.^-\=,^^^. ., «f ■•%= K ■ . - A • c A ■^ ' -^ \£Ke ,^x ^^. \' ^ x/.^ ^y'% ^, -- .f^~ -dr. ,A"^ .-\-^:f^/ .\. ^ -^^z ■i ^ o 0^ ■^>^ .^Vv^ ^^ ^^• V'« V 5^ 3^ V -" A^^ A % *' 8 1 V * ^^^ ,,^^ Digitized by the Internet Archive in 2011 with funding from The Library of Congress http://www.archive.org/details/outlinesofphysic01fitc OUTLINES PHYSICAL GEOGRAPHY. BY GEOEGE W. FITCH. rLLTTSTRATED BY 3n 3h^ n)i ^umnQM (Bn^xMwp " Let me once understand the real geography of a country, — its organic structure, if I may so call It ; the form of its skeleton, — that is, of its hills ; the magnitude and course of its veins and arteries,— that is, of its streams and rivers ; let me conceive of it as a whole, made up of connected parts ; and then the position of man's dwellings, viewed in refer- ence to these parts, becomes at once easily remembered, and lively and intelligible besides." Dk. Aknold. EIGHTH LAEGE EDITION. NEW YORK: J. H. COLTOlSr AISTD COMPANY, 172 WILLIAM STEEET. SHELDON, BLAKEMAN AND COMPANY, 115 NASSAU STREET. 1856. G-555 ENTERED, ACCORDING TO ACT OF CONGRESS, IN THE TEAR 1855, BY J. H. COLTON & CO. AND G. W. FITOH, IN THE clerk's OFFICE OF THE DISTRICT COURT OF THE UNITED STATES FOR THE SOUTHERN DISTRICT OF NEW YORK. By Transter from U.S.Navai Academy AuM. 26 1S32 DAVIE8 AND K0BERT8, GEOBUE KtTSSELL & CO., ELECXKOTYPEKS. PEINTEES. PREFACE. The following pages have been prepared vrith. a view of supplying the "want of a treatise on Physical Geography, adapted to the use of Schools and Academies. It is rather a remarkable fact, that among the multitude and variety of school-books prepared for the schools in the United States, there is not one devoted exclusively to this science. The consequence is, that Physical Geography, as a separate study, is very rarely taught in our schools, and that all, or most of the knowledge acquired respecting it, is what is iacidently obtaiaed in pursuing other kindred studies. The Author has aimed to present none but well- authenticated facts, and ac- cordingly he has consulted the latest and most reliable authorities. Among the works from which valuable information has been obtained are " Eyelid's Principles of Geology," "Milner's Gallery of Nature," " Mil- ner's Geography," " Kemtz's Meteorology," " Hughes' Outliives OF Geography," and " Somerville's Physical Geography." In this connection the Author would acknowledge his great obligation to Lieut. M, F. INIaury, Superititendent of the National Observatory, Washington, for very valuable information on the recent deep-sea soundrags which he has caused to be made in the Atlantic Ocean. From Maury's " Sailing Di- rections" many interesting facts have been gleaned respecting the winds and currents of the ocean, trade routes, etc. To A. D, Bache, Superin- tendent of the United States Coast Survey, the Author is indebted for va- rious Eeports of the operations of that department, and for a Tide Table of the United States which was specially prepared for this book. The maps were compiled with the greatest care by Mr. George W, Colton, the aim being to exhibit the most remarkable and interesting features of Physical Geography, so far as they are capable of being represented to the eye. PREFACE. It is proper to observe that, in the preparation of this treatise, no attempt at originality was made, but simply an effort to digest and arrange the more important facts in an intelligible style for learners. In many in- stances the Author has employed the phraseology of other writers, without always defacing the pages with quotation marks and references. Length- ened extracts, and those containing peculiar views of an author, are credited to their proper sources. The Author can not refrain from expressing the hope that the book will meet the approbation of teachers, and excite in the minds of learners a de^re for further attainments in this interestiag department of science. CONTENTS. INTRODUCTION. Definition of Physical Geography— how divided— the First Part— the Second Part— the Third Part— the Fourth Part Pages 1-8 PART I. THE LAND. LESSON I. — ^Extent and Distribution of the Land 4-5 LESSON II. — Continents: Eastern continent — its extreme limits. North America: its length and breadth — area — coast-line — indentations. South America: its dimensions. 6-7 LESSON III. — Continents (contimied) : Eastern continent : its length and breadth — area. Europe: its dimensions— its peninsular character. Asia: its dimensions. Africa: its dimensions. Table of the area of the five grand divisions, their extent of coast-line, etc. General remarks on the continents 7-9 LESSON IV.— Islands : Australia — table of the area of some of the largest islands, and their comparative size — Eockall — chains of islands or continental islands — oceanic isl- ands — archipelagoes — single islands, St. Helena, Ascension Islands — volcanic islands — examples of islands suddenly formed by volcanic action, Graham Island 10-12 LESSON Y. — Coeal Islands : Great extent of coralline structures — Great Barrier Eeef— description of coral animals and their operations — an atoll— lagoons— encircling-reefs — barrier-reefs — action of the waves on the Great Barrier Eeef— Florida. Eeef— Florida Keys— coral fringes — observations on coral islands by Capt. Basil Hall 13-17 LESSON VI.— Mountains : Insulated mountains— usual arrangement of mountains- mountain systems of the two continents — secondary ranges — highest known mountains on the globe— loftiest summits in the other four grand divisions — table of heights above the sea of some remarkable inhabited sites— list of some remarkable heights which have been reached 18-21 LESSON VII. — The Mountain Systems of the Westeen Continent : JVorth American 3Iou7itains. — The Eocky Mountains, the highest summits— the Mountains of the West Coast — the Apalachian or Allegany ranges. Green Mountains, White Mountains, Adi- rondack Mountains, Catskill Mountains — highest summits in the Apalachian range — Ozark Mountains — the mountains in Mexico — South American Moimtai^is. — The Andes — how divided — peculiarities of each division. The mountains of Guiana — of Brazil. 22-26 LESSON VIII.— Mountain Systems of the Easteen CoNTmEiJ^TS : European Mount- ains.— "Yhe Balkan Mountains — the Alps, celebrated passes— the Appenines— the Car- pathian Mountains— the Mountains of the Spanish peninsula— the Scandinavian Mount- Vi CONTENTS. ains— the Ural Mountains. Asiatic Mountains.— The Himalaya Mountains— the Altai Mountains — the Hindoo-Koosh — the Mountains of Armenia — the chain of Mount Taurus. African Mountains. — Alias Mountains— the Mountains of Abyssinia— mountains of the •western coast— of the eastern coast— of South Africa Pages 26-33 LESSON IX.— Upland Plains oe Table-Lands : Table-lands of North America— pla- teau of Chihuahua— table-lands of South America — the most extensive table-land of Eu- rope — table-lands of Asia — elevation of the plain of Tibet — table-lands of Africa. , 34-36 LESSON X.— Lowland Plains : The great central plain of North America — prairies — the plain or lowland of the Atlantic coast — the great central plain of South America — llanos— selvas— pampas 36-40 LESSON XI.— Glaciers : Eegions of glaciers— their origin— movements of glaciers— ap- pearance of glaciers— their uses 40-43 LESSON XII.— Snow Mountains and Avalanches :' Drift, sliding, creeping, and ice avalanches— destructive efifects of avalanches 43-45 LESSON XIII.— Volcanoes : Active, intermittent, or extinct volcanoes— number and dis- tribution of volcanoes 45-47 . LESSON XIV.— YoLCANic Kegions : The Volcanic Regions of the Andes. — Of North America. Volcanoes of Mexico — of the West India Islands. Volcanic Region from the Aleutian Isles to the Moluccas and Isles of Sunda. Volcanic Regions of the Medi- terranean 47-52 LESSON XV. — Vesuvius : Description of its crater — Herculaneum and Pompeii. Etna — us eruption in 1669. Volcanoes of /ceZcmcZ- eruption of Skaptar Jokul in 17S3. srs 52-57 LESSON XVI.— Earthquakes : Proof that earthquakes and volcanoes have a similar or- igin—intensity of earthquakes— movements of the earth they produce— their duration, instances — their frequency — their effects in elevating and depressing the land, instances — clefts and fissures— fatal effects of earthquakes 57-59 PART n. THE WATERS. LESSON I.— Chemical Composition of Water : The fresh waters— the salt water— salts contained in sea-water — salt-water lakes — the benevolence of the Deity as manifested in the wide diffusion of water over the globe 60-62 LESSON II.— Mineral Springs: Acidulous waters — chalybeate springs — sulphurous springs — saline springs, the salt springs at Salina and Syracuse — mmeral springs of the United States 63-65 LESSON III. — Eivees: Their sources — basins — area of the principal river basins — course of rivers— table of river windings 65-67 LESSON IV. — KivERS {continued) : 'lUe fall oi rivers— cataracts— the Falls of Niagara — of St. Anthony— other noted falls in America— principal waterfalls of the eastern con- tinent 68-71 LESSON V. — EivERS {continued) : The termination of rivers — deltas — the delta of the Mississippi, how produced— sedimentary matter of the Ganges — oceanic rivers — conti- nental rivers — causes which determine the magnitude of rivers — proportional quantity of water discharged by some of the principal rivers— inundations of rivers— historic asso- ciations of rivers 71-76 CONTENT So Vn LESSON VI.— The Eivee Systems of the "Westeen Continent : North American EiV' 6rs.— Divisions of the continent with reference to its drainage— the Mississippi— the Mis- souri — the Ohio— the St. Lawrence — other streams draining the Atlantic slope— rivers draining the region west of the Eocky Mountains— rivers draining the northern slope — other streams. = ,.... Pages 76-79 LESSON VII.— EivER Systems of the Western Continent {continued) : South Amer- ican Elvers. — The Orinoco— the Amazon — the Eio de la Plata 80-81 LESSON VIII.— ErvER Systems of the Eastern Continent : The two principal river systems of Europe— the Volga — Danube — Ehine — other European rivers 82-84 LESSON IX.— EivER Systems of the Eastern Continent {continued) : The two princi- pal classes of Asiatic rivers— the Obi — Yenesei — ^I^ena — Ganges— the Indus — other Asiatic rivers— drainage by continental rivers. African Eivers.—T:he Nile— the Niger— other African rivers S4-8S LESSON X.— Lakes : Distribution of fresh-water lakes— salt-water lakes— physical dif- ference of lakes — lakes which have no outlet, and do not receive any running water — lakes which receive water, but have no apparent outlet — lakes which receive no streams, but give birth to some — lakes which both receive and discharge water— elevations of lakes o .,... 8&-90 LESSON XI.— Lakes {continued) : North American Lakes. — ^Lake Superior — Huron — Michigan— Ontario — other North American Lakes. South American Lakes.— "Lake Titi- caca 90-93 LESSON XII. — Lakes {continued) : European Lakes. — Tables of the dimensions of the principal European lakes, their elevations, etc. Asiatic Lakes. African Lakes . . 93-95 LESSON XIII.— The Ocean : Partial oceans and their branches— the Arctic Ocean — floating masses of ice— sheet ice — the Grinnell Expedition— icebergs — ^point of the great- est cold — the Atlantic Ocean — " Banks of Fucus"— the Pacific Ocean — the Indian Ocean —the Antarctic Ocean— discoveries of "Wilkes and Eoss 96-100 LESSON XIV. — The Ocean {continued) : Temperature— color — depth— deep-sea sound- ings 100-101 LESSON XV. — The Ocean {continued) : Waves — tides— theory of tides explained — tide table for the coast of the United States 105-109 LESSON XVI. — The Ocean {continued) : Currents— causes of the oceanic currents— arc- tic currentr— equatorial current— Mexican Gulf Stream 110-115 PART in. THE ATMOSPHEEE, LESSON I.— CoMPOBinON of Air : Properties of oxygen gas 116-llT LESSON II. — Properties op the Atmosphere: Transparency— fluidity — weight— how indicated— the use that is made of barometers to ascertain the height of mountains — elasticity of the atmosphere — eflPect of rarefied air on the human body. 118-121 LESSON III. — Winds: How caused — uses— how their direction is indicated — the direc- tion of the wind in the upper regions often the reverse of what it is in the lower — velo- city of winds. VariaUe Winds. — ^Table of the relative frequency of winds in different countries— cold winds — the bora, mistral, vent de bise, gallego— hot winds — simoon — harmattan— sirocco — saJano 121-129 LESSON IV.— Permanent Winds: The trade-winds— how explained— important uses of trade-winds 130-135 Vm CONTENTS. LESSON V. — Pekiodic-al Wlxps : Monsoons— Etesian winds— land and sea hrcezes— llio zone of calma ,...., 1 35-139 LESSON YI.— IIuKKicANES : Tlie three hurricane regions 139 140 LESSON VIL-^MoiSTtJKB : When least in the atmosphere — when greatest — mists and fogs.. , 140-143 LESSON VIII. — Clouds : Cirrus or curlcloud— cumulus or stackencloud— stratus or fall- cloud — composite forms — height of clouds 143-146 LESSON IX. — Eain : Extraordinary showers — unequal distribution of rain — table showing the diminution of rain from the equator to the poles — increase in the annual number of the rainy days as we go from the equator explained — fall of rain the greatest near the coasts — and in mountainous districts — rainless regions — rainy seasons in the tropics . . 147-149 LESSON X. — Snow and Hail : Forms of snow crystals — limits of snow at the level of the sea— uses of snow— hail, how formed 150-153 LESSON XL — Climate : Meaning of the term — by what causes determined — tJie latitude of a country — elevation ahove the level of the sea — line of perpetual snow — climates of mountainous regions in the torrid zone — height above the sea of individual classes of vegetation— vegetable regions on Mount Etna — Teneriflfe 153-15T LESSON XII. — Climate {continued) : The nea?mess to, or remoteness of a country from the sea — why America has a colder climate than corresponding latitudes in the eastern hemisphere — the slope of a country, or the aspect it presents to the sun^s course — how observed in the Alps — the position and direction of mountain chains — the nature of the soil — the cultivation and improvement of a country^prevalent winds — anmial quantity of rain 158- 162 LESSON XIII.— Climate (continued) : When the greatest cold occurs— table of the cli- mates of different places — isothermal lines — hot regions — warm regions — temperate re- gions—cold regions— frozen regions 162-166 PART IV. ORGANIC EXISTENCE. LESSON L — Plants: Organic existence defined— wide distribution of plants — flight, heat, and moisture as affecting plants — number of species known — divisions of the vegetable kingdom — ages of trees 16S-1I1 LESSON II. — DisTKiBUTiON OP Plants : Indigenous and exotic plants — different regions inhabited by distinct species of plants — botanical provinces— diffusion of plants . . 171-175 LESSON III. — Food Plants : What plants man has selected for his food — arborescent food-plants — the food plants which prevail in the Old World — those which have their origin in the New World — barley, rye, oats — wheat, buckwheat — maize or Indian com, j-jee — olive, date-palm — banana — cocoa-nut palm — bread-fruit tree — potato — cassava — arrow root — sugar-cane — coffee — tea — the vine — fig— the cocoa or chocolate tree. 1T5-180 LESSON lY. — Animals : Number of species — four grand divisions — vertebrated animals how subdivided — mammalia — birds— reptiles — molluscous animals — articulated ani- mals—radiated animals 1S1-1S2 LESSON Y.— DiSTpaBijTiON of Animals : Diversity in the organizations of animals— pro- fusion of animal life in the torrid zone— insects of the torrid zone— reptiles, birds, and mammiferous quadrupeds of the torrid zone— animal tribes of the temperate and cold regions— adaptation of animals to different climates 182-185 CONTENTS. IX LESSON VI.— Zoological Eegions: DifiFerent regions inhabited by distinct species of animals, as well as plants — number of zoological regions — European region — African region— region of Soutliern Africa— of Madagascar — of India— of ttie Indian Arcliipel- ago — of New Guinea — of Australia — of North America — of South America 181-1S8 LESSON YII. — Max: Number of the human race — their wide diflfusion — man's capability of accommodating himself to a great diversity of circumstances 1SS-1S9 LESSON VIII. — Eaces of Mex : All mankind the offspring of common parents — classi- fications of mankind with reference to the color of the hair — with reference to the shape of the skull — the Caucasian race — the Mongolian race — the Ethiopic race — the American race— the Malay race 190-195 APPENDIX. CHIEF PRODUCTIONS OF THE EAETH AND THE COUNTRIES "WHEEE THEY AEE PRODUCED 197-199 EXPORTS OF COUNTRIES 199-201 TRADE ROUTES . 201-204 METALLIC PRODUCTIONS 204-211. LIST OF THE PEINCIPAL MOUNTAINS, WITH THEIE ELEVATIONS. 212-21T LIST OP THE PRINCIPAL RIVERS, WITH THEIR CHIEF TRIBUTA- RIES 218-221 TABLE OP TEMPERATURE 222-225 LIST OF MAPS I. The World, illustrating the Principal Features of the Land 6 Note— For the sake of greater clearness, the Co-tidal Lines are shown on this map rather than on the next, where the water portion is devoted to an illustration of the Oceanic Currents. n. " illustrating the Divisions and Movements of the Waters oftheGlohe 62 m. " illustrating the Geographical Distribution of some of the Principal Phenomena of Meteorology 122 rV". " showing the Geographical Distribution and Limits of Cultivation of some of the Principal Plants useful to Mankind 172 y. " showing the Geographical Distribution and Range of some of the Principal Members of the Animal King- dom 182 YI. illustrating the Productive Industry of various Countries, and exhibiting the Principal localities of Commerce and Navigation, Trade Routes, etc 196 NTRODUGTION. I'M HYSICAL Geography is a description of the general features of the earth's sur- face, the organized beings placed upon it, and the operations of the atmospheie by which it is uni- versally sunounded. It relates to the earth as it exists in a state of natuie, without regard to po- litical or aibitrary divisions, or to any of those changes or iin- piovements m the world which have been effected by man. 2. It may be divided into four parts, relating respectively to the following subjects : 1. The Land, or solid portion of the earth's \f« Questions.— \. What is Physical Geography? To what does it relate' many parts may it be divided ? Name the subjects to which they relate. 1 2. Into how 2 INTRODUCTION. surface ; 2. The Water, or liquid portion ; 3. The operations of the Atmosphere ; 4. Animal and Vegetable life. 3. The First Part describes the extent and distribution of the land ; the arrangement of the continental masses and islands ; the magnitude and direction of the great mountain systems ; and the situation and extent of the vast plains, upland and lowland, which constitute the most productive portions of the earth's sur- face. This part also relates to volcanoes, earthquakes, etc., in their relation to the character and aspect of the land portion of the earth. 4. The Second Part relates to the waters of the globe, whether salt or fresh ; the origin, course, fall, and termination of rivers ; the distribution and magnitude of lakes ; and the extent, depth, tidal and other movements of the oceanic waters. 5. The Third Part treats of the operations of the atmosphere which surrounds our globe. It describes the laws which set the winds in motion, and the causes which influence their direction and velocity ; it explains the phenomena of moisture, dew, rain, snow, and hail, and the various causes which are concerned in the regulation of climate. 6. The Fourth Part relates to organic existence, or the ani- mals and plants distributed over the globe. It describes the great natural divisions of plants, the agencies which contribute to their diffusion, the food plants, and the regions where they are produced. It presents the orders of the animal kingdom, shows its diversity of organization, and its diffusion, and explains the zoological character of the different portions of the world. 7. The facts of Physical Geography are of a more permanent character than those which relate to the civil or political affairs of mankind. The, boundaries of nations are frequently changed, either by conquests or treat- ies ; new countries become peopled, and new states and territories organ- ized ; populous cities spring suddenly into existence ; and the arts of civili- zation are rapidly carried to distant quarters of the earth. The varying condition of countries with respect to population, internal improvements, boundary lines, etc., is such as to require a constant correction of maps and statistical works, in order to make them correct exponents of political affairs. QxiestionK.—Z. What does the first part describe ? To what does it also relate ? 4. To what does the second part relate ? 5. Of what does the third part treat ? What does it de- scribe ? 6. To what does the fourth part relate ? What does it describe ? 7. What is said of the facts of Physical Geography ? Illustrate. Varying condition of countries ? INTKODUCTION. 3 8. Such fluctuations do not belong to the science of Physical Geography. The grand and majestic features which God has impressed on the face of our globe — its continents and oceans — its mountains, valleys, rivers, and lakes, - remain now, with all their prominent characteristics, very nearly the same as they have existed for centuries past. 9. It is true that natural agencies are at work, changing to a limited ex- tent the face of nature. Volcanic action has rent the crust of the earth in numerous places, raising some portions and depressing others ; some rivers have worked new channels, and formed extensive deltas at their mouths ; and. as in Holland, vast areas of land have been rescued from the ocean by embankments and artificial modes of drainage. These and other alterations, considerable as they may appear, are comparatively unimportant as regards the world at large, and scarcely serve to qualify the remark, that the phys- ical aspect of the earth has not greatly changed in modern times. 10. From what is here observed it must not be inferred that the earth has not been the scene of mighty convulsions. An examination of its sur- face shows that at very early periods most important changes successively took place. To explain those changes, and the causes which have led to the present state or condition of the earth, belongs properly to the science of Geology. 11. Physical Geography explains many interesting facts of Civil Geog- raphy. It shows where nature has provided for the growth of cities, the peopling of states, the construction of railroads, canals, and other works of internal improvement ; it points out what courses on the ocean the mariner must pursue in order to avail himself of its favoring winds and currents ; and it explains what pursuits are best adapted to the people of different countries. The influence of mountains, rivers, seas, climate, and natural productions on the industry of people and the progress of nations is so great, that it is scarcely possible for one to possess a thorough knowledge of gen- eral geography, without first understanding those facts which Physical Geography describes. Questions. — 8. Do such fluctuations belong to the science ef Physical Geography? 9 How :ire certain changes of the earth's sur'ai^e produced? AVhnt is observed of these al- terations? 10. "What does an examination of the earth's surface show ? "What belongs to the science of Geology ? 11. "Why is a kuowledge of Physical Geography important? PART I. THE LAND. I LESSON I. EXTENT AND DISTRIBUTION. HE surface of the earth con- sists of unequal portions of land and water. It has been esti- mated to contain about 196,500,- I 000 English square miles. Of [this area, the dry land is sup- f posed to occupy about 51,000,- 000 of square miles. Hence it will be seen the fluid portion predominates over the solid in the ratio of about 285 to 100. The extent of each division, however, can not be exactly ascer- tained, owing to the north and south polar regions not having been fully explored. 13. There is but little regularity in the arrangement of the land upon the globe. In some parts the coast is indented by deep bays and gidfs, in others the land projects into the ocean in capes and promontories, while the islands are scatteied throughout the ocean, either singly or in irregular groups. 14. The distribution of the land is very unequal, — ^by far the greater portion being in the northern hemisphere. It has been calculated that there is about three times as much land north of the equator as south of it, and about two and a half times as much in the eastern as in the western hemisphere. Questions. — 12. Of what does the surface of the earth consist ? How many square miles does it contain? Square miles of the land? In what proportion does the fluid portion predominate over the solid ? Why can not the extent of each division be exactly ascer- tained ? 13. What is said of the arrangement of the land ? Illustrate. 14. What is said of the distribution of the land ? Which hemisphere contains the greater portion, the north- ern or southern ? How much more land is there in the northern than in the southern hem ■ isphcre? In the eastern than in the western ? EXTENT AND DISTRIBUTION OF THE LAND. Its distribution through the diflerent zones is as follows : Northern HEiiiepnEEE. Sq. Miles. SouTiiiii>f Hemisphere. Sq. Miles. Arctic Zone 2,792,000 Temperate Zone 24,488,000 Torrid Zone 9,949,000 Total 37,229,000 Antarctic Zone Unknown. Temperate Zone 3,306,000 Torrid Zone 10,466,000 Total 13,771,000 Joutliern Heraispber Northern Hemisplaere. 15. The unequal distribution of the land may be most strik- ingly seen from an inspection of a map of the hemispheres, projected upon the plain of the horizon of London. The hemi- sphere, in which that city occupies the center, inchides nearly all the land on the globe, while the other is almost covered with water. One may therefore be termed the continental or land hemisphere, and the other the oceanic or water hemisphere "Water Hemisphere. Land Hemisphere. Questions.— ].5. Ilnw may the unequal distribution of the land be most striiiingly seen ' Which hemisphere include^ nearly all the land ? How termed ? O CONTINENTS. LESSON IL CONTINENTS. 16. There are two continents, — the Eastern, which includes Europe, Asia, and Africa, and the Western Continent, or New World, which includes North and South America. The Eastern Continent is styled the Old World, from its being the only one known to* Europeans previously to the close of the fifteenth century. The terms eastern and western refer to the meridian of the Ferro Isles, from which longitude was formerly reckoned. 17. The Western Continent is about 8,700 miles in length from north to south. The greatest breadth of the continent is about 3,250 miles, and its least breadth, in the center, across the the Isthmus of Panama, about 30 miles. 18. North America is the northern portion of the Western Continent. Its greatest length from north to south is about 5,600 miles, and its greatest breadth about 3,100 miles. It con- tains an area of about 8,600,000 square miles. The main body of the continent may be included within a triangle, whose base extends along the northern shores and whose .vertical angle is in Mexico. 19. The eastern side of North America is penetrated by branches of the ocean, and consequently presents several penin- sulas, and the western projects the long peninsula of California. These indented shores, which give to the continent a coast-line of 24,500 miles, or 1 mile to every 350 square miles of surface, are, with numerous rivers and lakes, the means by which civili- zation and commerce have been extended, and are now rapidly extending into the interior. 20. Among the numerous indentations of the Atlantic coast south of Labrador, are the Gulf of St. Lawrence, Bay of Fundy, Quest/ions. — 16. How many continents are there, and what countries do they respectively include? Why is the Eastern Continent styled the Old World? To what do the lerma Eastern and Western refer? 17. Length of the Western Continent? Greatest breadth? Least breadth? 18. Length and breadth of North America? Area? General form of the continent? 19. What is the character of the coast-line? Extent of coast-line? 20. Principal indentations of the Atlantic coast south of Labrador ? 'Dte Uciht <^^lirTe^L^l\.e.&cros■sing the. water a3~e,Q,o-\iAzX\xa&%. and. Lhe Romcurv WwmeircLls atlached., represent tfieJTour ofhigh -iv cuter, az Mew ScFuUMo on along their < K \ Sc a in, the .7e>>.-.9 Office of the Vistricc Court erf the U=n.it:aLSU •—Jw.Smj&iei-n Bijrtricb: C O N T I N E N T S , 7 Passamaquoddy Bay, Penobscot Bay, Massachusetts Bay, Cape Cod Bay, Buzzards Bay, Narragansett Bay, New York Bay, Raritan Bay, Delaware Bay, Chesapeake Bay, Albemarle Sound, Pamlico Sound, Gulf of Mexico, Bay of Honduras, etc. 21. South America is the smaller of the two divisions of the Western Continent. Its greatest length from north to south is about 4,600 miles, and its greatest breath from east to west about 3,000 miles ; its area is about 6,420,000 square miles. Its form is triangular. Its unbroken coast-line of 14,500 miles in extent, gives only a mile of sea-coast for every 420 square miles of sur- face, and presents few bays or even harbors. 22. The slow progress of civilization in South America has been attributed in a great measure to the want of bays and gulfs extending inland and af- fording maritime advantages to the interior regions. This disadvantage of unbroken coast-line is partly counterbalanced by the vast navigable streams of the Orinoco, Amazon, La Plata, and their branches. LESSON III. CONTINENTS — [continued). 23. The Eastern Continent is the largest mass of land upon the globe. It extends for about 10,000 miles from east to west, and about 8,000 from north to south. It contains an area of about 33,000,000 of square miles, or about two and a fourth times as many as the Western Continent. 