V-//1 .^^ 5 ill' ^ I^I-BR^l^Y I .-.,/ ..3...3V,. ill Please handle this volume vyrithcare. The Umversity of Connecticut Ubraries, Storrs BOOK 55 1.2 1.D19 c. 1 DANA # CHARACTERISTICS OF VOLCANOES 3 T1S3 DD135flDS 2 '^^«^J^><-vviL>^^^^ ^1 ^^^^^^ Th^ Rook n ^' kent o u X Plate I. UfvoluP ia_^ H AWA FROM THE GOVERNMENT MAP 1 lOnviles. t&.Ue CHARACTERISTICS ,., OF ,'T)'^ VOLCANOES, WITH CONTRIBUTIONS OF FACTS AND PRINCIPLES FROM THE HAWAIIAN ISLANDS, INCLUDING A HISTORICAL REVIEW OF HAWAIIAN VOLCANIC ACTION FOR THE PAST SIXTY-SEVEN YEARS, A DISCUSSION OF THE RELATIONS OK VOLCANIC ISLANDS TO DEEP-SEA TOPOGRAPHY, AND A CHAPTER ON VOLCANIC- ISLAND DENUDATION. By JAMES D. DANA. ILLUSTRATED BY MAPS OF THE ISLANDS; A BATHYMETRIC MAP OF THE ATLANTIC AND PACIFIC OCEANS; AND VIEWS OF CONES, CRATERS, A LAVA-CASCADE, A LAVA-FOUNTAIN, ETC. NEW YORK: DODD, MEAD, AND COMPANY. 1891. 344 Copyright, 1890, By Dodd, Mead, and Company. All rights reserved. SIniijcrsitg Press: John Wilson and Son, Cambridge. PREFACE. np'HE personal observations of the author on which this book is based commenced with the ascent of Vesuvius in 1834, and, the next month, a sight of Stromboli and a tramp after minerals on the solfataric island of Milo. They were continued in 1838 by short excursions on Madeira and one of the Cape Verds ; in 1839, by studies of the extinct volcanic regions of Xahiti, Tutuila and Upolu, and the basaltic outflows and overflows of Illawarra and other parts of New South Wales. They were further extended in 1840 by observations in the Feejees, and by explorations of the active and extinct volcanoes of the Hawaiian Islands ; in 1841, by observations on a crater in the coast region of Oregon, instructive though distant views of some of the lofty cones of the Cascade Range, and a brief survey of an extinct volcano on the Sacramento (now called Marysville Butte) during an overland trip from Vancouver to San Francisco ; and, finally, in 1860 by a second visit to Vesuvius, and in 1887 a second to the Hawaiian Islands. The purpose of the work is the illustration of volcanic action and principles by special reference to the facts sup- plied by the great, open, free-working craters of Hawaii, and by comparing and contrasting these with the corresponding features and phenomena of Vesuvius. It commences with an elementary treatise on volcanoes and volcanic action, that iv PREFACE. the book may be a convenient manual for the geological student and also for the tourist. After these general ex- planations, the workings of the fires in the two active craters of Hawaii are successively set forth by means of descriptions and various illustrations ; and a knowledge is thus presented of the steps in the progressing activity, the dependence of these steps on one another, and their relation to the final catastrophe. After such a study it becomes easy to apprehend the deductions which follow with regard to the methods and principles of volcanic action. The work contains, in Part Third, an account of the topog- raphy of the Pacific basin, with a map of deep-sea Pacific and Atlantic soundings, and a discussion of the influence upon the depth of the oceans of volcanic action. Further, Part Fourth treats of denudation, or valley-making, on vol- canic islands. The subject is illustrated by a map of the island of Tahiti, an admirable example of water-sculpture, and by supplementary facts from New South Wales cited from the author's '' Geological Report of the Wilkes United States Exploring Expedition." Of this report only one hun- dred copies were ordered for the Government ; and these, with an additional hundred printed at the time (fifty-one years ago) at the author's expense that it might escape ob- livion, are all that were ever issued ; hence some freedom in copying its nearly inaccessible pages has been thought allowable. The pages of this volume contain many reasons why the two active craters of Hawaii should share equally with Vesuvius and Etna in the attention of investigators. Hardly three weeks distant from Europe and not two from New York, with much to be seen on the way and tropical islands growing corals and tree-ferns at the end, the route should be a common one with tourists. The PKEFACE. V magnitude and easy access of the great craters; their prox- imity, while nearly ten thousand feet apart in altitude ; their strange unlikeness in ordinary action, although alike in features and lavas ; their unsympathizing independence ; their usually quiet way of sending forth lava-streams twenty and thirty miles long, — make them a peculiarly instructive field for the student of volcanic science, as well as an attrac- tive one for the lover of the marvellous. Even the lavas, although nothing; but basalt, have afforded much that is new to science, as is shown in the chapter by my son, Prof. Edward S. Dana. Reviewing the developments thus far made, we find that the region has already contributed many new ideas to the vulcanologist. Science has learned of volcanic activity un- restricted by altitude up to fourteen thousand feet ; of the possibility of two first-class craters working simultaneously within the area of one mountain-dome, and having the loftier the more frequent and the more copious in its outflows, and neither of them ordinarily responsive to the other even when in eruption ; and of the outflow of the heaviest of chrysolitic lavas at various altitudes to the very summit. Science has learned from Hawaii more than it knew of the mobility of liquid basalt ; of the consequent range in flow-angle of basalt-lavas, from the lower limit near hori- zontality to the verticality of a waterfall, and therefore of lava-cones of the lowest angle, and driblet-cones of all angles ; of lava-lakes tossing up jets over their fiery sur- face like the jets of ebullition, and in other cases playing grandly in fountains hundreds of yards in height ; and, con- sequently, of the absence from the craters of large cinder- ejections. It has further learned of a degree of system in the •changes within a crater from one epoch of eruption to a VI PEEFACE. state of readiness for another; of a subsidence, after an eruptive discharge of lava, that has carried down, hundreds of feet, a large part of a crater's floor without a loss of level in its surface ; and, following this, of a slow rising of the subsided floor, chiefly through the ascensive or up- thrust action of the lavas of the lava-column, and the lift- ing force taking advantage of the fault-planes that were made at the subsidence ; and also of debris-ridges and of debris-cones, one to two hundred feet in elevation, made, by the lift, out of the talus of the pit-walls. It has learned that pit-shaped craters are characteristic of true basalt-volcanoes, and a result of the free mobility of the lavas, whether the action in the lava-lakes within be fountain-like or boiling-like; that floating islands of solid lava may exist in the lakes ; that a regular oscillation be- tween fusion and cooling takes place at times in the thin crust of lava-lakes ; that the solid lava of the margin of a lake may be re-fused, and also even the mass of a float- ing island, and the blocks of a debris-cone until the cone has wholly disappeared. It has discovered that solfataric action, or that of the hot vapors in lava-caverns, may include the recrystalliz- ing of basalt, therein making it into long, stony pipe-stem stalactites and stalagmites, having cavities lined with trans- parent crystals of augite and labradorite, besides octahe- drons of magnetite. It has obtained evidence, also, that the greatest of erup- tions may occur without the violence or the noise of an earthquake, and without an increase of activity in the crater; that in place of an increase there may be a sud- den extinction of the fires, all light and heat and vapors disappearing as soon as the discharge begins; of the greater frequency of eruptions during the wetter season PREFACE. Vll of the year ; of the agency of fresh water from the rains (and snows) in the supplying of steam-power for volcanic action ; of the full sufficiency of water from this source without help from the ocean, — fresh water being as good as salt for all volcano purposes ; and further, of a great augmentation of the activity so produced with the increase in altitude of the working crater. These are facts from Hawaii — and not all that might be cited — that have not yet been made out from the in- vestigation of other volcanoes, not even the best known, Vesuvius and Etna. But much remains to be learned from the further study of the Hawaiian volcanoes. Some of the points requiring elucidation are the following : the work in the summit- crater between its eruptions ; the rate of flow of lava- streams and the extent of the tunnel-making in the flow ; the maximum thickness of streams ; the existence or not of fissures underneath a stream supplying lava; the tempera- ture of the liquid lava ; the constitution of the lava at the high temperatures existing beneath the surface ; the depth at which vesiculation begins ; the kinds of vapors or gases escaping from the vents or lakes ; the solfataric action about the craters ; the source of the flames observed with- in the area of a lava-lake ; the differences between the lavas of the five Hawaiian volcanoes, — Kilauea, Loa, Kea, Hualalai, and Kohala ; the difference in kind or texture of rock between the exterior of a mountain and its deep- seated interior or centre, — for the elucidation of which subject Kohala's northern gorges may possibly afford mate- rial ; the difference between Loa, Kea, and Haleakala in the existence below of hollow chambers resulting from lava-discharges, — a problem which Mr. E. D. Preston has begun to solve by pendulum observations, and there is Vlll PREFACE. reason to hope may continue to investigate to its complete solution ; and, besides, if admitting of field study, the move- ments of the lavas in the great lava-columns, and the source or sources of the ascensive movement. The geologist who is capable of investigating these subjects will find other inquiries rising as his work goes forward. James D. Dana. New Haven, Conn., Feb. 12, 1800. TABLE OF CONTENTS. part ifirsft. Characteristics op Volcanoes. Page I. General Characters 1 11. Volcanic Rocks, Gases, and Lava-streams , 4 III. Forms of Volcanic Cones 11 rV. Methods and Causes of Volcanic Action ........ 15 part ^econD* Contributions from the Hawaiian Islands to the Science of Volcanoes. I. The Island of Hawaii 28 A. KiLAUEA . 41 1. KiLAUEA before 1823 41 2. KiLAUEA FROM 1823 TO 1841 45 3. KiLAUEA FROM JANUARY, 1841, TO 1868 INCLUSIVE ... 74 4. KiLAUEA FROM 18G8 TO 1890 91 5. General Summary with Conclusions 124 I. Historical Conclusions 124 1. Periodicity or not in the Discharges of Kilauea .... 124 2. Mean Rate of Elevation of the Floor of the Crater after the Great Eruptions 125 3. Levels of the Floor after the Eruptions of 1823, 1832, 1840, 1868, and 1886 126 4. Progress in Halema'uma'u since the Eruption of March, 1886 120 6. Other Points in the Topographic History of the Kilauea Region 130 n. Dynamical Conclusions 141 1. Kilauea a Basalt-volcano 142 2. Size of the Kilauea Lava-column 151 3. Ordinary Work of Kilauea 153 C TABLE OF CONTENTS. L'he Island of Hawaii {Contittued). Page A. The Work done by Vapors 154 1. The Vapors concerned : their Kinds and Sources . 155 2. The EEfect of the Expansive Force of Vapors in their Escape from the Liquid Lavas : Projectile Action 158 3. The Effects of the Expansive Force of Vapors within the Lavas. — Vesiculation and its Me- chanical Effects 161 4. Work of Vapors generated outside of the Conduit : Fractures, Displacements, and other Results . 16!) B. The Ascexsive Action in the Lava-column . 170 C. PREFECTS OF Heat .175 D. Hydrostatic and other Gravitational Pres- sure 179 B. Mount Loa, Mokuaweoweo 180 1. Eruptions of Mount Loa from 1832 to 1868 180 2. Eruptions of Mount Loa from 1868 to 1890 197 3. General Summary, avith Conclusions 217 1. Times and Time-intervals of Eruptions 217 2. The Ordinary A\'ork of the jNIount Loa Crater 222 3. Causes of the Ordinary Movements within the Crater . . . 223 Solfataric Action 228 C. Eruptions of Mount Loa and Kilauea 228 I. Characteristics and Causes of Eruptions 228 1. Ordinary or Non-Explosive Eruptions 229 Height and Position of Outbreaks 229 Causes of Eruptions 230 Outflows and the Attending Circumstances 238 Lateral Cones 245 2. Explosive Eruptions 245 n. Metamorphism an Effect of Volcanic Conditions . . 254 IIL Form of Mount Loa 256 D. Relations of Kilauea to Mount Loa 258 E. Contrast between Mount Loa and Volcanoes of the Ve- suvius Type 265 II. Islands of Maui and Oahu 269 A. Island of Maui 269 1. East Maui 273 2. West INIaui 280 3. The Eccentric Form of the Maui Volcanoes .... 281 4. Consolidated Drift-sand Ridge 282 B. Island of Oahu 282 1. Features, Structure, and Origin of Oahu 285 2. Tufa and other Lateral Cones of East Oahu . . . 292 3. Evidence of Recent Change of Level 302 TABLE OF CONTENTS. XI Page III. Islands of Kauai and Nihoa 305 A, Kauai 305 The Interior of Volcanic Mountains 312 Elevation of the Island 315 B. Nihoa, or Bird Island 317 IV. Petrography of the Hawaiian Isla^ids, fy Edward S. Dana . 318 Mount Loa : Lavas of its Summit Crater, Mokuaweoweo, AND of its Lava-streams 319 Lava-stalactites from Caverns in Mount Loa Lava- streams 332 Lavas of Kilauea 342 Relation between the Rocks of the Summit Crater of Mount Loa and those of Kilauea 347 Lavas of Maui 349 Lavas of Oahu 353 part ^l)iri3. Volcanoes and Deep-sea Topography. The Bathymetric Map, and the General Features of the Oceanic Depression displayed by it 358 The Feature-lines of the Oceanic and Bordering Lands . . . 360 Facts bearing on the Origin of the Deep-sea Troughs .... 363 A. Facts apparently favoring a Volcanic Origin 363 B. Facts from the Vicinity of Volcanic Regions apparently not referable to a Volcanic Origin 365 C. Facts from Regions not Volcanic which are unfavorable to the Idea of a Volcanic Origin 366 D. Arrangement of the Deep-sea Troughs in the Halves of the Oceans pointing to some other than a Volcanic Origin 369 Conclusions 370 part iTourt!), Denudation of Volcanic Islands ; Its Amount a Mark op Age 373 Index 393 LIST OF PLATES. Page I. Map of Hawaii, reduced from the Map of the Hawaiian Govern- ment Survey Frontispiece II. Sketch of the Crater of Kilauea in 1840, by J. Drayton .... 33 in. Map of Kilauea, by Emerson and Dodge, of the Hawaiian Govern- ment Survey 98 IV. View of North Part of Debris-cone in Halema'uma'u. January, 1887 103 V. View of Debris-cone in October, 1886 107 VI. View of Debris-cone in the Spring of 1887 Ill VH. Lava-floor of Kilauea H*^' VIII. View of Debris-cone of September, 1887 -1-1 IX. Map of Kilauea, combining Part of Wilkes's and Brigham's Maps with that of Plate III 140 X. Map of Mokuaweoweo, by J- M. Alexander ........ 181 XI. Lava-cascade in the Lava-stream of 1880-1881 207 XII. Lava-fountain of January, 1887 213 XIII. Map of the Island of Maui, from the Map of the Hawaiian Govern- ment Survey 271 XIV. ;Map of the Island of Oahu, from the ]\Iap of the Hawaiian Govern- ment Survey, witli Views of some of its Tufa-cones .... 283 XV. Lava-stalactites from a Cavern in the Stream of 1880-1881, near Hilo 333 XVI. Bathymetric Map of the Oceans , 355 LIST OF ILLUSTRATIONS IN THE TEXT. Page Aa Lava-field 10 Map of the Hawaiian Islands 26 Sketch of the South End of Kilauea, by Ellis, engraved by Mr. Jocelyn of New Haven, Conn 46 Ellis's Sketch, as engraved in England 47 Ellis's Sketch, as engraved for his " Polynesian Researches " 50 Map of Kilauea, by Lieutenant INIalden, R.X 51 View of Kilauea, by R. Danijiier 52 View of South End of Kilauea, by Ca[itains Chase and Parker 60 Map of Part of Hawaii, illustrating the Eruption of 1840, from the Map of Hawaii of the United States Exploring Expedition under Captain Wilkes , 62 Tufa Hills of Nanawale, 1840, from Drawing by the Author ..... 04 Map of Kilauea in 1840, by Captain Wilkes 06 Driblet-cone in Kilauea, November, 1840 71 Map of Kilauea, by T. Coan, illustrating the Overflow of Lava and Canals of 1844 75 Map of Kilauea in 1846, by C. S. Lyman 79 Map of Kilauea in 1885, by William T. Brigham 84 Driblet-cone of 1864, by William T. Brigham 85 View of Kilauea in 1864, from a Painting by Mr. Perry 87 Trunk of Tree encased by Lava 91 Mapof Kilauea in 1874, by J. M. Lydgate 93 Floating Island in Halema'uma'u, Kilauea . * 99 Floating Island Stranded 100 Map of Halema'uma'u and South End of Kilauea in 1886, by J. S. Emerson 102 View of Debris-cone in Halema'uma'u, August, 1887 113 Wrinkles or Tapestry-like Folds on the Surface of a Lava-lake . . . . 117 Dome-like Elevation of Lava in Kilauea 118 Map and Sections of Halema'uma'u and Cone 120 Sections of the Crater of Kilauea, 1823 to 1886 127 Sections of Halema'uma'u, by F. S. Dodge 129 Map of Kilauea, by Captain Wilkes 133 Map of Kilauea, by William T. Brigham . , 134 XVI LIST OF ILLUSTRATIONS IN THE TEXT. Page Map of Kilauea, by C. S. Lyman 139 Magnified Views of Pele's Hair, by C. F. W. Krukenberg 161 Thread-lace Scoria 164, 165 Diagram illustrating the Origin of Lyman's Ridge ......... 173 Map of Mokuaweoweo, of the Wilkes Exjjloring Expedition 184 Source of Lava-stream of 1880 205 Aa Lava-stream 241 Tarawera Geyser and Volcanic Region, New Zealand 247 Diagram showing the Combinations of Volcanoes in the Hawaiian Islands 259 Map of the Hawaiian Islands 261 Cones of Kaneohe Point, Oahu 300 View showing the Western Moimtains of Oahu buried at Base by Lavas from Eastern Oahu 301 Kahuku Bluffs of Coral-rock, Oahu 302, 303 Koloa Region of Craters on Kauai „ . . . 309 Bluff of Drift-sands, Kauai 316 Feathery Forms of Augite in Mount Loa Lavas 321, 322 Chrysolite Crystals of IMount Loa Lavas . 325 Microlites of Lavas . 331 Enlarged Views of Lava-stalactites 336, 337 Sections of the Stalactites and Outline of a Crystal of Feldspar .... 338 Outline of a Twin Crystal of Feldspar from Maui 352 IMap of Tahiti 375 The Crown at the Head of Papiete Valley, Tahiti ......... 376 Outline Sketch of Orohena and Pitohiti 378 Diagram illustrating River Erosion, New South Wales 390 CHARACTERISTICS OF VOLCANOES. pan fxY^t VOLCANOES. I. GENERAL CHARACTERS. A VOLCANO is a mountain or hill, more or less conical in shape, which has a nearly central cavity at top, called a crater, and which discharges at times melted rock, called lava, and also vapors or gases. The lava either Jioivs down this or that side of the mountain in streams, of is projected into the air to fall around the vent, or lava-source, in fragments. The cooled fragments from a projectile dis- charge are called volcanic cinders, but the finer part, often, volcanic ashes ; if not cooled on the descent, they are drops or driblets. Since the accumulation of rock-material, whether due to descending streams of lava or to projected fragments, is made around a central lava-source, or is j^eincentric ^ in depo- sition, the hill or mountain built up takes the form of a more or less regular cone ; and a crater exists in its top be- cause of the discharges of lava and vapor from the lava- source within or beneath it. A volcano, as long as it is active, has thus — (1) its vapor or gaseous discharges; (2) its flowing lava-discharges; and (3) its projectile discharges. ^ Derived from the Greek rrepi, about, ami Kivrpov, a centre. 2 CHARACTERISTICS OF VOLCANOES. When discharges of liquid lava take place, or unusual pro- jectile discharges, or both together, the volcano is in erup- tion. Such eruptions result in emptying or deepening the crater. They may occur at intervals of three or four years, but often scores intervene. In the interval between erup- tions, the deepened crater may be for a while wholly quiet. But sooner or later, in the active volcano, vapors begin to rise from fissures, and small lava-flows and projectile dis- charges take place over the bottom ; and this continues, perhaps with interruptions, until ready for another out- break. In projectile discharges the height to which the fragments are projected into the air may be several thousands of feet during a great eruption, and hundreds or scores of feet in the interval. But in volcanoes of the Hawaiian kind the lava is ordinarily thrown to so little height that the frag- ments are not cooled on the descent, and no cinders or cinder-cones are made ; they are thrown up like the small jets over a boiling liquid. Yet even in such volcanoes lat- eral and terminal cinder-cones under some circumstances are formed. At an eruption the discharged lava may flow from the summit crater in great streams down the mountain ; or, sec- ondly, it may escape to the surface of the cone through fis- sures in the mountain's sides, made by the eruptive forces, and thence spread away in streams ; or, thirdly, it may flow oft' through fissures into cavities between the old lava-streams of the mountain, or force its way between the layers, and not show itself anywhere at the surface ; or, fourthly, it may only fill fissures made below by the volcanic action. Dis- charges of the first kind are superjluent discharges ; those of the second, effluent, or out of fissures ; those of the third, interjiuent. But for the third and fourth kinds all that can commonly be said is expressed in the word subterranean. Superfluent discharges are probably the prevailing kind at CHARACTERISTICS OF VOLCANOES. 3 the comnienceiiient of a volcano, the lavas then pouring out copiously from the vent or over the brim of the crater. But at the present time the discharges are effluent, or from fis- sures, though often also subterranean. The outflow from fissures may take place at any height on the mountain, from the top to the base, and also beneath the sea-level.^ If the latter, the eruptions are auhmarine ; if the former, suhaerial. The fissures from which outflows take place are sometimes so wide at some spots as to pour out the lavas from these places for weeks, so as thereby to make cones of lava ; or if the lava ceases to flow out, they may have projectile dis- charges for a time and make cinder-cones. In either case a line of cones may be formed on a fissure. Such cones while in action are true volcanoes in all their characters. They are distinguished as the lateral cones of a volcano or volcanic mountain.'^ The extinct lateral cones of a sub- marine eruption often stand as islands, or make shoals, off a coast. The regions of exhausted volcanoes, and sometimes the borders of active volcanoes, may have fissures that give out hot air, vapors, and gases in a quiet vv^ay, and that make de- posits of sulphur, alum, gypsum, or other minerals about the sides of the fissures or in the soil. Such regions are called solfataras, from the Italian for sulphur ; and the vapor- emitting fissures are called fumaroles, from the Latin for smohe. The heat of fumaroles may be as high as 750° F. Lava-caverns in and about craters often receive hot vapors, and have similar incrustations ; and sometimes they are hung with lava-stalactites. ^ The sources and courses of several great lava-streams are shown on Plate I. (trontispiece), the clotted belts representing the streams. ^ Many lateral cones are shown on the map of Maui, Platu XII. CHARACTERISTICS OF VOLCANOES. II. VOLCANIC ROCKS, GASES, AND LAVA-STREAMS. 1. Volcanic Rocks. — Lava is a general term for any rock of a lava-stream. It may be very compact. — that is, without a cellule ; or it may contain air-cavities or vesicles that were made by expanding vapor while the lava was still liquid, and so be a vesicular lava. But vesicular lava may be very openly vesicular, like a furnace slag, and then it is scoriaceous lava ; or it may be made chiefly of vesicles, and then it is a scoria, the scum or froth of the liquid lava. Lava, on cooling rapidly, sometimes becomes glass, or has a thin glassy crust ; but on cooling slowly^ the same material may become stone, by the conversion of glass into stony par- ticles, which are the constituent minerals of the lava. The lighter scoria of a volcano is mostly glass. Generally, but not always, minute portions of the glass remain in the most solid lavas. By extreme slowness of cooling, such as may occur in Nature in the interior of great igneous masses or under a deep covering of rocks, the texture of lava may be- come coarsely crystalline, like granite or syenyte ; so that, although granite has little resemblance to ordinary lava, it may be as truly an igneous rock as the lavas of Kilauea or Vesuvius, and, as Judd, Hague, Iddings, and others have shown, be part of the same eruption with scoriaceous lavas. ^ The more common kinds of lava consist as follows : — I. Of feldspar, as the chief ingredient. II. Of a feldspar, with one of the two iron-bearing min- erals, augite, hornblende. I. Lavas consisting chiefly of a Feldspar. — These lavas are generally light in color and light in weight. The specific gravity is 2.5 to 2.8. The feldspar is ordinarily orthoclase or potash-feldspar. ^ See page 314. CHARACTERISTICS OP^ VOLCANOES. 5 A coinmun kind, breaking with a rough surface of fracture and little lustre, is called Trachyte ; some black hornblende crystals are often present, and tables of feldspar called sani- din, and rarely small crystals of black or brown mica. If it contains quartz dissemmated through it, visibly or not, it is named Rhyolyte (from the Greek for to flovj) or Quartz- trachyte ; when in the form of glass, it is Obsidian ; when partly glassy, and therefore pitch-like or resin-like in lustre, it is Pitchstone ; when a fine light scoria, Pumice. A rock having the composition of trachyte or quartz- trachyte, but smooth, flint-like, in surface of fracture, is called Felsyte ; and wdien coarsely crystalline, the feldspar being in crystalline grains, and the quartz in visible grains, it is called Granulyte ; and the latter, when mica is present, is the common crystalline rock called Granite." A felsyte spotted with whitish feldspar crystals is a variety of Por- pliyi-y, or a j^orphyritic Felsyte. Leucite, a potash-bearing mineral related in composition to orthoclase, is prominent in some volcanic rocks. Its crystals are twenty-four-sided garnet-like forms. It is called leucite, from its whitish color. A leucite-rock occurs in Wyoming, and another kind is common at Vesuvius. II. Lavas consisting of a Feldspae and other Ingre- dients. — In the other common igneous rocks the feldspar may be (1) ortliodase ; (2) oligoclase, which contains the alkalies, soda and lime, with more soda than lime, — or the related andesine ; or (3) labradorite, which also is a soda- lime feldspar, but with more lime than soda. 1 . Tlte Orthoclnse and Hornblende or Augite Rocks. — These rocks are Syenyte, Quartz-syenyte, Augite-syenyte, and some others wdiich are not among the rocks of ordinary lavas. Leucite and augite are the chief constituents of Amphi- genyte (or Leucitophyre), tbe rock of the Vesuvian lavas just alluded to. 6 CHARACTERISTICS OF VOLCANOES. 2. Oligoclase Rocks. — A coiniiion lava of this group, of light to dark gray and greenish color, is called Andesyte, from the Andes. It consists of oligoclase or andesine and hornblende. A related rock, Angite-andesyte, consists chiefly of oligoclase and aiigite ; and where hypersthene, a mineral related to angite, replaces the latter, another variety is produced. When a rock of the composition of andesyte has a com- pact or a crystalline-granular texture with none of the aspect of a lava, it is called Dioryte. Its common colors vary from whitish to greenish-black. A compact red dioryte, with part of the feldspar in small whitish crystals, is the Red Porphyry of the ancients. 3. Labradorite Rocks. — Basalt and Doleryte are common lavas of this group. Doleryte (or Diabase) consists of la1)ra- dorite and augite, with more or less magnetite, and is a heavy dark-colored rock, with the specific gravity 2.9 to 3. Basalt is the same rock ; but it contains, in addition, chryso- lite (olivine), a mineral looking much like grains of green bottle-glass, with the specific gravity 2.D to 3.2. The angite is not unfreqnently in distinct black crystals, and the kahra- dorite in white or whitish crystals. These rocks are com- monly very fine-grained, and vary from compact to vesiculated, scoriaceous, and scoria. But doleryte and basalt vary also, on the other side, without cliange of composition, to coarsely crystalline rocks, the common Ivind of which is called Gabl)ro. In another labradorite sei'ies the rocks consist of labra- dorite and hornblende. They resemble dioryte, and one kind is called Labradioryte. The green porphyry, or oriental rcrd antique of the ancients, is a handsome porphyritic variety of the rock. Other igneous rocks have anorthite or nephelite, as prom- inent constituents ; or they may consist chiefly of augite, hornblende, or chrysolite. On this subject of volcanic rocks reference shoidd be made to works on petrology. CHARACTERISTICS OF VOLCANOES. 7 The most fusible of coniiuon lavas is doleryte or basalt, the temperature of fusion being between 2000° F. and 2500° F. Trachyte and rhyolyte are among the least fusi- l^le, and andesyte is intermediate in degree of fusibilit3^ A columnar or "basaltic" structure, more or less perfect, is very common hi solidified lava-streams, as a result of con- traction on cooling. Even the most recent lavas may exhibit it. It is most common in basaltic rocks, but occurs also in other kinds, even in obsidian or volcanic glass, as described by Iddings from the Yellowstone Park. Tufa. — Tufa, or tuff, as its method of formation implies, is nothing but a fragmental rock of volcanic origin, — a kind of argillaceous sandstone made out of volcanic ashes usually half decomposed. Its colors vary from gray to yellow, brown, and reddish-brown. The brown and brownish-yellow colors depend on the hydrous iron-oxide (Fe203 + Aq) present as a result of alteration. It some- times has a lustre almost like that of a resin, as is well ex- emplified at the quarry on Punchbowl, Oahu. The material, which was originally like powdered lava in composition, has been changed by the heat and moisture. The rock in this state is called j)ala(jonite. Besides the finer kinds, there are also coarse conglomerates among fras-mental volcanic rocks. The " cinders," or scoria, of a cinder-cone are often of a bright red color ; and this is due to surface decomposition of the augite producing the red iron-oxide (hematite or red ochre, Fe203). When the decomposition goes on in the presence of moisture, the color is usually yellowish-brown, from the production of the hydrous oxide above alluded to (Fe^O;^ -j- Aq, or limonite). 2. Yapoes or Gase.s. — The vapors which are emitted by the liquid lavas of the volcano are at least ninety-nine per cent steam, or vapor of water. There is never any true smoke. The amount of vapor given out is large in periods 8 CHARACTERISTICS OF VOLCANOES. of special activity, and clouds consequently are made over the mountain in the cool air above. Sulphurous acid (SO2) is probably the most common of the vapors next to that of water. It has the smell of burning sulphur. H3drogen is one of the gases that escape from the liquid lava, and its occurrence is attributed to the disso- ciation of the elements of water (HgO) by the extreme heat.^ Chlorine is emitted if sea-waters get access to the lava-col- umn, it being supplied in that case by the common salt of the sea (NaCl) ; and when present, chlorides occur as in- crustations on the lavas, among which are common salt, iron chloride, and others. Flames attributed to the com- bustion of free hydrogen have been observed. Other gases are only very sparingly present in the liquid lavas, but occur in solfataras or fumaroles. Hydrogen Sul- phide (H2S), or sulphuretted hydrogen, is sometimes detected, but not where the action is intense. Carbonic acid (CO2) may be given out if any limestone exists beneath the vol- cano. Hydrochloric acid (HCl) is another of the gases from the hotter fumaroles ; and nitrogen is sometimes present. Pyrite and marcasite, iron sulphides (FeS2), present in minute quantities in the rocks of the depths below the crater, are supposed to be the common source of the sul- phur and sulphur gases. Various deposits occur in solfataras and in caverns about volcanoes, produced by the escaping gases, of which the most common are the sulphates, — gypsum (hydrous calcium sul- phate), alums (hydrous aluminum sulphate, and aluminum- sodium sulphate), glauber salt (hydrous sodium sulphate), which is common in Hawaiian hot caverns ; occasionally hydrous copper sulphate or blue vitriol. The gases decom- pose the rocks to earth. Incrustations of sulphur are com- mon, and occasionally large deposits are made. ^ Foiique, Santorin et ses Eruptions, Paris, 1879; Siemens, Monatsb. K. Preuss. Akad., 1878, from investigations at Vesuvius. CHARACTERISTICS OF VOLCANOES. 9 3. Lava-streams. — Lava-streams are of two kinds. (1) There is the ordinary smooth-surfaced lava of volcanoes. It is the pahoeUoe of Hawaii, the term signifying '' having a satin-like aspect." The surface of the lava shows, by the fine and coarse flow-lines over it, that it cooled as it flowed. 'Through one means and another the surface is usually un- even, being often wrinkled, twisted, ropy, billowy, hummocky, knobbed, and often much fractured. Plate VIL shows some- thing of the uneven character, but not the larger irregularities. The streams have sometimes ii Arm glassy exterior half an inch or less in thickness. When lava overflows from a boiling lava-lake, it cari'ies jilong a surface scum one to three or four inches tliick, which is a glassy scoria, usually easily separable from the more solid and chief part of the lava-stream. The crusting over of a stream while it is still flowing, owing to contact with the air above, results in the leaving of empty tunnel-like caverns, which are sometimes hung w^ith stalactites. (2) The other most prominent kind of lava-stream is the cm. The aa streams have no upper flow-like surface ; tliey are beds of broken up lava, the breaking of which occurred during the flow. They consist of detached masses of irregu- lar shapes, confusedly piled together to a height sometimes of twenty-five to forty feet above the general surface. The size of the masses is from an inch in diameter to ten feet and more. The lava is compact, usually less vesiculated than the pahoehoe, not scoriaceous ; but exteriorly it is roughly cavernous, horridly jagged, with projections often a foot or more long that are bristled all over with points and angles. In some cases ragged spaces extend along planes through the large masses, like those of the exterior ; but in these, as in other parts, it is evident that the agency was tearing and up-ploughing and cavity-making in its action, and not vesiciflating. Occasionally (as well seen west of 10 CHARACTERISTICS OF VOLCANOES. Piiiialuu, on southern Hawaii) great slab-like masses of very compact rock, twenty feet or more long, eight feet high, and three to ten inches thick, stand vertically together, with a curving over at top, somewhat like gigantic shavings. Sim- ilar slabs are mentioned, as occurring on the Kilauea lava- stream of 1840, on page 63. The above figure represents the features of such a stream. The title of such piles of blocks to the name of a stream w^ould not be admitted were it not proved that they are formed during the progress of a lava-flow ; that a lava- stream may change from the suiooth-flowing or pahoehoe con- dition to the act, and back again to the smooth-flowing ; and that the same vent may give out at one and the same time a smooth-flowing stream in one direction and an aa stream in another. Lava of the aa kind occurs at Vesuvius, as well described by Sir William Hamilton in 1779, and later by •other authors. The aa streams are remarkable also for the presence of lava-halls of concentric structure that have been wTongly called bombs. These lava-balls are smoothish exteriorly, more or less rounded and bowlder-like, and vary in size from an inch or less to ten feet and more. One of them is repre- sented in the aa picture, at the top to the right. Some of these lava-balls have, outside, a crust of hard lava, and, inside, fragments of scoria or grains of chrysolite (olivine) ; others consist of concentric shells, hard and scori- CHARACTERISTICS OF VOLCANOES. 11 aceous shells alternating with one another. One on Hawaii near Punalim was found to have a nucleus of scoria eighteen inches in diameter, and around this successively a stony shell of three inches, a scoriaceous layer of one to two inches, a stony shell of four to five inches, and then outside a rough lava shell six inches thick. One of large size, broken open on one side, had had its inside filling of scoria worked out by the natives, and so made into a small cave.^ A common size on Hawaii is three to five feet in diameter ; but one enor- mous lava-ball, in the aa field west of Punaluu, measured 24 X 12 X 9 feet in its extreme dimensions, and contained at least a thousand cubic feet. Enough of its hard outer shell was pealed off to ascertain that the second layer was quite vesicular or scoriaceous, and the next layer inside hard basalt again. These Hawaiian lava-balls lie in the midst of the other blocks of the an stream, proving that all had a common origin, and tliat they are not ijrqjected homhSy and hence properly not bombs at all. The so-called '* l)ombs " of Vesuvius have been shown in- dependently by Dr. Johnston-Lavis, of Naples, to have had essentially the same origin.^ III. FORMS OP VOLCANIC CONES. The volcanic cone or mountain takes its shape partly from the nature and condition of the material of whicli it is made, partly from the position of the places of outflow, and partly from the copiousness of the flow. Other causes — as sul)- sidences and uplifts — may modify the forms ; but the forms not so modified are those here considered. If the lava were as liquid as water, cones of sensible slope 1 American .Journal of Science, 1887, 3d series, xxxiv. 364. ^ Johnston-Lavis, in a paper on " The Fragmentary Ejectanienta of Volcanoes," in the Proceedings of the Geologists' Association, London, vol. ix. no. 6, and Ameri- can Journal of Science, 1888, xxxvi. 103. 12 CHARACTERISTICS OF VOLCANOES. would be impossible. Lava has various grades of viscidity or liquidity ; and in the most liquid stage — that which ex- ists when the heat is at or above the fusing-point of the essential ingredients — there is still a degree of viscidity or cohesion sufficient to cause some resistance to free move- ment, and hence a slope in the upper surface of the flowing stream. From this stage of most perfect mobility there may be all grades of viscidity, in consequence of partial cooling, — cool- ing producing incipient and finally complete solidification. If melted beeswax were poured out on a fiat surface while heated above the fusing-point, it would flow off at a very small, angle ; and a very copious flow would be impeded neither by cooling below against a cold surface nor above against the air. But if the temperature were below that of fusion, the liquid beeswax would be pasty, and the angle of flow or of the pitch of the upper surface wolild increase with decrease of temperature. Copious streams would have the smaller angle ; while small streams would give ^increased pitch, and drops might make a vertical column. The facts are the same in principle with lava. Basaltic lava in the state of most perfect liquidity flows at an angle much less than that of 1°, as is shown by the surfaces of the great basaltic floods in the Snake River region and others on the Pacific border slope of North America, as well as 1)y the occurrence of a pitch of 1" and less in the lava-streams of some of the Hawaiian Islands. Copious flows — such as have occurred in the earlier dis- charges of a volcanic vent — may therefore make basaltic cones of I" and less. But the flows of modern volcanoes are not ordinarily of this copious kind. The lava of an eruption is discharged in portions at intervals of hours or days or weeks, and the streams become cooled at bottom and cooled at top, so that only the interior flows on in a kind of tube or tunnel, and this, as it emerges below, takes CHARACTERISTICS OF VOLCANOES. 13 its chances of cooling. The streams are narrow strips down the cone. They come out usually from fissures, and at all heights between the top and the bottom. The resulting angle for a basalt-volcano becomes thereby 1° to 10°, and rises often to 90° in the driblet cone. With the less fusible lava the cones are of steeper angle than with basalt, since the high temperature of fusion gen- erally fails of being supplied from the depths below, and is more easily lost by cooling; and the lava therefore is com- monly more or less pasty. The andesyte cones of western North and South America are 25° to 34° in slope. Since a cone diminishes in diameter upward, a flow of lava from near the summit liaving like width throughout would cover a much larger part of the circumference in the upper part than in the lower. The part of the cone below would require in fact a great number of ordinary streams to make one coat over the surface. The consequence of this condition is that such discharges make the cone steeper above, and give it a concave outline. But if the flows commence for the most part a little below the summit, from an eighth to a sixth of the height, the upper part would be widened and the cone take the form of a low dome, like Mount Loa ; or if the streams come from fissures in the lower part of the cone and spread beyond the base, the cone will be flattened below, and the lower part of the profile will be made concave. The possible slopes of the sides of cinder-cones may be learned from a very simple experiment. If circles half an inch apart are described about a centre on a large card, and a slender graduated rod is inserted vertically at the centre as an axis to the figure, then by dropping dry sand, fine, coarse, and angular, in successive trials over the axis, the slope at wliicli the different kinds of sand come to rest by gravity, under resistance from friction, may be readily obtained and compared. If enough wator is mixed with the finer sand or earth to make it flow like thin mud, the angles of different- 14 CHARACTERISTICS OF VOLCANOES. liovviiig muds may be obtained. Such trials show that an angle of 40° is as great as should occur with dry cinders, un- less the fragments are very irregular and light ; tiiat with fine dry sand it may be as low as 25° ; and that an angle of 15° is not too small for a flowing mud, though steeper slopes may also occur. Cinder-made cones are usually between 3fh' and 4(J" in angle ; but they vary in heiglit, breadth, and slope on the dif- ferent sides, according to the direction of the prevalent winds. Alternations of cinder and lava ejections will mal^e a cone of steeper slope than lava alone ; and this may be part of the reason for the high angle of slope of the volcanic mountains of western America. Summit ejections of cinders may increase height without adding much to the mass of a mountain. .Flowing muds are made out of volcanic ashes or cinders when waters descend in torrents during copious violent pro- jectile eruptions. The stream of mud so produced may flow off at a small angle of pitch, and make a low-angled, broad- topped cone, with a broad, saucer-like crater, — a tufa-cone. If the vent is at the sea-level or a little below it, so that the sea-water would be made to boil up by the heat of the vent and escape with the projected cinders or ashes, the mud- stream would flow directly from the interior of the crater. Punchbowl, Diamond Head, and the hills of Koko Head, figured on Plate XIV., are examples of tufa-cones. By making an outline of a section of a cone and drawing lines parallel to the sides, the usual figure of a section of a lava-cone or cinder-cone is obtained. But as lava-streams are to a large extent strips or patches of lava over the surface, the diagram conveys a wrong impression, since it seems to imply that the cone consists of a regular series of coats. In a tufa-cone there is a slope beneath the crater, as well as down the outer surface, — a structure illustrated in the left of the Koko Head craters on Plate XIV. METHODS AND CAUSES OF VOLCANIC ACTION. 15 Ejections of volcanic cinders or ashes from the chief vent or crater of a basalt-volcano are generally of small amount ; but they may make beds a thousand feet or more thick about volcanoes of other kinds. NoN- Volcanic Igneous Ejections. — Ejections of melted rock like those of volcanoes, and of great extent, have often taken place without volcanic agency. Fissures have opened in the earth's crust and let out liquid rock, sometimes with little overflow or none, but sometimes spreading over thou- sands of square miles. Occasionally the lavas have been forced in between the beds of rock of a reo;ion so as to make great intercalated sheets, or have thickened up under the cover of other rocks into great dome-shaped masses, over a thousand feet thick, called by Prof. G. K. Gilbert " lacco- lites " (laccoliths). A fissure in a case of ordinary non-volcanic igneous ejection affords its single outflow, and thus differs from a volcanic vent. Fissure may succeed fissure, however, and great thickness of beds be attained in the region through the successive discharges. But there could be no pericentric ar- rancrement of the beds, or a hio;her central resrion, unless the Assuring be subordinate to a central vent ; and in this latter <3ase the ejections would be distinctively volcanic. But the characters of the flows and of the rocks are essentially the same, whether from fissures about a volcano or from those of non-volcanic regions. IV. METHODS AND CAUSES OP VOLCANIC ACTION. The Sup2)lyirig of Lava. — A continued supply of lava from depths below is required for volcanic activity, since an enormous loss of lava takes place at an eruption. Moreover, the supply-channel, or conduit as it is often ■called, must reach down to a region of perpetual heat and 16 CHARACTERISTICS OF VOLCANOES. fusion. For the liquid column loses heat, owing (1) to con- tact with the cool rocks alongside of it ; (2) to the expan- sion of vapors or vaporizable material within the lava (all such expansion using up heat), which expansion becomes of large amount near the surface, as the superincumbent pres- sure in the liquid becomes small ; and (.3) to contact at surface with the air. This supply of liquid rock from a deep-seated source sup- poses some upthrusting force or forces, sufficient to push the lava up to the level of the bottom of the crater. If the level reached is much below the earth's surface, say some thousands of feet, the melted rock might be a source of heat for any waters that may descend to it from the surface to bring it up, and might thus make hot springs or geysers, or at a higher level might produce a region of escaping vapors called a soJfatara. For volcanic action, the ascensive force, or combination of forces, must be sufficient to restore the lava-column to its mean height sooner or later after every eruption ; for failure here is the beginning of decline in volcanic activity. When a volcano ceases action entirely, not even vapors escaping, it is said to be extinct ; but it may not always be so dead that a century later it will not break out anew. The Work inaicU the Grater at the Extremity of the Lava- column. — The work done in a crater is largely due to the expansive force of vapors, and directly to the making and escaping of vapors. For if all vaporizable material were absent, the lavas would lie quiet, and an eruption, if it w^ere a possibility, would be simply a running over. Whenever, in the bottom of a crater or in any part of it, liquid lavas are visible, they are always found to be in constant activity ; and if not actually in sight, there is usually considerable noisy ac- tion from the escaping steam, and from t he movements below which it occasions. The escape of vapor encounters resistance in consequence METHODS AND CAUSES OF VOLCANIC ACTION. 