi thus 
 made much more available for occupation than it now is. 
 
 Stony flood plains may be formed in relatively steep valleys,, 
 if they are actively supplied with coarse waste from their head 
 and side slopes. Although washed by streams of rapid current 
 and torrential behavior, such flood plains belong in the same 
 class of forms with the fine-textured flood plains of large 
 rivers. The slope of the plains and the texture of their 
 materials are unlike ; but the fact that both are flood plains 
 formed by their streams gives them a close relationship. 
 
 Alluvial Fans of Large Rivers. — When large rivers 
 flow from mountains or plateaus to open lowlands, where 
 no valley walls enclose them, they may build extensive 
 alluvial fans of faint slope. The Merced river of Cali- 
 fornia (see M, Fig. 190) offers a good illustration of this 
 habit. 
 
 The Merced gathers much waste from its steep headwaters 
 in the Sierra Nevada. On issuing from its narrow valley at 
 the mountain base, it is free to turn to the right or to the left 
 on the broad " valley of California," a low trough between 
 the Sierra and the Coast range. Here the river has built a 
 fan of about 40 miles radius, of gravel near the mountains, of 
 fine silt farther forward. 
 
 The rain of this region falling chiefly in winter, it is nec- 
 essary to irrigate the fields for summer crops. Nothing could 
 be better adapted to the needs of irrigation than a gently 
 sloping alluvial fan ; for the river may be easily turned into 
 various channels at the head of the fan and led forward on 
 different courses, and thus distributed over thousands of 
 acres. The fan of the Merced was a cattle range under Span- 
 ish occupation in the first half of the nineteenth century ; it 
 became a wheat region in later years ; and since irrigating 
 
THE WASTE OF THE LAND. 289 
 
 canals have been constructed, it has been largely planted with 
 fruit orchards. 
 
 One of the largest alluvial fans in the world is that of 
 the Hoanglio, in eastern China. This great river, bear- 
 ing a heavy load of fine silt from the basins among the 
 inner mountains, issues from its enclosed valley 300 miles 
 inland from the present shore line, and at a height of 
 about 400 feet above sea level, and then flows to the sea 
 down the gentle slope of its extensive fan. 
 
 The great fan of the Hoangho is very fertile, and sup- 
 ports one of the densest populations of the earth ; but it is 
 subject to overflow on a vast scale, when the river suddenly 
 changes its course from one path to another, and invades 
 fields and villages on a new course to the sea. Overflow 
 is restrained as far as possible by dikes ; but the channel has 
 repeatedly been changed during the many centuries of Chi- 
 nese history. The mouth of the river has thus been shifted 
 more than 200 miles north or south. The hilly district of 
 Shantung, once an island, has been converted into a peninsula 
 by the forward growth of the great fan. 
 
 " The destruction caused by these overflows is awful beyond 
 description ; the loss of life is very great, and the destruction 
 of crops that form the means of support of millions produces 
 famine and the overrunning by starving hordes of the more 
 fortunate districts of the adjacent country. The anarchy 
 that rules in this struggle for life is almost beyond the con- 
 ception of those who inhabit lands where the population is 
 much below the capacity of the country, or which are easily 
 reached by foreign supplies." 
 
 During wars " the river has been turned to account as a 
 weapon of offence. Breaking the embankments has been 
 made to accomplish, almost instantaneously, by the destruc- 
 tion of hundreds of thousands of inhabitants, conquests that 
 
290 
 
 PHYSICAL GEOGRAPHY. 
 
 had been delayed by years of brave resistance." The flood 
 of 1887 covered an area estimated at 50,000 square miles, 
 immensely fertile and swarming with villages. The num- 
 ber of people drowned was at least a million, and a greater 
 loss followed from famine and disease caused by the flood. 
 
 River-Made Plains. — When many rivers flow forth 
 from mountain valleys upon a neighboring lowland, their 
 adjoining fans unite in a broad plain sloping gently for- 
 
 
 rig. 189. —View on River-Made Plain of Northern India. 
 
 ward from the mountain base.- This may be called a river- 
 made plain, in distinction from coastal plains, lava plains, 
 and worn-down mountain lowlands. A river-made plain 
 often occupies the depression between two highlands or 
 mountain ranges, as between the Himalaya and the 
 plateau of southern India ; it will then slope from each 
 side toward a midway depression. The streams from the 
 various fans will be gathered by a trunk river meandering 
 along the depression. 
 
THE WASTE OF THE LAND. 
 
 291 
 
 The many rivers issuing from the valleys of the Sierra 
 Nevada and the Coast range upon the " valley of California " 
 have formed an extensive plain, of which the Merced fan, 
 described above, is only a part. The successive fans are so 
 broad and fiat that their slightly convex form can' hardly be 
 recognized without the aid of surveying instruments. Nearly 
 all the streams run in shallow 
 channels but little beneath the 
 gently sloping surface of the fans. 
 The fans from the east and west 
 meet in a broad flat-floored trough. 
 
 The trunk river in the depres- 
 sion of a two-sided river-made 
 plain is pushed away from the 
 base of the higher mountains by 
 the stronger forward growth of 
 their fans. The fan of a large 
 stream may form a low barrier 
 across the path of the trunk river 
 and enclose a shallow lake. 
 
 The San Joaquin river, gather- 
 ing streams from the Sierra jSTevada 
 and Coast range in the southern 
 part of the " valley of California," 
 lies nearer to the lower mountains. 
 The upper streams of the " valley " 
 have been ponded back by the fan of King river (K, Fig. 190), 
 forming Tulare lake, a shallow water sheet with indefinite 
 marshy shores much overgrown with reeds (Spanish, tules). 
 
 Extensive river-made plains built upon Piedmont low- 
 lands are the natural accompaniment of deep valleys ex- 
 cavated in the lofty mountain background. The waste 
 
 Fig. 190. — The VaUey of California. 
 
292 PHYSICAL GEOGRAPHY. 
 
 taken from the latter has supplied the material for the 
 growth of the former. The two are found together in 
 many parts of the world. 
 
 Extensive river-made plains have been formed both north 
 and south of the Alps. On the south, the Po runs between 
 the long plain built forward from the valleys of the high 
 Alps and the shorter plain built from the valleys of the 
 lower Apennines. Many of the streams here are some- 
 what entrenched beneath the general level, having begun to 
 cut valleys in the plain they had previously built up. Near 
 the Alps the material of the plain is coarse ; rain and streams 
 sink into the ground, and the surface is relatively dry and 
 infertile. Further forward the ground water issues in numer- 
 ous springs, and the rest of the surface is very fertile and 
 densely populated. The " spring line " separates these two 
 parts. 
 
 jSTorth of the Alps the branches of the Ehine and the Dan- 
 ube are entrenched in an uplifted river-made plain that was 
 built when the region stood at a less elevation. Some of the 
 valleys are 1000 feet deep, and the former plain is here 
 reduced to a series of ridges extending forward between 
 neighboring valleys. 
 
 Deltas. — When a river enters a lake or the sea, its 
 current is checked. The finest part of the waste may 
 be swept away by waves and tides ; the rest accumulates 
 at the river mouth and builds up a new land surface, 
 called a delta, in advance of the original shore line. 
 Small deltas are characteristic of young rivers ; the longer 
 the progress of river growth without interruption by 
 uplift or depression, the larger the delta may become. 
 
 When rivers bearing fine waste enter the sea, the settling 
 of the waste is favored not only by loss of velocity, but also 
 
THE WASTE OF THE LAND. 
 
 293 
 
 NORTB PASS 
 
 by the presence of salt in the sea water, which causes sus- 
 pended sediments to settle faster than they would in fresh 
 water. 
 
 The land surface of a delta is built on the same slope 
 as that of the river flood plain further up stream, the delta 
 being only the forward part of the flood plain. 
 
 The great fan of the Hoangho may be regarded as its 
 delta, because it has been built forward into the Yellow sea 
 (so named from the color given by the river waste) ; but it 
 cannot be said that the 
 whole area of the fan 
 was once occupied by 
 the sea ; part of it 
 may have been built 
 on land. 
 
 A river frequently 
 splits into several 
 channels on the con- 
 vex surface of its 
 delta ; the outgoing 
 branches being known 
 as dist7-ibt(taries. 
 These are well exhib- 
 ited in the finger-like 
 division of the Mississippi on its outer delta (Fig. 191), and 
 in the many channels of the Ganges and the Brahmaputra on 
 their compound delta at the head of the Bay of Bengal. 
 
 The deltas of large rivers consist of fine-textured waste 
 or silt, worn during the long journey from the river head- 
 waters, and weathered during many rests in the flood plain 
 on the way. In a favorable climate deltas are very fertile 
 and attract a large population. The three densest popu- 
 
 QRAND PASS 
 =^ a SOUTHWEST PASS 
 
 JETTIES 
 SOUTH PASS 
 
 Fig. 191. — The Delta of the MisBissippi. 
 
294 PHYSICAL GEOGRAPHY. 
 
 lations of the world (outside of large cities) are in eastern 
 China, northeastern India, and northern Italy ; all on the 
 lower flood plains and deltas of large rivers. 
 
 Although attractive on account of fertility, deltas are sub- 
 ject to dangerous overflows from land and sea. Kiver floods 
 spread over them, unless kept off by extensive dikes such as 
 have been built on the above-named deltas. 
 
 Sea floods on deltas are also destructive. When low 
 atmospheric pressure and on-shore hurricane winds happen 
 to occur with a strong high tide, the sea water may rise over 
 the shore dikes and overflow great tracts of delta plain. 
 One hundred thousand people were drowned on the delta 
 plain of the Ganges and Brahmaputra, India, by a sea flood 
 during a severe storm in 1876. 
 
 The deltas or fans of torrents descending directly from 
 mountains into the sea are of coarse stony texture, relatively 
 unattractive to settlement. Many torrent deltas, the forward 
 part of stony fans, are formed at the base of mountains on the 
 coast of Japan. 
 
 The rate of growth of deltas depends on the ratio 
 between the volume of waste brought by the river and 
 the activity of the waves and currents on the shore. 
 Great rivers may build their deltas in the face of waves 
 and tides. The building of deltas by smaller rivers is 
 favored by protection from waves in bay heads and by 
 weaker tides. 
 
 The deltas of various large rivers are built in seas having 
 distinct or strong tides. At the Mackenzie delta the tidal 
 range is 3 feet ; at the ISTiger, 4 feet ; at the Hoangho, 8 feet ; 
 at the Ganges-Brahmaputra, 16 feet. 
 
THE WASTE OF THE LAND. 
 
 295 
 
 The forward growth of deltas often partly fills the 
 embayments of half-drowned mountains, as may be seen 
 in many of the fiords of British Columbia. The delta 
 plain of Fraser river is a fine example of this kind. 
 Outlying islands are sometimes tied to the mainland by 
 the forward growth of deltas. Several examples of this 
 kmd are known in the Mediterranean. 
 
 Elvers of comparatively small size build deltas in the pro- 
 tected bays of (nearly) tideless seas. Deltas are therefore 
 common in the bay 
 heads of Greece ; 
 here the partial sub- 
 mergence of a moun- 
 tainous country has 
 produced a ragged 
 shore line in a sea 
 where the tidal range 
 is small ; ma^ny of 
 the bay heads have 
 been much short- 
 ened by delta growth. 
 The sloping delta 
 plains contain a 
 large part of the 
 coastal population. 
 
 Small streams 
 may be strong 
 enough to build 
 deltas in lakes. In Lake Geneva, Switzerland, many torrents 
 have built sloping fan deltas in the quiet waters. The fans 
 are generally occupied by villages. When large buildings are 
 erected close to the water's edge, the delta margin is over- 
 weighted, and it may slip into the lake. Numerous accidents 
 of this kind have occurred. 
 
 Fig. 192. — Torrent Fan, Lake Geneva. 
 
296 PHYSICAL GEOGRAPHY. 
 
 The absence of deltas at the mouths of certain rivers is 
 frequently not so much on account of the action of tides 
 in sweeping away the river silt, as because there has not 
 been time enough to build a delta since the present posi- 
 tion of the land was taken. 
 
 The lower valleys of the Delaware, Susquehanna, Potomac, 
 and neighboring rivers are drowned, forming bays in the 
 partly submerged coastal plain of the middle Atlantic states. 
 Whatever deltas these rivers previously built are now beneath 
 the sea. Soundings in the lower Delaware bay have, it is 
 believed, discovered a drowned delta traversed by the chan- 
 nels of several distributaries. Very little delta growth has 
 yet taken place at the bay heads ; hence it must be concluded 
 that the depression of the region is recent ; it may still be in 
 slow progress. 
 
 Very large rivers may build forward their deltas in spite 
 of a slow depression of the coastal region. Thus the delta of 
 the Mississippi has actively advanced into the gulf waters ; 
 while Galveston bay on the west and Mobile bay on the east 
 indicate a moderate depression of the region, which the rela- 
 tively small rivers entering those bays (formerly valleys) 
 could not wholly counteract by delta building. 
 
 Dissected Deltas. — When a region is broadly uplifted, 
 as in the formation of a coastal plain, the deltas of the 
 former shore line will be dissected by the rivers that built 
 them. Such deltas are seldom conspicuous forms, unless 
 built of coarse waste with a steep front slope. 
 
 During the submergence in which the topmost layers of 
 the Atlantic coastal plain were deposited, the Delaware built 
 a gravelly delta at Trenton, IST. J. Since uplift, the river has 
 trenched the delta, forming terraces on each side of its new 
 valley. It is probable that many similar dissected deltas 
 occur along the inner margin of the Atlantic coastal plain. 
 
CHAPTER XL 
 CLIMATIC CONTROL OF LAND FORMS. 
 
 The Several Classes of Climatic Controls. 
 
 Direct Climatic Controls. — An earlier chapter contains 
 a brief description of tlie several zones into wliich the 
 earth's surface may be divided on account of the unequal 
 action of sunshine on its globular surface. The average 
 atmospheric temperatures prevailing in the different zones 
 are certainly among the most important geographical con- 
 trols that are exerted upon man's ways of living. The 
 distribution of rainfall has also been shown to be an 
 important agent in determining whether a region may be 
 fertile or barren, populous or deserted. Climatic controls 
 of this class, depending on the physical condition of the 
 atmosphere as to temperature, moisture, and movement, 
 act directly on plants, animals, and man, and greatly 
 influence their distribution. 
 
 Indirect Climatic Controls. — All the controls exerted 
 on man's ways of living by the various forms of dissected 
 land surfaces are, in a certain sense, indirect climatic con- 
 trols, for they result from the action of weathering and 
 washing, and these processes are in turn controlled by 
 climatic conditions. The examples of land forms thus far 
 given have been mostly taken from regions of ordinary 
 climate, neither very dry nor very cold, and with rainfall 
 
298 PHYSICAL GEOGRAPHY. 
 
 sufficient to fill all basins to overflowing. A number of 
 examples now follow in which the peculiar effects of dry 
 and of cold climates are described. It will be shown that 
 the forms of the land and the condition of its surface vary 
 greatlj'" according to their origin under an ordinary, a dry, 
 or a cold climate. 
 
 Changes of Climate. — One of the most remarkable 
 results of this division of geographical study is the discov- 
 ery that certain existing land forms have been produced 
 under climatic conditions quite unlike those prevailing 
 to-day. There are regions, now dry and barren, where 
 the marks of a former moist climate are very apparent. 
 There are others, now 'fertile and populous, where the 
 marks of a former cold climate are no less distinct. Not 
 until these curious changes in climate are recognized can 
 the great variety of land forms and the controls that they 
 exert on the earth's inhabitants be clearly understood. 
 
 Effect of Dry Climate on Streams and Rivers. 
 
 Ledges and Waste Slopes. — Certain parts of the world 
 have so little rainfall that vegetation is nearly wanting. 
 Here rock waste washes and creeps freely down the slopes, 
 not being detained by vegetation long enough to be 
 weathered to fine texture. Narrow valleys among arid 
 uplands are therefore encumbered with stones and gravel. 
 The small streams must maintain a strong slope in order 
 to carry forward their heavy load. 
 
 As a consequence, the dissected uplands of arid regions 
 possess a large proportion of bare rock ledges, such as have 
 been described in the plateaus of Arizona. Their rugged 
 
CLIMATIC CONTROL OF LAND FORMS. 299 
 
 forms must be worn to more gentle slopes before they are 
 covered with waste. 
 
 The desolate gray forms of desert mountains, like the 
 ranges of northwest Mexico (Sonora) and of northern Chile 
 (Atacama), are much less picturesque than the snowy summits 
 and forested flanks of mountains in a moister climate. 
 
 Streams of Dry Climates. — When a light rain occurs in 
 a region of dry climate, much of the water returns to the 
 atmosphere by evaporation, a large part of the remainder 
 sinks into the thirsty soil, and the run-off by streams 
 is small. Much of the ground water evaporates under- 
 ground and passes from the soil as water vapor, instead 
 of coming out in springs. When a heavy rain occurs, the 
 streams are flooded ; but the water soon runs away, leav- 
 ing the channels dry again. 
 
 The streams of dry regions are, therefore, very variable 
 in volume ; active for a while after a rain, almost or quite 
 disappearing in the long dry seasons, advancing far down 
 their, lower courses when in flood, then dwindling and 
 withering away and leaving their lower channels dry. 
 
 In the Sahara dry water courses, known as wadies, are 
 commonly used for roads, as their defiles frequently offer 
 graded ways through rocky uplands. Death by drowning 
 would nowhere be so little expected as in a desert ; but it 
 sometimes happens that a caravan, following a wady through 
 an upland, meets a down-rushing flood fed by rainfall in the 
 distance ; and before the travellers can climb the steep walls 
 of the defile they may be overwhelmed and drowned. 
 
 In parts of the Kocky mountain region, of generally dry 
 climate, heavy rains occasionally fall in summer. Then for a 
 few hours the dry channels are flooded with a rushing turbid 
 stream, that sweeps away the waste that had been washed in 
 
300 
 
 PHYSICAL GEOGRAPHY. 
 
 by lighter rains. Camping parties, pitching their tents too 
 near a channel that was nearly dry in the afternoon, may be 
 overwhelmed by a rushing flood at night. Fig. 193 illustrates 
 
 Fig. 193. — Flood in Cherry Creek, Denver, Colorado. 
 
 a sudden flood in Cherry creek, where it passes through the 
 city of Denver, Col. The channel of the creek was dry half 
 an hour before this raging torrent rose. 
 
 Streams that are supplied by springs in uplands and 
 mountains frequently diminish in volume, partly by evapo- 
 ration, partly by sinking into the ground, as they advance 
 over arid lowlands. They may wither away and disappear 
 entirely from the surface ; but their flow is usually con- 
 tinued as ground water for some distance beyond their 
 visible end. Their load of waste is spread on the surface 
 before them ; hence the lower parts of many streams in 
 arid regions build up the surface they flow upon, even 
 though high above baselevel. 
 
CLIMATIC CONTROL OF LAND FORMS. 301 
 
 Certain rivers of Argentina liave not volume enough to 
 carry them across the pampas to the sea. Rising in the 
 mountains, tliey entrench their valleys 100 feet or more 
 beneath the surface of the pampas for some distance, and 
 here are the chief settlements, such as the city of Cordoba 
 on the Primero ; then, dwindling' in volume, they flow out 
 upon the pampas, ending in marshes. 
 
 Flood Plains in Deserts. — Rivers that rise in w^ell- 
 watered regions sometimes flow across deserts on their way 
 to the sea without receiving branches for long distances, 
 and decreasing by evaporation as they advance. If the 
 rivers have developed open and accessible valleys, nearly 
 all the population of the region is gathered on their flood 
 plains. 
 
 The most famous river of this kind is the Nile, which flows 
 1000 miles without receiving a branch, except a few small 
 wet-weather streams. Its flood plain, entrenched beneath the 
 desert uplands, is about 500 miles long and from 5 to 15 miles 
 wide, broadening on the delta to over 100 miles. Here most 
 of the millions of Egyptians dwell. Their resources are 
 almost wholly agricultural, and as such depend on the annual 
 inundation of the Nile, caused by the northward movement 
 of the belt of equatorial rains in summer. The river flood 
 begins in June, usually rising 25 feet or more at Cairo in late 
 summer or early autumn. For thousands of years the fer- 
 tility of the flood plain has been maintained by the annual 
 additions of river silt, estimated to amount to 4i- inches a 
 century. 
 
 The southward course of the lower Colorado has few 
 branches for about 300 miles. Its water supply comes chiefly 
 from the mountains and high plateaus in its upper basin. 
 The sediments swept from its canyons have built a delta 
 across the depression that holds the Gulf of California. The 
 
^02 
 
 PHYSICAL GEOGRAPHY. 
 
 I II ( ) 11 N I A 
 
 CALIFORNIA 
 
 Fig. 194. — Diagram of the Colorado 
 Kiver Delta. 
 
 former liead of the gulf, thus isolated from the rest, has been 
 dried out, leaving the arid Coahuila basin in southernmost 
 California, its central part being 300 feet below sea level. 
 
 Sometimes a distributary of the Col- 
 orado, called New river, turns north- 
 west into the basin, forming a lake, 
 as in 1891. If the lake rises high 
 enough, it overflows southward along 
 the western margin of the delta, this 
 outlet being called Hardy's Colorado ; 
 but as a rule its channel is dry. 
 LOWER f ■^■"^ 
 
 On the desert slopes of the 
 
 Andes in western Peru nea,rly all 
 the population is gathered on the 
 flood plains of rivers that descend 
 from the mountains to the Pacific. 
 
 Some of the rivers, like the Piura in northern Peru, run 
 
 dry for part of 
 
 the year. When 
 
 the wet season 
 
 comes, travel- 
 lers from up 
 
 the valley are 
 
 anxiously asked 
 
 if the river is 
 
 beginning to 
 
 flow. As its re- 
 freshed stream 
 
 approaches the 
 
 town of Piura, 
 
 bands of people go out to meet it, marching back with its 
 
 advancing current and celebrating its arrival by a public 
 
 Fig. 195. — A Kiver VaUey in Desert Mountains, Peru. 
 
CLIMATIC CONTROL OF LAND FORMS. 
 
 303 
 
 holiday. All the fields and gardens of the valley are 
 watered by canals led from its channel. 
 
 Bad Lands. — When fine-textured, unconsolidated de- 
 posits, such as lake silts, suffer dissection in an arid 
 climate, they acquire an extremely irregular surface; 
 
 Fig. 196. — Bad Lands. 
 
 hence their name, bad la7ids, originally applied on account 
 of the difficulty of travelling over them. The absence 
 of vegetation allows the formation of numerous rivulets 
 when rain falls. Every rivulet carves a channel, thus 
 dissecting the surface in minute imitation of a maturely 
 dissected plateau. 
 
 The bad lands of South Dakota and Wyoming are best 
 developed near the branches of the Missouri river system ; 
 the wet weather streams here actively dissect the uplands 
 in which the larger rivers have entrenched their valleys. 
 As the rainfall is light, vegetation is almost absent and no 
 loose soil remains on the dissected surfaces ; all the loosened 
 waste is washed into the valleys of the chief rivers. 
 
304 PHYSICAL GEOGRAPHY. 
 
 During the third quarter of the nineteenth century, the 
 Sioux Indians made use of these bad-land districts as natural 
 fortresses, in which pursuit was difficult ; here were fought 
 some of the last battles in the unhappy warfare of settlers 
 and soldiers against the native tribes. 
 
 Interior Drainage Basins. 
 
 Continental Interiors. — Regions situated far inland, 
 remote from moist sea winds, receive light rainfall. In 
 such regions a warping of the earth's crust or a mountain 
 folding may produce great or small basins faster than the 
 feeble rivers can fill them with water or waste, and may 
 raise high barriers faster than rivers can cut gorges through 
 them. 
 
 It is in good part for this reason that the rivers of 
 continental interiors so often discharge their waters into 
 enclosed depressions, and fail to reach the sea. On this 
 account, as well as because of diminished volume, the 
 rivers of arid regions are largely busied in building up 
 their lower courses. 
 
 The interior basins of Utah, ISTevada, Arizona, and Mexico, 
 having light rainfall, fail to support vigorous rivers. Warp- 
 ing and faulting of the earth's crust in this region has pro- 
 duced many enclosed basins, from which the rivers might 
 easily overflow under a more generous rainfall ; hence the 
 name. Great Basin region. 
 
 Many streams descend from the mountains of the basin 
 region and wither away on the sloping waste plains, failing 
 to unite in a trunk river along the trough line between the 
 ranges. Where the streams are a little stronger, a feeble 
 trunk river may be formed, only to wither away as it flows 
 toward the lowest part of its basin. 
 
CLIMATIC CONTROL OF LAND FORMS. 305 
 
 Salt Lakes. — An interior basin receiving a moderate 
 water supply will contain a lake in its lowest part. The 
 lake, having no outlet, must have such an area that 
 evaporation from its surface shall equal the supply from 
 inflowing streams. Lakes of this kind are usually salt, 
 for all the saline substances gathered in small quantity 
 by the inflowing streams accumulate in the lake and may 
 in time constitute a fifth, or even a third, by weight of 
 the lake contents. 
 
 Great Salt lake of Utah, with about 18% of salt, is of 
 this kind, lying on the lowest part of the waste plain that 
 has been built up in the depression among several mountain 
 ranges. Its waters are so dense that a man's body will not 
 sink beneath the surface. The Dead sea, with 24 <^ of salt, 
 is one of the most famous salt lakes, occupying a long, 
 narrow depression in Palestine; its surface is 1300 feet 
 below the level of the Mediterranean. Lake Van in east- 
 ern Turkey, containing 33% of salt, is the densest water 
 body known. 
 
 As the inflow of salt lakes is disposed of by evaporation, 
 their depth and area vary with change of weather and season. 
 When their shores are flat, as is usually the case, the shore 
 line may shift several hundred feet between the wet and the 
 dry seasons ; the strip of land laid bare at the low water 
 stage is charged with salts ; it may bear a peculiar vegetation 
 or may be covered with a saline incrustation. 
 
 Unlike lakes among mountains, salt lakes lying in shallow 
 basins surrounded by arid plains are not elements of beauty 
 in the landscape. Settlements are seldom made on their 
 unattractive shores. An explorer describes Lake Shirwa in 
 southeast Africa as a shallow sheet of foul salt water, lying 
 in the flat central depression of extensive alluvial plains, its 
 margin occupied by great malarial marshes. All the unpleas- 
 
306 PHYSICAL GEOGRAPHY. 
 
 ant features of a torrid quagmire are accented around its dis- 
 mal shores, where crowds of flamingoes, cranes, and screaming 
 water birds, jostling one another for room, only add to the 
 depressing nature of the scene. 
 
 Playas. — In interior basins where no permanent lakes 
 occur, the larger rivers may, at time of flood, reach the 
 lowest depressions and there spread out in shallow tem- 
 porary lakes, which soon disappear in clear and warm 
 weather. The silt brought by such rivers is spread over 
 the depression and thus forms a broad plain of remarkably 
 smooth surface, called a playa. 
 
 One of the largest playas in the Great Basin region is 
 known as Black Rock desert (i>, Pig. 205), in northwest 
 Nevada. It measures about 100 miles in length by 12 or 15 
 miles in breadth. It is overflowed in winter by the extension 
 of Quinn river ; but so level is the plain that the playa lake 
 is seldom more than a few inches deep. The wind stirs the 
 water and raises the fine silt of the plain, making the water 
 turbid ; the lake is then hardly more than ^' a vast sheet of 
 liquid mud." In summer the playa is smooth and dry, hard 
 baked by the sun, and perfectly barren ; one of the most 
 desolate and monotonous surfaces in the world. 
 