24. Europe is the smallest of the five grand divisions. Its greatest length from Cape St. Vincent, in the southwest, to the Gulf of Kara, in the northeast, is about 3,500 miles ; its great- est breadth, from North Cape to Cape Matapan, is about 2,400 miles. The area of its surface, including the islands, amounts to about 3,500,000 square miles. 25. Europe is indented by numerous bays and seas on its western and southern sides, in consequence of which the coast- Questions. — 21. What is said of South America? Greatest length ? Breadth? Area? Form ? Extent of coast-line ? 22. Slow progress of civilization in South America ? What compensation is there for its unbroken coast-line ? 23. What is said of the Eastern Con- tinent? Its length and breadth? Area? 24. What is the comparative size of Europe? Its length and breadth ? Area ? 25. "What is said of its coast indentation ? Extent of sea- coast ? What is said of its peninsular character ? What large peninsulas does it embrace ? 8 CONTINENTS. line is of great extent, and in proportion larger than that of any other of the grand divisions. Its line of shores extends 17,000 miles ; it therefore, enjoys a mile of coast-line for every 156 square miles of surface, thus possessing great facilities for commercial enterprise. Europe is essentially the region of peninsular for- mations : it embraces the Scandinavian Peninsula (Norway and Sweden) ; the Peninsula of Denmark ; the Peninsula of Spain and Portugal; and the Peninsulas of Italy and Greece. 26. Asia is the largest of the grand divisions of the earth. Its greatest length from east to west is about 5,600 miles, and its greatest breadth from north to south about 5,300 miles. It contains an area of about 17,500,000 square miles, or consid- erably more than is contained in both North and South America. It has a coast-line of 30,800 miles, and excluding the Arctic Ocean, which is scarcely navigable, there will be only 1 mile of sea-coast for every 459 miles of surface. 27. Africa, like South America, is a vast peninsula, being en- tirely surrounded by the waters of the ocean, except at the Isthmus of Suez, by which it is connected to Asia. Its greatest length from north to south is about 5,600 miles, and its greatest breadth from east to west about 4,700 miles. Its area is about 11,300,000 square miles. In consequence of its peculiar form, with no considerable peninsulas or sea indentations, its coast-line is only 14,000 miles, or only 1 mile of sea-coast for every 623 square miles of surface. On this account it is the most inacces^ sible, least civilized, and least known to civilized nations. 28. The following table exhibits the superficial extent of each continent in English square miles, together with the length of coast-line possessed by each (in English miles), and the proportion which the latter of these measures bears to the former : Surface. Coast-line. Square Miles of Surface for 1 Mile of Coast North America 8,600,000 6,420,000 3,500,000 17,500,000 11,300,000 24,500 • 14,500 17,000 30,800 14,000 350 420 156 459 623 South America Europe Asia Africa ^?ie5^ face of upward of 1,000 square miles, and form a r • r ±-\ • View of a Glacier sea ot ice irom the in- exhaustible reservoirs of which some of the principal European rivers are supplied 130. Glaciers are not composed of solid ice, but consist of a mixture of ice, snow, and water. They owe their origin to the accumulation of the snow which falls from the sides of the mountains, and becomes only partially melted during the short summer of these elevated regions. 131. It is a remarkable fact respecting glaciers that they have an onward flow like rivers. The movement is very slow, not amounting usually to more than a foot in twenty-four hours. Like that of rivers, it is most rapid in the center, and slower at the sides and bottom on account of friction. M. Agassiz obtain- ed the following results, in 1841 and 1842, upon this point : Annual Motion. Finster Aar. — Stake nearest the center of the glacier . . . 269 feet. " Stake nearest the side of the glacier 160 " Lauter Aar. — Stake nearest the center 245 " " Stake nearest the side 125 " 132. The rate of motion depends upon the seasons ; thawing Quefitio7i8. — 130. Of what do glaciers consist? Their origin? 131. Eemarkable fact jespecting glaciers ? Eate of movement ? In what part most rapid ? Kesults obtained by Agassiz? 132. Upon what does the rate of motion depend? State the movement of the Mer de Glace at diflFerent seasons. 4:2 GLACIERS. weather, and a wet state of the ice, conducing to its advance- ment, while cold, whether sudden or prolonged, checks its pro- gress. The ice near the shore of the Mer de Glace (Sea of Ice), near Chamouni, was found to moye as follows : From June 29 to Sept. 28 132 feet. " Sept. 28 to Dec. 12 70 " " Dec. 12 to Feb. 17 76 " " Feb. 17 to April 4 66 " ^ " April 4 to Jime 8 88 " 133. Glaciers, originating in the regions of eternal frost, de- scend far below the line of perpetual snow. The lowest limit to which perpetual snow extends downward in the Swiss Alps is about 8,500 feet above the level of the sea. The lower gla- cier of the Aar descends more than 1,500 feet below the snow- line, while others descend 4,000 or 5,000 below the region of perpetual snow and ice, as, for examples, the glaciers of the Upper and Lower Grindelwald. 134. The appearance of glaciers is thus described by Lyell : " When they descend steep slopes and precipices, or are forced through narrow gorges, the ice is broken up, and assumes the most fantastic and picturesque forms, with lofty peaks and pinnacles, projecting above the gen- eral level. These snow-white masses are often relieved by a dark back- ground of pines, as in the vaUey of Chamouni ; and are not only surrounded with abundance of the wild rhododendron in full flower, but encroach still lower into the region of cultivation, and trespass on fields where the tobacco- plant is flourishing by the side of the peasant's hut." 135. Snow mountains and glaciers, though devoid of vegeta- tion in the upper regions, and presenting a picture of desolation on a scale of magnificence which makes it awful, are yet a strik- ing instance of the truth that nothing was made in vain. " Herds of chamois are at home amid the frozen heights of the Alps; the Thibetian cow can only bear the climate of the valleys in winter ; nor can man pronounce such districts barren, though cheerless in appearance, and never intended for his residence. They minister to his comfort, happiness, and even luxury, as the inexhaustible sources of those streams, which in summer, when other waters are evaporated and dried up, roll on through the plains, fountains of fertility and plenty. The Rhone, Ehine, Po, Reuss, Questions. — 133. Do glaciers descend below the limit of perpetual snow ? What is the lowest limit of perpetual snow on the Alps ? To what distance below this line are glaciers known to descend? 134. Appearance of glaciers as described by Lyell ? 135. What re- mark is made of snow mountains and glaciers ? How illustrated ? SNOW MOUNTAINS AND AVALANCHES. 43 Ticino, Aar, Adige, Inn, and Drave, respectively flowing to the German Ocean, Mediterranean, Adriatic, and Black seas, are fed from the snows and glaciers of the Alps." — Rev. Thomas Milner. LESSON XII. SNOW MOUNTAINS AND AVALANCHES. 136. The polar regions are covered with fields of perpetual ice aad snow. In the temperate and torrid zones everlasting frosts prevail only on the high lands. The elevation at which perpetyal snow begins in these zones varies with the latitude. It is 16,000 feet from the level of the sea at the equator; 9,000 feet near latitude 45° ; 5,000 feet at latitude 60° ; 1,000 feet at latitude 70° ; and about latitude 80° the line of perpetual snow comes down to the sea-level 137. The principal localities of permanent snow in the torrid and temperate zones are Iceland, Norway, the Alps, and Pyre- nees, in Europe ; the Caucasus, Himalaya, Kuen4un, and Altai mountains, in Asia ; the range of the Greater Atlas, m Africa ; and the Andes, in America. The mountains of South Australia, and Mount Egmont, in New Zealand, are snow mountains. The Himalaya derives its name, "the dwellmg of snow," from the vast surface occupied by it. 138. The summits of these lofty mountains accumulate enor- mous masses of snow, which are often precipitated into the sur- rounding valleys, producing terrible disasters. These descend- ing bodies increase in volume by the dislodgment of other masses, and fall with tremendous velocity and violence, uprooting trees, overwhelming houses and villages, and stopping the flow of streams and rivers. 139. Such falls are very common in Switzerland, where they Questions.— IdQ. Polar regions how covered ? Where only do everlasting frosts prevail in the temperate and torrid zones ? Elevation at which perpetual snow begins at the equator ? At the 45° ? 60° ? 70° ? Snow-line at the 80° ? 137. Principal localities of permanent snow in the torrid and temperate zones? 138. Accumulation of snow masses ? Where precipitated? Destructive effects? 139. Where are such falls very common ? What are they called in Switzerland ? In Norway ? What four kinds are noticed ? 4:4 SNOW MOUNTAINS AND AVALANCHES. are called avalanches* or lavanges. In Norway they are called the snee-fond. Four kinds are noticed, drift, sliding, creeping, and ice avalanches. 140. (1.) A drift avalanche is the fall of the drifts and other accumulations of snow from the upper regions. During calm weather snow collects in enormous volumes on the declivities, where it remains until the wind forces it from its resting-place, and it rushes down into the lower regions. In its progress it forces off other masses, which augment its size, and becoming thus enlarged, it descends with constantly accelerated energy, occasioning as much damage by the whirlwind rush of the air, as by the direct attack of the snow. 141. (2.) A sliding avalanche is a descent of snow jnasses which have become loosened by the heat of the earth. Ava- lanches of this class occur in spring, and commonly origmate in the middle region of mountains. (3.) Creeping avalanches orig- inate in a similar manner, but on less steep declivities. (4.) Ice avalanches are parts of a glacier, detached by the summer heat, or broken off by their own weight, on the extremity projecting over the edge of a precipice. 142. The following interesting description of avalanches is by the Rev. Thomas Milner : " On descending the Sheideck into the valley of Grindelwald, canton of Berne, the extraordinary effects of an ice avalanche that fell some years ago are observable. The ground is entirely cleared ; the trees have been swept away like reeds ; an area of at least a mile and a half square is strewn with stones and stumps ; a fine forest growing on each side of the area, which was untouched by the Mling mass. 143. "A similar avalanche descended near the village of Kanda, in one of the valleys of the Valais canton, in 1819. It covered with ice, rubbish, and fragments of rock an area of 2,400 feet in length, by 1,000 feet wide, to the depth of 150 feet. It fell on an uninhabited spot, but the adjoining village was destroyed by the tremendous rush of the compressed air conse- quent upon the descent of such an enormous mass, about 9,000 feet. Beams of houses were carried nearly a mile into the forest, and the massive stone steeple of the church was snapped asunder. 144. " In the year 1749, a creeping avalanche of snow descended in the Questionsi.-Ua. Describe the drift avalanches. 141. The sliding avalanches,— the creep- .ing avalanches, — the ice avalanches. * Avalanche, from the French amUv, to descend. VOLCANOES. 45 valley of Tawich, in the canton of the Grisons, and buried the whole village of Bueras, pushing it at the same time from its site. The catastrophe oc- curred in the night, and so stealthily, that it was unperceived by the inhab- itants, who, on awaking in the morning, were surprised at the prolonged darkness. Sixty out of a hundred persons were dug out alive, obtaining a sufficient supply of air through the interstices of the snow to sustain life. 145. " In 1838 the secluded hospice of the Grimsel was the scene of a re- markable preservation. The hospice, remote from any human habitation, well known to pilgrims in the Oberland, is only tenanted by a single servant with provisions and dogs, from November to March. In the latter month, a great storm occurred, and the snow fell incessantly for four days. While occupied with his art of wood-carving, the solitary was alarmed by a myste- rious sound in the evening, like the cry of a human being in distress ; but no benighted wayfarer appeared on sallying forth with his dog. The sound re- curred again. It was one of those signals which frequently precede a grand catastrophe in the Alps — the noise of a mass disturbed and quivering. Sud- denly the impression seized him to retreat into the hospice. He went ac- cordingly into an inner room, and began to pray, when the avalanche came thundering down, crushing every apartment but the one which was then sanctified by prayer. Its inmate with his dog succeeded in working his way through the snow, and reached Meyringen in safety, firmly regarding his preservation as an answer to his prayer ; and to every pious mind it will verify the sacred declaration, ' He that dwelleth in the secret place of the Most High shall abide under the shadow of the Almighty.' " LESSON XIII. VOLCANOES. 146. The term Volcano (derived from Vulcanus, the name the ancient Romans gave to their imaginary god of fire) is ap- plied to those mountains which send forth, from their summits or sides, flame, smoke, ashes, and streams of melted matter called lava : it is also applied to mountains having eruptions of mud only, and which are hence called Mud Volcanoes. 147. Volcanoes are generally of a conical shape, with a hol- low at their summit, called the crater, or cup, the sides of which are sometimes entire, like the walls of a circus, but more com- Questions. — ^146. From What is the term volcano derived ? To what is it applied ? 147. General shape of volcanoes ? What is the opening at the summit called ? Its appearance ? The general appearance of the bottom or floor of craters ? 46 VOLCANOES. monly rent. The bottom or floor of craters usually presents a series of ashy cones, with cracks and fissures, through which jets of smoke, steam, and flame issue at the most tranquil in- tervals. Volcano of OrizalDa. 148. -Volcanoes are either continuously active, or intermittent, or extinct. Of the former class is Stromboli, in the Mediter- ranean — a comparatively lowly mound, 2,175 feet high. It has been uninterruptedly active from the dawn of authentic history, a permanent fiery beacon to the sailors of the adjoining seas, but very rarely violent. Etna, Vesuvius, and Cotopaxi have varying intervals of rest, in some instances amounting to centuries. Extinct volcanoes are those whose activity has for ages been suspended. A volcano of this class may be found on the isle of Palma, one of the Canaries. 149. An explosion commonly begins by a dense volume of smoke issuing from the crater, mixed with aqueous vapor and gases ; hen masses of rock and melted matter are thrown out with great violence, after which lava begins to flow, and the whole terminates with a shower of ashes from the crater. The Qiiestions. — 148. The throe states of volcanoes? Stromboli ? Examples of intermittent volcanoes? What are extinct volcanoes? Instance. 149. How does an explosion com- monly begin ? What substances follow ? What finally succeeds ? Which of the ejected substances is often the most destructive ? VOLCANIC REGIONS. 47 as"hes are often the njost destructive, as will be seen by the ac- counts of volcanoes in a succeeding lesson. 150. There are supposed to be about 300 volcanoes on the earth, about two thirds of which are situated in islands, the re- mainder being confined to the continents. Their distribution is stated in the following table : On Continents. In Islands. Total. Europe 4 20 24 Asia 17 29 46 Africa 2 9 11 America 86 28 114 Oceanica — 108 108 109 194 303 LESSON XIV. VOLCANIC REGIONS.* ^ 151. Volcanic Regions of the Andes. — The Andes of South America embrace three extensive volcanic regions. The first is known as the Chilean range, the second as the Peruvian, and the third as the volcanic region of Quito. These regions are separated by extensive tracts, in which no volcanic action has been known to occur since the discovery of America. 152. The volcanic range of Chile embraces the most southern line of active vents. It extends from latitude 43° 28' south, or from a point on a range with the island of Chiloe to Coquimbo, in latitude 30° south — a distance of nearly fourteen degrees of latitude. This region is remarkable for containing the highest known volcano in the world, that of Aconcagua (23,944 feet). To the north is a space of more than eight degrees of latitude, in which no recent volcanic eruptions have been observed. Question.'^. — 150. Number of volcanoes ? How many of these are situated in islands ? On continents ? What number belongs to Europe ? To Asia ? To Africa ? To America ? To Oceanica ? 151. Number of volcanic regions in the Andes ? By what names known? How are these regions separated ? 152. Volcanic range of Chile ? Between what parallels does it extend ? For what remarkable ? * The description of the volcanic regions contained in this lesson is derived principally from " LyeJl's Principles of Geology." 48 VOLCANIC KEGIONS. 153. Tho Peruvian line of volcanoes, the next in order, ex- tends a distance of about six degrees, from latitude 21° south to latitude 15° south. The volcano of Arequipa is situated in this district, with an elevation of more than 20,000 feet. Between the Peruvian volcanoes and {hose of Quito another space inter- venes, of no less than fourteen degrees of latitude, said to be free from volcanic action so far as yet known. 154. The volcanoes of Quito begin about 100 geographical miles south of the equator, and continue for about 130 miles north of the line. The most elevated of their summits are those of Cotopaxi and Antisana, — the former having an altitude of 18,858 feet, and the latter 19,126 feet. To the north o if the volcanic region of Quito there occurs another undisturbed in- terval of more than six degrees, after which we arrive at the volcanoes of Guatemala, in Central America, north of the Isth- mus of Panama. 155. The volcanoes of South America rise in many instances to vast elevations above the level of the sea, several examples of which have been previously mentioned. Those of Peru rise from a lofty platform to elevations varying from 17,000 to 20,000 feet. Of those which have recently been in a state of activity, the most lofty is Cotopaxi : its eruptions have been more fre- quent and destructive than those of any other mountain. It is a perfect cone, usually covered with an enormous bed of snow, which has, however, been sometimes melted suddenly by an eruption; as in January, 1803, for example, when the snows were dissolved in one night. 156. Frequent deluges are caused in the Andes by the sudden melting of great masses of snow, and by the rending open, dur- ing earthquakes, of subterranean cavities filled with water. In these inundations fine volcanic sand, loose stones, and other ma- terials, which the water meets with in its descent, are swept away, and a vast quantity of mud, called " moya," is thus formed and carried down into the lower regions. In 1797, valleys, a Questions.— 15S. Situation and extent of the Peruvian line of volcanoes ? Yolcano of Are- quipa ? What non-volcanic region to the north ? 154. Situation and extent of the volcanof 3 of Quito? Most elevated summits? What region extends farther north? 155. What is sai-»■ JS. Ci^Ztcm &Cc-t. iSr^-xus t'm-A/rSin.xher^Ui,!',. The iSsrvo^vrs show t/ie ^eiiei^al direction of the. (kuvents: those with points at cacli end hidicate cuirejvts which oMcrti-atc in direction with the seasoru.-. The Dotted lines luport the laTui.Tnark the boundai-ie.* hetwcen. tlie diffei-ervt Eiver-Baniiw. tance 1 2 1 tan. 131 640 6.330 Onefla IJeiul Sea. ("airpicji. .!>>v.—22&. Give particulars of the Falls of St. Antbony. 70 EIVEES Falls of Montmorenci, 227. Among the other ' noted falls in America are those of the Missouri, 500 miles from its source, a succession of rapids and cataracts, 26, 47, and 87 ft. .1 in perpendicular height ; | the rapids of St. Law- rence, above Montreal, | ^tending about 9 miles ; | the Great and Little Falls of the Potomac, in Mary- land ; the Falls of Mont- morenci, near Quebec, ^ which descend 240 feet ; in an unbroken sheet ; and the Cataract of Tequen- : dama, in the environs of | Santa Fe de Bogota, a magnificent fall of 574 ft. , 228. The Great Falls of the Missouri are the grandest in all! North America, those of Niagara excepted ; and although the latter exceed the former with respect to volume of water, depth, of descent, and awful grandeur, yet the former are far more di-} versified and beautiful. These falls are within sixty geograph-| ical miles of the easternmost range of the Rocky Mountains, j They were discovered by Captain Lewis while engaged in ex-j ploring the Missouri. Hearing a sound like that of a fall of water, he proceeded in the direction of it. " As he advanced, a spray arose above the plain like a column of smoke, and vanish- 1 ed in an instant. Toward this point he directed his steps ; and having traveled seven miles after first hearing the sound, he reached the falls about mid-day. The hills as he approached were difficult of access, and 200 feet high. Down these he hur-^ ried with impatience, and seating himself o'h some rocks underj the center of the falls, enjoyed the sublime spectacle of this, Questions.— 221 . Other noted falls in America? 228. The Great Falls Give an account of its discovery. I the Missouri ? KIVEKS. 71 stupendous cataract, which since the creation has been lavishing its magnificence on the desert, unknown to civilization." 229. The principal water- -i_-"^^:^ falls of the Eastern Conti- nent are Terni, Italy, a fall of the Velino, of 300 feet, usually regarded as the finest European cataract ; Staubach, near Lauterbrun- nen, in Switzerland, a per- pendicular descent of 800 feet ; Rhinefall, near Schaff- hausen, a fall of the river Rhine in three distinct branches over a precipice upwards of 80 feet ' high ; Reichenbach, canton of Bern, a series of six falls, amounting to 1,000 feet ; Ache, a small river of Ba- ReicheniDac-h. varia, descending in five falls 2,000 feet; Evanson, a torrent of Mount Rosa, 1,100 feet; Cauvery, southern India, two grand falls near Seringapatam, 810 feet; Girsupah, near a town of that name in the western Ghauts, a single fall of a considerable stream, 872 feet. LESSON V RIVERS — [continued) . 230. The termination of rivers is commonly by a single mouth, as in the instances of the St. Lawrence and the Hudson ; but many streams, flowing through alluvial regions, carry along sedimentary accumulations which they deposit at their mouths, producing formations of land, and dividing the main stream into Qii£Stions.—22^. Give the particulars of the following falls and rapids: Terni, Staubach, Ehinefall, Eeichenbach. Ache, Evanson, Cauvery, Girsupah. 230. Termination of rirers? Sedimentary accumulations? Deltas? 72 RIVEKS. branches. Such formations are called deltas, from their corre- spondence to the shape of the Greek letter A (delta). 231. The delta of the Mis- sissippi consists of a long, nar- row tongue of land protruding for 50 miles into the Gulf of Mexico, at the end of which are numerous channels of dis- charge. This extensive for- mation has been produced by the deposit of the sedimentary matter brought down by that mighty stream. The rate of Delta cf the Mississippi permanent advance of the new land has been very slow, not exceeding, it is supposed, one mile in a century.* 232. It has been calculated that the mean annual amount of solid matter which the water of the Mississippi contains is about T2V5 of i^s weight, and that it is equal to about 3 oVo ^^ its vol- ume. It has also been estimated that the quantity of solid mat- ter annually brought down by the river is 3,702,758,400 cubic feet, an amount which would cover over eleven miles square one foot deep. 233. The waters of the Ganges contam a much greater proportion of sedimentary matter, particu- larly during the season of the rains, which lasts about four months. The average quantity of solid matter suspended in the water during such times was by weight 4 ^8^^ P^^t ' ^^^ t^® solid Delta of the Gariges. ^^^^^^ discharged is ^l^th part in bulk, or 577 cubic feet per second. The total annual amount Question^.— 2'&\. Delta of the Mississippi? The rate of its formation ? 232. Proportion of the sedimentary matter? Amount annually brought down ? 233. Sedimentary matter in the Ganges ? Total annual amount ? The Hoang-Ho ? * Sir Charles Lyell. EIVEKS. 73 of mud discharged is estimated at 6,368,077,440 cubic feet, a mass equal in weight and bulk, it has been calculated, to eighty- two of the great pyramids of Egypt. The Hoang-Ho, which traverses the great alluvial plain of China, is supposed to bring down in one hour 2,000,000 cubic feet of earth, which so thick- ens and colors the ocean by its discharges as to originate the name of the Yellow Sea. 234. Rivers are grouped into two grand classes, the oceanic and the continental. Oceanic rivers are those which flow direct into the ocean, or into waters communicating with it. They form four distinct systems, belonging respectively to the Arctic, Atlantic, Pacific, and Indian oceans. I. System of the Arctic Ocean. Length in Eivers Course. Termination. English Miles. Lena Eastern Siberia Arctic Ocean 2,400 Olenek Northern Siberia Ditto 1,150 Yenesei Central Siberia Ditto 2,900 Obi Western Siberia Gulf of Obi 2,530 Petchora Northern Russia Arctic Ocean 695 Dwina Ditto White Sea 760 Mackenzie British America Arctic Ocean 2,160 n. System of the Atlantic Ocean. Neva Northern Russia Gulf of Finland. . . 46 Vistula Poland, Prussia Baltic Sea 630 Elbe Germany German Ocean 690 Rhine Switzerland and Germany. Ditto 760 Loire France Bay of Biscay 570 Rhone Switzerland, France Mediterranean 490 Danube Austrian Empire, Turkey .Black Sea 1,630 Dnieper Southern Russia Ditto 1,200 Don Ditto Ditto 1 ,100 Nile (Blue N.) Abyssinia, Nubia, Egypt.. Mediterranean 2,600 Senegal Western Africa Atlantic Ocean 900 Niger.. Ditto Gulf of Guinea ... 2,300 Gariep Southern Africa Atlantic Ocean 1,000 Saskatchewan British America .Hudson's Bay 1,920 St. Lawrence Ditto Atlantic Ocean 2,070 Mississippi-Missouri . Central North America .. .Gulf of Mexico 4,100 Rio-del-Norte Mexico Ditto 1,400 Questions.— 2Z^. Eivers, how grouped ? Oceanic rivers ? Systems ? Name the princi- pal rivers belonging to the system of the Arctic Ocean. Atlantic Ocean. Pacific Ocean. Indian Ocean. 4 Ti DIVERS. Length in Bivers. Course. Tennination. English ^ Miles. Magdalena New Granada Caribbean Sea 860 Orinoco Venezuela Atlantic Ocean 1,200 Amazon Brazil Ditto 3,900 Araguay Ditto Ditto 1,300 St. Francisco Ditto Ditto 1,500 Plata Ditto Ditto 2,350 m. System of the Pacific Ocean. Amour Eastern Asia Sea of Okhotsk 2,300 Hoang-Ho China Yellow Sea 2,600 Yang-tse-Kiang Ditto Ditto 3,200 Si-Kiang Ditto China Sea 1,110 Meinam Siam Gulf of Siam 900 Cambodia Tibet, Cochin China China Sea 2,000 Columbia Oregon Pacific Ocean 750 Colorado Utah, New Mexico Gulf of California. . 900 rV. System of the Indian Ocean. Euphrates Western Asia Persian Gulf 1,600 Tigris Ditto Ditto 980 Indus Northern India Arabian Sea 1,700 Ganges Ditto Bay ofBengal 1,460 Brahmapootra Tibet, Assam ..Ditto 2,000 Irawaddy Tibet, Birman Empire Ditto. 1,200 Murray South Australia Encounter Bay 1,000 235. Continental rivers are those which are confined exclu- sively to the continents, and discharge themselves into completely- insulated lakes, or are lost in sands, deserts, or swamps. The principal continental rivers are stated in the following table : Eivers. Course. Termination. Volga European Russia Caspian. Kour Georgia Ditto. Terek Circassia Ditto. , Ural European and Asiatic Eussia. Ditto. i Amoo, or Jihon (ancient Oxus) Turkestan Lake Aral. Sir, or Sihoon Ditto Ditto. | Helmund Afghanistan Lake Zurrah. ; Yarkand Central Asia Lake Lopnor. ; Many streams in Central Asia j terminate in insulated lakes, [ or are lost in desert sands. . Question.— 12&. Continental rivers ? Name the principal continental rivers, the eoun- i iriea through which they flow, and their places of termination. KIVEKS, T5 Elvers. Course. Termination. Jordan Palestine Dead Sea. Streams north of the African Sahara, lost in sands Rio Grande Mexico „ . . . Lake Parras. Desaguadero Bolivia Lakes and Swamps. Humboldt's Utah Territory Lake. Bear Ditto Great Salt Lake. Many other streams in Utah Territory are lost in sands, marshes, or lakes. 236. The magnitude of rivers depends upon the area of their basins, the rain-producing character of the climate, and the ar- rangement of the surrounding mountains, with reference to the prevailing winds. Lieut. Maury thus accounts for the vast rivers of the South American continent : " The northeast and southeast trade-winds, as they come across the Atlantic, filled with moist- ure, go full charged into the interior, dropping it in showers as they go, until they reach the snow-capped summits of the Andes, where the last drop, which that very low temperature can wring from them, is deposited to melt and feed the sources of the Ama- zon and the La Plata, with their tributaries." 237. The proportional quantity of water discharged by some of the principal rivers has been estimated as follows : Thames 1 Rhine 13 Loire 10 Po 6 Elhe 8 Vistula 12 Danube 65 Dnieper 36 Don 38 Volga 80 Euphrates 60 Indus 133 Ganges 148 Yang-tse-Kiang . . . 258 Amour 166 Lena 125 Obi 179 Nile 250 St. Lawrence 112 Mississippi 338 Plata 490 Amazon 1,280 238. Many rivers are subject to periodical inundations. It is to the annual overflowings of the Nile that Egypt owes her fer- tility. The rise commences about the 21st of June, attains its greatest height near the middle of September, and gradually di- minishes to the time of the winter solstice. Both the Mississippi and the Missouri have annual floods during the spring months. Questions. — 236. Upon what does the magnitude of rivers depend ? The large rivers of South America ? 