17 of the cohesion of the liquid material, which resistance is proportional to the strength of this cohesion, or is conversely as the degree of liquidity. Water, in boiling, lets very small babbles of steam through easily ; and the elastic force of the steam of the bubble makes low jets, the height only one or two inches. But to overcome the resistance in lava and break a way through, the elastic force of a small bubble of vapor is too feeble ; the bubble, tlierefore, keeps enlarging by additions until the force is sufficient to overbalance the resistance ; and then comes the break of the liquid lava-shell of the bubble, and the projection of its fragments verti- cally or nearly so into the air, — vertically, because the shell is thinnest at top. The projectile force thus depends (1) largely on the size of the Imbljle, or, what is the same thing, on the viscidity of the liquid lava ; and also on the supply of vapors seeking to escape. On account of the remarkable liquidity of basaltic lavas, the projectile force required to break a way through may be so small as to throw the lava to a height of only a few yards, as in Kilauea, — a height so small that the projected drops or masses of lava fall back unsolidified, and the jets dance in a lively and brilliant way over the surface of the lava-basin, like those over a boiling vat. Where the surface of liquid lava is small, as in half-covered oven-like places about the sides of a basin, the escape of the vapors produces a throw oi fiery spray. Again : where such lavas are jetted out of small apertures, the driblets fall back upon one another, and, becoming sol- dered together, make fantastic driblet-cones. (Figures are given on pages 71, 85.) The projecting steam, in such cases, often escapes from the aperture with a rush like that from a steam-engine ; hence the terms hloiv-hole and bloivi?ig-cone. But when the liquid lavas are of the stiffer sort, the bubbles have to become large before escape of the vapor is possible : 18 CHARACTERISTICS OF VOLCANOES. and then, on breaking, the explosive force projects the frag- ments of the hiva-shell to a height of hundreds or thousands of feet. The projected fragments, cooled in their flight, are the volcanic sand or dust, cinders or lapilli, which, in falling, make the cinder-cone about the vent, or cover slopes or the country about the volcanic mountain with thick deposits of loose volcanic ashes or scoria. Such high projections have occurred under rare conditions in connection with the Hawaiian volcanoes. They are the common fact at most volcanoes ; and it is well known that in some eruptions they reach a height of ten thousand feet and beyond. Great viscidity, while leading to the production of large size in the vapor-made bubbles before they are ready for explosion, makes fewer of them to form over a given sur- face of liquid lava ; and in times of moderate activity the number may be only half a dozen or only a single one at a time, while on a like area lavas with the Kilauea degree of viscidity would have scores or hundreds. When the author was at Naples, in May of 1834, there was at night an interval of seven to eight minutes between the explosions, or the throw (some hundreds of feet in height) of fiery cinders; on the ascent, the following day, the interval was four to five minutes ; and on passing Stromboli, a fortnight later, June 16, it was fifteen to twenty minutes, — the activity being- less than usual; explosions every two or three minutes being common. As Spallanzani, Hofmann, and others have seen the rising bubble within Stromboli, the bursting, and, follow- ing this, the rush of vapor and the cinder projections, there is no reason to doubt that at Vesuvius, also, each throw of cinders has the same source. Mr. John Milne states that on his ascent of the Japan volcano, Oshima. in May, 1877, on approaching the top, successive explosions were heard every two seconds with occasional pauses, which explosions he found, on reaching the top, to be due to successive outbursts of steam, each projecting ashes and lava-fragments to a METHODS AND CAUSES OF VOLCANIC ACTION. 19 height of nearly six thousand feet, that fell vertically unless wafted by the winds. ^ When the rains descend in torrents at a great eruption, these materials make the flowing mud that buries fields and forests, and has made fossils of cities, of which Herculaneum and Pompeii are examples. The vapor of water, as has been stated, is the chief part of the vapors expelled. Above the surface of liquid lava, from which it escapes, it is for some distance invisible, because the temperature of the liquid lava is near 2000° F. It becomes clouds by condensation at whatever height the required tem- perature is reached. For the supply of water, the sea may be a source ; and so also the rains, whence come not only the streams of the sur- face but also subterranean streams. The waters may descend deeply into the cavernous volcanic mountain. Approaching the hot rocks about the lava column, they would be thrown into steam, — a cubic foot of steam, if under the ordinary atmospheric pressure, to every cubic inch of water. So vast is the amount of vapor that would thus come from a small amount of water, that the vapor, unable to escape through the rocks, would be forced into the rising lavas of the con- duit. Moreover, a molecular absorption of vapor of water against the pressure within has been shown by Daubree to take place. Another source of water-vapor recognized among writers on volcanoes is the deep subterranean region which supplies the lavas. Further, if the fusion has been produced by the melting, through earth-movements or otherwise, of pre- existing rocks, the moisture of these rocks (perhaps half per cent of their weight) would be a source of rising vapors. Other effects of the vapors are these: (1) They enlarge, by their expansion, the bulk of the liquid lava, and may thus 1 Milne, "Volcanoes of Japan," Transactions of the Seismological Society of Japan, 1886, vol. ix. part ii. 20 CHARACTERISTICS OF VOLCANOES. increase the height of the lava-coliimn. (2) They make vesi- cles or air-cells in the lava. (3) They produce fractures in the walls of craters or in the sides of the volcanic mountain by the sudden generation or slower accumulation of large quantities within regions about or beneath the crater. (4) They may produce violent projectile effects when water in large quantity gains direct access to the lava-conduit. (5) They bring pressure to bear on surfaces of liquid lava be- neath, and often force the lava into opened fissures and up to levels hundreds of feet above the bottom of the cra- ter, acting here on the principle exemplified in a Pennsyl- vania oil-well. Progress toward an Eruption. — The crater, after it has been emptied by a great discharge at a time of eruption, often has, at first, a period of apparently extinguished fires, and something like the conditions of a commencing solfatara, through the lazy escape of vapors from the fissures and the lining of fissures with sulphur crystals. Next, little outflows of lava take place from apertures or fissures in some part of the bottom or floor of the crater, or driblets of lava or jets of cinders build a small cone about a vent. In the case of basaltic lavas, pools of boiling lava often appear in the crater, which frequently overflow and spread lava-streams over the floor, making thus small eruptions. In the case of the less liquid lavas the ejections at the bottom of the crater are mostly of cinders, and one or more cinder-cones are made thereby over the bottom ; but now and then es- capes of lava take place through fissures. The process is one that puts new material over the bottom of the crater and raises its level ; and it goes on at an increasing rate until the eruption commences. But this raising of the bottom by overflows and deposits of cinders is accompanied by the upward thrust of the lavas of the lava-column through the ascensive action already men- tioned. Owing to this ascensive action, aided by the ejec- METHODS AND CAUSES OF VOLCANIC ACTION. 21 tious, the floor of the crater keeps rising ; and sometimes, perhaps generally, the larger part of the floor is lifted or shoved up bodily by the lavas forced in beneath. By these methods the level of the floor in a volcano like Vesuvius may rise nearly to the very brink of the crater ; or, in one like Kilauea, at least some hundreds of feet. At such times the projectile action of the crater has be- come intense. Clouds rising in great volumes over the mountain are evidence of the activity, and an illuminated signal at night. The Eruption. — The eruption begins when the pressure from the vapors generated and confined below and from the hydrostatic pressure of the lava-column — chiefly the former — is too great to be withstood by the containing mountain. The mountain therefore breaks, the conduit is rent open on one side or the other, and the lavas run out. If the mountain is too strong to break, as it perhaps is in the earlier part of its history when it is of little height, the lava would rise to the top of the crater by the methods stated, and overflow on this side or that ; and thus the lava-flood would begin at the summit. But eruptions at the present day, as has been stated, are usually through fissures. The discharge of tJie lavas (1) empties the upper part of the lava-conduit or lowers the level of its upper surface, and (2) undermines the lifted crater-floor ; and the result may be (3) a collapse or down-plunge within the crater, making it again hundreds of feet deep, or a thousand, or two thou- sand, as the case may be. Part of the undermining at Vesuvius is due to outflow of lavas, part to discharge of volcanic cinders ; but at Kilauea it all comes, ordinarily, from the escape of liquid lavas. The collapse from the loss of lavas may be followed by a general chilling of the rocks down to the new lava-surface, and a long period of quiet. Before tlie mountain is ready 22 CHAKACTEKISTICS UF VOLCANOES. for another eruption the process of filling up again, b\' tlie methods described, has to be repeated, and this may take many years. An empty caldron will not overflow before its cracks are mended and the steam-apparatus at work has again filled it ; and it might be so badly cracked, and the supply of heat so cut off, as to fail of further use. Should the ascensive force for any cause cease to work, death would be sure. Earthquakes^ in connection loith Volcanic Eruptio/is. — When the breaking of the mountain is caused by vapors suddenly produced in large volume, and the resistance to fracture is very great for any reason, the vibrations attend- ing the rending may be vigorous, opening deep fissures, over- turning houses, and making underground rumblings. But in other cases the vibrations may be imperceptible, as is usually the fact both in Kilauea and Mount Loa at their greatest eruptions. SuborxUnate or Lateral Volcanic Cones. — Lateral volcanic cones are described, on page 3, as sometimes forming over fissures. Each such cone when it is in progress has its own lava-column, as a branch from the general lava-column of the mountain. But it is relatively small, and the liquid lavas consequently may soon become chilled by the cold rocks about it ; and hence such lateral or subordinate vol- canoes have usually only a brief existence. They, however, often work hard while the time lasts, and even in two or three weeks may make a cone many hundred feet or yards in height. They occur about the sources of great eruptions. But they are most common near the seashore, where subter- ranean fresh waters most abound for the supply of moisture, and where the sea is at hand as another source. The vol- canic origin of such cinder-cones can be proved, if a fact, by the pericentric arrangement of the materials constituting them. The sea. with its broad waves and the aiding winds, can make heaps or ridges out of the sands existing or pro- METHODS AND CAUSES OF VOLCANIC ACTION. 23 duced on its borders, but it cannot arrange the layers of sand or earth pericentrically into a conical hill. Explosive Eruptions. — When water in large volumes gains sudden access to the interior of a lava-conduit, — that is, to the liquid lavas of the lava-column, — the projectile force of the aljruptly generated vapors may be enormous, and produce projectile discharges of lava of terrific violence, covering a wide reach of country with volcanic cinders and ashes. More- over, great masses of solid lava may be torn off in such cases from the throat of the volcano, and add to the projections. Masses of a hundred cubic feet and more may be hurled for miles from the scene of explosion. Such an eruption is very unlike the ordinary kind described above. It is an exj^losive eruption. In some of the most violent of explosive eruptions no outflow of lava takes place. The projectile eruption is all, and this is soon ended. Some examples of such eruptions are described on a following page. Explosive eruptions of another kind, which might be styled semi-volcanic, are included among descril3ed volcanic phe- nomena. In such eruptions water in large volumes gains sudden access to the heated depths beneath an extinct or feebly active volcanic mountain through fractures or move- ments along planes of weakness, as in other cases ; but the heated depths are depths sliort of the 2000° F. or over re- quired for fusion. The consequences are earth-shakings, ex- plosions from the suddenly generated steam, the rending of rocks in the deep-seated region of the explosions, projectile action throwino; the stones and o;reat rock-masses so made and the dust from abrasion into the air and over the adjoin- ing region, attended by vast and violent effusions of steam, making darkness and terrific storms about the mountain, — and not outflows of lava nor the projection of volcanic ashes and scoria from cooled lavas. No liquid lavas are in any way directly concerned, and hence the eruptions are only semi- volcanic. They may get over their violence in an hour or less. 24 CHAKACTERISTICS OF VOLCANOES. Such projections make great cavities beneath, undermining the mountain ; and a down-plunge or subsidence of the moun- tain summit to hll the cavities should be a consequence. Since force acts most violently where the generator of the steam exists, as in other explosive eruptions, and compara- tively feebly after the vapors have made their escape into the open air, the chief destruction to the mountain cannot come from any blowing of steam, or air, or projection of rocks, against the outside walls or peaks. The origin of volcanic heat, the source of lava-eolimins beneath the volcano, the cause of the ascensive force in the lava- column are subjects on which science has various opin- ions and no positive knowledge. part ^cconD* CONTRIBUTIONS FROM THE HAWAIIAN ISLANDS TO THE SCIENCE OF VOLCANOES. 1'^HE Hawaiian Island group is an example of a line of g-reat volcanic mountains. Fifteen volcanoes of the first class have existed, and have been in brilliant action alonsji: the line. All but three are now extinct ; and these three are on the easternmost and largest island of the group, — Hawaii. Hawaii is made up of five of the vol- canic mountains, — Kea, 13,805 feet in height; Loa, 13,675 feet ; Hualalai, 8,273 feet ; Kilauea, 4,040 feet at the Vol- cano House, but 4,158 feet at the highest point on the west side ; and Kohala, 5,505 feet. But they have encroached much on one another by their eruptions ; and Kohala, the oldest and most northern, is largely buried by the lava of Kea. The island of Maui is a volcanic doublet. The eastern mountain of Maui — Haleakala, 10,032 feet high — looks as fresh in its lavas and as smooth in its slopes as a volcano still in activity. But the other mountain — that of western Maui or Eeka — has lost by long denudation its summit crater, its old even slopes, and a large part of the old cone. Oahu is another volcanic doublet ; and both its eastern and western mountains have, like Mount Eeka, lost the crater that was the great centre of action ; and besides they have lost much also by catastrophes of a subterranean source. 26 VOLCANIC PHENOMENA Still the lava-streams of the old cones may be made out on each, and in one perhaps the site of the ancient crater. Molokai is another volcanic doublet ; and probably also Kauai, although the larger part of the present island appears to belong to one great cone or dome. OF THE HAWAIIAN ISLANDS. 27 The group appears, in fact, to be a double line of volcanoes from Oahu eastward. One line, the northern, called the " Kea Range " from Mount Kea of Hawaii, includes the northeastern mountain of Oahu, Molokai, the two mountains of Maui, and Kohala and Kea on Hawaii ; tlie other, the '' Loa Range," includes the southwestern mountain of Oahu, Lanai, Kahoolawe, and the volcanoes of Hualalai and Loa on Hawaii. The island Niihau, at the west end of the group, southwest of Kauai, has a position transverse to that of the general trend of the islands. The depth of ocean about the islands, so far as soundings have been made, varies from 2,000 to 3,02o fathoms, as is shown on the map ; and as the cones stand on the sea- bottom, the whole heio-ht of the liioher mountains of Hawaii above the base to the eastward is not far from 31,000 feet. The Hawaiian group is an example of the lines of vol- canoes that characterize many island ranges over the globe and volcanic ranges over the continents. The volcanic features and phenomena of the Hawaiian Islands are described and discussed in the following pages from personal observations in 1840 and 1887, from the vari- ous records of others, and from the topographic surveys of the islands made under the direction of Prof. W. D. Alex- ander, Surveyor-General of the Hawaiian Islands. As the island of Hawaii is the held of existing volcanic fires, and therefore of greatest interest, the facts relating to it and the views on volcanic action thence deduced come first under consideration, after general remarks on the group, and then the results of observations on the other islands, and the relations of the group to the system of islands in the Pacific Ocean. ii8 VOLCANIC PHENOMENA. I. THE ISLAND OF HA WAIL General Observations. — A map of Hawaii makes the frontispiece to the volume. The island is approximately triangular, with its greatest length from nortli to south about ninety-three miles, and the extreme width eighty miles. It lies mostly between the parallels of 19° and 20° 20', and takes the trades on its northeast side. Many important facts may be read from the map at a glance. Among them the first to be noted is the simplicity of the topography and the gentleness of the mountain slopes ; secondly, the situation of the five volcanic mountains ; thirdly, the almost total absence of rivers, except on the north and northeast slopes, or the windward sides ; and fourthly, the courses of the great lava-streams of the past sixty years, indicated by long dotted areas. The Kohala Range, on the nortli, is the remains of the oldest of the Hawaiian volcanoes. The slopes are deeply cut by valleys of denudation. Between it and Mount Kea lie the broad plains of Waimea, 2.500 to 3,000 feet above tide-level, made by the lavas of the base of Mount Kea. On the north- eastward, the ocean side, there are the precipitous gorges of Waipio and Waimanu, 1,000 to 2,500 feet in depth, so pro- found and so bent around into parallelism with the coast that erosion cannot explain their origin. ]\Iount Kea has long been extinct, probably for centuries, yet not long enough for denuding action from the abundant rains over the windward slopes to extend the torrent chan- nels more than half-way to the summit. Mount Hualalai has been quiet since 1801, when the last eruption was wit- nessed by Turnbull. It is a question whether it did not reach final extinction as a consequence of that discharge. Its slopes so blend with those of Mount Loa that " it is hard to tell where one beorins and the other ends." Mount Loa THE ISLAND OF HAWAII. 29 blends in like manner with Mount Kea, but with a broader intervening plateau, about five thousand feet in elevation. The great Dome of Mount Loa ^ would have been the highest of the mountains, were it not for the last cinder- eruptions of Mount Kea, which ran up a cinder-cone to a height of one hundred and forty feet above it. Kilauea is twenty miles south of west from the crater of Mount Loa ; and although containing the largest crater of the group, the highest point is raised hardly three hundred feet above the plain between it and Mount Loa, and within two miles in that direction the Kilauea slope ends. In the op- posite direction Kilauea may claim the slopes to the shores, from Haena, southeast of Hilo, to the middle of the south coast within ten miles of Punaluu. Hawaii has no fringing reefs; only small patches occur here and there along the shores. The fact is a consequence of the destruction of life from submarine eruptions, and the encroachment also of subaerial lava-floods. It has therefore no first-rate harbor. That of Ililo is the best ; and the vil- lage of Hilo is consequently the chief settlement. The longest of Hawaiian rivers, the Wailuku, which follows in its lower part the meeting of the slopes of Kea and Loa, here enters the sea, and adds much to the capabilities and the beauties of the surrounding region. At the Pei-pei Falls above Hilo, it flows between high l)luffs of basaltic columns. Hilo is the usual starting-point for excursions to Kilauea. The old saddle-road is indicated on the map by a dotted line. The distance is about thirty miles. 174^ miles of it beyond the '' Half-way House." The new carriage-road, which follows nearly the same course, has reduced the time of the jour- ney, and added much to its pleasures. Another and a much shorter route is from Keauhou, on the southern coast. It makes the whole ascent of 4,000 feet in about ten miles' direct distance, or twelve miles by the road, rising 852 feet in ^ The words " Mauiia Loa " mean " Loiiir Mountain." 30 VOLCANIC PHENOxMENA. the first mile, and between the third and fifth miles (as the road goes) about 700 feet, which carries the road to the summit of the '' pali," or a long precipice that here extends along for more than twenty miles parallel nearly with the coast.^ A third route to Kilauea, and one of much interest, starts from Punaluu, on the southern coast, where there is a good hotel. The steamer to and from Punaluu passes around the southern cape, and affords a chance for a distant view of the lava-streams of 1868 and 1887, at the commencement of whose discharge earthquakes shook the whole island, and the southern half of it disastrously. Kealakekua, on the west coast, is the place where Captain Cook was killed by the natives in 1779. It is an interesting place geologically on account of the lofty cliffs that here face the sea, — evidence apparently of great fracturing and subsidence. The slopes of Mount Loa are under forests up to from seven to eight thousand feet on the north and east sides, and over much of the southeast to a line drawn from the summit through Kilauea, — the limit of the region struck by the trade-winds. The rest of the surface, with part also of the forest portion, is a nearly bare surface of lava-streams, either the pahoehoe or aa, with little shrub- bery. The fields of aa are the chief ol^stacle in an ascent to the summit outside of the usual track. As the jagged masses are from one cubic foot to ten thousand in size, and touch only by their points and edges, leaving deep recesses everywhere among them, any crossing on horseback, except by a made road, is impossible ; and the pedestrian has to 1 The road was made by the Wilder Steamship Company, and they publish the following as the levels of the road at each mile-stone along it, starting from Keauhou : 1st, 852 feet; 2d, 1,113 ; 3d, 1,841 ; 4th, 2,287 ; 5th, 2,504 ; 6th, 2,867 ; 7th, 3,204; 8th, 3,341; 9th, 3,395; 10th, .3,629; llth, 3,748; 12th, 4,008 ; 13th, 3,964 ;] 4th, 4,040, Volcano House. The Keauhou Eanch, a half-way house, is six miles from Keauhou Landing ; at nine miles the road sends off a branch to the southeast- ward to Puna. The Volcano House is under the direction of the Steamship Compnny. THE ISLAND OF HAWAU. 31 look to it that he does not miss his footing and break his limbs in a fall among the jagged masses. Moreover, some aa fields are so large that when upon them all in sight to the horizon around is gray and black desolation. The author made his first acquaintance with the two styles of lava-fields in 1840 on his walk from Kaulanamauna, on the southwest coast, to Waiohinu, Honuapo, Punaluu, and Kilauea. The pahoehoe also is exceedingly uneven, through its many rounded hillocks or domes (half of which are caved in), its ropy ridges, and its knobs and mouldings made by the extrusion of flowing lavas through the hardened crust of a stream ; but travelling over it is safe, and a mule will avoid the holes and crevices. The General Charactee of the Great Craters and OF the Facts they afford. — The active craters of the island — Kilauea, and Mokuaweoweo or the Mount Loa crater — are alike in being int-craters, or cratei's with mostly vertical walls without an enclosino; cone above the walls ; and these walls are made of the nearly horizontal edges of stratified lava-streams. A sketch of Kilauea, as it appeared in December, 1840, by Drayton, one of the two artists of the Wilkes Exploring Ex- pedition, is reproduced in Plate II. from the " Narrative of Captain Wilkes." ^ A knowledge of the features of the pit at that time is necessary to enable the reader to understand the history beyond. It was taken from the west angle of ^ Copied from the plate facing page 125 in the fourth volume of Wilkes's " Nar- rative." One or two points of geological importance were overlooked by the artist, which should be mentioned to forestall wrong inferences : One is the omission of the stratification of the wall, which is a marked feature ; and another is the giving a slight concavity to the floor of the crater in the northern or near part, which was not a fact. The small jets of vapor over the bottom arose at the time, with a single exception, from fissures or cavern-like openings; and such escapes of vapor are greatly multiplied by a rain. The exception was that of a lava-lake, about two hundred feet in diameter, named Judd's Lake in the "Narrative," which was the larger of two lakes tliat were active two months before, in November, 1840, at tlie time of the author's visit to the crater. o2 VOLCANIC PHENOMENA. the depression at the north end of the crater, and shows ad- mirably the condition of tlie pit. Its length then was four- teen thousand feet, as now ; but its depth to the bottom of the lower pit was one thousand feet. The broad, level platform between the lower pit and the upper wall, about six hundred feet below the top of ihe wall, is w4iat was then called the '' Black Ledge." At the present time, as shown on Plate III., there is no lower pit and no Black Ledge ; all is filled up to a higher level than that of the ledge, so that the greatest depth below the Volcano House is now but 482 feet, and the least about the centre of the pit is less than four hundred feet. The most active fires in 1840 were in the southwest part of the crater, as has been the fact through all the known history of Kilauea. The pit represented in the sketch to the left is the small crater of Keanakakoi, which is well shown in Plate III. The history of these volcanoes is such as has been sup- plied by no other volcanic region. Commonly it is the erup- tion that draws attention to the volcano ; and the course of the flow, the characteristics of the lava, and the devastations of the fiery stream and the earthquakes make up nine tenths of all the published facts. At Kilauea, on the contrary, it is a history of the iimer ivorkings of the volcano ; of the move- ments and changes that take place within the crater over the various parts of the great area, where come into view the outlets of the subterranean lava-column ; and of these events as steps in the line of progress from its emptied condition after a great eruption till ready again for an outbreak. In Vesuvius the crater may be accessible for a time after a discharge ; and Scacchi has done excellent work on such occasions. But in general, long before the time of eruption, the vapors and cinder ejections make access to the bottom impossible. The crater of ^tna is far away from habita- o B V THE ISLAND OF HAWAII. 35 tions, and it has therefore had no regidar series of interior investigations. Kilauea alone is always accessible. Although the crater is so large, the height is no greater than that of Vesuvius. Even when ready for an eruption it is safe to stand on the brink of the great pit and watch the boiling caldrons, and sweeping lava-floods, and violent but harmless blowing-cones. The action of the liquid lavas is ordinarily so quiet and regular that all parts of the great open arena may be traversed with safety ; and the margins of the fiery lakes, if the heat is not too great, may be made a sleeping- place for the night, — with only this possibility, that the lavas may well up and spill over. This spilling over may be the sending away of a stream for a mile or two across the crater's bottom ; but standing a little to one side it does no damage, and the next day the fresh lavas may be walked upon. Thus the crater may be followed in all its interior changes month after month. There is terrible sublimity in the quiet work of the mighty forces, and also something alluring in the free ticket offered to all comers. The records of such a region, whoever the reporter, are of great importance to science ; and where descriptions are seemingly overdrawn it is easy after a little experience to select the facts. Publications relating to the Hawaiian Volcanoes. — The earliest records of Hawaiian lavas and of the crater of Kilauea are contained in the "Journal of a Tour around Hawaii [in August, 1823] by a Deputation from the Mission of the Sandwich Islands," 264 pp. 8vo, with six plates, wdiich was published at Boston, in 1825, by Crocker & Brewster. The statement is made that it was " drawn up by the Rev. William Ellis," of England, one of the party, " from min- utes kept by himself and by his associates on the tour, who subsequently gave it their approbation." It contains, facing page 136, a night view of " the south end of Kilauea," from 36 VOLCANIC PHENOMENA. a sketch taken by Mr. Ellis, looking soutliwestward, en- graved by Mr. S. S. Jocelyn, an artist of New Haven, Conn. The position from which the sketch was taken is indicated in the following words. " Leaving the north end of the crater," says the ^'Journal" (p. 145), ''we passed along to the east side, where Mr. Ellis took a sketch of the southwest end of the crater." In the next sentence it is added : '^ As we trav- elled from this spot we unexpectedly came to another crater," nearly half as large as the former. The native name of it is Kirauea-iti (Kilauea-Iki, as now written) ; ''it is separated from the large crater by an isthmus nearly one hundred yards wide." The position from which the view was taken was hence north of Byron's hut (p. 51), either on the isthmus referred to or farther north on the bluff adjacent. A notice of the "Journal," with citations, is contained in the "Mis- sionary Herald," 1828, xxii. 28. In 1826 a London edition of the work, " with large addi- tions," was issued by Mr. Ellis, under the title " Narrative of a Tour through Hawaii ; " and a third edition, of 480 pages, was issued in March, 1827. The "Narrative" contains, facing page 226, a day view of the "southwest end" of Kilauea, engraved in England from the same sketch that was used by the American engraver ; f(jr the remark a1)out the spot from which it was taken is repeated on page 247. The view, for some unexplained reason, is made to differ widely from the earlier ; for a large cone stands where was the foot of a lava-stream descending the west wall, and, besides this, two of the cones in the bottom of the crater are omitted, and' the active cones in the crater emit vapors quietly. These two views are presented, half size, on pages 46, 47. Mr. Ellis reproduced his descriptions and his view of the crater in the second edition of his " Polynesian Researches," which was published in four volumes duodecimo in London in 1831. The earlier edition of the "Researches." of two volumes only, contained nothing about Hawaii. In prepar- THE ISLAND OF HAWAII. 37 ing the work for the second edition, the •' Narrative " was added as the fourth volume ; and, for a frontispiece to this volume, a new engraving of Kilauea (from a painting, a night view) was introduced, having the subscript. '' The Vol- cano of Kilauea in Hawaii. Sketched by W. Ellis. Painted by E. Howard, Jr. . . . London, 1831." An outline copy of this view is introduced beyond, on page 50. It differs widely from those of 1825 and 1826 ; and since the state- ment of the ''• Narrative " as to where tlie sketch was taken is again repeated, the source of the differences has no ex- planation in the work. The cones are fewer, but they are as active ; and one, placed out in the front, is a grand high- shooter, far outdoing any of those on the other plates. Further, the features of the black ledge and the wall above are changed on both sides of the pit. and the Great South Lake is put in a southeast recess instead of to the southwest. Mr. Ellis was a second time at Kilauea, but this was before 1826. He then found the crater much more quiet, and " the fires in the south and west burning but feebly." The next pul^lication containing details on the Hawaiian volcanoes is the Rev. C. S. Stewart's " Journal of a Voyage to the Pacific Ocean and Residence at the Sandwich Islands during the Years 1822-1825," published in New York in 1828. It contains an account of a visit to Kilauea, which was made on the 2d of July, 1825. A citation from the account is contained in the ^'American Journal of Science," 1826, xi. 363. Mr. Stewart was again at the Islands in 1829, and in 1831 published in New York his " Visit to the South Seas," in two volumes, duodecimo. It is noticed in the '• x\merican Journal of Science," 1831, xx. 229. In the years 1824, 1825, H. M. S. -'Blonde," under the Right Hon. Lord BrROisr, as commander, visited the islands ; and at London, in 1826, appeared his '' Voyage of the * Blonde' to the Sandwich Islands," in a quarto of 260 pages, with several plates. The visit to Kilauea was made on 38 VOLCANIC PHENOMENA. June 28, 29 (29, 30, American time). It is illustrated by a folded plate presenting a view of the volcano, by R. Dampier, in which the many cones give out vapors quietly, and also a map of the crater by Lieutenant Malden, R. N. (See p. 51.) Between 1825 and 1841 appeared in the -'American Jour- nal of Science," the '• Missionar}' Herald," and elsewhere, let- ters or papers by Rev. Joseph Goodpjch, dated 1825, 1828, 1832 ; by Rev. A. Bishop, letter of 1826 ; by Rev. L. Cham- berlain, 1824 ; by Messrs. Chase and Parker, prepared by E. G. Kellet, 1838 ; by Capt. John Shepherd, R. N., 1839 ; and by Rev. Titus Coan, 1840. Besides these, there appeared in 1836, in the "Compan- ion of the Botanical Magazine," ii. 79-182, a memoir of David Douglas, by Dr. W. J. Hooker, with a portrait, letters, and journal. Mr. Douglas spent a dozen years in travels over North America, visiting Oregon, California, Hud- son's Bay region, etc., as an exploring naturalist, and twice visited the Sandwich Islands, making collections and obser- vations in botany, zoology, etc., part of the time under the auspices of the Horticultural Society of London. His instru- ments included a barometer, chronometers, a reflecting-circle, large dipping-needle, etc. He made his visit to Kilauea on Jan. 23-25, 1834, and that to the top of Mount Loa on the 29th of the same month. The account of the latter journey is contained in his journal on page 175 of the above-men- tioned memoir, and in a letter to Dr. Hooker on page 158. Besides, there is an important letter from him to Captain Sabine, dated Oahu, May 3, 1834, taken partly from his journal, but containing additional material on his barometric, hygrometric, thermometric, and hypsometric observations, published in the " Journal of the Royal Geographical So- ciety," 1834, iv. 333-334. Extracts from the journal of Mr. Douglas are contained in the " Magazine of Zoology and Botany," 1837, i. 582, which includes the letter to Dr. Hooker describino; Mount Loa. While on an excursion THE ISLAND OF HAWAII. 39 over Hawaii in Jul}", 1834, Mr. Douglas, then thirty-live years old, fell into a pit n^acle to entrap wild cattle and was gored to death. In the year 1838 Count Strzeleoki visited Kilauea ; and in his ''New South Wales and Van Diemen's Land," published in London in 1845, he has an account of his observations cited, in quotation marks, from his " manuscript notes." The " Hawaiian Spectator," i. 436, contains a note from him on tlie subject, with a different statement of the facts. (See p. 61.) The author's first observations on the Hawaiian Islands were made in the months of October and November of 1840, and during ten days in November of 1841, while connected with the Wilkes Explcring Expedition around the world, and they are reported upon in his " Expedition Geological Re- port," published by the Government in 1849.^ They occupy pages 155-284 and 353-456, where they are illustrated by a colored geological map of Oaliu and many figures in the text. The islands studied were Oahu, Kauai, and Hawaii, — the last as far as could be done in the commander's allotted week. A second visit was made in August and part of September, 1887, when further observations were made on Hawaii and Oahu, and the volcanic mountains of Maui were for the first time visited.^ Capt. Charles Wilkes also has a report on the Hawaiian volcanoes in Volume IV. of his *' Narrative of the Exploring Expedition," published in 1845, in five volumes, royal octavo. The account given is partl}^ his own and partly that of his officers, including the excellent and faithful artist of the ex- pedition, Mr. J. Drayton. ^ Geology, 756 pages, 4to, with a folio atlas of twenty-one lithograpliic plates. ^ The facts observed in this second visit are reported upon in the "American Journal of Science," in a " Memoir on the Volcanoes and Volcanic Phenomena of the Hawaiian Islands," published in vols, xxxiii -xxxvii. This memoir is closed by a paper by Prof. E. S. Dana on the petrology of the islands : and its contents are re- produced in this volume. 40 VOLCANIC PHENOMENA After 1849, Rev. Titus Coan" became the chronicler of the Hawaiian volcanoes ; and very much is due him for his laborious excursions, and his many accounts of the volcanic changes in progress and of the great eruptions of Kilauea and Mount Loa. The larger part of his communications on the subject appeared in the volumes of the " American Jour- nal," the last in the year 1882. He also published notes on some of the eruptions in his " Life on Hawaii," 1882. Ac- counts from other observers and also many of Mr. Coan's appeared also in the daily newspapers of Honolulu. Among the most important was a paper by Prof. C. S. Lyman, in the " American Journal of Science " for 1851 (vol. xii.), giving an account of his observations in 1846. Others are mentioned beyond, with references. During the years 1864, 1865, Mr. William T. Brigham made a study of Kilauea and Mount Loa ; and he published the results of his work, with maps and other illustrations, in a memoir of 126 pages, quarto, published in 1868 in the "• Memoirs of the Boston Society of Natural History." His memoir contains also a map of the crater of Kilauea, from a new survey by himself, a history of the Hawaiian erup- tions, and a general review of Hawaiian geology. He has a second paper in the " Memoirs of the Boston Society," i. 564, with a map on page 572, based on his own obser- vation and the descriptions of the eruption of 1868. Mr. Brigham was again at the islands in 1880, and brief notes by him on the visit are published in the " American Jour- nal of Science " for 1887. In 1882 Capt. C. E. Button studied portions of the islands, including especially Hawaii and Maui. His account of his observations, with plates and maps in illustration, to- gether with discussions on points in the science of volcanoes, covers 140 pages in the "Fourth Annual Report of the Direc- tor of the United States Geological Survey, 1882-1883." In 1885 Rev. J. M. Alexander surveyed and mapped the IN THE HISTORY OF KILAUEA. 41 Mount Loa crater ; his paper on the subject is contained in the "American Journal of Science," 1888, voL xxxvi. In 1887, after the eruption of Kilauea in March of 1886, appeared important papers on the condition of the crater later in the year 1886 by Mr. J. S. Emerson and Mr. Frank S. Dodge, assistants in the Government Topographical Sur- vey, and by Prof. L. L. Van Slyke, of Oahu College, in the '' American Journal of Science," 1877, xxxiii. 87. Another work of much v;ilue appeared at Honolulu in 1887 : Part 11. of " The Vestiges of the Molten Globe ; or on the Earth's Surface Features and Volcanic Phenomena." By William Lowtiiian Green. A volume of 337 pages, with a map. Besides the above works and papers there are traditions of a violent eruption of Kilauea in 1789, which were collected and published in 1843 by the Rev. I. Dibble, as stated beyond. A. KILAUEA. 1. Kilauea before 1823. Eruption about the Year 1789. — The account of the erup- tion of 1789, or about that time, was gathered from the natives by the Rev. T. Dibble and published in his "^ History of the Sandwich Islands," at Lahainaluna (Island of Maui), in 1843. It was taken by the author from the lips of those who were part of the company and present in the scene, and is as follows : The army of Keoua, a Hawaiian chief, being pursued by Kamehameha, were at tlie time near Kilauea. For two preceding nights there had been eruptions, with ejections of stones and cinders. " The army of Keoua set out on their way in three different companies. The company in advance had not proceeded far before the ground began to shake and rock beneath their feet, and it became quite im- 6 42 VOLCANIC PHENOMENA possible to stand. Soon a dense cloud of darkness was seen to rise out of the crater, and, almost at the same instant, the thunder began to roar in the heavens and the lightning to flash. It continued to ascend and spread around until the whole region was enveloped, and the light of day was en- tirely excluded. The darkness was the more terrific, being made visible by an awful ghire from streams of red and blue light, variously combined througli the action of the fires of the pit and the flashes of lightning above. Soon followed an immense volume of sand and cinders, which were thrown to a great height, and came down in a destructive shower for many miles around. A few of the forward company were burned to death by the sand, and all of them experienced a suffocating sensation. The rear company, which was nearest the volcano at the time, suffered little injury ; and after the earthquake and shower of sand had passed over, hastened on to greet their comrades ahead on their escape from so im- minent peril. But what was their surprise and consternation to find the centre company a collection of corpses ! Some were lying down, and others were sitting upright, clasping with dying grasp their wives and children, and joining noses (the mode of expressing affection) as in the act of taking leave. So much like life the}'^ looked that at first they sup- posed them merely at rest, and it was not until they had come up to them and handled them that they could detect their mistake." Mr. Dibble adds : " A blast of sulphurous gas, a shower of heated embers, or a volume of heated steam would sulticiently account for this sudden death. Some of the narrators, who saw the corpses, affirm that though in no place deeply burnt, yet they were thoroughly scorched." The " sand and cinders " of this eruption (the latter usually called on the island piimice -^ on account of its extreme light- ness, and first mentioned by Ellis, who says "light as a ^ Pumice is the scoria of a trachytic or some orthoclase-bearing lava, with the vesicles linear. IN THE HISTORY OF KILAUEA. 43 sponge "), are well known to cover an area of '" many miles " to the southwest of the crater ; but the accounts of the re- gion have said nothing about the stones until the publication of Prof. C. H. Hitchcock in "Science" of February, 1887, after his visit to the crater in the summer of 1886. He there reports that, •' standing at Keanakakoi, one sees to the southwest and south a stretch of volcanic sand and debris fully equal in dimensions to Kilauea itself. On examining more closely the material called " gravel ' on the map, it was seen to consist of material ejected from the volcano, and numerous lava-bombs were picked up. Ashes also cover the country to the south and southwest over tlie Kau desert for several miles." The author was over the region here referred to in 1887. In accordance with Mr. Dibble's words " many miles around," the deposits exist through the whole circuit of Kilauea, even the vicinity of the Volcano House ; and the projection of stones preceded that of the light scoria (" pumice "), yet it was itself preceded by a great shower of volcanic ashes or sand. Tlie stones are in great numbers and of large size to the west and northwest of the crater. The deposit has its maximum thickness over a large area south and southwest of the crater, where it is twenty-five to thirty feet thick and extends ten miles or more away. It is well exposed to view along the fissures. The lower twenty to twenty-five feet of the deposit consist of yellowish-brown beds of tufa, the material very fine volcanic sand and hardly consolidated. Above the tufa are two to three feet of a coarse conglomerate consisting chiefly of stones ; and above this stratum, a bed twelve to sixteen inches thick of closely packed brownisii sponge-like scoria (''pumice"), in pieces half an inch across to two or three inches. This sponge-like scoria contains the least possible amount of solid matter, being about ninety-eight and one-third per cent air, the rest glass ; for the small round cells have 44 VOLCANIC PHENOMENA no walls except a few slender threads, and it is as light as a dry sponge. (See p. 163.) On acconnt of its light- ness it is easily carried off by the winds as well as by the sleepiest of waters, and hence the bed is often left in patches. The ejected stones vary in size np to several cubic feet. Those of one to two cubic feet are common, many are twenty to tliirty, and one seen by the author on the west side of Kilauea measured one hundred cubic feet and must have weighed over eight tons. Part are ordinary volcanic scoria ; but the most of them consist of the more solid basalt spar- ingly vesicular ; and many of the larger are of a light gray kind very slightly vesicular or hardly at all so, very sparingly chrysolitic, and frequently having on the worn exterior a faint banded appearance from alternating variations in com- pactness of texture. Another kind varies in color from faintly reddish to gray, is more or less vesicular, and con- tains a large amount of chrysolite. Going from the southwest border northward and approach- ing the highest point on the west side, the Uwekahuna sta-- tion of the survey, the deposit becomes thinner, but retains well its characteristics. North of this station the thickness becomes ten feet and less. At the Volcano House it is six feet or more. It may be seen in front of the house at the first descent, where it includes, at bottom, a bed of pebbles ; upon this, six to eight inches of the spongy scoria ("pumice ") ; then another pebbly layer and some fine tufa. It occurs also just north of the Volcano House garden, and may be found in traces elsewhere about the north border. From the south border of the crater the formation extends around by the east side not only to Keanakakoi, but to the Kilauea-iki depression, thinning northward as on the west side, but having the same characteristics, as observed in the spongy scoria, the great numbers of large stones and the kinds of rock constitutingr them. But the stones, though IN THE HISTORY OF KILAUEA. 