 Salinas. — Certain basins that formerly contained salt 
 lakes have now been more or less completely dried out, 
 leaving marshy or dry plains of salt, known as salinas, in 
 the central depressions, avoided by all plant and animal 
 life. 
 
 The Bolivian tableland, a lofty waste-filled basin lying 
 between two great ranges of the Andes, holds Lake Titicaca in 
 its northern part at an altitude of 12,500 feet. The outlet 
 flows 100 miles southeast to a shallow marshy salina about 
 
CLIMATIC CONTROL OF LAND FORMS. 307 
 
 50 miles long. The water not evaporated here flows south- 
 west and is lost in a broad salina of dazzling white surface. 
 Somewhat further south is a more extensive salina, 4000 
 square miles in area, a white and level plain covered with 
 a layer of salt about 4 feet thick, impassable when wet, but 
 firm in the dry season. 
 
 Salt lakes and salinas yield common salt and other min- 
 erals of commercial value. Great Salt lake is estimated to 
 contain 400,000,000 tons of salt. These products would be 
 of greater utility if they did not so generally occur in thinly 
 populated, desert regions. 
 
 The Development of Interior Basins. — Like young 
 mountain ridges, where little carving has been done on 
 uplifted blocks, young basins have received little waste 
 from their rims. Alluvial fans have begun to grow for- 
 ward around their margins, and the finer waste is spread 
 to a moderate depth over their floors. 
 
 The bottom of the trough occupied by the Dead sea is about 
 2600 feet lower than the level of the Mediterranean. Ravines 
 in the border of the uplifted plateau on the east lead down to 
 stony fans that are advancing into the sea. But the great 
 depth of the water, and the moderate extension of the fans 
 show that the basin contains much less waste now than it will 
 in the future. 
 
 Interior basins enclosed by deeply dissected mountains 
 have received the waste that the inner slopes of the 
 mountains have lost. The floors of the basins have in 
 this way been built up and smoothed. By the wearing 
 down of the mountains and the filling of the basins the 
 relief of the region as a whole has been decreased. 
 
308 
 
 PHYSICAL GEOGRAPHY. 
 
 Large alluvial fans of coarse waste with distinctly sloping 
 surface are characteristic features of well-filled arid basins. 
 The head of the fan may rise 500 feet above its rim, and its 
 slope may stretch 10 or 15 miles forward from the mountain 
 valley in which it heads. Thus these arid valleys, like lake 
 basins in moister regions, are gradually being filled with 
 delta-like accumulations of waste. 
 
 Fig. 197. — The Waste-Filled Floor of Death Valley, Southeastern California. 
 
 The water of mountain torrents is often completely lost in 
 the coarse waste of the fans, whose deeper parts thus gather 
 much ground water. By driving tunnels near the base of 
 the fans the water may be reached and brought out to irri- 
 gate the lower slopes. This method has been used for cen- 
 turies in Persia and northwestern India. It is now employed 
 in southern California, where fans of great size are formed at 
 the base of the mountain ranges. 
 
 When many neighboring alluvial fans are spread forth 
 at the base of arid plateaus and mountains, they unite in 
 
CLIMATIC CONTROL OF LAND FOBMS. 
 
 309 
 
 a long gravel-covered slope resembling a river-made plain, 
 but of steeper descent. The surface becomes less and 
 less steep, and the waste less coarse, the farther the slope 
 extends forward. 
 
 Extensive stony slopes of this kind occur in the depres- 
 sions between the desert mountains of Utah, Nevada, and 
 Arizona. The waste fills the depressions to great depths, 
 and backs up 2000 or 3000 feet on the flanks of the 
 mountains. 
 
 Fig. 198. — Half-Buried Uountain Bange, Nevada. 
 
 If the depression between the mountains is of small 
 breadth, the gravel slopes grow forward till they meet 
 in a rather well-marked trough line ; here a stream may 
 flow in the wet season. If of great breadth the slopes 
 grade into a dreary plain, with occasional springs around 
 its margin and temporary lakes in the center. 
 
 Opposite the mouths of canyons, trains of coarse waste, 
 including boulders weighing many tons, are spread forward 
 
310 
 
 PHYSICAL GEOGRAPHY. 
 
 by floods from cloud-bursts in the mountains — " immense, 
 sudden, deluging rainstorms, which, at rare and exceptional 
 moments discharge their waters into one of these mountain 
 gorges. On such occasions boulders 6 or 8 feet in diameter 
 are swept down the canyon in a fearful rush, and are some- 
 times carried out on the ... slope for half a mile." At other 
 points the slope is trenched from 50 to 200 feet deep opposite 
 the canyons, revealing its stony structure. 
 
 The farmer ant is one of the most remarkable and numer- 
 ^.-__ ous of the few forms 
 
 of animal life on these 
 stony slopes in the 
 southwestern United 
 States, near the Mexi- 
 ca,n boundary. Each 
 "farm" includes a 
 clean threshing floor, 
 from 5 to 30 feet across, 
 with a belt of grass 
 around it, and a passage 
 to the underground 
 dwelling in the center. 
 "Roads" a foot wide 
 connect the "farms" across the grass rings for hundreds of 
 feet ; the " farms " may cover nearly all the surface over 
 scores of square miles. 
 
 In such a farming district other plants, common in the 
 surrounding region, are carefully kept out by the ants. The 
 grass is their food crop, as they live on its seeds. If the crop 
 failed, they would die of famine by millions. The grass 
 would greatly decrease if it were not cultivated and the other 
 plants destroyed. 
 
 As the waste from the higher enclosing mountains is 
 washed into great interior basins, the smaller ridges may 
 be nearly or quite buried. Many small basins, originally 
 
 Fig. 199. — Home of the Farmer Ant. 
 
CLIMATIC CONTROL OF LAND FORMS. 311 
 
 separated by ridges, may thus be converted into a few 
 large basins ; in time all the basins may unite in a single 
 depression, which will then receive the drainage and 
 waste from all the surrounding region. 
 
 A great part of Persia consists of large basins enclosed by 
 mountains and without outlet to the sea. Long waste slopes 
 stretch forward 5 or 10 miles with a descent of 1000 or 2000 
 feet, stony near the mountain flanks, and gradually becoming 
 finer-textured and more nearly level. The central depressions 
 are absolute deserts of drifting sands, with occasional saline 
 lakes or marshes. The population gathers around the margin 
 of the basins where water is still to be found, avoiding the 
 rugged and barren mountains on the one hand, and the unin- 
 habitable central plains on the other. 
 
 Central Asia repeats the same conditions on a still larger 
 scale. The basin of Eastern Turkestan includes many half- 
 buried ranges in its central part. It is quite possible that 
 some ranges are completely covered with waste. Many rivers 
 flowing from the mountain rim wither on their way towards 
 the chief central depression ; only the largest river (Tarim) 
 reaches it, there spreading out in Lob (Lake) Nor, The chief 
 settlements are near the border of the basin, where the larger 
 rivers come out from the mountains. 
 
 Outward Drainage of Former Interior Basins. — The 
 
 lofty desert plateau of Tibet consists of many mountain 
 ranges Avith waste-filled basins between them. As in all 
 such forms, the gradual wasting of the ranges and filling 
 of the basins tend to make the whole surface more nearly 
 level. In time a lofty plain might here be formed, stand- 
 ing at a great altitude above baselevel. 
 
 During the advance of this long process, the active 
 headwater streams on the outer slopes of the enclosing 
 
312 
 
 PHYSICAL GEOGRAPHY 
 
 mountains may gnaw their way through the ranges, and 
 thus capture some of the streams of the interior basins, 
 giving them an exterior discharge. 
 
 One of the lofty basins on the southern border of Tibet is 
 now deeply dissected by the streams that have been turned 
 outward to the deep valleys of the Himalaya in this way. 
 Other basins (A, Fig. 200) are encroached upon by the head- 
 
 Fig. 200. — Diagram of Outward Drainage of Interior Basin, Himalaya. 
 
 water torrents (T) that have already gnawed their way 
 through the northernmost range of the Himalaya (S). The 
 deep notches thus worn in the mountains form the passes by 
 which the plateau of Tibet is reached from th'e Himalayan 
 valleys (F). 
 
 An interior basin may gain exterior drainage when its 
 depression is filled with waste until overflow occurs at 
 some low point on the basin rim. Then the outflowing 
 streams will tend to erode their channels with respect to 
 the general baselevel of the ocean surface, instead of with 
 respect to a central lake or playa ; and the basin will be 
 worn down instead of built up. As the waste is washed 
 out of the basin the rock floor will be worn down also. 
 
 An arid region in southern Arizona and northwestern 
 Mexico (the Sonoran district) includes forms that may be 
 
CLIMATIC CONTROL OF LAND FORMS. 
 
 313 
 
 explained in this way. A long rock-floored inclined plain 
 (QJ}i, Fig. 201), descending 200 or 300 feet to a mile, leads 
 forward from the base of the mountains (BQ). The gravelly, 
 waste from the mountains is washed across the plain to a flat 
 trough (NM), and the finest waste is washed along the trough 
 to the sea. 
 
 Fig. 201. — Diagram of a Waste-Filled Trough. 
 
 It is thought that at an earlier time, when the mountains 
 were much, higher (like KLH), the trough at their base was 
 broadly filled with their waste {HJ)- At that time they 
 resembled the mountains of Utah and Nevada, and the troughs 
 did not overflow. An overflow of waste being after a time 
 reached, the surface was gradually worn down lower and 
 lower, and LHJ was changed to BQN. 
 
 Sheetfloods. — ■ The behavior of the drainage in the Sono- 
 ran region is peculiar. The rainfall averages only two or 
 three inches a year ; for although a single shower may yield 
 almost as much as the annual fall, the showers are very 
 rare ; the sky is cloudless for a great part of the time. In 
 the mountains the rainfall gathers in streams in steep-sided 
 ravines, and issues upon the plains heavily charged with 
 
314 PHYSICAL GEOGRAPHY. 
 
 waste. There the water finds no channels ; it spreads out in 
 a shallow sheet, called a sheet flood, which gains a breadth of 
 a mile or more, but a depth of only one or two feet ; rushing 
 down the incline towards the troughs, but rapidly dwindling 
 when it encounters layers of gravel on the rocky floor. 
 
 As the sheetflood subsides, its waste is left strewn over 
 the smooth rocky floor, and the ground water soon escapes 
 by evaporation. Another storm, shedding its rain here or 
 there upon the rock-floored inclines or on the flat troughs, 
 washes the waste along a little distance ; and thus by degrees 
 it is carried forward, at last reaching its goal in the sea. 
 
 The Effect of the Wind ox Land Forms. 
 
 Comparison of Winds and Streams. — Where the land 
 surface is covered with vegetation, the wind has little 
 eifect on the form of the ground. In arid regions where 
 vegetation is scanty or wanting, the wind may become a 
 powerful agent of denudation and transportation. In such 
 regions the whole surface over which the wind acts should 
 be compared to the uneven bed of a broad river. 
 
 The difference of wind action on a dusty road and on a 
 grassy field may be taken to illustrate the contrast between 
 wind action in regions of dry and regions of wet climate. 
 
 In a general way, the wind raises the finest dust into 
 the body of its current, drifts along the sand at the bottom 
 of tlie current, and rasps the unmoved stones and ledges 
 with the drifted sand. 
 
 The wind that blows over desert mountain tops sweeps 
 away the finer waste so quickly that there is never enough 
 of it to make the upper air dusty. On arid lowlands the dust 
 is blown here and there ; what is raised by one storm hardly 
 
CLIMATIC CONTROL OF LAND FORMS. 315 
 
 settles before another storm occurs; here the lower atmosphere 
 is often turbid, the sky is of a dull gray color, and distant 
 objects are obscured. 
 
 Uplands, projecting into the great air currents, are 
 stripped of their sand and dust, leaving their surfaces 
 bare and stony. Less exposed surfaces gather the drift- 
 ing sand in hills, called dunes. The finest dust is carried 
 furthest and settles chiefly in protected basins, where the 
 wind tends to stagnate. 
 
 Many points of similarity may thus be found between wind 
 and water action. The uplands of the Sahara have extensive 
 surfaces of bare rock or of loose wind-carved stones; the dust 
 and the finer sand have been blown away to settle on the 
 lower lands. The stony uplands in the desert south of 
 Algiers are known as hainniada, on which travelling is diffi- 
 cult and fatiguing. 
 
 Sand Dunes in deserts may grow to a height of from 
 500 to 600 feet. In a region of relatively steady winds 
 
 Fig. 202. — Sand Dunes in the Sahara. 
 
 the sand is blown up the Avindward slope and carried over 
 the crest; hence the dune may slowly advance, gradually 
 changing its place and form. 
 
316 
 
 PHYSICAL GEOGRAPHY. 
 
 Drifting sand gives a loose footing and makes travelling 
 in a desert a weary task. A hot and violent wind, known 
 in Arabia and the Sahara as the Simum, raises clouds of 
 sand and dust, rapidly modifying the form of the dunes 
 over which it blows. It sometimes overwhelms caravans 
 — the easier if men and beasts are already exhausted by 
 thirst and fatigue. 
 
 The San Luis valley in Colorado and New Mexico is a waste- 
 filled basin enclosed by mountain ranges. It is an oval plain, 
 measuring about 40 by 140 miles, at an elevation of from 7500 
 to 8000 feet. The greater part of the surface is "as flat as a bil- 
 liard table." Coarse gravels slope inward around the border ; 
 streams wither as they flow towards the center ; fine silts floor 
 the central area, where small alkaline lakes occur. Drifting 
 sands, gathered from the basin, form extensive dunes on the 
 eastern or lee side of the plain at the base of the enclosing 
 mountains. A large lava flow covers many square miles near 
 the southwest margin. The Rio Grande receives the stronger 
 inflowing streams, and escapes southward through a deep and 
 gloomy gorge in the mountains. 
 
 An extensive dune-covered area is found in northwest 
 Nebraska, occupying thousands of 
 square miles. "The scenery is 
 exceedingly solitary, silent, and 
 desolate." The round hilltops rise 
 evenly as far as the eye can reach ; 
 travelling over them is extremely 
 difficult. A scanty vegetation in 
 the hollows, where ground water can 
 be reached by plant roots, once supported great herds of buffalo, 
 and now yields light pasture to wandering herds of cattle. 
 
 Dust Plains. — During times of high wind the air of arid 
 basins may be so darkened with dust as completely to hide 
 
 Fig. 203.— Buffalo. 
 
CLIMATIC CONTROL OF LAND FORMS. 
 
 317 
 
 the sun. The finest dust penetrates all enclosures and 
 makes everything feel gritty. As the winds decrease, the 
 sun becomes visible, at first of a ruddy color ; it may 
 disappear again in the murky atmosphere before reaching 
 the horizon. 
 
 The long-continued action of winds blowing from an 
 arid continental interior may form heavy deposits of dust 
 on the lower lands to leeward. Hills and valleys are in 
 time buried hundreds of feet beneath the even surface of 
 the dust plain. Such deposits are known as loess (a German 
 word meaning loose ; pronounced almost like less). 
 
 There are many loess-filled basins in the interior of China. 
 Their margins, conta,ining gravel and sand washed from the 
 enclosing slopes, are 2000 or 3000 feet higher than the 
 central parts, 
 which are occu- 
 pied by playa 
 muds or saline 
 deposits. But the 
 greater part of the 
 basin is filled with 
 a fine, almost im- 
 palpable dust to a 
 depth of hundreds 
 of feet. 
 
 Some of the 
 loess-filled basins 
 of China are now 
 partly dissected ; 
 a main river runs through the middle of the basin and receives 
 branches that have worn a labyrinth of forking ravines in the 
 loess deposits. 
 
 Millions of Chinese live on the valley floors of dissected 
 basins of this kind ; for loess is extremely fertile where well 
 
 Fig. 204. —Loess Beds, Yellow River Basin, China. 
 
318 PHYSICAL GEOGRAPHY. 
 
 watered. Great numbers of the people inhabit cave-like 
 dwellings excavated in loess bluifs ; in a thickly populated 
 district not a house may be seen. The yellowish color of 
 loess prevails everywhere. It gives color and name to the, 
 great river of the region and to the sea into which the river 
 flows. 
 
 Dry Regions, formerly Moist. — In certain regions, now 
 arid, marks of a former moist climate are found. The dry 
 valleys or wadies in the Sahara seem to be the work of 
 larger and steadier rivers than now follow them. Certain 
 basins now almost without water have been filled with 
 great lakes, even to overflowing ; the former shore lines 
 of the lakes are marked b}' cliffs, beaches, and deltas, and 
 an outlet is sometimes traceable in a trench across the 
 lowest pass in the enclosing highlands. 
 
 The basin of Great Salt lake in northwestern Utah once 
 contained a much larger lake, to which the name of an 
 explorer, Bonneville, has been given. Its shore lines are 
 still plainly recorded on the mountain sides nearly 1000 feet 
 above the desert plain around the present lake ; the fore- 
 ground of Fig. 103 shows extensive beaches of this lake. 
 The channel of an outlet leads northward across a pass to 
 the basin of Snake river ; hence the former lake must have 
 been fresh. The change from the moister climate of Lake 
 Bonneville time to the drier climate of to-day has caused the 
 almost complete disappearance of the lake waters, revealing 
 the sediments of the lake floor in an arid plain. The ancient 
 lake deltas are now trenched by the streams that built them. 
 
 One of the most remarkable features of this change of 
 climate is its rapidity as compared with the changes of land 
 forms. The cliffs, beaches, and deltas on the shore lines of 
 the extinct lake are still remarkably distinct. The same is 
 
CLIMATIC CONTROL OF LAND FORMS. 
 
 319 
 
 true of a former extensive lake (Lahoutan) of very irregular 
 outline in western Nevada, as well as of similiar ancient 
 lakes in various parts of the world. 
 
 Fig. 205. — Lakes Bonneville and Lahontan. 
 
 The causes of climatic changes of this kind are little under- 
 stood, but their geographical consequences in replacing exten- 
 sive lakes among forest-clad slopes by desert plains between 
 arid mountains are of great importance. 
 
 Plants and Animals of Aeid Regions. 
 
 Forms of Life in Arid Deserts. — Plant and animal 
 life is scanty or absent in arid regions, because of the 
 difficulty of securing food and water. The dryness of the 
 soil is unfavorable to plant growth. Leaves are small or 
 wanting, and thus the loss of water by evaporation from 
 the leaf surfaces is diminished. Thorns are commonly 
 
320 
 
 PHYSICAL GEOGRAPHY. 
 
 developed, like so many signs — "keep off " — as if to lessen 
 the chance of injury to the plant in a region where liv- 
 ing is so difficult that 
 every aid must be 
 summoned to protect 
 life. 
 
 Duringlong droughts 
 an arid region may 
 seem almost free from 
 vegetation. If rain 
 falls, small plants 
 spring up everywhere, 
 refreshing the surface 
 with their green color 
 but soon wit'jering 
 away in the sr ;3eding 
 dry period. \i.liis is 
 
 Fig. 206. - The Yucca, a Desert Tree. particularly marked OU 
 
 the borders of the subequatorial rain belts, where the ground 
 may be bare and dusty in the dry season and covered with 
 vegetation in the wet season ; as on the Llanos of Venezuela. 
 On the desert slopes of Peru, where droughts may last four 
 or five years without rain, plants soon spring up after a 
 shower. These examples show that the plants of arid regions 
 possess great vitality. 
 
 The same thing is seen in the subtropical belts, but less 
 distinctly, for there the rain comes in the cool season ; as in 
 the Algerian Sahara. In continental interiors, where most 
 of the rainfall is in smnmer, the wandering of nomadic tribes is 
 largely determined by the search for pasture for their flocks ; 
 as on the dry plains or stepi^ns north of the Caspian sea. 
 
 The larger plants of arid regions are thinly scattered, 
 leaving much bare surface. There is no striving for 
 
CLIMATIC CONTROL OF LAND FORMS. 321 
 
 space, such as commonly occurs in well-watered regions, 
 where plants of more active growth may crowd out the 
 weaker forms. Dry regions seldom produce plants of 
 economic value. Trees are small, and their wood is 
 hard and knotted ; they cast little shade on the dry, bare 
 ground. The sagebrush, so abundant on the arid western 
 plains of the United States, finds no use except as an 
 inferior firewood. 
 
 The contrast between the open plant growth of dry regions 
 and the crowded forests and jungles of the equatorial rain 
 belt is very striking. The equatorial forest is gloomy, reek- 
 ing with the damp smell of rotting vegetation. Gigantic 
 trees rise high before branching ; lesser trees push their way 
 upward, searching for every foot of vacant space. Thorny 
 creepers and tangled undergrowth twine beneath in an intri- 
 cate and impassable web. Objects near at hand are hidden 
 from view. On the other hand the glaring light of the sun in 
 the unclouded sky over a desert is tempered only by dust 
 raised from the parched ground. If 
 scattered trees or bushes can grow, 
 they are usually too far apart to ob- 
 struct the view. 
 
 The animals of deserts are gen- 
 erally of dull or gray color, not 
 easily seen on the barren surface. 
 Many of them are fleet in move- 
 ment, like the antelope ; or of OTeat 
 
 T , P I'ig- 207. -Camel. 
 
 endurance under a small supply of 
 
 food and water, like the camel. Those which are slug- 
 gish are often venomous, like the scorpion and rattle- 
 snake. 
 
322 PHYSICAL GEOGRAPHY. 
 
 The People of Deserts. - — • The human inhabitants of 
 arid deserts are few and miserable, as compared to the 
 more favored races of the world. Their food supply is 
 scanty and of little variety. Their arts are primitive, for 
 raw materials are of few kinds. They possess strength 
 and endurance, without which life would be impossible 
 under the difficulties around .them ; they have a "keen 
 intelligence for every advantage that their desert home 
 affords, but they cannot rise above a low stage of devel- 
 opment. 
 
 Many of the wandering tribes are, by force of necessity, 
 beggars and robbers. The struggle for existence is so severe 
 with them that they and their animals are frequently on the 
 verge of starvation. Yet so accustomed are they to their 
 wretched life that they do not wish for the changes proposed 
 by strangers. 
 
 The Papago Indians of the Sonoran region, south of the 
 Gila river, move from place to place with the failing and 
 flowing of springs. They are noted for strength, speed, 
 endurance, and abstinence. The Seri Indians, living in the 
 desert on the border of the Gulf of California, have no horses 
 and are noted as runners. 
 
 In regions of favoring climate and more varied products, 
 the manner of life of civilized people is so complicated by 
 long-growing habits and customs that it may seem in many 
 ways to be independent of geographical conditions. In the 
 simpler life of desert tribes the force of geographical con- 
 trol is more apparent, but not more real. 
 
 Oases. — Fixed settlements in desert regions are almost 
 entirely controlled by the occurrence of water. They are 
 commonly made where springs or streams flow upon the 
 open country at the base of uplands and mountains ; or 
 
CLIMATIC CONTROL OF LAND FOEMS. 
 
 323 
 
 near the ends of such streams, where they can be distrib- 
 uted in irrigating canals ; or at points where ground 
 water may be found in the nearly dry channels of with- 
 ered streams. Such settlements are called oases in the 
 Sahara, and the same name may be used elsewhere. 
 
 Fig. 208. — El Rantara Oasis, Algerian Sahara. 
 
 The barrenness of many deserts is due simply to their 
 dryness and not to an unfavorable composition of rock or 
 soil. Where springs or streams moisten the soil, grass and 
 trees may grow naturally. If the surface can be irrigated, 
 its productiveness may be increased so as to support permanent 
 settlements. 
 
 The contrast between a habitable spot and the surround- 
 ing barrenness is so grateful that " an oasis in the desert " 
 has come to serve as a poetic figure. But oases are only 
 relatively delightful. Their water supply is often limited 
 and impure ; their products are few in variety and small 
 
324 PHYSICAL GEOGRAPHY. 
 
 in quantity ; their industries are primitive ; tlieir inliab- 
 itants have to suffer the disadvantages of isolation as com- 
 pletely as the people of islands. 
 
 The oasis of Siwa, in the Sahara, 350 miles west of Cairo, 
 "the first halting place on the great desert highroad to the 
 west," is still little changed from its condition in ancient 
 times. Seclusion seems to have bred mistrust, for stran- 
 gers are looked on as intruders. They and their modern 
 ways of doing things are unwelcome. 
 
 The large and important oasis of Merv, northeast of Persia, 
 has a population of several hundred thousand, gathered in 
 many villages. The oasis is on a flat alluvial fan, formed 
 and watered by the Murg-ab (-river). The river is divided 
 into two distributaries, then into forty-eight smaller branches, 
 and again into hundreds of irrigating canals. 
 
 The inhabitants of an open country that has a sufficient 
 rainfall, with plentiful ground water easily reached in wells 
 and with numerous springs and streams, are free to settle 
 almost as they like. They seldom realize the importance 
 that a spring or small water course has in the life of 
 dwellers in deserts. 
 
 The occasional springs on the arid plateaus of Arizona are 
 regarded as so important that their position is indicated on 
 the government maps of that region. Travellers across the 
 plateaus follow trails that lead from spring to spring. 
 
 Ice Sheets and Glaciers of the Present. 
 
 Glacial Climate. — Where the temperature is so low 
 that the snowfall of the colder season is greater than the 
 loss by melting in the milder season, a heavy cover of ice 
 
CLIMATIC CONTROL OF LAND FORMS. 325 
 
 and snow many hundred feet thick is formed. The icy 
 sheet slowly creeps from the place of chief supply to lower 
 ground ; there it melts and the water runs away in 
 streams. Its edge may enter the sea, where besides melt- 
 ing it breaks off in large masses which float away as ice- 
 bergs. These long-lived accumulations of ice are called 
 ice sheets and glaciers. 
 
 The change from snow at the surface to ice beneath is 
 aided by water from occasional rains and from surface melt- 
 ing. The water sinks into the deeper snow and there freezes. 
 The ice thus formed is granular, and the motion of the mass 
 is much aided by a slight slipping of grain on grain. 
 
 During winter in the northern United States there are fre- 
 quent examples of the formation of small, short-lived ice 
 sheets, after a succession of snowstorms with prevalent cold 
 weather and occasional thaws. Such an ice sheet is not thick 
 enough to move ; but if it should grow year after year to 
 a thickness of 1000 or more feet, it would slowly move 
 from the region of greatest height and thickness to lower 
 ground in a milder climate. 
 
 Antarctic Ice Cap. — A few explorers of the far south- 
 ern ocean have discovered a great ice sheet ending in cliffs 
 that rise from 100 to 180 feet above the sea. No land was 
 seen back from their top. 
 
 Although as yet known only on one side of the South 
 Pole, the ice sheet is thought to form a polar ice-cap, per- 
 haps 1000 miles in diameter. There may be some land on 
 which the cap rests ; but it is believed that much of it lies 
 on the sea bottom. It must tend to thicken from snow sup- 
 ply over its desert, plateau-like center ; but it slowly creeps 
 towards the free sea margin, where great tables of ice break 
 off and float away. 
 