237. State the proportional quantity of water discharged by some of the principal rivers. 238. Inundations of rivers ? Overflowings of the Nile ? Of other rivers? 76. NOKTH AMERICAN KIVEKS. Among the other streams subject to overflow are the Orinoco, Amazon, Euphrates, Tigris, etc. 239. The following beautiful extract relates to the historic associations of rivers : " The rivers of the old world, while subordinate to those of the new in point of magnitude, have a historic and sacred interest in many instances wholly wanting to the latter. The Danube recalls the struggle of the an- cient civilization with overwhelming barbaric invasions; the Tiber revives the story of Roman greatness ; the Nile associates itself with the colossal power of the Pharaohs ; the Tigris and Euphrates are connected with the mighty dynasties of Assyria and Babylon, the captivity of God's chosen peo- ple, and that momentous hour when the hand of retributive justice unfolded the doom of monarch and of nation at a profane festivity of the royal house ; while the Jordan is imperishably linked with far more stupendous transac- tions : the miracle which divided its waters at the ingress of Israel into the land of promise ; and that voice from heaven which proclaimed the charac- ter of the Messiah at his baptism in the stream, placing his right to the universal homage of man, supported by the design of his mission, on the firm ground of his Divine nature : ' This is my beloved Son, in whom I am well pleased.'"* LESSON VI. THE RIVER SYSTEMS OF THE WESTERN CONTINENT. 240. In no portion of the world are rivers found upon so mag- nificent a scale as on the continent of North and South America. The magnitude of these streams is owing to a variety of causes, some of which have been described ; as the situation and direc- tion of the great mountain ranges, the extent of the river-basins, etc. : others will be explained in a subsequent part, which treats of wind, rain, etc. 241. North American Rivers. — The continent of North America may, with reference to its drainage, be divided into four grand divisions : (1) The Atlantic slope, or that part which ii> drained by the rivers tributary to the Atlantic Ocean ; (2) the Questions.— 239. What is said of the rivers of the old world ? Illustrate. 240 Magni- fude of the American rivers? To what owing? 241. How may the continent of North America be divided with reference to its drainage ? First division ? Second ? Third V ■Fourth ? * Eev. Thomas MUner. NOETH AMERICAN RIVERS. 77 Valley of the Mississippi, lying between the Rocky and Alle- ghany Mountains ; (3) the region to the west of the Rocky Mountains, the streams of which are tributary to the Pacific Ocean ; (4) the northern slope drained by streams tributary to Hudson's Bay and the Arctic Ocean. 242. The Mississippi is the largest of the North American rivers : it waters the southern half of the great plain, and brings to the sea the drainage of upward of a million of square miles. It rises in the small lake of Itasca, at an elevation of only 1,490 feet above the level of the sea, and flows in a southerly direction to its termination in the Gulf of Mexico, after a course of 2,400 miles. The Mississippi is navigable for 2,000 miles to the Falls of St= Anthony, which occur at a distance of about 400 miles below its source. 243. The Missouri has its origin in the Rocky Mountains, and runs for 2,500 miles in a southeasterly direction before it joins the Mississippi, making a total distance, from its source to its en- trance into the Gulf of Mexico, of more than 4,000 miles. It is navigable from the point where it unites with the Mississippi up to the base of the Rocky Mountains, where the Great Falls oc- cur (in latitude 46° 50^. 244. During the period of the annual floods, large tracts of the adjoining country are overflowed, and immense damage done to property. Artificial embankments, called levees, are constructed along the lower course of the Mississippi to prevent inundation ; but in seasons of high floods they are often broken through by the *force of the waters, forming what are known as crevases. About one fifth of the whole surface of the State of Louisiana is periodically overflowedo 245. The Ohio is, next to the Missouri, the most important of the tributaries of the Mississippi : it is formed by the junc- tion of the Monongahela and the Alleghany rivers, which unite their waters at Pittsburg, where the river becomes navigable. The Ohio, about 950 miles in length, and from four hundred yards t» upward of three quarters of a mile in breadth, flows Questions. — 242. The Mississippi? Its source, direction, and termination? How far navigable ? 243. The Missouri ? How far navigable ? 244. Floods ? Artificial embank- ments? 245. The Ohio? Its length, etc. ? Falls? 78 NORTH AMERICAN RIVERS, througn one of the most fertile portions of the Mississippi Valley. It has no fall, except a rocky rapid of 22^ feet descent at Louis- ville, around which a canal has been constructed sufficiently ca- pacious to admit steamboats, though not of the largest class, 246. Among the other prmcipal streams in the Yalley of the Mississippi are the following : the St. Peters, Iowa, Des Moines, St. Croix, Wisconsin, and Illinois rivers, tributaries to the Mis- sissippi above, and the Ohio, Arkansas, and Red rivers below, the junction of the Missouri ; the Yellow-stone, Platte, Kansas, and Osage rivers, tributaries to the Missouri ; and the Scioto, Miami, Wabash, Kanawha, Licking, Kentucky, Green, Cumberland and Tennessee rivers, tributaries to the Ohio. 247. The St. Lawrence is the second great river of the North American continent, and by far the largest of the streams drain- ing the Atlantic slope. Its channel from Lake Ontario to the sea is about 700 miles long, but (including the great chain of lakes from which it derives its waters) the whole length, from the mouth of the St. Lawrence to the western extremity of Lake Superior, is 1,880 miles. Above Montreal, rapids occur which interrupt its navigation. During four months of the year the navigation is completely stopped by the ice. 248. Of the other streams draining the Atlantic slope, the principal are the Connecticut (400 miles), the Hudson (325 miles), the Delaware (300 miles), the Susquehanna (450 miles), the Potomac (400 miles), the James (450 miles), the Roanoke (350 miles), the Pedee (350 miles), the Santee (350 miles), the Savannah (400 miles), and the Alatamaha (400 miles), — all of which flow into the Atlantic Ocean. The Appalachicola (600 miles) and the Mobile, further to the westward, flow into the Gulf of Mexico. Most of these rivers are navigable for a con- siderable distance inland, and the Hudson (at the mouth of which stands the city of New York) can be ascended by the largest merchant ships 120 miles, and steamers nearly 160 miles. Questions.— 146. Tributaries to the Mississippi above the junction of the Missouri ? Be- low the junction of the Missouri? Tributaries to the Missouri ? To the Ohio? 247. The St. Lawrence? Its length from Lake Ontario? Its whole length including the lakes? Rapids ? Ice ? 248. Other streams draining the Atlantic slope ? Their navigability ? The Hudson, how far navigable for the largest ships ? Fop steamers ? NOKTH AMERICAN KIYEKS. 79 249. The principal rivers draining the region to the west of the Rocky Mountains — forming the third division — are the Fraser (600 miles), Oregon, or Columbia (750 miles), Sacramento (420 miles), and the Colorado (840 miles). Columbia, the most con- siderable of these, receives several important tributaries, the largest of which is the Lewis. The river Sacramento waters the northern half of the valley lying between the Sierra Nevada and the coast range of California, and forms at its mouth the harbor of San Francisco : immediately above this outlet it is joined by the San Joaquin, which drains the southern half of the valley, and carries off the waters of Lake Tule. The streams tributary to the Sacramento and San Joaquin, which flow in from the westj drain the gold regions of California. 250. Of the streams draining the northern slope of North America two divisions may be made, — one embracing the Nelson, Churchill, and other rivers flowing into Hudson Bay ; and the other, the Mackenzie, Coppermine, and other streams flowing into the Arctic Ocean. The most considerable of these streams is the Mackenzie, which issues from the western extremity of the Great Slave Lake : during the summer it pours a vast flood of waters into the sea, but is obstructed by ice during nine months of the year. 251. The Rio del Norte is a considerable stream of 1,400 miles in length, which rises in the southern part of the Rocky Mountains and runs a southwesterly direction into the Gulf of Mexico. To the south of this stream are few rivers of any con- siderable length. The San Juan, in Central America, possesses considerable interest from its having hitherto afforded the most ready means of communication between the opposite shores of the Atlantic and Pacific oceans. It has its origin in the lake of Nicaragua, on the southern portion of the plateau of Guatemala, and after a course of 120 miles, empties itself into the Caribbean Sea. Questions. — 249. The principal rivers draining the third division? The Columbia? Sacramento ? San Joaquim ? Gold regions, how drained ? 250. What two divisions of the streams draining the northern slope? The Mackenzie? 251. The Eio del Norte? San Juan ? C*0 SOUTH AMEKICAN KIVERS. LESSON VII. THE RIVER SYSTEMS OF THE WESTERN CONTINENT. 252. South American Rivers. — The three principal rivers of South America are the Orinoco, the Amazon, and the La Plata, which drain respectively the northern, middle, and southern por- tions of the great plain. 253. The Orinoco (about 1,200 miles long) rises in the mount- ains of Guiana. About 130 miles below' its source it sends off' to the southward a branch called the Casiquiare (200 miles in length), which joins the river Negro, a tributary of the Amazon, and thus effects a natural communication (navigable for boats) between the basins of these two great rivers. 254. The principal tributaries of the Orinoco are the Guav- iari, Meta, and Apure (rising in the Andes), on its left bank ; the Ventuari, Caura, and Caroni, on the right. Below the village of Angostura, 280 miles from the mouth of the Orinoco, no impedi- ments to its navigation occur : above this its course is occasion- ally interrupted by rapids, but in general it presents a deep and navigable channel nearly to its source. 255. The Amazon (called the Maranon in the upper portion of its course) rises in the small lake of Laurdococha, upon the table-land of Pasco, amid the highest parts of the Peruvian Andes, Thence it flows in a northerly course until it leaves the mountains, and afterward crosses the great plain in an easterly direction to the Atlantic Ocean. The whole length of the Ama- zon is little short of 3,900 miles. 256. The tributaries of the Amazon are numerous and on a grand scale, some of them being equal to the largest streams of the Old World. The principal are the Napo, Putumayo or lea, Yapura, and Negro, on the left bank : — the Huallaga, Ucayale, Javary, Jutay, Jurua, Teffe, Purus, Madeira, Tapajos, Xingu, -252. The three principal rivers of South America? 253. The Orinoco? Casiquiare ? 254. The principal tributaries of the Orinoco ? Its navigability ? 255. The Amazon? Its course? Length? 256. What is said of the tributaries of the Amazon? The principal tributaries on the left bank ? Upon the right banlc ? The Madeira ? SOUTH AMERICAN RIVERS. 81 and Tocantins, upon the right. The Madeira has a course of more than 2,000 miles before it joins the Amazon. 257. At the distance of 700 miles below its source the Ama- zon has a width of 800 yards, and during the last 450 miles of its course, it is nowhere less than four miles in width, and at its mouth the channel is fifty miles across. A recent exploration of this river* has proved that it is navigable for vessels of the largest class from its mouth to the very foot of the Andes, a dis- tance of about 3,500 miles. So great is the amount of water which it brings down that its freshness is perceptible at a dis- tance of more than 500 miles from the coast. 258 The Rio de la Plata is a broad fresh-water estuary, which receives the waters of the Parana and Uruguay. The Parana has its rise in the mountains of Brazil, and, reckoning from its most distant source to the mouth of the Rio de la Plata, is 2,350 miles in length. About 760 miles above the sea it re- ceives the Paraguay, which has a course of about 1,260 miles. The Uruguay (1,000 miles long) flows nearly parallel to the lower course of the Parana. Both the Parana and Paraguay are navigable for large vessels to a distance of nearly 1,000 miles. 259. Among the other principal rivers of South America are the Magdalena (860 miles), which flows into the Caribbean Sea, and the Atrato (300 miles), into the Gulf of Darien. The Es- sequibo, Demerara, Berbice, Surinam, and Maroni, flow into the Atlantic to the eastward of the mouth of the Orinoco. To the east and south of the Amazon are the Maranhao, Paranahyba, St. Francisco (1,500 miles), and many others belonging to the At- lantic coast. The Colorado (600 miles) and the Negro (800 miles) flow into the Atlantic southwest of the Rio de la Plata. 260. The rivers on the western coast of South America are very short : among the longest are the Biobio, in Chili, about 150 miles, and a few streams of nearly equal length to the north- ward of the Gulf of Guayaquil. Questions. — 257. Width of the Amazon ? How far navigable ? Illustrate the great ex- tent of water it brings down. 25S. The Kio de la Plata? The Parana? Paraguay? Uruguay? How far are the Parana and Paraguay navigable? 259. Other principal rivers of South America? Eivers flowing into the Atlantic to the east of the mouth of the Ori- noco ? To the east and south of the Amazon ? To the south of the Eio de la Plata? 260. The rivers of the western coast? Biobio ? * By Lieut Hemdon. 4* 8B EUROPEAN KIVEKS. LESSON VIII. RIVER SYSTEMS OF THE EASTERN CONTINENT. 261. European Rivers. — Europe is divided into two prin- cipal river systems, — one embracing those streams which have a southerly direction, and flow into the Mediterranean, Caspian, and Black seas ; the other comprising those which have a north- erly course, and terminate in the North, Baltic, and White seas, and the Arctic Ocean. 262. In the west, these two systems are for the most part di- vided by the Alps and German mountains ; but in the eastern part of Europe the division of the waters is merely a ridge of the great plain slightly elevated above the general level. This watershed begins on the northern declivity of the Carpathian Mountains, about the 23d meridian, in a low range of hills run- ning between the sources of the Dnieper and the tributaries of the Vistula, from whence it winds in a tortuous course along the plain to the Valdai table-land, which is its highest point, 1,200 feet above the sea. It then declines northward toward the Onega, about the 60th parallel, and lastly turns in a very serpentine line to the Ural Mountains, near the 62d degree of north latitude. 263. The Volga, which is the largest river of Europe, rises in the plateau of Valdai, at the height of 1,100 feet above the sea: its entire course is 2,200 miles in length, and the area of its basin about 520,000 square miles, or nearly one seventh of the whole surface of the continent. The Volga is navigable through nearly its whole length, and has considerable depth. During the greater part of winter it is frozen over but at other times is the highway of a most extensive traffic. 264. The Danube, 1,630 miles, is the second of the rivers ol Europe, both in length of course and in the area of its basin, which is 310,000 square miles in extent. It rises in the Black Forest, to the north of Switzerland, at a height of 2,200 feet Questions. — 261. Into what two river systems is Europe divided ? 262. Division of the two systems in the western part? In ihe eastern part? Describe the course of the water- shed through eastern Europe. 263. Give particulars of the Volga. How far navigable ? 264. Give particulars of the Danube. Its source, direction, and termination ? EUKOPEAN RIVERS. 83 'above the level of the sea, and flows in an easterly direction across the plateau of Bavaria, through Austria, the plain of Hun- gary, and between Bulgaria and Wallachia, until it enters the Black Sea. 265. The Danube is navigable from its mouth up to Ulm (10° east longitude), or throughout nearly, the whole length of its course, excepting between the towns of Moldova and Gladova, where it passes, for a space of 60 miles, through a succession of rapids and shallows. The principal tributaries are the Inn, the Drave, the Save, and the Morava, on the south (or right- hand) bank; and the March, the Theiss, the Aluta, and the Pruth, on the north side ; all of these are rivers of considerable magni- tude. 266 Of the other principal streams which flow into the Black Sea are the Dniester (700 miles), the Dnieper (1,200 miles), and the Don (1,100 miles). The Dnieper is navigable from Smo- lensk to the sea, excepting for a distance of about 150 miles be- low Kiev, within which its navigation is impeded by rocks and cataracts. 267. The Rhine rises in the Alps, at an elevation of 6,580 feet, and flows in the upper portion of its course through Lake Con- stance. It has a length of 760 miles, and its basin is 70,000 square miles in area : at Basle (where it is 765 feet above the level of the sea) its breadth is 800 feet, at Mentz about 1,700, and at Cologne 1,400. It is navigable for boats as high up as the Falls of Schaff'hausen, a short distance below Lake Con- stance, and for vessels of some magnitude as high as Strasburg. The current is generally rapid, flowing at the rate of four or five miles an hour. Its principal affluents are the Neckar and Mayne on the right bank, and the Aar and Moselle on the left. 268. Of the other considerable rivers flowing into the Atlantic Ocean are — the Elbe (690 miles) and the Weser (380 miles) to the north, and the Meuse (550 miles), Seine (430 miles), Loire (570 miles), and Garonne (350 miles), to the south. Spain is Questions.— 265. Navigation of the Danube ? Tributaries ? 266. Other streams which flow into the Black Sea ? The Dnieper ? 267. The Ehine ? Its length, extent of its basin, etc. ? Its principal affluents ? 268. Other considerable rivers flowing into the Atlantic Oceaa ? Rivers of Spain ? 84 ASIATIC KIVEKS. watered by numerous rivers, as the Minho (200 miles), the Douro (460 miles), the Tagus (510 miles), and the Guadiana (450 miles) ; they are all navigable in the lower parts of their courses The Guadalquiver (290 miles) is navigable for large vessels up to Seville. 269. The rivers which flow into the Mediterranean have gen- erally short courses, owing to the nearness of the mountains on the north. The Ebro (420 miles) flows from the eastern side of the Spanish table-land. The Rhone (490 miles) rises in the' highest region of the Alps, and passing in its course through Lake Geneva, below which it is navigable, falls into the Gulf of Lyons. The Arno (150 miles) and the Tiber (210 miles), both water the western side of the Italian peninsula ; the Po (450 miles) and the Adige (250 miles) flow through the plain of Lombardy, and enter the Adriatic Sea near its northern ex- tremity. 270. Of the rivers flowing into the Baltic Sea are — the Duna (450 miles), the Niemen (400 miles), the Vistula (630 miles), and the Oder (550 miles). The Duna, the Vistula, and the Oder are navigable for the greater part of their courses. The Neva, which flows into the head of the Gulf of Finland, though only 46 miles in length, is of considerable importance, and has a vast volume of water, since it is the outlet of the great lakes of Lad- oga and Onega : it has a mean breadth of 1,500 feet and a depth of 50 feet, but is frozen over for five months of the year 271. The White Sea and Arctic Ocean receive several im- portant streams, among which are the Dwina (760 miles), the Mezen (480 miles), and the Petchora (500 miles). LESSON IX. RIVER SYSTEMS OF THE EASTERN CONTINENT (contiuued) . 272. Asiatic Rivers. — The rivers of Asia may, like those of Europe, be divided into two principal classes, separated by -269. What is said of the rivers flowing into the Mediterranean ? The Ebro? Ehone? Other streams ? 270. The principal rivers flowing into the Baltic Sea? Which are navigable ? The Neva? 271. Streams flowing into the White Sea and Arctic Ocean? 272. How may the rivers of Asia be divided ? The northern division ? The other class ? ASIATIC RIVERS. 85 the mountains and table-lands which extend east and west through the interior. The northern division embraces the rivers which flow into the Arctic Ocean, and those (in the west) which termi-= nate in inland seas or lakes unconnected with the ocean. The other and more numerous class includes the streams which have their origin in the mountains of the interior, and flow either southerly into the Indian Ocean, or eastwardly into the Pacific « 273. The Obi, which flows into the Arctic Ocean, is 2,530 miles in length; its river-basin is 1,250,000 square miles in ex= tent, being probably the largest basin of any river in the Eastern hemisphere. Of the other considerable rivers in the north of Asia are the Yenesei (2,900 miles) and the Lena (2,400 miles). The Obi, Yenesei, and Lena all rise in the mountains of the Altai system, and flow through the Siberian plain. Owing to the severity of the climate their waters are frozen during a great part of the year, and they are hence of little use for the purposes of navigation. 274. The Ganges (1,460 miles) and the Indus (1,700 miles), two of the most important rivers of Asia, both water the north= em portion of Hindoostan. The Ganges, whose basin extends from east to west to the south of the Himalaya Mountains, flows in an easterly direction into the head of the Bay of Bengal. At its mouth it divides into numerous arms, which inclose a delta of immense extent (page 72) : its most western arm, called the Hoogly, upon which Calcutta is built, is the only one that is usually navigated. The Ganges is remarkable for the great ex- tent of its fall : it is ascended by steamers as high as Allahabad, more than 800 miles from its mouth. 275. The Indus rises on the plateau of Tibet, to the northward of the Himalaya Mountains, at an elevation of more than 15,000 feet, and flows into the Arabian Sea. About 470 miles above its mouth the Indus receives on its left bank the river Chenaub, which collects the waters of the five streams of the Jeloam, the Chenaub, the Ravee, the Bayas, and the Sutlej. The district watered by these five rivers is called the Punjaub* All the Questions. — 2T3. The Obi? Other considerable rivers of northern Asia? What further is said of the Obi, Yenesei, and Lena ? 274. The Ganges and Indus ? Give particulars of the Ganges. 275. The Indus. Its tributaries. Hovr far navigable ? * Properly, Pe-nj-ab, or five rivers. 86 AFRICAN KIVEES. chief tributaries of the rivers, as well as the main stream, are navigable through nearly their entire length : steamboats of con- siderable size can ascend to more than 500 miles distance from the sea, and smaller vessels to 500 miles higher. 276. Of the other principal rivers belonging to the basin of the Indian Ocean are the Saleun and the Irawaddy (1,200 miles), both flowing into the Gulf of Martaban ; the Brahmapootra, the Godavery, the Krishna, and the Cauvery, into the Bay of Ben- gal ; the Nerbudda, into the Gulf of Cambay ; and the united Euphrates (1,600 miles) and Tigris (980 miles) into the Persian Gulf. 277. The seas to the east of Asia receive several large rivers, among which are the Amour (2,300 miles), which flows into the Gulf of Tartary ; the Hoang-Ho (2,600 miles), and the Yang-tse Kiang (3,200 miles), both flowing into the Yellow Sea ; and the Cambodia (2,000 miles), into the Gulf of Siam. 278. The drainage of a large part of the Asiatic continent — probably not less than four and a half millions of square miles — is unconnected with any of the surrounding oceans, but is re- ceived into inland seas or lakes, of which the Caspian and Aral possess the most extensive basins. The principal continental rivers of Asia are the Kour (550 miles), the Amoo, or Jihon (1,300 miles), and the Sihoon (1,150 miles), flowing into the Sea of Aral. The Tarim, or Erghue (900 miles), flows into the Lake of Lop, in the center of the continent. The Helmund (600 miles), which rises in the plateau of Afghanistan, falls into Lake Zurrah ; the Jordan, in Palestine, into the Dead Sea. 279. African Rivers. — The Nile is the most considerable river of Africa : it carries ofl" the waters from the northern and western sides of the plateau and mountains of Abyssinia, and discharges itself into the Mediterranean. The Nile is formed by the junction (in latitude 15° 40^ north) of two streams, — the Bahr-el-Azrek (Blue River), and the Bahr-el-Abiad (or White River) : the latter is generally admitted to constitute the main -276, Name the principal rivers belonging to the basin of the Indian Ocean. 27T. Those flowing into the eastern seas. 278. Extent of the surface drained into the in- land seas ? Principal continental rivers of Asia ? Into what seas or lakes do they re- spectively flow V 279. What is said of the Nile ? How formed ? Source of the NUe? How far has its course been traced ? AFRICAN RIVERS. 87 cnannel of the river. The source of the Nile — calling the head waters of the Bahr-el-Abiad its real source — has not yet been visited by Europeans, but its course has been traced upward to within four degrees of north latitude, and there is reason to be- lieve that it rises to the southward of the equator. 280. Though the Nile has so great a length of course — prob- ably not much short of 3,500 miles — its basin is of very limited extent. For a distance of 1,400 miles above its mouth it re- ceives no tributary. Through the middle and lower portion of its course, the Nile flows in a narrow valley inclosed on either side by steep rocks : the width of this valley varies from one to two miles in Nubia and Upper Egypt to as many as ten or twelve miles lower down the stream 281. The Niger (or Quorra) is the largest of the African riv- ers which flows into the Atlantic Ocean. It rises in the mount- ains of Soudan, where the main tributary is known as the Joliba, pursues a northeasterly course to the neighborhood of Timbuctoo, thence a southeasterly course, passing through a wide opening of the Kong Mountains, and enters the eastern extremity of the Gulf of Guinea by several mouths. The length of the Niger is perhaps about 2,300 miles : above the place of its passage through the Kong Mountains, it receives the waters of the Chadda, a broad and deep tributary. The Niger has been ascended by a steamboat to more than two hundred miles above the junction of the Chadda, but the extreme unhealthiness of the climate, in the district through which its lower course lies, has contributed to the failure of many attempts made to explore this part of Africa, and to establish commercial relations with the inhabitants. 282. Besides the Niger, the principal rivers upon the west coasts of Africa are the Senegal, the Gambia, the Rio Grande, the Rokelle, the Volta, the Zaire or Congo, the Coanza, and the Gariep or Orange. Both the Senegal (900 miles) ^nd the Gam- bia (650 miles) are navigable rivers : they flow in a westerly di- rection, and draw their waters from the same mountain ranges in Questi(yns.—2S0. Length ? Basin ? Width of the valley in different parts ? 281. The Niger ? Its source, direction, and termination ? Length ? How far ascended by a steam- boat ? The climate of the district in which its lower course lies ? 2S2. Other principal rivers upon the west coasts of Africa ? The Senegal and the Gambia ? The Gariep ? The principal river upon the eastern side ? Other rivers ? 88 LAKES. which are the sources of the Niger. The Gariep, or Orange River, in the southern part of Africa, has a length of upward of 1,000 miles. The principal river upon the eastern side of Africg is the Zambesi, whiel brings down a great volume of water, and is said to be navigable for boats through a distance of more than 900 miles. The Li*fij., Juba, and many other rivers of the east- ern coast, have not been explored, and are but little known. LESSON X. LAKES. 283. Fresh-water lakes occur in the greatest numbers, and upon the largest scale, in the northern regions of the globe. Nearly all the lakes of any considerable extent in North America are situated north of the 40th parallel, while in Europe and Asia, the regions peculiarly characterized by fresh-water collections are, for the most part, north of the 50th parallel. Salt-water lakes have a more southerly distribution, and are very abundant in eastern Europe, and central and southern Asia. 284. Lakes maybe divided into four classes, according to cer- tain physical peculiarities. The^r^^ class includes those which have no outlet, and do not receive any running water. Lake Albano, near Rome, is an example. Many of these lakes are situated in elevated districts, and are generally small : it has been supposed that they are the craters of extinct volcanoes, and are supplied by springs 285. The second class comprises those which receive water, but have no apparent outlets. The Caspian Sea and Lake Aral belong to this division. The Caspian is about 600 miles long : its extreme breadth is 300 miles, though its average breadth is not more than 100 miles. This most remarkable lake receives the waters of the Volga, a river which has a course of 2,200 miles, QuesUons.~^2%Z. Where are fresh-water lakes most abundant ? In North America ? In Europe and Asia ? Salt-water lakes ? 284. Into how many classes may lakes be divided ? First class? Example, Situation of these lakes, etc. ? 285. Second class? Examples. The Caspian ? What waters are tributary to it ? LAKES. 