45 mail}' and large, are of somewhat less size than to the west and southwest, and the ^'pumice" to the northward on this windward side of the crater is in thin widely scattered patches. The tongue of land extending from that side to- ward the south end of Halema'uina'u, with the words "gravel and Ijowlders " over it on the map, owes its gravel and many bowlders to the same source, as Professor Hitchcock implies. The low plain between Kilauea-iki and Kilauea fails of it ; but this is owing to recent lava-outflows over the surface. The deep soil and earth farther east, over a region crossed by the north and south carriage-road on the route from Keauhou to the crater, bearing tree-ferns in lux- uriance, is probably an eastern portion of the tufa formation. The greatness and violence of the eruption cannot be doubted. The distribution of the ejected stones, ashes, and scoria all around Kilauea seems to show that the whole bot- tom of the pit was in action ; yet the southern, as usual, most intensely so. The heavy compact rock of the stones and the size of many of them indicate that the more deep- seated rocks along the conduit of the volcano were torn off by the violent projectile action. It w^as an explosive erup- tion of Kilauea such as has not been known in more recent times. 2. Kilauea from 1823 to 1841. The recorded history of the crater of Kilauea — " Lua Pele " of the islanders — commences with August, 1823, the time of the visit by the deputation of missionaries mentioned on page 35. A great eruption had taken place in the pre- ceding spring between the months of March and June ; so that the condition was that of the crater emptied and just starting anew in the preparation for the next eruption. The fact as to an eruption but a short time before was inferred by the deputation from the existence of a " black ledge," as 46 VOLCAXIC PHENOMENA it was then called, running like a terrace-plain around the interior some hundreds of feet above the bottom ; " for it was evident," says the •' Journal," '• that the crater had been recently filled with, lavas up to the black ledge/' and that, as Mr. Goodrich states it in his letter of April, 1825,- '"' the black ledge was made by the crater's being filled to that level." Fortunately the deputation had one in their num- ber, Rev. j\Ir. Ellis, to make a sketch of the crater, and show precisely what was to be understood by the description. A reduced copy of the sketch as engraved for the " Journal " is here presented, and it is conclusive as to the evidences of a The South End of Kilauea. recent eruption ; for it has nearly the same features as the sketch by Drayton made a little more than six months after the eruption of 1840. And the resemblance extends not merely to the black ledge and the lower pit, but also to the position of the place of greatest activity in the southwest portion. The time of the eruption is inferred from informa- tion obtained in Kapapala, a few miles to the southwest of Kilauea, that the steaming chasms, fresh ejections of lavas, and a great sunken area fifty feet deep which the deputation passed near Ponahoahoa were made '' two moons " before ^ Goodrich, American Journal of Science, 1826, xi. 2. IN thp: history of kilauea. 47 their visit to the 2)hice, or, as reported to them at Keara- komo, " five moons ; " and they add : '• Perhaps the body of the lava that had filled Kilauea up to the black ledge . . . had been drawn off bv this subterranean channel." ' The resfion is one over which steaming chasms have been made also at later eruptions of Kilauea. Further, Rev. Mr. Bishop was informed by a native, in 1826,^ that ''after rising a little higher the lava would discharge itself toward the sea, as formerly by an underground way," — thus recognizing as a traditional fact what has been fully sustained by later events. The following is a copy of the view of Kilauea inserted in the English reproduction of the "Journal " called the "Nar- rative." In spite of the changes it tells the same story as to the deep lower pit and the black ledge. The Southwest End of Kilauea. All the changes are unfortunate because they tend to dis- credit the descriptions. But it is quite evident that the engraver is accountable for them. Two others, besides those mentioned on page 36, are here alluded to, that the reader may draw no wrong conclusions. The lavas of the floor of ^ Journal of a Tour, etc., yip. 117, 151. 2 Bishop, Mi.ssionaiy Herald, xxiii. 53, after a visit in 1826. 48 VOLCANIC PHENOMENA the crater are represented to be in "' tumultuous whorls," to correspond evidently with an expression in Mr. Ellis's de- scription ; but the engraver was probably not aware that he had made them hundreds of feet in diameter. The distant southwest part of the crater has its intense fires extinguished, and the wall beyond brought forward and made definite, to the loss of the most characteristic feature of Kilauea. There is no reason to doubt that the crater, although so little time had elapsed since the eruption, was in a state of intense activity, and yet not so generally flooded with lavas that descent into it was impossible. The description in the " Journal " says : '' The southwest and northern parts of the crater were one vast flood of liquid fire, in a state of terrific ebullition. . . . Fifty-one craters, of varied form and size, rose like so many conical islands from the surface of the burning lake. Twenty-two constantly emitted columns of gray smoke or pyramids of brilliant flame [lava-jets ?], and many of them at the same time vomited from their ignited mouths streams of florid lava, which rolled in blazing torrents down their black, indented sides into the boiling mass below." In a night scene " the agitated mass of liquid lava, like a flood of metal, raged with tumultuous whirl," and " at frequent intervals shot up, with loudest detonations, spherical masses of fusing lava or bright ignited stones," some of which projected stones are rep- resented in the sketch (p. 46). Descending to the black ledge (p. 144), they '' entered several small craters, . . . bearing marks of very recent fusion, . . . and many which from the top had appeared insignificant as molehills " proved to be " twelve or twenty feet high." ^ They also col- lected the " hair of Pele," and afterwards found some of it seven miles south of the crater, '' where it had been wafted by the winds." Mr. Ellis argues, from the ''conical islands," that the boiling caldron of melted lava '' was comparatively 1 Journal, pp. 131, 136, 144. LN THE HISTORY OF KII.AUEA. 49 shallow," implying that the cones stood on the solid bottom of the lake.^ Tlie " Journal," after describing on page 144 long, covered, tunnel-like chambers occupying the emptied interiors of lava-streams, the upper surface rippled, the roof '• hung with red and brown stalactitic lava," and " the bot- tom one continued glassy stream," — words that picture well the hundreds of such tunnel-like caverns in the lava-streams of the mountain, — says that they followed one such covered way " to the edge of the precipice that bounds the great crater, and looked over the fearful steep down which the fiery cascade had rushed," the fall " several hundred feet." The sketch on page 46, from the '' Journal," represents rudely such a stream descending the ivest wall (like that of 1832, on the opposite side of the crater) ; but it is omitted from the sketch in tlie " Narrative " (see p. 47). It was prob- ably a fact, but was given too great prominence in the view as engraved for the '• Journal." Mr. Goodrich's letter of April, 1825, does not distinguish the events of his hrst four visits. He observes that in Feb- ruary, 1825, he counted twelve places where the lava was red-hot, and three or four where it was '' spouting up lava thirty or forty feet," and mentions the escape of vapors in many places, making ''a tremendous roaring," — thus describing fully without naming true ''blow-holes" and "blowing-cones." On Dec. 22, 1824, a crater opened in the bottom, where the lavas boiled like a fountain, with jets forty to fifty feet high, and flowed off fifty or sixty rods. In order to give completeness to the records a copy of the engraving in Ellis's " Polynesian Researches " is introduced on page 50. A painter has intervened between the sketcher and the engraver ; and the consequence is easily perceived ,by the reader without remark. The black ledge is still a char- ^ Journal, p. 226, ami Narrative, p. 237. 7 50 VOLCANIC PHENOMENA acteristic feature, thougli made very narrow. It is obvious that the high-shooting cone in the foreground, blowing to a height of seven or eight hundred feet (measuring it by the The Volcano of Kilauea. height of the upper wall), is the artist's idea. It is wholly un-Kilauean, and fundamentally out of place. Depth of the Lower Pit and Width of the Black Ledge. — - The depth of the lower pit in August, 1823, was estimated by the deputation at three or four hundred feet, and the total depth of the crater from seven to eight hundred feet, making the former nearly or quite half the latter. Mr. Goodrich, who was at the crater with the deputation in 1823, and also three times afterward before April, 1825, estimated the whole depth at over a thousand feet, and that of the lower pit at five hundred feet. On this point and others we have further testimony from a map and a sketch of the crater, besides descriptions, in Lord Byron's " Voyage of the Blonde." Lord Byron's party was. at Kilauea in the last week of June, 1825, — nearly two years after Mr. Ellis drew his sketch. The map is from a IN THE HISTORY OF KILAUEA. 51 survey by Lieutenant Maiden, R. N. The copy here given, reduced one third, represents a narrow black ledge (5) around the lower pit, with a steep wall between them. The height of this lower wall, or the depth of the lower pit, was estimated by Lieutenant Maiden at four hundred feet ; and by triangulation he obtained nine hundred feet for the height of the upper wall. The calculation of the latter was based on the angle S'' 55', subtended by the highest part of the northwest wall (at 7 on the map) from the Hut on the east side, — ^Lord Byron's place of encampment, — and the distance obtained in his survey of the point 7 from the Hut, namely, 8,209 feet. He states that the result gave 932 feet. But there is some slip in the figures ; for the correct height from the data would be 851 feet. The recent government survey of Kilauea makes the distance across 8^750 feet; and using this number, we get 907 feet for the height of the wall. It is therefore probable that 900 feet was about 52 VOLCANIC PHENOMENA the heiglit of the upper wall, and that the lower pit two years after Ellis's visit had still a depth of 4(J0 feet. The sketch of the crater in Lord Byron's " A^oyage " was by R. Dampier. It makes the frontispiece to the volume. The following is a copy reduced two thirds. It was evi- dently taken from the Hut, on the east side of the crater. KiLAUEA. It shows the lower pit surrounded by a narrow terrace-plain, or black ledge, and the floor with some small cones over its surface, but with the fires chiefly in the southwestern part, — that of Halema'uma'u, — and with the great dome of Mount Loa in the background. Lord Byron's " Voyage " states that *' fifty cones of various height appeared below," at least " one half of these in activity ; " and Mr. R. Dampier's sketch represents such a scene. Lieutenant Maiden's map makes the cones fewer and very broad. His crater No. 5 is prob- ably Halema'uma'u, for the distance from the Hut is right for it; and if so, the part ''concealed by smoke" was of much less extent than was supposed by the party. Rev. C. S. Stewart, the author of a '* Journal of a Voyage to the Pacific and Residence at the Sandwich Islands in 1822 to 1825," was with the party from the " Blonde," and con- firms the statement in the " Voyage "as to the number of *' conical craters " and the position of the chief seat of action in the southwest extremity of the crater. The black ledge is described as covered with tortuous streams of shining lava, IN THE HISTORY OF KILAUEA. 53 bearing " incontestible evidence of once having been the level of the fiery flood ; " and it is added with reference to the lower pit that " a subduction of lava " had " sunk the abyss many hundreds of feet to its present depth." A cone on the bot- tom, visited by the party, spoken of as "• one of the largest, . . . whose laborious action " had attracted attention during; the night (No. 1 on Maiden's map), was judged to be one hundred and fifty feet high, — ""a huge, irregularly shapen, inverted funnel of lava, covered with clefts and orifices, from which bodies of steam escaped with deafening explosions, while pale flames, ashes, stones, and lava were propelled with equal force and noise from its ragged, yawning mouth." The following night crater No. 3 became suddenly eruptive, and a lake of fire (No. 4 ?) perhaps two miles in circumference opened in the more distant part. The black ledge is represented as narrow in all the published sketches, but most so in Maiden's map, and in the view in Ellis's '* Polynesian Researches," which had the benefit of im- provements from a professional artist. As the latter work was published five years after the " A^oyage of the Blonde," it may be queried whether Mr. Howard, the painter, derived any ideas from Dampier's sketch ; but the following facts are rather against this: Mr. Goodrich, in his letter of 1825, who shows careful work in his measurements of the circumference of the crater ivitli a line, remarks that the ledge " is like a stair, although it is half a mile wide some part of the way." ^ By his measurements, in which he was assisted by Mr. Chamberlain.^ lie made the circumference of Kilauea seven and a half miles, which is the length on the recent govern- ment map, and that of the black ledge (going only half-way around and estimating for the rest) five and a half miles, which also was probably very nearly right. * Goodrich, American Journal of Science, 1826, xi. 2. 2 Rev. L. Chamberlain, Ibid., and Missionary Herald, 1826, xxii. 42; Ellis's Polynesian Researches, iv. 253 ; Philosophical Magazine, September, 1826. 54 VOLCANIC PHENOMENA Lord Byron, on his descent into the pit, went from the northeast to the northwest side, and states with regard to the width of tiie ledge — probably the part on the north side, or that passed over — that it varies from four or five feet to upwards of twenty, which supports the evidence from the map and sketch in his "' Voyage ; " and Mr. Stewart says that it was in some places many rods and in others a few feet wide. A direct measurement of the southwest part, toward the sulphur banks, was made in June, 1824, by Rev. E. Loomis, with the result " nearly fifteen rods wide," ^ — which is about two hundred and fifty feet. It will be observed tliat, in the above citations from Mr. Ellis and other early writers on Kilauea, the only heights of ejections of lava mentioned are thirty to forty and fifty feet, and of cones twelve feet, twenty feet, and for "■ one of the largest cones" one hundred and fifty feet, — which are common facts of later time down to the present. The language of descriptions is sometimes strong, but the figures are correct. This close correspondence between the heights and char- acter of ejections given in the earlier accounts and those of recent years is interesting, inasmuch as it proves long-con- tinued uniformity with regard to kind and quality of work, even to the blowholes. The activity was, however, greater and more general than has been witnessed for many years. There are exaggerations, but they are mostly confined to the pictures and to some of the general descriptions. The esti- mates made were usually below the truth, from honest caution. Progress in the Filling of the Loioer Pit. — As early as February, 1825, Mr. Goodrich stated, in view of the over- flows he had observed, and the making of a '' mound " over sixty feet high in six weeks, that the pit had begun to fill ^ Memoir of W. T. Brigham, p. 407. IN THE HISTORY OF KILAUEA. 55 up ; ^ and in his letter of Oct. 25, 1828,^ he made the pit to have diminished in depth since August, 1823, by three or four hundred feet. A year later, Oct. 25, 1829, Mr. Stewart found the lavas, according to his description,^ still two hun- dred feet below the level of the black ledge, — which implies a filling of four hundred feet, if the depth in 1823 was six hundred feet, and of six hundred if eight hundred feet deep. He states that although the crater was comparatively quiet, the bottom was crossed by a chain of lava-lakes, one of them a mile wide, throwing up masses of lava fifteen to twenty feet ; and that there were also six cones in action in the lower pit and one on the black ledo-e. Here again the height of the ejections mentioned is small. In October, 1830, the black ledge was still distinct.^ But in November of 1832 Mr. Goodrich writes that in the preceding July he visited Kilauea, and found evidence that " the crater had been filled up to the black ledge and about fifty feet above it, — about nine hundred feet in the whole," since he first visited it (in 1823). Eriqjtion of 1832. — Mr. Goodrich found at his November visit that an eruption had taken place ; for he continues : " It had now again sunk down to nearly the same depth as at first, leaving as usual a boiling- caldron at the south end. The inside of the crater had entirely changed. ... In Janu- ary preceding — about the 12th as nearly as I can ascertain — the volcano commenced a vigorous system of operations, sending out volumes of smoke ; and the fires so powerfully illumined the smoke that it had the apjoearance of a city enveloped in one general conflagration. A day or two fol- ^ J. Goodrich, letter of April 20, 1825, American Journal of Science, 182(5, xi, 2. 2 Ibid., 1829, xvi. 345. ^ C. S. Stewart, Visit to the South Seas (New York, 1831), including an ac- count of a visit to Kilauea Oct. 9, 1829 ; and American Journal of Science, 1831, XX. 229. * H. Bingham, Residence in the Sandwich Islands, p. 387. 56 VOLCANIC PHENOMENA lowing smart shocks of earthquakes commenced, six or eight a day. . . . The earthquakes rent in twain tlie walls of the crater on the east side from the top to the bottom, producing seams from a few inches to several yards in width, from which the region around was deluged with lava. . . . The chasms " passed '^ within a few yards of where Mr. Stewart, Lord Byron, myself, and others had slept," — the Hut on Maiden's map ; " so that the spot w^liere I have lain quietly many times is entirely overrun with lava." Descending into the crater and going " to the south end, I found myself on the brink of a burning lake, — an opening in the lava sixty to eighty rods long, and twenty or thirty wide, ■ — the whole mass of liquid and semi-liquid lava in which, about twenty feet below the brink, was boiling, foaming, and dashing in billows against the rocky shore. The mass was in motion, runnino; from north to south at the rate of two or three miles an hour, boiling up as a spring at one end and running to the other.'' Depth of the Lower Pit after the Erujotion. — Mr. Goodrich's statements above cited would make the depth of the lower pit after the eruption of 1832 nearly nine hundred feet, and of the crater from top to bottom seventeen hundred and fifty feet. There is no published account furnishing data for cor- recting this estimate. By letter from Mr. W. D. Alexander, Surveyor-General of the Hawaiian Islands, dated March 2, 1887, I learn that his father. Rev. William C. Alexander (who arrived at the Sandwich Islands in 1832) visited the crater Jan. 12, 1833, four months after Mr. Goodrich's visit, and in his private diary gives the depth of the crater as two thousand feet. This tends to confirm Mr. Goodrich's num- bers, although only a rough estimate. He says nothing of any black ledge, except of that at the bottom of the two thousand feet ; and this leads to the inference that the ledge was quite narrow, as in 1823. IN THE HISTORY OF KILAUEA. 57 There is other t'lill evidence from Mr. David Douglas's " Journal " of the existence of a lower pit and black ledge after the spring of 1832, and thereby of the down-plunge, accompanying a discharge of the lavas.^ On Jan. 22, 1834, Mr. Douglas made careful barometric measurements of the crater, all the details of which, with the calculation, are given in his letter to Captain Sabine. He obtamed for the depth to the black ledge, on the highest northwest side, 715 feet, and to the bottom of the lower pit 1,077 feet, as a mean of two calculations. This makes the depth of the lower pit at that date 362 feet, in addition to which he says that there were forty-three feet more to the surface of tlie liquid lavas. We thus know that the down-plunge was a fact ; and we have proof further from the measurements of Mr. Douglas that the lower pit was larger both as to depth and breadth than that of 1840. Hence the eruption of 1832 — instead of being ''a very small one, only remark- able from the fact that the fissure from which it emanated opens at a level of more than four hundred feet above the present lava-lakes," with, " so far as known, ... no sym- pathy . . . within the lavas of Kilauea " — was one of Kilauea's greatest, although not registered, so far as known, in any outside stream of lava. Condition of the Crater ; Filling of the Lower Pit. — Some facts are cited on the preceding page from Mr. Good- rich with regard to the condition of the bottom of the crater after the eruption. Mr. Alexander, while in the crater four months later, found the lake in the southwest end of the lower pit, "the principal furnace, not in lively action," and ascended much disappointed ; but by the time he had reached the summit " the s;rand crater commenced furious action, ^ Memoir of D. Douglas, Companion of the Botanical Magazine, 1830, ii.; and Letter to Captain Sabine, May 3, 1834 (see p. 38). 8 58 VOLCANIC PHENOMENA spouting with a roaring sound streams of melted lava far into the air." The next day he went again to the bottom, and direct to the g;reat boilinsr caldron two and a half miles distant," and found it "• three thousand feet long and one thousand feet wide, tossing its fier}^ surges forty or fifty feet into the air." He went to the brink of the lake, but left it on account of the fumes, and three minutes afterward the spot was covered with the lavas of an overflow, '*■ which," he says, " seemed to pursue us as we hastened away." It is important to observe that uniformly the '' far into the air " and similar expressions in the general descriptions of travel- lers become when put in figures not far from thirty, forty, or fifty feet of actual height. Mr. Douglas, whose visit was in 1834, reports that he found two great boiling lakes in the crater, — a northern, 319 yards in diameter, and a southern, 1190 X 700 yards in area, heart-shaped in form. The great southern lake was " at times calm and level, the numerous fiery-red streaks on its surface alone attesting: its state of ebullition, when ag-ain the red-hot lavas would dart upwards and boil with terrific grandeur, spouting to a height which from the distance at which I stood (on the west wall) I calculated to be from twenty to seventy feet. Close by stood a chimney above forty feet high, which occasionally discharged its steam as if all the steam-engines in the world were concentrated in it," — a good description of a blowing-cone, though the name had not yet been used. There were o'Jier chimneys over the bottom, some active and others comparatively quiet. In each of the large lakes the lavas had an apparent movement southward, the velocity of which Mr. Douglas measured (by throwino; on a block of lava and seeino: how Ions; it took to go one hundred yards), and found it to be nearly three and a quarter miles an hour.^ ' Mr. Douglas's testimony with regard to the Hawaiian volcanoes has been douhted because of bis incredible account of what lie saw at the summit crater in a IN THE HISTORY OF KILAUEA. 59 Thus the filling of the lower pit was again in progress ; and according to information from Mr. S. N. Castle, of Honolulu, the obliteration was nearly complete by the latter part of August, 1837. Mr. Castle reports that he found cones active in all parts of the crater. On May 8, 1838, Kilauea was visited by Captains Chase and Parker, and an account of their observations was written out from their statements by Mr. E. G. Kelley, submitted to them for approval, and afterward published in the " Ameri- can Journal of Science " for 1841,^ with a plate from their sketches, but redrawn, unfortunately, by a New Haven artist who evidently had Vesuvius in his thoughts. An outline copy is here introduced. It was taken at the south end looking northeastward, and has the great South Lake in the foreground. The important fact is registered in it that the black ledge was already nearly buried. There is none on the west or north side ; and to the left, instead of a black ledge, there is a depressed plain, forty feet below the general level ; part of it (AA) was flooded by lavas after having been passed over by the party. The crater was luuisually active ; there were twenty-six volcanic cones, twenty to sixty feet high, eight of them throwing out cinders, red-hot lava, and steam, and six lakes of lava including the Great Lake (C), the last " occupying more space than all the rest." letter to the eminent hotanist, Dr. Hooker. But I find that injustice has been clone Iiim. His " Journal " of his visit to the summit, evidently written by him at the time of his observations, represents the crater us having been long quiet. While at Honolulu, over three months later (May 3j, he wrote Captain Sabine on his various physical investigations and barometric measurements, and gave him the same facts as to the summit crater that he has in his " Journal," and partly in the same words. Only three days later (May 6) he wrote his letter to Dr. Hooker, — a reasonable letter in all parts, excepting its description of the terrific activity and inmiense size of the Mount Loa crater. His words indicate a mixing up and magnify- ing of what he had seen at the Kilauea and summit craters, which can be explained only on the ground of temporary hallncination. He may have dined that day with his friend the British consul. Mr. Douglas was an excellent Scotchman, and all the rest of his writings are beyond questioning. ^ American Journal of Science, 1841. xl. 117 60 VOLCANIC PHENOMENA Not far from the centre of the Great Lake an island (I) of black solid lava " heaved up and down in the liquid mass," and "' rocked like a ship on a stormy sea." This is the first mention of a " floating island." The descending streams at KiLAUEA, from the south end. B are described as streams of sulphur ; but as this is not possible, they were probably lava-streams in part colored yellow. We have still another account for the same year ; it is that of Count Strzelecki, who was at the crater in August or September, and published his notes in his work on " New South Wales and Van Diemen's Land," in 1845. He made some barometric measurements over the region, and deter- mined the height of the north-northeast wall down to the " boiling surface of igneous matter " to be six hundred feet, and makes no mention of a black ledge. He describes six craters with boiling lavas, four of which were only three or four feet high, a fifth forty feet, the sixth one hundred and fifty feet. He states that the first five contained twelve thou- sand square feet each ; while the sixth — which he says is called " Hau-mau-mau " — contained nearly a million. He IN THE HISTORY OF KILAUEA. 61 alludes plainly to tlie ebullition over this great lake in tlie expression " ceaseless impetuosity and fury." He says that " the lava sank and rose in all the lakes simultaneously," which is not always true.^ Still further evidence as to the obliteration of the black ledge is supplied by Capt. John Shepherd, R. N., who visited Kilauea on Sept. 16, 1839. Captain Shepherd de- scended into the crater, and visited several cones and small lakes on his way to the Great Lake. He speaks of the black ledge as " obliterated ; " of cones twenty to thirty feet high; whence issued vapors and lava with loud detonations ; of a lake of lava toward the east side one mile long and half a mile wide within a cone a hundred feet high, from the sum- mit of which he saw the expanse of liquid lava "• in violent ebullition." He also mentions that the lavas had an apparent flow from south to north, and adds, " caused by the escape of elastic fluids, throwing up the spray in many parts thirty to forty feet." ''^ Eruption of 1840. — The eruption of 1840 had no witness from among the foreign residents of the islands. Mr. Coan was absent from Hilo at the time on a mission visit to Oahu. He states in his letter on the event, dated September, 1840,^ 1 Count Strzelecki'.s note in the Huwaiian " Spectator " occurs in the number for October, 1838, which number also states that he was visiting various por- tions of the Pacific in H. B. M. S. "Fly." It differs widely from the report in his own work, in making the area of the largest lake three hundred thou- sand square yards, and those of the smaller " about fifty-seven hundred square yards each." His volume is the later publication, and should set aside the news- paper note. Count Strzelecki in this volume describes the terraces around the Kilauea crater as vast platforms ; makes the height above the sea-level of the north- northeast side of Kilauea, two paces from the edge of the precipice, 4,109 feet above tide-level, and 600 feet above the fires below ; and observes that this is 950 feet below the brim of the ancient crater, the highest point of which he made 5,054 feet, and its circuit twenty-four miles. He thought he saw evidence that this greater crater was formerly brimful of molten lava. If this highest point was, as is prob- able, that now highest on the west side, his observed height would imply a large subsidence. - London Athena;um, Nov. 14, 1840, p. 909. ^ Missionary Herald, xxxvii. 283. 62 VOLCANIC PHENOMENA that " on the testimony of many natives" for a week previ- ous to the eruption, in the latter part of May, the interior of Kilauea was '' one great sea of liquid lavas," and that the ground about Kilauea so trembled from the action below that the islanders avoided the path along the verge of the crater. On his first visit in September, tliree months after the eruption, he found the crater witli a deep lower pit and a terrace-plain or black ledge around the whole interior. Dray- ton's sketch (Plate II.), tiioagli made four months later, represents closely the scene. Mr. Coan gathered facts showing that the eruption began on May 30, made itself apparent at intervals down the eastern slopes of the mountain, finall}^ broke out as a stream twelve miles from the coast, and llovv^ed into the sea just south of Nanawale ; and that the flowing continued for three weeks. There was no earthquake, no shaking of the mountain. At Hilo not the faintest rumbling was heard or felt, and only slight quiverings to the north. A light was seen in the dis- tance ; but there were no inhabitants in the region, and it was supposed to be a jun- gle on fire. The la- vas appeared first in a small pit-crater five miles southeast of Ki- lauea (A, in the ac- companying map, which is a reduced copy of part of a large map in the Atlas of Wilkes's "•Narrative"). The natives stated that the lavas rose to a height of three hundred feet in the crater, and this was confirmed by the scoria within it. Next followed small ejections over the surface near by, where other fis- sures had opened, and simultaneously the lava of the crater IN THE HISTORY OF KILAUEA. 63 sunk and disappeared. Other small openings and ejections occurred near C, m, and ii ; and finally, on June 1, began the large flow that was continuous to the sea, which it reached on June 3, extending the coast-line outward nearly a fourth of a mile, and so heating the waters that for twenty miles the shores were strewn with dead fish. The place of final outflow was twenty-seven miles from Kilauea, and eleven from the sea ; and its height, according to Wilkes, 1,244 feet above tide-level. The flowing lava swept away forests in its course, at times parting and enclosing islets of earth and shrubbery, and at other times undermining and bearing along masses of rock and vegetation on its surface. It plunged into the sea with loud detonations. The burning lava, on meeting the waters, was shivered like melted glass into millions of particles, which were thrown up in clouds that darkened the sky and fell like a storm of hail over the surrounding country. The light " was visible for over a hundred miles at sea, and at the distance of forty miles fine print could be read at midnight." The author was over the region in the following Novem- ber. The stream consisted largely of the smoother lava or pahoehoe, with twisted and ropy surface, as usual ; but there were large areas of aa , m which huge blocks were piled to- gether, and in some places slabs were laid with much regu- larity against one another. Here and there were miniature cones a few yards in height, out of which the lavas had spouted for a while after the stream had flowed on. Many fissures and caverns were sending up hot vapors, and in some the rocks were yet glowing within a few feet of the surface. The islets of forest-trees in the midst of the stream of lava were from one to fifty acres in extent ; and the trees still stood, and were sometimes living. Captain Wilkes describes a copse of bamboo which the lava had divided and sur- rounded ; yet many of the stems were alive, and a part of the 64 VOLCANIC PHENOMENA foliage remained uninjured. Near tlie lower part of the flood the forests were destroyed for a breadth of half a mile on either side, and were loaded with the volcanic sand; but in the upper part Dr. Charles Pickering of the Expedition Scientific Corps (both botanist and zoologist) found the line of dead trees only twenty feet wide. The lava sometimes, as in other eruptions, flowed around stumps of trees ; and as the tree was gradually consumed it left a deep cylindrical hole, either empty or filled with charcoal. Toward the margin of the stream these stump-holes were innumerable ; and in many instances the fallen top lay near by, dead but not burned. Dr. Pickering also states that some epiphytic plants upon these fallen trees had begun again to sprout. The rapidity witli which lava cools is still more remarkably shown in the fact tliat it was found sometimes hanging in stalactites from the branches of trees ; and although so fluid when thrown off from the stream as to clasp the branch, the heat had barely scorched the bark. The lava, as stated by Wilkes, issued from several fissures along its whole course, instead of being an overflow from a single opening. At three spots on the coast, probably over three opened fissures, the sands continued to be thrown up until as many Tufa Hills, Nanawale. rounded or nearly conical elevations were formed, the largest of which was found to be two hundred and fifty feet in height, and the smallest about one hundred and fifty feet. They consist of a finely laminated tufa, like tufa-craters. The above figure shows the appearance of the hills at the time of the author's visit in November of 1840. IN THE iiirsTom' OF kilaup:a. 65 These sand-hills are exaiii})les uf elevations thrown up sncl- denly over fissures of ernption. They consist of a nisty yellow tufa, distinctly and finely laminated. The sea was already encroaching on them in the autumn of 1840, and hrid exposed the regular stratification of the interior, showing.'- a steep inclination of the layers outward. Not a trace of tilt- ing took place in the rocks beneath ; the hills are simple cones of eruption formed of ejected cinders. The sands are said to have been thrown out from the centre of each hill while in progress ; yet there was no cavity at top. As the molten lava met the sea there was a violent explosion, and an ejection of fragments which fell arottnd the centre of eruption ; and owing to the water which ascended and de- scended with them, the structure became laminated. The yellow color of the tufa is owing to the action of the steam and water on the augitic and chrysolitic sands, reducing some part of the iron to a hydrate. The time of origin of the several pit-craters to the soitth- east of Kilauea is not known. One of them, Makaopuhi, has the western half about nine hundred feet in depth, according to Rev. E. P. Baker, and the eastern only half this depth, — the latter level answering apparently to a black ledge or terrace. Form and De'pili of the Crater after the Eruption of 1840. — The study of the crater by the Wilkes Exploring Expedi- tion was begun in December, 1840, — more than a month after the author's visit, — and completed in January, after the pendulum experiments had been made at the summit of Mount Loa. The accompanying map is a reduced copy of that published by Captain Wilkes. The scale is five thou- sand feet to the inch. K is for Kamohoalii ; and B the posi- tion of Byron's Hut. It will be observed that it has adjoin- ing it on the east two smaller pit-craters, — Kilauea-iki, or Little Kilauea, and Keanakakoi, — both inactive in 1840, and 9 66 VOLCANIC PHENOMENA of unknown time of origin.^ Wilkes's map makes the wall of the lower pit much too sloping, and the neck between the KILAUEA U. S. EXPL. EXPED 1841 J Encampmciii above the sea 3970 ft. Depth to Black Ledge 650 to bottom 342 main body of the lower pit and the area of the Great Lake, Halema'uma'u, far too narrow. Both are better represented in Drayton's sketch, on Plate II. ; but the latter errs a little 1 The size of these lateral pit-craters is better mapped on Plate ITI. Kilauea- iki, according to Mr. Dodge's recent ineasureiuents, is 3,300 feet from east to west, and 2,800 feet from north to south, and has a depth of 749 feet, or the bottom is 867 feet below the Volcano House datum. Keanakakoi is 1,600 feet long, 1,100 feet wide, and approximately 400 feet deep. Both have nearly vertical walls. The name " Keanakakoi" (or Keana-ka-koi), applied on the Hawaiian govern- ment map to the small crater east of the southern half of Kilauea, signifies, as I was informed by an intelligent native, the " chipping-stone pit," and refers to the fact that formerly a very compact grayish lava Avas obtained at its bottom and used there for the manufacture of stone implements. No such stone or manufacture has ever existed at Kilauea-iki. This appears to settle the question raised by Mr. Brigham as to the correct application of the latter name. The crater has now a bottom of very smooth recent lava, which our guide stated had been ejected eight or ten years back ; its ejection may have occurred, therefore, at the time of the eruption of Kilai;ea in 1879. IN THE HISTORY OF KILAUEA. 67 on the other side, as the walls are too free from debris. (For further remarks on the map see page 135. A dotted line is added in the northeast corner to indicate the pL^.ce of descent.) With regard to the depth of the crater, we iind, as tlie first statement about it in Wilkes's Narrative/ that the " black ledge surrounds it [the crater] at the depth of 660 feet, and thence to the bottom is 384 feet." Four pages beyond, it is added that '' the black ledge is of various widths, from 600 to 2,000 feet." Later in the volume measurements by Lieutenants Henry Eld and Thomas A. Budd are also given. Lieutenant Budd made the depth to the black ledge 650 feet, and thence to the bottom 842 feet, ''whence the total depth 992."^ Again, Lieutenant Eld, it is observed,^ was instructed to make the measurement of the depth, '' as I was desirous of proving my oivn as well as Lieutenant Budd's observations ; " and then follows the remark, '' The measurements coincided within a few feet of each other." Had the precise numbers obtained by Lieu- tenant Eld been reported we might be aljle to remove the doubts left by the varying statements. But the fact that Lieutenant Budd's results are inserted by Captain Wilkes on his own map of the crater is a strong reason for believ- ing that the coincidence was between the results obtained by the two lieutenants. Condition of the Crater at the Time of the Author s Vint in November, 1840. — Although the' crater had been discharged but six months before, the Great South Lake, Halema'uma'u, was ao^ain in full ebullition over its surface, an area of one thousand by fifteen hundred feet, according to measurements by Captain Wilkes. Besides, there were two small boiling lava-lakes. 1 Narrative of the Exploring Expedition, iv. 123. 2 Ibid., p. 175. ' Ibid., p. 179. 68 VOLCANIC PHENOMENA Still, to the spectator on the northern brink of the pit, all was marvellonsly quiet. The lofty walls were horizon- tally stratified, nuich like those of limestone along some river-gorges, and, in tlie view, were as free as the latter from scoria and all else of volcanic aspect. The interior of the crater, an area two and a half miles long, covering nearly four square miles, was a desolate scene of bare rock. Instead of a sea of molten lava '■' I'olling to and fro its fiery surge and flaming billows," the only signs of action were in three spots of a blood-red color which were in feeble but constant aci:itation, like that of a caldron in ebullition. Fiery jets were playing over the surface of the three lakes ; but it was merely quiet boiling, for not a whisper was heard from the depths. Aud in harmony with the stillness of the scene, white vapors rose in fleecy wreaths from the pools and numerous fissures, and collected over the large lava-lake into a broad canopy of clouds not unlike the snowy heaps that lie near the horizon on a clear day, though changing rapidly in shape through constant accessions of cloud material from below. When on the verge of the lower pit, a half-smothered, gurgling sound was all that could be heard. Occasionally a report like musketry came from the depths ; then all was still again, except the stifled nmtterings of the boiling lakes. In a night scene from the summit the large caldron, in place of a bloody glare, now glowed with intense brilliancy, and the surface sparkled all over with shifting points of dazzling light like " a network of lightning " ^ occasioned by the jets in constant play ; at the start of each the white light of the depths breaking through to the surface. A row of small basins on the southeast side of the lake were also jetting out their glowing lavas. The two smaller lakes tossed up their molten rock much like the larger, and ^ A comparison made by my friend Dr. Charles Pickering, a man of very exact observation and measured words. IN THE HISTORY OF KTLAUEA. 69 occasionally there were sudden bursts to a height of forty or fifty feet. The broad canopy of clouds above the pit, and the amphitheatre of rocks around the lower depths were brightly illumined from the boiling lavas, while a lurid red tinged the more distant walls, and threw into varying depths of blackness the many cavernous recesses. The next night streams of lava boiled over from the lake, and formed several glowing lines diverging over the bottom of the crater. Toward morning there was a dense mist, and the whole atmosphere seemed on fire. The lakes were barely distinguished through the haze, by the spangles on the sur- face that were Vjrightening and disappearing with incessant change. Reaching the black ledge we came upon the scene of the recent fires and lava-flows, although the boiling pools were still three hundred and forty feet below. Streams of har- dened lava with their tortuous windings covered its surface, some spreading far and wide and ending in a rolled margin against the base of the outside walls of the crater, and some twisted into ropes or ropy lines, or reaching out in rounded knobs. Others, of less extent, surrounded an oddly shaped cone, a few yards in height, which small worming streams and smaller driblets of lava had raised. These features were testimony to the great lava-floods that spread over the whole crater, even the black ledge, before the eruption of the preceding June. Other reminders were the many dark chasms along the margin of the black ledge, some opening to depths of hundreds of feet, and letting up torrents of hot air or suffocating fumes of sulphur. In several places acres of the ledge were tottering ready to fall ; and twice, while among the chasms, long-continued rumbling sounds broke the silence of the pit, showing that the engulfing or down-plunging of the walls, that began with the dis- charge of June, was still in progress. The great subsidence of nearly four hundred feet at the 70 VOLCANIC PHENOMENA time of the eruption, making the lower pit, generally gave the pit vertical walls, with no slopes except such as were formed of fallen masses of rock. But on the northwest side, the outer part of a great block five hundred yards along the ledge and four hundred yards in mean width, and hence two hundred thousand square yards in area, sank down the four hundred feet so as to make a sloping plane from the top of the ledge to the bottom of the pit. A broad fissure divided the sunken, sloping mass from the black ledge, and other fissures intersected its surface. A descent into the lower pit along any part of the vertical walls was dangerous ; but here it was easy.