326 PHYSICAL GEOGBAPHY, 
 
 The Greenland Ice Sheet. — Greenland is covered by a 
 lieavy sheet of ice, measuring about 1500 miles north and 
 south by from 300 to 600 east and west. It has a slightly 
 conv^ surface, and probably rises to a height of 9000 
 feet in the central part. As far as explored, the ice con- 
 ceals all hills and mountains except near the margin, 
 where the sheet is thinner; here occasional rocky sum- 
 mits rise above the surface like islands in a frozen sea. 
 Descending gradually towards the coast, the ice either thins 
 out on land, or advances along the valleys in branch-like 
 arms or glaciers, some of which extend into the sea. 
 
 Some of the Greenland glaciers are from 10 to 50 miles 
 broad where they enter the sea. Their forward movement is 
 from 20 to 50 feet a day. Many icebergs are formed of great 
 fragments broken from their front. Xansen, the famous Arc- 
 tic explorer, was the first to cross the ice sheet of Greenland 
 (1888, in latitude 64i^°). Peary crossed northern Greenland in 
 1892. The interior is a monotonous desert of snow and ice, 
 now melting and becoming almost impassable, now freezing 
 over or receiving a new layer of snow. Most of the surface 
 is unbroken ; but near the margin, where the motion is 
 faster in one part than in another, the ice is deeply fissured 
 or crevassed. 
 
 The only inhabitants of this great cold desert are a simple 
 microscopic plant that sometimes gives a red color to snow, 
 and a minute worm. The Eskimos of Greenland live on the 
 narrow belt of land between the ice sheet and the shore. 
 
 Alpine Glaciers. — Glaciers of the Alpine type flow in 
 stream-like tongues from the valley heads between lofty 
 peaks and ridges. The snowfall in the valley, increased 
 by avalanches from the enclosing walls, is gradually con- 
 verted into granular ice ; and the ice slowly creeps down 
 
CLIMATIC CONTROL OF LAND FORMS. 
 
 327 
 
 the valley, melting as it descends to a milder climate than 
 that of its gathering ground. The end of a glacier may 
 often reach far below the tree line and even approach fields 
 on the floors of the larger valleys. 
 
 In the upper valley reservoirs the snow surface is concave, 
 sagging from sides to middle ; here movement is directed 
 inward from the enclosing slopes. Standing in one of these 
 reservoirs in clear 
 weather, one may 
 see only dark 
 ledges and peaks 
 that rise over the 
 dazzling snow 
 under a deep blue 
 sky, --- all barren 
 and silent. In 
 the lower tongue 
 of a glacier the 
 ice stream is con- 
 vex, and moves a 
 little towards 
 either bank as well 
 as downward 
 along the slope of 
 
 J.1 vallpv ^'^" 209.— Eosegg Glacier in the Alps, 
 
 A glacier moves faster along the medial surface line than 
 at sides or bottom, thus resembling a river. The movement 
 of Alpine glaciers is from 100 to 500 feet a year on the aver- 
 age, about as fast as the point of the hour hand of a watch. 
 Where the valley steepens, the motion is more rapid and the 
 ice is irregularly broken. Its parts unite again on the next 
 gentler slope, and the ice stream flows on as before. 
 
 The Aletsch glacier is the longest in the Alps, measuring 
 about 13 miles from head to end. Glaciers of much greater 
 size occur in the Himalaya and in Alaska. 
 
328 
 
 PHYSICAL GEOGRAPHY. 
 
 Creeping glaciers press heavily on their beds, dragging 
 rock waste beneath them and scouring the bed-rock clean 
 and smooth. Loose grains and fragments of rock, dragged 
 along by the ice, scratch and groove the smoothed rock 
 surface. The rock waste thus scoured from the ice floor, 
 as well as that torn from projecting ledges and received 
 in rock slides and avalanches from surmounting slopes, is 
 ^P-^-' dragged or carried along 
 
 P'^ by the ice and deposited 
 
 around its lower margin 
 or at its end. Great 
 boulders may be trans- 
 ported in this way. 
 
 The Swiss name mo- 
 raine is applied to various 
 forms of ice-borne rock 
 waste. That underneath 
 the glacier is called 
 ground moraine; it is 
 firmly compacted by the 
 pressure of the ice. The 
 waste on the side of a 
 valley glacier forms the 
 lateral moraine. Where 
 two glaciers unite, the 
 adjacent lateral moraines 
 form a single medial moraine. The rough heaps and ridges 
 of waste deposited around the end of a glacier (or at the 
 margin of an ice sheet) form the terminal moraine. Here 
 the waste is often loosely deposited ; it may be laid down 
 in beds by water running from the ice. Glacial drift 
 is a more general term for waste moved by ice and ice- 
 water. 
 
 Fig. 210. — Viesch Glacier in the Alps. 
 
CLIMATIC CONTROL OF- LAND FORMS. 329 
 
 Large glaciers are sometimes so heavily covered with 
 moraines near their lower end that a plant-bearing soil is 
 formed upon them. Pasturage is found for the flocks of the 
 mountaineers in the Himalaya on certain grass-covered mo- 
 raines overlying the ice. Some Alaskan glaciers bear large 
 forests near their ends. 
 
 Water received from side streams and supplied from melt- 
 ing ice gathers beneath a glacier and issues from an ice cave 
 at its end. The water is usually whitened by fine "rock 
 flour " ground beneath the ice. 
 
 The length of glaciers is found to increase and decrease 
 slowly in successive years. For a time they lengthen or 
 advance ; then they melt back or retreat ; the change 
 being completed in the Alps in a period of about thirty- 
 five years. This is believed to result chiefly from a varia- 
 tion in the snowfall. 
 
 A change of snow supply is sooner indicated by a vari- 
 ation in the end of a short than of a long glacier ; hence 
 all the glaciers of a mountain range do not vary together. 
 
 These slow variations in the length of glaciers may be com- 
 pared to the rapid variations in the length of streams that 
 descend from, mountains and wither away on deserts. After 
 each rain the streams advance for a time and then retreat. 
 The change is seen first in the end of the short streams. 
 
 An advancing glacier at first usually overrides the soil 
 in front of it, overturning trees, if they stand in the way ; 
 it slowly drags forward the waste as a greater weight of 
 ice comes upon it, and at last grinds and smooths down 
 the firm rock ledges. A retreating glacier, receding from 
 the terminal moraine that was made at its greatest ad- 
 vance, leaves a barren stony bed to be slowly invaded 
 
330 PHYSICAL GEOGRAPHY. 
 
 by plants from neighboring slopes. Here the forms pro- 
 duced by the ice in scouring the surface on which it moved 
 may be conveniently studied. 
 
 The chief regions of valley or Alpine glaciers are the 
 Alps, the Caucasus, the Himalaya, and other lofty ranges 
 of Eurasia ; the New Zealand Alps ; the southern Andes ; 
 and the northern members of the Rocky mountains, from 
 the Selkirk range of Canada to the St. Elias range of 
 Alaska. 
 
 The snowy Selkirk range, crossed in a high pass by the 
 Canadian Pacific Railway, promises to become a center of 
 glacier excursions in North America, like the Alps in Europe. 
 The heavy snowfall of the St. Elias range feeds large gla- 
 ciers, many of which descend into the sea, like the famous 
 Muir glacier, now visited every summer by excursion steamers 
 from Pacific ports. 
 
 From the valleys about Mt. St. Elias itself the uniting 
 glaciers form a great ice fan at the base of the mountains 
 (in shape like a flat alluvial fan), known as the Malaspina 
 glacier. It spreads 20 miles forward to the sea, with a front 
 of 70 miles. Rivers issue from tunnels beneath the ice and 
 build extensive stony deltas. Smoothed rock surfaces, for- 
 merly covered and worn by the ice, are well exposed near 
 the border of the glacier. 
 
 The Work of Ancient Glaciers and Ice Sheets. 
 
 The Glacial Period. — The study of existing glaciers 
 is of much importance from the light that it sheds on 
 the geographical features of certain regions where great 
 glaciers or ice sheets existed during former periods of the 
 earth's history. 
 
CLIMATIC CONTROL OF LAND FOBMS. 
 
 331 
 
 The time of the former extension of glaciers and ice sheets 
 is called the glacial period. It must have been a time of 
 lower temperature and greater snowfall than to-day. It 
 included several epochs of extensive advance and retreat. 
 Regions that have been ice-covered are said to have been 
 glaciated. It is often convenient to refer to periods of time 
 before, between, and after the chief glacial advances as pre- 
 glacial, interglacial, and postglacial. 
 
 The glacial period probably corresponded with the period of 
 moister climate in those interior basins that recently (in the 
 earth's history) contained great lakes. 
 
 During the glacial period many glaciers in lofty moun- 
 tains advanced far dov^n their valleys and overspread 
 the adjoining lowlands. Terminal moraines, formed at 
 the greatest advance of the glaciers or during their retreat, 
 are now found in the lower valleys. Lakes often lie in the 
 glaciated valley 
 floors, as if the 
 enlarged ice 
 streams had 
 scoured out their 
 basins. 
 
 Ancient gla- 
 ciers occupied the 
 valleys of certain 
 mountains that 
 now bear little 
 snow ; as in the 
 Rocky mountains t.- „,. ^, • , ,„ c- ^t ^ r. ,-, 
 
 •J Fig. 211. — Glacial Moraines, Sierra Nevada, Califorma. 
 
 of Colorado and 
 
 the Sierra Nevada of California. Great glaciers descending 
 
 from the high Sierra into the desert valley of Mono lake in 
 
332 
 
 PHYSICAL GEOGRAPHY. 
 
 eastern California built strong moraines forward from the 
 mountain base. Twin lakes at the head of the upper Arkansas 
 valley in Colorado are held within heavy terminal moraines. 
 Around the border of the Alps the lower land near the 
 outlet of the chief valleys is often enclosed for 10 or 20 miles 
 from the mountains by a belt of hilly morainic ridges. The 
 ancient glaciers that descended southeast from Mt. Blanc to 
 the river-made plain of the Po built a huge terminal moraine, 
 whose ridges rise from 1000 to 1500 feet above the plain, 
 enclosing a great amphitheater. 
 
 Fig. 212. — Glaciated Area of the Northern United States. 
 
 The Highlands of Scotland, to-day without permanent 
 snow fields, were occupied by great streams of ice during 
 the glacial period. Large glaciers extended into the 
 ocean, east and west. The many lakes that lie in the 
 broader valleys result partly from the scouring or erosion 
 of the valley floors by the ancient glaciers, partly from 
 dams formed by terminal moraines. 
 
 The most extensive ice sheets of the glacial period 
 were those that spread outward from the highlands of 
 
CLIMATIC CONTROL OF LAND FORMS. 
 
 333 
 
 eastern Canada across the basins of the Great Lakes upon 
 the northern United States, and from the highlands of 
 Scandinavia across the Baltic upon northern Germany. 
 
 The occurrence of ancient ice sheets is known by the many 
 marks of their presence still remaining, such as moraines and 
 other forms of drift, transported boulders, and scratched rock 
 ledges. The ice sheet that spreads from the highlands north of 
 
 Fig. 213. — Diagram of an Ice Sheet. 
 
 the St. Lawrence is known as the Laurentian glacier. It was 
 a desert nearly as extensive as the Sahara. The Scandinavian 
 ice sheet was nearly as large as the desert of inner Australia. 
 These ancient ice sheets advanced and retreated more than 
 once, reaching different limits in the successive advances. At 
 each advance they drove away the plants and animals of the 
 region that they invaded ; at each retreat plants and animals 
 were free to take possession again of the uncovered surface. 
 
 H M' L 
 
 Fig. 214. — Diagram of a Retreating Ice Sheet. 
 
 Effects of the Glacial Period. — The geographical conse- 
 quences of the glacial period are numerous and important. 
 Rivers flowing from the ice sheets were so well supplied 
 with waste that they filled their valleys with broad grav- 
 elly or sandy flood plains (A, Fig. 213). Since the disap- 
 
334 PHYSICAL GEOGRAPHY. 
 
 pearance of the ice, the rivers have terraced the drift-filled 
 valley floors {T, Fig. 214). 
 
 The valleys of the south-flowing rivers of Ohio, Indiana, 
 and Illinois, outside of the glacial area, are now bordered by 
 drift terraces from 10 to 40 or more feet in height. The 
 mounds that mark the sites of prehistoric Indian villages are 
 frequently found upon these terraces. Many villages to-day 
 have a similar situation. 
 
 Not only at the time of greatest advance but also during 
 the disappearance of the ice sheets, the valleys leading away 
 from their retreating edge were generally more or less filled 
 with washed sands and gravels. It was under such condi- 
 tions that the Chippewa river of Wisconsin, heading in the 
 retreating ice sheet and carrying much drift down its valley, 
 built a fan delta in the valley of the Mississippi, obstructing 
 the main river and causing it to spread over its flood plain, 
 forming the narrow Lake Pepin (P, Fig. 219). 
 
 The Connecticut and Merrimac valleys in New England, 
 well within the glaciated area, have many drift terraces along 
 their sides. The valleys must have been drift-filled while 
 the ice was retreating ; the high flood plains thus formed 
 have been trenched and terraced after the ice had disappeared. 
 
 Terminal Moraines were generally formed along the 
 margin of great ice sheets, not only at their furthest 
 advance but also during pauses in their retreat (M, M', 
 Fig. 214). The moraines are hilly belts of gravel, sand, 
 clay, and boulders ; they may be one or more miles wide, 
 and from 50 to 100 feet in local relief. Although seldom 
 of conspicuous height, they are often the only hills to be 
 seen for many miles in the prairie states of the Ohio basin. 
 Their surface is often too uneven and their soil too coarse 
 and stony for cultivation in competition with the fertile 
 prairies that they interrupt. 
 
CLIMATIC CONTROL OF LAND FORMS. 
 
 335 
 
 Hollows or "kettles" among the morainic hills frequently 
 contain small lakes or swamps. The small lakes of northern 
 Indiana are of this kind ; their number is not less than 1000. 
 
 Terminal moraines are strongly developed in the Dakotas. 
 They are from 3 to 10 miles wide ; sometimes so rough, with 
 
 Fig. 215. — Glacial Moraine*, North Dakota. 
 
 so many stony hills and hollows, as to present a formidable 
 barrier to travel. One may easily lose his way on this undu- 
 lating surface, where the hills are all much alike and where 
 no conspicuous landmarks serve as guides. 
 
 Ground Moraines. — During the occupation of a region 
 by an ice sheet, the terminal moraines receive only a 
 small part of the rock waste that is dragged forw^ard by 
 the slow motion of the ice or washed along by subglacial 
 streams. A great part of the drift remains beneath the 
 ice as a ground moraine, distributed over the glaciated 
 region. It may be spread unevenly, causing irregular 
 changes of moderate amount in the form of the surface. 
 Where it accumulates in greater quantity, it may be of 
 
336 
 
 PHYSICAL GEOGRAPHY. 
 
 sufficient thickness to buiy low hills and shallow valleys, 
 forming extensive plains. It is especially plentiful near 
 the margin of the glaciated area. 
 
 The ground moraine left by an ice sheet is an unsorted 
 and compact deposit of rock waste. It is sometimes called 
 " boulder clay " from containing many large rocks packed in 
 a stony clay. It is known as "hard pan" to contractors, 
 who find much greater difficulty in digging foundations or 
 opening railroad cuts in the ground moraine than in the loose 
 sands and gravels that were washed forward from the edge of 
 the ice. The Scotch word till is the best general name for 
 this deposit. 
 
 Fig. 216. — An Esker. 
 
 The hills and valleys of New England are irregularly 
 sheeted over with compact ground moraine, here clog- 
 ging a valley, there smoothly cloaking a hill, and again 
 leaving a rocky surface bare. Mounds, ridges, and plains 
 of washed sands and gravels are also common in the val- 
 
CLIMATIC CONTROL OF LAND FORMS. 337 
 
 leys, the result of stream action at the margin of the latest 
 ice sheet during its retreat. The ridges are called eskers. 
 
 The till of New England contains many boulders, from 5 
 to 20 feet in diameter, and sometimes so plentiful on the 
 surface as to make agriculture impossible. Even where less 
 numerous, the 
 boulders must 
 often be gathered 
 from the fields and 
 thrown into heaps 
 or built into walls 
 before plowing is 
 possible. 
 
 Northwest 
 
 Ohio has been ng. 217.-AGlaeialBoulder. 
 
 converted from a region of hills and valleys into a smooth 
 plain by a heavy covering of till, at many points more 
 than 100 feet thick, and averaging 30 or more feet over 
 hundreds of square miles. 
 
 The till of Ohio is less stony than that of New England. 
 It furnishes good soil, for it consists of a thorough mixture 
 of waste from many kinds of rocks, gathered under the ice 
 and not exhausted by plant growth during its accumulation. 
 The till plain of northwest Ohio is for this reason more fertile 
 than the hilly country in the southeast part of the state, 
 beyond the limit of ice action. The same is true of large 
 areas in the northern central states as far west as the Dakotas. 
 
 Shallow lakes or marshy tracts occur here and there on the 
 till plains from Ohio to Minnesota. The streams of the region 
 bear every mark of youth. They follow narrow valleys, and 
 are frequently interrupted by falls where they have cut down 
 through the till to the rocky floor. In Minnesota, lakes are 
 
338 PHYSICAL GEOGRAPHY. 
 
 very numerous in hollows in the till and among the terminal 
 moraines. The falls and rapids of the upper Mississippi are 
 all of postglacial origin. Glacial action must have been com- 
 paratively recent (not many thousand years ago) in these 
 states, as the streams have been so little developed since the 
 ice disappeared. 
 
 In southern Iowa and northern Missouri there is an exten- 
 sive sheet of drift, burying the rock floor for miles together. 
 Here no lakes occur ; the numerous valleys are broad floored 
 and well opened ; few falls interrupt the even reaches of the 
 streams. The glacial epoch in which this well-dissected drift 
 sheet was dragged forward must have been much less recent 
 than that in which the smooth and undissected till plains of 
 northern Ohio and Minnesota were formed. 
 
 Drumlins. — In some glaciated districts the till was 
 here and there gathered beneath the ice sheet in smoothly 
 arched, oval hills called drumlins., commonly half a mile 
 
 Fig. 218. — A Drumlin. 
 
 or more long, and from 100 to 200 feet high, easily rec- 
 ognized when once known. They may be compared to 
 sand bars in rivers or to sand dunes under the wind, 
 all such built-up mounds occurring where more material 
 is brought than is carried further forward. 
 
CLIMATIC CONTROL OF LAND FORMS. 339 
 
 Numerous drumlins occur within an area enclosed by a 
 well-defined moraine in southern Wisconsin. Here the land- 
 scape presents a succession of arched hills, with flat marshy 
 plains between them. The streams wander along such courses 
 as the drumlins allow. The preglacial stream courses cannot 
 be determined, so heavy and extensive is the drift cover. 
 
 Hundreds of drumlins are found on the Ontario lowland of 
 western New York. On the uplands in central Massachusetts 
 many drumlins are cleared and farmed, in preference to the 
 more rugged rocky hills. Most of the islands in Boston har- 
 bor are drumlins. Many hills of this kind are distributed over 
 the lowland of Scotland between Glasgow and Edinburgh. 
 
 Marginal Lakes. — When an ice sheet retreated from a 
 land surface that sloped towards it, temporary lakes may 
 have been formed in the depression between the land 
 slope and the ice front (i, Fig. 214). The lake floors 
 received layers of fine silt, forming smooth plains when 
 laid bare after the disappearance of the ice. The shore 
 lines were marked by cliffs, beaches, and deltas of greater 
 or less size, now deserted by the waters that made them. 
 
 One of the most extensive glacial-marginal lakes has been 
 named Lake Agassiz. When at its greatest size, it stretched 
 hundreds of miles northward from Minnesota and North 
 Dakota into Canada. Its floor is in part a plain of till ; 
 in part covered with fine silts, nearly as level as the sea. It 
 is now traversed by the main stream and branches of the Red 
 river, whose narrow valleys proclaim the extreme youth of the 
 plain. Great wheat farms (Fig. 173) and pastures (Fig. 182) 
 now profit from the fertile soil. 
 
 The shore lines of the glacial Lake Agassiz are marked by 
 wave-made beaches and by the deltas of inflowing streams. 
 The latter are often so sandy that dunes have been formed on 
 
340 
 
 PHYSICAL GEOGRAPHY. 
 
 them by the winds. Following the shore lines southward, 
 they converge and almost unite at a slight depression in the 
 
 enclosing "height of 
 land " ; here the lake 
 outlet is found in a 
 well-defined channel, 
 a mile or more wide, 
 lea.ding southeast to 
 the Mississippi. The 
 Minnesota river, a 
 small stream in com- 
 parison with the great 
 current that once 
 flowed from the lake, 
 now wanders along 
 the floor of the chan- 
 nel. 
 
 Fig. 219. — The Glacial Lake Agassiz. 
 
 All the Great 
 Lakes were tempo- 
 rarily expanded while the retreating ice sheet obstructed 
 their discharge by the St. Lawrence ; they rose for a time 
 to higher levels and spread over the bordering lands. 
 Their shore lines, marked by cliffs and beaches, have been 
 traced for hundreds of miles ; their silted floors, bordering 
 the present lakes, form many fertile prairies. 
 
 When the northward discharge of Lake Michigan was thus 
 obstructed, the overflow ran southwest across a low " height of 
 land " to the Illinois river, and thus to the Mississippi. When 
 the ice retreated further, and Lake Michigan gained an outlet 
 through Huron, the waters sank to a lower level, and the for- 
 mer outlet remained as a low notch, which was afterwards a 
 " portage " for Indian canoes. The site of Fort Dearborn was 
 thus determined ; and from this small beginning in a favorable 
 
CLIMATIC CONTROL OF LAND FORMS. 341 
 
 situation between tlie East and the great Northwest the city 
 of Chicago has grown. To-day the ancient lake outlet has 
 been deepened by cutting an artificial canal ; a strong current 
 flowing through it from the lake carries the drainage of the 
 city to the Mississippi system. 
 
 When the lower St, Lawrence was blocked by the waning 
 ice sheet, the expanded Lake Ontario overflowed down the 
 Mohawk to the Hudson. The outflow cut down a flat-floored 
 channel at Rome, N. Y., and here is the ''long level" of the 
 famous Erie canal, where no lock is needed for many miles. 
 The beaches of the ancient lake shore are very distinct ; many 
 of them are used as naturally graded roadways. 
 
 The shore lines of the glacial-marginal lakes are no 
 longer level, as they must have been 'when formed. They 
 ascend a few feet in a mile to the northeast. Hence it 
 must be concluded that the land has risen in that direc- 
 tion during or since the retreat of the latest ice sheet. 
 
 Eecent observations have shown that the tilting of the land 
 is still in progress, causing a change of level of about half 
 a foot in 100 miles in a century. 
 
 A remarkable consequence is predicted if this change 
 of level continues. In a few thousand years, before 
 Niagara can lower the level of the upper Great Lakes 
 by wearing back the great falls between Lakes Erie and 
 Ontario, the uplift of the land in the northeast will have 
 raised the lake waters of southern Michigan high enough 
 to restore all the overflow to Chicago. Only Ontario will 
 then remain in the St. Lawrence system, while the Illinois 
 river will be greatly increased in volume. 
 
 Lake Basins. — The drainage of a glaciated region is 
 often greatly disordered by glacial action. At one i)lace 
 
342 
 
 PHYSICAL GEOGRAPHY. 
 
 a valley floor may be scoured out, producing a lake basin. 
 At another the irregular distribution of drift may divert 
 a stream to a new course, where it is now seen cutting a 
 steep-walled young valley with many falls and rapids. A 
 lake is often formed up stream from the drift barrier. 
 
 The Adirondacks, a well-dissected and subdued mountain 
 group, resemble the Black mountains of North Carolina in 
 many features, but are contrasted with them in the possession 
 of numerous lakes and in the frequent occurrence of gorges 
 
 J^S£^h ^.' ' 
 
 --^.^^-^ 
 
 
 S:"r-"^ ' -■'~ 
 
 
 Fig. 220. — Lake in the Adirondacks, New York. 
 
 Q' chasms ") and falls along the course of the outflowiug 
 streams. These peculiarities result from glacial action, which 
 the Adirondacks suffered in common with the other northern 
 parts of the country, but which the southern mountains 
 escaped. 
 
 Rapids and Waterfalls. — When a river carves terraces 
 in its drift-filled valley, it often happens that the new 
 course is entrenched on one side of the preglacial channel, 
 
CLIMATIC CONTROL OF LAND FOEMS. 343 
 
 and thus the stream comes upon a buried ledge. Here a 
 fall is formed; for the drift down stream is (relatively) 
 soon washed away, while the ledge is cut down much 
 more slowly. The valley is narrow where the river cuts 
 a gorge in the ledge. The alternation of waterfalls and 
 graded reaches in many northern rivers is thus explained. 
 
 The Merrimac is a famous river of this kind. Its falls 
 at Manchester, Lowell, and Lawrence have determined the 
 growth of great manufacturing cities. Rochester, Grand 
 Eapids, Minneapolis, and many other important cities have 
 grown up at the side of falls on rivers that have been turned 
 from their preglacial channels by glacial drift. 
 
 Where drift is plentiful and the preglacial relief of hill 
 and valley is moderate, rivers may be displaced far from 
 their former courses. Niagara is one of the most remark- 
 able examples of a large river on a new course ; the 
 upland that it crosses is a form of preglacial origin (an 
 upland of an ancient coastal plain), while the gorge and 
 falls are postglacial and extremely young. 
 
 It is probable that in preglacial time the region of the 
 Great Lakes was drained by a large river that followed in 
 a general way the main line of the St. Lawrence system ; but 
 the precise course of this ancient river has not been deter- 
 mined. Niagara is a new river, whose course was taken 
 across the upland between the Erie and Ontario lowlands 
 after the retreat of the ice sheet. At first the river fell over 
 the northern bluff of the upland. But as the plunging water 
 undermined the capping layers, the gorge was cut backward 
 through them. The falls have now retreated about seven 
 miles from their first position. An international boundary 
 line here follows the accidental path of the postglacial river. 
 A small fraction of the water in the river is now diverted 
 
344 
 
 PHYSICAL GEOGRAPHY. 
 
 from the falls and carried by a canal to supply power to 
 factories, to drive electric cars, and to furnish electric light 
 to cities. 
 
 Moraines and other drift deposits, forming new divides, 
 frequently cause important changes in the areas of river 
 systems. The headwaters of the Mississippi in northern 
 Minnesota are separated from Canadian drainage by drift 
 hills, Lake Itasca being but one of the innumerable lakes 
 held in drift basins, all of which are very modern features 
 in this ancient river system. Where the Mississippi rose 
 before the drift hills were formed, no one can say. 
 
 The divide between the upper Ohio and the St. Lawrence 
 systems is largely determined by moraines and drift barriers 
 south of Lake Erie. The same is true of many divides 
 and subdivides between the streams of the prairie states of 
 Indiana and Illinois. 
 
 Central Areas of Glaciated Regions. — The highlands of 
 eastern Canada, whence the ice sheets moved out to the 
 
 ^ \fKr'-^-~..- 
 
 
 Fig. 221. — Ice-Worn Kocks, Coast of Maine. 
 
 surrounding regions, and where the ice must therefore 
 have been of great thickness, possess relatively little drift. 
 
CLIMATIC CONTROL OF LAND FORMS. 345 
 
 Much of the surface is occupied by bare rock, clean 
 scoured, or by a thin stony soil. Here the action of the 
 ice sheet was chiefly destructive ; while on the surround- 
 ing region, as south of the Great Lakes, it was more 
 largely constructive. 
 