89 and brings down more than 518,000,000 cubic feet of water every hour. The Ural, and many other streams of consider- able magnitude, are also received by the Caspian; but its level IS not changed, though it has no perceptible outlet by which to discharge the water it receives. 286. Lake Aral presents the same phenomena, and, though not to be compared in extent to the Caspian, receives two large rivers, the Sihoon and Amoo, or Jihon. The difficulty in explain- ing the nature of these lakes is to account for the constancy of their level, which might be expected to rise considerably, as they are daily receiving so large a body of water. The opinion was once entertained that they are connected by some internal chan- nel with the sea, and it was supported by the fact that the water of both the Caspian and Lake Aral is salt, and contains marine productions ; but it has been ascertained that the Caspian is not less than 84 feet below the level of the Black Sea, thus com- pletely disproving the hypothesis that they have a connection. It is thought that the phenomena referred to may be accounted for by evaporation and filtration. Besides the Caspian Sea and Lake Aral, there are -numerous other bodies of water of this class, the receptacles of the continental rivers. (See table of Continental Rivers page 74.) 287. A third class comprehends all those lakes which receive no streams, but give birth to some. Many of these lakes occupy very elevated situations, and are the sources of some of the largest rivers. They are no doubt supplied by springs, the waters of which rise in their reservoirs until its level is sufficiently high to admit a discharge. The lake in Monte Rotondo, in Cor- sica, is one of this class, and is situated 9,000 feet above the level of the sea. 288. The fourth class includes all those lakes which both receive and discharge water, being by far the most numerous division. They commonly receive the waters of many rivers, and have but one outlet. The origin of such rivers is easily Questions. — 286. Lake Aral ? Opinion formerly entertained ? How supported ? How is this hypothesis disproved ? How may the constant level be accounted for ? What other lakes belong to this class? 287. Third class? What is said of many of the lakes of this class ? How supplied ? Monte Kotondo ? 288. Fourth class ? How is the origin of such lakes explained ? 90 NORTH AMERICAN LAKES. explained. Should a hollow present itself in the course of a river, it is evident that it must be filled to the level of some part of its banks before the river can proceed, and this would produce a lake. But it may happen that there is a general declivity from various parts of a district toward some central valley, and then the waters of a number of rivers may be brought into it, while at the same time the continuation gives but one course by which the waters can be discharged. A description of some of the largest lakes of this class will be given in the next lesson. 289. Most lakes occur at varying elevations above the level of the sea, while some are much below it. The highest knovirn lake in the world is Sir-i-kol, in Asia. It is the source of the Amoo River, and is 15,600 feet above the level of the ocean. Lake Titicaca, in Bolivia, has an elevation of 12,785 feet ; Tzana, or Dembea, in Abyssinia, 6,076 feet; Lake Baikal, in Asia, 1,793 feet; Constance, 1,299 feet; Geneva, 1,229 feet; Great Salt Lake, in Utah Territory, 4,200 feet ; Superior, 623 feet ; Huron and Michigan, 591 feet ; Erie, 565 feet ; Ontario, 234 feet. The Caspian Sea, Lake of Tiberias, and the Dead Sea, are each be- low the sea-level, — the first 84 feet, the second 600 feet, and the third 1,316 feet.* LESSON XL LAKES — (continued). 290. North American Lakes. — The largest lakes in North A.merica are Superior, Huron, Michigan, Erie, and Ontario, "Which are connected with the sea by the channel of the river St. Lawrence ; Winnipeg, which is drained by the river Nelson into the Hudson Bay; and the Athabasca, Great Slave, and Great Bear, which empty their waters into streams tributary to the Arctic Ocean. Questions. — 289. Varying elevations and depressions of lakes? Highest known lake, its elevation, etc. ? Give the elevations of the other lakes mentioned. State the depres- sions of the Caspian, Lake of Tiberias, and the Dead Sea. 290. Which are the largest lakes in North America, and how drained ? * According to the measurement made by Lieutenant Lynch, in 1848, the exact deprw- eion of the Dead Sea below the Mediterranean was found to be 1,816-T feet NORTH AMERICAN LAKES. 91 291. Lake Superior is the largest fresh-water formation on the globe, computed to have an area of 40,000 square miles; length 420 miles ; extreme breadth, 165 ; height above the level of the Atlantic, 623 feet; greatest depth 1,200 feet. There is reason to believe, from the appearance of the shores, that the waters of this, as well as the other Canadian lakes, formerly oc- cupied a much higher level than they reach at present. The amount of water carried off by its outlet, the river of St. Mary, is much less than that received by its tributaries, from which circumstance it is inferred that the evaporation from its surface must be very great. 292. Lake Huron, remarkable for its brilliant transparency, has an area of 25,000 square miles. It is about 240 miles in length, from 180 to 220 in breadth, and is 591 feet above the level of the sea. The outline of this lake is very irregular, and its shores are described as consisting of clay cliffs, rolled stones, abrupt rocks, and wooded steeps. The greatest depth of Lake Huron is found to be nowhere more than 450 feet. Lake Mich- igan, which lies wholly within the United States, is connected with Lake Huron by means of the navigable channel Mackinaw. It is about 300 miles long, and has an area of about 25,000 square miles. 293. Lake Erie has an area of about 11,000 square miles : its surface is 565 feet above the sea. This lake is said to be the only one in the whole Canadian chain in which there is any per- ceptible current, a circumstance which is supposed to be attrib- utable to its comparative shallowness, its average depth being not more than 60 or 80 feet. The current of Lake Erie, which runs always in one direction, combined with the great prevalence of westerly winds, and the occurrence of sunken reefs and rocky banks, form serious obstacles to the safe and easy naviga- tion of this lake. The shallowness of the water of Lake Erie likewise causes it to be more readily and more permanently af- fected by frost, so that its navigation is usually obstructed by ice for some weeks every winter, Avhile that of the other lakes continues open and unimpeded. Questions. — 291. Give particulars of Lake Superior. Change of level ? 292. Give par- ticulars of Lake Huron. Lake Michigan. 293. Lake Erie. What is said of its current? Its navigability ? 92 NOETH AMEEICAN LAKES, 294. Lake Ontario has a computed area of 10,000 square miles, 234 feet above the sea-level, and 331 feet below the level of Lake Erie. Its depth is said to be very great, and it is nav- igable throughout its w^hole extent for the largest ships. Its out- let is a spacious channel studded with islands, collectively de- nominated the Thousand Isles, but no less than 1,692 have been actually counted. 295. Lake Champlain (about 500 square miles) belongs to the same basin as the great lakes above described, and is connected with the St. Lawrence by the river Richelieu. Lake George, tVmf^LOCELYN-A^'^'^- Lake George noted for its picturesque scenery, and for the transparency of its waters, is situated west of the southern extremity of Lake Cham- plain, with which it is connected by a short stream. It is about 30 miles long, and from 1 to 2 miles broad. 296. The Great Salt Lake (about 2,600 square miles), situ- ated in the great basin between the Rocky Mountains and the Questions. — 294. Give particulars of Lake Ontario. The Thousand Isles. Champlain. Lalce George. 296. Great Salt Lake. What are its waters ? 295. Lake EUROPEAN LAKES. 93 Sierra Nevada (111), is about 70 miles in length, from 30 to 35 miles in breadth, and is about 4,200 feet above the level of the sea. Its waters are saturated with common salt, and when the lake is low, considerable quantities of this substance are precip- itated to the bottom of the lake, or, rather, are there crystallized. No living animal can exist in this lake. It receives the waters of the Bear, Weber, and other rivers, but, like other lakes in this region, has no connection with the ocean. 297. Upon the Mexican plateau is the large lake of Chapala (about 650 square miles), which is discharged into the Pacific by the river Santiago. Lake Nicaragua (about 3,500 square miles), in Central America, lies at an elevation of about 128 feet above the sea. The distance between its western shore and the coast of the Pacific is only eleven miles ; it is drained by the San Juan, which flows into the Caribbean Sea. 298. South American Lakes. — South America has few lakes of any great extent.. The largest is Lake Titicaca (about 3,800 square miles), situated on a plateau of that name, at an elevation of 12,785 feet, and surrounded by some of the highest summits of the Andes. The water of Lake Titicaca is fresh; a river called the Desaguadero, which leaves its southern extremity, flows into the smaller lake (or marsh) of Aullagas, or Uros, which lies at 490 feet lower level, and the water of which is salt. 299. Lake Maracayho (5,000 square miles), near the coast of the Caribbean Sea, is connected by a narrow strait with the Gulf of Maracaybo, and has brackish water. The Lake dos Patos and Lake Mirim are on the southeast coast of Brazil. LESSON XII. , LAKES — [continued) . 300. European Lakes. — There are two principal lake-re- gions in Europe, one lying around the Baltic, and situated within Questions. — 297. Give pnrticulars of Lake Chapala. Lake Nicaragua. 29S. Wliat is eaid of South America? Lake Titicaca ? 299. Lake Maracaybo ? Other lakes? 300. How many lake-regions are there in Europe, and where are they respectively situated ? How are the lakes of each division characterized ? 94: EUROPEAN LAKES. its basin ; and the other embracing the Alpine system of mount- ains. The lakes situated in the former of these regions possess, in general, greater magnitude, while the latter are distinguished by their great elevation above the sea, and by the grandeur of the scenery among which they lie. 301. The following Tables give the dimensions of the principal European lakes, together with their elevation and greatest depth, where these particulars have been ascertained. Lakes situated round the Baltic. In Russia — Ladoga Onega Ilmen Peipous, or Tchoudskoe Pskov Bieloe Saima Enara* In Sweden — ^Wener Wetter Maelar Area in Sq. Miles 6,330 3,280 390 1,250 280 420 2,000 1,200 2,136 840 Ileiffht. 144 288 Depth. 288 432 Lakes belonging to the Alpine System. Area in 3q. Miles. Height. Depth. Ttm Stji7't't'7:t'"r t. a ivt) — (renevaj ......... - 240 115 99 76 228 150 250 152 66 183 1,230 1,437 1,430 1,332 1,299 350 918 678 684 320 1,012 426 600 600 964 13 36 2,622 600 Neufchatel Zurich Constance, or Boden See In Hungary— Neusiedler See Balaton, or Flatten See. In Italy— Lago Maggiore Garda 302. Lakes are very numerous in Scotland, especially in the middle and northern parts. They are mostly long and narrow Q'iiestions.— 301. What is the area of Lake Ladoga ? Of Onega ? Of other lakes in Eussia ? Give particulars of Lake Wener. Of other lakes in Sweden. Of Geneva. Of other lakes in Switzerland. Of Lago Maggiore. Of other lakes in Italy. 302. What is said of the lakes in Scotland ? Loch Lomond ? * The waters of Lake Enara, however, communicate with the Arctic Ocean, not with the Baltic. ASIATIC AND AFRICAN LAKES. 95, bodies of water, occupying the deep hollows within the elevated mountain- valleys. The largest lake in Scotland, and also in Great Britain, is Loch Lomond (45 square miles), which is 24 miles in length, and 7 miles in its greatest breadth. 303. Of the lakes in Ireland the largest is Lough Neagh (150 square miles), situated in the north of Ireland, and the Lakes of Killarney (three in number), noted for their beautiful scenery in the south. 304. Asiatic Lakes. — The largest fresh-water lake in Asia is Lake Baikal, situated among the northern offsets of the Altai mountain-system: it has an area of about 15,000 square miles, and lies at an elevation of 1,793 feet above the level of the sea. Its water is fresh, and abounds in fish. It is annually frozen over for a period of five or six months, and may be traversed on sledges 305. Among the smaller lakes of Asia are Balkashi, Oubsa, Zaisang, Issyk, Bosteng, Lop, Koko-nor, Bouka-nor, and Tengri- nor — all on or adjacent to the high plateaus in the interior of the continent ; — Tong-ting and Poyang, in China ; — Zurrah and Bakhtegan (both salt), on the plateaus of Afghanistan and Per- sia ; — Urumiyah, Van, and Goukcha (the two former of which are salt), on the Armenian table-land ; — the salt lake of Koch- hissar, in Asia Minor ; — ^with Lake Tiberias and the Dead Sea in Palestine. 306. African Lakes. — The largest body of inland water known in Africa is Lake Tsad, which lies in the central part of the contiiient and is several thousand square miles in area. Its waters are very shallow, though fresh and clear. It is not known to have an outlet, but it probably has a channel of dis- charge like all fresh-water lakes. 307. Of the other African lakes are Lake Dibhie, through which the Quorra passes, and Lake Tzana, or Dembea, in Abys- sinia. A large lake, called Ngami (or " the Great Water"), has recently been discovered in the southern part of Africa, near the 20th parallel, lying at an elevation 2,800 feet above the sea. Questions. — 303. Lakea in Ireland ? 304. Give particulars of Lake Baikal. 305. What other Asiaticlakes are mentioned ? 306. Give particulars of Lake Chad. SOT. Of o'ih«e African lak««. 06 THE OCEAN LESSON XIII. THE OCEAN. 308. The vast body of water which surrounds the land and penetrates its coast, is comprehended under the general name of the ocean. For convenience sake it is divided "into five portions, named, respectively, the Arctic, Atlantic, Indian, Pacific, and Antarctic oceans. These, with their branches, are as follows : Arctic Ocean . . Atlantic Ocean Pacific Ocean. Indian Ocean Antarctic Ocean. I. ^ Extends from the northern shores of America, Europe, Asia, and the arctic circle around the north pole n. Bounded on the west by Amer- ica ; east by Europe and Afri- ca; north by the arctic, and south by the antarctic circle — divided by the equator into the North and South Atlantic ni. Inclosed between America on the east; Asia, the Sunda Isles, and Australia on the west ; and the arctic circle on the north ; the antarctic on the south — divided by the equator into the North and South Pacific IV. Bounded by Africa on the west ; the Sunda Isles and Australia on the east ; south- ern Asia on the north ; and the antarctic circle on the south Branches. Baf&n'sBay. White Sea. Gulf of Kara. Gulf of Obi. Baltic with its gulfs. North Sea. Mediterranean. Black Sea, Hudson's Bay. Gulf of Mexico. Caribbean Sea. Sea of China. Yellow Sea. Sea of Japan. Sea of Okhotsk. Sea of Kamtchatka. Behrings Strait. Gulf of California. Bay of Panama. Red Sea. Arabian Sea. Persian Gulf. Bengal Sea. Extends V. from the antarctic circle around the south pole '} Qioestiom.—SGS. Under what general name is the vast body of water which surround* the land comprehended? How is it divided? Describe the situation, and mention the principal brancbes of the Arctie Ocean, Atlantic, Pacific, Indian, Antarctic THE AKCTIC OCEAN. 97 309. The Arctic Ocean has been but partially explored. Va- rious efforts have been made to reach its higher latitudes, but, up to this time, they have proved unsuccessful, in consequence of the impenetrable fields of ice which are met with, and the impos- sibility of remaining in those regions, with safety, for a great length of time. During the winter months the waters of the Arctic Ocean are covered with ice, which in summer is broken up, and drifted into lower latitudes where it is dissolved. Scene in the Arctic Ocean 310. The floating masses of ice in the Arctic waters are of two kinds, sheet-ice and icebergs, which have quite an inde- pendent origin. Sheet-ice is that which is formed by the freez- ing of the ocean's surface, and is generally level like that of lakes ; it rises from 2 to 8 feet out of the water. Yast fields, 20 or 30 miles in diameter, have been found in the Arctic Ocean : sometimes they extend 100 miles, so closely packed together that no opening is left between them. Smaller sheets are called floes. Fields and floes, when much broken up, the fragments crowding together, form what is called pack-ice, which when much elongated is called a stream. When the parts of a pack are loose and open, so that a vessel may sail between them, it is called drift-ice. Questions. — 309. What is said of the Arctic Ocean ? Why have the efiforts made to reach its higher latitiules been unsuccessful? 310. Of what two Ivinds nre the floating masses of ice ? Describe the sheet-ice. Its extent. Floes. Tacli-ice. Streams. Drift-ice. 5 98 THE AKCTIC OCEAN, 311„ In 1850, Lieut. De Hayen, commanding the Grinnell Expedition in search of Sir John Franklin, proceeded into the Arctic Ocean a considerable distance north of Wellington Channel. Here, in the early part of October, ■vrhile drifting about among large masses of floating ice, his yessels (two in number) were frozen in so firmly that it was impossible, with all the means at command, to disengage them from the ice. In this state they were drift- ed back through Wellington Channel and Lancaster Sound into Baffin'sBay, thence southeasterly through this bay to about latitude 66° north, where after having been confined in the ice nearly eight months, and having drift- ed not less probably than 1,^00 miles, they were liberated from their icy fetters. Icebergs. 312. Icebergs d^re. fresh-water formations; and, towering like cliffs to a considerable height, they present a very different as- pect from ice-fields. They are produced on the shores of arctic lands by the freezing of melted snow, like the glaciers of Switz- erland. The frozen masses projecting into the sea, yield to its undermining and wrenching power, by which immense blocks are broken off, constituting icebergs. These huge masses are drifted southward 2,000 miles from the places of their origin to Questimis.—ZW. What part of the Arctic Ocean was reached by tieut. De Haven? What subsequently happened to bis vessels ? How long were they confined and how far did ihey drift ? 312. What are icebergs ? How produced ? How far south do they some- times drift ? ' - THE OCEAN. \)\) melt in the Atlantic, where they cool the water and air to a great distance around. Icebergs vary from a few yards to miles in circumference, and are often 1,000 feet high. 313, It is supposed that the point of the greatest cold is in the vicinity of Melville Island, and that to the north and west of it, there is, in summer, a comparatively open sea, or " Polynja." The latter opinion is supported by the fact that beasts and fowls are known to migrate over the ice from the mouth of Mackenzie River, and its neighboring shores to the north. In further con- firmation of this conjecture, Lieut, De Haven reported that as he entered Wellington Channel the signs of animal life became more abundant ; and Captain Penny, commander of an English expedition, who penetrated on sledges farther toward the north than it was possible for De Haven to do, reported that he actually arrived on the borders of this open sea. 314, The Atlantic Ocean is the best known of any of the divisions of the great deep, it being the highway of the world's commerce, and constantly traversed by hosts of vessels in which millions of property and thousands of lives are embarked. It extends upward of 9,000 miles from north to south, with a width varying from little more than 900 miles between Norway and Greenland, to 1,700 miles between Cape St. Roque, in Brazil, and the coast of Sierra Leone, in Africa. 315, The North Atlantic, though generally very deep, is re- markable for immense shoals occurring in the North Sea, and to the southeast of Newfoundland. It is also noted for the im- mense portion of its surface occupied by sea-weed (fucus natans), closely matted together, forming what is sometimes known as the " Grassy Sea " A region of this weed extends along the me- ridian of 40° west longitude, and between the latitudes 20° and 45° north, bearing the name of " Banks of Fucus." It occurs thence in varying quantities to the Bahamas, the area occupied being equal to 1 ,000,000 geographical square miles and upward, — more than one third the extent of the whole territory of the United States. QueHiojVi —SIS. Supposed point of the greatest cold ? Open sea or '■■ Polynja" ? Con- firmation of this conjecture ? 314. The Atlantic Ocean? Its extent? 315. The North Atlantic ? For what noted ? Where are Ihe Banks of Fucus situated ? Where else does it occur ? Extent of the sea so occupied ? 100 TEMPEKATURE OF THE OCEAN. 316. The Pacific Ocean has about twice the area of the At- lantic, extending upward of 9,000 miles from north to south, and from east to west 12,000 miles. It was so called by the early navigators on account of its peaceful aspect, as contrasted with the stormy seas of Cape Horn, It is remarkable for the number of its islands, and for submarme coral formations, which render navigation difficult and dangerous. 317. The Indian Ocean extends upward of 6,000 miles, from the tropic of Cancer, at the head of the Arabian Sea, to the ant- arctic circle ; and has its greatest breadth, amounting to 5,000 miles, between the south point of Africa and Van Diemen's Land. It is remarkable for its hurricanes and monsoons, which will be treated of in another division. 318. The Antarctic Ocean presents features similar to the Arctic, but the ice extends farther from the south than from the opposite pole. Its waters are almost always agitated; there is a perpetual swell, and terrific storms are common. Packed ice occurs to an immense extent. Sir James Ross passed through a belt upward of 800 miles broad. 319. The discoveries, m 1840, of Commodore Wilkes, com- mander of the United States Exploring Expedition, established the fact that there is a vast antarctic continent near the south pole. Victoria Land, the most southern land known, was dis- covered in the same year by Sir James Ross, who penetrated to latitude 70° south, the point nearest the south pole ever yet reached. LESSON XIV. THE OCEAN — {continued). 320. The temperature of the ocean, though varying in differ- ent latitudes, is more uniform than that of the land. Thus, in equatorial regions, the difference in the temperature of the air Questions.— ^\&. What is said of the Pacific Ocean ? Why so called ? For what re- markable? 317. The Indian Ocean? For what remarkable? 31S. Antarctic Ocean? State of its waters? Packed ice? 319. The discoveries of Commodore Wilkes? Of Sir James Ross ? 820. What is said of the temperature of the ocean? Illustrate. I COLOR OF THE OCEAN. 101 near the surface of the sea, by day and night, does not appear to exceed three or four degrees. In temperate climates the diurnal range of temperature is rather greater, but it is by no means equal to that on land, 321. From numerous observations of the temperature of the ocean the following facts have been deduced: 1. The temper- ature of the surface of the ocean is generally lower at raid-day than that of the atmosphere in the shade. 2. It is always higher at midnight. 3. Morning and evening the two temperatures usually correspond. 4. The mean temperature of the surface of the ocean far from land is greater than that of the atmosphere with which it is in contact. 5. The water is colder where it is shallow than where it is of great depth. 6. The seasonal changes of the temperature of the air do not affect the ocean beyond the depth of 300 feet. 7. The greatest heat of the surface, 88° 5^ of Fahrenheit, is found in the Gulf of Mexico, and in one of the havens of New Guinea. 322. The color of the ocean is generally of a deep bluish green, but it varies with every gleam of sunshine or passing cloud, from the deepest indigo to green, and even to a slaty gray. It is dif- ferent in different localities, depending upon local causes. It is ^vhite in the Gulf of Guinea and black around the Maldives. Be- tween China and Japan it is yellowish, and west of the Canaries and Azores it is green. In some parts, as off California, it has a Vermillion hue ; in others, as the eastern division of the Mediter- ranean Sea, a purple tint prevails. 323. These various shades are, in most instances, caused by myriads of marine animalcules which pervade the deep ; and the magnificent appearance, known as the phosphorescence of the ocean, is owing to the phosphorescent brilliancy of these microscopic tribes. The bed of the ocean, in shallow places, often imparts a tinge to the superincumbent waters, while the gray or turbid appearance, near the mouths of large rivers, arises from the sediment washed in from the land. Questions. — 321. What is said of the temperature of the surface of the ocean at mid-day ? At midnight? Morning and evening? Of the mean temperature of the ocean far from land? Of shallow -water? Depths affected by seasonal changes ? Where is the greatest heat of the surface found? 322. Color of the ocean? Mention its hues in different local- ities. 823. How are these shades generally caused ? What other causes affect its color? 102 DEPTH OF THE OCEAN, The Ocean. 324. The depth of the ocean was, until recently, a subject of speculation only. The experiments made during the past few years have added more to our knowledge of the depth of the ocean and the shape of the oceanic basins, par- ticularly that of the Atlan- tic, than was ever before known. 325. Like the dry land, the bottom of the sea is di- versified with slopes, plains, table-lands, eminences ab- ruptly projecting to within a few feet of the surface, or just peering above the waves, and with enormous depressions. It has been generally supposed that the depth of the sea is about equal to the height of the land, the lowest valleys of the ocean's bed corresponding with the summits of the loftiest mountains. 326. The recent experiments caused to be made by Lieut. Maury, of the National Observatory, seem likely to confirm this conjecture. Before he undertook the subject, there had been no well-directed efforts made to ascertain the depths of the deep sea. Navigators had, indeed, tied weights to lines, and thrown those weights overboard with the view of ascertaining the depth, but the lines were often unwieldy, and there was no certain means of knowing whether the plummet had reached the bottom, or, if it had reached the bottom, when. 327. Recent investigation has led to the supposition that there is in the ocean, as in the air, a system of circulation, which, by currents and counter currents, upper and under currents, keeps the waters of the sea perpetually in motion. For it has been found that, generally speaking, when a sounding has been made Questions. — 324. What is said of the depth of the ocean? Recent experiments? 825. How is the bottom of the sea diversified ? What was generally supposed respecting the depth of the sea? 326. What is said of former efforts to ascertain the depth of the sea? 827. To what supposition has recent investigation led? What circumstances favored this supposition? • DEPTH OF THE OCEAN. 103 in the deep sea, though the vessel from which it is made be per- fectly at rest, and though it be known that the plummet has reached the bottom, yet the line will continue to run out, and un- less it be suffered to run out, or the plummet be detached from it, a strain so great is brought upon it that it invariably breaks. It is the undertow, or a system of currents and counter currents below, which it is supposed produces this strain. 328. Most of the vessels of the navy are now furnished with twine made especially for deep-sea soundings ; and the results already obtained have enabled the officers at the National Ob- servatory to construct a map^ of the basin of. the North Atlantic Ocean, which shows the depressions of the solid parts of the earth's crust below the sea-level, and which gives us, perhaps, as good an idea of the profile there as geographers have of the con- trasts afforded by the elevations of the land in the interior of Australia. 329. The deepest soundings ever reported were made in the North and in the South Atlantic Ocean. I^ieut. J. C. Walsh, commander U. S. schooner Taney, being furnished with a large quantity of iron wire made expressly for the purpose, obtained, on the 15th November, 1849, lat. 31° 59' N., long. 58° 43' W., a cast of the plummet, when after 34,200 feet had run out, the wire parted without reaching bottom, as it was thought. On the 12th of Feb., 1853, Lieut. Berryman, of the Dolphin, in lat. 32° 55' N., long. 47° 58' W., obtained a cast of the lead, using the small twine as a sounding line. At this trial 39,600 feet ran out, when the line parted, and it was consequently thought that the plum- met had not reached the bottom. On the 5th of April, 1852, lat. 36° S., long. 440 IP W., Lieut. Parker, of the U. S. frigate Congress, using a 32 lb. cannon ball for his plummet, and sound- ing twine like that of Berryman's, made an experiment at deep- sea soundings, when 49,800 feet of line ran out before it parted. The time occupied for this sounding was eight hours and a quarter. 330. The next great sounding was made by Capt. Denham, of Questions.— S28. With what are most of the vessels of the navy provided ? Results ob- tained ? 329. When have the deepest soundings been made ? Give particulars of the sounding made by Lieut J. C. Walsh. By Lieut. Berryman. By Lieut. Parker. 830. By Capt Denham. What is thought of these soundings by the light of subsequent experiments ? 1Q4: DEPTH OF THE OCEAN. * H. M. ship Herald, 30th October, 1852, lat. 36° 49^ S , long. 37° 06' W., with 46,236 feet. He had been furnished with sounding twiue from the U. S. frigate Congress, and instead of a 32 lb. shot, his sinker was a 9 lb. lead. By the light which subsequent experience has thrown upon the subject of deep-sea soundings, all four of these immense depths have had their ac- curacy questioned, and it is believed with reason. 