^ Over the solidified lava-stream,s of the bottom, as well as the black ledge, the tread made the lava crackle, as if it were nothing but the loosest of fragile scoria. The crack- ling was due to a shining, glassy scoriaceous crust, two to four inches thick, that was crushed under the foot, and was easily peeled off from the more solid rock of the lava- stream. Few visitors to the crater find out that there is any other kind of lava in the crater besides this shining and often iridescent crust. It was found to be only the scum of the boiling lava-lakes, — the frothy part, which each stream bore off, like that on a stream from a pot of boiling molasses. Over the eastern of the two small lava-lakes, the first visited, the lava-jets darted to a height of ten or a dozen yards, and fell again into the lake or upon its sides. There was no inconvenience or dantrer in standing; within four or five feet of the edge of the basin. The formation of Pele's hair, or capillary volcanic glass, was going on at the time ; and the spun glass covered tbickly the surface to leeward of the lake, where it lay like mown grass. On watching the ^ It is indicated as the place of descent on the Wilkes map (p. 66). In Dray- ton's view (Plate II.) the line of the sloping plane was coincident with the line of vision, and hence it does not appear. IN THE HISTORY OF KILAUEA. 71 operation a moment it was apparent that it proceeded from the jets of liquid lava thrown up Ij}^ the process of boiling. The winds carried off the spun glass, and laid it down over the surface to leeward, the heavy or loaded end going down first. It apjDeared, at the time, as if the wind carried off small points of the jetted lavas, and thus drew out the glassy hairs ; but others have since shown that the hairs are drawn out when the projected lava, in its ascent, be- comes divided into a succession of clots, the hairs being spun as the pieces pull apart, and that the wind serves only as a transporter. The overflowing of the lava-lake — a common event for the smaller lakes as well as the large — had made a low cone about it, exemplifying the process of overflow or superfluent eruptions characterizing the early period of a volcanic moun- tain. One such cone of great breadth over the centre of the floor, with a large crater at top but then extinct, had a height of about one hundred feet. The lavas of the floor covered caves of various sizes, and the roofs afforded stony stalactites, some of them of ordinary tapering shapes and others of a slender cylindrical form not larger than a quill and partly hollow. A few hundred yards from the eastern lava-lake there stood a singular spire of lava, like a petrified fountain. A column of hardened lava-drops had been raised on a rudely shaped conical base, having a height in all of about forty feet. It had been formed over a small vent, out of which the liquid rock was shot up in driblets and small jets, — making one of the fantastic driblet-cones, as ,-, ,1 1 . n 1 ii Driblet-cone, November, 1840. the author has smce called them, — the result of blowing-hole action. It is an interesting exam- ple of a cone of 90^ on one of 40° to 70°, made out of 72 VOLCANIC PHENOMENA descending lavas, -'but lavas in drops, the drops in succession adhering to one another ; the aperture from which those of the column were thrown out was close by its base. The surface of the Great Lake, at the time of the author's exploration of the bottom, was fifteen or twenty feet below its banks, and the height of the jets appeared to be nearly as many yards. The surface lavas, with the playing jets, had apparently, as reported by Douglas, a flow to the south- westward. It looked as if a great lava-stream came up to the surface for a moment and flowed on ; but it was appar- ent that it was due to the process of ebullition, — the lavas raised in the hotter portions flowing off to the cooler side. One of the most striking sights in the crater was that of the cooled and hollow streams of lava coming down the steep walls just south of the usual place of descent. They were those of the eruption of 1832, which flooded the plain above, including the site of Lord Byron's '' Hut," and which also plunged into the crater, besides escaping from fissures in the wall. The angle of descent of the streams was about 35° ; and yet the streams were continuous. The ejection had been made to a height of four hundred feet at a time when the pit below was under boiling lavas and ready for discharge. Elsewhere about the upper walls, and also about those of the lower pit, no scoria was seen. The surfaces of walls are those of fractures, brought into sight by subsidences ; and the rocks of the layers were as solid as the most solid of lavas. Moreover, no scoria intervened between the beds of lava even in the walls of the lower pit, each new stream having apparently melted the scoria-crust of the layer it flowed over ; and no beds of cinders or volcanic ashes were any- where to be seen in alternation with the beds of lava. While the cooled lava-streams over the bottom were of the smooth- surfaced kind, and would be called pahoehoe, there was the important distinction into streams having the scoria-crust just mentioned, and those having the exterior solid with no sep- IN THE HISTORY OF KILAUEA. 73 arable crust, — facts that pointed to some marked difference in conditions of origin. Condition in Janaaru, 1841. — In January, on the 16th, as observed by Captain Wilkes, one of the small lava-lakes, called Judd's Lake, sent forth a great stream over the bottom of Kilauea, and on the night after the following day, Hale- ma'uma'u, the Great Lake, overflowed. The next morning the lavas had sunk one hundred feet. On the 26th Dr. Pickering found the surface much depressed and in ebulli- tion throughout; yet -"Judd's Lake w\as at the same time overfiowiug its banks." Dr. Pickering concluded, from his observations at this time and in December, that during the intervening month the bottom of " the lower pit had been raised at least fifty feet." The crater had then (as shown on the map, p. 60; two sulphur-bank regions. One was situated on the southeast side of the crater, where the rocks of the wall had been crumbled to an earthy slope in consequence of their decom- position by the hot acid fumes. Fine crystallizations of sulphur were constantly forming through condensations be- neath an outer crust of the earthy surface ; and with the sulphur there was some gypsum, a little alum (alumina sul- phate), some ammonium sulphate, and traces of blue vitriol or copper sulphate, the last indicating the probable presence, in the depths below, of the common copper pyrites or chalcopyrite. Another larger sulphur-bank region — a true solfatara — occupied the eastern part of the broad depressed area at the northeast end of the crater, — an area intersected by many profound chasms emitting hot air and water vapor, and some of them also fumes of sulphurous acid. Incrustations of the blue copper sulphate were obtained also at this place. Toward the margin on this side of the pit large sections of the walls had subsided ; and the way down into the pit was along such sunken blocks and among: the steaming chasms. 74 VOLCANIC PHENOMENA 3. KiLAUEA FROM JANUARY, 1841, TO 1868 INCLUSIVE. The history of Kilauea thus far presented mckides three great eruptions within the seventeen and a half years between the early part of 1823 and the summer of 1840, with inter- vals of eight to nine years. It also indicates that the method of change was, in a general way, alike for each interval, from the emptied state of the pit to that of high-flood level pre- paratory to discharge ; and alike in the down-plunge of the floor consequent on the discharge. Further, the various accounts agree in referring the filling of the pit to outflows of lavas from lava-lakes, cones, and fissures over the bottom of the crater, and in mentioning no facts that point to other concurring means. During the following twenty-eight-year period, from 1840 to 1868, these several subjects received not only contribu- tions of new facts, but the most fundamental of them, on the method of filling the pit, facts enough for a widened and apparently final explanation. Even within the first six years of the twenty-eight the demonstration was made out, though not published until 1851. The only down-plunge of the floor in this period, producing a lower pit, occurred at its close in 1868. (1) Changes in the Crater from 1841 to 1849. — The changes after the year 1840 went forward in the usual quiet way, varying much from time to time, but on the whole with some increase in activity. In July, 1844, according to a letter from Mr. Coan,^ the ^ The letter nf Mr. Coan has not been published entire, and the author is in- debted to his son, Mr. T. Munson Coan, for a copy received in April, LS8S. Some extracts from a letter on the same subject are contained in the author's " Exploration Expedition Report," p. 193. The complete letter, in connection with the observa- tions of Mr. Lyman above reported, enables the author to correct the note about the canals on page 84 of the '' American Journal of Science " for July, 1887. IN THE HISTORY OF KILAUEA. 70 Great Lake, Halema'uma'u, overflowed its margin on all sides, " spreading out into a vast sea of fire, filling the whole southern part of the crater out to the black ledge on either side, and thus obliterating the outlines of the caldron." Moreover, the lavas flowed northward and north- eastward '' in tw^o deep canals five to fifteen rods w^ide, one hundred feet deep, and tw^o miles long," — one by either margin of the lower pit at the base of its walls; and ''the two came within half a mile of meeting under the northern wall of the crater." ^ In one of these canals the liquid lava plunged down a precipice of some fifty feet, forming " a fiery cataract of indescribable grandeur." The facts were also observed by his son, Mr. Titus Munson Coan, and a similar record made at the time. The latter mentions also a small lake in the floor of the pit toward the middle of the west side. A diagram by the Rev. Mr. Coan accompanies the letter. It represents the canals at the base of the wall bound- ing the lower pit, and situ- ated close by the black ledge, on which, as is recorded on tlie map, the two walked at the time around the cra- ter besides also crossing the lower pit. Canals five to fifteen rods or eighty to two hundred and fifty feet wide, could not be ordinary fissures ; and their position along the sides of the lower pit at the foot of the enclosing walls, their depth, the cascade of fifty feet, their great length, the two nearly encircling the lower pit, were at the time without expla- nation. The depth of the lower pit is not stated. 1 Coan, Life in Hawaii, 1882, p 2(13, 76 VOLCANIC PHENOMENA Two years later, in June of 1846, Mr. Coan reported^ that *' the repeated overflowings had elevated the central parts of the crater four or five hundred feet smce 1840, so that some jDoints are now more elevated than the black ledge." Thus, in only six years the lower pit — nearly four hundred feet deep in Jnne of 1840 — had been almost or quite obliterated. It is reasonable to conclude, therefore, that in 1844 two thirds of the original depth had l^een lost ; and hence that when those great canals existed alongside of the black ledge, the lower pit was less than one hundred and forty feet deep, ex- cept alo?ig the ivide canals. The next record gives the key to the mystery about the canals. i In the course of the next month, July of 1846, Rev. Ches- ter S. Lyman (afterward Professor of Mechanics and Physics in the Sheffield Scientific School of Yale University), visited the crater, and found it in the condition reported by Mr. Coan. The account of his investigations, which he published in 1851," states that " the whole interior of the pit had been filled up nearly to a level v/ith the black ledge, and in some places fifty to one hundred feet above it." Moreover, Mr. Lyman proved that the change was not a change of level in the ledge, instead of the centre of the pit, by measuring a base and taking, with a quadrant, the altitude above it of the high western wall, making it six hundred and eighty feet, which agrees very nearly with -the result of Wilkes's measurement. Beyond all this, Mr. Lyman obtained full testimony as to the ivay in ichich the rapid obliteration of the pit had gone forward, and thereby reached an explanation of the so-called 1 Coan, American Journal of Science, 1850, x. 361. 2 American Journal of Science, 1851, 2d series, xii. 75. A letter from Mr. Lyman, dated Sandwich Islands, July, 1846, is referred to on page 193 of the author's " Expedition Geological Report ; " but no facts respecting the crater are there cited except the one that some parts of the centre stand one hundred to one hundred and fifty feet above the black ledge ; the author has no knowledge of what it contained beyond this. IN THE HISTORY OF KILAUEA. 77 canals. He found that while the bottom of the pit was almost level with the '' black ledge," there was upon it, along the inner rnar0, letter of July 18, 1855, and p. 139, letter of Oct. 15, 1855. IN THE HISTORY OF KILAUEA. 83 a few seconds, burst into a fountain of twenty to thirty feet ; and then, falling back, the spot became quiet and the red surface quickly took on its gray filmy covering. Near by, another similar fountain in a few seconds would start into action and go through the same changes. In great cavern-like openings under the northeast wall, there were furious surgings and outt brows of the lavas. The wall of Halema'uma'u was tufted with Pele's hair, which was per- petually being formed from the lava projected into the air. Two islands stood unmelted in the northwest part of the lake. On October 9 the crater was still active, but less intensely so. The dome over Halema'uma'u had fallen in. Mr. Coan's report of March, 1856, mentions several visits to the summit eriqjtion then in progress, but nothing about Kilauea until October of that year, when he speaks of the crater^ as declining in activity for the year past, since the sunnnit eruption began ; '• getting moi'e and more profoundly asleep ; . . . only a little slug^n.sh lava in the great pit of Halema'uma'u, but much escaping vapor." A subterranean discharge took place probably in October, 1855. 1855 to 1864. — In June of 1857 Kilauea was still quiet.^ The lavas of the Great Lake were but five hundred feet across, and one bund red feet below the edge. The alternations from the crusted to the completely molten state took about three ininutes. Through the following year, as during the two preceding, there was little change. In August, 1858, the Great Lake, some five hundred feet in diameter, " boiled and sputtered lazily at the centre of a deep basin which occupied the locality of the old dome. The action alternated between general refrigeration and a breaking up of the whole sur- face with intense ebullition." ^ ^ Coaii, American Journal of Science, 1857, xxiii. 4.35, letter of Oct. 22, 1856. 2 Ibid., 1858, XXV. 136, letter of Sept. 1, 1857. 3 Ibid, 1S59, xxvii. 411, letter of Feb. 3, 1859. 84 VOLCANIC PHENOMENA In 180!^ the condition was but little different. Halema'u- ma'u had a lake at centre "' about six hundred feet in diameter." Within the basin, a fourth of a mile from the border of the lake at its centre, there was a large mound of lava (a blow-hole product), with pinnacles and turrets, some- what cathedral-like.^ In the summer of 1863 ^ activity had not much increased ; at intervals of a few seconds to half a minute, a large fountain broke forth at the middle of the lake, throwing up a rounded crest of lava ten to twelve feet. KILAUEA WM. T. BRIGHAM and smaller portions to a height of twenty to thirty feet, while elsewhere there was a filmy crust through which 1 Coan, American Journal of Science, 1863, xxxv. 29G, letter of Nov. 13, 1862. 2 0. H. Gulick, Ibid., 1864, xxxvii. 416, letter of July 25, 1863. IX THE HISTORY OF KILAUEA. 85 small stones tlirowii in sank ; and then again there was ebullition at various points in the lake, — facts showing that the action was still far from brilliant. In October, I860, Mr. Coan reported new activity in the Great Lake, and through the whole circumference of the crater, with outHows that covered the old black ledge with fresh lavas. But the central plateau, " a distinct table-land," probably five to six hundred feet above the bottom of 1840, remained unchanjj-ed.^ '&" 1864-1866. Ohservations and Map of Me. William T. Beigham. — In 1864 Mr. Brigham visited Hawaii, and began the observations on its volcanoes reported in his memoir. The accompanying reduced copy of the map made by him from his survey in 1865, deserves special attention. The map confirms the statements, made from 1846 onward, as to the obliteration of the lower pit. It shows the southwestern sulphur banks, but much dimin- ished in extent since 184(1 from lava-overflows. Halema'u- ma'u has apparently its old position, or is very near it. There are also, on the map, other lakes of small size ; cones, two or three of which were driblet-cones, of blow-hole origin, and one, e, named the Cathedral, from its half- dozen turrets (here repre- sented from his figure), is the same that Avas seen in 1862 by Mr. Coan. The map shows also two . . The Cathedral . Dkiblet-coxe, 1861. lung pieces (e/, i j) of Ly- man's ridge of loose blocks of '' compact broken lava, . . . concentric." as Mr. Brigham reports, " with the main wall of Kilauea. . . . marking the limits of Dana's black ledge [that is, the black ledge of 1840] ; . . . composed of fragments ^ ("oan, American Journal of Science, 1864, xxxvii. 415, letter of Oct. G, 1SG3. 86 VOLCANIC PHENOMENA of all sizes and shapes, very solid and heavy; and full of small trrains of olivine." A recent letter from Mr. Brigham informs the Avriter that the ridge ij (which is not particularly mentioned in the re- port) had the same constitution as ef, but consisted of larger blocks. Other interesting features, indicated on the map, are (1) a wall, a b, — fault-wall, — enclosing an amphitheatre, that of the Halema'uma'u region, perhaps a result of the undermin- ino; occasioned bv a discharge of the lavas of the lake at some unrecorded time; (2) just north of this, a deep fissure, c d, concentric with the wall a h ; and (3) warm or hot steaming caverns in the floor of the crater, some of which were hung with gray-black, often tubular, stalactites.^ The text states that in 1864 the "' black ledge " region was fifty feet below the level of the interior plain of the crater, and that the difference in level was the same in May, 1866, althouo-h both had been much raised, — " at least a hundred feet," — the former by overflows and the latter without overflows. Mr. Brigham does not allude to Mr. Lyman's explanation of the long ridge of lava-blocks. He remarks as follows on page 421, after stating the constitution of the ridge, as already cited : " This wall, which is concentric with the main wall of Kilauea, is said to rise and fall and sometimes disappear, — which seems to be a fact, although no one has ever seen it in motion. It is [made up of] the fragments broken from the edge of the crater by an eruption, and floated out to its [the wall's] present position." Again (p. 415): "From a manuscript map prepared by Mr. Lyman, I find the ridge occupied the same position as at present." Again, in his account of the crater in May, 1866 (p. 427): "The ledge of broken lava which swept aroimd the eastern end of the ^ The stalactites are described on a fullowing page. The temiierature of the caves wasusuanv80°-95° F. IN THE HISTORY OF KILAUEA. 87 crater, marking the limits of Dana's black ledge, is nearly covered with the successive overflows." The Great Lake had a diameter of about eight hundred feet in 1864, and of one thousand in August, 1865. Its lavas in 1864 were fifty feet below the edge, and extended into cav- erns beneath it. The action was mostly feeble : " occasion- all}' a crack opened, and violent ebullition commenced at several points ; " again it was liquid, but soon passed to the viscid condition ; again " boiling violently, and dashing against the sides, throwing the red-hot spray high over the banks." There were two small islands in the lake in 1864 ; but in August, 1865, they had disappeared, and the lavas were then only thirty feet below the edge. The following view is copied from a photograph of a paint- ing by Mr. Perry, a California artist, which I received from Mr. W. T. Bridiam in March, 1865 : — ,~^,',:;„:> ,j—' S'Tt.V-'* iCETS. KiLAUEA IN 1864. Its close correctness is sustained by comparison of the out- lines of Kilauea with those of Drayton's sketch. It has great interest because it gives the position and general appearance of Lyman's ridge of lava-blocks, corresponding well with the 88 VOLCANIC PHENOMENA same in Mr. Brigbam's map. The point from which the view was taken was apparently a little to the east of that selected by Drayton, and hence the differences in the western wall and some other points. The existence of flames over the large boiling lake is at- tested to by Mr. Brigham, who says, on page 423, speaking of a midnight view, that " they burst from the surface, and were in tongues or wide sheets a foot long and of a bluish green color, quite distinct from the lava even where white- hot. They played over the whole surface at intervals, and I thought they were more frequent after one of the periodical risings of the surface." In May, June, and July of 1866 ^ there was a great increase of activity in Kilauea, beginning just after the cessation of the summit eruption. In May new lakes of lire and new cones were opened along a curving line extending from the Great Lake northwest to north and northeast, thus again covering the " black ledge " portion of the crater, flooding the surface with lavas for a distance of two miles, and with a breadth in some places of half a mile ; and for days the flood of lavas closed the usual place of entrance to the crater. Large blocks were shaken down from the walls of Kilauea ; and Mr. Brig- ham observes that these blocks were soon removed by the in- tensely active flood at their base, '' showing how pit craters ma}' be enlarged horizontally." In August the force of the eruption seemed to be spent ; but no subterranean outflow is known to have occurred. During all the activity the central plateau of the crater remained undisturbed. Eruption of 1868. — In 1868 a great outbreak and down-plunge took place in Kilauea, almost simultaneously ^ Coan, American Journal of Science, 1867, 2d .series, xliii. 264 ; Brigham's Memoir, p. 427. IX THE HISTOKY OF KILAUEA. 89 with iin eruption from the summit-crater of Mount Loa.^ It was preceded by a succession of heavy earthquakes. — two thousand or more, according to reports, — commencing on the 27th of March and cuhninating on Thursday, tlie 2d of April, when a shock occurred of terrific violence, which was de- structive through the districts of Hilo, Puna, and Kau, north- east, east, south, and southwest of Mount Loa, and was felt far west of the limits of Hawaii. With the occurrence of this great shock, fissures were opened from the south end of Kilauea soutliwestward througli Kapapala, a distance of thir- teen miles, and bending thence southward toward the coast. The position of this line of lissures is shown on the large map of Hawaii published by the Government Survey in 1887 (frontispiece) ; it followed the course of the earlier fissures of 1823. Some lavas were ejected from the openings in Kapa- pala, which were probaljly lavas from Kihiuea. Simultane- ously with the violent shock, a decline began in the fires of Kilauea.^ By night of that same Thursday, the liquid lavas had disappeared from all cones and were confined to the lakes ; by Saturday night, all the lakes were emptied except the Great Lake ; finally, by Sunday night, tlie oth, the Great Lake had lost its lavas, and all was darkness and quiet. Where the lava went to is unknown. A down-plunge of the central part of the floor of the crater took place at the same time, so that again a lower pit ex- isted, as in 1840. Mr. Coan, in describing it, says that the plateau " sagged down " three hundred feet ; and another 1 Dr. William Hillebrand, American Journal, of Science, 1 868, 2tl series, xlvi. p. 115 ; Coan, Ibid., p. 106 ; F. S. Lyman, Ibid, p. 109; H. M. Whitney, Ibid., p. 112 ; Coan, Ibid., 1869, xlvii. 89, letter of Sept. 1, 1868, with a map of southern Hawaii on page 90. Also the same letters in a paper by Mr. "William T. Brigham, in the Memoirs of the Boston Society of Natural History, i. o()4, with a ma[) on page 572. The map was made by Mr. Brigham from liis survey in 1865 and the descriptions of the 1868 eruption. 2 A letter from Rev. E. P. Baker, of April 5, 1888, states, on the authority of Mr. Richardson, that the subsiding of the lavas began immediately after the earth- quake of April 2d. 12 90 VOLCANIC PHENOMENA writer, after a visit to the pit, gives the same depth, and re- marks "just as ice falls wlien the water is drawn from be- neath." The great sunken area had not vertical walls, like that of 1840, but sloping sides, as the term '' sagged " im- plies ; the slope generally thirty to sixty degrees, but at a much less angle on the side toward Halema'uma'u. There was again a black ledge, and it was nearly of its old width, but at a somewhat hig-her level owino; to the overflows. The emptied Great Lake, three thousand feet in diameter at the top, fifteen hundred feet below, and five hundred feet deep, was literally empty ; it showed no light at bottom by day and not much at night. The discharge of lava may have been as great as in 1840, although the lower pit made by the undermining had less extent. Mr. Nordhoff, in his " Northern California, Oregon, and the Sandwich Islands," ^ page 45, says, speaking of this out- break : " Suddenly, one day, the greater part of the lava-floor sank down, or fell down, a deptli of about five hundred feet, to the level where we now walked. The wonderful tale was plain to us [March o, 1873] as we examined the details on the spot. It was as though a top-heavy and dried-out pie- crust had fallen in at the middle, leaving a part of the cir- cumference bent down but clinging at the outside of the dish." Mr. Nordhoff's statement as to the deptli of the lower pit was evidently quoted, and is not independent testimony ; but his comparison suggested by the sight of the place, suf- ficiently intelligible to an American, attests to the reality of the subsidence. Another remarkable fact is stated : that just before the earthquake of the 2d of April, " the lavas of Kilauea burst up vertically and spread over the old deposit of 1832." A fissure opened in the depressed area between Kilauea and Kilauea-iki, which extended on for nearly a hundred yards. 1 Nordhoff, Northern California, etc., New York and also London, 1874. IN THE HISTORY OF KILAUEA. 91 The lava of the outflow was still lustrous, and mostly free from vegetation in the summer of 1887, while that of 1832 was much weathered and mostly under dense vegetation. As has happened in most Hawaiian eruptions, trees were enveloped by the lava-flood. Half-charred trunks J"' " •"'■i\ were standing, in 1887, with a rough (^^^'''*" '^ cylmdrical encasement of lava about £>. . ' •(k the stumps, projecting from two to I^^^^B^:^^--' two and a half feet or more above !~^':t:;5^^SiM^a^A^*^ the level of the solidified stream, as in the figure, showing that when the lava reached the trees on its way down the slope, it had greater height of surface than afterward when the flow had passed by and its final level was attained. On Tuesday, April 7th, five days after the beginning of the Kilauea discharge, the lavas were ejected in great volume at Kahuku in southwestern Hawaii, and flowed to the sea. It was at first a question whether a part of the Kahuku flow might not have come from Kilauea. But the extinction of the summit fires occurred at the same time, and the Kaliuku discharge was in a line with fissures leading toward it from the summit, so that Mokuaweoweo is believed to have been their only source. Tlie conduit of the Kilauea lavas was probably ruptured at the time of the great shock, and lience the discharge. The curving of the Kilauea fissures from Kapapala toward the coast seems to point to a submarine discharge off that part of the island. 4. Kilauea from 1868 to 1890. This period of eighteen years passed without another down-plunge of the floor of the pit. The gradual filling of the new-made lower pit, and the ultimate merging of 02 VOLCANIC PHENOMENA all sloDes at the crater's bottom into those leading; off in all directions from Halema'uma'ii, are the chief events of the period. Mr. Lydgate's map, on the following page, shows an intermediate stage in the progress. Changes from 18G8 to 1879. — After the discharge and consequent exhaustion of 1868, Kilauea was slow in its re- turn to activity. In July of 1860 Mr. Coan found the crater quiet, and the basin of the Great Lake so nearly cooled that he went down into it and measured across its bottom four hundred feet below the rim ; he found it '* five sixths of a mile" wide, and at top more than a mile froni the north to the south side. Down deep fissures within the emptied basin he could see the lavas, fifty to one hundred feet below, still in ebullition.^ Two years later,'-^ in 1871, the Great Lake was full, and successive overflowings had covered deeply the southern end of the crater and sent streams two miles northward, filling the central pit to a depth of fifty feet. In August of 1871 Halema'uma'u was again a deep cavity, hot and full of dense \"apors,^ but before August of 1872 it was full with lavas and often overflowing; into the o;reat basin of 1868. On March 3, 187o, Halema'uma'u, according to Mr. Nord- hoff.* was divided between two lakes, their shorter diameter about five hundred feet ; " the two were separated by a low- lying ledge or peninsula of lava ; each was red, molten, fiery " within. From the '' north bank " the depth of the pit or basin down to the lavas was seen to be about eighty feet, and " the two large lakes appeared to be each nearly circular." In January, 1874, says another observer, the lower pit was still much below the ledge. The surface of the Great Lake ^ Coan, American Journal of Science, 1879, 3d series, ii. 454, letter of August 30, 1871, and xviii. 227. 2 Ibid., 1871, ii. 454. 3 Ibid., 1872, iv. 407, letter of August 27. 1872. * Northern California, Oregon, and the Sandwich Islands, 1874. IN THE HISTORY OF KILAUEA. 93 was thirty-five to forty feet below the edge of the basin, and "possibly" five hundred feet by nearly half a mile in its diameters, but divided almost in two by a low bank of rock. Four months later, on the 4th of June, the cone about the Great Lake had risen much, and the lake was divided through into two oblong lakes, a northern and southern, in the direction of the longer diameter ; it lay below precipitous and partly overhanging walls that were eighty feet high. The action was less intense than in January. There were active cones near by. One hundred yards from the lake, one typical blowing-cone -'of beehive shape," twelve feet high, about forty feet deep within, and having walls two feet thick, was throwing up jets and clots of lava through holes in its 94 VOLCANIC PHENOMENA sides, '"with a deafening or rather stunning roar" and sub- terranean rumblings and detonations.^ In June of 1874 a map of the crater was made by Mr. J. M. Lydgate.'^ It has great interest, since it shows the central depression or pit of 1868 still well defined, and also the subdivision of Halema'uma'u, above alluded to. Early in October of 1874, according to Mr. Coan, "• the great central depression of 1868 had been filled up by de- posits about two hundred feet," and the region around the Great South Lake had become a truncated elevation nearly as high as the southern brim of the crater.^ In December, 1874, Mr. J. W. Nichols, of the British Transit of Venus Expedition of 1874, was at Kilauea. A brief note by him contains the following facts : ^ A low cone around Halema'uma'u about seventy feet high ; diameters of the basin one-half and one-quarter of a mile ; within it, four lava-lakes, the largest two hundred yards in length ; in the largest, seven or eight fountains of white-hot lava playing to a height of thirty to forty feet, one of them sometimes stop- ping, and then connnencing in another part of the lake ; the fountains in every case playing around the edges of the lake ; lava of largest lake about fifty feet below the brim ; one of the smaller lakes brimful of lava when in the others the lava-surface was thirty or forty feet below the brim ; in one, a single fountain bursting from a cavern in its side. The summit crater is stated to have been in action about a month before the visit. During the Year 1878 and the early Part of 1879. — In January, 1878, Mr. C. J. Lyons, of the Government Survey 1 Isabella L. Bird, The Hawaiian Archipelago, Louduii, 1875, pp. 55, 253. 2 For this tracing I am indebted to the Surveyor-General, Mr. Alexander, the original being in the archives of the office of the Hawaiian Survey. The precise date was not given on the tracing ; but by letter from Mr. Lydgate, the date is now known to be as given above. ^ Coan, American Journal of Science, 1874, 3d series, viii., letter of Oct. 6, 1874. * Proceedings oi' the Edinburgh Royal Society for 1875-1876, ])p. 113-117. IN THE HISTORY OF KILAUEA. 95 Office, obtained, by means of a theodolite, three hundred and twenty-five feet as the level of the lavas of Halema'uma'u below the datum mark at the Volcano House. The following facts, bearing on the condition of the crater in 1878 and the early part of 1879, were copied by the author in 1887 from the hotel-book of the volcano : — July 20, 1878. " Halema'uma'u in a most active state." — M. P, Robinson. September 20. '• Very active." — J. Mott Smith. November 24. "• Very active ; lava within a foot of top of bank." Jan. 8, 1879. '• South Lake with lava fifty feet below the rim and .boiling like water." — Wm. Gardner. Marcli 19. " Large and bright lake." April 15. " Light wonderful." Eruption of 1879. — The facts from the Volcano House hotel-book and the testimon}- of Mr. Coan and others, were evidence that Kilauea was ready for another eruption. The threatened eruption took place between the 18tli and 21st of April, 1879, — the 21st, according to information reported by Miss C. F. Gordon Cummings, who was at the crater in the autumn of that year.^ Mr. Coan reported, in a letter of June 20, that the Great Lake, which had been running over, and whose rim had been raised till nearly as high as the outer edge of Kilauea, was suddenly emptied by a subterranean outlet and subsided several hundred feet, leaving nothing but " a smoking; basin." ^ But the hotel-book records fix the date : — April 21, 1879. " Bottom dropped out of crater." — Wm. H. Lentz, of Honolulu. April 23. "Found tbe thing extinct." — G. Grceper. April 28. " Almost extinct ; some vapors." — Rev. K. 0. Forbes, of Honolulu. April 29. " No fire at all. . . . Lake quite empty." — J. Day. * Fire Fountains of the Kingdom of Hawaii, 2 vols. 8vo, London, 1883. - Coan, American Journal of Science, 1879, xviii. 227, letter of June 20, 1879. 96 VOLCANIC PHENOMENA After some days, in which there was no evidence of fires except that from escaj)ing vapors and steam, the lava re- appeared. The hotel-book of the Volcano House contains the following proof that in June the great basin had recov- ered activity : — June 24, 1879. " Throwing up jets of lava ; both lakes active ; looks like a fountain of fire from the veranda of the Volcano House." — Wm. H. Lentz. July 2. "All traces of two lakes of July, 1878, obliterated, and instead an enormous single lake, which was quite active ; . . . lava thrown up fifty feet." — Wm. Tregloan, of Honolulu. By May, 1880,^ Halema'uma'u had become a boiling and overflowing lake, pouring its streams into the great central basin of the crater. In July of 1880 Mr. William T. Brigham was again at the crater.^ The floor was found to rise into a " tolerably regu- lar dome " which was " surmounted by four lakes of an average diameter of a thousand feet." The latest of the four, the southeastern, commenced to form May 15 of that year, and its bank was in part nearly on a level with the lavas ; but the others had stratified walls, as is stated and figured, which were in places one hundred feet or more in height, and from their front there were frequent avalanches, owing to the undermining action of the active lavas beneath. These lavas were seen here and there to be white hot in the night view. In the darkness " a large volume of gas " was observed escaping from a cluster of blow-holes in the vicinity of the lakes, " which burned with a bluish-green flame," dif- fering in its continuance from the flames seen before by Mr. Brio-ham, which "seldom lasted lono-er than a few moments." The four lakes replaced old Halema'uma'u. By sighting from two of his monuments left from the 1865 survey, Mr. ^ Coaii, American Joui-nal of Science, 1880, xx. V2, letter dated May 3-C, 1880. 2 Brigham, Ibid., 1887, xxxiv. 19. IN THE HISTORY OF KILAUEA. 97 Brigham obtained evidence that the area of the old lake lay " in the midst of the present four lakes " instead of corre- sponding with either of them. This would make the summit of the dome to be in the Halema'mna'u part of the crater, or its southern portion, as in 1886, the dome having in fact ^' a very eccentric apex." In 1882 Captain Button made his examination of Kilauea. He states that after reaching the floor of the crater he walked over the uneven surface for about a mile and three-quarters, and then came to a rapidly ascending slope, rising about one hundred feet ; and from the top of it looked down on " New Lake," about four hundred and eighty feet long and three hundred feet in width, lying between walls fifteen to twenty feet liigh, situated to the northwest of Halema'uma'u. This lake first appeared, he states, in May, 1881.^ New Lake was much of the time crusted over, showing fires only at the edges. Break-ups, making cracks' over the whole surface, and followed by an engulfing of the number- less fragments until " the whole was one glowing mass of lava," occurred at intervals of forty minutes to two and a quarter hours ; but they were of short duration, and the lavas in the mean time were ^' quite black and still." Now and then a fountain broke out in the middle of the lake and boiled feebly for a few minutes ; then it became quiet, " but only to renew the operation at some other point." The larger and more active lake, Halema'uma'u, half a mile off, was siuTOunded by a cone of loose lava-fragments, the lavas a hundred feet below the top. The lake was to a consider- able extent crusted over ; but there were boiling fountains of liquid lava five to ten feet high (by estimate) in play, changing their positions from one part of the lake to another, one dying out as another started up. Two masses of solid ^ Coan, American Journal of Science, 1883, xxv. 220, letter of Feb. 8, 1883; and United States Geological Report, loc. cit. 13 98 VOLCANIC PHENOMENA lava were seen in the New Lake, looking as if formed in it, whicli in the course of several days shifted their positions, showing that they were floating islands. Eruptio?^ of March, 1886. — The above-described condi- tions continued, though with great variations, until March of 1886. On the 6th of that month both Halema'uma'u and the " New Lake " (see Plate III.), the latter five 3'ears old, were unusually full and active, and mingled their floods in overflows. The next morning, March 7, between two and three o'clock, the lavas disappeared and left both basins empty, — first the shallower New Lake, and then the Great Lake. The cone around the latter, then two hundred feet in height above the boiling surface, fell into the emptied basin, and for days the down-plunge of the walls continued. The eruption was thus a simple running off somewhere of the lavas, and a down-plunge of the undermined region was a consequence. There had been a great increase of activity within and about Halema'uma'u, whicli at last had extended in a subterranean way to the northern borders of the crater. The fissures of the solfatara region on the northern border of Kilauea, west of the Volcano House, sent up hotter air and vapors than usual, foreboding some change. The bath- ing-house of the hotel, fitted up for vapor baths, is in this de- pressed region over one of the fissures. The proprietor of the house, Mr. J. H. Maby, found on the afternoon of the 6 til of March (Saturday), when wishing to take a bath, the vapors at repeated visits too hot for it, and finally gave it up. At half-past nine of that evening a slight earthquake was felt, and at a quarter of ten three others, which made '' thud-like sounds," or " like the fall of a meal-bag on the floor;" at ten the light over Halema'uma'u, before very brilliant, suddenly disappeared, — the erwption had taken place. Through Sunday morning the escape of vapors from the Plate H; The Crater or KI LAI IE A UAyVAU . IN THE HISTORY OF KILAUEA. 99 fissures of the solfatara region near the A^olcano House went on, but it ceased entirely on Tuesday, and tlie stoppage con- tinued through Wednesday and Thursday. Afterward the discharge was gradually resumed. Forty-one earthquakes are reported as having occurred during the night, but none strong enough to shake down furniture in the Volcano House, or crockery from shelves. The shocks have been attributed to the down-plungings of the walls of Halenia'uma'u consequent on the discharge of the lavas ; but the intervening distance, twelve thou- sand feet, is too great for such an effect from the feeble vibrations so caused. Moreover, there was a cause nearer by ; for deep fissures were opened for a mile along the road that goes east from the Volcano House, commencing at a point not far from the house. The fissures were still steam- ing in August, 1887. The forty-one feeble earthquakes felt on the margin of the crater at the Volcano House disturbed no other part of the island, and they were the only semblance of violence at the time of the eruption. There was a down-plunge as in other eruptions, but it was all confined within the area which included Halema'uma'u and the associated New Lake. Where the lavas of the lake went, is the old question again unanswered. Perhaps into souie cavernous subter- ranean region, or perhaps into the sea by an opened fissure. The New Lake had had since 1882 its '' floatino; island." A photograph gives the following view of it in its earlier condition. It looks as if it had been a part of a solidified lava-stream which had been floated off from the sides of the lake or had been buoyed up to the sur- face from the bottom. Its lavas were not much vesiculated ; 100 VOLCANIC PHENOMENA but the air-cells were evidently sufficient to enable it to float. It changed much in form from 1882 to 1886, as photographs indicate, probably from encroachments on it by the fusion of its sides, and also from the additions to it through the throws of liquid lavas over it. At the eruption it was left stranded at the bottom of the emptied "Floating Island" of New Lake, Stranded. lake-basin. This view, exhibiting its condition in August, 1887, is from a photograph. It is not known how much of it was beneath the surface of the lava ; but the reader may perhaps satisfy himself on this point. Aftei' the Eruption of March, 1886, durimj the rest of the Year. — The reports of Mr. J. S. Emerson, Prof. S. S. Van Slyke, and Mr. Dodge give details as to the conditions of the crater within the first eight months after the eruption.^ The first and last were made to the Surveyor-General, Professor Alexander. Mr. Emerson was at the crater seventeen days after the event on March 24, and remained till April 14. He says that in this interval '•' no molten lava was anywhere visible in the entire crater. At certain points of easy access a stick could be lighted by thrusting it down a crack so as to bring 1 American Journal of Science, 1877, xxxiii. 87, 95, 98. IN THE HISTORY OF KILAUEA. 101 it in contact with the red-hot rocks beneath ; but in general there was scarcely a place from which I was prevented access on account of the heat." The total depth below the datum at the Volcano House to the bottom of the basin of Halo- ma' uma'u was found to be nine hundred feet, and below the rim of the basin about five hundred and ninety feet. On the 29th of March he descended into the pit ; only Rev. E. P. Baker had preceded him. The sides were covered, not by small fragments of lava or gravel or scoria, but by great irregular slabs of the smooth-surfaced lava (pahoehoe), six to eight or more feet long, five or six feet wide, and about a foot thick, and mostly so placed as to slope downward, though many were tilted in all directions ; they looked as if ready to slip to the bottom. But at a depth of about three hun- dred and twenty-five feet, or two hundred and seventy- five feet from the bottom, where the diameter was about six hundred feet, this rough flooring of pahoehoe slabs came abruptly to an end, and a nearly circular pit began, which had the form nearly of an inverted cone. A view of the condition is shown in the accompanying map of the Hale- ma' uma'u region by Mr. Emerson. The lower basin had an even, lustreless surface, free from large blocks and notable fissures, and consisted chiefly of coarse gravel or fragments of lava, but at bottom of smooth black pahoehoe, free from debris, and of somewhat triangular shape, with sides of twenty-five feet. From a small fissure issued a faintly bluish vapor. In the upper part of the basin, on the northwest side, about 364 feet above the bottom and 225 feet below the top, there was a continuous jet of steam from an oval aperture of five to ten feet. This continued to increase, and on the 12th of April deposits of sulphur were formed about it. Within the basins of New Lake and Little Beggar there were hillocks of smooth-fissured lava, without debris. The huge hulk of the " Floating Island " lay as in the 102 VOLCANIC PHENOMENA sketch, and on measurement proved to be sixty feet high and fully a hundred feet in length. The walls of the emptied basin of New Lake were for the most part nearly vertical, and were everywhere covered with a black, vitreous enamel. The hottest part of the Halema'uma'u depression was on the southwest side ; and in the same direction, to the south- ^ N ^ \ xN ~A^& bono iM. \v;^ s?r^.;-^^V^''/n'i,ij:.:..^^^^ s^^^^^^SSliilS* IIai.ema'cma'u in April, 1886. west of Kilauea, where there are old fissures of 1868 which are still steaming, there were other fissures which appeared to be of recent origin. Professor Van Slyke reached the crater on the 19th of July, — three months after Mr. Emerson left it. He re- ported great changes in Halema'uma'u ; for liquid lava had again appeared, and besides, the central region of the great basin had been " upheaved." The upheaving will be under- stood from Plate III. Within the basin of Halema'uma'u, _ w "^'ft^lif-itj IN THE HISTORY OF KILAUEA. 