 Whatever soil the eastern Canadian highlands possessed in 
 preglacial times has been stripped away; it now lies in the 
 till plains and moraines south of the Great Lakes. The 
 generally even surface of the highlands (a worn-down old- 
 mountain region, somewhat dissected in preglacial time) now 
 consists of low rounded hills of firm unweathered rock 
 separated by shallow troughs that often hold lakes and 
 swamps both large and small. Many of the lakes lie in 
 eroded rock basins ; others are held behind drift barriers. 
 The undeveloped character of the streams is an indication of 
 the disorder in the drainage system produced by glacial 
 action. 
 
 The immaturity of the drainage of this region is imitated 
 in a small way when the snow and ice of winter melt from a 
 road, whose arched surface may be taken to represent the 
 highlands. Innumerable pools find outlets- by irregular rills ; 
 the rills have minute rapids on stony sills. During a rain on 
 such a roadway, the rills may be seen to deepen their channels 
 and lower the level of pools, or discharge them entirely; thus 
 imitating the changes that are progressing with relative 
 rapidity on the Canadian highland. 
 
 The highlands of Scandinavia repeat many of these fea- 
 tures, but their altitude is greater and their valleys are deeper. 
 The innumerable small lakes and the rapids and falls in the 
 streams of Sweden and Finland are all of glacial origin. The 
 great depth of the Norwegian fiords is by some explained as a 
 result of intense glacial erosion. 
 
 The ice sheets of the glacial period have vanished from 
 the northern United States and eastern Canada. The 
 
346 PHYSICAL GEOGRAPHY. 
 
 Indians that occupied this region when the Europeans 
 first landed have greatly decreased in number, disappear- 
 ing entirely in the more thickly settled districts. The 
 Indians are always considered in the study of American 
 history. The vanished ice sheets are of even greater 
 importance in American geography. 
 
CHAPTER XII. 
 SHORE LINES. 
 
 The Border of the Lands. 
 
 Next to the prospect gained from a lofty mountain, 
 the view of the sea from the border of a highland is 
 the most inspiring sight that the earth offers. To the 
 traveller from an inland country it is as if the shore line 
 marked the beginning of a new kind of world. There is 
 the mystery of the distant horizon, far beyond which 
 strange lands are hidden. There is the unceasing move- 
 ment of the waves as they roll upon the beach, and of the 
 tides as they slowly rise and fall ; and the thought comes 
 that thus the ocean has been rolling in waves, rising and 
 falling in tides, ever since the lands and the waters were 
 divided. With the sight of the vast ocean comes the 
 thought of unending time. 
 
 While the surface of the land has been for ages attacked 
 by rain and rivers, the border of the land has been 
 attacked by the sea. The sun warms the air in the torrid 
 zone, and thus the general circulation of the atmosphere 
 is established. The winds beat on the ocean and form 
 waves ; and the waves run ashore and dash in surf upon 
 the lands. The border of the land is worn back under so 
 constant an attack, and the waste taken from it by the 
 surf, as well as that washed into the sea by rivers, is 
 slowly carried away into deeper water by the waves, the 
 
348 
 
 PHYSICAL GEOGRAPBY. 
 
 currents, and the tides. In time the area of the land 
 would be greatly reduced by the invasion of the sea, were 
 it not for upheavals of the earth's crust by which the 
 land is now and then, here and there, renewed. 
 
 The contour of the land border exerts a strong control 
 on coastwise trade and on international commerce ; for 
 the dangers of the sea are not so much in the storms and 
 
 Fig. 222. — Sea Cliffs, Grand Manan, New Brunswick. 
 
 waves of the open ocean as in the shoals and reefs of the 
 shore. A rocky coast, descending in bold cliffs to a surf- 
 beaten beach, is justly dreaded when storm winds blow 
 landward. A safe harbor, protected from winds and 
 waves, is eagerly sought for when a vessel nears the coast. 
 The outlines of the shore deserve as careful study as the 
 forms of the land. 
 
SHORE LINES. 349 
 
 The Development of Shoee Lines. 
 
 Classification of Shore Lines. — Where the margin or 
 coast of the hmd dips under the sea, the water lies against 
 it and marks the shore line. The original outline of a 
 shore depends on the form that the land had when its 
 present attitude with respect to the sea was taken. Various 
 changes are afterwards made by the action of waves, cur- 
 rents, rivers, and other agents. 
 
 It lias been learned that in some parts of the world the sea 
 borders upon a smooth coastal plain that was once a sea bot- 
 tom (p. 118), and that in other parts it lies on the flanks of a 
 depressed mountain range (p. 195) ; hence this chapter may 
 be begun with an understanding that the attitude of the land 
 suffers greater or less change with respect to the sea; and that, 
 as the land rises or falls, the outline of the shore changes. 
 
 It will now be shown that some idea of the time since the 
 present attitude of a coast land was taken may be gained 
 from the form of bars built by waves off shore from a coastal 
 plain, from, the area of deltas built by rivers forward from 
 their mouths, and from the height of cliffs cut by waves on 
 headlands. 
 
 Shore lines in their original form, unchanged by sea 
 action, may be divided into two classes, according as 
 they are produced by uplift or by depression of the land. 
 The shore line is smooth and simple and bordered by 
 shallow water, where the sea lies on an uplifted sea 
 bottom. It is irregular and complicated and generally 
 bordered by relatively deejD water, where the sea lies on 
 a depressed land surface. Shore lines of the first class 
 border lowlands of weak strata ; they are comparatively 
 
350 PHYSICAL GEOGRAPHY. 
 
 liarboiiess and do not offer easy opportunity for traffic 
 between land and sea. Those of the second class gener- 
 ally have rocky headlands enclosing protected bays, where 
 harbors and settlements are favored. 
 
 There are exceptions to this simple classification. The sea 
 bottom is sometimes uneven, as where a hilly region has been 
 depressed. The sediments laid on such a sea floor accumulate 
 chiefly in the deeper parts, and thus tend to reduce the imeven- 
 ness of the bottom. If uplift occur before the bottom is 
 well smoothed, the new shore line will be irregular, although 
 belonging to the first class. 
 
 Shore Lines of the First Class. — The low plain of 
 Buenos Ayres dips gently beneath the sea, whose waters 
 are shallow for many miles off the simple shore line. 
 Large vessels cannot approach close to the land, except 
 where an artificial harbor has been dredged out. 
 
 When storm winds blow from the sea, they brush the water 
 upon the low coast and cause destructive sea floods ; dikes are 
 built along certain parts of the shore to keep the waters off. 
 
 Sand Reefs. — Along the shallow shores of low lands, 
 storm waves beat up the bottom sands and in time build 
 off-shore sand reefs, enclosing long, narrow lagoons. Roll- 
 ing surf beats on the outer beach of the reef, slowly grind- 
 ing the sand finer and finer, and sweeping the finest 
 particles far off shore ; but the reef is not easilj^ destroyed, 
 in spite of its loose texture, for about as much sand is 
 brought in from the sea bottom as is ground up on the 
 beach and taken away. 
 
SHOEE LINES. 
 
 351 
 
 The slow movement of tidal or wind-driven currents along 
 the beach gives it a straight or gently curved front. On-shore 
 winds blow sand from the beach, and build sand hills or dunes 
 of irregular form, sometimes 50 or 100 feet high, on the reef. 
 The sand drifts into the lagoon, making the inner border of 
 the reef somewhat irregular. Sediments are brought by streams 
 from the land, and, with the aid of salt-water plants, the lagoon 
 is gradually converted into a salt marsh at high-tide level, inter- 
 sected by numerous tidal channels, as in Fig. 223, b, e. 
 
 Fig: 223. — Diagrams of Coastal Plain Shore Lines. 
 
 Along the coastal plain of Texas the mainland shore line is 
 simple (except where interrupted by small bays caused by a 
 very slight depression of the plain after shallow valleys had 
 been cut in it). It is fronted by a sand reef, whose beach has 
 a remarkably smooth curvature. Much of the lagoon behind 
 the reef is only 5 or 10 feet deep. Galveston, the chief port 
 of the state, is built on the reef (Fig. 238), in order that its 
 wharves may reach deeper water than that of the lagoon, and 
 thus gain the advantage of traffic by seagoing vessels. 
 
352 
 
 PHYSICAL GEOGRAPHY. 
 
 M&^'Q 
 
 A peculiar series of sand reefs fringes the coastal plain of 
 North. Carolina (the mainland shore line being indented by 
 shallow " sounds " due to moderate depression of the region 
 after the uplift and dissection of the plain). Here three long 
 
 narrow reefs, with concave 
 outline to the sea, unite in 
 sharp angles pointing sea- 
 ward and forming Capes 
 Hatteras, Lookout (Fig. 
 224), and Fear. The 
 curved reefs appear to re- 
 sult from the action of 
 eddying currents between 
 the continent and the Gulf 
 Stream. Long sand shoals 
 
 Fig. 224. - The Hooked Spit of Cape Lookout. trail off shorC f rom the 
 
 capes, greatly endangering coastwise navigation. The reefs are 
 locally known as the " Banks"; the few people living on them 
 are called " Bankers." A small breed of horses, known as 
 " Banker ponies," run wild on the reefs. In the absence of 
 springs and streams, the ponies scrape away the sand until 
 they reach fresh ground water. Many of them are sold for 
 use on the mainland. 
 
 Cape Lookout^ 
 A T L A ]Sr Tl.C OCEAN 
 
 Inlets. — The flow and ebb of the tides, reenforced at 
 ebb by river discharge from the mainland, preserve open 
 passages or inlets through the reefs (Fig. 225). The 
 stronger the tides, the greater the number of inlets. 
 
 On the Texas coast, where the range of the tides is small, 
 there are few inlets ; one reef is unbroken for nearly 100 miles 
 northward from the mouth of the Eio Grande. Traffic between 
 land and sea is thus almost entirely cut off for long distances. 
 On the New Jersey coast the tidal range is stronger, and inlets 
 are more numerous. On the South Carolina coast the tides 
 
SHOBE LINES. 
 
 353 
 
 P;iP A jr /;, / c 
 s f) ' I- ^' 1) 
 
 are still stronger ; there tlie reefs are so frequently broken that 
 they do not interfere with traffic between land and sea. The 
 str on g tidal c ii r r e n t s 
 maintain inlet channels 
 deep enough for seagoing 
 vessels to enter the har- 
 bors of Charleston and 
 Savannah. 
 
 Tidal currents in in- 
 lets sometimes cause so 
 rapid a change in the 
 form and depth of the 
 channel that the inlets 
 are left blank on sailing 
 charts. Masters of ves- 
 sels must then trust to Fig. zas.-ATidallnlet and Delta. 
 
 local pilots to show them the best passage. The sand swept in 
 and out by the changing currents forms shoals known as tidal 
 deltas (Fig. 225) ; their outer edge forms a bar so shallow 
 that vessels must often wait for high tide before crossing it. 
 
 Advance and Retreat of Sand Reefs. — When sand is 
 brought (from the bottom or from elsewhere along shore) 
 in greater quantity than it is carried away, reefs broaden 
 on the seaward side and slowly advance into the sea 
 (Fig. 223, h). Reefs may thus grow to be a mile or more 
 wide. They retreat when more sand is lost than gained, 
 their dune sands slowly blowing back into the lagoon or 
 upon the lagoon marsh (Fig. 223, c). At last the lagoon 
 disappears, and the mainland is directly attacked and 
 slowly cut back in a long low bluff (Fig. 223, d). 
 
 At Atlantic City, a seaside resort on a sand reef in southern 
 New Jersey, the reef is broadening and gaining on the sea. 
 Some of the hotels facing the beach have been moved forward 
 
354 PHYSICAL GEOGRAPHY. 
 
 SO as to keep near the ocean front. Further north the' Kew 
 Jersey sand reefs are retreating ; for tide-marsh mud, matted 
 by lagoon plants, is foimd on the outer beach (Fig. 223, c). 
 
 Still further north the sand reef is absent, and the mainland 
 is cut back in a low blirff on which Long Branch, a noted 
 resort, is built. Severe storms cut away the base of the 
 bluff, sometimes undermining the houses above. 
 
 The low coast of the middle Netherlands has retreated 
 two miles or more in historic times ; for although the 
 attack by the sea is not so vigorous as on a coast exposed 
 to the open ocean, the land offers little resistance to the 
 waves and tides. A belt of dunes, half a mile or more 
 wide, lies inland from the smooth harborless beach. The 
 chief ports are on the lower courses of rivers, whose chan- 
 nels are broadened by the tides. 
 
 The Eomans built a castle back of the dunes, near the 
 mouth of the Rhine. In 1520 the dunes had blown inland, 
 grain by grain, leaving the castle close to the sea. In 1694 
 the castle stood in the sea, about half a mile from land. In 
 1752 it disappeared, destroyed by the waves. 
 
 In 1460 a church that had been built inside of the dunes 
 in the Dutch village of Scheveningen (near The Hague) was 
 reached by the sea. A new church was then built about a mile 
 inland, at the east end of the village. In 1574, the outer part 
 of the village having been gradually consumed by the waves, 
 new houses had been built east of the church, so that it stood 
 in the middle of the village. In a later century the new 
 church stood close to the shore, the body of the village having 
 moved beyond it. 
 
 Lake Shores. — Although the waves and currents of 
 lakes are weaker than those of the sea, their shores never- 
 theless exhibit all of the features above described for 
 
SHORE LINES. 
 
 355 
 
 the shores of the sea, with the exception of those clue 
 to tides. 
 
 The shores of the Great Lakes have wasted sufficiently to 
 develop bluff's or low cliff's of comparatively even front for 
 distances of many miles ; as along the southern shore of Lake 
 Erie, west of Buff'alo. Many other features of lake shores 
 imitating those of seashores might be mentioned. 
 
 Coastal Plain Cliffs. — As the margin of a coastal plain 
 is cut back by the sea (Fig. 223, d), and' the shore bluff in- 
 creases in length and height, longer and longer stretches 
 
 Fig. 226. — The Sea Cliffs of Normandy. 
 
 of the shore become harborless ; but it is seldom that 
 coastal plains terminate in cliffs of great dimensions. 
 Hence it must be inferred that uplift or depression of the 
 land generally occurs, interrupting the regular develoiD- 
 
356 
 
 PHYSICAL GEOGRAPHY. 
 
 merit of shore features before the sea has had time to cut 
 far back into the continent. 
 
 An exceptional case is found in northwestern France, 
 where the upland plain of Normandy (in general structure 
 similar to that of ancient coastal plains) fronts the sea in a 
 vertical sea cliff, 200 or 300 feet high, with gently curving 
 shore line for many miles. A large part of the plain must 
 have been consumed by the sea in the development of the 
 cliff. 
 
 The sea and land are here separated as if by a wall. The 
 plain is cultivated by its agricultural population close to the 
 
 top of the cliff. So 
 much land has been 
 cut away that the lower 
 trunks of many rivers 
 have disappeared, leav- 
 ing the upper branches 
 to enter the sea as inde- 
 pendent streams, as in 
 Fig. 227. The valleys 
 of the smallest streams 
 end in the cliff face, and 
 
 iiS. 227. - valleys in the CUffed Uplands of Normandy. ^j^^ gtrCamS fall tO the 
 
 beach below. Larger streams have cut their valleys down to 
 sea level, opening little harbors ; here alone are villages built 
 close to the shore line. The stream harbors are kept open 
 with difficulty, on account of the plentiful sand and cobbles 
 that drift along the beach. 
 
 There is good reason for believing that Great Britain has 
 been separated from the continent of Europe in great part by 
 the retreat of the sea cliffs on each side of the English 
 channel. Wolves and other large animals that formerly lived 
 in England as well as on the continent imply the existence of 
 
SHORE LINES. 357 
 
 a land connection, as they could not have crossed the waters 
 of the channel, and it is not probable that they were carried 
 across by man. 
 
 Effects of Depression and Elevation. — Depression of 
 the land may interrupt the orderly progress of seashore 
 action at any stage in the development of shore lines of 
 the first class. The sea then advances upon the lowland, 
 entering furthest along the valleys and thus producing a 
 shore line of the second class, but with moderate coastal 
 relief, upon which a new series of changes takes place. 
 
 The irregular shore line, with many sounds and bays along 
 the Atlantic coast from North Carolina to New Jersey, is a 
 good example of the effect of depression. Farmers would 
 have occupied the valley floors if the low land had not been 
 drowned; now fishermen gather from the bays "the harvest 
 of the sea." 
 
 Movements of elevation are as common as those of 
 depression, but their effects are generally less apparent. 
 The sea, retreating from its former position, begins the 
 development of a new shore line. The former shore line 
 may be marked by low ridges of sand reefs and dunes, or 
 by bluff-like terraces if an advanced stage of development 
 had been reached before elevation. 
 
 A low bluff, interpreted as a former shore line, has been 
 traced on the low coastal plain of Virginia and North Carolina 
 a short distance inland from the present seashore. Further 
 study will probably discover many more examples of this kind 
 on the Atlantic coastal plain. 
 
 The coastal plain of Mexico is not a perfectly smooth 
 inclined plain, but is benched by several low terrace-like steps, 
 which are believed to mark the action of the sea during pauses 
 in the elevation of the region. 
 
358 
 
 PHYSICAL GEOGRAPHY. 
 
 Fig. 228. — Diagram of an Irregular Shore Line. 
 
 Shore Lines of the Second Class. — The variety of 
 shore features here included is greater than in the first 
 
 class, because 
 the forms of 
 the land are 
 more varied 
 than those of 
 the sea bottom. 
 When an un- 
 even land 
 surface is de- 
 pressed and 
 partly covered by the sea, as in Fig. 228, ridges and hills 
 stand forth as promontories and islands ; valleys are en- 
 tered by arms of the sea ; protected harbors are plentiful 
 in the earl}'- stages of shore lines of this class. 
 
 The western coast of Norway is extremely irregular, hav- 
 ing many small and large islands along its " outer shore line," 
 while long arms of the sea, or fiords, carry deep water far 
 inland between steep mountain walls. 
 
 Sogne fiord, north of Bergen, penetrates the mainland 100 
 miles, its branching arms giving assurance that it is a sub- 
 merged valley. The depth of this and other Norwegian fiords 
 is believed to have been increased by the scouring action of 
 heavy ice streams from the highlands during the glacial period. 
 
 The walls of the fiords are so steep that roads can seldom 
 follow their shore lines; hence communication is chiefly by 
 water. Settlements are found at the head of the fiords and 
 on deltas built by inflowing streams. 
 
 An irregular coast favors the development of maritime 
 arts. Its outlying islands tempt exploration ; its protected 
 bays afford safe harborage even for small boats. The 
 
SHORI] LINES. 
 
 359 
 
 people occupying the coastal lands become expert sailors 
 and fishermen. 
 
 The numerous bays of southern Scandinavia were known as 
 viks to the people who occupied them 1000 years ago ; and 
 the inhabitants were therefore called vik-ings, or bay people. 
 
 
 : !!1:il|V'^ilV|^^;,,||l| 
 
 Fig. 229. — A Delta in a Norwegian Fiord. 
 
 They became bold marauders, invading and conquering the 
 more southern coasts of western Europe, by whose people 
 the vikings were called " Northmen." Normandy is to this 
 day named after these early sea kings. They were the first 
 European people to venture far out upon the ocean, and thus 
 almost 1000 years ago they discovered Greenland and other 
 parts of the western world. 
 
 The west coast of Patagonia (southern Chile) resembles 
 that of Norway. The Canoe Indians dwell here, — a primi- 
 tive people who find the steep slopes of the land so inhos- 
 pitable that they live almost entirely in open canoes on the 
 
360 PHYSICAL GEOGRAPHY. 
 
 water. A small fire is kept burning on a few sods in the 
 canoes, so that they may carry it from place to place. They 
 have no fixed habitations and make little use of the land, 
 except when they build temporary shelters of tree branches, 
 roughly thatched, in one cove or another where they stop for 
 a time to gather shellfish. 
 
 Lake Shores frequently imitate the features of sea- 
 shores of the second, class. When mountain valleys are 
 warped, the lake waters rise on the mountain flanks and 
 gain outlines of much regularity. Again, when lakes are 
 formed back of barriers of glacial drift, their waters may 
 rise upon an uneven land surface, transforming valleys 
 into bays and hills into islands. 
 
 Lake Lucerne, Switzerland, is an excellent example of an 
 irregular lake in a warped mountain valley ; its many arms 
 enter bays between bold promontories of great picturesqueness. 
 The Lake of the Woods, on the northern border of Minnesota, 
 overlaps the border of the rugged highland of Canada; its 
 outline is extremely irregular, and numerous rocky hills rise 
 as islands in the lake. The northern shore of Lake Superior 
 is of exceptional beauty, its bold headlands and outlying 
 islands separating many irregular bays, where the lake waters 
 have risen upon an uneven land surface. 
 
 Sea Cliffs and Benches. — The irregular seashore lines 
 above described are relatively little changed from the 
 outline produced by depression, except on the projecting 
 headlands and the outlying islands. Here the sea may 
 beat furiously, cutting a rocky bench beneath bold cliffs 
 and sweeping away the waste of the cliffs into deeper 
 water. Recesses are cut between outstanding ledges. 
 Isolated rock columns or stacks stand up on the rock 
 bench. 
 
SHORE LINES. 
 
 361 
 
 Angular rock fragments, weathered from a rocky coast, are 
 swept about by the clashing waves, and are in time rounded to 
 cobbles and pebbles. In storms the cobbles batter the rock 
 face and grind the rock floor, thus cutting a notch in the 
 edge of the land, forming a cliff that rises above sea level and 
 a bench that may be partly bare at low tide. At high tide 
 the waves roll across the bench and under-cut the base of the 
 cliff. Great masses of rock fall from the cliff, and for a time 
 protect its base ; but their shattered fragments are soon 
 dragged off the bench by the waves and dropped into deeper 
 water, and the attack on the cliff is then renewed. The force 
 of storm waves on an exposed coast suffices to move great 
 blocks of rock, 
 even exceeding 
 100 tons in weight. 
 The Orkney and 
 Shetland islands, 
 north of Scotland, 
 have lost much of 
 their former area 
 by the attack of the 
 sea. Headlands 
 break off in lofty 
 cliffs, some of 
 which are nearly 
 1000 feet high. 
 An isolated stack, 
 known as the " Old 
 Man of Hoy," rises 
 600 feet above the 
 sea. 
 
 Fig. 230. — The "Old Man of Hoy.' 
 
 Under the 
 strong attack of 
 the sea a steep coast may for a time be worn into a more 
 irregular outline than its original form. 
 
362 
 
 PHYSICAL GEOGRAPHY. 
 
 The stormy promontory of western Prance, beaten by heavy 
 waves and swept by strong tides, has thus gained a very ragged 
 outline. The shore is dangerous from the many rocky reefs 
 that rise to about half-tide height on the rock bench in front 
 of the cliffs. Light houses on such reefs must be of the very 
 strongest construction. 
 
 Sea Caves. — If one part of an exposed sea cliff is 
 weaker than the rest, the waves may excavate a cave in 
 it, cutting away at the head of the cave faster than the 
 overhanging roof weathers down. The length of such 
 caves may reach 20, 50, or more feet. 
 
 Fingal's cave, on the island of Staffa, west of Scotland, and 
 many other less famous sea caves are of this origin. The 
 " Ovens," on the coast of Mt. Desert, Maine, are shallow caves 
 of similar natiire. 
 
 Bay-Head Beaches. 
 
 Storm waves sweeping into little 
 bays or coves 
 carry with 
 them some of 
 the waste that 
 is washed from 
 the benches of 
 the enclosing 
 headlands and 
 from the shal- 
 low bottom 
 
 along shore. Beaches are thus formed around the bay 
 heads (Fig. 231), and layers of sediment are strewn over 
 the bay floor, while bare rock benches still front the head- 
 land cliffs. 
 
 Fig. 231. — Cliffs and Deltas on an Irregular Shore Line. 
 
SRORH LINES. 363 
 
 Bay-head or cove beaches present a smooth curve, concave 
 to the sea, on which the surf breaks evenly, quite unlike the 
 dashing and fretting waves on ragged headlands. The cob- 
 bles and pebbles thrown up on the beach during storms may 
 form a wall 5 or 10 feet above high tide, back of which a pond 
 or swamp is often enclosed in the valleys that previously 
 opened into the bay. The New England coast has hundreds 
 of small beaches of this kind between its rocky headlands. 
 
 Sea Cliffs and Beaches. — As a sea cliff is cut back, 
 the bench at its base becomes so broad that many cobbles 
 and pebbles are not at once washed away into deeper 
 water ; thus the beginning of a beach is made at the base 
 of the cliff, and 
 the rock floor 
 of the bench is 
 more or less 
 concealed. 
 
 The breadth 
 which a bench 
 must gain be- 
 fore a beach 
 forms upon it 
 is greater on a coast exposed to strong waves than in more 
 quiet water. In southwest Ireland, exposed to the violent 
 winter storms of the North Atlantic, the ragged headlands 
 have been cut back many hundred feet ; yet the benches have 
 only patches of cobbles here and there, and are still for the 
 most part without continuous beaches. 
 
 With further retreat of the cliff the beach will be more 
 continuously developed, and much of the material upon it 
 will be washed along shore in one direction or the other. 
 
 Fig. 232. — A Curved Shore Line. 
 
364 
 
 PHYSICAL GEOGRAPHY. 
 
 according to the movement of wind-driven waves and 
 tidal currents. The ragged cliff is then worn to a more 
 even front, as in Fig. 233, C 
 
 The smoother the front of the cliff becomes, the more 
 steadily maj- the tidal and wind-swept currents move along 
 it, di'agging the pebbles and sand jostled by the waves. 
 
 Fig. 233. — Diagram of a Retreating Shore Line. 
 
 Instead of following around the curve of every bay, the 
 currents swing across the little bays from headland to 
 headland, building curved spits^ or harrier beaches, with 
 the material brought from the cliffs. The bay heads are 
 in time enclosed and deltas (JS, F, Fig. 233) grow in their 
 quiet waters. The originally irregular shore line thus 
 becomes more and more simplified. As the beached head- 
 lands are cut back, the spits and barrier beaches retreat 
 with them, and the coast gains a smoother outline; thus 
 the development of the shore line approaches maturity. 
 
SHORi: LINES. 365 
 
 The dangers of the headlands are somewhat lessened when 
 their stacks and rocky reefs are worn away, and when the 
 bench at the cliff base is covered with a somewhat yielding 
 beach, instead of lying bare. At the same time the bays are 
 more or less completely closed, and are therefore less adapted 
 to seafaring settlements. 
 
 Tide-Swept Bays. — Strong tides may hinder the for- 
 mation of beaches across large bays, by preventing the 
 movement of cross currents from headland to headland. 
 The waste that is carried into such bays from the cliffs is 
 ground to fine mud by the tidal currents, and forms exten- 
 sive tidal flats about the bay head, bare at low tide. 
 
 The Bay of Fimdy and the Bristol channel are not only 
 kept open but are broadened by the action of the tides, which 
 increase in strength towards the bay heads. The estuary of 
 the Seine is open to the sea, in spite of the mature stage 
 reached by the cliffs on each side. Vessels entering the 
 estuary must keep to the channel between the mud flats, 
 although at high tide a broad sheet of water is spread before 
 them. 
 
 A British steamer, some years ago, ran aground on these 
 flats and was swung around square to the channel by the flood 
 tide. When the tide began to fall, the ebb current scoured a 
 hollow under the bow, and the vessel, unsupported bow and 
 stern, broke in two amidships. The next flood tide scoured 
 away the mud on which the middle of the broken hull had 
 been siipported ; and thus within a day the vessel sank and 
 was buried almost out of sight, a total loss. 
 