331. An instrument has been invented by Passed Midshipman J. M. Brooke, of the U. S. Navy, which enables the officers who now attempt deep-sea soundings to detach the plummet from the line the moment it strikes the bot^pm, and then to haul up, at- tached to the line, specimens of the bottom. In this way speci- mens have been obtained from the depth of 12,000 feet,(about 2^ miles). These specimens have been examined with a microscope by Prof. Bailey at West Point, and found to consist entirely of minute sea-shells, not a particle of sand or gravel, or any foreign matter being among them. 'From this it is inferred that the wa- ter at the bottom of the sea is comparatively at rest. 332. The deepest part of the North Atlantic Ocean is prob- ably a little to the south of the Grand Banks of Newfoundland. There is a place there somewhat in the shape of a boot, which none of the officers of the navy have so far been able to fathom. The deepest soundings that have been satisfactorily made show that, in all other parts, the North Atlantic Ocean is not more than 25,000 feet in depth. The soundings which have been made by the navy have established the fact that there is a pla- teau, or shelf^ at the bottom of the ocean between Newfoundland and Ireland, quite shallow enough for the wires of a submarine telegraph, and quite deep enough to keep, them beyond the reach of icebergs. Questio7is.—3Sl. How have specimens of the bottom of the ocean been obtained ? Of what have these specimens been found to consist? 332. Where is the deepest part of the North Atlantic supposed to be? What do the soundings show with respect to the depth of the North Atlantic ii* all other parts? What other important fact has been established by these soundings ? WAVES OF THE OCEAN. 105 LESSON XV. THE OCEAN — (continued). 333. The ocean is subject to a motion of three different kinds : it is agitated by the action of the wind, producing waves ; by tides, which result from the attraction of the moon and sun ; and by currents, produced under various circumstances, and resulting from a variety of causes. 334. Waves are produced by the action of the winds on the surface of the water, and vary in size from mere ripples to enor- mous billows. Their height in open seas depends upon the force and duration of the wind, and the angle at which it bears down upon the waters ; but in lakes and bays it is affected by the shallowness of the waters and the character of the shores ; on which account the shallow waters of Lake Erie are more readily disturbed by winds than the deeper lakes, Ontario and Huron. 335. Waves are not, as appearances would indicate, an on- ward flow of water. This is proved from the fact that a floating body merely rises and falls with very little or no progression. Waves agitate the water but a little way below the surface, and it is supposed that the effect of the strongest gales does not ex- tend below the depth of 200 feet. 336. The crest of a wave (b, h) is the ridge or highest part, and in strong winds is usually covered with foam ; the trough i I (c) is the depression between two waves, and is as much be- low, as the crest is above, the general level of the ocean. In estimating the elevation of a wave, the perpendicular height from the trough to the crest is taken. 337. Waves are sometimes said to run mountains high, but this is a popular exaggeration The highest rise noticed in the Mediterranean is 16 feet, and 20 feet off Australia. During a Questions. — 333. What are the three different kinds of motion to which the ocean is subject ? 334. How are waves produced, and how do they vary ? Upon what does their height depend ? How is the height affected in lakes and bays ? 335. How is it proved that waves are not an onward flow of water ? 336. What is the crest of a wave ? The trough? 337. Give instances to show the height of graves. 5* 106 TIDES OF THE OCEAN. * storm in the Bay of Biscay, the highest waves measured scarcely 36 feet from the base to the summit. In the South Atlantic the result of several experiments gave only an entire height of 22 feet, and a velocity for the undulations of 89 miles per hour, the interval between each wave amounting to 1,910 feet. Off the Gape of Good Hope, notoriously the cape of storms, according to its former name, 40 feet is considered the extreme height of waves, or 20 feet above and below the general level of the ocean,* 338. The sea does not regain its placidity immediately after the subsidence of the winds which set it in motion, but continues to heave with mighty undulations for a considerable time after- ward. This movement is called the " swell." It frequently oc- curs, that while the swell is advancing in one direction, the wind rises from an opposite quarter, producing a series of compound waves, and giving to the deep a very complex aspect. 339. Tides are those regular alternate risings and fallings of the waters of the ocean and of bays, rivers, etc., which commu- nicate freely with it. They arise from the attractive influence of the sun and mcon, the latter being the more powerful agent. The sea rises, or flows, as it is called, by degrees, about six hours ; it remains stationary about a quarter of an hour ; it then retires, or ebbs, during another six hours, to flow again after a brief repose. Thus high and low water occur twice every lunar day, or the period elapsing between the successive returns of the moon to the meridian of a place, which is 24 hours 50| minutes, 340. The theory of the tides may be thus explained : Let E represent the earth surround- ed by water in every part, and m the moon. As a solid body draws toward it any other body, by a force which varies with its distance from the point attracted, then the water QuesUoTis.—^^. What is the movement of the sea called which continues after the sub- sidence of the winds? How are compound waves produced? 339. What are tides? From what do they arise? Describe the successive movements of the sea. 840. How may the theory of the tides be explained? * Rev. Thomas Milner. TIDES OF THE OOEAlf. lOT at a will be more powerfully attracted than those at e and/, and the result will be a bulging out of the water at a, immediately next the lunar body. 341. But while high water is thus produced at a, it is also produced at the same time in the opposite hemisphere at d. Different causes have been assigned for this phenomenon, but it is probably likewise owing to the attractive influence of the moon. The earth's center, E, will be more powerfully drawn toward the moon than the waters at d, and recede from them, producing the same effect as though they receded or rose up from the center of the earth. As the waters can not rise in one place without fall- ing in another, they are depressed at e and/" when elevated at a and d. 342. If the earth remained stationary upon its axis, there would be two elevations and depressions of the waters in each place in a month, or the time the moon is making her circuit round the earth. But by the diurnal rotation, the moon passes every day the meridian of every part of the globe, producing daily two seasons of high and low water. 343. The time of high tide does not coincide with the time when the moon is on the meridian of the place, a period of sev- eral hours ordinarily intervening between the time of the moon's transit and that of high water. The explanation of this is, that the water, having received motion, continues to rise after the moon has passed from its meridian, the impulse continuing for some time after the moon's transit. 344. Besides the attraction of the moon, the influence of the sun is concerned in elevating the waters of the ocean. The solar attraction is not so strong as the lunar, because, though a much larger body, the sun is at a far greater distance from the earth. The tidal influence of the sun has been calculated to be about one third that of the moon. 345. Sometimes the sun and moon act in conjunction, as at Questions. — 341. Explain how high water will be produced in the hemisphere oppo- site the moon. 342. What would happen if the earth remained stationary ? What occurs by the diurnal rotation? 343. What is said of the time of high water? How explained? 344. What is said of the influence of the sun on the tides ? 345. When do the spring-tides occur ? The neap-tides ? 1^^ TIDES OF THE OCEAN, the seasons of new and full moon, a and d, and then the tides rise the highest, and are called spring-tides; but when the moon is in quadrature, as at b and c, it acts in opposi- tion to the sun, and then oc- cur the lowest, or neap-tides. 346. Though high tides oc- cur in open seas soon after the moon has passed the meridian, yet in other places shoals and channels, peninsulas and capes, and the diversified form of shores, so retard the progress of the undulation, that high water happens at all distances of the moon from the meridian, and con- sequently at all hours of the day. Differences of local situation cause great differences as to the height to which the tide rises. In the central parts of the ocean the height is comparatively small, seldom exceeding three feet, but in rushing up contracted chan- nels the tide-water frequently causes a difference of twenty, thirty, and sixty feet between high and low water mark. 347. The cradle of tides is supposed to be that part of the Pacific Ocean to the southeast of Australia. Proceeding from this quarter, a wave advances into the Indian Ocean, reaching the island of Sumatra, the southern point of Hindoostan, the island of Madagascar, and the Cape of Good Hope about the same time. (See map No. 1.) 348. Entering the Atlantic, the wave proceeds northerly and westerly, bringing high water successively to all parts on the western shores of Africa, and eastern shores of America. It moves with much greater rapidity through the central parts of the ocean than along the coast — in consequence of which it reaches the islands of Cuba and Newfoundland, and Cape Blanco in Africa, simultaneously. The Atlantic coast of the United Questions.— Z'iQ What serve to retard the progress of the undulation ? What is said of the differences of local situation in aflFecting tides ? Illustrate. 84T. What is supposed to be the cradle of the tides ? Describe the movements of a wave proceeding from this quarter. Its progress after entering the Atlantic Ocean. What three points are reached i^multaneously ? TIDES. 109 States receives the wave from the east, while the western coast of Europe receives it from the west, the direction, in the latter case, being nearly the reverse of what it had previously to doubhng the Cape of Good Hope. 349. Along the shores of South America, from Rio Janeiro to the Falkland Islands, a wave advances from east to west, bring- ing high tide later on going southward, as if the wave came from the north. On the western coast of South America the tide travels from north to south, between the Gulf of Panama and the Strait of Magellan. And on the same side of North America, it travels from the Gulf of Panama, northward to Queen Char- lotte's Sound 350. The height to which tides rise varies greatly in different places. At St Helena the rise does not exceed three feet; at St. Male's, on the north coast of France, the spring tides rise 50 feet ; at Chepstow, on the British Channel, 60 feet ; and in the Bay of Fundy, between Nova Scotia and New Brunswick, it is known to rise 70 feet. On some occasions the rapidity of the waters is so great as to overtake animals feeding on the shores. TIDE TABLE FOR THE COAST OF THE UNITED STATES.* Portland Boston New Bedford Harbor. Newport New Haven New York Old Point Comfort.... Baltimore Smittiville Savannah Key West Interval between time ot moon's tian" sit and time of higli water. Mean. H. u. 11 25 11 22 7 57 7 45 11 16 8 13 8 17 IS 33 7 19 8 13 9 22 Dif. betw. greatest and least 44 44 41 24 1 8 46 50 43 47 51 1 12 Else and Fall. Mean. Feet. 10-1 3-8 3-9 5-8 4-3 2-5 1-3 4-5 6-5 14 Spring. Feet. 10 131 4-6 4-6 6-6 5-4 1-5 5-5 7-6 2-3 Neap. Feet. 7-6 7-4 2-8 3-1 5-1 0-9 5-5 0-7 Mean Diir.'tion. Flood. H. M. 6 14 6 16 Ebb. H. M. 6 12 6 18 5 33 6 3 6 5 6 25 6 25 6 33 6 26 7 22 5 25 20 9 42 23 28 26 14 12 Qtiestions. — 349. What is the direction of the wave south of Eio Janeiro ? Describe its movements on the western coast of South America. On the western coast of North America. 350. Mention the height to which tides rise at different places. * The author is indebted for the above table to the kindness of A. D. Bache, Superin- tendent of the United States Coast Survey. 110 CUEEENTS OF THE OCEAN LESSON XVI. THE OCEAN — (continued). 351. Currents constitute the third oceanic movement. They consist of vast oceanic streams which keep up a perpetual circu- lation of the waters, transferring them from one hemisphere to another, — from the Pacific to the Atlantic, and to the Pacjfic again, — and from the polar seas to the warm regions of the torrid zone. 352. Currents are due to a variety of causes ; as the influence of tides and winds, — the evaporating power of the sun, — the expansion and contraction of water by heat and cold, — and the revolution of the earth upon its axis. 353. The effect of the rise and fall of tides in producing an alternate flowing of currents in opposite directions, is perceived in channels between islands, or between islands and the main- land. Thus, in the channel which connects Long Island Sound with the Harbor of New York, known as the East River, strong currents^ alternately prevail in opposite directions, as the tide ebbs or flows. 354. Evaporation by solar heat is another cause of oceanic currents. Large quantities of water raised from one tract of the ocean are transported to some other, where the vapor is condensed and falls in the form of rain ; this, in flowing back to restore equilibrium, causes sensible currents. A perpetual stream flows into the Mediterranean from the Black Sea through the Bospho- rus and the Hellespont, and another from the Atlantic through the Straits of Gibraltar. No counter, lateral, or submarine currents have been discovered sufficient to dispose of the quantity of wa- ter flowing inward ; hence the inference that the inward current goes to supply the waste caused by an enormous evaporation. 355. The expansion and contraction of water by heat and cold are, perhaps, the principal causes to which currents are due. -351. Of what do currents consist ? 352. To what are they due ? 353. Where 13 the eflfect of the rise and fall of tides in producing currents perceived? Example. 354. How does evaporation by solar heat operate to produce currents ? Mention what is said of the Mediterranean Sea. 355. What are perhaps the principal causes to which currents are due ? Explain hew they aflfect the currents. ARCTIC CtJRKENT. Ill Warm water is specifically lighter than cold, and when certain portions become heated, they rise by reason of their buoyancy above the general surface, and are replaced by surrounding colder and heavier fluid flowing in beside or beneath them. 356. The revolution of the earth upon its axis is still another powerful cause in producing currents, particularly those of the equatorial regions, which have ^commonly a westerly direction. The winds of tropical climates, which blow continuously, or during long periods in one direction, also lend their influence in afiecting this class of oceanic movements. 357. Currents may be classed into constant, periodical, varia- ble, counter, and drift currents. Constant currents are produced by the rotation of the earth, differences of temperature in the waters of the ocean, and other causes not yet fully understood. Periodical currents are principally due to the action of tides, though they are doubtless aff'ected somewhat by the land and sea breezes and monsoons. Variable currents are occasioned by tides, winds, and the melting of ice in the polar regions. Counter cur- rents are the streams that flow alongside or beneath, and in op- posite directions to, other currents. Drift currents are the effect of permanent and prevailing winds upon the surface of the sea, and a variety of other causes. 358. Arctic Current. — The north polar or Arctic Current, after passing round the North Cape of Europe, crosses the upper part of the Atlantic, running to the southwest till' it reaches the east coast of Greenland. It then traverses the narrow sea be- tween that country and Iceland, turns round Caps Farewell, the southern extremity of Greenland, and proceeds northward into Davis' Strait. It follows the eastern side of the strait as far to the north as Holsteinborg, in latitude 67°, where it abruptly turns to the west, and strikes the opposite shore of Cape Walsingham. From thence its course is southward to Labrador and the north bank of Newfoundland, where it meets the Gulf Stream. 359. The breadth of the Arctic Current is in some places from Questions. — 356. What other causes are instrumental in producing currents ? 357. How may currents be classed ? What are constant currents? Periodical currents ? Variable currents? Counter currents ? Drift currents? 358. What is the course of the north polar or Arctic Current previously to its reaching Cape Farewell ? After it turns round Capo Farewell ? 869. What is the breadth of this current ? Its velocity ? 112 EQUATORIAL CUKBENT. 250 to 300 miles. Its velocity varies, in different parts of its course, from eight or nine to fifteen or sixteen miles per day. The icy masses it bears along are supposed to be about two months in making the before-mentioned circuit from Cape Fare- well to the coast of Labrador. 360. This current is distinguished for the great amount of drift-wood which it floats along^ and casts upon the shores of Spitzbergen, Iceland, and other lands lying in its way. The masses of floating wood thrown upon the island of Jan Mayen often equal, it is said, the whole of the island in extent. It is supposed that this timber comes from the forests of Siberia, and is carried into the Arctic Ocean by the streams of Northern Asia. . 361. Recent observations in high northern latitudes show that the Arctic Current presents one of the most formidable difficulties in exploring the polar regions. Parry, who attempted to reach the north pole by means of boat-sledges and reindeer, traveled over the surface of the deep to nearly latitude 83°, which seemed to be the utmost limit of animal life. Here he found that when, according to his reckoning, he had traveled ten or eleven miles toward the north, he had actually gone four miles to the south, owing to the current. The success of the expedition was thus rendered hopeless. The two vessels of the Grinnell Expedition which were sent out, under the command of Lieut. De Haven, to search for Sir John Franklin, after having penetrated far into Wellington Channel, were inclosed firmly in the ice, and drifted backward through Baffin's Bay, a distance of not less than fifteen hundred miles, thus baffling one of the noblest and most humane enterprises ever undertaken. 362. Equatorial Current. — The most extensive movement of the ocean is that which proceeds from east to west, on each side of the equator, and is therefore called the Equatorial Current. This great oceanic current originates in the immense expanse of the Antarctic Ocean. It first moves in a northeasterly direction Qtiestions.—S&O. For wbal is it distinguished ? 361 . What do recent observations in high northern latitudes show ? Describe the attempt of Parry to reach the north pole. The drift of the two vessels of the Grinnell Expedition. 362. Which is the most extensive movement of the ocean, and what is it called? Where does it originate? Describe ita course. MEXICAN GULF STREAM. 113 until it reaches the western shores of South America; a small branch rounds Cape Horn, but the great stream flows along the American coast until it arrives off the shores of Peru ; it then turns toward the west, and in a belt 3,500 miles broad, moves westwardly through the Pacific. 363. On reaching the Indian Archipelago and Australia, it is divided into numerous smaller streams, and hence the variable currents prevailing in the Indian Ocean, which render navigation so dangerous. A large volume of water forces its way through the islands, and joins the great equatorial current which moves on toward the eastern coast of Africa. The greater portion of the stream flows round north of the island of Madagascar, and sweeps through the channel of Mozambique, after which, being joined by other currents from the east, it doubles Cape Horn and enters the bed of the Atlantic. 364. Proceeding northward along the western shores of Af- rica, it mingles with the Great Atlantic equatorial current which flows out of the Gulf of Guinea. The Equatorial Current, on reaching Cape St. Roque, the most eastern point of South Amer- ica, is separated into two branches. One proceeds southward along the coast of South America, and before reaching the mouth of the La Plata, it is turned toward the east, and under the name of the South Connecting Current, makes the circuit of the South Atlantic Ocean, entering the Indian Ocean 200 miles to the south of the Gape of Good Hope. 365. The other and principal branch, known by the name of the Guinea Current, is a direct continuation of the equatorial. It runs from off Cape St. Roque, across the mouth of the Amazon, and after skirting the low coast of Guiana, and passing through the Caribbean Sea, it enters the Gulf of Mexico, between the island of Cuba and the peninsula of Yucatan. 366. Mexican Gulf Stream. — This is the most powerful cur- rent known, and the most important in consequence of the extent Questions. — 363. What happens on its reaching the Indian Archipelago and Austra- lia V Describe its subsequent course until it reaches Cape Horn. CC4. Its course through the Atlantic. Where is it divided? What is the course of the southern branch? 365. What is the name of the other branch, and where does it run ? 366. What is said of the Mexican Gulf Stream ? Where does it originate ? Its velocity through the straits of Florida? Its subsequent course ? Its course after striking the banks of Newfoundland ? 114: MEXICAN GULF STREAM. to which it affects the navigation of the Atlantic. It originates in the Gulf of Mexico, the waters of which are characterized by a remarkably high temperature.* It pours forth at the rate of five miles an hour through the straits of Florida, and flows in a northeasterly direction along the whole coast of the United States, expanding in volume and diminishing in rapidity. On striking the banks of Newfoundland, it sets to the east, and trav- erses the basin of the Atlantic to the Azores, where it turns south and enters the Equatorial Current on the coast of Africa, and is conducted again to the west, to re-enter into itself in the Gulf of Mexico. Thus the waters of the Atlantic Ocean between the parallels of 11° and 43° constitute a whirlpool of prodigious ex- tent, by which a smgle particle of water describes a circuit of over 11,000 miles in the space of two years and ten months. 367. The Gulf Stream, as it issues from the straits of Florida, is a dark indigo-blue ; the line of junction between it and the green waters of the Atlantic, is plainly seen for hundreds of miles. This line is finally lost to the eye as the stream goes northj though it is preserved to the thermometer for several thousand miles. From observations made with the deep-sea thermometer, it has been ascertained that " the stream, as far as the banks of Newfoundland, flows through a bed of cold water, which cold water performs to the warm the office of hanks to a river."t Questions. — 367. What is the color of the Gulf Stream ? What fact has been ascer- tained respecting it ? * DiflFerent opinions have been formed, respecting the cause of the Gulf Stream. It is supposed by some, that the waters of the Mexican Gulf have a higher level than those of the Atlantic in consequence of the trade winds and the influx of the Equatorial Current; and that the current is merely the running offoi the water, in order to restore an equilib- rium. Accordingly, the stream has been likened to " an immense river descending from a higher level into a plain." But Lieut. Maury has very satisfactorily disproved this theory, and shown that, " instead of descending, its bed (the bed of the stream) represents the surface of an inclined plane from the north, up which the lower depths of the stream must ascend.?' In the absence of any better theory respecting the cause of this remarkable current, it is safe to assume that it is influenced much by the excessive temperature im- parted to the waters of the Gulf of Mexico. The course of the Gulf Stream has been as- signed to the difference in density between the waters of the Caribbean Sea and the Gulf of Mexico,-and those of the Baltic and the North seas. The waters of the former contain a larger proportion of salt, and are consequently heavier than common sea water ; while th"«e of the latter, being only slightly impregnated with saline matter, are much lighter than common sea water. This difference in density destroys the equilibrium and produces a current; "for wherever equilibrium be destroyed, it is restored by motion, and motion among fluid particles gives rise to currents, which, in turn, constitute circulation." f Lieut M. F. Maury. MEXICAN GULF STREAM. 115 368. Coming from the heated cauldron of the Gulf of Mexico, the waters of the Gulf Stream have a high temperature, which is gradually lost as they reach higher latitudes, " The maximum temperature of the Gulf Stream is 86°, or about 9° above the ocean temperature due the latitude. Increasing its latitude 10°, it loses 2° of temperature. And, after having run 3,000 miles toward the north, it still preserves, even in winter, the heat of summer. With this temperature it crosses the 40th degree of north latitude, and there, overflowing its liquid hanks, it spreads itself out for thousands of square leagues over the cold waters around, and covers the ocean with a mantle of warmth that serves so much to mitigate in Europe the rigors of winter. Moving now more slowly, but dispensing its genial influences more freely, it finally meets the British Islands, By these it is divided, one part going into the polar basin of Spitzbergen, the other entering the Bay of Biscay, but each with a warmth con- siderably above ocean temperature. Such an immense volume of heated water can not fail to carry with it beyond the seas a mild and moist atmosphere. And this it is which so much softens climate there."* Qxiest!ion8.—Z&%. What is said of its temperature ? What is its maximum or greatest temperature, and how many degrees is it above that due the latitude ? Describe how the Gulf Stream serves to moderate the climate of Europe. * Lieut. M. F. Maury PART III. THE ATMOSPHERE LESSON I. COMPOSITION OF AIR. TMOSPHERE is the name of that thin, transparent, and highly elastic fluid which surrounds the earth on every side, and ac- companies it in its diurnal rev- olution upon its axis and its annual motion round the sun. It is lighter than either land or water, and rises above them, but is kept by the force of gravity close to the surface of the earth, where its use is indispensable to all living creatures. It is the medium through which sound, light, and odor are transmitted ; it is the vehicle in which moisture is raised and diffused ; and the agent by which that diversity of color so pleasing to the eye is produced in natural objects. 370. Atmosphere is unlike the great divisions of land and water in not being perceptible to the touch unless in agitation. Its existence as a material substance is evident the moment it is set in motion. It not only carries away in its progress the lighter substances with which it comes in contact, but, when greatly agi- tated, uproots trees, crumbles rocks, and overturns buildings. Its motion is applied as a mechanical force, and as such is of vast use to man in wafting his vessels over the ocean. 371. The atmosphere is composed principally of two different Questions. — 869. Of what is atmosphere the name ? What is said of its lightness ? What else is remarked of it? 370. How is atmosphere unlike the great divisions of land and water? Its effects when in motion? Its motion how applied? 371. Of what is the atmosphere principally composed, and in what proportions? What other substances does it contain ? State the composition of 1000 parts of the atmosphere. COMPOSITION OF AIR. 117 gases, termed oxygen and nitrogen, the relative proportions being 21 parts of the former to 79 of the latter. It contains a small but variable proportion of aqueous vapor, and a still smaller proportion of carbonic acid gas. The proportions of oxygen and nitrogen are definite, but the amount of aqueous vapor fluctuates. Under ordinary circumstances, the composition of 1000 parts of the atmosphere may be stated as follows : Oxygen 210-0 Nitrogen 775-0 Aqueous vapor 14-2 Carbonic acid 0-8 1094-0 372. The same proportions of oxygen and nitrogen are found in the atmosphere of all countries, and at all elevations, over land and over sea, on the summit of the highest mountains and at their base, at the equator and in high northern and southern lati- tudes. The quantity of carbonic acid gas is, however, greater near the level of the sea in summer than in wmter ; greater during the night than the day ; and rather more abimdant on the summit of high mountains than on plains. 373. Oxygen and nitrogen are extremely different in their properties. Oxygen gas is a supporter of combustion, and is required for the support of animal life, while nitrogen, in its un- mixed state, is destructive to both. Without oxygen, fires would cease to burn, and all animals would immediately expire. By the process of breathing it is taken into the lungs and goes to purify the blood. When the bloo'd is brought into the lungs it is of a dark purple color, but it then throws off the hydrogen and carbon, and receives oxygen, which gives it a bright red color. A portion of the nitrogen that is received by the lungs appears to be absorbed, while the other and larger part is rejected and thrown back again into the atmosphere in which it immediately rises, being lighter than air. Questions. — 372. What is said of the invariable proportions of oxygen and nitrogen in common air? In what localities, and at what times, is the quantity of carbonic acid great- er? 373. What is said of oxygen gas? Of nitrogen gas? What would happen without oxygen ? What is the color of the blood when brought into the lungs ? What change . then takes place ? What becomes of the nitrogen received into the lungs ? 