105 /rom four hundred to a thousand feet from its precipitous north wall, there was a steep mound or cone of loose blocks of solid lava about a hundred and fifty feet high, dropping to about thirty feet on the northwest side. It occupied the central part of tlie basin, and consequently had a deep and wide depression around it. Already a lava-lake of about five acres existed within this depression ; and besides this Pro- fessor Van Slyke saw active fires under cover beneath the cone. He states : — " Ascending the cone part way, I came to the edge of a deep hole or well, of rather irregular outline, four-sided, perhaps thirty or forty feet wide, and from sixty to seventy -five feet long, and not less than a hundred feet deep. The mouth was surrounded by masses of loose rocks, rendering approach to the edge impossible or very dangerous, except at one point ; from this point I could see the bottom of the well, and that it was covered with hardened fresh pahoehoe. At one side the liquid lava could be seen as it was puffed out of a small hole every few seconds and thrown up a few feet. The puliling noise accompanying the ejection of the lava was quite like that of a rail- way locomotive, though louder. The a])erture through which the lava was thrown out might have been three feet long and two feet wide. Immediately beneath the point where I was standing there seemed to be a constant and tremendous commotion, attended by a peculiar swashing noise, but I could not lean sufficiently far over with safety to see anything. Fumes of sulphur dioxide were coming up in abundance, but being on the windward side I was not greatly annoyed by them." From the southeastern side of Haleraa'uma'u he went again up the sides of the cone : — " This led to a second well or deep hole, where molten lava was visible. This well was nearly round, with a diameter of perhaps twenty or thirty feet, and a depth of about a hundred feet. At one point the edge could be safely approached ; but as it was on the lee- ward side the fumes of sulphur dioxide could be endured only for a few seconds at a time. Like the other well, the sides were perpen- dicular. At the bottom was a cone having an opening at the top perhaps ten feet across ; and inside liquid lava was boiling with intense violence, every few seconds throwing up a jet of lava, the 14 106 VOLCANIC PHENOMENA spray of which came to tlie mouth of the well almost into my face. The drops of lava thrown to the mouth of the well liad cooled enough to become hardened and black when they reached the level on which I was standing. This place was quite noisy, the noise resembling that of violently swashing waters." Besides the deep holes just descril^ed. there was, as has been mentioned, a "lake" of liquid lava. It was situated immediately beneath the west wall of Halema'uma'u at the bottom of the wide depression between this wall and the cone-like hill of loose rocks. It extended to the " Smoke Jet," a distance of four hundred feet approximately. It was possible to get down to the edge of the lake, but very haz- ardous. On the occasion of his first visit, in a view from the north side, the entire surface was hardened and black, the only sign of volcanic activity being little steam-jets here and there. After about an hour some liquid lava burst through the black crust and flowed awa}'. Such little out- bursts were followed by others larger. Two days later there was much pufhng and swashing and some boiling lava. Mr. Dodge was at Kilauea, on survey duty, during the last week of the following September and the first of October. The map (Plate III.) is the result of his work and of the previous survey of Mr. Emerson. It brings out strongly the fact that previous to the eruption of 1886 the floor of the crater had been flooded again and again by the streams from Halema'uma'u, until the whole was covered through- out with the new lavas. The surface sloped away from the lake in all directions, as it had done since 1880, and this was true even to the farthest northeastern walls. These universal fiery floods, making the existing floor, took place during 1885, or the year preceding the eruption. They left the depth at the foot of the northeast wall 482 feet below the Volcano House ; over the centre of the floor 350 to 375 feet, and at the summit of the eccentric cone of the crater, about Halema'uma'u, 320 to 340 feet. There was consequentl}^, as P7- g en Z o o H 5- c« ^ (/J H W « 2 IN THE HISTORY OF KILAUEA. 109 Mr. Dodge remarks, a slope of 163 feet to the northeast wall, 125 feet to the northward, below Kamohoalii, 105 to the middle of the northwest side, below Uwekahuna, and about eighty feet along the short radius to the southeastward. The flow had also encroached upon the south bluffs of Kilauea, and covered the older formation at the head of the bay near Holoholokolea, so that at the extreme south angle in the bluffs a further rise of forty feet, more or less, would cause Kilauea to outflow toward the sea. Mr. Dodge also mapped and measured the debris-cone of Halema'uma'u, which Professor Van Slyke had found already '' upheaved " in Halema'uma'u, and determined the height of some of its summits as given on the map. The cone he found to have a breadth from northeast to south- west, of 1,080 feet, from east to west of 1,100 feet, from north- west to southeast of 930 feet. Consequently, as the width of the Halema'uma'u basin from east to west was 2,300 feet, the depression or trough around the base of the cone was 500 to 700 feet on either side. The highest point in the cone scarcely rose above the level of the margin of the Halema'uma'u basin. The basin around it was becoming gradually filled by small outflows of lavas discharged from vents opened over its floor, especially near the base of the cone, and near the wall, where were many small cones and blowholes. But outside of Halema'uma'u, evidences of much heat were con- fined to three or four places. Further, Mr. Dodge obtained evidence that the floor of the basin with the cone upon it w^as rising bodily ; and his observations made on his arrival and before he left indi- cated that the elevation was going on " at the rate of nearly a foot a day." This he further confirmed by later observations ; and on the 14th of January, 1887, wrote that " it was all rising slowly as though floating on the surface of the new lava-lake;" and that the height gained thereby 110 VOLCANIC PHENOMENA above the sea-level since October was probably two hundred feet. The material of the cone he describes as coarse angular debris, with finer fragments, the same that Mr. Emerson found to be the lining of the basin. The structure of the north end — and the rest was all similar — is well shown in Plate IV., from a photograph taken in January, 1887, look- ing westward. The steaming depression at its base is part of the Halema'uma'u basin. The stratified wall beyond is the west wall of Halema'uma'u ; and that above, also strati- fied, is the west side of Kilauea. Above this faintly in the distance is the dome of Mount Loa, covered with January snows. The interior of the cone was inaccessible on account of the vapors ; but from the flashes of light seen over it at night, Mr. Dodge inferred that there was some action. His native guide said to him, '' Plenty fire." In various places over the exterior, as when seen by Mr. Van Slyke, there were '' openings emitting dense bluish- white vapors under considerable pressure, the mouths of which were coated with deposits of sulphur and at night in some cases glowed with red heat." Plate V. shows the condition in October. The photo- graph, of which it is a copy, was taken on a cloudy day, and hence the structure of the cone is not distinct ; but the steaming apertures are nearly as described by Mr. Van Slyke. The surface in the foregroimd is that of the Halema'uma'u basin on the northeast side ; and the walls beyond are, as be- fore, those of the Halema'uma'u basin and of Kilauea, — the former one hundred to one hundred and fifty feet in height. Plate VI. represents the cone six or seven months later, in the spring of 1887. Progress had been made of a kind that threatened the life of the cone ; for the steaming apertures in its side had become steaming vents of consider- able length, too copious in vapors to admit of approach. 5" 2; - g ^ g IN THE HISTORY OF KILAUEA. 113 Three or four months later, in August, 1887, at the time of the author's visit, the Halema'uma'u cone, as seen from the Volcano House, nearly three miles distant, had the ap- pearance shown in the following figure, the vapors being omitted. Its top was high above the rim of the Halema'u- ma'u basin, owing to the rise which had taken place. The '-■ -I .^-..-.AffllfflMyEfeJH^dV ^:>...'-j^!^ .1 J-i-^: >gZ5am ^ ^^ ^''-:~g^ Cone in Halema'uma'u, August, 1887. cone was found to be literally a debris-cone, not a lava-cone or cinder-cone in any part ; and the debris was like that of fallen walls of lava, not of loose scoria such as might have come from the central vent of a cone. No eruptions of lava or scoria from the central depression had been at any time observed, and there was no evidence visible over the surface that any such ejections had taken place. In the night view from the Volcano House the dense vapors on the east and west sides were lighted from the lavas below, but none over the centre of the cone, where there was apparently only feeble action. In the basin about the cone, the chief boiling lava-lake was on the west side, in full view from the top of the west wall. The lake was about lijO by 175 feet in its diameters. Although mostly crusted over, it showed the red fires in a few long crossing lines (fissures), and in three to five open places, half-way under the overhanging rock of the margin where the lavas were dashing up in spray and splashing noisily, with seemingly the liquidity of water. Now and then the fire-places widened out toward the interior of the lake, breaking up the crust and consuming it by fusion ; yet at no time was there a projection of the lavas in vertical jets in a free-boiling way ; nor was it too hot to stand on the border of the lake if only the face were protected. Al- ia 114 VOLCANIC PHENOMENA though relatively so quiet, the mobility of the brilliant splashing lavas made it an intensely interesting sight. Occasionally the red fissures widened by a fusing of the sides as the crust near by heaved, and the lavas flowed over the surface. It was evident from the cooled streams outside, that now and then more forcible movements take place, followed by outflows over the margin ; when the whole lake is in action. There were no true well-defined jets rising and falling over any part of the surface, like those of 1840, — a condition requiring a little more heat; but the splashing at the margin, also due to the escape of vapor-bubbles, had all the freedom of movement of splashing waves on a sea-coast. The existence of the half-covered caverns along the margin, which the descriptions show to have been the most common feature for a score of years, was owing to the protection from cooling given by the overlying rock. All parts of the basin had been overflowed from fissures or temporary lava-pools. One of the striking features of the cooled lava-streams over the bottom of Kilauea, and also of those outside, over its slopes and over those of Mount Loa, are the series of par- allel curved wrinkles, which give the look of tapestry folds to the surface. They are well shown in the following photograph (Plate VII.), which gives a good general idea of the floor of Kilauea as left by the lava-flooding of 1885. While looking: at the small western lava-lake in Halema'u- ma'u, which has since been named the " Dana Lake," the making of the tapestry-like folds was well exemplified. A stream of lava came out from beneath the wall of the debris- cone and flowed obliquely across the lake, making the folds or wrinkles by its onward movement in the thin crust which surface-cooling had produced ; and the wrinkles were convex down-stream because of the greater velocity at centre. The accompanying figure represents, reduced, a small portion of the stream. The wrinkles also formed over the lake along- .Vt, IN THE HISTORY OF KILAUEA. 117 side of fissures in the softened and nearly melted crust. At one time a lateral shove took place along one of the fissures in the crust of the lake, and the next moment the margin was rolled over into a long fold or wrin- kle, and then, by the more rapid movement of the middle portion, a large part of the fold became twisted into a rope. Thus fold follows fold, and a group or series of rope-like folds results. The tapestry-like folds of the surface of streams are some- times folds simply in the scoria-crust ; but they commonly consist of the more solid lava also, or of that alone in case the scoria-crust is absent. Sometimes, in connection with the making of the long ropes, the crust, where thin, becomes bent upward so as to have a long empty space a foot or two deep beneath the brittle cover. It is a trap for the incautious traveller, but it usually startles without injuring, yet serves to j)oint a paragraph about the dangers of the crater. Over the bottom of the crater there were many bulgings of the lavas into oven-like shapes, having a height of fifteen to twenty feet. Such bulgings are common over all lava- streams, and, as already stated, are often called " billows '* and hummocks, and some of them have twice the height of any seen in Kilauea. They look as if they had been pro- duced by a sudden generation of vapors from some volcanic source beneath or from water or moisture passed over by the flowing stream. In many places evidence was plain that the bulging had taken place after the flow of a lava-stream, though before complete consolidation. This evidence was afforded by the tapestr}^ folds on the bulged surfaces, they being upside down ; that is, the folds were often convex upward instead of down- ward, as in the following figure. The tapestry folds indicate 118 VOLCANIC PHENOMENA the direction of movement ; and when thus npside down, they prove that they had been turned out of their original position. These bulgings or domes are generally more or less cavernous within, and sometimes cover large chambers ; they have usually broken sides with some displaced blocks, as here represented. The breaking up of such domes seemed to be due in part to contraction and want of support through the cavernous condition beneath. Some of those in the crater had evidently been further crushed by the push of a subse- quent lava-flow. The sulphur vapors probably take part in the making of such dome-shaped elevations. And when so, the space below may have the roof covered with a crust and stalactites of glauber salts, or with a thin crust of gypsum, as often met with in Kilauea, the vapors having contributed material for the sulphuric acid, and the labradorite of the lavas, the soda or lime. Throughout the crater the lavas had the thin, fragile, or separable scoria-crust or scum, mentioned on page 70 as characteristic of lavas from the overflow of boiling lakes of 1840. But this crust appeared to be thinner than it was in 1840, — only one to two inches thick instead of two to four, as then reported. And as there was vastly greater freedom in the ebullition in 1840, it may well be that the scum of the boiling vats of that period was much thicker than now. But some of the lava streams have no crust. This results when the lava of an outflow exudes through fissures made in the hardened crust that covers it, or when it comes up through deep fissures, and is not derived from the boiling lakes. IN THE HISTORY OF KILAUEA. 119 Such lava is ordinarily glassy for half an inch or less ex- ternally, but instead of being scoriaceous, the glass is nearly solid and part of the solid lava. The lava flowing beneath the crust of cooled rock had parted with its scum, and that from great depths never had any. The occurrence of msilile flames at night over the liquid or semi-liquid lavas of Halema'uma'u, observed by Mr. Brig- ham and mentioned on pages 88, 96, was one of the inter- esting points confirmed at the time of the author's visit of 1887. They were seen to rise within the area of the lake where heavings and breakings of the lava-crust took place, and not where the fires were most active. The flames were one to three feet in height. They were very pale in color, and slightly greenish rather than bluish. The author does not claim himself to have seen the flames, — the rains of the evening and a cold from a thorough wetting on a long excur- sion having prevented his joining the party. But critical observers were of the number, — as Mr. Emerson of the Gov- ernment Survey, President Merritt of Oahu College, Rev. S. E. Bishop, and others, — and the testimony was unanimous. In September, 1887, a month or so after the author left the volcano, the photograph of the Halema'uma'u cone was taken which is reproduced on Plate VIII. It is essentially the same as the cone of August. The change since the spring of 1887 is apparent in the longitudinal division of the west wall into two, so that the vapors rise east of a western section for nearly the whole length. The great cone was evidently in process of dissolution. By March 8, 1888, the cone had risen so high that the summit was " on a line with the outside walls of the crater beyond it, looking from the Volcano House ; " and the floor of the basin had risen likewise, so as to be but forty or fifty feet below the top, — facts which imply a rise of thirty or forty feet since the middle of August, 1887. Moreover, the 120 VOLCANIC PHENOMENA eastern side of the cone, which appeared to be partly separate in the later photograph (Plate VIII.), -'has slipped down a little and changed considerably in shape." ^ In July, 1888, Mr. F. S. Dodge made a new survey of Halema'uma'u.^ He found the basin near- ly obliterated by the rise of its floor, and only fif- teen to twenty feet above it where highest. The accompanying map and sections 2 to 5 present the chief results (l \,-jJlJ J "^ \ ^^ L__ E . F 1. Map of Halema'uma'u in July, 1888, by Mr. F. S. Dodge, reduced to one fourth. 2 to 5. A B, C D, E F, G H, courses of the sections. 2 to 5. Sections by Mr. Dodge of Halema'uma'u in July, 1888. of his survey. The scale of the map is two thousand feet to the inch, which makes the distance across the basin from east to west (New Lake not included) a little over three thousand feet. The outline of the debris-cone at ^ Mr. J. H. Maby, of the Volcano House, American Journal of Science, 1888, xxxvi. 14. 2 American Journal of Science, 1889, xxxvii. 48. See also a letter from Presi- dent Merritt, Ibiel., p. 52. P- G IN THE HISTORY OF KILAUEA. 123 base is approximately indicated by the dotted line. The numbers give the level, below the Volcano House datum, of three points at the top of the cone as well as of the floor of the basin and of the crater outside. At m, n, o, p, q, r are small discharging cones, ten to twenty feet high. Two of these small cones, m and n, were at such a height, owing to the rising of the floor of the basin, that their lava-streams overflowed the rim of the basin ; and from o the lavas had flowed into New Lake, s and t are the higher summits of the cone, and '' New L." means New Lake. Figs. 2 to 5 are four profile sections by Mr. Dodge (A B, C D, E F, G H) of the basin and its cone. The height in these sections is exaggerated five times ; the scale is made four hundred feet to the inch, and the horizontal two thousand feet ; but in Fig. 2, the profile a b has the true proportions. In 2 and 3, p is the pit within the debris-cone. No attempt to obtain the depth could be made on account of the discharg- ing vapors, e is the edge of the basin of Halema'uma'u ; I, Dana Lake. The projection above the floor of New Lake in Fig. .3 is due to the '' stranded floating island." The time from March, 188G, to July, 1888, a little over two years, was sufficient for the refilling of the deep basin of Halema'uma'u and also of New Lake, and for the renewal of the great outflows over the floor of the crater. This condition continued until May, 1889, when, as I learn from Mr. Baker, there was a subsidence of eighty feet in the floor of Halema'uma'u, which carried down the large central debris-cone, and all else on the floor, and made walls of eighty feet again about the great depression. Dana Lake was between the walls and the cone ; but on July 4 it was as active as usual, and a stream flowed froui it toward the cone. A stream of lava issued in May from a fissure in the floor of Kilauea, some distance from Halema'uma'u ; and this appears to have drawn off the lavas beneath the floor of the basin, and so dropped it down the eighty feet. 124 volcanic action. 5. General Summary, with Conclusions. From the foregoing review of publications on Kilauea, it appears that the knowledge we have about the changes in the crater embraces facts that are fundamental to the science of volcanic action. This will be made more apparent by the Summary and Conclusions which follow. It will be conven- ient to consider, first, the Historical Conclusions, and, sec- ondly, the Dynamical. I. HISTORICAL CONCLUSIONS. 1. Periodicity or not in the Discharges op Kilauea. In the sixty-three years from 1823 to 1886, there appear to have been at least eight discharges of Kilauea. Four of them were of prime magnitude, — those of 1823, 1832, 1840, and 1868, — distinguished by a down-plunge in the floor of the crater, making in each case a lower pit several hundred feet deep. Others, as those of 1849, 1855, 1879, 1886, were minor discharges, discharges simply of the active lakes, with- out any appreciable or noticed sinking of the floor of the crater. The eruption of 1849 may be questioned. Other subterranean discharges may have occurred since 1840, of which no record exists. Even small breaks below might empty Halema'uma'u ; and they often do more or less, as the floor of Kilauea l)etween eruptions rises. The mean length of interval between the first three erup- tions was eight to nine years. The great eruption of 1789, the only one on record before that of 1823, occurred thirty-four years back of 1823, or 4X8^ years ; and the 1868 eruption was 3X9^ years after that of 1840. The above approximate coincidences in interval and multiples of that interval seem to favor some law of progress. But it is not yet proved that they have any significance. The minor eruptions which have been referred to above have intervals PROGRESSIVE CHANGES IN KILAUEA. 125 varying from six to thirteen years. Moreover, looking to the summit crater of Mount Loa for its testimony, we find still greater irregularity, the successive intervals between its six great outflows from IS'iS to 1887 being S^, 4, 3i 9, 12i and 6|- years. Dependence of the Actwitij on Seasons of Rains. — A re- lation to the rains was suggested by Mr. Coan ; and there is some foundation for the opinion in the fact that the times of occurrence of the Kilauea discharges come mostly within the four months, March to June, as shown in the following table : 1823 Marcli? 1849 May. 1879 April 21. 1832 June (Jan.?) 1855 October. 1886 Mardi 6. 1840 May. 1868 April 2. In addition, there was a brightening of the fires around the crater in October of 1863, and again in May and June of 1866 ; whether followed by a discharge of the Great Lake or not is not known. The future study of the crater should have special reference to this supposed meteorological connection. 2. Mean Rate of Elevation op the Floor of the Crater AFTER the Great Eruptions. After the eruption of 1823, between the spring of that year and October of 1829, an interval of 6|- years, the bottom, if the depth was 800 feet as inferred after the measurement of the upper wall by Lieutenant Maiden, rose at a mean annual rate of 138 feet, or, taking the depth at 600 feet, of 93.3 feet. Lieutenant Maiden's 900 feet for the upper wall, sustained after explanation on page 51, may need reduction, on the ground that the present width of the crater is greater than in 1825, owing to falls of the walls ; but it is useless with present knowledge to make any definite correction. Only general results are possible. After the 1832 eruption the lower pit in February of 1834 was 362 feet deep, by the barometric measurement 126 VOLCANIC ACTION. of Mr. Douglas, as explained on page 57 ; and in May of 1838, about 4i years later, it was filled to within forty feet of the top ; whence the mean annual rate of 71|^ feet. After the 1840 eruption, between January, 1841, and the summer of 1846, 5|- years, the 342 feet of depth, found for the lower pit by the Wilkes Expedition, was obliterated, and the floor was raised on an average forty or fifty feet beyond this ; a rise of 400 feet in the 6^ years would give, for the mean annual rate, 72| feet. Subsequent to 1846 the rising of the floor was slower. Between 1846 and 1868, twenty-two years, the rise over the central plateau is estimated at two hundred feet. It is not certain that subsidences in the plateau of greater or less amount did not take place at the eruptions of 1849 and 1855, or at other times. 3. Levels op the Floor after the Eruptions op 1823, 1832, 1840, 1868, and 1886. The measurements of depth already given and the mean annual rate of progress deduced are approximate data for determining the depth of the lower pit as it existed imme- diately after the great eruptions. The depth after the 1823 eruption is considered above. To arrive at the depth after the 1832 eruption, the depth obtained in 1834 by Douglas has to be increased by an allowance for change during the previous year and a half, which, at the rate arrived at above, would give four hun- dred and fifty feet. This is so much less than the estimate of Mr. Goodrich, mentioned on page 56, that it is almost certainly below rather than above the actual fact. For the depth in June, 1840, the Wilkes Expedition measurement (342 feet) should be increased for a preceding interval of seven months, which, at the rate deduced above for the next four years, would make the amount about 385 PROGRESSIVE CHANGES IN KILAUEA. 127 feet. In 1868, according to the two estimates for the lower pit, the depth was about three hundred feet. Mr. Severance, of Hilo, informed me, in August, 1887, that the pit in 1868 was as deep as in 1840. The lower estimate is adopted beyond. In 1880, the lower pit of 1868 had wholly disappeared, and, according to the description of Mr. Brigham (p. 1)6), the bot- tom of the crater had already the form of a low eccentric cone, the surface rising from the foot of the encircling walls to the summit about Halema'uma'u. Tliis has continued to be the form of the bottom, and the Government map gives the present depth. (See Plate III.) The following table contains the above deduced figures for the depth of the lower pit, the height of the highest imrt of the western wall, and the level of the centre of the pit below the top of the western wall. Depth of Lower Pit. Height of Western Wall above Ledge. Hei ght of Western Wall above Centre of Bottom. After eruption of 1823 600 (800?) 900 (?) Maiden 1,500 (1,700?) 18.32 450 (600?) 715 Douglas 1,165 (1,315?) 1840 385 650 Wilkes i 1,030 1868 300 600 (550?) 900 (850?) 1886 500 Gov't Survey 380 These numbers have much instruction in them, notwith- standing all uncertainties. The following diagram based on .too .1000 18S8 1S46 i tz: 1^^^ — y ^00 1832 them represents a transverse section of the crater at the sev- eral levels of the floor and black ledge. The minimum depths for 1823 and 1832 are here accepted, there being in them no probability of exaggeration. The sides of the pit in this section are made vertical ^ The Wilkes Expedition appears to have made the place of encaiiipnicTit tlie datum point. It was just west of the solfatara depression, but the exact position is not precisely known. 128 VOLCANIC ACTION. from 1823 onward, — an error which there are no data for correctmg. The dimmution since 1823 in the height of the western wall above the black ledge is probably due almost wholly to the floodhuj of the black ledge. iVccording to the numbers this diminution was about a hundred and eighty-five feet from 1823 to 1832, sixty-five from 1832 to 1840, and one hundred and sixty feet since 1810. But subsequent to 1840, as Emerson's map shows, the diminution of level along the black ledge or lateral portion of the pit has been much less than over the central, the amount of diminution at centre havino; been at least two hundred feet, and about Hale- ma'uma'u two hundred and fifty to three hundred feet. The bottom of the emptied basin of Halema'uma'u after the eruption of 1886 was nine hundred feet below the Vol- cano House ; and this was fifty to a hundred feet above the liquid lava of the basin in 1840. Tlie relations hetween the amounts discharged in 1823, 1832, 1840, and 1868 could be approximately inferred from the size of the lower pit as determined by the mean breadth of the black ledge, if the width of the crater were the same at all periods. But in addition to other uncertainties we have that arising from sloping walls, — and very sloping on the southeast side. The pit of 1823 should therefore have been narrower at the black-ledge level than that of 1840. Still the width of the ledge in 1823, according to all the observa- tions and maps, was so very narrow compared with that in 1840 that we may feel sure of the far larger amount of the earlier discharge. But the depth of the lower pit was also greater in 1823 ; and this requires an addition of one half to the amount which the area of the lower pit suggests, if not a doubling of it. For an estimation of the discharge of 1832 we are still more uncertain as to the mean width of the ledge. But that the ledo-e was narrow — much like that of 1823 — is most PKOGEESSIVE CHANGES IN KILAUEA. 129 probable. In 1868 the down-plimge. according to the most reliable estimate, was a fourth less than in 1840, the depth of the pit being not over three hundred feet. There are no sufficient data for putting in figures the rela- tive amounts of discharge at the great eruptions. But the general fact of a large diminution in the amounts since the first in 182o is beyond question. It has to be admitted, however, that we can hardly estimate safely the discharge in 1868 from the size of the pit then made, since the thickness of the solid floor of the crater may have prevented as large a collapse in proportion to the discharge. But it did not take place until twenty-eight years had passed after 1840, and this strengthens the evidence as to an apparent decline in the outflows, whatever be true as to the activity. The fol- lowing eighteen years produced only minor eruptions. 4. Progress in Halema'uma'u since the Eruption of March, 1886. In April, 1886, a month after the. eruption, Mr. J. S. Em- erson found the basin 590 feet in depth at middle, and 175 to 200 feet decD over a broad border reg;ion. The condition is represented approximately (from Mr. EmxCrson's measurements) in the profile section A. The cone had already become, by Professor Van Slyke's estimate, a hundred and fifty feet high in the next three months. The sections across the basin through the cone B, C, D, illustrate the progress in the lifting of the cone and the floor of the basin, B l^eing the condition re- ported in Mr. Dodge's survey of the first week of October, — six months after Mr. Emerson's survey, when the highest peak of the cone was only two to five feet above the rim of 17 130 VOLCANIC ACTION. the basin ; C, that approximately at the time of the author's visit in August, 1887 ; and D that of Mr. Dodge's last survey in July, 1888, when the cone was almost wholly emerged. From the levels obtained by Mr. Dodge at his two sur- veys in October, 1886, and July, 1888, and by Mr. Emerson in April, 1888, we have data for determining the rate of change of level. (1) The change in the western rim of Halema'uma'u was nothing; (2) in the summit s, 167.2 feet; in the summit t, 171.4 feet. The time during which this rise of approximately 170 feet took place was about 650 days, giving for the mean daily rate of rise 3.15 inches. The rise was most rapid during the first year, Mr. Dodge making the rate in October, 1886, a foot a day. The small ejections going on over the basin outside of the cone during the two years past, raised to some extent the level of the floor. But whatever the amount it does not affect the calculation, this being based on changes in the level of the summit, which received no additions from ejec- tions or any other source. The conclusion of Mr. Dodge that the cone within Hale- ma'uma'u and the floor of the basin about it had been " floated upward " on the rising lavas a|3pears, therefore, to be the only satisfactory explanation of the change of level. Finally, in May of 1889, an eruption over the floor of Kilauea (or some other way of discharge) dropped the floor of Halema'uma'u, with the cone, eighty feet again, restoring nearly the condition of August, 1887. This is the ordinary way with Halema'uma'u. Its discharges from time to time help in the raising of the Kilauea floor, and in the process its own floor loses in level. 5. Other Points in the Topographic History op the Kilauea Region. Besides the points considered, the chief events in the topo- graphic history since 1823 are (1) avalanches and subsidences PEOGRESSIVE CHANGES IN KILAUEA. 131 along tlie Ixjrder of tlie crater, and (2) overflowings and chano-es of level over the bottom. o Down-falls of the walls and sinkings of the l)orders are reported as having been common during periods of eruption and earthquake ; but direct testimony as to the amount at any time does not exist. Besides the great fissures of the northern border of the crater, near the path of descent, with the subsided belts be- tween, and the many fissures of the solfatara depression just back, others exist farther north and east, to a limiting wall, about forty feet high, which is evidently a fault-wall. This wall is about two thousand feet from Kilauea at the northwest corner, and diverges eastward to about five thousand feet, and then bends around southward so as to embrace Kilauea- iki within the large northern border region of fissures and subsidence. Deep and wide rents extend also along the whole western border of Kilauea, generally two or more together ; and. near the highest station, Uwekahuna, there were six of them, parallel to one another, in August, 1887. South of this station, between it and the southwest angle of the crater, the fissures are continued over a large depressed border, five to fifteen hundred feet wide, lying between a precip- itous ridge — fault-plane — on the west and the crater. North of Uwekahuna the evidences of subsidence visil)le in 1887 were small j but south of it the surface had different terrace-levels, showing great and various sinkings of the sur- face. Almost in front of Uwekahuna, bordering the Kilauea wall, there was a surface, 200 to 208 feet below the level of this station, according to the Government maps, which is plainly, as seen from below, a result of subsidence ; and vari- ous other terrace-levels existed farther south. On the east side of Kilauea also there are fissures parallel to the walls ; and large depressed areas exist between Kilauea and the two adjoining craters. Fissures extend northward to the east of 132 VOLCANIC ACTION. Kilaiiea-iki, as noticed by the Wilkes Expedition in 1840, and new openings there, near the Keauhon road, were reported as opened in March, 1886, at the time of the eruption. The wall on the northeast side of Kilauea near the path of descent, called Waldron's Ledge (after a purser in the Wilkes Expedition), is one of the highest and most stable parts of the walls, being but eleven and a half feet below the level of the Volcano House datum. It is a bare-faced, vertical precipice, showing stratified lavas to the top. Like Uwekahuna, it seems to be an exception to border instability. But it stands on the brink of the most unstable region, — that of the north side. In a. walk along the base of the precipice there was in August, 1887, a freshly uncovered portion of the rock at bottom for a height of two to three inches, showing that a recent sinking adjoining it had taken place, or that one was then in progress. This border-belt of fissures and subsidences, if reckoned as part of the Kilauea iire-region, or region of disturbance, adds five thousand feet to the length of the region, and nearly doubles the width across the northern half. There are long fissures also over the region southwest of the crater, some of which were reported by the Mission Deputation of 1823. It is an interesting and important fact that while the fissures about the northeast end of Kilauea are concentric with the outline of the crater (Kilauea-iki being included with it), those at the south end are nearly all longitudinal, or in the direction of the longer diameter, southwestward. Moreover, as is Avell known, tlie latter extend on for twelve to fifteen miles to the southwest. There are many of them, — more than is shown on any map or recorded in any de- scription ; and some are very deep in places, giving off hot air. steam, and sulphurous acid fumes in great volume. While some of them date from 1868, and others from 1886, still others existed back of all records. The subsidence that PKOGKESSIVE CHANGES IX KILAUEA. 138 has gone on over this southwestern fissured area has not left any satisfactory evidence of its amount. We know only that (as the Government map teaches) the surface is about 280 feet heloiv the level of the Volcano House, and 395 feet below that of the Uwekahuna station. In view of the great numbers of deep fissures about Kilauea and the many fault-planes and sunken areas, the fact of extensive subsidence cannot be doubted. Mr. Bris:- ham has estimated ^ that the crater in 1880 was five per cent larger than it was eighteen years before. The increase in mean diameter on this estimate would be three hundred feet. This estimate appears to be much too large. KILAUEA U. S. EXPL. EXPED. Of the gradual changes over the bottom of the crater pretty full records are given in the preceding pages. For defi- ^ American Journal of Science, 1887, 3d series, xxxiv. 2(). 134 VOLCANIC ACTION. nite information on this point, and especially with regard to changes in general outline, we should naturally look with the greatest confidence to the maps that give the results of personal surveys. We have two such maps, — that made personally by Wilkes in 1841 and that by Brigham in 1865, — besides the recent map by the Hawaiian Government, under Professor Alexander's charge, completed in 1880. The first is here KILAUEA WM. T. BRIGHAM referred personally to Captain Wilkes, because his '' Narra- tive " says : "I measured my base and visited all the stations around in turn." For convenient comparison the reduced copies of Wilkes's and Brigham's maps are here reproduced. For that of the Government Survev, see Plate III. PROGRESSIVE CHANGES IN KILAUEA. 135 In using the maps a difficulty is encountered at the outset in consequence of a discrepancy between the first two of the maps and that of the Government Survey as to the dimensions of the crater. Accepting the latter as right, the scale of each of the others should be diminished about an eighth to bring the three maps into correspondence. The maximum diam- eters in Wilkes's map, using his own scale, are 16,000 and 11,000 feet; while, according to the Government map, they are about 14,000 and 9,800 feet ; and the length of the line from K to B on the former is 10,000 feet, and on the latter 8,500 feet. It is certain that the crater in 1840 was not larger at top than now. Mr. Brigham's map appears to have been carefully made, but for some reason it requires the same correction. This correction makes the scale of Wilkes's map 5,000 feet to the inch, as stated on page 65. Such a discrepancy unavoidably throws doubts over other parts of the maps. But while closer study increases confidence in Mr. Brigham's, tlie result is not so satisfactory with the Wilkes map. The following remarks suppose the scale of the two maps to have been corrected. Wilkes s Mcq) of Kilauea. — The relations of the map made by Captain Wilkes to that of the Government Survey is ex- hibited on Plate IX., the outline of the crater from the former being drawn over the latter where it is prominently divergent. This diverging part of the outline is lettered ABODE; D E shows the outline of the southeast Sulphur Bank of 1840. Besides this, the outline of the black ledge of 1840 is indicated by the line L L L, and its surface by cross-lining. Some important features from Brigham's map also are drawn in and indicated by italic letters. These include small lava- lakes, the outline of Halema'uma'u as given by him, small cones, fissures, etc. Plate IX. shows, in the first place, a general conformity between the eastern wall of the Wilkes and the Government maps, but a far greater width of Sulphur Banks in that of 136 VOLCANIC ACTION. 1840. These Sulphur Banks have become submerged by the lava-flows of later time, as remarked as long ago as 1868 by Mr. Brigham, and thus the floor of the crater has in this part been extended eastward about twenty-five hundred feet. This change there is no reason to doubt. In the second place, there is no conformity between the maps in the southern half of the western wall. On the con- trary, in Wilkes's map, south of the Uwekahuna station, the west wall (A B C, on Plate IX.) is twelve to fifteen hundred feet inside of the position of the existing wall as given on the Government map ; showing, apparently, a very great topographical change on that side of Kilauea since January, 1841, and one of the highest interest, — a change that, if a fact, had been brought about either by subsidence or by over- flowings of lava-streams, and had added nearly ten million square feet to the area of the crater. Looking about for other evidence of this change, and find- ing no allusion to it in Mr. Coan's reports on the crater during the period, and nothing in Mr. Lyman's paper of 1851 or his map of 1846, l3ut, on the contrary, a general con- formity in Lyman's map to that of the recent survey, I was led to question the unavoidable conclusion, although it in- volved a doubt of the Wilkes map. A consequence of the doubt was my sudden determination in the sunnner of 1887 to revisit Hawaii and sustain the conclusions from Wilkes's map if possible ; for they made too large a piece in the his- tory to be left in doubt. Mr. Drayton's sketch (Plate 11.) suggested the method of deciding the question. The conclusion arrived at while on the ground was that Drayton's sketch of 1840 represented sufficiently well the jjresent outline of that part of the crater ; that is, the out- line of the crater of 1887. Consequently, if the west wall in 1840 had essentially the same position as in 1887, Wilkes's map of the southern half of its western wall is twelve to fifteen hundred feet out of the way. PROGRESSIVE CHANGES IN KILAUEA. 137 To make this large correction on Wilkes's map involves some other large changes ; namely, the widening of the black ledge west of Halema'uma'u ; and also a widening of the Halema'uma'u part of the lower pit with the entrance-way to it. Both changes are favored, or rather required, by Drayton's sketch. In Plate IX. the entrance- way referred to has thus been widened (on the ground of Drayton's sketcli chiefly), from Wilkes's eight hundred feet at top of wall to about fifteen hundred feet. The dotted line L'L'L' on the same plate is beUeved to show tlie probable limit of the 1840 blaclv ledg-e alona; the west border of Halema'uma'u.^ So large an error in so small a map excites an uncomfort- able query as to all the rest of its details ; fortunately not, however, as to the depth of the cratei" and its lower pit, since this was obtained by the independent measurements of two of the Expedition officers. Lieutenants Budd and Eld. More- over, the map may be used for some general conclusions. The point from which Drayton's sketch was probably taken is marked Dn on Plate IX. ; this is south of Wilkes's en- campment. It ma}' have been on the higher land just west of this point.^ The sketch has three headlands alons; the west wall. Of these, only the second and third exist as they then were. The first or nearest stood, as the sketch shows, between the Uwekahuna summit and the second of the deep western bays on Wilkes's map of the lower pit, — a spot where great sub- sidence has taken place in the western wall, east or south- east of the Uwekahuna station ; and the sketch appears to ^ Another smaller change is proposed in the eastern outline of the lower pit, near e, suggested by Brighani's map. No attempt is made to give, on the Govern- ment map, Wilkes's outline of the southeast angle of the crater, as the existing features offer no available suggestions. 2 While the sketch bears evidence of being generally faitliful to the facts, the foreground appears to be modified for the artistic purpose of giving distance to the rest. 18 138 VOLCANIC ACTION. he sufficient testimony for the reality of this subsidence and its amount. Looking again at Wilkes's map, on page loo, it is seen that, as already stated, the outer eastern wall has the same position that it has on the Government map, ]:)ut that the western wall of Wilkes is not continuous with the southeastern, Imt is an independent one put in more to the eastward ; and here came the error. The error is so extraordinarily great that we sought, while at the crater, for some extraordinary excuse for it. We concluded (Mr. Merritt and myself) that Captain Wilkes in his visit to '' all the stations around the crater in their turn," on reachiug the high Uwekahuna summit, in- stead of relying on his angles, probably took the shorter way of sketching in the ridges that stood to the southeast and south ; and that he was led by insufficient topographical judgment to throw the wall, together with the parallel ridge outside of it, too far to the eastward. The error, as we saW when there, is an easy one for him to have made. This cramped the map to the southward aljout the Great South Lake ; but the angles taken from other stations were not enough to serve for the needed correction, and the sketching was allowed to control the lines. An important error also exists in Wilkes's determination of the longitude of his encampment near the crater. The Surveyor-General of the Islands, Professor Alexander, in- formed me that the position Wilkes gives Kilauea is eight and a half minutes too far west ; and that the error affects all the southeastern quarter of his map of Hawaii including the position of the coast-line. His longitude of the summit of Mount Loa is correct. Mr. Brighams Map. — Mr. Brigham's map is a register of the facts of 1864-1865, a period just half-way be- tween 1841 and 1887. It indicates unfinished changes in progress within the crater which were commenced in 1840, PROGRESSIVE CHANGES IN KILAUEA. 