 Land-Tied Islands. — An island is sometimes attached to 
 the mainland by the backward growth of sand reefs that 
 are supplied with waste from its cliffs. The fortified Rock 
 
366 
 
 PHYSICAL GEOGRAPHY. 
 
 of Gibraltar, belonging to Great Britain, was originally an 
 island, but it is now tied to the mainland of Spain by a 
 
 broad sand reef. Part of the 
 reef is "neutral ground," occu- 
 pied neither by Spain nor Great 
 Britain. 
 
 Effects of Depression and Eleva- 
 tion. — When the further devel- 
 opment of irregular shore lines 
 is interrupted by depression, the 
 work of cliff-cutting and bay- 
 filling must be begun again, in 
 much the same way as before. 
 
 If a rugged land mass border- 
 ing the sea is uplifted, its former 
 cliffs and beaches may be found 
 at a greater or less distance in- 
 land from the new shore line. 
 As time passes, the cliffs and 
 beaches are weathered away and 
 
 EuKopa Poinf 
 
 Fig. 234. — Gibraltar. 
 
 the abandoned shore line becomes indistinct. 
 
 An elevated shore line, marked chiefly by rocky cliffs 
 and benches with occasional beaches, may be traced along 
 the greater part of the western coast of Scotland, at a 
 height of 20 or 25 feet above sea level of to-day. The 
 present shore line has, as a rule, reached a less advanced 
 stage of development than that reached by the elevated 
 shore line. 
 
 This elevated shore line forms a convenient bench along 
 which roads may be laid near the base of the slopes that 
 
SHORE LINES. 
 
 367 
 
 ascend to the highland summits. ' Villages and farmhouses are 
 often situated on the broader benches. Sea caves, roughly 
 walled in, sometimes serve as stables for the seaside farmers. 
 Other elevated shore lines are found at greater altitudes. 
 
 Fig. 235. — Easdale, a Village on an Elevated Shore Line, West Coast of Scotland. 
 
 The sediments spread over the bay floors of a former 
 shore line form, after elevation, local coastal plains between 
 rugged headlands. Cliffs are again cut on the headlands, 
 while smooth-curved beaches, sometimes many miles in 
 length, front the little coastal plains (Fig. 236). 
 
 Eegions of this kind are among the most bea,utiful parts of 
 the world. Many examples are found along the coast of Italy, 
 the Gulf of Salerno (next south of the, Gulf of Naples) being 
 one of the most perfect. 'When viewed from one of the higher 
 hills on the north, the bay sweeping to the headland on the 
 
368 PHYSICAL GEOGRAPHY. 
 
 south and the plain sloping forward from the inner moun- 
 tains, with the bright coloring of an Italian landscape, form a 
 picture long to be remembered. 
 
 
 Fig. 236. — Headlands and Bays. 
 
 The withdrawal of lake waters by a change of climate 
 (p. 318) has an effect on the condition of shore lines similar 
 to that produced by an elevation of the land with respect to 
 the sea. The cliffs and beaches that contour around the slopes 
 of the mountains of Utah, where the waves of Lake Bonne- 
 ville once beat, in many ways resemble the elevated shore lines 
 of western Scotland. 
 
 The western coast of Norwa}'^ is bordered for much of 
 its length by a belt of low land, sometimes as much as from 
 3 to 10 miles wide, from whose inner margin a bold ascent 
 leads to the highlands (Fig. 237). The low land is a 
 broad rock bench or platform, cut by the sea when the 
 land stood about 300 feet lower than now. A large part 
 of the population of western Norway dwells on this ancient 
 sea floor. 
 
 The former sea cliff, at the inner margin of the platform, is 
 from 500 to 1000 feet high. A number of rocky hills surmount 
 the platform, representing unconsumed islands of the former 
 
SHORE LINES. 
 
 369 
 
 time. The deep fiords of the highlands and many branching 
 channels traverse the bench, so that its outer part is now fringed 
 with islands. From this it is inferred that, after the cut- 
 ting of the platform and cliff, the whole region was uplifted to 
 
 Fig. 237. — The Coast Platform of Norway. 
 
 a greater elevation than it now has ; and while in this position 
 the valleys were eroded in the platform. Since then a depres- 
 sion has occurred, drowning the valleys and thus converting 
 the outer part of the plain into a swarm of islands, many of 
 them so small as to be occupied only by a single family. 
 
 The platform is wanting on certain parts of the Norwegian 
 coast ; here the sea beats directly against the border of the 
 highlands, as at Cape North, a great cliff 1000 feet high and 
 nearly vertical. It is probable that at such points the land 
 stands again in about the same position that it had while the 
 platform was carved. Here the work of making the platform 
 is still going on, and the shore line is becoming more and more 
 mature. 
 
 Delta Shore Lines. — Rivers tend to build their deltas 
 forward, and thus oppose the destructive action of the sea. 
 
370 PHYSICAL GEOGRAPHY. 
 
 The outline of a delta will therefore depend on the rela- 
 tive strength of these opposing tendencies, whether on 
 shore lines of the first or of the second class. 
 
 A small stream entering an ocean of strong waves or 
 tides can have little effect on the shore line. The action 
 of the waves will cut back the land in face of the effort of 
 such streams to build it forward. Tides of great range 
 will not only prevent small streams from building deltas ; 
 they may even widen the lower courses of the streams, 
 forming estuaries. 
 
 Streams that enter quiet waters build deltas without 
 interference from strong waves and currents. A small 
 river of a coastal plain, entering a lagoon back of a sand 
 reef, builds a delta of convex front with projecting arms 
 at the mouth of each distributary. 
 
 A river of this kind may find no break in the sand reef 
 opposite its mouth for the discharge of its waters into the sea. 
 The nearest inlet may be many miles to one side of the river 
 mouth. As the lagoon is filled by delta growth and tide 
 marsh, the river maintains a channel to the inlet, thus making 
 a square turn from its mainland course, and running for some 
 distance parallel to the coast. 
 
 Pedee river in South Carolina receives a branch from North 
 Carolina whose waters flow southwest parallel to the coast at a 
 little distance inland for 70 miles before reaching the point 
 where a break in the shore ridges allows an escape to the sea. 
 This seems to be a result of the process just described. 
 
 A great river entering the sea where the strength of 
 waves and tides is not excessive may build a delta which 
 shows little effect of sea action. Examples may be found 
 representing many stages between the extreme cases here 
 indicated. 
 
SHORE LIKES. 
 
 371 
 
 The powerful Mississippi discharges a great quantity 
 of land waste into the Gulf of Mexico. The waters of 
 the gulf are relatively shallow and the tides are • weak. 
 Here the outline of the delta seems to be governed en- 
 tirely by the action of the great river {Fig. 191); 
 
 The several distributaries of the Mississippi build low and 
 slender banks of mud on each side of their channels ; hence 
 the delta has several linger-like projections into the sea. In 
 order to increase the depth of water in one of the channels, or 
 "passes," jetties (dikes of wood and stone) have been built 
 forward beyond the end of the delta fingers, thus increasing 
 the current, and forcing it to scour the channel to a depth 
 sufficient for seagoing vessels to enter. 
 
 The Eio Grande, a large river, but much smaller than the 
 Mississippi, delivers land waste to the gulf in greater quantity 
 than the waves and currents 
 can altogether remove ; hence 
 its delta is built forward (Fig. 
 238). But the waves are strong 
 enough to smooth the outline 
 of the delta ; hence it has a 
 gently convex curve withoiat 
 finger-like projections. The 
 Brazos river, about midway 
 between the Mississippi and 
 the Eio Grande, also causes a 
 slight forward bowing of the 
 Texas coast ; here, as in the 
 Rio Grande delta, the lagoon, 
 that elsewhere lies behind the 
 sand reef, is replaced by the 
 delta deposits. It is probable 
 that the Colorado river (of Texas) has aided the Brazos in 
 building forward the coast line^ althoiigh it now enters a lagoon. 
 
 Fig. 238. — Deltas of the Texas Coast. 
 
372 PHYSICAL GEOGRAPHY. 
 
 Example for Review. — The coast of Maine is a worn- 
 down old-mountain region. Like southern New England, 
 the worn-down lowland has been uplifted and again dis- 
 sected, many valleys being thus formed between ranges 
 of hills. After the valleys were formed, a movement of 
 depression (400-600 feet) converted many of them into 
 bays reaching far inland. The land stood in this de- 
 pressed position during the glacial period ; and while the 
 ice sheet was melting away, much drift was washed from 
 it into the long narrow bays. 
 
 Since then a movement of elevation (about 300 feet) 
 has laid bare the bay floors, where marine clays now form 
 an irregular coastal plain enclosed by hills that were for- 
 merly promontories and islands. The streams from the 
 interior, flowing forward over the clay plains, have begun 
 to dissect them, so that their surface is now uneven. The 
 coast line is still very irregular, because the postglacial 
 elevation was not so great as the previous depression. 
 
 The farmed fields of southern Maine are very generally on 
 the smoother parts of the clay plam. The rocky hills are 
 wooded, except where covered with, enough drift to provide a 
 soil worth cultivating. The peninsulas and islands are com- 
 ing to be occupied as summer resorts by people from the 
 interior states. 
 
 Effect of Climate on Shore Lines. — Shore lines, like 
 land forms, are affected by climate ; not only by differ- 
 ences between regions of on-shore and off-shore winds, 
 where waves and currents are stronger or weaker, but 
 even more by differences of temperature. 
 
 In polar seas the land is often bordered by a fringe of 
 
SHORE LINES. 
 
 373 
 
 ice called the ice foot. This is in part formed of fresh 
 water that freezes on entering sea water whose tempera- 
 ture is below 32°. During the winter the ice foot usu- 
 ally remains attached to the land, unless broken by strong 
 tides ; in summer it may melt, loosen, and float away. 
 
 The ice foot is often used as a 'longshore roadway for 
 sled travel by Eskimos and Arctic explorers. When loose 
 from' the lands and moved on and off shore by the tides, 
 stones are dragged beneath it, grinding the shore rocks round 
 and smooth. 
 
 In torrid seas, not exposed to strong surf, the shores 
 may be invaded by certain kinds of trees, forming a net- 
 work so dense as to make landing difficult. 
 
 The mangrove is the most important tree of this kind. It 
 grows freely in shallow sea water on low and muddy shores, 
 and protects the land 
 from the waves. Roots 
 grow out from the 
 trunk above water 
 level. Crabs and oys- 
 ters live on the stems 
 and roots. Birds oc- 
 cupy the branches. 
 Muddy sediments ac- 
 cumulate in the quiet 
 water among the trees, 
 and thus the land 
 gains on the sea. 
 Shores occupied by 
 mangrove swamps are 
 
 dismal as compared with the shell-strewn beaches of sand and 
 pebbles, beaten by trade-wind surf. 
 
 Fig. 239. — Mangrove Tree. 
 
374 PHYSICAL GEOGRAPHY. 
 
 Coral Reefs. — The shallow waters of continental bor- 
 ders or mid-ocean islands in the warmer seas are commonly 
 occupied by coral reefs composed of the limy framework 
 of coral animals. Living corals are found chiefly on the 
 outer side of the reef where they grow in the shallow 
 water much in the same way that a thicket of small bushes 
 grows on the land. 
 
 Eeef-building coral animals take the limestone needed for 
 their skeletons from solution' in sea water. They are not 
 found where the mean temperature of the water in the cool- 
 est month is lower than 68° F., and they do not live at depths 
 greater than about 20 fathoms. There are many different 
 species, but all are fixed to the bottom. Some branch in 
 bush-like forms 1 or 2 feet high (" stag-horn coral ") ; some 
 grow in round masses from 1 to 3 feet in diameter ("brain 
 coral"). 
 
 The shores of a volcanic island in water of fitting tempera- 
 ture might be colonized by corals, for the young forms float 
 and are carried far and wide by ocean currents. The follow- 
 ing succession of reef might then be produced. 
 
 Fringing Reefs. — When reef-building corals first take 
 possession of a new shore, their growth extends upward 
 from the shallow bottom and outward into the surf, where 
 
 the constant movement 
 of the sea water supplies 
 them, with food. When 
 they are detached from 
 the bottom by severe 
 
 Fig. 240. — A Frmging Reef. i ti t i , 
 
 storms and rolled about 
 by the waves, the larger fragments of their limy framework 
 are thrown back towards the land, forming shoals, and 
 
SHORE LIITES. 375 
 
 sometimes rising in a beach a little above sea level ; the 
 finer particles are carried off shore and strewn over the 
 sloping bottom towards deep water. The reef thus broad- 
 ens, forming a fringe close along the shore line. At this 
 stage it is called a friyiging reef. 
 
 Strips of fringing reef are found on the equatorial coast of 
 east Africa, along parts of the Brazilian coast, at various points 
 on the coast of Cuba and elsewhere in the West Indies, and 
 bordering many islands in the Pacific, as the Hawaiian and 
 other groups. The Galapagos islands in the eastern Pacific, 
 close to the equator, are free from reefs, because of the low tem- 
 perature of the water which there comes in a strong current 
 from far southern latitudes, or which rises from below the sur- 
 face along the Peruvian coast when the winds blow off shore. 
 
 Fringing reefs are generally interrupted opposite the 
 mouths of streams, where land waste makes the bottom 
 muddy and unfit for coral growth. Water passages are often 
 preserved back of the reef, close to the shore. Natural harbors 
 are thus provided, well protected from the surf that breaks 
 on the shoals and beaches of the outer reef. 
 
 Barrier Reefs. — A fringing reef broadens by the out- 
 ward growth of the corals, and the submarine slope is 
 built forward by the sup- 
 ply of coral fragments. 
 At the same time water 
 supplied by rain, by 
 streams from the land, 
 and especially by the 
 surf that rolls over the reef, slowly dissolves and washes 
 away the inner part of the reef where living corals are 
 few or wanting. Thus the reef may come to be separated 
 
 Fig. 241. — A Barrier Reef. 
 
376 
 
 PHYSICAL GEOGRAPHY. 
 
 from the land by a shallow lagoon a mile or more wide ; 
 and in this way a fringing reef may change to a barrier reef. 
 
 Fig. 242. — Part of the Great Barrier Reef of Australia (as seen at low tide, looking towards 
 the mainland). 
 
 The Great Barrier reef stretches along the northeast coast 
 of Australia for about 1000 miles, the largest reef in the world. 
 It is from 20 to 50 miles from the mainland, mostly beneath 
 
SHORE LINES. 
 
 377 
 
 Fig. 243. — Diagram of Part of a Barrier Reef. 
 
 sea level, interrupted by numerous inlets, and bearing a few- 
 low islets. The sea outside descends rapidly to great depths ; 
 the water inside is shallow (from 10 to 40 fathoms). 
 
 Effects of Elevation. — If a slow uplift occurs, corals 
 will continue to grow 
 on the outer face of 
 the reef. At the same 
 time, rainfall and surf- 
 overflow may wear and 
 dissolve away the up- 
 lifted parts so tha,t the 
 reef gains little height 
 above sea level, and the lagoon is kept open beneath sea 
 level. It therefore seems possible that barrier reefs may 
 occur in regions of very slow elevation. 
 
 If a relatively rapid uplift occurs, a reef may be raised 
 above sea level, forming a terrace-like bench above the 
 new shore line. Ele- 
 vated reefs are known 
 along many coasts in 
 the torrid zone. 
 
 An uplifted reef forms 
 a bench at a height of 
 about 30 feet, with a 
 breadth of a mile or less, 
 bordering much of the northern coast of Cuba. Corals are 
 easily recognized in the ragged structure of the reef. It is 
 seldom interrupted, except where rivers cut their valleys 
 through it. The sea has worn a low cliff in the front of 
 the bench ; from the cliff top one may look down upon the 
 modern fringing reef now growing in the sea. 
 
 M 
 
 ^W 
 
 '^X 
 
 h^' 
 
 ®^^^r^~~~~i 
 
 1 
 
 ...A .. .. 
 
 
 mi ! 
 
 M^ 
 
 244. — Diagram of Part of an Elevated Reef. 
 
378 
 
 PHYSICAL GEOGRAPHY. 
 
 Elevated reefs are relatively weak and cavernous struc- 
 tures ; they may be worn down much more rapidly than 
 the strong foundation rocks on which they are often 
 based. In this way an elevated reef may be converted 
 into a barrier reef again, the lagoon being dissolved out, 
 while new coral growth takes place on the outer margin. 
 Barrier reefs of this kind may be recognized as long as the 
 
 island remnants of the 
 elevated reef are not 
 entirely worn away. 
 
 Elevated reefs in vari- 
 ous stages of destruction 
 occur on the Fiji islands 
 up to heights of 800 feet. 
 Many of the barrier reefs 
 of this group seem to have 
 grown on the outer edge of platforms formed by the almost 
 complete wearing away of elevated reefs, much of whose 
 surface is now worn and 
 dissolved away even a lit- 
 tle beloMf sea level. 
 
 Effects of Depression. 
 — If a reef is depressed 
 faster than corals can 
 grow upward, the depth 
 of water above it will 
 
 Fig. 245. — Diagram of Part of a Denuded Keef enclosed 
 by a Barrier Reef. 
 
 Fig. 246. — Diagram of Part of a Drowned Keef. 
 
 increase to a greater measure than that in which reef- 
 building corals can live. Then the polyps are " drowned " 
 and the reef is " dead." 
 
 The Chagos Bank, in the Indian ocean, 1000 miles south 
 of India, is a broad shoal measuring about 100 by 75 miles, 
 
SHORE LTNES. 
 
 379 
 
 at a depth of 40 or 50 fathoms. It is bordered by a ridge 5 or 
 10 miles v/ide and 15 fathoms deep, on which a rim about 1 
 mile wide rises to within 5 or 10 fathoms of the surface, bear- 
 ing a few low islets here and there with some living coral. 
 The banks appear to have once been an extensive coral reef, 
 now drowned. 
 
 The Marquesas islands in the eastern Pacific are a group 
 of dissected volcanoes of irregular outline and steep slopes, 
 with deep water close to shore, as if recently depressed. 
 Cliffs are already cut in the headlands, and the bays contain 
 beaches strewn with cobbles, among which coral fragments 
 occur. There are no living reefs around the shores, although 
 the temperature of the water is fitting and reefs abound in 
 islands to the southward. It is probable that while the Mar- 
 quesas stood higher, reefs were formed around them, and from 
 these the coral cobbles of the present beaches have most likely 
 been derived ; but the depression by which the present outline 
 of the islands was determined appears to have been too rapid to 
 permit the upward growth of the reefs to keep pace with it. 
 
 Atolls. — If a slow depression takes place, it may be 
 counteracted by the upward growth of the reef corals. 
 Then the reef will be 
 preserved ; it may even 
 
 Fig. 247. — A Large Atoll. 
 
 increase in size by out- 
 ward growth during de- 
 pression, as in Fig. 247. 
 At the same time, the 
 lower slopes of the island around which the reef first 
 fringed will be drowned and its valleys will be occupied 
 by bays ; if depression continues, the central island may 
 altogether disappear, leaving only the encircling reef of 
 oval or irregular outline around the lagoon. Such reefs 
 are called atolls. 
 
380 PHYSICAL GEOGRAPHY. 
 
 If a volcanic island witliin a barrier reef does not suffer 
 uplift or depression, it must be slowly worn down closer and 
 closer to sea level, while its barrier reef is growing outward. 
 But it is doubtful whether the resistant rocks of such an island 
 could be worn away below sea level, so as not to appear in a 
 lagoon whose depth may be from 20 to 50 fathoms. For this 
 reason the theory proposed by Darwin, that atolls result from 
 the slow depression of islands with fringing or barrier reefs, 
 has had general acceptance. 
 
 Life on Atolls. — As coral islands are limited to the 
 warm and uniform climate of the oceans in low latitudes, 
 mostly within the torrid zone, they are bordered with 
 
 Fig. 248. — An Atoll, or Coral Island. 
 
 waters teeming with marine life, and many of. them bear 
 a luxuriant vegetation. The natives of the larger atolls 
 lead easy and indolent lives, but their progress towards 
 better conditions than those of savagery is hindered by 
 the small variety in their surroundings and by their dis- 
 tance from lands of more varied form and products. 
 
SEORE LINES. 381 
 
 Although, one of the most wonderful objects in nature, 
 a lonesome atoll affords little opportunity for human 
 development. 
 
 The small height of atolls subjects them to the danger of 
 being overwhelmed by earthquake waves. Hurricanes some- 
 times come upon them unobstructed from the open sea, sweep- 
 ing violent surf far up the beaches ; the storm winds break 
 down the cocoanut palms on which the natives dej)end largely 
 for food and for the materials, of many of their simple arts. 
 There are no streams, but fresh water supplied by rains 
 may be found a little below the surface. The thin soil has 
 little variety of mineral matter, but floating pumice is often 
 cast ashore from distant volcanic eruptions, and some of the 
 islanders have learned to gather and pulverize it to use as 
 a fertilizer for their little fields. Floating logs sometimes 
 drift upon the islands, and their roots occasionally carry 
 stones of firmer texture than coral rock (for example, frag- 
 ments of dense lava from a volcanic island) ; whetstones, 
 pestles, and mortars are made from these chance supplies. 
 
 Although birds are plentiful, there wefe no mammals on 
 coral-islands until rats and mice came ashore from vessels; a 
 few domestic quadrupeds have occasionally been imported by 
 foreign residents. 
 
 Until the nineteenth century the natives of most of the 
 Pacific islands knew nothing of the rest of the world. Their 
 highest art was seen in the making of sail canoes, in which 
 they voyaged between the islands of their archipelagoes. It 
 was probably when blown from an intended course in these 
 small boats that the islands were originally peopled from 
 larger lands. 
 
 The Tuamotu or Low archipelago in the eastern Tacific 
 contains 80 islands, only 4 of which rise more than 12 feet 
 above sea level. Most of the islands are atolls. The narrow, 
 irregular reefs are partly below, partly above, tide level, but 
 only ^\ of their land area is habitable. The islands are gen- 
 
382 ■ PHYSICAL GEOGRAPHY. 
 
 erally higher on the windward (east and southeast) side, where 
 wind and wave supply coral sand to make beach ridges. On 
 the leeward side the surf is not so strong, and here many 
 channels are kept open by outflowing currents. 
 
 Like fringing and barrier reefs, atolls may be elevated. 
 After elevation they may be worn down and again con- 
 verted into atolls of the usual form without any central 
 island. 
 
 Metia, one of the Tuamotu group, seems to be an elevated 
 atoll, with cliffs cut on the windward side. It measures about 
 4 by 2^ miles, with a height of 250 feet. It consists entirely 
 
 Fig. 249. — Metla, an Elevated Coral Island. 
 
 of limestone, containing fragments of coral here and there, but 
 generally of fine texture, as if composed of the coral sand and 
 mud that formed the deeper parts of the former atoll. Many 
 caverns are found in the limestone. 
 
 Some of the atolls in the Fiji group are best accounted for 
 by the denudation of elevated reefs, remnants of which are 
 still to be seen standing somewhat above the general level. 
 In these islands the corals that now fringe the atoll have had 
 little influence on the form of the reef ; they only form a crust 
 upon the platform of the denuded elevated reef. 
 
 If the depression of an atoll is at such a rate that not 
 enough coral waste is supplied to build the submarine 
 
SHORE LINES. 
 
 383 
 
 slope that descends into deep water, the outer margin of 
 the reef may be slowly worn away, and thus the atoll will 
 decrease in size. It 
 may in time disappear 
 entirely. 
 
 Fig. 250. — A Smaii Atoll. 
 
 Honden island, in the 
 Tuamotu group, is about 
 3 miles in diameter, wit 
 a small central lagoon. 
 The reef rises 12 feet above sea level, and is occupied by a 
 belt of large forest trees. When visited by 'explorers, about 
 1840, the island was 'tenanted only by birds, so tame that 
 they were taken from the trees as if they had been their 
 flowers. 
 
 Jarvis island is close to the equator in longitude 160° W. 
 It is about a mile in diameter. Its sandy surface is a little 
 depressed at the center, but does not hold a lagoon. This is 
 one of the smallest known coral islands. 
 
APPEIsrDIXES. 
 
 APPENDIX A. 
 
 Problem of Eudoxus (p. 11). — Eudoxus was one of the 
 
 earliest of the Greek philosophers to demonstrate that the 
 earth is not flat. His argument may be outlined as follows : 
 Let NABCS be a part of a meridian line ; the lines DAE, 
 FBG, and ^CJ" representing the horizons of observers at the 
 points A, B, and C. Each observer can see only those parts 
 of the sky that stand above his horizon. If the observer at 
 B travel to C, he 
 
 will lose sight of 
 the stars X (sup- 
 posed to be at a 
 great distance away 
 in the direction of 
 the arrows), while 
 the stars -^ will come 
 into sight beneath 
 the stars Y that he saw before. Eudoxus was in some such 
 way as this led to argue that as he went north or south, his 
 horizon plane tilted one way or the other, and hence that the 
 surface of the earth must be convex. We may imagine that 
 he "said : " Observations of this kind might be made by any 
 one who travels north or south. On whatever meridian the 
 observations are made, the result is the same. All meridians 
 seem to have the same curvature, as if they were all circles 
 of the same size. Hence the earth must be a sphere." 
 
 Fig. 251. — Globular Form of Earth shown by Visibility of Stars. 
 
386 
 
 PHYSICAL GEOGRAPHY. 
 
 APPENDIX B. 
 
 Problem of Eratosthenes (p. 12). — Eratosthenes was the 
 first to measure the size of the earth. His method may be 
 easily imitated as follows : A hill having north and south 
 slopes, AD and AB (Fig. 252), may be taken to represent 
 part of a small earth, FBADG. Set up two boxes, with ver- 
 tical sticks nailed 
 to their sides, at the 
 points B and D, on 
 a north and south 
 line ; measure the 
 distance BAD over 
 the curve of the hill. 
 (If no hill is avail- 
 able for this experi- 
 ment, set up two 
 boxes on the north 
 and south sides of a 
 school yard, tilting 
 each box slightly away from the other, as in Fig. 253, and 
 representing the curve of the imagined earth by a series of 
 stakes set up between the boxes.) 
 
 The vertical sticks BJ and DK may then be regarded as 
 extensions of the local radii 
 OB and OD of the imagined 
 earth FBADG. At midday, 
 when the sun passes the me- 
 ridian, the parallel rays of 
 sunshine S'M and S"N fall 
 in the same plane with the 
 radii OB and OD. Measure the shadows cast at midday 
 by the sticks J and K on the upper surface of the boxes. 
 
 Fig. 252. — Sun Altitudes on the Two Slopes of a Hill. 
 
 Fig. 253. — Sun Altitudes measured in a School Yard. 
 
APPENDIXES. 387 
 
 Knowing the length of each stick above the box surface, the 
 angles OJM and OKN may be determined. The angle 
 BOD or J OK equals the difference between OJM and 
 OKN. (JOK = JMK - OJM. But as &'M and &^N are 
 parallel, JMK = OKN ; hence JOK = OKN - OJM.) Then 
 we have the proportion : 
 
 Angle JOK : 360° = distance BAD : circumference. 
 