118 PROPERTIES OF THE ATMOSPHERE. LESSON II. PROPERTIES OF THE ATMOSPHERE. 374. The general properties of the atmosphere are transparency, fluidity, weight, and elasticity Transparency is that state or prop- erty it possesses by which ?^^i?r it suffers rays of light to pass through it, so that objects can be distinctly seen through it. The va- rious degrees of clearness ■ in the atmosphere are owing to particles of va- por and other substances which float in it. Distant objects sometimes appear twice as near as at others, a phe- nomenon occasioned by the differ- ence in the purity of the atmosphere, or its freedom from aqueous and other particles. 375. 'Qy ihe fluidity oi ihe atmo- sphere is meant that quality it possesses which renders it im- pressible to the slightest force, and by which the particles easily move or change their relative positions. Fluidity is a property common to liquid and aeriform substances. The atmosphere, like other fluids, presses in all directions, upward as well as downward, and is capable of supporting light bodies. 376. The air is ponderable, or has weight. The pressure or weight exerted upon every square inch of the earth's surface is equal to about 15 pounds. In consequence of its fluidity it Questions.— ^li. What are the general properties of the atmosphere ? "What is transpa- rency ? To what are the various degrees of clearness owing? Why do distant objects ap- pear sometimes twice as near as at others? 375. What is meant by the fluidity of the atmo- sphere? How does the atmosphere press? 376. What is the pressure or weight on every square inch of the earth's surface ? What pressure does the human body of the ordinary size sustain ? Why do we not feel the pressure ? PKOPERTIES OF THE ATMOSPHERE. 119 presses equally in every direction, and the human body, of the ordinary size (supposed to measure 15 square feet), sustains the enormous pressure of 31,536 pounds or 14 tons. We do not feel the pressure, owing to its acting uniformly on all sides, and because the air within our bodies perfectly counterpoises the ex- ternal pressure. 377. The weight of a column of the entire atmosphere is equal to that of a column of water of the same base about 34 feet high, or a similar column of mercury 30 inches high. The pressure diminishes as we ascend, according to a*scale, which is nearly certain. From numerous observations it has been ascer- tained that at the height of 3^ 2 7 4 10^ 8 , 14 miles above the level 16 17^ of the sea, the air is 32 21 64 24i 128 ■(_ 28 256 times lighter than at the earth's surface. 378. The pressure of the atmosphere is indicated by the barometer (the measure of weight), an instrument consisting of a column of mercury poised or pressed up into a vacuum by the weight of the atmosphere. The mercury rises or falls according to the pressure of the atmosphere, its range, at the level of the sea, being from about 28 to 31 inches. 379. The barometer is used for determining the height of mountains. At the level of the sea the pressure is greatest in consequence of the weight of all the superincumbent atmosphere, and hence at that point the highest column of mercury will be sustained ; but as we ascend, this superincumbent pressure is di- minished, and consequently the mercury falls. Thus, Humboldt, at the foot of Mount Chimborazo, found the barometer to stand exactly at 30 inches ; but on ascending the mountain to the ele- vation of 19,000 feet, it was very little higher than 14 inches. Questions.— SJ J. To -what is the weight of a column of atmosphere equal? 378. By what instrument is the pressure of the atmosphere indicated ? What is the range of the mercurial column at the level of the sea ? 379. For what is the barometer used ? Where will the highest column of mercury be sustained, and why? Why does it fall as we ascend ? What did Humboldt discover ? Lieut. Hemdon ? What have experiments proved ? 120 PEOPEETIES OF THE ATMOSPHERE. In the pass of Antarangra (one of the highest passes of the Andes), Lieut. Herndon found the barometer to stand at 16-73 inches, indicating an elevation of 16,044 feet. Experiments have proved that the mercury will fall about yL of an inch for every 100 feet of perpendicular height, or one inch for every 1,000 feet. 380. The density or pressure of the atmosphere is, by another method, made subservient to the measurement of heights ; name- ly, by observing the boiling point of water, which decreases in a ratio nearly equivalent to the decrease of atmospheric pressure. At the level of the sea, water boils, or passes into the state of steam, at 212° Fahrenheit, but at the Hospice of the Great St. Bernard, it boils at the lower temperature of 203°, and on the top of Mount Blanc, at 186°. In the pass of Antarangra, Lieut. Herndon found water to boil at 182° 5. From these and other observations, it may be inferred that a difference of one degree in the boiling point of water, as indicated by the common thermom- eter, answers very nearly to 550 feet of elevation. 381. The elasticity of the atmosphere is the property it pos- sesses of occupying less space under the influence of certain forces, and returning to its original volume when the influence is withdrawn. Hence its density is not uniform, but, as before explained, diminishes from below upward. The height of the atmosphere is not known, but it is supposed to extend to about fifty miles. By far the greater portion of it is within fifteen or twenty miles of the earth's surface ; and at a much less distance it becomes so rarefied as to be incapable of supporting life. 382. Travelers on high mountains have experienced sensible, and sometimes painful, proofs of the rarefied state of the air. In very elevated regions the thinness of the air diminishes the in- tensity of sound, renders breathing difficult, and produces a loss of physical strength. The blood burst from the ears and lips of Hum- Questions. — 3S0. By what other method may the density of the atmosphere be made subservient to the measurement of heights ? At what degree of Fahrenheit does water boil at the level of the sea ? At the Hospice of the Great St. Bernard ? On the top <.f Mount Blanc V In ihe pass of Antarangra? What elevation is found to answer the diflFerence of one degree in the boiling point ? 3S1. What is the elasticity of the atmosphere ? How- does its density diminish? What is the supposed height of the atmosphere? 382. What have travelers on high mountains experienced ? What effects are produced by the thin- ness of the air ? WINDS. 121 boldt in attempting to reach a high elevation in the Andes. He experienced the same difficulty in kindling and maintaining a fire at great heights, which Marco Polo felt on the mountains of Central Asia. In the high regions of the Andes a malady pre- vails, called veta, which is thus spoken of by Lieut. Herndon : " Veta is the sickness caused by the rarity of the atmosphere at these great elevations. The Indians call it veta, or vein, be- cause they believe it is caused by veins of metal diffusing around a poisonous mfection. The affection displays itself in a violent headache, with the veins of the head swollen and turgid, a diffi- culty of respiration and cold extremities." LESSON III WINDS. 383. The atmosphere remains at rest so long as its density is unchanged ; but, as soon as the equilibrium is broken by any cause whatever, a motion occurs, which is called wind. If, in one part of the atmosphere, the air becomes dense, it passes away to those parts where the density is less, in the same man- ner as air, compressed in a pair of bellows, escapes by the orifice. We may compare this displacement of air to that of water in rivers ; it is a flowing of the aerial ocean from one region toward another. 384. The currents of the atmosphere perform many invaluable services to man. They renew the air of cities ; and they miti- gate the climates of the north by bringing to them the heat of the south. They transport the clouds from the sea to the interior of continents, thus aiding to fertilize regions which would other- wise become arid and uninhabitable. They waft the sails of the navigator around the globe, bring distant nations into familiarity, and are thus greatly instrumental in the diffusion of civilization and Christianity throughout the world. Questions. — 3S3. How long does the atmosphere remain at rest? What occars when this equilibrium is broken ? If in one part of the atmosphere the air becomes dense, what follows? To what may this displacement of the air he compared? 3S4. Describe the uses of the atmospheric currents. 6 122 vv^INDS. 385. To indicate the direction of the wind the horizon is divided into eight equal parts, and the wind is designated by giving it the name of the points of the horizon whence it blows. The eight kinds of winds are north, north-east, east, south-east, south, south-west, west, and north-west. It is customary to write merely the initial of these words, that is : N., N. E., E., S. E., S., S. W., W., N. W. 386. The general direction of the wind near the surface of the earth is indicated by vanes. They are commonly placed on ele- vated buildings, such as steeples, towers, etc., so that small va- riations, resulting from accidents of the ground, may not have any action on them. Clouds indicate the direction of the upper aerial currents ; and show that it differs very often from the direction of the wind on the surface of the earth. 387. That the direction of the wind in the upper regions is often the reverse of what it is in the lower, has been conclu- sively proved. During an eruption of the volcano of St. Vincent in 1812, the ashes were conveyed in great quantities to the island of Barbadoes, situated to the east. These islands lie in the range of the trade-winds, which blow from the east toward the west ; but the ashes, having been launched into the air as high as the region of the upper current, were transported by it in the direction from west to east. At the summit of the Peak of Teneriife almost all travelers have found west winds, while east winds prevail at the level of the sea. On the 25th of Feb- ruary, 1835, the ashes emitted from the volcano of Coseguina, in the state of Guatemala, obscured the light of the sun for five days ; they rose into a high region of the atmosphere, and fell a short time afterward in the streets of Kingston, in Jamaica, which is situated to the N. E. of Guatemala, the winds near the surface all the while blowing toward the S. W. Questions. — 885. Into how many parts is the horizon divided to indicate the direction of the wind ? How is the wind designated ? What are the eight kinds of winds? Their initials? 3S6. How is the general direction of the winds near the surface of the earth Indicated? Where are they commonly placed, and why? What do clouds indicate? 887. What is said of the reverse direction of upper and under currents ? Of the eruption of the volcano of St. Vincent? What have travelers found at the summit of the Peak of Tenerlffe ? What further illustration of this fact was afforded by the transportation of ashes emitted from the volcano of Coseguina ? The UgJvt waved, tinea wMdh- cro.vs t>%e,Ma.p front JSchst to 'West, are Isotherms [or lines of equal mean, temp eraiturei and tAe figia-es attuclied to eadhjnarlc the , ircmiiuzl heat.whic/zit rep?-e.fents.ana wfurh istjiesarn^ in all planes. 13irongl\ whirh it passe.9 . F-T^tsred, acr.Lrraznj -co^Act erf tm^ess.zr^ rjiexearl. k Co ir. t3u- uerrcs Office ,?'rheD:st:-'^ lczct rr'i,.. VARIABLE WINDS. 123 388. Daily experience teaches us the unequal force of the wind, exhibiting every conceivable variety, from the almost in- sensible breeze, to the hurricane which prostrates the monarch of the forest. The following facts respecting the velocity and force of winds have been ascertained : Velocity of the Perpendicular force on wind in miles one square foot in pounds Characteristics. per hour. avoirdupois. 1 -005 Hardly perceptible. 2 '020 Just perceptible. 5 '123 Gentle, pleasant 'wind. 10 -492 Brisk gale. 20 1-968 Very brisk. 30 4-429 High wind. 40 7-873 Very high wind. 60 12-300 A storm. 60 17-715 A violent storm. 80 31-490 Ahurricane. 100 49-200 A violent hurricane. 389. Winds may be divided into three classes, — Variable, Per- manent, and Periodical. 390. Variable Winds. — Variable winds, as their name indi- cates, are very irregular as to time, direction, and force, and seldom continue to blow for many days. They prevail in the Temperate and Frigid zones, those of the Torrid zone being, :uf the most part, either permanent or periodical. 391. We are not fully acquainted with the causes which pro- duce these partial and ever-fluctuating aerial currents, but there is no doubt that they are mainly due to the unequal states of the temperature of land and sea. Although these winds alternately come from every point of the compass, changin'g frequently from one point to the opposite in a very short space of time, it has been observed that diff'erent seasons are characterized by winds from different directions. Franklin long ago observed in North America, that in summer the winds come from the south and in winter from the north. Questions. — 388. What is said of the unequal force of the wind ? Describe the force, and mention the characteristic, of wind having a A'elocity of 1 mile per hour. 2 miles per hour. 5 miles per hour. 10 miles per hour. 20 miles per hour. 30 miles per hour. 40 miles per hour. 50 miles per hour. 60 miles per hour. SO miles per hour. 100 miles per hour. 389. Into what three classes may winds be divided ? 390. What are variable winds? Where do they prevail ? 391. To what are they no doubt mainly due? What has been observed respecting them ? What did Franklin observe? 124 VARIABLE WINDS. 392. From numerous observations made in different parts of Europe, the following laws have been established : In winter, the direction of the wind is principally from the south, its force being greatest in January. In spring, east winds are common at certain places in March, and at other places in April. In sum- mer, especially in July, the winds blow chiefly from the west, and in autumn the south winds more frequently blow, particularly in October. 393. Designating the total number of winds that blow in a given time by 1000, the following Table shows their relative fre- quency in the countries named : Countries. N. N. E. E. S. E, S. S. "W. W. W. "W. North America.. 96.. ..116.. .. 49.. ..108.. ..123.. ..197.. ..101.. ..210 England 82.. ..111.... 99.... 81. ...111.. ..225.. ..171.. ..120 France 126.. ..140.. .. 84.... 76.. ..117.. ..192.. ..155.. ..110 Germany 84.... 98... .119.... 87.... 97.. ..185.. ..198.. ..131 Denmark 65.... 98.. ..100.. ..129.... 92.. ..198... .161.. ..156 Sweden 102.. ..104.. .. 80.... 110.. ..128.. ..210... .159.... 106 Prussia 99.. ..191.... 81.. ..130. .. . 98.. ..143.. ..166.. ..192 394. There is a certain class of variable winds known to pos- sess peculiar properties, such as the hot winds felt on the north- ern coast of Africa, in Persia, India, and China, the cold winds of Siberia, the pestilential simoon or samiel of Africa, Arabia, and Mesopotamia, etc. Winds partake of the property of the regions from which they come ; thus, in Europe the west winds which blow from the Atlantic are more moist than the east, which sweep over the continent. On the Atlantic coast of the United States, the winds which come from the northeast are remarkable for their chilliness, and for the disagreeable storms which accompany them. Variable winds may be subdivided into cold and hot winds. 395. The cold winds of the north temperate zone are those which blow from the north and northeast. In Europe the north- east winds are cold, deriving their character from the very low temperature which prevails in northern Europe and Asia. In .—892. What is the general direction of the winds of Europe in winter? In spring ? In summer ? In autumn ? 394. What is said of the properties of certain winds? Of the west winds in Europe ? Of the northeast winds on the Atlantic coast of the United States ? How may variable winds be subdivided ? 395. What is said of the cold winds of the north temperate zone ? Of the northeast winds in Europe ? Of the north winds in the south of Europe ? THE SIMOON. ' 125 the south of Europe the north winds are of great violence and severity, owing to the contrast between the snow-covered Alps and the elevated temperature of the Mediterranean. 396. The bora, a northeast wind, so called in Istria and Dalmatia, is sometimes so furious as to overturn horses at plow. The mistral and the vent de bise are winds which prevail in the southeast of France. The mis- tral blows from the northwest, descending from the mountains of Central France, and sweeping over the ancient provinces of Provence and Langue- doc, where it is supposed to contribute greatly to the salubrity of the air, by dispelling the exhalations from the marshes and stagnant waters common in that region of extensive levels. It is very fearful in the Gulf of Lyons ; hence the name of that gulf, not derived, as commonly imagined, from the city of Lyons, but from the lion-like violence of its tempests. The vent de bise (black wind) is a cold, piercing current from the Alps and the mount- ains of Auvergne, which chiefly follows the course of the Rhone, in the val- ley through which it runs, rendering the climate in winter very severe. In Spain, a north wind, called the gallego, is of a very formidable character. 397. Hot winds are very frequent in countries contiguous to the tropical regions. Large deserts and plains, covered with little vegetation, engender very warm winds ; these winds, which are of a noxious character, prevail in the vast deserts of Asia and Africa, where they show themselves in all their force. Nubia, Arabia, Persia, and other parts of Asia, are visited by a burning wind peculiar to the desert. In Arabia it is called samoun, from the Arabic samma, which signifies hot and poisonous. It is also named samiel, from samm, poison. In Egypt it is called cham- sin (fifty) because it blows for fifty days, from the end of April until June, at the commencement of the inundation of the Nile. In the western part of the Sahara it is named harmattan. 398. The Simoon is announced by the troubled appearance of the horizon ; afterward the sky becomes obscured, and the sun loses its brilliancy, — paler than the moon, its light no longer pro- jects a shadow ; the green of the trees appears of a dirty blue, the birds are restless, and the affrighted animals wander in all directions. The rapid evaporation occurring at the surface of the human body dries the skin, inflames the throat, accelerates Questions. — 396. What is said of the liora ? The mistral ? The vent de liise ? 397. Where are hot winds very frequent ? By what name is the burning wind called in Ara- bia? By what other name is it known? What is it called in Egypt, and why? In the western part of Sahara ? 398. How is the simoon announced ? How does it affect the human body ? 126 THE siarooN, respiration, and causes a violent thirst. The water contained in the skins evaporates, and the caravan is a prey to all the horrors of thirst. 399. This hot wind is deleterious in its mildest forms, occasionally de- structive, and many a pilgrim to the shrine of the prophet at Mecca, and merchant to the marts of Bagdad, have perished by its noxious, suffocating influence. Bruce suffered from it when ascending the Nile, he and his com- pany becoming so enervated as to be incapable of pitching their tents, op- pressed as well by an intolerable headache. " The poisonous simoon," he remarks, when at Chendi, " blew as if it came from an oven ; our eyes were dim, our lips cracked, our knees tottering, our throats perfectly dry ; and no relief was found from drinking an immoderate quantity of water. 400. " In June, 1813," says Buckhardt, " in going from Siout to Esne, I was surprised by the simoon in the plain which separates Furschiout from Berdys. When the wind arose I was alone, mounted on my dromedary, and at a distance from every tree and habitation. I endeavored to protect my face by wrapping it in a handkerchief. Meanwhile, the dromedary, into whose eyes the wind drove the sand, became restless, commenced galloping, Storm .a i-n-i Dc-.sci't. and caused me to lose the stirrups. I remained lying on the earth without moving from the spot, for I could not see to a distance of ten metres, and I wrapped myself up in my clothes until the wind had abated. I then went in search after my dromedary, which I found at a very great distance, lying down near a bush that protected his head against the sand raised by the wind." QuefiUons.—S99. What further is remarked respecting this hot wind ? How did Bruce suffer from it ? What does he say of it ? 400. Mention some of the particulars related by Buckhardt. THE SIMOON. 127 401 . Volney gives the following complete account of the simoon and its eflfects : " Travelers," he states, " have mentioned these winds under the name of poisonous winds ; or, more correctly, hot winds of the desert. Such, in fact, is their quality ; and their heat is sometimes so excessive that it is difficult to form an idea of their violence without having experienced it ; but it may be compared to the heat of a large oven at the moment of draw- ing out the bread. When these vrinds begin to blow, the atmosphere as- sumes an alai..iing aspect. The sky, at other times so clear in this climate, becomes dark and heavy ; the sun loses its splendor, and appears of a violet color. The air is not cloudy, but gray and thick ; and is in fact with an extremely subtile dust, that penetrates everywhere. 402. " This wind, always light and rapid, is not at first extremely hot, but it increases in heat in proportion as it continues. All animated bodies soon discover it by the change it produces in them. The lungs, which a too rarefied air no longer expands, are contracted and become painful. Respi- ration is short and difficult, the skin parched and dry, and the body con- sumed by an internal heat. In vain is recourse had to large drafts of wa- ter ; nothing can restore perspiration. In vain is coolness sought for ; all bodies in which it is usual to find it deceive the hand that touches them. Marble, iron, water, notwithstanding the sun no longer appears, are hot. The streets are deserted, and the dead silence of night reigns everywhere. The inhabitants of townc and villages shut themselves up in their houses — and those of the deserts in their tents, or in pits they dig in the earth — where they wait the termination of this destructive heat. 403. " It usually lasts three days, but if it exceeds that time it becomes insupportable. Woe to the traveler whom this wind surprises remote from shelter ! he must suffer all its dreadful consequences, which sometimes are mortal. The danger is most imminent when it blows in squalls, for then the rapidity of the wind increases the heat to such a degree as to cause sudden death. This death is a real suffocation; the lungs, being empty, are con- vulsed ; the circulation disordered, and the whole mass of blood, driven by the heat toward the head and breast ; whence that hemorrhage at the nose and mouth which happens after death. 404. "This wind is especially fatal to persons of a plethoric habit, and those in whom fatigue has destroyed the tone of the muscles and vessels. The corpse remains a long time warm, swells, turns blue, and is easily sep- arated ; all of which are signs of that putrid fermentation which takes place when the humors become stagnant. These accidents are to be avoided by stopping the nose and mouth with handkerchiefs ; an efficacious method is also that practiced by the camels, who bury their noses in the sand, and keep them there till the squall is over. Questions. — 401. What does Tolney say respecting these winds? To what does he com- pare iheir heat ? What is the aspect of the atmosphere during the continuance of the simoon ? 402. What changes does it produce on all animate bodies ? 403. How long does it usually last? "When is the danger most imminent? 404. To whom is the wind espe- cially fatal ? 128 HARMATTAN, SIKOCOO. 405. "Another quality of this wind is its extreme aridity, which is such, that water sprinkled upon the floor evaporates in a few minutes. By this extreme dryness it withers and strips all the plants, and by exhaling too suddenly the emanations from animal bodies, crisps the skin, closes the pores, and causes that feverish heat which is the invariable effect of sup- pressed perspiration." 406. The Harmattan blows from the northeast, over Sene- gambia and Guinea, to that part of the coast of Africa lying be- tween Cape Verde, in 15° north latitude, to Cape Lopez in 1° south latitude, a coast line of upward of two thousand miles. It occurs during December, January, and February, generally three or four times during that season. It comes on at any hour of the day, at any time of the tide, or at any period of the moon, continuing sometimes only a day or two, at other times five or six days, and it has been known to last upward of a fortnight. 407. Extreme dryness is the property of this wind ; — all veg- etation droops and withers, and should the harmattan blow for several days, the leaves of the lemon, orange, and lime-trees become so parched that they may be readily rubbed into dust. Even* household furniture cracks, and in many instances flies to pieces. Though this wind is so pernicious in its effects upon vegetable life, yet it is conducive to the health of the human species, by removing dampness from the atmosphere, and coun- teracting its effects after a long rainy season. 408. The Sirocco is a hot southeast wind, prevailing in the Mediterranean, in Italy and Sicily, but felt most violently in the country around Naples, and at Palermo. It sometimes com- mences about the time of the summer solstice, but blows occa- sionally with grieat force in the month of July. Though usually attributed to the Sahara, it is supposed by some to arise on the arid rocks of Sicily ; and hence is far more violent on the north than on the south coast of the island, about Palermo, and also in the neighborhood of Naples. 409. It is thus described by a traveler during his stay at Palermo : " On Sunday, July 8th, we had the long-expected sirocco wind, which, although our expectations had been raised pretty high, yet I own greatly Questions. — 105. What other quality does this wind possess? Give particulars. 406. Describe the Harmattan. When does it occur? What is said of its irregularity, etc.? 407. What is the property of this wind ? What are its efiFects on bodies ? On the human Bpecies ? 408. What is the Sirocco ? When does it blow ? Its supposed origin ? SALANO. 129 exceeded them. Friday and Saturday were uncommonly cool, the mercury never being higher than 725° : and although the Sirocco is said to have set in early on Sunday morning, the air in our apartments, which are very large, with high ceilings, was not in the least affected by it at eight o'clock, when I rose. I opened the door without having any suspicion of such a change ; and indeed I never was more astonished in my life. The first blast of it on my face felt like the burning steam from the mouth of an oven. I drew back my head and shut the door, calling out to Fullarton that the whole atmosphere was in a flame. However, we ventured to open another door tliat leads to a cool platform, where we usually walk ; this was not ex- posed to the wind ; and here I found the heat much more supportable than I could have expected from the first specimen I had of it at the other door. It felt somewhat like the subterraneous sweating-stoves at Naples, but still much hotter. In a few minutes we found every fiber greatly relaxed, and the pores opened to such a degree, that we expected soon to be thrown into a profuse sweat. 410. " I went to examine the thermometer, and found the air in the room as yet so little affected that it stood only at 73°. The preceding night it was at 721°. I took it out to the open air, when it immediately rose to 110°, and soon after to 112°; and I am confident that in our old lodgings, or any- where within the city, it must have risen several degrees higher. The air was thick and heavy, but the barometer was little afiected : it had fallen only about a line. The sun did not once appear the whole day, otherwise I am persuaded the heat must have been insupportable ; on that side of our platform which is exposed to the wind, it was with difficulty we could bear it for a few minutes. Here I exposed a little pomatum, which was melted down as if I had laid it before the fire. I attempted to take a walk in the street, to see if any creature was stirring, but I found it too much for me, and was glad to get up stairs again. This extraordinary heat conMnued till three o'clock in the afternoon, when the wind changed at once, almost to the opposite point of the compass. All nature languishes under the influ- ence of this wind ; vegetation droops and withers ; the Italians suffering from it not less than strangers. When any feeble literary production ap- pears, the strongest phrase of disapprobation they can bestow is, " It was written in the time of the sirocco." 411. The deserts of Asia and Africa are the regions in which the hot or burning winds prevail ; but in Spain, the Solano, a wind which is supposed to arise on the plains of Andalusia, throws the majority of individuals into a condition of peculiar languor. In India, which is covered with a rich vegetation, and in Chile, in Louisiana, and in the great level plains [Llanos) of the Orinoco, there are certain local winds of a very elevated temperature. QuesU(ms.