139 and other conditions that became pronounced only in Liter years. The remnants it represents of Lyman's ridge of lava-biocks — the talus of the lower wall uplifted upon the rising lloor of the lower pit, and the same on Mr. Perry's sketch — have already been referred to. That it may be fully appreciated, the reader is directed again to Mr. Lyman's map al:)Ove, and then to Plate IX., which shows these remaining parts of the long- ridcje drawn, from Mr. Bria;ham's mni), on the recent map of the Government Survey (lettered e f, (j li). The ridges are not put as far from the east wall of tlie crater as on Brigham's map, but are made to accord with the statement of both Lyman and Coan (p. 78) and of Brigham also, that they followed the course of the lower-pit wall of 1840 a little inside of its position, over tlie site of the original talus, — Wilkes's position of the wall being adopted except for a short distance near e. Halema'uma'u, as the dotted line inside of the basin of the Government map shows, was small 140 VOLCANIC ACTION. in 1864-1865, it being only one thousand feet in diameter and but little raised above the level of the liquid lavas. Mr. Brigham's map shows also the positions of active lava- lakes in 1864 or 1865 (lettered i, k, I, m) ; and the interest- ing fact is to be noted, on Plate IX., that two of them, to the northwest (/, k) lie at the edge of the Mack ledge, while /, m are a little back of it, but in a line with ?*, k. The long curving line of deep fissures and fault-plane, already referred to as marking the outline of the Halema'u- ma'u region, is seen on Plate IX., at a h, not to be concen- tric with the Halema'uma'u basin of either Brigham's map or of the recent map, but to that of Halema'uma'u j^lfc^ the New Lake region of 1884 to 1887. Thus in 1865, when Hale- ma'uma'u appeared as a small basin one thousand feet broad (not half its existing breadth), the fissure indicated the pres- ence of deep-seated conditions as to the fires and forces that finally ultimated in its extension over the New Lake area. And the expression of this fact in 1865 was doubled by a second concentric fissure five hundred feet farther north (Plate IX., c d). Further, four of the cones mapped by Brigham in the vicinity of Halema'uma'u in 1865 {p, q, r, s, on Plate IX.) are inside of the existing Halema'uma'u basin ; and one of the others (o) is near the north border, and an- other (/) is close by the east side of New Lake. On Mr. Brigham s map, the position is given of a very large loose block of lava, which is shown at iv, on Plate IX. It lies, as is seen, in the northwest part of the crater, and is over the lower edo:e of v^liat in 1840 was an inclined but even lava-plane to the bottom, that had been made in 1840 by an ()hli([uo down-plunge, carrying the inner side of the great mass down and leaving the other, that against the black ledge, on a level with the ledge, with a broad fissure between. This sloping way from the ledge to the lower floor is men- tioned on page 70, The block probably slid down the slope to its bottom. But in the lifting again of the obliquely PLATE IX with additionii rrom the Uapx of Oipt. Wllkm tud W. T. Brigbtm. ^ ->St^j tli^fla'Jitt, C ■ PROGKESSIVE CHANGES IN KILAUEA. 141 subsided mass, as the Hour was raised and Lyman's ridge was made, this loose block was lifted. The lift along that part of the crater, which was already completed in 1846, consisted in the restoring of the half-engulfed mass with the lava- block on its surface, to its former horizontal position ; and this was the position it had when Mr. Brigham's map and observations were made. It is interesting to note thus how the 1864-1865 condition of Kilauea grew out of that of 1840, and foreshadowed that of 1887. It is worthy of consideration, also, that just as the fault-plane a h is concentric with the Halema'uma'u basin plus New^ Lake, so the far greater Kilauea fault-planes, two thousand to five thousand feet north and northeast of the crater, are concentric, not with Kilauea, but with Kilauea plus Kilauea-iki. II. DYNAMICAL CONCLUSIONS. General Cycle of Movement hi Kilauea. — The history of Kilauea, through all its course since 1823, illustrates the fact that the cycle of movement of the volcano is simply: (1) a rising in level of the liquid lavas and of the bottom of the crater ; (2) a discharge of the accumulated lavas down to some level in the conduit determined by the outbreak ; (3) a down-plunge of more or less of the floor of the region under- mined by the discharge. Then follows another cycle : a rising again, commencing at the level of the lavas left in the con- duit, — that is, the lavas of the lava-column, — which rising continues until the augmenting forces, from one source or another, are sufficient for another outbreak. In 1832 the conditions were ready for a discharge when the lavas had risen until they were within seven or eight hundred feet of the top ; in 1840, when within six hundred and fifty feet ; in 1868, when within five or six hundred ; in 1886, when within three hundred and fifty feet. The greater 142 VOLCANIC ACTION. height of recent time may seem to show that the mountain has become stronger, or better able to resist the augmenting forces. But it also may show a less amount of force at work. In 1823, 1832, and 1840 the down-plunge affected a large part of the whole floor of the crater, which proves not only the vastness of the discharges, but also indicates active lava through as large a part of the whole area preceding the dis- charge, while in 1886 the down- plunge and the active fires in view were confined to Halema'uma'u and its vicinity. It w^as not in earlier time, therefore, the greater weakness of the mountain, but probably the greater power of the volcanic forces. The broad low-angled cone whicli the volcano tends to make, has a great breadth of stratified lavas to withstand rupturing forces. How great may easily be calculated by comparing a cone of 5° to 8° with one of 30°, the latter the average angle of the greater volcanic mountains of western America ; and this suggests important differences in the re- sults of volcanic action independent of those consequent on the possible prevalence of cinder-ejections in the latter. Somehow or other Mount Loa breaks easily — very easily, its quiet methods say — and it seems to be because such rocks, however thick, can offer but feeble resistance to rupturing volcanic agencies. In the discussion beyond of the operations going on and of their causes, I speak (1) of Kilauea as a Basalt-volcano, the basis of its peculiarities ; (2) of the size of the Kilauea con- duit ; (3) of the ordinary work of the volcano. The origin of the eruptions of Kilauea is considered in connection with that of the Mount Loa eruptions. 1. Kilauea a Basalt-volcano. The Mobility of the Lavas. — The phenomena of Kilauea are largely due to the fact that it is a basalt-volcano in its KILAUEA A BASALT- VOLCANO. 143 normal state. By this I mean, first, that the rock-material is doleryte or basalt, and secondly, that the heat is sutlicient for the perfect mobility of the lavas, and therefore for the fullest and freest action of such a volcano. It is essentially perfect mobility, although there is not the fusion of all of its minor ingredients, that is, of its chrysolite and magnetite. This is manifested by the lavas, whether they are in ebulli- tion over the Great Lake, throwing up jets twenty to forty feet high, throughout an area of a million square feet or more, or when only splashing about the liquid rock and dash- ing up spray of lava-drops from areas of a few square yards. There is in both conditions the same free movement, almost like that of water, and suggesting to the observer no thought of viscidity. Of the two conditions just mentioned, the former was that of November, 1840 ; the latter that of August, 1887, and of the larger part of intermediate time. This mobility is dependent largely on the fusibility of the chief constituent minerals of the lava. Trachyte and rhyolyte are the least fusible of igneous rocks, because the constituent feldspar, orthoclase, is the least fusible of the feldspars ; and basalt or doleryte is one of the most fusible, because the feldspar present, labradorite, is of easy fusibility, and it is combined in the rock with the still more fusible augite or pyroxene. The degree of mobility is dependent also on temperature. It is probable that at the temperature of fusion, or better a little above it, all the feldspars, the least and the most fusible, are nearly alike in molnlity. But the lower the degree of fusibility the less likely is the heat to be deficient, or below that required for complete fusion and mobility ; and here comes in the great difference among them as regards lavas and volcanoes. The basalt-volcano has special advantage over all others in this respect, as the copious Mount Loa lava-streams and the 144 VOLCANIC ACTION. immense basaltic outflows of other regions exemplify. In Hawaii the heat required for the existing mobility is no greater than the deep-seated conditions below the mountain can keep supplied, in spite of cooling agencies from cold rocks, subterranean waters, and the air ; it is no greater than it can continue to supply for more than half a century, as tlie records have shown ; and supply freely to the top of a con- duit three thousand to thirty-five hundred feet above the sea-level, and even to the top of another conduit but twenty miles off, rising to a height of thirteen thousand feet above the sea-level. The temperature needed for this mobility, judg- ing from published facts, is between 2000° F. and 2500° F. The fusing temperature of augite and labradorite has not yet been determined. We are certain that a white heat exists in the lava within a few inches of the surface ; for the play of jets in a lava-lake makes a dazzling network of white lightning-like lines over the surface ; and white heat is equiv- alent to about 2400° F. Considering; the heig-ht of Mount Loa and the greatness of its eruptions, and the vastness of basaltic outflows over the globe, we may reasonably assume that the temperature needed for the normal basalt-volcano has long been, and is now, easy of supply by the earth for almost any volcanic region ; and that the difficulty the earth has in supplying the higher heat, for equal mobility in a trachyte or rhyolyte volcano, is the occasion of the semi- lapidified, pasty condition of their outflowing lavas. Even if the higher temperature required for orthoclase lavas were always present quite to the surface in the volcano, the ordinary cooling influences of cold rocks and subterranean waters and air would be sure to bring out, in some degree, on a globe having existing climatal conditions, the character- istics of the several kinds of volcanoes designated. It cannot be affirmed that this higher heat required for the complete fusion of trachyte or rhyolyte is wanting at con- venient depths below ; for it has been manifested in the out- KILAUEA A BASALT-VOLCANO. 145 pouring of vast floods of these rocks through opened fissures, many examples of which over the Great Basin are mentioned in King's "Systematic Geology" of the Fortieth Parallel. But in the volcano, whose work, after an initial outflow, is carried forward by periodical ejections, and requires for long- periods a continued supply of great heat, the more or less granulated or pasty condition of the outflowing orthoclase- bearing lava-streams is the usual one. Consequentlv, wlien a volcano changes its lavas from the less fusible to the more fusible, as sometimes has happened, some change in the features of the volcano should be looked for, except perhaps when the change occurs directly after the initial discharge. Here the question suggests itself whether the temperature existing at depths below may not be one of the conditions that determine whether the discharged lavas shall be of the less fusible or the more fusible kind. But a hasaU-\o\ccii'io also niay fail to have heat enough for perfect fusion, and hence may have partially lapidified or pasty lavas, and thus be made to exhibit some of the char- acteristics of the other kinds of volcanoes. This condition may result from three causes : (1) A decline in the supply of heat of the conduit, as when the partial or complete extinc- tion of the volcano is approaching; (2) When the lava is dis- charged by lateral openings or fissures, in which case the lateral duct of lava may not be large enough to resist com- pletely the cooling agencies about it ; (3) The sudden en- trance of a large body of water into the conduit. The effects from the first of these conditions — declining heat connected with approaching extinction — are strikingly exemplified in two great volcanic mountains of the Hawaiian Islands, Mount Kea on Hawaii, and Haleakala on Maui. Those of the second, in which the ejections are from lateral openings, are abundantly illustrated in the cinder and tufa cones of the islands, and also in widespread cinder or ash 19 146 VOLCANIC ACTION. deposits through the driftmg of the ejected material by the winds. The third, a sudden incursion of waters through an opened fissure, if a possibility, should both lower the temper- ature and produce violent projectile results ; and even Kilauea bears evidence of at least one eruption of great magnitude which was thus catastrophically produced, — that of 1789; for the region bordering the crater on all its sides, and to a distance of ten or fifteen miles to the southwest, is covered with the ejected stones or bowlders, scoria, and ashes of such an eruption. Besides the influence of degree of fusibility of the lavas on the features and action of volcanoes, there is also some effect from their specific gravity, which varies much with the vari- ations in the amount present of either of the iron-bearing minerals augite, hornblende, chrysolite, and some other re- lated species. But little or no importance is attributable to the amount of silica present, or the acidic or hasic character of the feldspar or rock. The distinction of basic and acidic, of great interest mineralogically and chemically, has in fact little importance in the science of volcanoes, while that of fusibility is fundamental. The most basic of all the feld- spars, anorthite, is as little fusible as the most " acidic " of feldspars, orthoclase, and more so than the equally '' acidic " albite.^ It is plain, therefore, that the quality of being heme does not explain the fusibility of the lavas. Neither does it explain any other of the physical character- istics on which tlie peculiarities of the volcano depend. It is also true that the chrysolite (or olivine), the ultra- basic constituent of the lavas, has little influence on their physical characters except through its higli specific gravity, which is about o-o to 3-4. The mineral chrysolite is infusible, and cannot increase the mobility of the lavas ; and there is * In mv " Manual of Mineralogy and Petrography," page 436, 1 point out further that the distinction of alkali-hearing and not alkali-hearing among the silicates is of much more geological importance than the much used one of acidic and basic. KILAUEA A BASALT-VOLCANO. 147 fomuioiily not enough of it in the Kikuea rocks to diminish the mobility ; for ;i hirge part of the lava contains less than five per cent, and much of it less than one per cent. Chryso- lite is uUra-basic ; but this qnality has little volcanic im- portance. It is not the little amount of silica in it that i,s influential volcanically, but the much iron. The presence of much chrysolite does not even determine the distril^ution of the lavas of Mount Loa ; for, as shown beyond (p. 324), no Hawaiian lavas contain more chrysolite or have higher spe- cific gravity than some of those of recent ejection at the summit of Mount Loa. Eruptive Characteristics of a Basalt-volcano. — The obvious results of superior mobility and density in lavas are, as in other liquids : — First, greater velocity on like slopes, and thus an easier .flow, with less liability to be impeded by obstructions; a lower mininuun angle of flow, and consequently a less angle of slope for the lava- cones. Secondly, the vapors ascending through the liquid lava encounter comparatively feeble resistance, and hence the expansive force required for escape of bubbles through the lava to the surface is feeble ; and so also are the projectile effects due to the explosion of the bubljles. Hence the pro- jected masses commonly go to a small height — it may be but a few yards — and fall Ijack before cooling, instead of reaching to a height that involves their cooling and solidifi- cation in the air and the making thus of cooled fragments of lava or scoria, called cinders and volcanic ashes. The projectile proc(^ss in the basalt-volcano, as long as it is in its normal stage, makes, as stated on page 17, not cinder- cones, but driblet-cones, fifteen to sixty feet high, out of the projected masses, the falling driblets becoming plastered together about the small places of ejection. Among the pro- jectile results of volcanoes driblet-cones are at one extremity of a series, and cinder or tufa cones, many hundreds of feet 148 VOLCANIC ACTION. liisch, at tiie other. A cinder-cone of a thousand feet m height has fifteen to twenty thousand times the bulk of any driblet-cone. The process is one ; but the result varies with the mobility and fusibility of the lavas. Further : in the great lava-cone of a basalt-volcano in its normal stage, cinder or tufa deposits rarely alternate with the large lava-streams, while they commonly alternate in other kinds of volcanoes. Further : cinder-cones and beds of volcanic ashes may form about a basalt-volcano, as already explained, whenever the condition of insufficient heat is in any wa}^ occasioned. The above views as to the characteristics of a normal basalt-volcano are sustained by the facts from the volcanic mountains of all the Hawaiian Islands. In the first place, the slopes are not only the lowest pos- sible, usually from less than 1° to 10°. but continuous flows of 10" to 90"* occur. The author has seen many of them descending as unbroken streams vertical precipices on south- ern and western Hawaii. The example shown in Plate XL is small compared with many about Mount Loa. Again : the alternation of the lava-streams of the great volcanoes with deposits of volcanic sand, scoria, or stones that were ejected from the great craters, is of rare occurrence ; and such deposits make only thin beds of the kind whenever they occur. In such examinations as the author was able to make of the walls of Kilauea and Haleakala and of the precipices and Ijluffs of Oahu he did not succeed in finding cinder or tufa deposits among the lavas of the body of the mountain, thouo^h a common feature wherever lateral cones have been thrown up. The walls of Kilauea are stratified from top to bottom, but with lava-streams, and comparatively thin streams. No evidence was found in the examinations of its walls of any intervening stratum or bed of scoria, tufa, or stones like that wdiich now covers its border. This testi- mony is not conclusive as to the alxsence of such projectile KILAUEA A BASALT-VOLCANO. 149 eruptions in former times ; for thin beds of scoria or sand like that just referred to — its thickness is only twenty-five to thirty feet — might be fused and annexed to the succeed- inti- lava-flow. But the evidence against great tufa-deposits amouLT the Hawaiian lavas, excepting those from lateral ejections, is sufficient. Ou the island of Maui no such beds of projectile origin were found in the walls of Haleakala, or in those of Wailuku valley, — the probable crater cavity of western Maui. On Oahu the pitch of the layers of lava along the Manoa and Nuuanu valleys is only 1° to 3° ; and in the precipices and bluffs which Ijound them I saw no layer of tufa. The thick tufa-deposits are confined to the beds of cinder and tufa cones, and these are common. This point needs investigation ; for the existence of even thin tufa-beds in alternation with the lava-beds of the great volcanoes of the islands may still be true, and such facts would have much interest. The author observed beds of conglomerate on Oahu and Kaui, but all may have come from lateral cones. The Crater of a Basalt-volcano is the same in Origin. His- tory, and Functions as those of Volcanoes of other Kinds, hut differs iisucdh/ in Form. — The crater of a great volcano probably has always its beginning in a great discharging fissure, or in the crossing of two fissures ; and it continues open until a temporary or final decline of volcanic action, whatever the kind of volcano. It continues open, (1) because of the fixed position of the lava-column, (2) because of the conduit-work going on through it in the discharge of vapors and lavas, and (3) because of tlie down-plunges in the crater consequent on the undermining which tlie discharge of the conduit occasions. The open end of a deep-reaching lava- column determines thus, by its discharges and the subsequent underminings, the existence of the crater ; and the crater, by the work done within and about it, makes the volcanic cone. 150 VOLCANIC ACTION. This appears to be the order of rank or importance in the phenomena, — the crater begins in the opened hssure, and is the indicator and future builder of the cone. In the history of the volcano the era of summit outflows niciy pass, and only lateral discharges take place ; and still the discharge of vapors from the lava-conduit and the accompanying move- ments in the lavas, together with the down-plunges in the cra- ter following the discharges, will keep the crater or portions of it in continued existence, and the work of eruption or out- flow, if subaerial, will be still adding to and shaping the cone. This is the present stage of Kilauea and Mount Loa ; and these are the results as they exemplify them. The action, functions, and processes are the same whether the lavas fill up to the summit before outflowing, or become discharged at a lower level by an opened fissure. Examples in the Hawaiian Islands teach also that vol- canoes may end with an open crater over two thousand feet deep, like Haleakala, a cone ten thousand feet high, or with a filled crater, as in the case of Mount Kea, thirteen thousand eight hundred feet high. The preceding remarks about the permanence of craters apply to other kinds of volcanoes as well as the basaltic ; but in the form of the crater the basalt-volcano has peculiarities, owing to the mobility of the lavas and the paucity of cinder discharges. The ordinary crater of the basalt-volcano is pit- like, with the walls often nearly vertical, and the floor may be a great nearly level plane of solid lavas. The liquid ma- terial of the extremity of a conduit works outward from the hotter centre, through the fusing heat and the boiling and other caldron-like movements ; and hence, where the mo- bility favors freedom of action in these respects, it tends to give the basin or crater a nearly circular form, with steep sides. Besides, when the discharge takes place there is usu- ally a fall of the walls, which is still another reason for vertical sides and the pit-like form. KILAUEA LAVA-COLUMN. 15 1 The small lava-lakes of Kilauea, and the Great South Lake also, after a discharge (or an eruption, as it is usually called), are literally pit-craters. Such was the condition of the Great Lake after the eruption of 1886. They all illustrate how the great pit-crater, Kihxuea, was made. The "lower pits" of 1823, 1833, 1840, are other examples. Such pit-craters are normally circular ; but where there is a large fissure beneath the crater they may be much elongated. From the considerations which have been presented we see why the volcanic mountains of the Hawaiian Islands, with slopes rarely exceeding 10° in angle, differ so widely from the great andesyte cones of western North America, with their high slopes of 28° to 35^. We see that the fact of being basalt-made means much in a volcano ; that it affects pro- foundly all the movements and the results of those move- ments, as well as the shapes of the mountains and of their craters. 2. Size of the Kilauea Lava-column. To appreciate the power at work in Kilauea and under- stand its action, we should know, if possible, the diameter of the lava-column beneath ; and for this we have to look to its condition both in times of eruption and in periods of relative quiet. In view of the greatness of the discharge in 1823, — so undermining, owing to its extent, as to drop abruptly to a depth of some hundreds of feet the floor of the crater, leaving only a narrow shelf along the sides, — we reasonably con- clude that at that time the lava-column beneath the floor was of as large area as the Kilauea pit itself, — or nearly seven and a half miles in circuit. We may also infer that, immediately before the discharge, wherever there was a lava- lake, the liquid top of the column was up to the floor of the crater, and elsewhere not far below it. The inference is sim- 152 VOLCANIC ACTION ilar from the eruptions of 1832 and 1840. When the floor of the pit fell at the discharge in 1840 it was not thrown into hills and ridges, as it might have been had it dropped down its four hundred feet to solid rock in consequence of a lateral discharge of the lavas beneath ; on the contrary," it kept its flat surface, thus showing that it probably followed down a liquid mass, that of the subsiding column of lava. But it is probable that the conduit had then, and has still, a larger area than that of the Kilauea crater. At the eruption of March, 1886, when the emptying of Halema'uma'u and its bordering lake at the south end of Kilauea was all the visible evidence of discharge, the sol- fatara at the north end, two and a half miles from Hale- ma'ma'u, showed sympathy with the movement ; for the escape of vapors from its fissures suddenly ceased, as if the source of the hot vapors had participated in the ebb, while a few hours before the discharge the vapors were unusually hot, so as to prevent the use of the bath-house. Thus, even now, during a comparatively small discharge, we have evi- dence that the two distant extremities of the crater are un- derlaid by intercommunicating liquid lava. Mr. Brigham speaks of hearing in 1880, when at the vapor bath-house in the solfatara, sounds from below, — ''rumbling and hard noises, totally unlike the soft hissing or sputtering of steam," ^ — a fact that seems to favor the above conclusion. Further, throuo;h all known time, as now, several of the fissures in the solfatara region have discharged, besides steam, sulphur- ous acid freely ; and this is probably from liquid lavas. The summit of the conduit must, therefore, be even larger than all Kilauea. To this may perhaps be added the border- ing; reg-ion of fi.ssures and abrunt subsidences ; for subsidences or down-plunges indicate imder mining ; and undermining here means the removal of liquid material from beneath. With this addition to the limits, the width is sixteen thou- ^ American Journal of Science, 1887, .\xxiv. 27. IN THE ORDINARY WORK OF KILAUEA. 153 sand feet, and the length as much, plus a mile or more to the southwest, where the fissures of 1868, if not also of earlier date, are giving off hot vajDors abundantly. But while this may be the area of the upper extremity of the lava-column, its top surface is not a level plane, as the condition of the region over it indicates. A small part of it at all times (with short exceptions after an eruption) has ex- tended up to the surface in Halema'uma'u, and occasionally in other lava-lakes during times of special activity ; for each such lake, however small, nuist have its separate conduit reaching down to the general liquid mass and giving upward passage to the working vapors. We learn, hence, that what- ever the number of these large and small conduits, they may act — that is, overflow, and rise and fall in level — indepen- dently, because the size is very small compared with that of the reservoir from which they rise. 3. Ordinary Work of Kilauea. By the ordinary work of Kilauea is here meant the work which is carried on between epochs of eruption. A large part of it is the living work of the volcano, the regular daily action, never joermanently ceasing except with the decline and extinction or withdrawal of the fires. The deep-reaching column of lavas, which is the source of the heat and centre of this living activity, owes a large part of its power to act the volcano, and make a volcanic moun- tain, to the presence of something besides heat and rocks. Vapors are ever rising and escaping from the conduit, and though lazy in the clouds above where their work has come to an end, they carry on nearly all the oi^dlnani action of a crater, even that of greatest brilliancy and loftiest fiery projection, as well as the gentler play of the fires. But these vapors have not produced the great eruptions in Kilauea smce the century begun ; they occasion only its 20 154 VOLCANIC ACTION quiet or lively activity in periods of regular work between eruptions. I add also, lest I be misunderstood, tliat tbe vapors are bad for fuel, as they tend to put the fires out, but good for work. * There is another source of work, perhaps a perpetual source during the active life of a volcano as it is a perpetual source of heat ; namely, the ascensive force of the conduit lavas. But, unlike the vapors, it is an invisible agency, slow in its irresistible movements. What are its limita- tions, and what its source, still remain undetermined. The other agencies concerned in the ordinary work have only occasional effects. They include heat in work outside of the conduit, and hydrostatic and other working methods of gravitational pressure. Tabulating the agencies, they are as follows : — A. The vapors. B. The ascensive force of the conduit lavas. C. Heat, dis|)lacing, disrupting, fusing. D. Hydrostatic and other gravitational pressure. All these agencies do their work around the lava-conduit, as their central source of energy, or about its branches, and therefore, as has been explained, pericentrically. A. THE WORK DONE BY VAPORS. Only part of the work of vapors is of the permanent kind, carried on, as above described, by the vapors rising through the lavas of the conduit. Another efficient part, but most efficient in times of eruption, is dependent on vapors gener- ated outside of the conduit. In addition, there are the chemical effects of vapors. The work includes : — 1. The effects of the expansive force of vapors in their es- cape from the liquid lavas : projectile action and its results. 2. The effects of the expansive force of vapors within the liquid lavas : vesiculation and its results. IN THE ORDINARY WORK OF KILAUEA. 155 3. The eli'ects of vapors generated outside of the conduit : fractures, displacements, etc. 4. The chemical action of vapors; which is considered in this work only as regards certain metamorphic effects. 1. The Vapors concerned: their Kinds and .Sources. The vapors of Kilauea have not yet been made a subject of special investigation. Still, there is no question that the chief xcorhiwj vapor is the vapor of water ; besides which there is a little sulphur gas, and probably some atmospheric air. Investigations elsewhere have establislied the fact of the vast predominance of water-vapor among aerial vol- canic products, proving that less than one part in one hundred is vapor of any other kind. The statement of Mr. J. S. Emerson ^ that on the west n^argin of Halema'u- ma'u, at one of his surveying stations in April of 1886, to leeward of a '' smoke-jet," he continued his work '' without regard to the smoke whicli the wind carried over him within a few feet of his head," is proof that the air held little sul- phurous acid. Mr. Brigham was led to conclude, from his seeing so little vapor rising from the Great Lake during his visit, that too much influence had been ascribed by others to water ; and this view is presented also by Mr. W. L. Green, of Honolulu, who refers part of the movements in the lake to escaping atmospheric air ; the air IxMug supjjosed to be car- ried down by the splashing and jetting lavas, there to be- come the source of the splashing, and to become confined in this and other ways, and be carried deeper for other work.^ But the amount of vapor escaping from a lake in times of moderate activity, when it is mostly crusted over, is very small, being only that from the vesicles (p. 166) and breaking bubbles in the actively liquid portion ; and in * American Journal of Science, 1887, xxxiii. 90. 2 Vestiges of the Molten Globe, part ii., 8vo^ Honolulu, 1887. 156 VOLCANIC ACTION a state of brilliant action, the hot air above, up to a height where the temperature is diminished from that of the liquid lavas to oU0° ¥., will dissolve and hold invisible nearly five times as much moisture as at 212" ; up to 440°, sixteen times as much ; and to 44G°, twenty-seven times. Tlie absence of vapors over a flowing lava-stream is made evi- dence against the presence of water ; but if all is from one source, there should be none except at the source. The amount of sulphur in the vapors, and its condition be- fore the escape from the lava, whether as sulphur vapor sim- ply or as sulphurous acid (sulphur dioxide), are questions for the future investigator. Pyrite, or some iron sulphide, being its probable source, I add that I have detected pyrite in the lava of a dike on Oahu, \mi not in the lavas of the crater, where we should hardly expect its presence. Chalcopyrite (copper pyrites) may also be present, as stated on page 73. The faintly greenish tint of the flames mentioned on pages 88. 96, 119, may have this source. Carhonic acid has not been observed escaping from fuma- roles aljout any part of the Hawaiian Islands, and no frag- ments of limestone have been found among the ejectamenta of Kilauea or Mount Loa. The volcanoes stand in the deep ocean, and the conduit nnist come up through old lavas for thousands of feet, and hence carbonic acid is only a pos- sible not a prolja1)le product. The position of the volcanic region in mid-ocean, where continental geological work has most probably never gone forward, makes it almost certain that there is none above the level of the ocean's bottom. The presence of lujdrogen among the escaping vapors re- mains to be determined. The pale flames seen about the Great Lake may come from the burning of escaping hydro- gen or of sulphur vapor or of hydrogen sulphide. The source of the ivater or moisture, whence comes the chief part of the escaping vapors, is probably atmospheric. IN THE ORDINARY WORK OF KILAUEA. 157 On this point the arguments appear to be as strong now as in 1840. Kilauea is situated, like Hilo, in a region of ahnost daily mists or rains, and if approaching Hilo in amount of precip- itation, as is probable, over one hundred inches of rain fall a year. Tables give over two liundred inches some years for Hilo. The whole becomes subterranean, except what is lost by evaporation ; for, owing to the cavernous and fissured rocks, there are no running streams over the eastern or southeastern slopes of the island south of the Wailuku River, which comes down from the northwest to Hilo. That which falls into Kilauea and on its borders gives moisture to the many steaming fissures ; and sometimes it makes a steaming area of the whole. But this part has very little to do with the volcanic action. Part of the subterranean water follows the underground slopes seaward, as shown by copious springs in some places near the shores, and takes no part ordinarily in the volcanic work. But another part must descend by gravity vertically, or nearly so, and keep on the descent far below the sea-level. It has been shown on a former page (p. 125) that much the greater number of the eruptions have occurred in the months from March to June, and this appears to indicate a dependence of the action to some extent on the abundance of precipitation.^ Moisture may be gathered also from all moist rocks along the course of the conduit in the depths miles below the reach of superficial waters, as suggested by different writers on vol- canoes. But any dependence on the amount of precipitation would show that this is not its chief source. Another source of water is the sea. But sea-water could ^ Tlii.s view with regard tf) the sources of the waters is sustained by several writers. It is well presented, with fxplanations at len^i^th as to the water-line in the volcanic mountains, in a paper »n " The Agency of Water in Volcanic Erup- tions," by Prof. .Joseph Prestwich, Proceedings of the Royal Society, .\li. 117. 158 VOLCANIC ACTION not ordinarily gain access to the lava-column except at depths much below the sea-level, on account of the abun- dance of subterranean island waters pressing downward and outward. Further, no one has yet reported evidence of the presence of marine salts, or chlorides, beyond mere traces, among the saline products of Kilauea or ^lount Loa after an eruption. A third source of moisture is the deep-seated region in or beneath the crust whence the lavas come. Of this we know nothing. The fact that the presence of such moisture below would make this a dangerous earth to live on has been urged against the idea of such a soin"ce. Since all ordinary action in Kihiuea, and also in Mount Loa, is of the quiet non-seismic kind, the introduction of water iuto the conduit must be an ordinary and a quiet process, not one of sudden intrusion through fissures. Sud- den intrusions may sometimes take place for eruptive effects, but of these we are not speaking. The facts from the vesic- ulation of some lava-flows of Mount Loa, brought out beyond (p. 166), give further evidence as to the quiet molecular oc- clusion of the waters. Moreover, as remarked on page 19, the possibility of this method of imbibition appears to be demonstrated by Daubree's experimental work, which proves that the process will go on through capillarity or molecular movement, against the opposing pressure of vapors within.^ He uses the fact to explain the origin of volcanic vapors. 2. The Effect of the Expansive Force of ^apors in their Escape FROM THE Liquid Lavas : Projectile Action. All the lava-lakes of the crater, whether one alone exists or many, and the smaller vents over fires that are concealed ^ Geologie Experimentale, 2 vols. 8vo, Paris, 1879, p. 235. The temperature of the liquid lava is nearly that of the dissociation tempera- ture of water — 1985° F. to 2370° F., according to M. H. St. Claire Deville, — and higher than this no doubt at depths below. But that dissociation takes place within the conduit, under the pressure there existing, is not satisfiictorily proved. IN THE ORDINARY WORK OF KILAUEA. 159 but not at too groat depths, send forth vapors, which in their effort to escape as bubbles through a resisting me- dium, that is, the lavas, do projectile work. The vapors thus produce the play of jets over lava-lakes with the muffled sounds and tremor of ebullition ; and also the splashing and the throwing of spray from open fire-places along the borders of the crusted lakes. They dash up the melted fragments from a blow-hole with a rush and roar " rivalling sometimes a thousand engines," thus introducing the coarser effects of gunnery into Kilauea. They make the thin crust of the crusted lake to heave and break, press into rope-like folds the lava along the red fissures, or start a new play of fiery jets, high or low, and frequently several in alternate play; or they make openings and push out a flood of lava ; and occasionally, when rising in unwonted volume, they make lava-fountains of unusual heights over the lakes, with at times loud detonations. The projectile force required to throw up jets of lava to the heighV which they ordinarily have in times of brilliant activity, thirty feet or so, is even less than a calculation from the heiglit-, diameter, and density would make it, because the jets before they reach their limit usually have become divided into clots, instead of remaining a continuous stream. The fact that the throw in the projectile action of a crater is usually vertical is well shown in some of the vertically columnar forms of driblet-cones. This is the case in that of the figures on pages 71, 91, in which the column was elongated vertically, although a result of successively de- scending drops. This vertical throw — due to the fact that the top of the bubble is the weak, and therefore the explod- ing, spot — makes the projectile action good for throwing upward, hut not good for a destructive homhardment of a crater's vmlls. Common observations would lead us to expect that in a low state of the fires, when the large lake is for the most 160 VOLCANIC ACTION part thinly crusted over, the point of greatest heat and action would be toward the centre ; instead of this, it is usually at the margin, and often in oven-like places partly under the cover of the border rocks. The only explanation that now appears is that already given, — that along the border, under cover, the outside cold, or that of the atmosphere, is much less felt than over , the central portion. One of the secoiidary results over the floor of the crater of the projectile work is the making of the fantastic driblet- cones, formed often about blow-holes out of the descending clots and drops and Avorming streamlets, as already explained. Occasionally the particles of the projected lava are small and descend in small showers of loose, smooth-faced, but variously shaped bullets and granules around the vent ; and this is the nearest the crater at present comes toward producing cinder-cones. Besides making driblet-cones, the projectile work raises somewhat the borders of the lakes. Further, the small over- flows, lapping in succession over the borders, often make them steep, and keep increasing their height until a heavier outflow sweeps one side or another away. A third incidental result of the projectile action is the making of capillary glass, or Fele's hair, from the glassy part of the lavas. In the jetting and splashing of the lavas the flying clots and drops pull out the glass into hairs, — just as takes place in the drawing apart of a glass rod when it is melted at middle. Mr. Brigham says that "the drops of lava thrown up draw after them the glass thread, or some- times two drops spin out a thread a yard long between them." His new observations of 1880^ accord with this explanation, but are remarkable for the length and size of Pele's tresses reported as hanging from the roofs of the fiery recesses. 1 American Journal of Science, 1887, xxxiv. 22. IN THE ORDINARY WORK OF KILAUEA. 161 The microscopic structure of the capillary glass has been studied with care by C. Fr. W. Krukenberg/ In his fifty fio-ures, a few of which are here copied, the glassy fibres are sometimes forked or branching, sometimes welded at cross- ings, and often contain air-vesicles (o, 4j and microscopic Pelf's Hair. crystals (1, 2, o), often tubidar (1, 2) through the draw- ing out of a minute air-vesicle. They also show that the air-vesicles sometimes continued expanding as the glass was drawn out, and that the hair is often enlarged about enclosed crystals. The crystals are rhombic, as in the figures. The facts make it evident that the glass is far from being pure glass. 3. The Effects of the Expansive Force of Vapors within the Lavas. — Vesiculation and its Mechanical P>fects. Orifjln. — Vesiculation, the making of bubble-like cavities in a melted rock, is a noiseless unseen effect of the vapors that are rising and expanding ivithin the lavas. The expan- sion necessary to produce them is resisted l\y the cohesion in the lava and l)y the pressure. Consequently it is a very com- mon feature of the easily fusible volcanic rock basalt, but not of trachyte or rhyolyte, except in pumice, the glassy scoria of these rocks ; and even this glass (obsidian) commonly holds to its moisture, if it contains anv, without vesiculating;. Owing to superincumbent pressure, the maximum depth of vesicles is small, as has long been recognized ; but how ^ Micrographie der Glasbasalte voni Hawaii ; petrographische Untersuchung, 38 pp. 8vo, with 4 plates, Tiibiiigen, 1877. 21 162 VOLCANIC ACTION small in basalt or any other rock, has not been ascertained by experiment. It probably does not occur in the Hawaiian Islands below a depth of a hundred feet. Above the lower limit vesicles may increase in number and size toward the surface, and be largest in the scum or crust, as within Kilauea ; but this variation upward is not always a fact. Kinds. — Five styles of vesiculation may be distinguished in the Kilauea ejections, two of which characterize stony lavas, and three scorias. 1. That of the ordinary lava-stream of the floor of the pit. The vesicles are oblong and of ii-regular shape, and con- stitute from less than one to fifty or sixty per cent of the mass of the rock. The form is spherical when the vesicles are very few and small. 2. That of the common stony sj^herically vesiculated lava. The vesicles make thirty to sixty per cent of the mass, and are too small to be elongated much by the flow. This kind of lava occurs in streams outside of Kilauea, and in many about the slopes of Mount Loa. The best example of it I have seen, and the basis of the following description, is that of the 1880-1881 Mount Loa flow, near Hilo. The small uniformly crowded vesicles con- stitute about forty per cent of the mass. They characterize the lava, with scarcely any change in size and numbers, to a depth (as I found in a tunnel within the lava-stream whose floor was similar) of ten or twelve feet. Below this depth of ten or twelve feet the lava, as I learned from Rev. E. P. Baker of Hilo, is probably more solid, this being usually the case. The scoriaceous kinds are — 3. That of the glassy scoriaceous crust of the lava-stream inside of Kilauea, and of the scum of its lava-lakes (p. 70). The vesicles are sixty-five to seventy-five per cent of the mass ; they are elongated, those at top mostly closed, those of the bottom of the crust commonly very large. The half- IN THE ORDINARY WORK OP KILAUEA. 163 solid crust of the lake is sometimes so thin that stones thrown on it slump through. The glass is easily fusible, and hence its rapid fusion and cooling. An analysis of this scoria-crust by Prof. 0. D. Allen proved it to have the com- position of ordinary basalt.^ No analysis has been made of the stony lava of Kilauea for comparison. 4. Ordinary scoria, such as is common about cinder-cones outside of the crater, mostly stony in texture ; the vesicles sixty-five to ninety-five per cent of the mass. 5. Spongy thread-lace glassy scoria, occurring as a layer twelve to sixteen inches thick over the southwestern border of Kilauea, as stated on page 44 ; the vesicles ninety-eight to ninety-nine per cent of the mass ; their walls in the coarser varieties sieve-like or reticulated, in the finer like thread-lace in texture. Similar spongy scoria is reported as occurring at the summit of Mount Loa and about the sources of some of the Mount Loa hiva-llows. Since a cubic inch of the finer thread-lace scoria contains only VI per cent in bulk of rock material, a layer of solid basalt glass one inch thick would l^e sufficient to make a sixty-inch layer of the spongy material, and probably a seventy- five to a hundred inch layer of the much more common coarser variety, in which are some large vesicles occasionally half a cubic inch in size. ^ Professor Allen's analysis (American Journal of Science, 1879, 3d series, xviii. 