 Eratosthenes learned that at Syene (the modern Assouan) 
 on the Nile, vertical objects cast no shadow at noon on June 
 21. On the same day at Alexandria, about 5000 stadia north 
 of Syene, he measured the angle between the sun's noon ray 
 and a vertical rod, and found it to be 7^°. As the earth- 
 radius at Syene lay in a line with the sun's ray, while the 
 radius at Alexandria made an angle of 7-^° with the sun's ray, 
 he saw that the angle between these radii at the earth's cen- 
 ter must be 7^°. He then made the proportion : 
 
 7^° : 360° = 5000 stadia : circumference of the earth. 
 
 There is some uncertainty as to the accuracy of the meas- 
 ure made by Eratosthenes, because the length of the stadium 
 is not accurately known in terms of modern units of distance ; 
 but as the distance between Syene and Alexandria is about 
 500 miles, his result could not have been far from the truth. 
 
 The problem of Eratosthenes may be repeated in essence by 
 the students of two schools at places about north and south 
 of each other ; for example, at Cleveland and Savannah, or at 
 Chicago and Mobile. At noon upon a certain day, agreed 
 upon by correspondence, determine the angle between a ver- 
 tical rod and the sun's rays at each place. Measure the dis- 
 tance between the two places (better, the meridian distance 
 between their parallels of latitude) on a good map. Then 
 take the difference between the two angles and repeat the 
 above proportion, 
 
388 PHYSICAL GEOGRAPHY, 
 
 APPENDIX C. 
 
 Latitude and Longitude (p. 17). — On tlie supposition 
 that tlie eartli is splierical, the arc of a meridian from a 
 given point to the equator measures the latitude of that 
 point. Tlie arc of the equator between two meridians meas- 
 ures the difference of longitude between all places on those 
 meridians. 
 
 The terms latitude and longitude, or " breadth " and 
 "length," were introduced in ancient times with reference 
 to the countries around the Mediterranean Sea, where the 
 dimensions of the known lands were greater east and west 
 than north and south. As exploration proceeded, the same 
 terms were extended all over the globe, although no longer 
 appropriate in their meaning. 
 
 Latitude. The latitude of a place may be roughly deter- 
 mined as follows : 
 
 In consequence of the rotation of the earth, the sun and 
 stars seem to move around us in circles. The circles thus 
 traced in the sky are arranged like parallels of latitude on 
 the earth ; they are all parallel to one another and have the 
 north and south poles of the sky in common. 
 
 A few hours' observation on a clear night will aid in 
 understanding the apparent motion of the stars. Several 
 rods may be used as ''pointers." Set a rod so that it points 
 to a star. After an hour or two, compare the direction of 
 the star with that which it had before, as indicated by the 
 pointer. If observations of this kind are made on various 
 stars in different parts of the sky, it will be found that over 
 the northern horizon the stars move in arcs of relatively 
 small circles about the sky pole. About 90° away from 
 the pole, and therefore near the equator, the stars move 
 much more rapidly in arcs gf larger circles. By leaving the 
 
APPENDIXES. 389 
 
 pointers unmoved till the next evening aucl beginning obser- 
 vations a little earlier than before, the stars may be seen to 
 approach and pass their previous positions. Hence each star 
 makes a whole circuit in a day (strictly, in 23 h. 56 min.). 
 The path of the sun should be traced in the same way. 
 
 Observers in temperate latitudes may see a good number of 
 stars in the neighborhood of the sky pole that do not sink 
 below the horizon in their daily circuits ; these are called 
 circumpolar stars. 
 
 For an observer at the pole, the horizon would stand par- 
 allel to the star circles. As the observer moves towards the 
 equator, his horizon is more and more inclined from its posi- 
 tion at the poles, and makes a larger and larger angle with 
 the star circles. At the equator, the horizon and the star 
 circles are at right angles to each other. The angle formed 
 by the plane of the horizon with that of any star circle is, 
 therefore, the measure of the arc of the meridian from the 
 pole to the observer. The difference between this arc and 
 90° is the local latitude. Any student who is familiar with 
 the apparent movement of the stars across the sky may 
 thus roughly estimate his position with respect to pole and 
 equator. 
 
 In consequence of the annual motion of the earth around 
 the sun, the (apparent) diurnal motion of the sun is not 
 strictly in a circle parallel to the star circles, but is in a 
 slightly oblique line ; the sun thus moves north and south in 
 the sky in the course of a year. But in a single day the sun's 
 path does not depart significantly from a star circle. As the 
 sun may be observed much more conveniently than a star, 
 it may be used for a first rough determination of latitude, in 
 the following manner : 
 
 Drive a peg into the ground and to its top attach a pointer 
 that may be easily turned to any part of the sky. At an 
 early morning hour direct the pointer towards the sun (it 
 
390 
 
 PHYSICAL GEOGRAPHY. 
 
 will be properly set when turned so that it casts a shadow 
 no larger than its cross section on a paper held behind it), 
 and record the position of its end by driving a stake into 
 the ground so that the top of the stake shall just touch the 
 end of the pointer. 
 
 Repeat this process several times during the day. The 
 tops of the stakes will then mark part of a circle whose 
 plane is parallel to that followed by the sun. Standing at a 
 little distance to one side, the stake-toj) circle may be seen 
 edgewise, so as to appear as a slanting straight line, AD. 
 
 The angle I) AC that this 
 line makes with the hori- 
 zon measures the arc of 
 the meridian from the ob- 
 server to the pole. The 
 angle DAU that it makes 
 with a vertical line meas- 
 ures the latitude, as ordi- 
 narily counted from the 
 equator. The advantage 
 of this method is that it can be performed without knowing 
 the position of the sun with respect to the sky equator. 
 
 The latitude of a place is also measured by the altitude of 
 the pole of the sky. (Atmospheric refraction is not consid- 
 ered in any of these problems.) At the equator the sky pole 
 would lie on the horizon ; and for every degree of latitude 
 that the observer moves north, his horizon would dip a 
 degree below the sky pole. The North star is about a degree 
 and a half from the north pole of the sky ; but, in rough 
 measures, the altitude of the North star may be taken as 
 equal to the latitude. 
 
 Latitude may be determined by measuring the noon alti- 
 tude, or meridian altitude, of the sun, provided the angular 
 distance of the sun from the sky equator is known. The 
 
 .,.M„.,,j-^^. .;■ 
 Fig. 254. — Sun-Circle Method of Measuring Latitude. 
 
APPENDIXES. 
 
 391 
 
 meridian altitude of the sun is SAC (Fig. 255). If its angu- 
 lar distance from the sky equator is SAD, then SAC — SAD 
 -— DA C = the meridian altitude of the sky equator = 90° 
 minus the local latitude. This method is commonly employed 
 for determining the latitude at sea, the sun's position with 
 respect to the equator being given in the Nautical Almanac. 
 
 On a spherical earth latitude might be defined as the angle 
 in a meridian plane, limited by the radii drawn to the equator 
 and to the place of observation. But on the spheroidal earth 
 latitude must be defined, not by the angle between the radii, 
 but between the verticals AM and QM, or between the hori- 
 zon planes AB and QB, for CBQ = AMQ. Latitude may 
 
 Pig. 265. — Latitude on a Spheroidal Earth. 
 
 then be defined as the angle between the tangents to a 
 meridian at the place of observation and at the equator. 
 
 Longitude. There is no meridian from which longitude 
 may be counted as naturally as latitude is counted from the 
 equator; but it is customary in English-speaking countries to 
 take the meridian of the astronomical observatory at Green- 
 wich on the Thames below London as the prime meridian. 
 Difference of longitude may be determined as follows : 
 
 Imagine two observers on different meridians. Let each 
 observer set his clock to noon, when the sun passes the plane 
 
392 PHYSICAL GEOGRAPHY. 
 
 of his meridian. (This moment may be determined by noting 
 the time when a vertical rod casts the shortest shadow on 
 a horizontal surface.) If the two observers could then com- 
 pare their clocks, the difference of the two local tiiaes would 
 give them their difference of longitude, reckoned in hours 
 and minutes (24 h. = 360°). The comparison of times may 
 be made when a lunar eclipse happens, as follows : 
 
 The eclipse being caused by the entrance of the moon into 
 the earth's shadow, it must be seen at the same moment by 
 all observers. Hence, if two observers note the local time of 
 the beginning of a lunar eclipse and then by correspondence 
 compare their records, the difference of the local times gives 
 their difference of longitude. This method was first employed 
 by Strabo, about the beginning of the Christian era. The 
 date of eclipses may be found in almanacs. 
 
 Another method involves the carrying of a timepiece 
 from one place to the other. Let the students in two 
 schools, as in Cincinnati and St. Louis, set their watches to 
 noon at the passage of the sun across their local meridians. 
 Then let either school send a watch by express to the other 
 school. A comparison of local times can then be made. The 
 result can be confirmed when the watch is returned. This 
 method has frequently been employed in determining the dif- 
 ference of longitude between the capitals of various coun- 
 tries, a number of very accurate timepieces (chronometers) 
 being carefully carried from one place to the other. 
 
 Longitude is determined at sea by a similar method, A 
 chronometer set to Greenwich (or some other) local time is 
 carried on the vessel. Local noon is determined by noting 
 the time when the sun rises highest above the horizon in its 
 daily circuit. After certain corrections are made the differ- 
 ence between Greenwich and local time gives the longitude. 
 
 A very simple method may be employed for finding the 
 difference of longitude between two places that are connected 
 
APPENDIXES. 393 
 
 by telegraph. Let the local time be ascertained, as described 
 above, at each place. At some day and hour agreed upon, let 
 the observers at each place go to their respective telegraph 
 offices and exchange time signals ; that is, at certain even five 
 seconds, as indicated by the watch, let the observer at one 
 place send a telegraphic signal to the other observer, who 
 records the time of its arrival. Local times may be thus 
 comj^ared with great accuracy. This method has now been 
 employed not only between neighboring cities, but across the 
 whole breadth of the United States, and by cable across the 
 Atlantic. It may be easily repeated between schools a hun- 
 dred or more miles apart, at a very moderate cost. 
 
 APPENDIX D. 
 
 Globes, Maps, and Models (p. 17). — In the study of geog- 
 raphy it is necessary to represent the earth, or parts of 
 it, in a form convenient for study. This is done on globes, 
 maps, and models. Globes are excellent in showing the gen- 
 eral distribution of land and water over the whole earth, 
 with true outlines and correct relative positions ; but they 
 cannot be made large enough to exhibit the small features of 
 land forms.'- 
 
 Maps necessarily have some distortion, for it is impossible, 
 without crowding or stretching certain parts, to represent the 
 convex surface of the earth, curved east and west as well as 
 north and south, on a plane surface. But maps of parts of the 
 earth have the advantage of being easily constructed of a size 
 large enough to exhibit even the smaller features of the lands. 
 
 Models are less cominonly used than globes or maps, but if 
 well constructed they are of great value, as they may repre- 
 sent the form of the lands over moderate areas with great 
 
 1 An inexpensive &ix-incli globe is made by A. Donnelly, O^f nxl, N. Y. 
 
394 
 
 PHYSICAL GEOGRAPHY. 
 
 fidelity. Views of the Harvard Geographical Models, de- 
 signed by the author, are given in Figs. 71, 72, and 122.^ 
 Models are sometimes made with the sea surface convex, like 
 that of the earth ; they then correspond to parts of large 
 globes. A model of the United States, on a true-curved 
 surface, is reproduced in Plate A, to illustrate the physical 
 features of the country.^ It is important that the height of 
 ridges and mountains on models should not be much magni- 
 fied in proportion to their horizontal measures. 
 
 Projection of Maps. In the construction of maps, the 
 
 meridians and parallels are first 
 drawn as guide lines by a method 
 called projection (see below) ; then 
 the outlines of land and water, 
 the position of boundaries, cities, 
 etc., are drawn in according to 
 their determined latitude and lon- 
 gitude, or according to their dis- 
 tance and direction from known 
 points. 
 
 In order to present half of the 
 earth's surface, the StereograpMc 
 projection is commonly employed 
 as follows : 
 
 Let the map plane touch a 
 globe at the equator, as in Fig. 
 256. From the opposite point on 
 the equator imagine straight lines drawn through various 
 points on the meridians and parallels ; prolong or project 
 these lines till they intersect the map plane. The projected 
 position of the guide lines is thus determined. The central 
 
 1 These models are published by Ginn & Company. 
 
 2 This model is made by E. E. Howell, 612 17th Street, N. W., Wash- 
 ington, D. C. 
 
 Fig. 256.— The Stereographic Projection. 
 
APPENDIXES. 
 
 395 
 
 part of sucli a map is in true proportion ; at the margin 
 distances are doubled. In actual practice projection does 
 not require the aid of a globe ; the position of tlie projected 
 guide lines is constructed by an ingenious use of geometry on 
 the map plane itself. 
 
 When it is desired to represent nearly all the earth on 
 a single map, the Mercator j>rojectio7i is commonly used as 
 follows : 
 
 Imagine a cylinder touching a globe around the equator, as 
 
 Fig. 257. — The Mercator Projection. 
 
 Fig. 258. —The Conical Projection. 
 
 in Fig. 257. From the center of the globe project the guide 
 lines upon the cylind-er. Cut the cylinder down one side, and 
 open it flat. The equator and parallels are then horizontal 
 lines ; the meridians are vertical lines. There is no distortion 
 around the equator, but there is an increasing exaggeration 
 towards the poles ; hence the polar regions are not represented 
 on maps of this kind. 
 
 When a small part of the earth's surface, such as Germany 
 or Mexico, is to be mapped, the Conical jjrojection (or some 
 modification of it) involves relatively little distortion. Imag- 
 ine a cone touching the earth on a latitude circle that passes 
 through the middle of the country to be mapped. Project 
 
396 
 
 PHYSICAL GEOGRAPHY. 
 
 lines from the center of the globe to the enclosing cone. 
 When the cone is split and unwrapped, the meridians are 
 divergent straight lines, and the parallels are concentric 
 circles. 
 
 Many other methods of projection are also employed. 
 
 Fig. 259. — Representation of Relief by Hachures. 
 
 Relief. The unevenness of a land surface is technically 
 known as relief. Models have the advantage of showing 
 actual relief. On maps relief is shown in various ways. 
 Hachures are lines drawn in the direction of the surface 
 slope, — longer and finer for gentler slopes, shorter and darker 
 for steeper slopes. Hachures are used on the maps of the 
 U. S. Coast and Geodetic Survey (generally known as the 
 
APPENDIXES. 397 
 
 '^ Coast Survey"). Contour lines, or contours, represent level 
 lines along the side of a slope, as if marking the shore lines 
 of the ocean at successive stages of its rise on the land. 
 They are placed so as to be separated by definite vertical 
 intervals, such as 50 or 100 feet ; consequently they stand far 
 apart on gentle slopes and close together on steep slopes. 
 Contours are used on the maps of the U. S. Geological 
 Survey, and should become familiar by frequent use. Exam- 
 ples of contour maps are given in Figs. 134, 137, and 153. 
 
 Lists and prices of tlie maps published by these surveys may 
 be obtained without charge on addressing the Superintendent 
 of the U. S. Coast Survey, and the Director of the U. S. 
 Geological Survey, Washington, D. C. Many of the maps 
 are of great value as geographical illustrations. A general 
 account of many of them is given in "Governmental Maps 
 for use in Schools," Holt & Co., New York. The maps 
 published by the Geological Survey can be had for two cents 
 apiece when bought by the hundred. 
 
 Relief is sometimes indicated by shading, so that one side 
 of a hill or mountain appears lighter than the other side. 
 Darker tints are sometimes used to indicate greater heights. 
 Good examples of both these methods have been prepared 
 for the state of New Jersey; they may be bought at moderate 
 price from the State Geological Survey, Trenton, N. J. 
 
 Scale of Maps. The ratio of a distance on a globe or map 
 to the same distance on the earth is expressed by the scale. 
 A globe 8 inches in diameter is on a scale of about 1 inch to 
 1000 miles. Many maps are on a scale of about 1 inch to 50 
 or 100 miles. The scale may be expressed by a fraction — a 
 scale of 1 inch to 2 miles being x2^V2o ^^ nature. The sim- 
 pler fraction, X25V00' ^^ adopted for many of our national 
 maps. A scale of ^2^00 corresponds closely to that of an 
 inch to a mile. 
 
398 PHYSICAL GEOGRAPHY. 
 
 APPENDIX E. 
 
 Terrestrial Magnetism. — The earth acts as if it were a 
 great magnet ; this being one of its most remarkable and use- 
 ful properties. In response to the earth's magnetism, a mag- 
 netic needle, delicately suspended on a vertical pivot, will 
 take a definite direction, about north and south in many 
 parts of the world. The magnetic needle or compass thus 
 ■ serves as a guide on pathless lands and seas. 
 
 As the needle seldom points true north, its departure from 
 the meridian must be determined. This angle is called the 
 Tnagnetic variation or declination. It may be found by com- 
 paring the direction of the needle with the shadow of a 
 vertical rod at midday. The variation slowly changes from 
 year to year. 
 
 The compass was invented by the Chinese. It was intro- 
 duced into Europe about 800 years ago. When Columbus 
 made his first voyage, the magnetic variation in Europe was 
 west of true north. He found that it decreased as he sailed 
 westward, and soon after passing the longitude of the Azores 
 he discovered a point where the variation was zero. Farther 
 west the variation was found to be east of true north, increas- 
 ing as he sailed west from the point of no variation. 
 
 A few years later, when Spain and Portugal were in dis- 
 pute about lands then newly discovered, it was decided by 
 the Pope that Portugal should have the lands to the east of 
 the meridian that ran through the point of no variation, and 
 Spain all the lands to the west of it. The eastern point of 
 South America lay east of the dividing line, and hence fell to 
 the share of Portugal, which thus gained possession of Brazil. 
 For that reason Portuguese is spoken there to this day, while 
 Spanish is the language of the other American republics from 
 Mexico southward. 
 
APPENDIXES. 
 
 399 
 
 Since the time of Columbus it lias been found that the line 
 of no variation (connecting all points where the needle points 
 due north) is not a meridian, and that it shifts its position. 
 About 1500 it lay on the mid- Atlantic. About 1600 it ran 
 from Finland to Egypt. In 1700 it again traversed the 
 mid-Atlantic. Now it runs through the United States from 
 lower Michigan to South Carolina. At all places in the 
 United States east 
 of the line, the com- 
 pass needle points 
 to the west of the 
 true meridian ; at 
 all places west of 
 the line, to the 
 east. 
 
 If lines of mag- 
 netic north (often 
 called " magnetic 
 meridians ") are 
 drawn through 
 many places and 
 prolonged, always 
 
 following the guide of the needle, tLey will converge and 
 meet at a point called the north magnetic pole, in the north- 
 ern part of the Canadian province of Keewatin (northwest 
 of Hudson Bay, latitude 70°). If the magnetic meridians are 
 prolonged southward, they converge towards a south magnetic 
 pole, far south of Australia. On the (true) polar side of the 
 magnetic poles the variation of the compass may be 180° ; its 
 north end would there point south. 
 
 When the values of magnetic variation are found for many 
 places and entered on a map, lines may be drawn through 
 the places where the values are alike. These are called 
 "lines of equal variation," as in Fig. 260. 
 
 Fig. 260. — Lines of Equal Magnetic Variation. 
 
400 PHYSICAL GEOGRAPHY. 
 
 APPENDIX F. 
 
 The Annual Movement of the Earth around the Sun and 
 its Consequences (pp. 27 and 35) may be best explained after 
 pupils have been led to notice the stars seen in the east 
 shortly after sunset. Observations made once a week or 
 fortnight suffice for this purpose. If they are patiently con- 
 tinued, it may easily be shown that a line from the sun 
 through the earth points successively to different groups of 
 stars ; but that at the end of a year it points again to the 
 group with which the observations began. Recognizing that 
 the stars are very far away, much farther than the earth is 
 from the sun, the movement of the earth around the sun once 
 in about 365 days can be thus reasonably proved. An under- 
 standing of the earth's revolution thus gained is of much 
 greater value than the memory of a text-book paragraph. 
 
 The following construction will be found to give a better 
 explanation of the cause of the seasons, as dependent on 
 the inclination of the earth's axis, than can be gained from a 
 ready-made diagram. 
 
 Through the middle of a sheet of paper that measures 10 
 or 20 inches on a side, draw a straight line parallel to one 
 side. Let this middle line represent 200 arbitrary units of 
 length. Mark two points, one on each side of the middle 
 of the line, so that they shall be 3 units apart. Drive two 
 pins through the paper at these points so that they shall 
 stand firm. Place a loop of thread, whose perimeter meas- 
 ures 189 units, over the pins ; stretch the loop tight with a 
 pencil ; and thus guided draw a curve around the pins. It 
 will look like a circle, but it is an ellipse, and represents the 
 true form of the earth's orbit. Take out the pins, and around 
 one pin hole draw a circle a little less than 1 unit in diameter ; 
 this represents the sun, the units being niillions of miles. 
 
APPENDIXES. 401 
 
 The distances from the sun along the middle line of the paper 
 to the orbit will be 91|- and 94|- million miles. The earth 
 occupies the first of these points (called ])^^'^helion) on Janu- 
 ary 1, and is then nearer the sun than at aiiy other time of 
 the year. The opposite point {aplielioii) is occupied on July 1. 
 On this scale the earth would be a minute dot, hardly visible. 
 It must be magnified to a globe (wooden ball) about one inch 
 in diameter, and set up on a small flat support with a pin or 
 wire for its axis. The ISTorth star being supposed to lie on 
 the upper side of the paper, the earth must move around its 
 orbit so that when seen from the sun it passes from right to 
 left. Move the earth back from its position on January 1 by 
 ^ of a quadrant ; this is the position for December 21. In 
 this position, tilt the upper end of the axis 23-^° away from 
 the vertical and away from the sun. The earth is then set in 
 its proper attitude. Now move it slowly around the orbit, 
 always keeping the axis parallel to its oblique position on 
 December 21. It will then clearly appear that the sun's rays 
 will shine unequally on the northern and southern hemispheres 
 in different parts of the orbit. The limits of the zones are 
 easily defined. By turning the earth on its axis, it may be 
 seen that a point, as in latitude 40° N., will have oblique 
 (weak) sunshine and short days with long nights in the 
 winter months, and steeper (stronger) sunshine, with longer 
 days and shorter nights in the summer months. The times of 
 shortest days and shortest nights are the solstices, December 
 21 and June 21, respectively. At two points on the orbit 
 (found by drawing a line through the sun at right angles to 
 the solstitial line), the days and nights are equal ; these 
 points are called the equinoxes, and are passed on March 20 
 and September 22. The sun will be vertical at noon at 
 some time during the year at every point within 23^° north 
 or south of the equator — the zone thus defined being called 
 the torrid zone. On December 21 the sun will not be seen 
 
402 PHYSICAL GEOGRAPHY. 
 
 from any point within 23-|-° of the north pole ; on June 
 21 it will not be seen from any point within a similar space 
 aronnd the south pole — the spaces thus defined being called 
 the north and south frigid zones. The north and south tem- 
 perate zones lie between the torrid and frigid zones ; they 
 never have a vertical sun, or a day in which sunlight does 
 not reach every point within their limits. Frequent prac- 
 tice with school-made apparatus will make the problems of 
 the seasons and the zones well understood. 
 
 APPENDIX G. 
 
 The Circulation of the Atmosphere (p. 29). — The inter- 
 esting problem of the atmospheric circulation as modified by 
 the earth's rotation cannot be profitably taken up in a book 
 of this grade. Attention should be given chiefly to the more 
 important members of the circulation seen in the lower cur- 
 rents or winds, as described in the text. It may be briefly 
 stated that, on account of the earth's rotation, there is a force 
 that tends to deflect all horizontal motions (whatever their 
 direction) to the right in the northern hemisphere, and to the 
 left in the southern. This force is zero at the equator, and 
 strongest at the poles. The temperature being unlike at the 
 equator and poles, gravity tends to produce interchanging 
 currents along the meridians. The earth's rotation deflects 
 these motions to the right or left, according to the hemi- 
 sphere, and the resultant motions greatly affect the dis- 
 tribution of pressure that would result from differences of 
 temperature alone. Instead of finding high atmospheric pres- 
 sure in the cold polar regions, the pressure there is lower 
 than at the equator ; and a belt of high pressure is found 
 about latitude 28° or 30° N. and S., this belt defining the 
 " meteoi-ological tropics." See the author's ''Elementary 
 Meteorology," 1894. 
 
APPENDIXES. 403 
 
 APPENDIX H. 
 
 Clouds and Rainfall (p. 31 and 45). — A greater amount of 
 water vapor can be contained in warm than in cold air. When 
 as much vapor is present as can be formed at a given tempera- 
 ture, the air is said to be saturated. When air is not saturated, 
 it may be made so by cooling it until the temperature falls to 
 that degree at which the amount of vapor present is as much 
 as can be contained. Any further cooling will make the air 
 cloudy, and if continued far enough will cause rain or snow. 
 
 The chief processes by which large masses of air are cooled 
 sufficiently to become cloudy and yield rainfall are : (1) mix- 
 ture with colder air masses ; (2) movement into a region 
 where sunshine and radiation from the earth cannot maintain 
 the preexisting temperature ; and (3) an ascending move- 
 ment (generally very oblique), whereby the air rises and the 
 pressure of the overlying atmosphere upon it is reduced, so 
 that it expands and cools. The first of these processes occurs 
 in the whirling winds of cyclonic storms, but it is probably 
 of much less importance than the others. The second pro- 
 cess takes place when winds move towards the pole, and espe- 
 cially when this movement carries them from warm seas to 
 cold lands, as in passing during the winter season from the 
 Gulf of Mexico or the Atlantic towards the Great Lakes in 
 front of a cyclonic center. The third is of great importance 
 when winds encounter mountain ranges over which they 
 must rise ; and again in cyclonic areas, where the whirling 
 winds slowly ascend to great heights. 
 
 It should be noted that the cooling of ascending currents 
 is hardly influenced at all by the cold of lofty mountain tops, 
 or by the low temperature of the upper atmosphere that they 
 enter. The cooling is the immediate result of the expansion 
 of the ascending air. Cooling of this kind may be felt in a 
 
404 PHYSICAL GEOGRAPHY. 
 
 small way when the air is allowed to escape from its com- 
 pressed condition in a bicycle tire by opening the valve. 
 
 By reversing the above processes the conditions of clear 
 and dry weather are indicated. The clouds of cool winds 
 will be dissolved when the winds mix with warmer currents. 
 Movement towards the equator, where higher temperatures 
 are produced, will increase the capacity of air currents for 
 vapor. They will then dry the surface over which they blow. 
 It is in this way that the trade winds produce deserts. When 
 air descends from aloft, it is compressed by the weight of the 
 air that rolls in upon it above. It is thus warmed ; and if it 
 contained any clouds at first, they will be speedily dissolved. 
 Hence winds that become cloudy and give forth rain on one 
 side of a mountain range will be clear and dry when they 
 descend on the opposite slope. In the same way the air of 
 anticyclonic areas is clear and dry, because it settles down 
 from great heights to supply the outflowing winds at the 
 base. 
 
 The many forms assumed by clouds afford better material 
 for observation than for definition. Students should be led 
 to describe and to classify the ordinary cloud forms, and to 
 note their prevalent direction of movement and their altitude 
 relative to one another, rather than to learn names and 
 descriptions from a book. The chief classes of cloud form 
 are : the curmdus, or heaped cloud, of massive structure and 
 moderate altitude, characteristic of daytime and fair weather ; 
 the cirrus, or curled cloud, of delicate, fibrous structure and 
 great altitude ; nimbus, or rainfall cloud, heavily covering the 
 sky, and yielding rain or snow. Cumulus clouds are formed 
 in local ascending currents of air ; they sometimes grow into 
 the nimbus of thunder storms. Fibrous cirrus clouds may 
 often be traced westward to a source in thin sheet-clouds, 
 called cirro-stratus, and these in turn to a source in the heavy 
 nimbus of a cyclonic area. 
 