—4\\. What is said of the deserts of Asia and Africa ? Of the Salano? Where do ©ther very warm winds prevail ? 6* 130 TKADE-WINDS LESSON IV. PERMANENT WINDS. 412. The Trade-winds are those permanent breezes which prevail within the tropics, and which maintain nearly the same direction and rate throughout the year. Their direction is from the northeast in the northern hemisphere, and from the southeast south of the line ; but it is more decidedly from the east as the equator is approached. They extend generally from about 28° to 30° on each side of the equator, but their limits vary consid- erably as the sun is north or south of the equator ; their external and internal boundaries are also very different in the Atlantic and Indian oceans. It is only over the wide ocean that the trade-winds can blow uninterruptedly. Between them is a zone A Calm at Sea. styled the Region of Calms, in which thick, foggy air prevails, with frequent sudden and copious rains, attended by thunder and lightning. 413. The trade-winds may be thus explained. The regions bordering on the equator are the hottest on the earth. In con- sequence of rarefaction, the air there ascends and flows over the colder masses on either side toward the poles, from which a Questions. — 412. What are the trade-winds? What is their direction? Their limits? What region lies between them ? 413. How may the trade-winds be explained ? TKADE-WINDS. 131 polder atmosphere moves to supply its place. Thus two currents are created in each hemisphere, an upper and a lower, but flow- ing in opposite directions. If the earth did not rotate on its axis, the lower current in the northern hemisphere, or the trade- wind, would be from north to south, and in the southern hemi- sphere from south to north. The earth, however, rotates from west to east, and the atmosphere surrounding it partakes of this rotary motion, — hence these winds become northeast and south- east. 414. The movements of the trade-winds, and the laws by which they arc governed, are very clearly explained in the following article, by Lieut. Maury : " From the parallel of about 30° north and south, nearly to the equator, we have two zones of perpetual winds, viz. : the zone of northeast trades on this side, and of southeast on that. They blow perpetually, and are as steady and as constant as the currents of the Mississippi River — always moving in the same direction. As these two currents of air are constantly flowing from the poles toward the equator, we are safe in assuming that the air which they keep in motion must return by some channel to the place near the poles, whence it came in order to supply the trades. If this were not so, these winds would soon exhaust the polar regions of atmosphere, and pile it up about the equator, and then cease to blow for the want of air to make more wind of. 415. " This return current, therefore, must be in the upper regions of the atmosphere, at least until it passes over those parallels between which the trade-winds are always blowing on the surface. The return current must also move in the direction opposite to the direction of that wind which it is intended to supply. These direct and counter-currents are also made to move in a sort of spiral curve, turning to the west as they go from the poles to the equator, and in the opposite direction as they move from the equator toward the poles. 416. " This turning is caused by the rotation of the earth on its axis. The earth, we know, moves from west to east. Now if we imagine a par- ticle of atmosphere at the north pole, where it is at rest, to be put in motion in a straight line toward the equator, we can easily see how this particle of air, coming from the pole, where it did not partake of the diurnal motioif of the earth, would, in consequence of its vis inertia, find, as it travels south, the earth slipping under it, as it were, and thus it would appear to be coming from the northeast and going toward the southwest : in other words, it would be a northeast wind. Questions. — 414. Where have we two zones of perpetual winds ? What are we safe in assuming ? Why ? 415. Where must this return current be ? Which way do the direet and counter-currents turn ? 416. How is this turning caused ? Explain. 132 TRADE-WINDS, Diagram, of tlie Trade--wmds. 417. " On the other hand, we can perceive how a like particle of atmos- phere that starts from the equator, to take the place of the other at the pole, would, as it travels north, in consequence of its vis inertia, be going toward the east faster than the earth. It would, therefore, appear to be blowing from the southwest, and going toward the northeast, and exactly in the opposite direction to the other. Writing south for north, the same takes place between the south pole and the equator. Now this is the pro- cess which is actually going on in Nature ; and if we take the motions of these two particles as the type of the motion of all, we shall have an illus- tration of the great currents in the air, the equator being near one of the nodes,* and there being two systems of currents — an upper and an under — between it and each pole. 418. " Let us return now to our northern particle, and follow it in a round Questions. — il7. Explain the direction of the return current. 418. Describe the course of a particle of atmosphere proceeding from the polar regions toward the equator. What does it meet near the parallel of 30° ? * Nodes, thfr point where the ascending and descending currents cross each other. TKADE-WINDS. 133 from the north pole to the equator and back again, supposing it, for the present, to turn back toward the pole after reaching the equator. Setting off from the polar regions, this particle of air, for some reason, which does not appear to have been satisfactorily explained by philosophers, travels in the upper regions of the atmosphere, until it gets near the parallel of 30° Here it meets, also in the clouds, the hypothetical particle that is going from the equator to take its place toward the pole. 419. " About this parallel of 30°, then, these two particles meet, press against each other with the whole amount of their motive power, produce a calm and an accumulation of atmosphere sufficient to balance the pressure from the two winds north and south. From under this bank of calms, two surface currents of wind are ejected : one toward the equator, as the north- east trades— the other toward the pole, as the southwest passage winds — supposing that we are now considering what takes place in the northern hemisphere only. 420. " These winds come out at the lower surface of the calm region, and consequently the place of the air borne away in this manner must be sup- plied, we may infer, by dovraward currents from the superincumbent air of the calm region. Like the case of a vessel of water which has two streams from opposite directions running in at the top and two of equal capacity discharging in opposite directions at the bottom — the motion of the water in the vessel would be downward : so is the motion of air in this calm zone. The barometer, in this calm region, is said by Humboldt and others to stand higher than it does either to the north or to the south of it ; and this is another proof as to the banking up here of the atmosphere and pressure from its downward motion. 421. " Following our imaginary particle of air from the north across this calm belt we now feel it moving on the surface of the earth as the north- east trade-wind, and as such it continues till it arrives near the equator, where it meets a like hypothetical particle, which has blown as the south- east trade-wind. Here, at this equatorial place of meeting, there is another conflict of winds, and another calm region, for a northeast and southeast wind can not blow at the same time in the same place. The two particles have been put in motion by the same power ; they meet with equal force, and, therefore, at their place of meeting, are stopped in their course. Here, therefore, there is also a calm belt. 422. " Warmed by the heat of the sun, and pressed on each side by the whole force of the northeast and southeast trades, these two hypothetical particles, taken as the type of the whole, ascend. This operation is the re- QuesUo7is.— 419. What results follow ? What surface currents are here^ejected ? 420. From what part of the calm region do these wnnds come, and what consequently may be inferred ? Illustrate the downward motion of the air in this calm zone. What is another proof of the banking up here of the atmosphere and pressure from its downward motion? 421. When does the particle of air move after leaving the calm belt? What occurs at the equatorial place of meeting ? 422. Why does it here ascend ? Describe its track in as it retoms to the pole. 134 TRADE-WINDS. verse of that which took place at the other meeting near the parallel of 30°. This imaginary particle now returns to the upper regions of the atmosphere again, and travels there until it meets, near the calm belt of Cancer, its fellow-particle from the north, where it descends as before, and continues to flow toward the pole as a surface wind from southwest. Entering the polar regions obliquely, it is pressed upon by similar currents coming from every meridian ; here our imaginary particle approaches the higher par- allels more and more obliquely, until it, with all the rest, is whirled about the pole in a continued circular gale : finally reaching the vortex, it is car- ried upward to the regions of atmosphere above, whence it commences again its circuit to the south as an upper current. * 423. " Now the course we have imagined an atom of air to take is this : an ascent at P, at the north pole ; an efflux thence as an upper current, until it meets G (also an upper current), over the calms of Cancer. Here there is supposed to be a descent, as shown by the arrows along the wavy lines which envelop the circle. This upper current from the pole now becomes the north- east trade wind B, on the surface ; it rises up at the equator, and returns thence — we will suppose for the present only — back toward the north pole, as G, until it reaches the calms of Cancer, where it descends and is felt on the surface as H, the southwest passage wind ; and so the circuit is com- pleted for the northern hemisphere." 424. Nothing excited the wonder of the early navigators so much as the east wind which blows regularly within the tropics. The companions of Columbus were terrified when they found themselves driven on by continu- ous east winds, which seemed to forewarn them that they would never return to their country. Fortunately for the fame of the great navigator, and for the world, he firmly held on his course, and made the discovery of a new continent. 425. The trade-winds serve important uses to navigators, in facilitating the passage of ships round the world. In passing from the Canaries to Cu- mana, on the north coast of South America, it is scarcely ever necessary to touch the sails of a ship ; and with equal facility a passage is made across the Pacific, from Acapulco, on the west coast of Mexico, to the Philippine Islands. The customary route of vessels on their outward voyage from New York to Canton is by the way of Cape Horn, and thence westwardly through the Pacific : the return voyage is by the way of the Cape of Good Hope. If a channel were cut through the Isthmus of Panama, the voyage to China would be more speedy, agreeable, and safe than the usual route by Cape Horn. 426. All mariners and passengers have spoken with delight of the region of the trade-winds. It is noted for the favoring gales, the transparent at- mosphere, the splendid sunsets, and the brilliancy of the unclouded heavens. Questions. — 423. Illustrate the course an atom of atmosphere is Imagined to take. 424 Wonder of the early navigators ? The companions of Columbus ? 425. Uses of the trade- winds ? Illustrate. Route of an outward and return voyage from New York to Canton ? 426. For what is the region of the trade-winds noted? MONSOONS. 135 day and night. Columbus, in recording his first voyage into their territory, compares the air, soft and refreshing without being cool, to that of the pure and balmy April mornings he had experienced in Andalusia. Humboldt, in describing the tropical regions, remarks upon the mildness of the climate and the beauty of the southern sky. He observed stars seen from infancy progressively sinking and finally disappearing below the horizon, an un- known firmament unfolding its aspect, and scattered nebulae rivaling in splendor the milky way. The Spaniards gave to the zone in which the trade- winds are constant the title el Golpo de las Damas, the Sea of the Jjadies, on account of the ease with which it may be navigated, the uniform tem- perature prevalent night and day, and its pacific aspect. LESSON V. PERIODICAL WINDS. 427. Periodical winds are those which regularly prevail at a certain time of the year or of the day. The monsoons of the Indian Ocean, the Etesian winds of the Mediterranean, and the land and sea breezes, are of this class, 428. Monsoons, from the Malay word moussin, signifying " a season," are regular periodical winds which sweep over the In- dian Ocean and the whole of Hindoostan, changing their direc- tion after an interval of about six months, as the sun moves into the northern or southern hemispheres ; hence the term season winds, or monsoons. These winds are a modification of the trade-winds, occasioned by the position of the sun in different seasons, the openings in the chain of islands separating the In- dian Ocean from the Pacific, the interposition of the Asiatic continent, and the rarefied atmosphere of Africa and Australia. 429. From 3° south of the equator to the northern shores of the Indian Ocean, including the Arabian Sea, the Bay of Bengal, and the Chinese Sea, a southwest wind prevails from April to October, and then a northeast wind sets in, and prevails through the next half year, from October to April. While the wind north Questions. — 427. What are periodical winds ? Name those which belong to this class. 42S. What are monsoons ? From what is the term derived ? What is said of these winds? 429. What are the limits of the region having a southwest wind from April to October? What wind prevails in this region from October to April ? Describe the winds which pre- vail at different seasons between 3° and 10° south of the line. 136 MONSOOXS. of tlie equator is .southwest, a southeast wind prerails between 3^ and 10^ south of the line ; and when the wind north of the equator is northeast, that south of it is northwest. -430. The western boundary of the region of the monsoons is the African shore : its eastern limit is supposed to be about the meridian of 130^ east longitude ; its northern confine is near the parallel of 27^ north latitude ; its southern extremity* has been alreacfy stated. The monsoons are much stronger than the trade- winds, and may be called gales : they sometimes blow with such violence that ships are obliged to reef their sails. They are not confined to the ocean, but extend over the whole of Hindoostan to the Himalaya Mountains. 431. Mr. Gaunter, a resident at Madras, gives the foUowing interesting account of a storm wMch occurred there during the shifting of these winds : " On the 15th of October, the flag-stafi" was struck, as a signal for all ves- sels to leave the roads, lest they should be overtaken by the monsoon. On that very morning some premonitory symptoms of the approaching war of elements had appeared. As the house we occupied overlooked the beach, we could behold the setting in of the monsoon in all its gi^and and terrific sublimity. The wind, with a force which nothing could resist, bent the tufted heads of the tall, slim, cocoa-nut trees almost to the earth, flinging the light sand into the air in eddying voi*tices, until the rain had either so increased its gravity or beaten it into a mass, as to prevent the wind, from raising it. 432. *' The pale lightning streamed from the clouds in broad sheets of flame, which appeared to encircle the heavens as if every element had been converted into fire, and the world was on the eve of a general conflagration ; whilst the peal, which instantly followed, was like the explosion of a gun- powder magazine. The heavens seemed to be one vast reservoir of flame, which was propelled from its yoluminous bed by some invisible but omnip- otent agency, and threatened to fling its fiery ruin upon every thing around. In some parts, however, of the pitchy vapor, by which the skies were by this time completely overspread, the lightning was seen only occasionally to gli m mer in faint streaks of light, as if struggling, but unable, to e5caf>e from its prison, — igniting, but too weak to burst, the impervious bosoms of those capacious magazines in which it was at once engendered and pent up. 433. '•' So heavy and continuotis was the rain, that scarcely any thing save those vivid bursts of light, which nothing could arrest or resist, was x>er- ceptible through it. The thunder was so painfully loud, that it frequently caused the ear to throb; it seemed as if mines were momentarily springing Questions. — 430. What is tlie western boundary of the region of monsoons ? Ite eastern limit? Ii3 nonhem ? la souihem ? Intensity of the monsoons ? ETESIAN WINDS, ETC. 137 in the heavens, and I could almost fancy that one of the sublimest fictions of heathen fable was realized at this moment before me, and that I was hearing an assault of the Titans. The surf was raised by the wind and scattered in thin billows of foam over the esplanade, which was completely powdered with the white, feathery spray. It extended several hundred yards from the beach ; fish, upward of three inches long, were found upon the flat roofs of houses in the town during the prevalence of the monsoon, either blown from the sea by the violence of the gales, or taken up in the water-spouts, which are very prevalent in this tempestuous season. 434. " When these burst, whatever they contain is frequently borne by the sweeping blast to a considerable distance over-land, and deposited in the most uncongenial situations : so that now, during the violence of these tropical storms, fish are found alive on the tops of houses ; nor is this any longer a matter of surprise to the established resident in India, who sees every year a repetition of this singular phenomenon. During the ^treme violence of the storm, the heat was occasionally almost beyond endurance, particularly after the first day or two, when the wind would at intervals entirely subside, so that not a breath of air could be felt, and the punka afforded but a partial relief to that distressing sensation which is caused by the oppressive stillness of the air so well known in India." 435. The monsoons are of great assistance to commerce ; by tliem a ship is frequently wafted to a distant port, and aided in returning by a monsoon blowing in an opposite direction to that which carried her out. 436. The Etesian* winds are periodical winds which blow from the northeast for about six weeks throughout the Mediter- ranean, particularly the Levant, where they commence toward the middle of July, about nine in the morning, and continue only throughout the day. The immense desert of Sahara, south of the Mediterranean, deprived of w^ater, and composed of sand and flints, become& very highly heated under the influence of an al- most vertical sun, and currents are created from the colder atmosphere of the north. Hence the passage from Europe to Africa in summer is much quicker than the autumn. Periodical currents, called nortes, or north-winds, blow from September to March in the Gulf of Mexico. They occur also on the Brazil coast, from N. E. in the spring, and S. E._in autumn. 437. Land and sea breezes are supposed to be caused by the Questions. — i35. "Cses of monsoons ? 436. What are the Etesian -winds ? Explain how they are caused. When and -where do the noHes blow? 437. Ho-w are land and sea breezes supposed to be caused ? Describe them. * "Erof, a year, a season. 138 THE ZONE OF CALMS. unequal heating of the land and sea On the coasts and islands within the tropics, a breeze from the sea daily occurs about nine o'clock in the morning, at first blowing gently toward the shore, but gradually increasing in force till the middle of the day, when it becomes a brisk gale ; after two or three o'clock it begins to subside, and is succeeded at evening by a breeze from the land, which blows freshly from off the coast during the night, and dies away in the morning when the sea-breeze commences. 438. These breezes are particularly strong along the coast of Malabar, where it is said that their influence is felt 60 miles from land. They are also very perceptible in the Mediterranean and ifi the East and West India Islands. The regular inland breezes experienced in the morning and evening, in some situa- tions, are produced by changes in the density of the atmosphere, affected by the radiating properties of neighboring snow-clad mountains, marshes, or sandy deserts. 439. The Zone of Calms, represented on the map, has a breadth of about 6° ; but varies with the seasons from 9^ to \(P. It is frequently interrupted by violent storms. " When the vessel on its voyage to the south approaches the equator in the midst of the Atlantic Ocean, anxious fear seizes the crew. Sooner or later, according to the time of year, the favoring wind which had brought them thus far, becomes weaker and weaker ; at first it ceases for a little while, and at last drops entirely. Around extends the sea, an endless glassy surface. The ship, hitherto speeding onward with a bird-like flight, lies bound on the crystal fluid. The rays of the sun, fall- ing perpendicularly, glow through and through the narrow space in which the men are inclosed. The deck burns through the soles of the shoes. A stifling vapor fills the cabins. A fortnight has the ruler of the sea lain im- movable in the same spot. The store of water is exhausted. Glowing thirst glues the parched tongue to the palate. Each man looks upon his companion in suffering with the wild, murderous glance of despair. 440. " The sun sinks below the horizon, the evening sky is illumined by a peculiar coppery redness ; and with the advancing night, arises a black wall to the eastward ; a low, shrill pipe resounds from the distance, from whence a streak of foam advances over the black ocean. The ship sways and rocks upon the irregular waves, but the sail still hangs against the mast, flapping dismally upon the spars. Suddenly the storm bursts over with frightful roar ; with a shriek the sails are torn asunder, and fly in ribbons ! A loud crack ! a second, and the mainmast goes overboard ! By a violent effort the crew succeed in cutting through the remaining ropes, and the ship now flies Questions. — 438. Where do these breezes prevail? How are regular inland breezea produced ? 439. How wide is the Zone of Calms ? HURRICANES. 139 over the ocean— now borne high upon the hacks of the waves— now hurled down into the depths ; so that every seam cracks and groans as though it would part asunder. The thunder rolls unceasingly ; continuous lightning darts through the agitated atmosphere ; the rain falls in streams instead of drops. Ten times the sailors give themselves up for lost, when the quaking bark falls into the trough of the sea, and as many times does it rise over the waves again. 441. " At last the storm lulls ; single shocks follow, always at longer in- tervals ; the waves become smoother, and when the consoling sun rises in the east, it illuminates the same dreary picture as on the former day. Mir- ror-hke the endless surface again expands, and in eight days is the store of collected water exhausted ; and again the silent specters creep about and turn murderous looks upon each other. A new storm, and a new calm, and so in frightful alternation, until at last the ship is driven into the region of the peaceful trade- wind on the other side of the equator. Hundreds of ships have gone down in storms here ; hundreds lost their crews by the most frightful of deaths, — that of thirst ; and those who have passed the fearful region of calms, turn in earnest worship to Heaven with thanks for their new- won life."* ; LESSON VI. HURRICANES. • 442. The terms hurricane, whirlwind, water-spout, land-spout, sand-pillar, tornado, white squall, pampero, etc., have been ap- plied to rotary movements of the atmosphere in dififerent parts of the world. 443. Hurricanes are revolving storms which occur in the West Indies and in the Indian Ocean. Of a similar kind are the ty- phoons in the Chinese Seas. These circulating movements oc- cupy a space from 50 to 500 miles in diameter. They revolve the more rapidly the nearer the center, up to a certain distance, within which there is a calm. 444. The center of rotation advances steadily along a definite line upon the globe, with a velocity varying from 2 to 30 or 40 Questions.— 442. What terms have been applied to the rotary movements of the atmos- phere ? 443. What are hurricanes ? What space do these circulatinfif movements occupy ? Where do they revolve the more rapidly ? 444. What is the velocity of the center of rota- tion ? What is a remarkable fact ? What is the rotation of the storms in the northern hemisphere ? In the southern hemisphere ? * Schleiden'a " Lecture about the Weather." 140 MOISTURE. miles per hour. It is a remarkable fact, that in the same hemi- sphere these whirling storms always revolve the same way, but that this direction is opposite in opposite hemispheres. In the northern hemisphere their rotation is retrograde, or in a direction opposite to the hands of a watch. In the southern hemisphere their rotation is direct, conformable to the hands of a watch. 445. There are three well-known hurricane regions — the West Indies, the Indian Ocean, and the Chinese Sea. The gen- eral course of the West Indian hurricanes is from the Leeward Islands N. W., passing around the shores of the Gulf of Mexico or across it, then followmg the Gulf Stream and terminating in the Atlantic, or exhausting their fury in the United States. From Oct. 3, 1780, to Aug. 25, 1837, inclusive, 38 hurricanes occurred m this region, in the following months : in June, 1 ; July, 4 ; August, 13; September, 10; October, 8; exclusive of 2, the months of which have not been recorded. Thus they are very rare in June, and most frequent in August. The only instance m June occurred in 1831, when Trinidad, Tobago, and Grenada were devastated, before supposed to be exempt from hurricanes. 446. The hurricanes of the Indian Ocean come from the N. E., near Sumatra and Java, and travel to the S. W. toward Rodri- guez and the Mauritius They occur chiefly from December to April, the hot season in that hemisphere ; are very rare in No- vember and May, and are quite unknown during the other months of the year. 447. In the Chinese Sea, hurricanes, there styled typhoons, range from 10^ to 30° N. They occur from June to November, after an interval of three or four years. LESSON YII MOISTURE. 448. If we place a vessel of Avater in the open air on a warm day, the quantity of the fluid will soon be sensibly diminished, Questions. — 445. Which are the three well-known hurricane regions? What is the general course of the West Indian hurricanes ? When are hurricanes in this region most rare, and when most frequent? 446. Describe the hurricanes of the Indian Ocean. When do they chiefly occur ? 447. What is said of the typhoons ? When and how often do they occur? 44S. What will happen if we place a vessel of water in the open air on a warm day ? Where does evaporation transpire on a grand scale ? MOISTURE. 141 or evaporated, being converted by the heat into invisible vapor, and diffused through the air. In like manner evaporation trans- pires upon a grand scale from the great collections of water on the earth's surface, the oceans, lakes, and rivers, as well as from moist ground. It I's subject to diurnal and annual variations. 449. The quantity of vapor diffused through the air is least in the morning before sunrise. As the temperature rises with the ascent of the sun, evaporation increases. The heat of raid- day causes the vapors to rise into the upper regions, and hence the greatest degree of dryness is generally felt during the day- time, though evaporation is then going on most rapidly. In January the quantity of vapor, like the mean temperature of the air, is at its minimum ; it increases from that period, and in July attains its maximum ; it then decreases to the end of the year. 450. The moisture in the atmosphere is an element on which the life of plants and animals as much depends as on tempera- ture. The healthfulness of climate is greatly influenced by the dryness or humidity of the atmosphere. As resulting from the action Of heat on water, the quantity of vapor diminishes with the temperature from the equator to the poles. It decreases also as we pass from coasts into the interior of continents. This rule is confirmed in the mterior of the United States, in the mid- dle of the plains of the Orinoco, in the steppes of Siberia, the deserts of Asia and Africa, and the central parts of Australia. In the temperate zone, in general, the annual evaporation is es- timated at between 36 and 37 inches of water. In the torrid zone, at Guadaloupe, it has been found to amount to 97 inches, and at Cumana to 100 inches. 451. The air is only capable of receiving a certain quantity of vapor. Its capacity depends upon its temperature, and is in- variable in its extent at the same temperature. According to Professor Leslie, air at the freezing point is capable of holding moisture equal to the 160th part of its own weight; at the tem- . — 449. When is the quantity of vapor diffused through the air the least? When does evaporation increase? What does the heat of mid-day cause? In what month is the quantity of vapor at its minimum, and in what at its maximum? 450. What is said of the moisture in the atmosphere? How does the quantity of vapor diminish? Annual evaporation in the temperate zone ? In the torrid zone ? 451. What is said of the capacity of air for receiving vapor ? Upon what does it depend ? Give its capacity at different states of temperature. 