134) is in column A, below. For comparison the composition is added of (B) the doleryte (diabase) of West Rock, New Haven, Conn., of Triassic age, by Mr. G. W. Hawes (Ibid., 1875, ix. 186), and of (C) a " typical" basalt from Buffalo Peak, east of the west fork of the Platte, between the two Parks, by R. W. Woodward (De- scriptive Geolo,t,'y, " Geology of the Fortieth Parallel," 1877, ii. 126) SiOa AUG;, FeoOs FeO MnO MgO CaO NaoO K.O ign. P.,05 A 50.75 16.54 2.10 7.88 trace 7.65 11.96 2.13 0.56 0.35 = 90.92 B 51.80 14.21 3.55 8.26 0.42 7.63 10.68 2.15 0.39 0.63 0.14 = 90.86 C 49.04 18.11 2.71 7.70 trncp. 4.72 7.11 4.22 2.11 1.29 TiO.2 2.46 = 99.47 I add that I do not cite here the analyses of the rocks and volcanic glass of Kilauea made by another for me and published in my " E.xpedition Report," be- cause they are erroneous and should be rejected. 164 VOLCANIC ACTION The vesicles of the finest kind are mostly one thirtieth to one fortieth of an inch in diameter, like those of the 1880- Cells of thk Thrkad-lace Scoria. 1881 Mount Loa flow ; but their walls are reduced to threads corresponding to the edges of polygonal vesicles. Fig. 1 shows the general appearance of the surface in a maonified IN THE ORDINARY WORK OF KILAUEA. 165 view. The forms of the skeleton polygonal cells are for the most part either twelve-sided or fourteen-sided figures, having a perimeter of ten or twelve pentagonal faces in two alter- nating rows, and bases of five or six sides. The twelve-sided cells are bounded by the edges of pentagonal dodecahedrons such as come from the mutual pressure of spheres, except that they are distorted usually by compression and by elonga- tion or abbreviation. The fourteen-sided, which are much the most common, are similar to the twelve-sided in general form, but have hexagonal bases. Fig. 2 is a side view and Fit;-. 3 an end view of one of the latter kind, and Fig. 4 shows a group of such cells as seen over the surface of the scoria (a cut or broken surface, for it is impossible to handle a piece of the scoria without breaking off bits of the brittle threads). Fig. 6 is another of the fourteen-sided kind of less symmetrical form, as is common. One of the pentagonal dodecahedrons is shown in Fig. 7, and another in Fig. 8. There is often a more complex system of network through other crossing contour-threads, but the simpler forms are referable to those represented. The inside of the base of one of the large and therefore less regular forms is shown in Fig. 5 ; the diameter was about one twentieth of an inch. In the largest vesicles the walls are openly reticulated. The threads of tliis thread-lace scoria are not rounded, but parts of the conto\n\s of the three elliptical cells that were there in contact ; and Fig. shows a portion of one. Having this form, the glassy material of the threads is thickest, and therefore of darkest color, at the centre ; and they are still thicker and darker at the angles or jimctions of three threads. This glassy scoria calls to mind the vesic- ulation of an obsidian b}^ a high heat, converting it into pumice or scoria because of its occluded water, as illustrated 166 VOLCANIC ACTION by Professor Jucld, and also by Mr. Iddings in experiments with the obsidian of the Yellowstone Park. The Kilauea glass must have been penetrated molecularly with water to have produced such a result. Its ejection took place after the violent projection of great stones. — and apparently not long after, as it o^^erlies directly the layer of stones. The minute delicacy and brittleness of the threads in this scoria suggest a way of making fine dust by volcanic action, which is much more reasonable than that of mutual friction of projected fragments of scoria of the ordinary kind ; it thus helps in the understanding of the lofty dust-clouds of Kra- katoa and Tarawera. Amount of Moisture required for Vesicidation, its Distribu- tion, and its Origin. — The facts derived from the crowdedly vesiculated lava of 1880-1881, reaching from its source down to Hilo, over thirty miles, and throughout the whole range remarkable for uniformity and for depth in the stream, be- sides giving an opportunity to study the origin of the vesicu- lation and the amount of moisture it requires, presents also evidence as to the origin of the moisture in the conduit and its condition. 1. According to the report of Rev. E. P. Baker, the vesicles change little toward the summit except in becoming coarser, with thinner walls, at the source. From the mean size, one thirty-fifth of an inch in diameter, we ol^tain for the size of the jMrficJe of moisture required at the ordinary pressure to fill one of the vesicles, '000,000,007 of a cubic inch. What the size actually was, under the pressure and the temperature that existed at the time of vesiculation, cannot be deter- mined. But this much we learn, that the moisture was dis- tributed throughout the lava in a state of extreme division, actually or essentially that of molecular diffusion. 2. The space in the vesicles is forty per cent of the mass, as determined from the specific gravity of the rock-material. IN THE ORDINARY WORK OF KILAUEA. 167 2*98, and that of the mass with the surface varnished to ex- clude the water, 1-88. Tlie required water is hence '0003 per cent of the mass, or by weight -OOOl per cent ; showing that the cunount of loater I'equired for the vedcidation is exceed- ingh/ small. From the thread-lace scoria we find, since only I'T per cent of the mass is solid glass, that the amount of moisture re- quired to produce the vesiculation, at the ordinary pressure, would be 3-12-5 per cent of bulk, and 1-1 per cent by weight. The amount of moisture was hence not unusual for a rock, although the vesicles occupied 98*3 per cent of the mass. 3. The source of the flow of 1880, 1881, according to Mr. Baker, was about 11,100 feet above the sea-level. This is 2,575 feet below the summit of Mount Loa, or aljout 1,600 feet below the bottom of the summit crater. Before the out- break the liquid lavas were active within the crater ; that is, the length of the conduit above the place of outbreak was then about 1,800 feet. On account of the pressure of 1,800 feet of liquid lava no vesiculation could have taken place at this depth inside of the conduit ; but at the discharge the lavas escaped from the pressure, and the vesiculation by means of the diffused moisture must have then begun. Whether the vesiculation for the whole stream took place at or near the source cannot be decided without more knowl- edge of the flow and its actual sources than we now have. 4. The facts also tend to sustain the conclusion, before expressed, that the ingress of the subterranean waters, what- ever their source, took place by molecular absorption ; for it produced an essentially equable molecular distribution. T7ie Distribution and Functio?is of Moisture after reception into the Conduit. — 1. The above conclusions from the ve- siculation have prepared the way for additional deductions as to the distribution and movements of the moisture in the conduit. After its reception it is exposed to a heat at least 168 VOLCANIC ACTION 1500° F. beyond the critical point of water (773" F.), and re- tains the temperature of fusion to tlie surface. If the expan- sive force has at the ingress under the pressure any effective vakie, the accession of the moisture will diminish somewhat the density of the lava, that is, increase its bulk ; and this in- crease will be greatest along the central region of the conduit, because this is the region of greatest heat. If dissociation takes place the increase is still greater, as it adds to the bulk of the moisture. It is a question, therefore, whether the pressure of the denser lateral lavas of the conduit would not have some effect toward producing an upward movement along the hotter central region. 2. The mechanism of the volcano, as regards these inside vapors, seems then to be this : {a) a molecular absorption, at depths below, of subterranean waters from regions either side ; {h) a rise of the lavas, thus supplied with moisture, along the conduit from some cause (see beyond on "• the ascensive force of the conduit lavas "), and perhaps partly in consequence of the vapors present ; (c) after reaching a level where the pressure is sufficiently diminished, a union of the molecules of water into gas-particles, p}'oduclii(i by their ex- pansive force vesiculatiou ; [d) a further union of particles into bubbles, when the vapors are sufficiently abundant, in order to exert the greater expansive force required to escape through the surface of the lavas, producing jyrojectile residts. Mechanical Effects of Vesicidation. — Vesiculation tends in a quiet way to increase bulk, as the above-mentioned facts illustrate. It therefore will give increased Jieight to the liquid lava in a conduit. How deep down this effect is ap- preciable is a point of much importance in its bearing on the movements and levels of the lavas of conduits. If only to a depth of two hundred feet, an average of twenty per cent of vesicles would add only forty feet to the lieight or level of the surface. But if the vapor particles at all deeper depths are, through IN THE ORDINARY WORK OF KILAUEA. 169 iheir expansive force, undergoing gradual expansion as they work their way or are carried upward, we are still further in the dark as to the amount of effect of vapors on the bulk of the lavas in a conduit. After the author's observations of 1840, he was led to question, as is stated in his "' Expedition Report," whether the effects from this means might nut be sufficient to account for much of the excess of elongation of the Mount Loa column over that of Kilauea. This is ob- viously not so. But how much the elongation is, is an impor- tant question, and it has still to remain unanswered. 4. ayork of varors (iexkkated ultshje of the condlit : fractures, Displacements, and other Results. The conduit lias hot rocks around it ; and beneath the floor of the crater there are hot rocks about and over its upper extremity. The descending waters are driven back as vapor, and usually in a harmless manner. But a sudden in- cursion of subterranean waters happening under any circum- stances, might produce confined vapors of great amount and force. The natural effects of the pressure of such confined vapors are fractures, elevations, and subsidences, and, where pressure is brought to bear in a confined place on a source of liquid lavas, their injection into any open fissure at hand. These effects belong mostly to times of eruption ; but in a lighter form they may be part of the ordinary work of the crater. The lava-lakes of the bottom, even in quiet times, often have large overflows, and also outflows through fissures, that is, both superflnent and effluent discharges ; and it is probable that the cause here considered may be the occasion of part of them. Confined vapors are often generated also by the action of the heat of a lava-flow on moisture underneath it. As rains fall almost every day at Kilauea, there must be more or less moisture, underneath many parts of the cold floor ; and if a few hours' flow from the great lake should flood it with 22 170 VOLCANIC ACTION liquid rock, its 2000° F., which the bottom of the stream carries along and does not at once lose, would make vapor out of the moisture, having great expansive force. The large dome-shaped bulgings of the lava-streams and other undula- tions of the surface may thus be accounted for ; and many of the steaming fractures of the floor as well as those of the domes may have the same orighi. B. THE ASCENSIVE ACTION IN THE LAVA-COLUMN. Evidence. — The evidence in favor of an uplifting action by the ascensive force has been presented on pages 76, 109. It is briefly as follows : — 1. The observations in 1846 by Mr. Chester Lyman de- monstrate that in six years the lower pit of 1840, averaging ten thousand feet by twenty-five hundred in its diameters and nearly four hundred feet in depth, had gradually become obliterated, and chiefly through an uplift of the floor ; for the floor bore on its surface the talus of lava-blocks that had fallen from the walls. Overflows had done part of the work, but " subterranean force," as Mr. Lyman concluded, the larger part. Mr. Coan, who was with Mr. Lyman at the time, ap- preciated the evidence, and later described the lifting as " not uniform in all parts ; as sometimes taking place here and there abruptly ; but as producing nearly uniform results, ex- cept a greater rise toward Halema'uma'u." 2. In 1868 Mr. Brisrham arave further evidence as to the o o Lyman ridge by the representation of what remained of it in 1865 on his valuable map, though not, as his memoir shows, understanding its origin. Besides this the painting of the crater of about the same date (1864 or earlier) by Mr. Perry (p. 87), afforded confirmatory proof as to its position and extent at that time. 3. In 1848 Mr. Coan observed that a cone of broken lava, that had formed within the Halema'uma'u basin, was lifted IN THE ORDINARY WORK OF KILAUEA. 171 by " subterranean action," as he argued, because only slight additions were made to its outside by ejections. It con- tinued to rise bodily until it was as high as the near walls of Kilauea. Between 1880 and 1882 another debris cone began in the basin of Haleraa'uma'u, wliich, as he describes, rose in like manner without additions to its summit, and finally became two hundred feet or more high ; this cone continued to exist until the eruption of 1886. The subterranean force appealed to was plainly force aris- ing in some way from the lavas beneath. Mr. Coan, in his letters, supposed that the lifting was produced by the injec- tion of the lavas of the conduit into open spaces between the solid layers below. 4. Again, in the summer of 1886, three months after the eruption of that year, the debris from the fallen and falling walls of Halema'uma'u were made into a cone occupying a large part of the interior of the basin ; and from August on- ward, it was apparent that the cone so made was slowly rising, though having little outside additions; in October of 1886, its top was on a level with the rim of the basin ; in January, two hundred feet higher, so as nearly to overtop the south- eastern Kilauea walls. It was early apparent to visitors at the crater that the elevation was through action l)elow ; and soon the conclusion was general, among observers, that the cone, as expressed in the words of Mr. Dodge, of Jan. 14, 1887, was " rising slowly as though floating on the surface of the new lava-lake."^ ^ American Journal of Science, xxxiv. 70. When at Honolulu, Mr. Parinelee, of that place, informed the author that in August of 1886 he made observa- tions on the rate of change of level, by sighting from the Volcano House veranda over a post one hundred yards in front of the house, and marking the cliange of the line of sight on a pillar of the veranda. His observations were made between the 19th and 21st of the month. On the first day the rise, according to his calculated result, was sixteen feet ; on the second, seventeen feet ; and on the third, eight feet. These numbers are large. They were not verified by observations near the cone. They at least prove progress in the elevation. 172 VOLCANIC ACTION The ascensive force was thus proved to be great, and its effects to have fundamental significance. Method of Action. — It is a question whether, in the lift of the floor of the great crater in 1823, 1832, 1840, 1868, the lavas of tlie lava-conduit acted by direct thrust, or through injections into s[)aces between the layers of solidified lava be- neath it.^ The facts favor strongly the former of these views. In the first place, the lateral thrust in the upper lavas of a conduit is necessarily feeble ; for the conduit there, or near by, opens to the surface. Then, secondly, it is quite certain that the breadth of the Kilauea conduit at top has been, at the times of these uplifts of the floor, large enougli to i\ct somewhat equably against the floor. Thirdly, since the floor kept its even surface as it fell at the great eruption of 1840, it must have followed down, as already urged, the subsiding lavas. The flotation method, or that by direct thrust, seems therefore to be the right one. It is the obvious explanation of the lifting of the debris cones of Halema'uraa'u. Kilauea affords, as has been indicated, facts illustrating the details connected with the lifting movement. FauU-jolanes of the vp-and-down Movements about the Pit. — {1) The down-plunge of 1823, 1832, and 1840 left, for the most part, vertical walls bounding the '■ lower pit " so made. There is evidence that these were fault-walls; that is, planes of fracture with a vertical displacement along them equal to their height, or about four hundred feet in 1840 and six or eight hundred feet in 1823. In the reverse movement — that is, the rise after the down-plunge of 1840 — the old floor was carried up along the same fault-planes. The rate of rise, as shown on page 10, was seventy to one hundred and tliirty feet a year, which is to be divided be- tween {a) overflows, (h) vesiculation if this had any effect, and (c) ascensive force apart from vesiculation. 1 The latter is the explanation adopted by Mr. Brii,^hani in his paper of July, 1887, American Journal of Science, xxxiv. 19. IN THE ORDINARY WORK OF KILAUEA. 173 Further : these vertical fault-planes of 1840, and others subordinate to them along the border regions, appear to have determined the chief places of eruption — that is, of lava-lakes, cones, ovens, and opened iissures — in Kilauea durinr/ the 7iext flurty years. They were plainly the occasion of the wonder- ful girt of fires, four miles long and half a mile wide, which was three times repeated after the year 1846 before the erup- tion of 1868 (in 1855, 1863, and 1866), while the interior plateau suffered relatively little change from erupting forces, and in some parts was growing ohelo bushes and ferns. The position of the ''canal" in Kilauea in 1846, described by Mr. Coan and also Ijy Mr. Lyman as extending around the crater, bounded by the outline of the old black ledge and tlie Lyman ridge of lava-blocks, and which became gradually filled by inflowing lavas and debris, has here its explanation. The circumferential fault-planes of the pit of 1840 coincided with the face of the lower wall or precipice. The debris which fell from the wall necessarily fell to the floor beyond the plane, and there began the making of the talus. Through the fall of the face of the wall, the wall, and thereby the limit of the black ledge, retreated; and as the elevation of the floor went on, an interval was left between the talus and the limit of the black ledge, and along this interval lay the " canal." The annexed figure will serve to illustrate the point, notwith- standing tlie assumptions made in it. Let h h' be the wall of the lower pit, four hundred feet high, and the course of the fault-plane ; a h, the floor of tlie pit ; h' c, the surface of the black ledge. Let now the falls from the wall above e make the talus d e h with a slope of 45°, causing therel^y the wall (and limit of the black ledge) to retreat to g. If the floor be now lifted four hun- dred feet, to the position a' h', the debris of the talus d e h 174 VOLCANIC ACTION would make an elevation at top equal to d' e' h, besides filling up efh'(efh'= cV e' V = I d e h) ; the interval Vf g would represent the canal, and d' e' h' , one hundred feet high, the ridge. If the floor were raised fifty feet higher, the ridge would be lowered, say twenty-five feet, owing to material that would slip down into the canal ; and consequently, the heierht of the ridge above the floor over the centre of the crater would then be twenty-five feet less than before, while twenty-five feet more than it was above the black ledge. If no talus had been formed at the foot of the wall, an uplift of the floor of five hundred feet would have made a precipice of one hundred feet fronting toward the black ledge, the falls from which would have produced a steep talus. These are two conditions in the different parts of the ridge mentioned in Mr. Lyman's paper. Faidt-planes about TIalemaumau. — In Halema'uma'u, at the eruption of 1876, there was a circumferential fault- plane ; this seems to be implied in the fact that the return of lava was mostly through vents toward the walls, little coming up at the centre, and the fact that even a year and a half afterward the action was greater outside of the cone than at its centre. At the discharge, the debris from the tumbling walls fell beyond the fault-plane and made an accumulation of blocks, like the talus of the lower pit of 1840 ; and this, as Mr. Dodge's description shows and the photographs illustrate, was the material that became the cone as the lifting went forward. Conclusion. — By the above facts, it is proved that the conduit lavas of the volcano not only keep up the supply of heat, and carry on, by means of the vapors, projectile action and vesiculation, but also that they furnish power for lifting, in a quiet, unperceived way, the floors of craters with what- ever is upon them, and thus raising the level of volcanic IN THE OKDINARY WORK OF KILAUEA. 175 activity ; and that this g-oes forward as part of the ordinary operations of the crater. The action has long been recognized as a means of supplying heat and lavas, but not as a mechan- ical agent to the extent here indicated. The force at vi^ork in making the Gilbert laccoliths must be the same ; and Mr. Gilbert, in his report on the Henry Mountains, gave the first intelligible idea of its power.' But there is nothing in the action that leads us to suppose that it can, under any probable conditions, make jets or foun- tains of lavas, or work in blow-hole style. Each jet over a lake, and each large jet in a lava-fountain, has its local pro- jectile cause beneath the projected column of lava, and can- not be produced by any general upthrust movement in the great conduit. The imperceptibly slow uplift and fountain- making are incompatible effects. There seems to be, there- fore, no foundation for the comparison of the lava-fountains to the projectile effect in an " artesian boring made to a stra- tum of molten rock which had only been awaiting an oppor- tunity to overflow." ^ The source of the ascensive 7noveme7it has not been ascer- tained. It is most commonly referred to the pressure of the earth's crust on the lava-reservoir beneath, arising from subsidence in the earth's crust from secular refrigeration. Another explanation appeals to vapors from the deep source of the lavas. The possibility of some addition to the force through ascending vapors is referred to on page 168 of this volume. C. EFFECTS OF HEAT. From Change of Temperature. — Contractional effects from cooling — that is, fractures and changes of level — should be common in the crater ; for each stream has passed from a tem- 1 Mr. W. L. Green, Vestiges of the Molten Globe, pp. 168, 272. Mr. Green's examples are taken from action in the summit crater ; and when speaking of that crater, this point will be again considered. 176 VOLCANIC ACTION perature of 2000° F. or more to 70° or 80° F., and the upper surface of a stream rapidly so. Besides ordinary shallow frac- tures, the cause produces also an imperfectly columnar struc- ture in the cooled lava-stream below the upper foot or two. The cracks in the floor of Kilauea often expose quite good basaltic columns even when the whole thickness of the layer is hardly a dozen feet. There should be also larger effects in the Kilauea region arising from change of temperature between periods of great and little activity, or from periodical variations in the heat below, and changes of level in the lava of the conduit. But we have no special facts to report in illustration, although there are cracks innumerable in view that probaljly have this source. Tlie Dissolving Action of the Liquid Lavas. — (1) The refu- sion of the crust over the surface of a lava-lake by the liquid lavas is — as the history has shown — one of the common occurrences in Halema'uma'u and other lava-lakes. The intervals of cooling and refusion vary in length from a few seconds to an hour and longer. The crust of a lava-lake is often only the thin, easily fusible glassy scum ; but thicker crusts also yield to the heat. In the case of rapid transitions, the cooling may be due to the loss of heat by the expansion in the process of vesicula- tion ; and if the vesiculation takes place intermittently for any reason (as from oscillating movement in the lava-column or other condition) it would occasion the alternations be- tween the fused and crusted state. But for the crustings at longer intervals deeper movements may be concerned, and more study is needed before they are fully understood. (2) The disa2)peara7ice of floating islands is another effect of heat and chiefly of refusion ; for in some cases the islands have after a while — a year or more — disappeared. (3) The destruction of dehris-cones in Halema'uma'u is dependent on undermining by the active lavas and vapors IN THE ORDINARY WORK OF KILAUEA. 177 beneath ; and in one case the destruction was probably com- pleted before a period of eruption. The debris-cone, fifteen hundred to two thousand feet broad at base, which now occupies the centre of the Hale- ma'uma'u basin, is already in process of dissolution, as stated on page 110. It made no increase in height during the summer of 1887, but, instead, rather lost ground through the changes going on ; and the report of the spring of 1889 tells of a loss already of eighty feet in its height, — not eighty feet of its summit, but of the lower part that was within reach of or in contact with the liquid lavas. The description on page 105 by Professor Van Slyke of the cone as seen by him in July, 1886, gives particulars as to the steam-holes in and beneath the cone, and of the blowing-cone work which began this work of destruction. This destructive work brings the cone to its end either be- fore or during a period of eruption ; and a floating island may be the last phase before its disappearance. Oldening of New Lava-lakes. — With the intensifying of the fires of the crater there has often been, as the history shows, an opening of lakes over the interior of the crater, and especially along the borders of Kilauea, or the region of the black ledge. Such facts signify, as has been explained, that the broad underlying conduit of Kilauea, which is like a great reservoir of lavas beneath the pit, reaches at such a time up to the surface, not only in the Halema'uma'u basin through the great conduit, but also in minor lakes through secondary conduits. It is a query whether this has ever been brought about by new sources of vapor starting in the under- lying reservoir as a consequence of subterranean conditions ; whether hot vapors from such a source have not forced a way through to the surface in consequence of their own dissolving and fusing heat and that of the lavas, and thus have made a new lake, — as ascending air from the l)ottom of an ice- covered pond makes a hole through the covering of ice. But 23 178 VOLCANIC ACTION such lakes, as remarked on a preceding page, are generally begun over fissures ; and it may be that fissures under the general increased activity are all that are needed for the result. Extending the Limits of the Conduit hy Fusion. — Another suggestion comes from the fusing power of the Halema'uma'u lavas. If these lavas can slowly, even at their surface, fuse stony lavas, what is the extent of the fusing power at depths below where there is greater heat ? An increase in the heat from a subterranean cause would necessarily widen the limits of the conduit. It is a question wliether an extended sub- terranean bed of liquid lava, thick enough to remain per- manently liquid in spite of cooling agencies about it, can occupy its place without fusing and incorporating with itself any solid lavas directly underneath it, if such there be. A great lava-conduit, therefore, has probably its varying phases, like the fires at the surface, and includes extremes in breadth or enlargement as well as in contraction. The widest part should not be at the summit unless the cooling agencies are less effective, or the heat-making causes more effective, there than elsewhere. The Metamorphic Action of the Heed. — Metamorphic ac- tion also may be part of the quiet work of the volcano. The lava-column has its enclosing rocks, and at temperatures varying from that just below fusion to that of the outside rocks ; and vapors must be active in the hot regions. The throat of tlie conduit may well be, therefore, a region of recrystallizations, of the making of geodes, or the lining of fissures with crystals, out of whatever material was at hand, and different kinds, somewhat according to the tempera- ture. The effects of such metamorphism are exhibited, be- yond question, in the various mineral crystallizations of the ejected masses of Vesuvius. They are found also at Kilauea, as mentioned beyond. The repeated coolings and heatings (passing often to fusings), which Kilauea lava-lakes so well IN THE ORDINARY WORK OF KILAUEA. 179 illustrate, suggest an explanation also for the feathery angite detected by Prof. E. S. Dana in the lavas of Kilauea as well as of Mount Loa, as described beyond. D. HYDROSTATIC AND OTHER GRAVITATIONAL PRESSURE. 1. The hydrostatic pressure of the column of liquid basalt is 2-8 to 2-9 times that of water, supposhig the lavas while in fusion to be mainly in the glassy condition. This pressure was early recognized by Lyell as one of the possible causes of rupture in volcanoes. The cause may have its effects in a quiet way over the bottom of Kilauea, since the lavas often stand in the lakes at a height of fifty to a hundred feet above the floor outside of the surrounding cone ; but no facts yet observed can be positively referred to it. 2. Again, there may be undermimngs and therefore sub- sidences in the ordinary course of Kilauea changes, through discharsres followino; small fractures. Such effects over the floor of the pit are not at present distinguishable from those of other modes of origin. But the sinking of the floor of Halema'uma'u in the spring of 1889, mentioned on page 123, is probably an example within this subordinate pit. Having thus reviewed the ordinary operations of the crater — that is, those carried forward between times of eruptions — in the way of preparation for an eruption, the next inquiry is, What is needed to produce a great eruption of Kilauea ? The power of the rising vapors and that of the ascensive conduit-lavas — the two chief sources of ordinary activity — appear to be too feeble for any such result. Can eruptions take place without any increase of their activity within the crater beyond what has been described ? If so, how ? Before discussing this subject the history of the summit crater, Mokuaweoweo, should be first reviewed, as its facts afford important illustrations of the eruptive methods. 180 VOLCANIC PHENOMENA B. MOUNT LOA, AND ITS SUMMIT CRATER, MOKUAWEOWEO. The map of the island of Hawaii, reduced from the Gov- ernment map, making the frontispiece, should here be studied. It will enable the reader to appreciate the broad, almost plateau-like summit of the mountain, the relative position and heights of Kilauea and the Mount Loa crater, besides other points of interest in the history and discussion beyond. The present form of the summit crater, Mokuaweoweo, is shown on the map (Plate X.) by J. M. Alexander, reduced from the results of his survey. The height of the highest point given on it — 13,675 feet — differs eighty-five feet from Wilkes's determination of the same point in 1841. The history of the summit crater is mostly a history of the results of its eruptions, for few facts have been observed respecting the action within the crater. It has excited atten- tion when an eruption has been in progress ; but the chief outflows have begun below the summit, and the source of the outflow is usually the only place reached. Still there is much to be gathered from the reported facts. The records begin with the year 1832. 1. Eruptions of Mount Loa from 1832 to 1868. 1832, June 20. — On the 20tli of June, 1832, according to Rev. Joseph Goodrich, lavas were discharged from several vents about the summit.^ The fires continued to be visible for two or three weeks, and were seen from Lahaina, on the western coast of Maui, a hundred miles to the northwest. 1 Goodrich, American Journal of Science, 1834, xxy. 201, letter of Nov. 17, 1832. Plate X. 7^ J^ejirrT/i , 3:aa rnitca, t^r'CQ. , 3:e Sr/. miles. Circiirtifer'ancc, Oj PcT I <3%i 1 Tixti, l?e ale CDm.-VVilkee. r.S.TJocIgc '"^ /N20°E MAP OF MOKUAWEOWEO, MAUNA LOA, HAWAII. 2,000 ft. - 1 inch. Surveyed by J. M. Alexander. 1885. IN THE HISTORY OF MOUNT LOA. 183 Nothing is known of any large discharge of lava, and no mention is made of accompanying earthquakes. The outbreak of Kilauea in 1832 occurred about the same time, but possibly a few months later. 1834, January 29. — Mr. David Douglas, the naturalist, who was the lirst to ascend Mount Loa and determine baro- metrically its altitude, describes the crater, in his " Journal," ^ as having great chasms in the bottom that he could not fathom '' with a good glass and the air clear of smoke," and says further that " the depth to the bottom on the east side was by an accurate measurement with a line and plummet 1,270 feet;" that the southern part of the crater, " where the outlet of the lava had evidently been, must have enjoyed a long period of repose." He mentions hearing light, hissing sounds from fissures in the summit, that might " perhaps be owing to some great internal fire escaping." He adds: '' There is little to arrest the eye of the naturalist over the great portion of this huge dome, which is a gigantic mass of slag, scorise, and ashes." 1841, January. — Captain Wilkes was at the summit dur- ing the latter part of January, 1841.^ Lieutenant Eld, by taking angles from the bottom of the crater, made the west- ern wall 784 feet high, and the eastern 470 feet. The only sign of activity was the escape of steam and sulphur gases from many deep fissures over the bottom, especially on the west side. The fissures had generally a N.N.E.-S.S.W. direc- tion. There was one cinder or scoria cone at the bottom, 1 Companion of the Botanical Magazine, 1836, ii. 175, and in a letter to Captain Sabine, dated May 3, 1834 (Journal of the Geographical Society, 1834, iv. 333). See page 58, on the letter to Dr. Hooker and the evidence against it. 2 Narrative of the Expedition, iv. 152, 156, 159. The descriptions of the crater are from descents made into it by Dr. G. P. Jndd of Honolulu (p. 152) and Lieut. Henry Eld (p. 156). Wilkes's map has its longer diameter, through some mistake, north and south in direction ; this is corrected in the copy on the following page. 184 VOLCANIC PHENOMENA according to Dr. G. P. Judd, toward the southwest side, hav- ing a height of about two hundred feet. Other steam-cracks were observed outside about the pit-crater of the south-south- west end ; and one, which they "designated the great steam- crack, led from the top a long distance down the sides of the mountain toward the south ; " and a great depth was indicated ^'%.- /__:_.- ■2' ,^^S. w »r PfuduiuTH Peak .m IM 12^4 SOOOtt: The Summit Crater. by the reverberations from a block of lava which was dropped into it. Small driblets of lava were observed along some of these fissures, indicating feeble ejections. In Wilkes's map, as shown in the above outline copy, seven small cones are faintly represented on the bottom of the crater, although the descriptions speak of only one. IN THE HISTORY OF MOUNT LOA. 185 1843, Geeat Eruption commencing in January. — In January^ 1843, began an outflow that continued for about six weeks. Clouds above on the 9th made the first announcement to the people of the islands. During the following night, ac- cording to Dr. L. Andrews,^ a brilliant light appeared at the summit, looking, as Mr. Coan states, like " a small beacon- fire." ^ In a week the light disappeared. In the mean time the lavas had commenced their discharge. Mr. Coan as- cended to the source, about eleven thousand feet up, and found two large craters near together, very deep and active. The stream of lava flowed toward Mount Kea, but gave oft" a westward branch, toward Hualalai, near its source. At the base of Mount Kea a branch went northward toward Waimea, and another eastward toward Hilo. Mr. Coan states that over the crusted surface of the stream were many steam- ing openings, twenty to fifty feet broad, down which he saw the lavas rushing along the tunnel-like way, " with awful speed, some fifty feet below us ; " large stones thrown on the surface were carried " instantly out of sight before sinking into the stream." The action was much diminished in six weeks, but was " still somewhat vehement at one or two points." In March of 1843 Messrs. Paris and Coan found snow on the summit. Mr. Andrews states that during the progress of the erup- tion Mr. Wilcox visited Kilauea and found no signs of sympathy. 1849, May. — A brief notice of brilliant fires at the sum- mit crater in the month of May, 1849, is contained in a letter of Mr. Coan's, dated January, 1851. He says that the light was first noticed after the extraordinary activity in Kilauea. "I cannot say that they were coincident." For two or three 1 Andrews, Missionary Herald, xxxix. .381, letter of Feb. 6, 1843. 2 Coan, Ibid., xxxix. 463, letter of Feb. 20, 1843 ; xl. 44, letter of April 5 ; American Journal of Science, 1859, 2d series, xxvii. 411; Life iu Hawaii, 1882, p. 270. 24. 186 VOLCANIC PHENOMENA weeks a brilliant and lofty column of light was seen over the mountain. There is no reported evidence as to any surface outflow of lavas, and none of an earthquake.^ 1851, August 8. — A short flow commenced at this date a few miles west of the summit.^ From Hilo a column of clouds was seen by day, which was fiery by reflection at night. The eruption continued, so far as could be seen from Hilo, only three or four days. No earthquake was reported. Mr. William T. Brigham in 1864 visited the flow, and states^ that the outbreak of 1851 occurred about a thousand feet below the summit, ''or two hundred feet below the bot- tom of the crater." He estimated the length of the stream at " ten miles and the average breadth less than a mile," and the volume " one hundred and sixty million cubic yards of lava." " The greater part is the pahoehoe, although some aa occurs." The course was westward, near that of an old stream toward Kealakekua. 1852, Great Eruption commencing February 17. — The eruption of 1852 began only six months after the brief action of 1851, as if its supplement. The place of outbreak, accord- ing to Mr. Coan,* was on the north side of the summit, near that of 1843. When first seen the light looked like " a planet just setting" over the top of the mountain. In a few minutes the whole summit was brilliant, and Hilo also ; and a stream of lava commenced its flow down the mountain. Forty hours later the fires had apparently become extinct. But after three days, on the 20th, the chief flow began at 1 Coan, American Journal of Science, 1851, 2d series, xii. 82, letter of January, 1851. 2 Ibid., 1852, xiii. 395, letter oC Oct. 1, 1851; and D. D. Baldwin, Ibid., p. 299, from " Polynesian " of August 23, 1851. 3 Volcanoes of the Hawaiian Islands, 1868, 4to, p. 389. 4 Coan, American Journal of Science, 1852, xiv. 105, 219; Life in Hawaii, p. 279. IN THE HISTORY OF MOUNT LOA. 1S7 a point on the eastern side about ten thousand feet above the sea-level, near the terminus of a line of fissures leadino: down from the place of the first outbreak. The escajylng lavas rose at first in a lofty fountain, and then flowed east- ward for twenty miles. On the 2Tth Mr. Coan reached the place of the fountain, approaching it on the windward side within two hundred feet. He found the lavas playing, as he states, to a height of four to five and seven hundred feet, by angular measurement, in ever-varyhig forms of towers, pyra- mids, and spires, and with variations also in colors from white heat at base to red above, and then to grayish red and gray. Great volumes of lava were ascending and descending, not intermittently but continuously ; and the " surging, roaring, booming " sounds were almost deafening, but without earth- quake from beginning to end. Ashes and capillary glass fell in the streets of Hilo. The stream stopped about ten miles from the village. The grand eruption was in blast only twenty days. All this time Kilauea was quiet. In Jul}^ Mr. Coan ascended again to the crater or place of discharge,^ and found the fires extinct. He says a kind of " pumice " was abundant and widely scattered ; " we found it ten miles from the crater, and it grew more and more abundant till we reached the cone, where it covered the whole region to a depth of five or ten feet." An ascent to the active fires was made early in March by Mr. H. Kinney^ and Mr. Fuller. Mr. Kinney, speaking of the sounds from the cataract of liquid lavas, says : " Its deep unearthly roar, which we began to hear early on the day before, waxed louder and louder as we drew nearer the action, until it resembled the roar of the ocean's billows when driven by the force of a hurricane against a rock-bound coast, ^ Coan, American Journal of Science, 1853, xv. 6.3. 2 H. Kinney, American Journal of Science, 1852, xiv. 257, from the "Pacific" of San Francisco of June 19, the letter dated Waiohinu, Hawaii, April 19, 1852. 188 VOLCANIC PHENOMENA or like the deafening roar of Niagara." This description at- tests to the fountain-like character of the discharge ; for such sounds do not come from flowing lavas unattended by earth- quake phenomena. Mr. Kinney made the height of the jets four to eight hundred feet. He reports also that the heat created terrific whirlwinds which stalked about like so many sentinels, bidding defiance to the daring visitor. Mr. Fuller states^ that from careful calculations, made *' after deliberate discussion with Mr. Kinney," " some of which," he says, " have been confirmed by a somewhat ac- curate measurement by Mr. Lyman of Hilo," the diameter of the crater from which the fountain rose was about a thou- sand feet ; height of the crater, a hundred to a hundred and fifty feet ; height of the fountain, two to seven hundred feet, and rarely below three hundred feet ; diameter of the foun- tain, one to three hundred feet, " and rarely perhaps reaching four hundred feet." The jet of fire sometimes shot up into a tapering gothic spire of seven hundred feet, then rose in a grand mass three hundred feet in diameter, but varied at top with points and jets like the ornaments of gothic architecture. He adds that to appreciate the most terrific element in the sublime composition you should stand at the foot of a Niagara, or on a tempest-lashed shore ; for " the force neces- sary to raise two hundred thousand to five himdred thousand tons of lava at once into the air would not be silent in its operations." The lava-stream is stated to have a depth, in some places, of two or three hundred feet. Mr. E. P. Baker states that on the route from Ainapo to the source of the outflow of 1852, the lavas of the 1852 stream, where they were first reached, were of the aa kind ; but after a while there was a change to pahoehoe, and soon after this the source was reached, — a red cone in the midst of an extensive bed of pumice. Long ditches or trenches 1 Fuller, American Journal of Science, 1852, xiv. 258, letter dated Waiohinu, March 28. IN THE HISTORY OF MOUNT LOA. 189 occur in the surface of the region, wliich were evidently the beds of lava-streams, their sides having been the banks. The flow appears to have had a single outlet. Water boiled at the source at 200° F.^ 1855, Great Eruption commencing August 11. — Dur- ing the evening of August 11 a glowing point of light was seen at a height of twelve thousand feet on the northeast slope of the mountain.^ The light rapidly extended, and it soon became evident that a lava-stream was on its way down the mountain. No earthquake had announced the eruption. Mr. Coan ascertained, through his excursions, that a line of fissures extended from near the summit for " five miles " down the northeast side to the place of outbreak, along which there were cones of volcanic scoria and sand, a hundred feet or so liigh, that had been thrown up at the points of greatest activity. Descending the mountain the cones became lower and less frequent, and were the ragged jaws of orifices throuQ:h which the stream of lava was visible. The place of outflow was a crater formed over a fissure two to thirty yards wide. The lava flowed in a continuous stream down slopes of all angles from less than one degree to verticality. The course was eastward like that of 1852, and it finally stopped within five miles of Hilo. Mr. Coan describes the tunnels in the lava-stream, and speaks of the lavas seen through openings as moving with great velocity, — " estimated to be forty miles an hour." Some of the steaming openings were thirty to two hundred feet long, and the flowing lavas were fifty to a hundred feet below. But the progress of the front of the stream, where were obstructions of trees, jungles, depressions, etc., was 1 Baker, American Journal of Science, 1889, xxxvii. 53. 2 Coan, American Journal of Science, 1856, 2cl series, xxi. 139, 144, letters of Sept. 27 and Oct. 15, 1855; Ibid., p. 237, letter of Nov. 15, 1855; Ibid., xxii. 240, letter of March 7, 1856 ; Ibid., 1857, xxiii. 435, letter of Oct. 22, 1856 ; Life in Hawaii, p. 289. 190 VOLCANIC PHENOMENA " slow — say one mile a week/' He observes that owing to the cooling, and the partial damming thereby along the front, the hardened upper stratum was raised by the descending stream into numerous tumuli of various forms and sizes as if by pressure from above, which became cones or domes, and let out lavas to flow over the surface and add to the thick- ness ; that '' upgushings" also occurred through fissures ; and that thus layer was added to layer, increasing the thickness from a few feet to fifty or a hundred, and also retarding the progress of the stream. One dome on the stream was a hundred feet high and three iiundred feet in diameter ; and through the fissured top and sides the liquid lavas were visible, and easily reached by the pole he had for measuring the thickness of the cap, — two to five feet. These effects were especially great where the slope was very small. Pres- sure of the lavas above, and gases or vapors from the burning of trees and other vegetable matter l^uried by the lavas, are made the causes of the uneven surface of the lava-stream. The stream, in addition, became widened by the lateral out-gushimi-s, divided into a number of channels, and shifted to the right or left. After flowing freely for a while, the stream often suddenly cooled and hardened along the front and remained for several days inactive ; "' at length, immense areas of the solidified lava, four, five, or six miles above the extremity, are again in motion, cones are uncapped, domes crack, hills and ridges of scoria move, and great slabs of lava are raised vertically or tilted in every direction." On the 22d of October, 1856, the stream was within five miles of the sea-coast north of Hilo, still pushing out and spreading itself. Mr. Coan says that the lavas were even then flowing in the tunnel-ways from the place of outbreak to the lower extremity, although no fires were seen, — evi- dently an opinion rather than a direct observation. He argues for the absence of fissures beneath the stream for the supply of lava, from the absence of steaming vents and cones. IN THE HISTORY OF MOUNT LOA. 191 After fifteen months, in November, the fires ceased action. The stream includes many square miles of aa and immense fields of pahoehoe. 