APPENDIXES. 405 
 
 APPENDIX I. 
 
 Weather Observations and Weather Maps (p. 49). — A 
 thermometer, barometer, wind vane, and rain gauge suffice 
 for elementary observations of the weather. The more accu- 
 rate the instruments are, the better, but useful results can be 
 obtained with instruments of very moderate cost. Observa- 
 tions should be conducted so as not only to determine the gen- 
 eral change of tlie seasons, but also to exhibit the relation of 
 local weather to the general phenomena exhibited on the 
 United States weather maps. For this purpose it is desirable 
 to give attention to one weather element at a time ; for exam- 
 ple, first wind, then clouds and rainfall, next temperature, 
 finally pressure. Each of these elements should be noted 
 during the passage of one or two cyclonic and anticyclonic 
 areas represented on the weather maps. After the several 
 weather elements have been studied singly, they may be 
 observed in their natural combination ; thus an understand- 
 ing may be gained of the relation between local and general 
 atmospheric conditions. Local and distant phenomena may be 
 compared ; thus a period of settled fair weather illustrates the 
 weather of the trade wind belt ; a period of changing weather, 
 the weather of the north and south temperature zones. 
 
 Accompanying these observations, exercises on the con- 
 struction of weather maps may be given. Here, as in local 
 observation, it is well to give attention to one element at a 
 time, as in Pigs. 12 and 15. The correlation of the various 
 weather elements in cyclonic and anticyclonic areas, the east- 
 ward progress of these areas, and the resulting weather changes, 
 should be discovered by the pupils themselves, as far as pos- 
 sible, from the study of a selected series of typical weather 
 maps. There are few subjects better adapted to the inculca- 
 tion of scientific methods than the study of weather changes. 
 
406 
 
 PHYSICAL GEOGRAPHY. 
 
 Daily weather maps can be obtained from the nearest 
 publishing station of the U. S. Weather Bureau at a nomi- 
 nal cost. If publicly displayed where they may be of gen- 
 eral service, they may usually be obtained free of charge. 
 A collection of such maps is of great service in teaching ; 
 the more striking examples of cyclonic and anticyclonic 
 areas should be noted as types. Information regarding the 
 distribution of the maps may be had on addressing the Chief 
 of the Weather Bureau, Washington, D. C. 
 
 APPENDIX J. 
 
 The Moon and the Tides (p. 86). — Let C (Fig. 261) be the 
 common center of gravity of the earth and the moon. Both 
 bodies revolve around this center once a month (27|: days), 
 the plane of the page being the plane of their revolution, and 
 
 Fig. 261.— The Tidal Problem. 
 
 AFBD being the earth's equator. The attraction exerted by 
 the moon on a part of the earth at E is just equa,l to the 
 resistance (centrifugal force) that this part offers to turning 
 from a straight line, EJ, into its curved path, EG. At A the 
 attraction of the moon is a little greater, and at-^ a little 
 less, than at^. The resistances to curved motion (centrifugal 
 force) are everywhere alike. Hence at A and B there must 
 be small unbalanced forces, t^ and t^^, directed outward from 
 
APPENDIXES. 407 
 
 the earth's center, and lying on the line ^M. As the earth 
 turns on its axis, any point on the equator AFBD must be 
 acted on by the forces t^ and t^^ every 12 hours 26 minxites. 
 The forces are very weak, and the waves that they produce in 
 the oceans must be very low ; but they are perceptible when 
 increased by running on shore. 
 
 The only point that may be obscure in this statement is 
 the constant value of the resistance to curved motion at all 
 parts of the earth. But remembering that the diurnal rota- 
 tion of the earth may be overlooked while the tidal forces are 
 discussed, it should be seen that the monthly movement of 
 the earth around C must be accomplished witJiout angular 
 turning, a given side of the earth always facing in a fixed 
 direction. If this be tried experimentally with a disk of 
 paper, or with a small globe, it will be seen that all parts 
 of the earth thus moved will describe circles of the same size 
 as that which carries E round C ; and that at any moment 
 all parts are moving in the same direction ivith the same 
 velocity. Hence all parts must have the same resistance to 
 curved motion. If this important point is once grasped, 
 there should be no further difficulty in the demonstration of 
 the unbalanced forces at A and B. 
 
 The value of the tidal forces t^ and t^^ may be roughly 
 calculated in terms of gravity, as follows : 
 
 As the moon's mass is -^l of the earth's mass, and as the 
 distance from the moon to the earth is sixty times the 
 earth's radius, it follows that lunar attraction at E is 
 
 QA ' >rA\2 ' °^ 2¥Fooo of terrestrial gravity. Lunar attractions 
 
 at A and B are (f §)^ and (f f)^ of lunar attraction at E. The 
 excess of lunar attraction at A and the deficiency at B with 
 respect to the value at E will measure the value of the small 
 unbalanced forces to which the tides are due. These will be 
 found to be about 0.0000001 of terrestrial gravity. 
 
408 PHYSICAL GEOGRAPHY. 
 
 The Sun also causes tides in the oceans, but, in spite of 
 the great size of the sun, its distance is so much greater than 
 that of the moon that the solar tides have only about one- 
 third of the strength of the lunar tides. Hence the lunar 
 tides are not overcome, but only modified by the solar tides. 
 At time of new and full moon, when lunar and solar tides fall 
 together, the tidal range is increased, low tide being lower as 
 well as high tide being higher than usual. Sprmgtide is the 
 name given to this condition of strong range. At the first 
 and third quarter of the moon, the solar forces attempt to 
 make low tide where the lunar forces make high tide, and 
 vice versa ; hence at such times the tidal range is decreased, 
 low tide being not so low and high tide being not so high as 
 usual. Neaptide is the name given to this condition of weak 
 range. It is often the case that the range of springtides is 
 twice that of neaptides. 
 
 APPENDIX K. 
 
 Recent observations indicate that in the polar oceans, 
 where evaporation is small, the cold surface water is some- 
 what reduced in density by the supply of fresh water from 
 rain, snow, and rivers. The polar surface water is therefore 
 not quite so dense as the somewhat less cold but Salter surface 
 water in latitude 60° or thereabouts. Hence the simple plan 
 of the convectional movement of the underwaters between 
 the poles and the equator should be modified by the addition 
 of a subordinate movement that carries dense cold salt water 
 from latitude 60° or thereabouts poleward underneath the still 
 colder but less salt and less dense water of the polar oceans. 
 It is in this way that the slight increase of temperature in 
 the deep polar waters, discovered in the Antarctic by the 
 Challenger expedition, and in the Arctic by Nansen, can be 
 accounted for. 
 
APPENDIXES. 409 
 
 APPENDIX L. 
 
 References for Supplementary Reading. 
 
 The titles in the following list have been selected with especial 
 reference to their accessibility in public libraries. Frequent mention 
 is made of the publications of the U. S. Geological Survey because 
 of their great value to the geographer as well as of theu' wide distri- 
 bution. 
 
 General References. 
 
 Gannett, The United States, Stanford's Compendium of Geography, 
 Edward Stanford, 1898. 
 
 The Annual Reports, Bulletins, Monographs, and Geological Folios 
 of the U. S. Geological Survey. Many of the more geographical 
 essays are referred to below. (Abbrev., G. S, Ann. Rep., etc.) 
 
 The following geographical periodicals contain a great amount of 
 material serviceable in teaching : 
 
 National Geographic Magazine, Washington, D. C. (Abbrev., N. G. M.). 
 
 Bulletin of the American Geographical Society, New York. 
 
 Journal of School Geography, Lancaster, Pa. (J. S. G.). 
 
 Geographical Journal, London. 
 
 Scottish Geographical Magazine, Edinburgh (S. G. M.). 
 
 Platt, The Better Books in School Geography, J. S. G., May, '98. 
 
 (All the books mentioned in the above article would be found serviceable 
 in school libraries.) 
 
 Davis, The Equipment of a Geographical Laboratory, J. S. G., 
 
 May, '98. 
 Cornish, Laboratory Work in Elementary Physiography, J. S. G., 
 
 June, Sept., '97. 
 National Geographic Monographs, American Book Co., 1895. 
 Preliminary Report of Committee on Physical Geography of N. E. 
 
 A.; J. S. G., Sept., '98. 
 Shaler, History of the Earth. D. Appleton & Co., 1898. 
 
410 PHYSICAL GEOGRAPHY. 
 
 Chapter TI. — General References. 
 
 Young, Astronomy. Ginn & Company, 1888. 
 Todd, Astronomy. American Book Co., 1897. 
 
 Chapter III. — General References. 
 
 Waldo, Elementary Meteorology. American Book Co., 1896. 
 Davis, Elementary Meteorology. Ginn & Company, 1894. 
 Jameson, Elementary Meteorology, J. S. G., Jan., Feb., March, 
 
 April, '98. 
 Greely, American Weather. Dodd, Mead & Co., 1888. 
 Harrington, Rainfall of the United States, U. S. Weather Bureau, 
 
 Bulletin C, 1894. 
 Greely, Rainfall Types of the United States, N. G. M., v, 45. 
 
 Special References. 
 
 PAGE 
 
 53. Davis, The Temperate Zones, J. S. G., May, '97. 
 
 53. Ward, Climatic Control of Occupation in Chile, J. S. G., 
 
 Dec, '97. 
 55. Merriam, Geogr. Distribution of Terrestrial Animals and 
 
 Plants, N.G.M., vi, 229. 
 
 Chapter IV. — General References. 
 
 Thomson, The Depths of the Sea. Macmillan & Co., 1874. 
 Thomson, The Voyage of the Challenger : The Atlantic. Macmillan 
 
 & Co., 1877. 
 Sigsbee, Deep Sea Sounding and Dredging, Washington, 1880. 
 Agassiz, Three Cruises of the Blake, Cambridge, 1888. 
 Monthly Pilot Charts of the North Atlantic and the North Pacific 
 
 Oceans, U. S. Hydrographic Office, Washington. 
 
 Special References. 
 
 PAGE 
 
 72, 83. Davis, Waves and Tides, J. S. G., April, '98. 
 
 76. SciDMORE, Earthquake Wave, Japan, N. G. M., vii, 285. 
 
APPENDIXES. 411 
 
 PAGE 
 
 77. Davis, Winds and Ocean Currents, S. G. M., Oct., '97, and 
 
 J. S. G., Jan., '98. 
 81. PiLLSBURV, The Gulf Sti-eam, Ann. Rep. U. S. Coast Survey, 
 
 1890. 
 84. Tide Tables, published annually by U. S. Coast Survey. 
 
 Chapter V. — General References. 
 
 Shaler, Aspects of the Earth. Charles Scribner's Sons, 1889. 
 Text-books on Elementary Geology by Dana, Geikie, Leconte, Scott, 
 and Tarr. 
 
 Special References. 
 
 PAGE 
 
 107. Heilprin, Distribution of Animals. D. Appleton & Co., 1886. 
 107. Beddard, Zoogeography. University Press, Cambridge, 
 
 189.5. 
 107. MacMillan, Geogr. Distribution of Plants, J. S. G., 
 
 April, '97. 
 
 109. Wallace, Island Life. Macmillan & Co., 1891. 
 
 110. Wallace, Travels in the Malay Archipelago. Macmillan 
 
 & Co., 9th ed. 
 
 Chapter VI. — Special References. 
 
 117, 119. Davis, Description of the Harvard Geographical Models, 
 published by the Boston Society of Natui'al History, 
 Berkeley Street, Boston. 
 
 123. Glenx, South Carolina, J. S. G., Jan., Feb., '98. 
 
 125. Cobb, North Carolina, J. S. G., Nov., Dec, '97. 
 
 126. Shaler, The Dismal Swamp, G. S. 10th Ann. Rep., 313. 
 
 126. Chamberlin, Artesian AVells, G. S. 5th Ann. Rep., 125. 
 
 127. McGee (Fall line), G. S. 12th Ann. Rep., 360. 
 130. McGee, Chesapeake Bay, G. S. 7th Ann. Rep., 548. 
 139. Ramsay, Physical Geology and Geography of Great Britain, 
 
 London, 6th ed., 1894, 333. Edward Stanford, 1894. 
 144. Powell, Exploration of the Colorado river of the west, 
 Washington, 1875. See pp. 98-102, 130, 131. 
 
412 PHYSICAL GEOGBAPHY. 
 
 PAGE 
 
 144, 155. Button, Colorado Canyon, G. S. 2d Ann. Rep., 49. 
 
 144, 155. Button, Colorado Canyon, G. S. Monogr. II. 
 
 147. Campbell and Mendenhall (Plateau of West Virginia), 
 
 G. S. 17th Ann. Eep., 480. 
 149. EoosEVELT, Winning of the West, vol. i, 101; vol. iii, 13. 
 
 G. P. Putnam's Sons, 1894. 
 149. Semple, Influence of the Appalachian Barrier upon Colonial 
 
 History, J. S. G., Feb., '97. 
 151. Hodge, The Enchanted Mesa, N. G. M., viii, 273. 
 154. Marbut, Missouri, J. S. G., April, May, '97. 
 
 Chapter VII. — Special References. 
 
 161. Russell, Southern Oregon, G. S. 4th Ann. Rep., 435. 
 
 165. Russell (Mountains of Nevada), G. S. Monogr. XI, 38. 
 
 169. Newton (edited by Gilbert), Geology of the Black Hills, 
 
 Washington, 1880. 
 
 172. Fay, Canadian Alps, J. S. G., June, '97. 
 
 172. WiLLCOx, Canadian Rockies, J. S. G., Dec, '97. 
 
 172. Lubbock, Scenery of Switzerland. Macmillan & Co., 1896. 
 
 183. Milne, Earthquakes. D. Appleton & Co., 1883. 
 
 186. Beddard, Zoogeography. University Press, Cambridge, 
 
 1895. 
 
 187. Willis, Round about Asheville, N. C, N. G. M., i, 291. 
 
 188. McGee, Geogr. History of the Piedmont Plateau, N. G. M., 
 
 vii, 261. 
 
 188. Keith (Piedmont Plateau), G. S. 14th- Ann. Rep., 366. 
 
 190. Willis, Northern Appalachians, Natl. Geogr. Monogr. 
 
 190. Hayes, Southern Appalachians, Natl. Geogr. Monogr. 
 
 190. Davis, Rivers and Valleys of Pennsylvania, N. G. M., i, 183. 
 
 192. Davis, Southern New England, Natl. Geogr. Monogr. 
 
 192. Davis, Geographical Illustrations (Southern New England), 
 published by Harvard University, Cambridge, Mass. 
 
 194. A. Geikie, Scenery of Scotland, 2d ed. (chapters on High- 
 lands). Macmillan & Co., 1887. 
 
APPENDIXES. 413 
 
 PAGE 
 
 194. Herbertson, Geography of Scotland, J. S. G., May, '98. 
 198. Irving (Baraboo ridge), G. S. 7th Ann. Rep., 399. 
 
 Chapter VITI. — General References. 
 
 Russell, Volcanoes of North America. Macmillan, 1897. 
 Dana, Characteristics of Volcanoes. Dodd, Mead & Co., 1890. 
 JuDD, Volcanoes. D. Appleton & Co., 1881. 
 Dodge, Volcanoes, J. S. G., June, '97. 
 
 Special References. 
 
 PAGE 
 
 202, 203. Lyell, Principles of Geology (Monte Nuovo, vol. i, 
 
 p. 607 ; JoruUo, vol. i, p. 585). D. Appleton & Co., 
 1872. 
 
 203. DiLLER, A Late Volcanic Eruption in Northern California, 
 
 G. S. Bull. 79. 
 
 207. Phillips, Vesuvius. Macmillan & Co., 1869. 
 
 207. Milne, Earthquakes. D. Appleton & Co., 1883. 
 
 210. DuTTON (Lava Flows), G. S. Monogr. II. 
 
 213. DuTTON, Hawaiian Volcanoes, G. S. 4th Ann. Rep., 81. 
 
 214. Diller, Mt. Shasta, Natl. Geogr. Monogr. 
 216. Diller, Crater Lake, N. G. M., viii, 33. 
 
 216. Diller, Crater Lake, J. S. G., Nov., '97. 
 
 217. DuTTON, Volcanic Necks of Zuni Plateaus, G. S. 6th Ann. 
 
 Rep., 164. 
 217. Gilbert, Geology of the Henry Mountains, Washington, 
 
 1877. 
 217. Cross, Laccolites, G. S. 14th Ann. Rep., 165. 
 
 Chapter IX. — General References. 
 
 Gilbert, Geology of the Henry Mountains, Washington, 1877. 
 
 Chapter on Land Sculpture, p. 99. 
 Russell, Lakes of North America. Ginn & Company, 1894. 
 Brigham, Lakes, a Study for Teachers, J. S. G., March, '97. 
 Russell, Rivers of North America. G. P. Putnam's Sons, 1898. 
 
414 PHYSICAL GEOGRAPHY. 
 
 Special References. 
 
 PAGE 
 
 225. HovEY, Mammoth Cave, J. S. G., May, '97. 
 
 226. Walcott, Natural Bridge of Virginia, N. G. M., v, 59. 
 228. Weed (Hot Springs), G. S. 9th Ann. Rep., 613. 
 
 232. Bell, Tlie Labrador Peninsula, S. G. M., xi, 335. 
 
 232, Gilbert, Niagara, Natl. Geogr. Monogr. 
 
 246, Gannett, Mississippi Flood of April, 1897, S. 6. M., Au- 
 gust, '97. 
 
 249. Davis, Seine, Meuse, and Moselle, N. G. M., vii, 189, 228. 
 
 257. Lubbock, Scenery of Switzerland, 133, 312. Macmillan 
 & Co., 1896. 
 
 259. DeKalb, Valley of the Amazon, J. S. G., Sept., '97. 
 
 Chapter X. — Special References. 
 
 265. Shaler, Origin and Nature of Soils, G.S. 12th Ann. Rep., 219. 
 276. Lubbock, Beauties of Nature. Macmillan & Co., 1892, 264. 
 285. Powell, Exploration of the Colorado River of the "West, 
 
 Washington, 1877. (Green River basin.) 
 289. PuMPELLY, Researches in China, Smithsonian Contributions, 
 
 No. 202, 1866, p. 48. 
 
 Chapter XI. — General References. 
 
 Russell, Glaciers of North America. Ginn & Company, 1897. 
 Shaler and Davis, Glaciers. James R. Osgood & Co., 1881. 
 Tyndall, Forms of Water. D. Appleton & Co., 1872. 
 J. Geikie, Great Ice Age, 3d ed., D. Appleton & Co., 1895. 
 Wright, Ice Age in North America. D. Appleton & Co., 1890, 
 
 Special References. 
 
 PAGE 
 
 303. Gilbert, Geology of the Henry Mountains, Washington, 
 
 1877, Chapter on Land Sculptui-e. 
 306. Russell, Past and Present Lakes of Nevada, Natl, Geogr, 
 
 Monogr, 
 
APPENDIXES. 415 
 
 PAGE 
 
 309. King, Geol. Survey of the dOth Parallel, Washington, vol. i, 
 1878, 460, 484; vol. ii, 1877, 470. 
 
 317. PuMPELLY, Researches in China, Smithsonian Contribu- 
 
 tions, No. 202. 
 
 318. Gilbert, Lake Bonneville, G. S. 2d Ann. Eep., 169. 
 
 318. Gilbert, Lake Bonneville, G. S. Monogr. T. 
 
 319. Russell, Lake Lahontan, G. S. 3d Ann. Rep., 195. 
 322. McGee, Seriland, N. G.M., vii, 125. 
 
 324. Jennings-Bramley, Journey to Siwa, Geogr. Journ. 
 
 (London), Dec, '97. 
 326. Nansen, First Crossing of Greenland, 1890. Longmans, 
 
 Green & Co., 1890. 
 32&. Peary, Northward over the Great Ice. Frederick A. Stokes 
 
 Co., 1898. 
 330. Russell, Glaciers of Alaska, G. S. 13th Ann. Rep., 7. 
 330. Russell, Mt. St. Elias, Alaska, N. G.M., iii, 53. 
 330. Reid, Muir Glacier, Alaska, N. G. M., iv, 19. 
 
 330. Russell, Existing Glaciers of the U. S., G. S. 5th Ann. 
 
 Rep., 303. 
 
 331. Russell, Mono Lake Region, G. S. 8th Ann. Rep., pt. I, 
 
 321. 
 
 332. A. Geikie, Scenery of Scotland, 2d ed., chapters on Glacial 
 
 Action. Macmillan & Co., 1887. 
 
 333. Chamberlin, Rock Scorings, G. S. 7th Ann. Rep., 155. 
 
 334. Chamberlin, Terminal Moraines, G. S. 3d Ann. Rep., 295. 
 337. Todd, Terminal Moraines in Dakota, G. S. Bull. No. 144, 16. 
 337. McGee (Drift Plains of Iowa), G. S. 11th Ann. Rep., 393. 
 
 Gilbert, Modification of Great Lakes by Earth Movement, 
 N. G. M., viii, 233. 
 
 339. Upkam, Glacial Lake Agassiz, G. S. Monogr. XXV. 
 
 340. Taylor, Studies in Indiana Geography, Terre Haute, 1897. 
 
 Short History of the Great Lakes. 
 
 344. Dryer, Studies in Indiana Geography, Terre Haute, 1897. 
 
 The Morainic Lakes of Indiana. 
 
 345. Bell, The Labrador Peninsula, S. G.M., xi, 335. 
 
416 PHYSICAL GEOGRAPHY. 
 
 Chapter XII. — Special References. 
 
 PAGE 
 
 351. Shaler, Seacoast Swamps of Eastern U. S., G. S. 6th Ann. 
 
 Rep., 359. 
 351. Shaler, Sea and Land. Charles Scribner's Sons, 1894. 
 354. Gilbert, Features of Lake Shores, G. S. 5th Ann. Rep., 75. 
 
 358. Shaler, Natural History of Harbors, G. S. 13th Ann. 
 
 Rep., 93. 
 
 359. Hatcher (Savages and Shore Lines in Patagonia), N. G. M., 
 
 viii, 306, 312. 
 366. A. Geikie, Scenery of Scotland, 2d ed. (Shore Features). 
 
 Macmillan & Co., 1887. 
 379. Darwin, Coral Reefs. D. Appleton & Co., 1889. 
 382. Dana, Corals and Coral Islands. Dodd, Mead & Co., 1890. 
 382. A; Agassiz, Letter in Amer. Journ. Science, Feb., 1898. 
 
 APPENDIX M. 
 
 The following list of map-sheets, selected from those published by 
 the U. S. Geological Survey and the U. S. Coast and Geodetic Sur- 
 vey, will be found of service in illustrating various examples of land 
 forms referred to in Chapters VI to XII. Complete lists of maps 
 published by these Surveys can be had, free of charge, on application. 
 The sheets here named might be supplemented by many others in 
 illustration of special localities. Some account of the cost and of 
 the method of ordering and using the maps is given in the Journal 
 of School Geography, September, 1897, and October, 1898. Coast 
 Survey maps are here marked " C. S." The others, unless specially 
 designated, are published by the Geological Survey. 
 
 Chapter VI. — Plains and Plateaus. 
 
 PAGE 
 
 113. Relief Map of New Jersey, published by the State Geological 
 
 Survey, Trenton, N. J. ; price, 25 cents. 
 130. Nomini, Md. 
 
APPENDIXES. 417 
 
 PAGE 
 
 138. Niagara Falls, Syracuse, 'Oneida, Ithaca, Elmira, N. Y. 
 140-153. Topographic Atlas of the United States, folio 1, Physio- 
 graphic Types, Pis. I-III. 
 141. Mt. Trumbull, Diamond Creek, Ariz. 
 147. Kanawha Falls, Nicholas, W. Va. 
 
 150. Sewanee, Tenn. ; Kaaterskill, N. Y. 
 
 151. Watrous, Corazon, N. M. ; Abilene, Brownwood, Tex. 
 Springfield, Bolivar, Tuscumbia, Mo. 
 
 Mt. Trumbull, Kaibab, Echo Cliffs, Ariz. 
 
 Chapter VII. — Mountains. 
 
 165. Disaster, Nev. ; Alturas, Cal. 
 
 170. Deadwood, Rapid City, S. D. 
 
 172. Platte Canyon, Huerfano Park, Col. 
 
 187. Asheville, Mt. Mitchell, Pisgah, N. C. 
 
 190. Atlanta, Ga. (Stone mountain is a fine example of a monad- 
 nock on the uplands of Georgia.) 
 
 190. Harrisburg, Hummelstown, Lykens, Pa. 
 
 192. Chesterfield, Granville, Mass. ; Winsted, Derby, Bridgeport, 
 Conn. 
 
 196. C. S. No. 710. 
 
 Chapter VIII. — Volcanoes. 
 
 215. Shasta, Cal.; San Francisco Mountain, Ariz. 
 
 216. Crater Lake (special sheet), Oregon. 
 
 Chapter IX. — Rivers and Valleys. 
 
 226. Citra, Fla. 
 
 229. Gallatin, Shoshone, Yellowstone National Park. 
 
 239. Mesa de Maya, Col. 
 
 242. Versailles, Tuscumbia, Mo. 
 
 243. Minden, Nebr. 
 
 245. 8-Sheet Map of the Alluvial Valley of the Mississippi River, 
 published by the Mississippi River Commission, St. Louis, Mo. 
 
418 PHYSICAL GEOGRAPHY. 
 
 PAGE 
 
 249. Dahlonega, Gainesville, Walhalla, Ga. 
 
 252. Great Falls, Mont. 
 
 255. Delaware Watergap, Pa.; Harpers Ferry, Va. 
 
 260. New London, Norwich, Conn.; State Map of Rhode Island. 
 
 261. Haarlem, Tarrytown, West Point, Poughkeepsie, N. Y. 
 
 Chapter X. — The Waste of the Land. 
 
 277. Lake, Wyo. (Two-Ocean Creek). 
 
 279. Independence, Marshall, Mo. 
 
 286, Donaldsonville, La. 
 
 287. 8-Sheet Map of the Alluvial Valley of the Mississippi Eiver. 
 
 (See above.) 
 
 293. C. S. No. 194. 
 
 Chapter XI. — Climatic Control of Land Forms. 
 
 306. Disaster, Granite Range, Long Valley, Nev. 
 
 334. Springfield, Mass.; Cohoes, N. Y. 
 
 334. Topographic Atlas of the United States, folio 1, PL VI. 
 
 338. Oconomowoc, Sun Prairie, Wis. 
 
 342. Elizabethtown, Mt. Marcy, N. Y. 
 
 343. Oriskany, N. Y.; Minneapolis, St. Paul, Minn.; Marseilles, 
 
 Ottawa, Lasalle, 111. 
 
 343. Rochester, N. Y.; Minneapolis, Minn. 
 
 Chapter XII. — Shore Lines. 
 