142 MISTS AND FOGS. perature of 59°, the 80th part ; at that of 86o, the 40th part ; at 11 30, the 20th part; and at that of 140°, the 10th part. 452. When a volume of air contains as much aqueous vapor as at its particular temperature it is capable of receiving, it is then said to be at the point of saturation, being as humid as can be. If the temperature. then rises, it will be capable of receiving more, but if it falls, some of the contained vapor will be rejected, and become visible as mist. Thus the effect of a change of temper- ature upon a saturated volume of air is analogous to that of the hand relaxing or tightening its grasp on a piece of imbibing sponge. 453. It has been frequently observed that the summits of some mountains are constantly covered with clouds. The formation of such clouds may be thus explained : The winds, laden with vapor from lower and warmer districts, in passing over such ranges are forced up into a colder region, where they are obliged to part with a portion of the vapor, which thus forms a cloudy state of the atmosphere. 454. Mists and fogs are formed when the air is saturated, and generally when the moist soil, or the water of lakes and rivers is warmer than the air, the vapors of which are immediately condensed. In like manner the vapor of the air breathed from our mouths in winter becomes condensed and visible. Mists differ in no respect from clouds except in position, being on the surface of the earth, instead of being suspended at a height in the atmosphere. 455. The thick mists which prevail in the neighborhood of Newfoundland arise from the warm waters of the Gulf Stream, which flow to that locality, the temperature of which is much higher than that of the saturated air. 456. Soon after sunset, in calm and clear weather, mists are frequently formed over the beds of lakes and rivers, while the adjacent land is free from them. This arises from the land more rapidly losing its heat by radi- ation than the lake or river. The air over the land necessarily becomes the coldest; and when the situation of the ground.is such as to bring the cold air of the land over the warmer water, a fog confined to its expanse ensues. Questions. — 452. When is a volume of air said to be at the point of saturation ? 453. What has been frequently observed ? How may the formation of such clouds be explained ? 454. When are mists and fogs formed ? How do mists differ from clouds ? 455. Origin of the mists which prevail in the neighborhood of Newfoundland ? 456. Explain why mists are frequently formed over the beds of lakes and rivers while the adjacent land is freo from them. CLOUDS. 143 457. Dew is formed by the gradual condensation of the vapors of the atmosphere. After sunset in summer, when the great di- urnal has filled the air with moisture, and the earth is gradually- cooled by radiation under a clear sky, the atmosphere in contact with the surface is chilled, and has its capacity to retain the aqueous vapors lessened, which are gradually and gently depos- ited in the form of fluid drops, called dew. In some countries dew supplies the place of rain. In Palestine and western Asia in general, where showers are unknown for several months in succession, the dew formed at night moistens the earth, and sus- tains the vegetation, being often so abundant as completely to saturate the tents, baggage, and clothing of travelers exposed to it. 458. As all objects have not the same capacity for radiating heat, some cooling much more rapidly than others, we frequently find certain bodies densely covered with dew, as grass and leaves, while the bare grounds, metals, stones, and wood are compar- atively dry. A thermometer laid on a grass-plot on a cloudless night has been upward of 16° lower than another laid at the same time on a gravel walk. Hence there has been a much more copious deposition of dew on the grass than on the walk, — the herbs needing the nourishment thus receiving it in preference to the bare soil — a striking evidence of an all-wise Being operating in the economy of nature.* LESSON YIII. CLOUDS. 459. Clouds are masses of visible vapor like mists, floating in the atmosphere, and occurring at a distance from the surface of the earth. They exhibit an endlessly diversified outline, a very varying density, and appear at difl'erent elevations. The dense clouds are usually formed toward noon, when the vapors are raised up by the ascending currents of air and then com densed by the lower temperature of the upper regions. Questions. — 457. How is dew formed ? Explain particularly the operation of Its forma- tion. What is said of the dews of Palestine and western Asia ? 458. Why does dew col- lect more on some bodies than others ? 459. What are clouds ? What is said of them ? * Eev. Thomas Milner. 144: CLOUDS. 460. Though clouds are generally composed of vapor, they may consist of frozen particles. In winter", during severe cold, we can often observe that the vapors which rise are composed of brilliant needles, that glisten in the sun and resemble small flakes of snow. The same thing must take place in the higher regions of the atmosphere. There exist, therefore, snow clouds and clouds of vapor of water. 1, 1. Cirrus. 3. Cumulus. 5. Stratus. 2, 2. Cirro- Cumulus. 4. Nimbus QuetiMis. — 160. Of wLat arc duuds (•(iiiii-so.! ? V.hiit t\v<. kin.U? CLOUD6. 145 461. Notwithstanding the varied aspect ol clouds, they may be arranged into three principal classes — the cirrus, the cumulus^ and the stratus. 462. Cirrus — Curlcloud. Fig. 1. — The cirrus (the cafs-tail of sailors) is composed of thin filaments, variously disposed, in the form of woolly hair, a crest of feathers, or slender net-work. The cirri appear in the higher regions of the atmosphere, and are the most elevated of the clouds. Viewed from the summits of high mountains, while the traveler looks down upon other forms of clouds, he beholds these still above him, and apparently at as great a distance as when seen from the plains. The ap- pearance wof true cirrus, or curlcloud, is supposed to indicate variable weather ; when most conspicuous and abundant, to pre- sage high winds and rain ; and when the streaming fibers have pointed in a particular direction for any length of time, the gale may be expected to blow from that quarter. 463. Cumulus — Stackencloud. Fig. 3. — This form of cloud {ball of cotton of sailors) occurs in the lower regions of the at- mosphere, and is easily recognized. It is commonly under the control of the surface winds, and frequently exhibits a veiy mag- nificent appearance. It consists of a vast hemispherical or con- ical heap of vapor rising gradually from an irregular horizontal base and increasing upward. Hence the names, cumulus, a pile or heap, and stackencloud, a number of detached clouds stacked into one large and elevated pile. 464. Cumuli are indications of fine weather. They begin to form soon after sunrise from irregular and scattered specks of cloud ; as the morning advances the clouds enlarge ; and early in the afternoon, when the temperature of the day is at its max- imum, the cumulus attains its greatest magnitude. The cloud decreases as the sun declines, and is usually broken up toward sunset. The cumulus may be called the cloud of day, from the interval between morning and evening generally measuring the term of its existence. Its appearance considerably varies in the detail, and often exhibits a brilliant silvery light, and a copper Questionft. — 461. Into what three principal classes may clouds be arranged ? 462. De- scribe the cirrus or curlcloud. What is said of the height of the cirri ? What is the cirrus supposed to indicate? 463. Describe the cumulus or stackencloud. Of what does it con- sist ? 464. What do cumuli indicate ? Describe their successive changes during the day. 7 146 CLOUDS. tinge, when in opposition to the sun, indicating a highly electrical condition of the atmosphere. 465. Stratus^Fallcloud. Fig. 5. — This cloud consists of horizontal bands near the surface of the earth. It belongs to the night, forming at sunset and disappearing at sunrise. This class of clouds comprehends all those fogs and creeping mists which sometimes spread like a mantle over the surface of the valleys, plains, lakes, and rivers. 466. To the above primary varieties three transition or com- posite forms are added. Cirrocumulus — Sondercloud. Fig. 2. This name designates the feathery accumulated cloud, familiarly known as fleecy, intermediate between cirrus and cumulus. It consists of small patches, arranged in extensive beds, the com- ponent parts being quite distinct or asunder. Cirrostratus — Wanecloud and Cumulo stratus — Twaincloud (not represented in the cut), are combinations, — ^the former of the cirrus and stratus, and the latter of the cumulus and stratus. 467. Nimbus — Raincloud. Fig. 4. — Any of the preceding modifications may pass over into the actual rainy clouds, first exhibiting a great increase of density, and a bluish-black tone of color, then putting on a lighter shade, or gray obscurity, and becoming fringed at the edges. 468. Clouds are generally higher within the tropics than in the temperate zones ; and in the temperate zones they are com- monly higher in summer than in winter. The cirri are the high- est clouds. They are supposed to range from 3 to 5 miles above the level of the earth. Kaemtz states that during a stay of eleven weeks within sight of the Finsteraarhorn, upward of 14,000 feet high, he never observed any cirri below the summit of the mountain. It is highly probable that they consist of flakes of snow. Questions. — 465. Of what does the stratus or fallcloud consist? When does it prevail ? What does this class of clouds comprehend ? 466. Describe the cirrocumulus or sonder- cloud. What other composite forms are mentioned ? 46T. Change to the nimbus or rain- cloud ? 468. What is the comparative height of clouds in different zones and seasons ? Height of the cirri ? What does Kaemtz state ? LESSON IX. RAIN. 9. Rain is water, which, originally taken up into the at- mosphere in the state of vapor, is returned to the earth in thp form of liquid drops. It is produced by the continued conden- sation of vapor. Rain may begin to fall, and yet not reach the ground, being resolved into invisible vapor on arriving at strata of air removed from the point of saturation. For the same reason, rain-drops may become smaller in their descent, a por- tion being evaporated, and less rain arrive at the earth's surface than at a certain height above it. Usually the drops increase in their fall, bringing with them the low temperature of the upper regions. 470. The following are examples of very extraordinary showers : 1822 Oct. 25, at Genoa, 30 inches of rain fell in 24 hours. 1827 May 27, at Geneva, there fell 6 inches of rain in 3 hours. 1841 June 4, at Cuiseaux, a small town in the valley of the Saone, there fell about 11 inches in 68 hours. At Cayenne, Admiral Roussin collected 10 inches in 10 hours. 471. Rain is very unequally distributed over the regions of the globe. 1. The average annual quantity of rain is the great- est in tropical climates, and diminishes as we recede from the equator to the poles. 2. It decreases as we pass from maritime to inland countries, because the land supplies a less quantity of vapor than the sea. 3. More rain falls in mbuntainous than in low level districts, lofty heights arresting the clouds, and pro- moting the condensation of vapor by their cold summits. 4. The result of experiment shows that a greater amount of rain falls while the sun is below than when above the horizon. 472. The diminution of the average annual quantity of rain from the equator to the poles, appears from the following Table : San Luis de Maranhao lat. 3° S. is equal to 276 inches. Parimaribo, Guiana " 6° N. " 229 " Questions. — 469. What is rain ? How produced ? 470. Give examples of very extra- ordinary showers. 471. What is said of the unequal distribution of rain ? Where is the average annual qu.nntity the greatest? Where does it decrease? What is observed of mountainous districts ? What does the result of experiment show ? 472. What is the an- nual quantity of rain in different places? The annual quantity within the Tropics of the Old World ? Of the New World ? Average for the Tropics generally ? Annual quantity in the Temperate Zones of the New World ? In the Temperate Zones of the Old World ? In the Temperate Zone generally ? 148 RAIN. Sierra Leone, Guinea " 9° N. is equal to 189 inches. Island of Grenada, West Indies. " 12° " 108 " Hayana, Cuba.. "23° " 90 " Calcutta "22° " 81 " Macao, China ''22° " 68 " Charleston, South Carolina "33° " 47 Rome ,.. = "42° " 89 " Edinburg "65° «^ 24 " St. Petersburg "60° " 17 "' Uleaborg, Finland "65° " 13 " Annual quantity of Rain within the Tropics of the New World. 115 inches. Annual quantity within the Tropics of the Old World 76 " Average for the Tropics generally . .' 951 " Annual quantity of Rain in the Temperate Zones of the New World (United States) 37 inches. In the Temperate Zones of the Old World (Europe) 31| " Temperate Zone generally 34| " 473. Although the amount of rain is greater within the tropics than in the temperate zone, yet the niimber of rainy days is less, because two seasons divide the year — wet and dry ; and during the dry season entire months frequently pass away without a drop falling or a cloud being seen. In the temperate zone also, in passing from south to north, the number of rainy days increases, although the intensity of rain diminishes. Annual number of rainy days in North of Syria 54 Straits of Gibraltar , . : 68 Plains of Lombardy 90 Buda, Hungary 112 Plains of Germany 141 England and West France 152 Poland 158 St. Petersburg 169 Netherlands 170 East of Ireland 208 474. Countries situated in the vicinity of the sea receive, as we have re- marked, a larger amount of rain than those inland. This is exemplified in the interior of the IJnited States, of the llanos of the Orinoco, of the Si- berian steppes, of Australia, and on comparing the amount of precipitation in inland and maritime countries. It declines from an annual fall of be- tween 30 and 35 inches on the shores of Great Britain and France to from 15 to 13 inches as the borders of Asia are approached. Mountains produce Questions. — 473. Where is the number of rainy days less than in the temperate zone, and •why ? "What is observed in passing from south to north in the temperate zone ? State tbe annual number of rainy days in different places. 474. What is said of countries situated in the vicinity of the sea? How is this exemplified ? With what does the annual number of rainy days decrease ? Illustrate. KAIN. 149 several exceptions to this rule. The annual number of rainy days aecreases also with the increased distance from the sea. West coast of France 152 days. Interior of France 14:7 " Kasan, Plains of the Volga • 90 " Interior of Siberia 60 " 475. The annual fall of rain in mountainous districts, as compared with that of low and level countries, is sometimes very striking. At Keswick — a mountainous district in England — the annual average depth of rain is 67 inches, while on the sea-coast it is not half that amount. On the Great St. Bernard it is 63 inches, and at Paris only 21. " The description of Judea by the sacred writer, contrasting it with the flat lands of Egypt, though not intended to be philosophic, is in harmony with the teachings of science respecting the important part performed by mountains in the general-econ- omy of the earth : — ' For the land whither thou goest in to possess it, is not as the land of Egypt, from whence ye came out ; but the land whither ye go to possess it, is a land of hills and valleys, and drinketh water of the rain of heaven.' By arresting the course of the clouds, and producing a con- densation of aqueous vapor when a warm current of air lights upon their cold summits, the elevations contribute to precipitate the moisture of the atmosphere, often amid a terrible display of electric phenomena — a blaze of fiery horrors, and the echo of heart-thrilling sounds."* 476. In some portions of the world rain is entirely unknown, or occurs so scLlom as to be quite a phenomenon. The rainless regions of the New World comprise portions of California and Guatemala, the Mexican table-land, and the coast line of ieru. Those of the Old World comprehend an immense territory, stretching from Morocco, through the Sahara, a part of Egypt, Arabia, and Persia, into Beloochistan, with another great zone, commencing north of the Hindoo-Koosh and Himalayas, includ- ing the table-land of Tibet, the desert of Gobi, and a portion of Mongolia. 477. The rains of most tropical countries are periodical, — seasons of extreme humidity regularly alternating with those of excessive drought. The length of time of the rainy season differs in different districts, but lasts generally from three to five Questions. — 475. What facts illustrate the difiFerence between mountainous districts and low. and level countries, with respect to the fall of rain ? What is remarked of the de- scription of Judea by the sacred writer? 476. What do the rainless regions of the New World comprise ? What, those of the Old World ? 477. What is said of the rains of most tropical countries ? Length of the rainy seasons ? When do they commence at Panama, etc. ? Violence of these tropical showers ? * Eev. Thomas Milner. 150 SNOW. months. The periodical rains commence in Panama, on the west coast ol i\merica, m uie eariy part of March ; in Africa, near the equator, and on the banks of the Orinoco, they begin in April ; in the countries watered by the Senegal, and at San Bias, in California, they begin in June. The violence of these tropical showers may be inferred from the large annual amount of rain, and from its fall being limited to a few months, and to a few hours during the day. The drops are enormous, very close to- gether, and fall with such rapidity as to occasion a sensation of pain if they strike against the skin. 478. In both continents the districts which have their periodical rains are subject to an occasional intermission, and become rainless for considerable intervals, the drought inflicting terrible suffering on man and beast. Such a 23eriod happened between the years 1827 and 1830 in the state of Buenos Ayres, and is known by the name of the gran seco, or the great drought. This interval was very destructive to animals. The loss of cattle in the province of Buenos Ayres alone, was estimated at one million head. Cattle in herds of thousands rushed into the Parana, and being exhausted by hunger they were unable to crawl up the muddy banks, and thus were drowned. LESSON X. SNOW AND HAIL. 479. Snow is nothing more than rain congealed before it falls to the earth. Snow-flakes exhibit forms of exquisite beauty, regularity, and endless variety. These varied shapes are as- sumed while the body passes from the liquid to the solid shape. The tendency of wate to crystallize, while in the process of con- gelation, may be observed in winter on panes of glass. 480. A microscope applied to a flake of snow will unfold its wonderful mode of structure. It is only in the polar regions that snow assumes its most beautiful and varied forms. Captain Scoresby has figured ninety-six different varieties, which he dis- covered during his Arctic voyages, and which he distributed into Questions. — 478. To what are the rainless districts of both continents subject? Ex- ample? Destruction of cattle? 479. "What is snow? What do snow-flakes exhibit? When are these varied forms assumed? 480. In what region does snow assume its most varied forms ? How many varieties discovered by Captain Scoresby, and how distributed? What does Kaemfz observe ? SNOW 151 classes of lamellar,* spicular,t and pyramidal crystals, as shown in the annexed representation. It will be seen that the annexed forms are mostly hexagonal J stars, and consequently snow-flakes Cjjp rf.3 LSD sToS Various Forras of Snow Crystals. * Lamellar, composed of thin plates or scales. t SpictrLAE, resembling a dart. $ Hexagonal, having six sides and nnsles. 152 HAIL. belong to the hexagonal system of crystals. Kaemtz observes that flakes which fall at the same time have generally the same form ; but if there is an interval between two consecutive falls of snow, the forms of the second are observed to differ from those of the first, although always alike among themselves. 481. The limits of the fall of snow at the level. of the sea, in the northern hemisphere > are about the parallel of 30° in Amer- ica, which cuts the southern part of the United States ; 43° in the center of the North Atlantic ; and 36° in the Old World, the latitude of Algiers. But for several degrees above these limits its appearance is rare and brief. 482. Snow performs an important part in the general economy of nature. In winter it serves as a mantle to keep the ground warm, and thus protect vegetation from being destroyed by the frost, or by cold biting winds. Accumulated on elevated mount- ain chains, it affords, by its thawmg, a regular supply to rivers and to the interior reservoirs of the earth, while in low latitudes it tempers the heat of warm regions. 483. Hail appears to be partly the result of a very intense degree of cold being rapidly produced in the atmosphere ; it is supposed to be also somewhat dependent upon electricity, which is almost always powerfully developed durmg hail-storms. In very high latitudes it is unknown, and it is also rare at the level of the sea within the tropics. The icy particles which fall vary in shape and size. True hail is an opaque mass, and has gen- erally the form of a pear, or of a mushroom ; large hailstones are surrounded by a thick coat of ice, and are composed of alternate layers of snow and ice ; no one has ever seen hail- stones formed entirely of transparent ice. 484. Many instances are well authenticated of hailstones haying a cir- cnmference of from 6 to 9 inches, and a weight of from 12 to 14 ounces ; but much larger masses are recorded. June 15, 1829, the hail beat in the roofs of the houses at Cazorta, in Spain, — some of the hailstones weighing up- wards of 4 lbs. avoirdupois. In Hungary, May 8, 1832, a block of ice fell. Questions.— i^l. Limit of the fiill of snow in America? In the center of the North At- lantic? In the Old World? 4S2. What are some of the uses of snow? 48-3. Of what does hail appear to be the result? Upon what is it supposed to be also somewhat depend- ent? Where is it unknown and where rare? Appearance of true hail? 484. Size of some hailstones observed ? Examples of destructive effects of hail ? What is remarked of these enormous mns«ps ? CLIMATE. 163 abo-Qt 39 inches in breadth and length, and 27 inches in depth. Mr. Dar- win mentions a fall of hail in the state of Buenos Ayres which killed a large number of wild animals, ostriches, and smaller birds. These enormous masses are either the fragments of a thick sheet of ice suddenly formed, and broken in the atmosphere in falling, or are due to the union of a great num- ber of hailstones in their descent. Snow y^oTrQ LESSON XI CLIMATE. 485. Climate, in its relation to animal and vegetable exist- ence, constitutes one of the most interesting and important sub- jects belonging to physical geography. The term, as it is com- monly understood, denotes the temperature of the air in the va- rious regions of the globe ; but taken in its more general sense, it signifies all those states and changes of the atmosphere which sensibly affect our organs, — temperature, humidity, variation of atmospheric pressure, the purity of the atmosphere, or its admix- ture with more or less deleterious exhalations, and lastly, the degree of habitual transparency of the air and serenity of the sky, w^hich has an important influence on the feelings and the whole mental disposition of man. Questions. — 485. What is said of climate ? What does the term climate commonly de- note ? Taken in its more general sense, what does it signify ? 7* 154 CLIMATE. 486. Climate is determined by a variety of causes, the chief of which are : 1 . The latitude of a country ; that is, its geo- graphical position with reference to the equator. 2. Elevation of the land above the sea-level. 3. The proximity to, or re- moteness of a country from, the sea. 4. The slope of a country, or the aspect it presents to the sun's course. 5. The position and direction of mountain chains. 6. The nature of the soil. 7. The degree of cultivation and improvement at which the country has arrived. 8. The prevalent winds. 9. The annual quantity of rain that falls in a country. 487. (1) The latitude of a country, and the consequent direc- tion in which the solar rays fall upon its surface, are the princi- pal causes of the temperature to which it is subject. At the equator, and within the tropics, the greatest heat is experienced, because the sun is always vertical to some place within those limits, and the solar action is more intense in proportion as the rays are perpendicular to the earth. As we recede from the equator, they fall more obliquely ; and because fewer of them are spread over a larger space, they are less powerful, and conse- quently less influential in promoting temperature. It has been calculated that, out of 10,000 rays falling upon the earth's at- mosphere, 8,123 arrive at a given point if they come perpen- dicularly ; 7,024, if the angle of direction is 50° ; 2,821, if it is 7° ; and only 5 if the direction is horizontal. 488. The latitude of a place is therefore of the first import- ance in determining its temperature, since a decrease of heat takes places with an increase of latitude as we travel, at the same level above the sea, from the equator toward the poles. This is true of countries lying between the tropics and the poles, but it is not true of places situated between the tropics and the equator. 489. " If the ecliptic, as shown on a terrestrial globe, be examined, it will be seen that toward the northern and southern limits, for a consider- able distance, it neither approaches nor recedes from the equator or the QuesUo7is.—4:'i&. What are the principal causes which determine climate ? 487. What principally determine the temperature of a country ? Why is the greatest heat experienced within the tropics ? What happens as we recede from the equator ? 488. Why is the lat- itude of a place of the first importance in determining its temperature ? Is this true of countries lying between the tropics? 489. Explain why a greater degree of heat prevails at Ihe tropics than at the equator. CLIMATE. 155 pole, but has a direction due east and west. This ecliptic is, in point of fact, the path or the point of direct heat and sunlight over the earth's surface. Thus, then, it appears, that when this point has reached its near- est approach to either pole, it does not immediately turn back toward the other pole, but remains at that nearest distance for a considerable time ; or, as it were, lingers there. It has been calculated, that if the space between the tropics be imagined to be divided into three equal bands of the earth, the point of direct sunlight would be found to linger in each of the two outer bands 3i times as long as in the middle band. 490. " This lingering of the point of direct heat and sunlight at its nearest approach to the poles, is a necessary result of that simple and admirable provision, by which the earth is made to revolve round the sun, rotating at the same time round an axis which has an inclined position, and which pre- serves its parallelism. The object of it is obviously to minister to the polar regions, in 'their due proportion, light and heat."* 491. In the northern hemisphere, the countries where the greatest heat is experienced — the banks of the Senegal, the Te- hama of Arabia, and Mekran in Beloochistan — coincide with the tropic of Cancer ; and it has been found that the snow-line of the Andes in 17o south latitude is higher than at the equator, an evidence of a higher temperature. 492. (2) The temperature of countries is largely affected by the extent of their elevation above the level of the sea. As we as- cend in the atmosphere the cold increases, — an effect due to the rarefaction of the air, and to the circumstance of being farther from the heat reflected from the surface of the earth. We may travel several hundred miles from the equator toward the poles, along the level surface of the earth, before we become sensible of a diminished temperature ; but the moment we begin to increase our elevation, a rapid change of temperature is experienced, until we arrive at a point where constant frost prevails. 493. The ratio of the diminution of temperature usually given, is 1° for 300 feet of height ; 2° for 595 feet ; 3° for 872 feet ; 4© Questions. — 490. What is said of the lingering of the point of direct light and heat at the tropics? What is obviously its object? 491, What is said of the countries in the northern hemisphere where the greatest heat is experienced ? 492, By what else is the temperature of countries largely affected ? What occurs as we ascen.l m ihe atmosphere, and why ? State the difference, as affecting climate, between travehng on the surface of the earth, from the equator toward the poles, and mcreasing our elevation. 493. What is the ratio of the diminution ot temperamre for different heights ? What is remarked of Ihe effect of elevation in the temperate zone ' * Professor Moseley's " Astro-Theology." 156 CLIMATE. for 1,124 feet ; 5° for 1,347 feet ; and 6° for 1,539 feet. In the temperate zone generally, if one site is a thousand yards higher than another adjoining, it will have a climate 12° colder ; and the higher the latitude the lower the snow-line becomes, till it meets the surface of the earth in the frigid zone. The following diagram represents the line of perpetual snow forming the arc $^^ Heiglit in Feet. Surface of tli8 Eaitli. 40 50 60 70 80 of an ellipsoid passing over the equator, from pole to pole. Making allowance for the fact that the snow-line of the Andes is higher at some distance from the equator, the diagram should not ex- hibit a continuous curvature, but be corrected as follows : ^;iSi-— 1 ^ ^ o b e a> 05 M ,^ o "~^ s? b o Height in Feet o o o o o o o ^ -