 351. C. S. No. 21. 
 
 351. C. S.Nos. 30, 204. 
 
 352. C. S. Nos. 11, 14.5, 419. 
 
 352. C. S. Nos. 123, 154. 
 
 353. C. S. No. 143. 
 
 354. Asbury Park, Sandy Hook, N. J., C. S. No. 121. 
 357. C. S. No. 408. 
 
 364. Martha's Vineyard, Gay Head, Mass., C. S. No. 112. 
 
 371. C. S. No. 194. 
 
IJSTDEX. 
 
 Adirondacks, 138, 342. 
 Agriculture, 36, 282, 124, 125. 
 
 and irrigation, 45, 288. 
 
 and soil, 7, 124, 134, 189, 268. 
 
 Alabama, 134, 146. 
 Alaska, 195, 196, 327, 330. 
 Allegheny mountains, 190, 256. 
 
 plateau, 138, 146, 149, 194, 
 
 200, 242. 
 
 river, 254. 
 
 Alluvial fans, see Fans. 
 
 Alps, 172, 177, 184, 186, 256, 277. 
 
 glaciers of, 327, 329, 330, 332. 
 
 Amazon, 237, 259. 
 
 Andes, 31, 177, 302, 306, 330. 
 
 Andorra, 185. 
 
 Animals, in caves, 225. 
 
 and climate, 55. 
 
 on deserts, 321. 
 
 distribution, l07. 
 
 on islands, 109, 381. 
 
 on mountains, 175, 186. 
 
 in ocean, 88, 106. 
 
 Antarctic regions, 66, 325. 
 Anticyclones, 34, 49, 405. 
 Ants, 267, 310. 
 Arabia, 316. 
 Argentina, 177, 301. 
 Argon, 25. 
 Aristotle, 11. 
 
 Arizona, climate, 298, 312. 
 
 • plateaus, 144, 151, 155, 324. 
 
 volcanoes, 214, 218. 
 
 waste slopes, 309. 
 
 Arkansas river, 282. 
 Artesian wells, 126, 137, 228. 
 Atlantic City, 115, 127, 353. 
 Atlantic ocean, 40, 62, 66, 69, 78, 
 
 81, 82. 
 Atmosphere, 22, 23, 25, 27, 29, 402. 
 Atolls, 379, see Reefs. 
 Australia, 109, 376. 
 Avalanches, 178. 
 Azores, 212. 
 
 Bad lands, 303. 
 Baltimore, 131. 
 Banks, 352. 
 Baraboo, 198. 
 Barometer, 23. 
 Baselevel, 120. 
 Basin, interior, 304, 307. 
 
 river, 230. 
 
 rock, 342, 345, see Lakes. 
 
 waste-filled, 281, 284, 307, 311, 
 
 317, see Waste. 
 Basques, 185. 
 Bays, 129, 131, 196, 296, 357, 358, 
 
 365. 
 Beach, 351, 362, 363, 364. 
 
 419 
 
420- 
 
 PHYSICAL GEOGRAPHY. 
 
 Beavers, 107. 
 Bedouins, 18. 
 Bench, 360. 
 Black Hills, 169. 
 Black Rock desert, 306. 
 Blue Ridge, 187, 256. 
 Bluff, 353, 354, see Cliff. 
 Bolivia, 306. 
 Bore, 87. 
 
 Boulder clay, 336. 
 Boundaries, 17, 177, 249. 
 Brazil, 31. 
 
 Bristol channel, 365. 
 British Columbia, 196, 295. 
 British Guiana, 152. 
 Buenos Ayres, 231, 233, 350. 
 Butte, 150, 216, 217, 221. 
 
 Caldera, 212, 213, 215. 
 California, climate, 21, 37, 302. 
 
 coast, 118. 
 
 • fans, 288, 308. 
 
 moraines, 331. 
 
 mountains, 167, 195. 
 
 valley, 288, 291. 
 
 volcanoes, 203, 214, 220. 
 
 Calms, 32. 
 
 Camel, 18, 321. 
 
 Canada, 137, 217, 232, 333, 344, 
 
 345. 
 Canals, 232, 341. 
 Canyons, 141, 144, 148, 156, 158, 
 
 218. 
 Carbonic acid, 25, 26. 
 Caribou, 108. 
 Cassowary, 109. 
 Catskill moimtains, 146. 
 Caucasus, 175, 185, 330. 
 Caverns, 225, 362. 
 Central America, 31, 206, 208. 
 
 Chagos bank, 378. 
 
 Charleston, 125, 353. 
 
 Chattahoochee, 249. 
 
 Chesapeake bay, 130, 228, 260. 
 
 Chicago, 341. 
 
 Chili, 37, 177, 299. 
 
 China, 177, 289, 294, 317. 
 
 Chinook wind, 176. 
 
 Chippewa, 334. 
 
 Chunnenugga ridge, 135. 
 
 Cinder cone, 204. 
 
 Cliff dwellers, 146. 
 
 Cliffs, 143, 147, 156, 158, 196, 269. 
 
 sea, 219, 355, 360, 363, 366. 
 
 Climate, 20, 52, 153, 297. 
 
 and animals, 55, 321. 
 
 and land forms, 297. 
 
 and man, 56. 
 
 and plants, 54, 319. 
 
 and shore lines, 372, 374. 
 
 changes of, 298, 318. 
 
 dry, 46, 299, 319. 
 
 glacial, 324. 
 
 of lands, 98. 
 
 of mountains, 167, 175, 176. 
 
 of plains, 140, 153. 
 
 • of plateaus, 144, 153. 
 
 Cloudbursts, 145, 300. 
 Clouds, 403, 404. 
 Coal, 149. 
 Coastal plains, 118, 122. 
 
 ancient, 136, 137, 139. 
 
 belted, 132, 247, 249. 
 
 embayed, 129. 
 
 Cold wave, 21, 49. 
 Colorado, 208, 272, 316, 331. 
 Colorado canyon and river, 144, 
 
 156, 189, 235, 301. 
 Columbia, 125. 
 Columbus, 398. 
 
INDEX. 
 
 421 
 
 Commerce, 7, 20. 
 
 Congo, 237. 
 
 Conical projection, 395. 
 
 Connecticut, 192, 334. 
 
 Conseguina, 206. 
 
 Continental shelf, 70, 96, 104. 
 
 Continents, 93, 94, 95. 
 
 Contours, 397. 
 
 Coral reefs, see Eeefs. 
 
 Cotopaxi, 207. 
 
 Cotton, 20, 125, 135. 
 
 Crater, 202. 
 
 Cuba, 375, 377. 
 
 Cuesta, 133. 
 
 Cumberland plateau, 146. 
 
 Currents, 77, 79, 81, 97, 364, 375, 
 
 Cyclones, 34, 39, 49, 405.' 
 
 Dacia bank, 208. 
 
 Dakota, North and South, 169. 
 
 303, 335, 337, 
 Danube, 285, 292. 
 Dead sea, 305, 307. 
 Deception island, 213. 
 Dekkan, 122. 
 Delaware bay and river, 130, 255, 
 
 296. 
 Deltas, 130, 196, 197, 292, 294, 369, 
 
 370. 
 
 dissected, 296. 
 
 in lakes, 234. 
 
 tidal, 353. 
 
 Denudation, 105. 
 
 Denver, 300. 
 
 Deserts, 18, 30,46, 146, 301, 306, 333. 
 
 Dew, 47. 
 
 Dikes, 216, 221. 
 
 Distributaries, 293. 
 
 Divides, 230, 246, 250, 251, 312, 
 
 344. 
 
 Doldrums, 32, 37, 39, 81, 97. 
 Dredge, 62. 
 Drift, glacial, 328. 
 Drought, 21, 320. 
 Drumlins, 338. 
 
 Dunes, 104, 315, 351, 353, 354. 
 Dust, 314, 316, 317, 
 Dwarfs, 2, 5, 19, 
 
 Earth, 8, 9, 15, 19, 400. 
 
 shape and size, 10, 12, 13, 14, 
 
 385, 386. 
 Earthquakes, 76, 163, 166, 183, 
 
 187, 199, 207. 
 
 waves, 75, 76. 
 
 Ecuador, 207. 
 Enchanted mesa, 151. 
 England, 139, 365. 
 Equinox, 401. 
 Eratosthenes, 386. 
 Erosion, 105, 181. 
 
 glacial, 329. 
 
 Eruptions, 199, 201, 205. 
 Erzgebirge, 195. 
 Escarpments, 156. 
 Eskers, 337. 
 Eskimos, 4, 19, 326. 
 Eudoxus, 385. 
 
 Fall line, 127, 134. 
 
 Falls, 127, 134, 144, 234, 236, 252, 
 
 338, 342. 
 Famines, 21. 
 
 Fans, 162, 166, 275, 288, 295, 307. 
 Faroe, 219. 
 Faults, 158, 162, 165. 
 Feldspar, 101. 
 Fertilizers, 125. 
 Fiji, 378, 382. 
 Fingal's cave, 362. 
 
422 
 
 PHYSICAL GEOGRAPHY. 
 
 Finland, 345. 
 
 Fiords, 196, 345, 358, 369. 
 
 Fisheries, 44, 71, 131, 134. 
 
 Flood plain, 242, 244, 279, 280, 
 
 286, 301, 333. 
 Floods, 21, 148, 206, 211, 246, 277, 
 
 289, 310, 313. 
 
 and lakes, 182, 234. 
 
 sea, 294, 350. 
 
 Florida, 21. 
 
 Foehn wind, 176. 
 
 Forests, 2, 32, 125, 135, 148, 208, 
 
 218, 273. 
 on mountains, 171, 174, 176, 
 
 188, 193. 
 Fossils, 71, 96, 102, 119, 136, 173. 
 France, 177, 215, 220, 249, 253. 
 Fraser river, 253, 295. 
 Frost, 47. 
 Fundy, Bay of, 87, 365. 
 
 Galapagos, 375. 
 
 Galveston, 351. 
 
 Ganges, 293, 294. 
 
 Genoa, 118. 
 
 Georgia, 249. 
 
 Germany, 188, 191, 195, 254, 287. 
 
 Geysers, 229. 
 
 Giants' causeway, 219. 
 
 Gibraltar, 366. 
 
 Glacial period, 330. 
 
 Glacier, 325, 328, 330. 
 
 Alpine, 326. 
 
 ancient, 331. 
 
 Laurentian, 333. 
 
 Scandinavian, 333. 
 
 Glens, 194. 
 Globes, 393. 
 Globigerina, 68, 103. 
 Gold, 195, 220. 
 
 Gorges, 183, 282, 342, 348. 
 
 Grand wash, 156. 
 
 Granite, 101, 193, 225. 
 
 Gravity, 15. 
 
 Grazing, 37, 140, 153, 170, 176, 
 
 186, 221, 320. 
 Great Basin, 304, 306. 
 Great Lakes, 340, 341, 355. 
 Greece, 295. 
 
 Greek philosophers, 11, 12. 
 Green river basin, 285. 
 Greenland, 4, 326. 
 Ground water, 224, 227, 278, 292. 
 Gulf Stream, 81. 
 
 Hachures, 396. 
 
 Hail, 45. 
 
 Harbors, 196, 354, 356, 358, 375. 
 
 Harvard geographical models, 394. 
 
 Hatteras, 352. 
 
 Hawaiian islands, 213. 
 
 Headlands, 358, 364, 365. 
 
 Herculaneum, 207. 
 
 Highlands of Scotland, 194, 196, 
 
 332, 366. 
 Himalaya, 172, 177, 181, 258, 280, 
 
 284, 312, 327. 
 Hoangho, 289, 293, 294. 
 Hood, Mount, 214. 
 Horse, 140. 
 Horse latitudes, 33. 
 Hudson river, 261. 
 Hungary, 244, 285. 
 Hurricane ledge, 156. 
 Hurricanes, 22, 39, 75, 294. 
 
 Ibex, 186. 
 Ice, 65, 234. 
 
 falls, 179. 
 
 sheets, 325, 333. 
 
INDEX. 
 
 423 
 
 Icebergs, 66, 325, 326. 
 
 Iceland, 210, 229. 
 
 Idaho, 211, 218. 
 
 Illinois, 334, 344. 
 
 India, 46, 122, 177, 219, 258, 290, 
 
 294, 308. 
 Indian ocean, 43, 80. 
 Indiana, 334, 344. 
 Indians, 145, 304, 322. 
 Inlets, 352. 
 Iowa, 338. 
 Iron ore, 149, 195. 
 Irrigation, 37, 45, 288, 308. 
 Islands, 67, 71, 196, 358, 360, 365, 
 
 369, 372. 
 
 coral, 67, 379. 
 
 volcanic, 67, 203, 209. 
 
 Isotherms, 29, 34, 35. 
 Italy, 202, 207, 294. 
 
 Jaguar, 108. 
 Japan, 76, 207, 294. 
 Java, 207. 
 JoruUo, 203. 
 Jura, 167. 
 
 Kaibab plateau, 157, 158. 
 Kanauha river, 258. 
 Kangaroo, 110. 
 Kansas, 21. 
 Kashmir, 284. 
 Kentucky, 147, 268. 
 Klondike, 195. 
 Krakatoa, 24, 76. 
 Krypton, 25. 
 
 Lagoons, 351, 353, 370. 
 Lake Agassiz, 339. 
 
 Bonneville, 318. 
 
 Crater, 215, 216. 
 
 Lake Erie, 138, 281, 354. 
 
 Geneva, 234, 295. 
 
 Great Salt, 305, 307, 318. 
 
 Itasca, 344. 
 
 Lahontan, 319. 
 
 Nyassa, 233. 
 
 Pepin, 334. 
 
 Shirwa, 305. 
 
 Snag, 204. 
 
 Titicaca, 306. 
 
 Van, 305. 
 
 Victoria Nyanza, 233. 
 
 Lakes, 226, 232, 245, 256, 276, 282, 
 
 291, 302. 
 
 Alpine, 256. 
 
 glacial, 335, 339, 341, 345. 
 
 in mountains, 163. 
 
 salt, 305, 311. 
 
 shore lines, 354, 360. 
 
 temperature, 233, 234. 
 
 volcanic, 211, 213, 214. 
 
 Land and sea breezes, 44. 
 Lands, 91, 93, 95, 98, 104, 105. 
 
 waste of, 70, 101, 103. 
 
 Landslides, 162, 181, 184, 187, 270, 
 
 280. 
 Latitude, 17, 388, 391. 
 Lava, 103, 200, 201. 
 flows, 204, 209, 210, 219, 
 
 268. 
 
 plateaus, 211, 218. 
 
 table mountains, 219. 
 
 Ledges, 298. 
 Life, 88, 105, 109. 
 Limestone, 102, 225, 226, 266. 
 Llanos, 320. 
 Loess, 317. 
 Long Branch, 354. 
 Longitude, 17, 388, 391. 
 Lookout, Cape, 352. 
 
424 
 
 PHYSICAL GEOGRAPHY. 
 
 Madras, 122. 
 
 Magnetic poles, 399. 
 
 Magnetism, terrestrial, 398. 
 
 Maine, 372. 
 
 Mammoth cave, 225. 
 
 Man, races of. 111. 
 
 Manchester, 237. 
 
 Mangrove, 373. 
 
 Maps, 393. 
 
 Marquesas islands, 379. 
 
 Marsh, 140, 305, 311, 351. 
 
 Massachusetts, 192, 339. 
 
 Meander belt, 245. 
 
 Meanders, 241, 243, 253, 284. 
 
 Mercator projection, 395. 
 
 Merced river, 288, 291. 
 
 Meridians, 16, 17, 391. 
 
 Merrimac, 334, 343. 
 
 Merc, 324. 
 
 Mesa, 150, 219, 221. 
 
 Meuse river, 249. 
 
 Mexico, 31, 121, 203, 208, 299, 312, 
 
 357. 
 Mica, 101. 
 Michigan, 149. 
 
 Mining, 134, 137, 149, 171, 195. 
 Minneapolis, 237, 343. 
 Minnesota, 149, 337. 
 Mississippi river, 237, 239, 259, 
 
 338, 340, 344. 
 
 • delta, 293, 296, 369. 
 
 flood plain, 21, 244, 246, 286, 
 
 287. 
 
 meanders, 245. 
 
 Missouri, 154, 242, 252, 338. 
 
 river, 220, 242, 279. 
 
 Models, 393, 394. 
 Mohawk, 138, 223, 341. 
 Monadnock, 190, 193, 197. 
 Monsoons, 40, 43, 88. 
 
 Montana, 220. 
 Monte Nuovo, 202. 
 Moon, 86, 406. 
 Mountains, 159, 164, 176. 
 
 buried, 218. 
 
 embayed, 195, 295. 
 
 lofty, 172, 174, 204, 292, 293, 
 
 330. 
 
 old, 167, 188, 372. 
 
 subdued, 187. 
 
 young, 161, 163, 167. 
 
 Moraines, 328, 334, 335. 
 Moselle river, 249, 254. 
 Mt. Blanc, 174. 
 
 Nansen, 79, 326. 
 
 Narragansett bay, 260. 
 
 Natural bridges, 226. 
 
 Navigation, 39, 60, 67, 78, 81, 87, 
 
 353, 358. 
 
 river, 128, 236, 237, 260. 
 
 Nebraska, 21. 
 
 Neckar river, 254. 
 
 Necks, volcanic, 216. 
 
 Netherlands, 97, 354. 
 
 Nevada, 161, 164, 309, 319. 
 
 New England, 20, 192, 336. 
 
 New Hampshire, 192. 
 
 New Jersey, 113, 255, 296, 352, 
 
 354, 357. 
 
 New Mexico, 151, 214, 218, 316. 
 New York, 146, 262, 339. 
 Newton, 12, 86. 
 Niagara, 137, 232, 234, 341, 
 
 343. 
 Nile, 38, 233, 301, 387. 
 Nitrogen, 25. 
 Nomads, 140, 153. 
 Norfolk, 131. 
 Normandy, 253, 356, 359. 
 
INDEX. 
 
 425 
 
 North Carolina, 125, 187, 342, 351, 
 
 357. 
 Norway, 345, 358, 368. 
 
 Oasis, 322, 323. 
 
 Oceans, 57, 59, 61, 67, 69, 77, 88, 
 
 104. 
 Ohio, 147, 334, 337. 
 
 river, 234, 243, 344. 
 
 Ontario, 137. 
 
 Ooze, 68. 
 
 Oregon, 161, 211, 214, 215, 218. 
 
 Osage river, 242. 
 
 OxbovF lake, 245. 
 
 Oxygen, 25, 26, 64. 
 
 Ozark plateau, 154. 
 
 Pacific ocean, 40, 43, 53, 67, 76, 
 
 375, 378. 
 Parallels, 16, 17, 388. 
 Pamlico sound, 130. 
 Pass, 177. 
 Patagonia, 359. 
 
 Peaks, 174, 180, 271, 272, 273. 
 Peary, 326. 
 Peedee river, 370. 
 Peneplain, 152. 
 Pennsylvania, 137, 190, 242, 255, 
 
 296. 
 Persia, 308, 311. 
 Peru, 302, 320. 
 
 Piedmont belt, 188, 190, 253, 274. 
 Pikes peak, 272. 
 Plains, 1.39, 152, 221. 
 coastal, 118, 122, 349, 355, 
 
 372. 
 
 dust, 316. 
 
 glacial, 337. 
 
 river-made, 290, 291, 292. 
 
 Planets, 9. 
 
 Plants, 15, 54, 90, 105, 107, 224, 
 
 319. 
 
 on atolls, 380. 
 
 on deserts, 319. 
 
 on mountains, 175. 
 
 on plateaus, 146. 
 
 Plateaus, 141, 145, 150, 155, 271. 
 
 Platforms, 143. 
 
 Platte river, 243. 
 
 Playas, 306. 
 
 Po, 292. 
 
 Population, 118, 322. 
 
 of mountains, 184, 188, 194. 
 
 of river-made plains, 289, 292, 
 
 294. 
 
 See Settlements. 
 Potomac river, 256, 260, 262, 296. 
 Prairies, 135. 
 Projection of maps, 394. 
 Promontories, 196, 358, 372. 
 Pyrenees, 177, 185. 
 
 Quartz, 101, 275. 
 
 Races of men. 111. 
 Railroads, 134, 178, 193, 254. 
 Rain gauge, 45. 
 Rainfall, 1, 31, 37, 45, 403. 
 
 and agriculture, 45, 156, 320. 
 
 on mountains, 164, 171, 175, 
 
 299. 
 Rapids, 144, 234, 254, 338, 342, 
 
 345. 
 Red river, 280. 
 Reefs, coral, 374, 377, 382. 
 
 sand, 121, 129, 350, 353, 370. 
 
 Relief, 396. 
 
 Rhine, 192, 252, 259, 287, 292. 
 
 Rhone, 234. 
 
 Ridges, 174, 180. 
 
426 
 
 PHYSICAL GEOGRAPHY. 
 
 Rio Grande, 371. 
 
 Rivers, 222, 230, 238, 243, 299, 356. 
 
 antecedent, 258.. 
 
 dismembered, 260. 
 
 engrafted, 259. 
 
 graded, 237. 
 
 mature, 250. 
 
 old, 251. 
 
 revived, 252. 
 
 w^ithering, 300, 304. 
 
 young, 163, 231, 329. 
 
 Roads, 149, 224. 
 
 in mountains, 177, 186, 193, 
 
 285. 
 
 on plains, 115, 121, 134. 
 
 Rochester, 237, 343. 
 
 Rock basins, 342, 345. 
 
 Rock waste, see Waste. 
 
 Rocks, 101. 
 
 Rocky mountains, 172, 175, 253, 
 
 270, 330, 331. 
 Roraima, 152. 
 Rotation of earth, 15. 
 Russia, 152, 153, 185. 
 
 Sahara, 18, 30, 299, 315, 320, 323, 
 
 333. 
 Salerno, 367. 
 Salinas, 306. 
 Salt, 63, 305, -307. 
 San Luis valley, 316. 
 Sand, 315, 316. 
 Sand reefs, see Reefs. 
 Sandstone, 101, 193. ' 
 Savannah, 249, 353. 
 Scale, 397. 
 
 Scandinavia, 333, 345, 359. 
 Schwarzwald, 188. 
 Scotland, 194, 196, 332, 339, 366. 
 Seasons, 35* 401. 
 
 Seine, 87, 250, 253, 254, 365. 
 Selkirk mountains, 175. 
 Settlements on coasts, 134, 350, 
 358, 367, 368. 
 
 on mountains, 164, 167, 169, 
 
 171, 183, 186, 193, 196. 
 
 on plains, 114, 121, 125, 128, 
 
 131, 134. 
 
 on plateaus, 146. 
 
 on rivers, 125, 134, 237, 286. 
 
 See Population. 
 Shasta, Mt., 214, 282. 
 Sheavwits plateau, 144, 155, 210. 
 Sheetflood, 313. 
 Ships, 20, 58, 73. 
 Shore lines, 347, 349, 357, 366, 372. 
 
 of deltas, 369. 
 
 of lakes, 360, 368. 
 
 Siberia, 139, 233. 
 
 Sierra Nevada, 195, 331. 
 
 Simum, 316. 
 
 Sinkholes, 225, 226. 
 
 Slate mountains, 191, 259. 
 
 Snake river, 218. 
 
 Snow, 2, 45, 47, 177, 206, 209, 
 
 404. 
 Snow line, 176. 
 Soil, 265, 268, 274, 337, 345. 
 Solar system, 9. 
 Solstice, 401. 
 Sounding, 61. 
 Sounds, 196, 357. 
 South Carolina, 123, 249, 352. 
 Spain, 177. 
 Spits, 364. 
 
 Springs, 163, 226, 228, 292. , 
 St. Elias, Mt., 330. 
 St. Helena, 75, 209. 
 St. Lawrence, 232, 234, 260, 340, 
 
 344. 
 
INDEX. 
 
 A21 
 
 Stacks, 360, 364. 
 Stars, 8, 388, 400. 
 Steppes, 320. 
 
 Stereographic projection, 394. 
 Storms, 21, 22, 33, 36. 
 Subequatorial belts, 37. 
 Subtropical belts, 37. 
 Sudan, 38. 
 Sun, 8, 400. 
 Surf, 74. 
 
 Susquehanna, 242, 256, 296. 
 Svanetians, 185. 
 Swamps, 126. 
 Sweden, 345. 
 Switzerland, 167, 185. 
 See Alps. 
 
 Table mountains, 219. 
 Talus, 143, 146, 162, 269, 271. 
 Tarim river, 311. 
 
 Temperature of atmosphere, 27, 28, 
 41. 
 
 and currents, 81, 82. 
 
 earth, 99. 
 
 lakes, 233. 
 
 oceans, 63, 69. 
 
 Tennessee, 268. 
 
 Terraces, 280, 334. 
 
 Texas, 351, 352, .371. 
 
 Thermometer, 27, 61. 
 
 Thunderstorms, 32, 39, 45. 
 
 Tibet, 24, 208, 311. 
 
 Tidal deltas, 353. 
 
 Tides, 37, 83, 87, 294, 352, 365. 
 
 cause of, 86, 406. 
 
 in lakes, 88. 
 
 Tiger, 109. 
 Till, .336. 
 
 Tonga islands, 203. 
 Tornadoes, 34. 
 
 Torrents, 275, 278. 
 Trade winds, 31. 
 Tree line, 176. 
 Tributaries, 286. 
 Tropical calms, 33, 36. 
 Tuamotu, 381, 382. 
 Turkestan, 311. 
 
 Uinkaret plateau, 155, 157, 210. 
 Uinta mountains, 285. 
 Utah, 164, 309, 318. 
 
 Valleys, 103, 153, 222, 239, 244. 
 
 crosswise, 169, 183, 255. 
 
 filled, 278, 282. 
 
 in mountains, 174, 180. 
 
 in plains, 119, 125, 133, 153. 
 
 in plateaus, 141, 148. 
 
 lengthwise, 169, 183, 255. 
 
 terraced, 278, 280. 
 
 Vegetation, 25, 45, 54, 140. 
 Venezuela, 37, 320. 
 Vera Cruz, 121. 
 Vermont, 192. 
 Vesuvius, 200, 207, 213. 
 Virginia, 1-30, 188, 357. 
 Volcanoes, 12, 99, 103, 199, 201, 
 205, 208, 213. 
 
 Wadies, 299. 
 Wales, 188. 
 Wallace's line, 110. 
 Washington, 211, 218, 268. 
 Waste of the land, 143, 263, 267, 
 
 271, 273, 275. 
 
 and climate, 298. 
 
 glacial, 328. 
 
 in basins, 281, 284, 306, 309, 
 
 311, 316. 
 in valleys, 278, 282, 286, 302. 
 
428 
 
 PHYSICAL GEOGRAPHY. 
 
 Water vapor, 25, 403. 
 Waterfalls, see Falls. 
 Watergap, 170, 255. 
 Watershed, see Divide. 
 Waves, 70, 73, 104, 294, 360, 370. 
 
 earthquake, 75. 
 
 Weather, 21, 33, 48, 405. 
 
 maps, 49, 405. 
 
 ■ prediction, 21, 52. 
 
 Weathering, 13, 99, 100, 265, 267, 
 
 271. 
 Wells, 227. 
 West Virginia, 147, 258. 
 
 Westerly winds, 31, 33. 
 Winds, 29, 36, 40, 44, 104, 402, 
 405. 
 
 and currents, 79. 
 
 and denudation, 314. 
 
 Wisconsin, 130, 197, 228, 274, 339. 
 Wyoming, 285, 303. 
 
 Yazoo river, 287. 
 Yellowstone park, 26, 229, 277. 
 Yellowstone river, 235. 
 
 Zones, 27, 48, 52, 401. 
 
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