1859, Great Eruption commencing Januaey 23. — Prof. R. C. Haskell (of a party to the place of eruption including also Professor Alexander and President Beckwith) reports^ that on the 23d ''smoke" was seen over the summit from Waimea by Mr. Lyons of that place. In the evening lavas were ejected, and the light was bright enough at Hilo, thirty- five miles east, to read Hue print. '' No earthquake was felt in any part of the island." But dead fish, apparently par- boiled, were found in the sea to the northwestward, both east of Molokai and between Molokai and Oahu. The stream flowed northwestward by the foot of Hualalai, " turning just enough northward to fetch by the northeastern flank of this mountain," and reached the sea on the 31st of January at Wainanalii, a dozen miles south of Kawaihae, a distance in all of thirty-three miles in eight days. The chief source was probably about 10,500 feet above the sea-level. Above this point, for four miles, a fissure, two inches to two feet wide, descends the mountain, from which some lavas escaped. Several cinder-cones stand along the line of fis- sures, and two of them near its extremity. Half a mile farther down the outflow began. The lavas, "white hot" as they escaped, were thrown at once, as at the 1852 eruption, into a fountain, the height of which, according to Mr. Vaudrey, who happened to be on the mountain at the outbreak, was three or four hundred feet. On the 9th of February the issuing lavas were '' at a white 1 Haskell, American Journal of Science, 1859, xxviii. 66, 284 (the latter from letter of June 22) ; 1860, xxix. 301, letter of November 5. There are shorter reports by the Editor of the "Commercial Advertiser" of Oahu, and Eev. L. Lyons, Ibid., 1859, xxvii. 412 ; and Coan, Ibid., xxvii. 415, letter of Feb. 2, 1859, and xxix. 302, letter of Nov. 25, 1859. W. L. Green, Vestiges of the Molten Globe, 1887, pp. 163, 270, 280. 192 VOLCANIC php:nomena heat and apparently as liquid as water." The report says that the stream below dashed along in cataracts and rapids at such a rate that " the eye could scarcely follow it." For eight to ten miles there was a succession of cascades and rapids, some of them a consequence of obstructions met on tlie way and others due to the obstructions which the stream made. The lava flowed more gracefully than water and with great velocity, following the surface beneath, rising as it rose, and turning abruptly, with the outside of the stream higher than the inside, the mobility being perfect. Both pahoehoe and cm were formed. The aa portions are described by Professor Haskell as produced by deep lava- streams, — streams flowing sluggishly where the slopes are small, which become dammed up in front by the cooling, by the breaking up of the cooled barrier and crust, and by the rolling over and over of the stream. Often at the end of the aa stream no liquid lava could be seen, and the only motion was the rolling;; of the iag^sfed rocks of all sizes down the front O J CO of the embankment. Sometimes it broke through the em- bankment, and flowed on, '^ carrying jagged rocks of all sizes on its back, which looked like hills walking ; " then it became clogged again, with finally a repetition of the process of breaking up and piling. The stream, after reaching the seashore, continued flowing into the sea till after the 25th of November. The surface of the stream was of black hardened lavas ; but at the sea- border the liquid lavas ran out at a red heat, having flowed under cover. Professor Haskell states, for at least twenty-five miles, if not from the source. According to Mr. W. L. Green, the column of vapor that rose from the orifice or crater, alongside of which his tent was pitched, was five hundred feet wide and ten thousand feet high. He says : "• From the whole interior of this crater rose the great illuminated column of smoke perpendicularly, and then at a great height in the atmosphere it spread out on IN THE HISTORY OF MOUNT LOA. 193 all sides." It continued for many weeks, but ceased before the flow was ended. Tlie lava appeared to have broken out at the intersection of two fissures. Over the surface in the vicinity there was a thick deposit of " pumice " or *•' glass- foam." The top of the mountain at the time was covered with snow, — a source of percolating water. While Mr. Green was near the stream, on the plain between Loa, Kea, and Hualalai, " loud explosions were heard all night long, like the reports of heavy cannon." Mr. Green also states, from his observations, that at the seashore the lava ran over a low shelf about ten feet high and five or six hundred feet wide, and fell into the sea where the water was twenty or thirty feet deep. " It came from under the crust in great red-hot flattened spheroidal masses, having something the appearance of moderately thick por- ridge as it is poured from a saucepan, — the spheroidal masses perhaps ten to fifteen feet wide and four to six feet deep. . . . There was no steam, vapor^ or gas whatever to be seen coming from the lava until it went under water. Indeed, the first contact of the red-hot spheroids did not seem to pro- duce a particle of steam, and it was only when each had gone under water and become partially cooled off that a puff of steam rose above the water, . . . an effect due to the sphe- roidal state of the water against the red-hot surface." No sympathy was exhibited by Kilauea. Mr. Coan says : '' We have occasional earthquakes, — two in February, one in July, and two in November of the current year (1859)." In June, according to Professor Haskell, there was no action in the summit crater. 1864, August 5. — Mr. W. T. Brigham found the sunnnit crater, at this date,^ without any signs of action excepting some " steam issuing from the northern bank." There were two cones at bottom, about two hundred feet high, near the 1 Memoir, p. 384. 25 194 VOLCANIC PHENOMENA east side. He also observes that in various places over the great plain about the crater there ^' were large irregular masses of a solid reddish clinkstone, much used for stone axes," and speaks of the " hard compact graystone of the summit and walls." \^Qb,' December 30. — Light, says Mr. Coan, was seen "at the very summit," on the night of the SOtli of December.^ It continued, with variations in intensity, sometimes very brilliant, at others faint or gone, for four months, or until the last of April, or perhaps into May. Mr. Richardson, propri- etor of the Volcano House, reported tlie occasional escape of steam, but no outflow of lava is known to have occurred. " The falls of snow on the mountains this winter have been frequent and heavy, extending almost to their bases." No earthquakes were reported. "As it was winter, no one ascended the mountain." In May a great increase of ac- tivity began in Kilauea. 1868, Great Eruption commencing in Earthquakes, March 27. — On March 27, Friday, many slight earthquakes were felt in Kau, southern Hawaii, and in Kona, the south- western district. On the 28th they were more energetic and frequent, and extended east to Hilo, and northward through Kona. Mr. T. D. Paris, of Kealakekua, South Kona, reports^ that on the morning of Friday fire and great columns of " smoke " were seen at the summit ; and on Saturday the 28th the fires were visible from Hilo, according to Mr. Coan.^ Mr- F. S. Lyman reports, from Kau, that the first outbreak was a little to the southwest of the summit ; that others fol- lowed, and soon the lavas were seen in four streams running down the mountain in a southerly and easterly direction. ^ Coan, American Journal of Science, 1866, 2d series, xli. 424, letter of Feb. 27, 1866; and xliii. 264, 1867, letter of August 31, 1866. ^ Paris, American Journal of Science, 1868, 2d series, xlvi. 107. 8 Coan, Ibid., p. 106 ; F. S. Lyman, Ibid., p. 109; H. M. Wliitney, Ibid., p. 112. IN THE HISTORY OF MOUNT LOA. 195 By Sunday (the oOth) the line of smoke had advanced about fifteen miles on a line toward Captain Brown's house in Kahuku. (See southern part of map of Hawaii.) But the light of the summit had disappeared ; it was not seen at Hilo after the 28th. During this time, however, the earthquakes became still more violent and destructive, and almost continuous. On Thursday, April 2, at four p. m., occurred '' the terrible shock," destroying houses and life, making fissures of great length and depth, dislodging rocks, and half a mile in breadth of marshy earth from the mountain side of Kapapala, to the destruction of a native village, besides raising earthquake waves on the southern coast, that swept away the villages of Punaluu, Ninole, Kawaa, and Honuapo. The position of the land-slide is shown on tlie map of Hawaii (Plate I.). It was also violent to the eastward in Hilo, the only stone building being thrown down, and furniture in other houses ; but so light on Oahu, two hundred miles to the westward, that most of the inhabitants of Honolulu were unaware of it, those in stone houses being almost the only persons that felt it. On the Tth of April the lava escaped from a wide fissure in the district of Kahuku, ahout fifty-six hundred feet above the sea-level. Along the fissure, in the course of a mile, the escaping lavas were thrown into four fountains, which were playing on the lOtli, when the place was visited by Mr. H. M. Whitney, of Honolulu. According to this writer's descrip- tion, the fountains rose to a height of five to six hundred feet, along the line of the fissure for a mile. The lavas were "blood-red, yet as fluid as water." Sometimes two of the fountains joined, and then all four were united. At one time they subsided for a few minutes, and then burst out again and went to a height of a thousand feet. Large stones and rocks were thrown up. some weighing a hundred tons ; and so many that they seemed to fill the air. The lava of the fountains is stated to have had a rotation " to the south." 196 VOLCANIC PHENOMENA Below the fountains the lava flowed in a rapid stream to the sea, making a descent of two thousand feet, and reaching the shore in two hours. The rate of flow is stated to have been ten to twenty-five miles an hour.^ A cinder or tufa cone was made at tlie place of discharge into the sea, which was first an island, and afterward became joined to the land by the flowing lava. The eruption ceased in the night between the 11th and 12th, after only five days' activity. The lava is mostly pahoehoe, with some areas of aa, and extremely chryso- litic. At the crack above the main outburst, the lava which escaped was light l^rownish scoria, which was drifted by the winds, along with much capillary glass. The season was one of unusual rains over the mountain. Prof. C. H. Hitchcock examined the region of eruption in June of 1885, both above and below the extremity of thp pali (precipice) represented on the map (Plate I.) as running along Ijy the west side of the lava-stream. He states the following facts to the author in a letter of May 30, 1888 : The fissure whence the lavas of 1868 flowed, is in exact continuation of the pali, up the mountain. I traced it fully three miles. For much of the way it makes a narrow cafion forty to fifty feet wide at the maximum, and so deep that it is dangerous to explore it. In the lower part heat was still evident. The fissure is most prominent where the lava is in greatest amount. Its borders have the smoothed appearance that would result from an outflow of lava over its edge. The very uppermost point reached we estimated, from our aneroid, to Idc thirty-one hundred feet above Mr. Jones's ranch near the north end of the pali. There is no cone at tliat point, as there is at the sources of the 1855 and 1881 tiows which I also visited. Every fact harmonizes with the ' Pacific Commercial Advertiser of May 9, 1868. See also W. L. Green's Vestiges of the Molten Globe, pp. 294-303. Mr. Green does not intimate that Mr. Whitney's description is exaggerated. According to Rev. E. P. Baker, the highest fountain, on the estimate of an observer, Mr. Swain, was not over two hun- dred feet. IN THE HISTORY OF MOUNT LOA. 197 view of a rent three miles long, allowing the accumulated lava to discharg-e in one or two davs' time, instead of oozino; out of a single small orifice for months. The connection of the fissure with the pali shows clearly the existence of a fis- sure along its whole length, which has been the seat of erup- tions in ages past. This Kahuku flow was analogous to that of Kilauea in 1840. 2. Eruptions of Mount Loa from 18G8 to 1890. 1870, Januarii 1. — During the first two weeks of January much " steam and smoke " arose from the summit crater.^ In the course of the preceding month Judge Hitchcock, of Hilo, with others, visited the crater, and found much escap- ing steam but no visible fires. Slight shocks of earthquakes often occurred, sometimes one, two, or three a day. 1870. — Mr. Severance (as I learned from Rev. E. P. Baker, of Hilo) was at the summit crater in 1870, and found no action there. 1872, August 10. — On the night of the 10th of August, says Mr. Coan,^ " a lofty pillar of light," two thousand feet high, — which means lighted vapors of this height, — stood over the sunnnit crater, with varying brilliancy, indicating active fires within. The crater was '' in full blast on the 27th," and continued so into September. On the 23d of August a tidal wave was felt on the coast at Hilo, the wa- ters during a calm rising four feet, and in a second wave, six minutes later, three feet, and diminishing for about four- teen oscillations. It may have been part of the Mount Loa disturbance ; but Kilauea also was unusually active over its Ulterior. No earthquake is reported. ^ Coan, American Journal of Science, 1870, xlix. 393, letter of Jan. 24, 1870, 2 Ibid., 1872, 3d series, iv. 406, letter of August 27, 1872, and 1873, v. 476, letter of Feb. 14, 1873. 198 VOLCANIC PHENOMENA The "Pacific Commercial Advertiser," of September 21,^ reports an ascent to tlie summit made just before this date. Near the southwest corner of the crater tliere was a foun- tain of lava about seventy-five feet m diameter, playing, it is stated, to a height of five hundred feet. The basin from whicli it rose covered about a third of the bottom, and was at the top of a low cone made by the falling lavas. Mr. J. M. Lydgate has informed me that he was at the crater in the latter part of August, and that the fountain was then in play. 1873, January 6 aiid 7. — On the 6th of January the action at the summit, as seen from Hilo, was " marvellously brilliant," the lighted vapors visible at night rising thousands of feet above the summit.^ There was evidence, apparently, of active ebullition or a playing fountain ; and this conclu- sion is favored by the fact that the herdsmen of Reed and Richardson's ranch, at Ainapo, on the eastern slope (forty- two hundred feet above the sea), stated that the mountain was •' constantly quivering, like a boiling pot." The action suddenly ceased, without any known outflow ; the time of ending the display is not mentioned. Kilauea had been very active for months. No earthquake is spoken of, and no sym- pathy with Kilauea implied. 1873, 1874. Brilliant Summit Displays from April 20, 1873, to the Autumn of 1874. — The summit display of Jan- uary was followed, on April 20, three months later, by a return to activity, or to a degree of activity that was visible from Hilo. Mr. Coan observes that the lofty columns of light above the summit at night and of clouds by day were proof of violent ebullition within the crater. 1 Coan, American Journal of Science, 1872, iv. 331, and 407, 408. 2 Ibid., 1873, V. 476, letter of Feb. 14, 1873 ; 1874, vii. 516 ; 1877, xiv. 68. In the first of these notices the date given is January 27 ; in the others, January 6 and 7. IN THE HISTORY OF MOUNT LOA. 199 On the 6th of January, 1874, Mr. Coan writes^ that for nine months the action within the great crater has not re- mitted. "The great marvel is its duration," without any out- side results. There appears to have been a turn of sjDecial brilliancy in January. On the following October (the 6th) he says ^ the action has continued " for eighteen months, and the most of the time it has been violent. But of late it has become more quiet, and there is a prospect that it will soon cease." He adds : " We have had few earthquakes during the year, and these have been feeble. . . . Kilauea all this time was unusually active ; " but no sympathy with Mount Loa was observed. It is of great importance to the history that we have trust- worthy rejDorts with regard to the condition of the interior of the summit crater on three of the days during this era of prolonged activity. And as the first of the three — the 6th of June, 1873 — was a day of feeble summit light as seen from below, it affords data for an estimate of its condition dur- ing times of greater brilliancy. The explorer, Miss Bird,^ was at the summit on the 6th of June, and describes well the condition of the crater. For the most part its floor was an area of solid black lava ; but at one end (the south- west ?) there was " a fountain of yellow fire," one hundred and fifty feet broad, which played in several united but independent jets to a height of one hundred and fifty to three hundred feet. The party for the two days preceding had been under the impression that the fires had faded out ; and yet this fire-fountain was all the time in action. When within two miles of the crater, monitions of the activity were apparent in a distant vibrating roar; and on reaching the cra- ter edge, the roar was like that of an ocean, rising and falling ^ Coan, American Journal of Science, 1874, vii. 516, letter of Jan. 6, 1874. 2 Ibid., 1874, viii. 467, letter of Oct. 6, 1874 ; and 1877, xiv. 68, letter of March 17, 1877. ^ Six Months in the Sandwich Islands, by Isabella L. Bird, London, 1876, pp. 266-273. 200 VOLCANIC PHENOMENA '' like the thunder-music of windward Hawaii," — a compari- son used also by Mr. Kinney in describing the eruption of 1852. At night the lake was for the most part at white heat, and its surface v/as agitated with waves of white-hot lava about the fountain at the centre. Through the rest of the vast crater the projecting ledges were thrown into bold relief by the reflected light, and by numerous dashes and lines of fire from apertures and crevices. Occasional detona- tions were heard, but no shakings except the tremors from the throw and fall of the lavas. At one time the jets, after long playing at a height of three hundred feet, suddenly be- came quite low, and for a few seconds there were " cones of fire wallowing in a sea of light," — a description that not only reads well, but I feel sure is to the life, like the most of Miss Bird's word-pictures ; then, " with a roar like the sound of gathering waters, nearly the whole surface of the lake was lifted up, by the action of some powerful internal force, and its whole radiant mass rose tliree times in one glorious up- ward burst, to a height, as estimated by the surrounding cliffs, of six hundred feet. . . . After this the fountain played as before." "' Tn one place heavy white vapor blew off pow- erful jets from the edge of the lake, and elsewhere there were frequent jets and ebullitions of the same ; but there was not a trace of vapor over the burning lake itself." In " The Vestiges of the Molten Globe " (p. 166), Mr. W. L. Green, with whom Miss Bird made her ascent, gives confirmatory facts. He makes the height of the fountain generally three to four hundred feet, as estimated from the known depth of the crater ; and occasionally some spires shot up, he observes, to a greater altitude. He adds : "• Among the varied forms of the fountain there were the low rounded dome ; a spire at centre, with a fountain either side in the form of a wheat- sheaf ; and one great wheat- sheaf." Besides a dull roar, there was " the metallic clink " from the fall of masses of lava of the fountain which were IN THE HISTORY OF MOUNT LOA. 201 cooled in the air; these cooled fragments formed a light falling veil over the dazzling fountain, and descending into the lake outside of the jets, made a scum over its surface. Only a light vapor was seen over the playing fountain. Early in August, 1873, Dr. 0. B. Adams ascended Mount Loa, at a time when the light at the summit was unusually brilliant. He found the fountain playing, he says, to a height of two to five hundred feet, and " assuming all the forms of a grand fountain of water." ^ In October, 1873, Messrs. E. G. and H. R. Hitchcock spent one night at the summit near the site of Wilkes's camp, on the east side of the central crater or pit. They state that a fountain of lava was playing in the southwestern end of the crater, to a height of six hundred feet, this height being obtained by lying upon the brink and looking across the pit to the top of the opposite wall ; •' the column of fire ascended at least one half higher than the distance from the floor to the top of the walls, and taking this distance at four hundred feet, the height of the fountain was de- cided to be approximately six hundred feet." The descend- ing lava of the fountain, falling into the basin, flowed off northward nearly the whole length of the western side of the pit.^ 1875, January. — Mr. W. L. Green mentions the occur- rence of summit action at this time for a month, in his tabular statement of eruptions, and says nothing of one in August of this year, to which date Mr. Coan refers the 1875 eruption. The report of the " Challenger," mentioned beyond, sustains Mr. Coan's statement, but does not positively set aside that of Mr. Green. 1 Hawaiian Gazette, Sept. 3, 1873. * Letter of W. C. Merritt, in American Journal of Science, 1889, xxxvii. 51. 26 202 VOLCANIC PHENOMENA 1S76, August. — Mr. Coan says : ^ "I think it was on the 11th of August that the summit crater was again in bril- liant action. The action continued, as appeared in the view from Hilo, for one week, and without any observed evidence of an outflow." In the first half of August, the day not stated, a party from the " Challenger " Expedition visited Kilauea. As reported in the first volume of the '' Scientific Results of the Expedi- tion" (p. 766), "a globular cloud" was seen over the summit of Mount Loa, which was '• perpetually re-formed by con- densation," and had " a brilliant orange glow at night, look- ing as if a fire were raging in the distance."^ 1876, February 13. — Another grand display from the sum- rait crater, but of short duration. No outflow is reported.^ 1877. Probable Submarine Eruption, February 14. — The display of light on the 14th, says Mr. Coan,* was " most glorious." The columns of illuminated steam rose " with fearful speed to a height of fourteen to seventeen thousand feet, and then spread out into a vast fiery cloud, looking at night as if the heavens were on fire." The brilliancy con- tinued only ten days. No outflow is positively known to have occurred, but it is probable that a submarine discharge took place off western Hawaii. The steamer brought passengers from Honolulu to visit the mountain, but returned as the fire had disappeared. But before the vessel was fairly out of sight of land, " a re- markable bubbling was seen in the sea about three miles south of Kealakekua, a mile from the shore," and steam and scoria were thrown up. Mr. H. M. Whitney states that 1 Coan, American Journal of Science, 1877, xiv. 68, letter of March 17, 1877. ^ See also Moseley's Notes by a Naturalist of the " Challenger," London, 1879, p. 500. ' Coan, American Journal of Science, 1877, xiv. 68, letter of March 17, 1877. * Ibid. IN THE HISTORY OF MOUNT LOA. 203 ^^ blocks of lava two feet square came up from below, strik- ing and jarring the boats ; " and " nearly all the pieces on reaching the surface were red-hot ; ... as soon as they became cold they sank." This eruption took place on the 24th of February, the day the light disappeared from the summit.^ On the land new fissures were opened in the mountain which had a westward course toward the place of submarine disturbance. An earthquake is reported as having been felt in the fissured region, but not at Kealakekua. A heavy tidal or earthquake wave occurred about this time along the coast of Kona." 188U, May 1. — Early in the morning of May 1 a light was seen at or near the summit, which soon after became so intense as to illuminate Hilo at night. It indicated vio- lent activity, and led to an expectation of a great eruption. But clouds obscured the mountain for a few days, and when they disappeared, the light was gone.'^ On the 3d and 4th of May flocks of Pele's hair and light particles of volcanic dust, drifted by the wind, fell over Hilo. According to reports from Puna and Kau, the action had not ceased by May 6. Mr. Brigham states* that his guide was at the summit at the time, and saw boiling lava in the south crater ; and that the tops of the jets were visible to the native while he was lying down some distance from the brink, — which would make the height of the jets, Mr. Brigham says, one thou- sand feet. As the depth of the crater was not over eight hn.ndred feet, his estimate is probably too high. Mr. Good- ale, one of the party who ascended at that time, reported, as 1 Hawaiian Gazette, Feb. 28, 1877. ^ On the 10th of May, 1877, a destructive earthquake wave was felt at the Hawaiian Islands, which rose at Hilo to a height of thirty-six feet. But it was of South American origin, where there were heavy earth-shocks, aud not of Hawaiian. ^ Ooan, American Journal of Science, xx. 7, letter of May 3-6, 1880. * Brigham, American Journal of Science, 1888, xxxvi. 33. 204 VOLCANIC PHENOMENA mentioned in a letter from Mr. E. P. Baker, that the lavas were thrown sixty or eighty feet above tlie brink of the crater on which the party were standing ; and this confirms the re- port of the native guide. 1880. July 28. — On the 28th of July Mr. W. T. Brigham found the crater without action.^ The walls were much fis- sured about the southern pit ; fresh-looking lavas covered the bottom ; and a small area was seen on the west border of the pit, which was probably of recent ejection. Moreover, about the region around the crater there was much of the spongy scoria, some masses a foot in diameter. 1880, 1881. Great Eruption from Nov. 5, 1880, to Aug. 10, 1881, Nine Months. — No "violent demonstrations or earthquake" announced the eruption. The first light was visible in the evening of Friday from Waimea, and a few hours later in the night from Hilo, and after midnight " the lavas could be distinctly seen leaping like a fountain into the air." The next day a line of light extended down the slopes toward Mount Kea, from a point about eleven thousand one hun- dred feet above the sea.^ Near the same time another stream flowed from the source southeastward into Kau, and soon after the lavas commenced a third stream toward Hilo, be- tween those of 1852 and 1855. The Kea stream stopped on the intermont plateau east of Kalaieha, having a length of ten to twelve miles ; and the Kau stream reached nearly the same length. The Hilo, as the map shows, came near giving Hilo a burial. As observed by Judge Hitchcock^ on the 10th or 11th, from the Kalaieha Hills at the south foot of Mount Kea, the stream, for miles northward to the plain, was * Brigham, American Journal of Science, 1868, xxxvi. 33. 2 Coan, Hitchcock, Ibid., 1881, xxi. 79, letter of Nov. 9-12, 1880; xxii. 227, 228, letter of June 28 and July 2!, 1881, and xxii. 322, letter of August 24, 1881 ; Life in Hawaii, p. 325. 8 Ibid., 1881, xxi. 79, and xxii. 226. IN THE HISTORY OF MOUNT LOA. 205 a continuous belt of fire in steady flow, and also beyond this for several miles toward Hilo. The regular flow was inter- rupted half-way from the plain to the source by the lavas rising into a huge dome, from which they flowed over like an immense fountain ; but there was no fountain at the source. Mr. E. S. Baker states,^ after an examination of the region a second or third time, in July, 1888, that the Kea and Kau streams oris-inated together from the same source, at the extremity of a long fissure where there is now a large pit crater, called Puka Uahi, as shown at S, in the annexed figure ; and that the divergence of the Kau stream from the Kea and also from the Hilo stream was owing to the fact that the fissure followed the course of a " divide," so that a small obstacle was sufiicient to turn the flow to one side or the other. The outflow took place on this divide ; the Kau stream went off first from the fissure, or at least started off from it higher up, the Kea stream next, and the Hilo from a still lower point. The fissure ran by the north side of Red Hill, a cone with a deep crater which was still giving out vapors, and this hill was apparently the occasion of the turn southward of the Kau stream, it standing at the point of their divergence. This Kau stream is in general aa, but near the source, in a most quiet, unobtrusive way, the aa changes into pahoehoe. Near the head of the Kau stream there is a cinder-cone, named '^ Little Vesuvius " (at V on the map). This cone and the pit-crater were also steaming, although seven years had elapsed since the end of the eruption. ^ Baker, letter to the author, and also American Journal of Science, 1889, xxxvii. 53. 206 VOLCANIC PHENOMENA The thickness of the stream in its lower part, as deter- mined by the depth of the holes left where trees had been burned off, was found by Mr. Baker to be in two such places twelve and eighteen feet. In four months the stream was within seven miles of Hilo, or about twenty-six miles long; in seven and tw^o thirds months, June 28, within five miles ; in eight and one half months, July 18, about two miles ; and August 10, nine months after the outflow began, it stopped within three fourths of a mile of Hilo. On June 30, the movement just beyond the Hilo tufa-hills (the Halai Hills) was, as stated by Mr. D. H. Hitchcock, about seventy-five feet an hour. On its w^ay, says Mr. Ernest E. Lyman, " the lava-stream came in contact with a stream of water, flowed into, blocked, and turned it out of its course. The steam form- ing under it caused frequent explosions. I saw it pass over a water-fall. At first the water cooled the lava suf- ficiently to make it brittle, and it fell over in chunks till it had formed a pile as high as the fall ; and then it flowed over, forming a flume of lava. It was a wonderful sight to see the water and the liquid lava flowing side by side." ^ Plate XI. represents another cascade in the same stream, two and a half miles above Hilo, and about half a mile below that described by Mr. Lyman. In a communication to the " Commercial Advertiser " for November 20,^ the formation of the aa or clinker fields is described as follows by Judge Hitchcock : " The whole broad front of the then sluggish stream was a mass of so- lidified lava twelve to thirty feet in height, moving slowly along by breaking and bearing onward the crusted cover- ing ; along the whole line of its advance it was one crash ^ E. E. Lyman, communicated by President Merritt, in July, 1889. ^ Hitchcock, American Journal of Science, 1881, xxii. 228, from the "Com- mercial Advertiser" of Honohihi. IN THE HISTORY OF MOUNT LOA. 209 of rolling, sliding, tumbling, red-hot rock, no liquid rock being in sight ; there were no explosions, but a tremendous roaring, like ten thousand blast-furnaces all at work at once. The rough blocks lie piled together in the wildest confusion, many as large as ordinary houses. They [clinker- fields] form only when the movement is slow." While at Hilo in August, 1887, the author, under the guidance of Rev. E. S. Baker, of Hilo, visited the cooled lava-stream of 1880-1881, and its tunnel. The ropy twisted lines and tapestry folds cover much of the surface ; and some are on a most delicate scale, the tapestry hangings (like that of page 117) only an inch wide, and varying from this diminutive size on one extreme to a breadth of six or eight feet. Three or four miles from Hilo the lava-stream, which had consisted of pahoehoe, became rather abruptly an aa stream. At the junction the pahoehoe was very much broken, as if by an intermittent flow in the stream. The cavern, or rather tunnel, of the stream had very smooth sides, and in part a literally glazed surface, indicat- ing the flow of the lava ; and thore were long parallel lines of mouldings^ due to the same cause. One of the lines of mouldings had the form and position, along the side of the tunnel, of a solid, handsomely modelled bench, showing that the mouldings were due to projecting points and larger pro- tuberances of the solid lava outside. The tunnel had a varying height of four to eight feet, but in some portions diminished to two feet, and in others rose to ten feet. The general width was about thirty feet ; but there were large lateral expansions. The layer of rock above was two to six feet thick. In some undisturbed parts of the tunnel there were thick- ets of long, slender, grayish-black stalactites, like pipe-stems in size, scarcely tapering at all except at the extremity where there is usually a short irregular twist (Plate XV.). Where most crowded they were twenty to thirty inches or 27 210 VOLCANIC PHENOMENA more long, and one every six or eight inches. Over the floor beneath eacii there was an irregular column of stalagmite of similar nature, consisting of a heap of bent, coalescing stems, of the same diameter, varying from a few inches to hfteen or eighteen in height. The stalactites were solid for the most of their length ; but still many parts were hollow cylinders. A pocket lens was sufficient to show, after emerging again to daylight, that the texture of the stalactite was stony, like the lava, and contained similarly minute crystals of feldspar, which were lath-shaped on a surface of fracture; and that the cavities were lined with glassy crystals and magnetite. I am informed by Mr. Baker, in a letter dated Hilo, July 3, 1889, that at one place in the tunnel, where the stalactites were only two or three inches long, their bent extremities were all turned one way, and that was toward a blow-hole entrance to the tunnel, — favoring the view, as he says, that a draught from the interior outward had determined the bending. 1882. — In this year (the month not stated) Capt. C. E. Button made his visit to the summit.^ He found " no vol- canic action whatever, . . . not even a wisp of steam issuing from any point." No mention is made of any cinder-cone at the bottom. 1883, February. — Prof. C. H. Hitchcock was at the sum- mit on the 15th, and found no activity. " A snow-squall struck us, and the entire floor of the crater was ivhite with snow. 1885, ^pn7. — In April, 1885, Rev. E. P. Baker visited the crater and descended to its bottom. It was all quiet. 1 Eeport, p. 139. 2 Letter to the author of May 30, 1 888. IN THE HISTORY OF MOUNT LOA. 211 1885, October. — In October, 1885, Rev. J. M. Alexander made a survey of the summit crater for the Government Sur- vey.^ The bottom of the crater was mainly flat, and covered with fresh lavas ; it had two cones in it, as represented on the map, the southwestern a hundred and forty feet high and smoking ; steam was rising from " hundreds of cracks," but no fires were visible. In the depressed area or terrace to, the north of the central or main pit a circular pit-crater was found, as shown on the map, which was six hundred feet deep and a thousand feet wide, and had a cone at centre that was still smoking. Near the junction of the central pit with the south crater there had been an eruption from fissures that were still steaming, from which a great stream had flowed southwestward in the Kahuku direction ; the lava had also poured down in cataracts into the south crater. Mr. Alex- ander observed about the summit for a breadth of a fourth of a mile from the crater many blocks, from fifty pounds to a ton in weight, of a "• solid, flinty lavao" The dimen- sions of the crater obtained by Mr. Alexander are stated on the map (Plate X.). 1887. Gee AT Ekuption in January and February, ATTENDED BY EARTHQUAKES. — In December, 1886, earth- quakes became frequent in southwestern Hawaii. By the 12th of January the shocks averaged three a day. Between twelve minutes past two o'clock on the morning of January 17 and four o'clock on the morning of the 18th, 314 shocks were counted by Mr. George Jones in Kahuku, sixty-seven between the latter date and midnight, and three the follow- ing day. In Hilea, ten miles west, 618 were counted between two o'clock on the morning of the 16th and seven o'clock on the evening of the 18th. On the night of the 16th, with the sudden increase in the/ ^ Alexander, American Journal of Science, 1888, xxxvi. 35. 212 VOLCANIC PHENOMENA earthquakes, fires broke out at the summit near the small crater south of the summit crater, Pohaku o Hanalei (Plate I.), and in a few hours disappeared. The height of this first out- break, according to Mr. E. P. Baker, was eleven thousand five hundred feet. On the 18th, at seven o'clock in the morning, — three hours after the cessation of the earth- quakes, — an outbreak took place in Kau, north of Kahuku. The lavas came from a fissure about sixty-five hundred feet above the sea-level and twenty miles from the sea, and reached the sea at noon on the 19th, nearly four miles west of the flow of 1868. It extended the shore outward three to five hun- dred feet without making a cinder-cone on the sea-border. By noon of the 24th the flow had stopped, but the fires were still active along the stream. At the outburst, as at the Kahuku eruption of 1868, the lavas were thrown up into fountains. The fountains were about eighty feet in diameter, and eighty to a hundred or more feet in height. They were photographed ; and two of the views, representing the same part of the stream and one fountain, are shown on Plate XII. Mr. Spencer, who visited the source on the 20th, states that there were then fifteen fountains, and that the highest was two hundred feet ; others make the height not over half this amount. The stream is stated to have flowed away bearing bowlders weighing tons, with explosions at intervals. During the first twenty-four hours the rate of flow was but a mile and a half an hour, and the stream made was of aa ; afterward the flow was rapid, and the stream of pahoehoe. The earthquake in Kau threw down walls that had a northeast and southwest direction, — the throw was to the southeast ; and light wooden houses were moved eight or ten inches in the same direction or down the slope. The oscilla- tions in Hilo were reported to have been from south-southeast to north-northwest. On February 20 Mr. D. H. Hitchcock was at the summit, w ►=j .7 .'-i\ IN THE HISTORY OF MOUNT LOA. 215 and found the crater quiet, but vapors issuing from large fissures. Kilauea was moderately active during the period of erup- tion, rather increasing in activity with its progress, but without evincing special disturbance or sympathy/ In July, 1888, going from Ainapo to the source of the erup- tion of 1887, in Kahuku, about six thousand feet above the sea-level. Rev. E. P. Baker passed through regions of woods and D-rass, and saw seven runnino; streams and three or four ponds of water. There had been heavy rains. The fissure of 1887, about four hundred feet above the place of outflow, was still giving out vapors. No deep crater marked the place of discharge.^ 1887, Dccemher 29. —A letter from Mr. J. S. Emerson, dated Kohala, Hawaii, December 29, states that the view of the summit of Loa from that place indicates activity in Mount Loa. " Volumes of smoke and steam have been pouring out of the summit crater, but no glow or reflection of fire has been observed. . . . The summit is now heavily coated with snow." Another letter of April states that on March 29, 1888, the signs of activity at the summit had disappeared ; the exact time of their cessation was probably early in February. 1888, Jubj 18. — The summit was visited at this date by President W. C. Merritt and Rev. E. P. Baker." The range of the thermometer for the day was : At noon, 62° F. ; at seven o'clock in the evening, 40° F. ; at eleven o'clock at night, 30° F. ; at daybreak, 26° F. Mr. Merritt states that in the central pit of Mokuaweoweo, at bottom, a small cinder- cone was found not far from the eastern wall, and just south- 1 The above is from the " Pacific Commercial Advertiser and Hawaiian Gazette" of Honolulu ; American Journal of Science, 1887, xx.xiii. 310. 2 Baker, American Journal of Science, 1889, xxxvii. 53. 8 Ibid., 1889, xxxvii. 51, 52. 216 VOLCANIC PHENOMENA. west a pumice-cone in the midst of an cm flow, the summit of which was very hot and reddish from the action of vapors. In the southwest corner of the pit there was a cone (at F on map, Plate X.), from which vapors were escaping, and south of it, at m, a circular pit three and four hundred feet in its diameters by estimate, and a hundred and fifty to a hun- dred and seventy-five feet deep. In the walls of the pit, which consisted of the edges of layers of basaltic rock, one layer was forty to fifty feet thick, and vertically columnar in structure. The floor of the central pit had, as a. whole, a slope from the southwest to the northeast, — confirming the view that the southwest part of the pit had been the seat of greatest activ- ity, as it is in Kilauea. Southwest of m the outer wall of the central pit was cut through from top to bottom by two parallel fissures, which had a south-southwest direction, and thence pointed nearly toward the place of chief eruption of 1887. East of m, and near the wall in the direction of L, there were great numbers of small fumaroles, from which sulphur vapors were escaping freely, and large deposits of sulphur had been made about them. Near h two dikes, two to two and a half feet thick, intersected the walls, crossing one another at a small angle, the rock of which had a feld- spathic aspect. From a rough measurement the depth of the crater on the east side was made not over three hundred and fifty feet. If this small depth is sustained by careful observations, a great change of level had taken place since the survey of Mr. Alex- ander in 1885. Such a change might have been among the effects of the eruption of February, 1887. On the summit, to the south of the crater, Mr. Baker observed six parallel fissures, ten to twenty rods apart, having a course toward the place of eruption of 1887. PKOGKESSIVE CHANGES IN THE MOUNT LOA CRATER. 217 3. General Summary, with Conclusions. The subjects connected with Mount Loa and the summit crater considered in the following summary and conclusions are the following : — 1. The times and time-intervals of eruptions and of summit iUicminations or activity, with reference to (1) periodicity, (2) relations to seasons, (3) variations in activity since 1843, and (4) the changes in the depth of the crater. 2. Tlie ordinary activity ivithin the summit crater. 3. Causes of the ordinary movements wit! tin the crater. 1. Times and Time-intervals op Eruptions. Question of Periodicity. — Commencing with the eruption of 1832, there have been nine registered eruptions of Mount Loa. Their times and heights of outflow, directions and lengths of stream, and relations to earthquakes are stated in the following table : — Reported Earthquakes. Height of Chief Outflow. Direction and Length of Flow. 1. 1832, June 20, 2-.3 weeks .... None. Summit. No outflow. 2. 1843, Jan. 9 to end of Feb., U mos. . None. 11,000. N.N.W.,15m. 3. 1851, Aug. 8, for 3 or 4 days . . . None. 12,900. W., 10 m. 4. 1852, Feb. 17 into March, 20 days . None. Little over 10,000. E., 20 m. 5. 1855, Aug. 11 to Nov., 1856, 15 mos. None. 12,000. E., 26 m. 6. 1859, Jan. 23 to Nov. 25, 10 mos. . . None. 10,500. N. W., 33 m. 7. 1868, March 27, 16 days Earthquakes. 3,000. S., 10-11 m. 8. 1880, Nov. 5 to Aug., 1881, 9 mos. . None. 11,100. E., 30 m. 9. 1887, Jan. 18, 10 days Earthquakes. 6,500. S., 14 m. The intervals between these eruptions, reckoning (A) be- tween their beginnings and (B) between the end of each and the beginning of the following one, are : — 28 218 VOLCANIC ACTION. A. B Between eruptions 1 and 2 10 years 8 months. 10 years 7 months 2 and 3 8 9» 7 n 8 1 1 5i- „ 3 and 4 6^ 15 6 „ 4 and 5 3 ^, 6 J5 3 5 ,, 5 and 6 3 1 1 5 »» 2 2 ,, 6 and 7 9 11 2 ,, 8 4 ,, 7 and 8 2 ,, 7 1> 12 7 „ 8 and 9 6 ,, 2i 5» 5 6 „ The eruptions above enumerated — that of 1832, perhaps, excepted — were great eruptions ; that is, they had outside or subaerial outflows. But the history shows that at other times in the sixty-five years the summit of the mountain has been often brilliantly lighted, and surmounted with a column of clouds of great height, made apparently from the escaping vapors, which became a lofty column of light at night. These summit illuminations have been shown to be evidence on page 197, not merely of action in or about the crater, but de- cisively of a boiling or fountain-like activity in the liquid lavas, if not also of outflowing streams. The drifting of Pele's hair on such occasions thirty-five miles to Hilo is as good testimony to the playing of jets or fountains as a note from an observer at the summit. Moreover, we have learned from Kilauea that these times of brilliant action within the crater may be followed by subterranean or submarine discharges when not by sub- aerial, and therefore that they are not always merely the flaring up and fading out of the crater-fires. They announce that the toj) of the Mount Loa cohcmn of liquid lavas may he up to and in the crater, or have its maximum length and be at serious work, even when no outbreak ensues. The followino; table contains the times of these minor dis- plays, as well as those of the admitted greater eruptions. In the table the latter are indicated by italics. PROGRESSIVE CHANGES IN THE MOUNT LOA CRATER. 219 Dates. 1. 1832, June 20. 2. 1843, Jan. 9 to late in Feb., — 1^ months. 3. 1849, May, 2 to 3 weeks. 4. 1851, Aug. 8, — 3 or 4 daj/s. 5. 1852, Feb. 15 to June, — about 4 months. 6. ,1855, Aug. 11 to Nov., 1856, — 15 months. 7. 1859, Jan. 23 to Nov. 25,-10 months. 8. 1865, Dec. 30,-4 months. 9. 1868, March 27 to April 12 ; the flow 4 daijs. 10. 1872, August 10 into September. 11. 1873, Jan. 6, 7,— 2 flays. 12. 1873, April 20 to October, 1874,-18 months. 13. 1875, Aug. 11, — one week. 14. 1876, Feb. 13, —few days. 15. 1877, Feb. 14, —few clays. 16. 1880, May 1. 17. 1880, Nov. 5 to Aug., 1881,-9 months. 18. 1887, Jan. l<6,—tendaqs. 19. 1887, Nov. 25 into Feb., — one month. Couditions at the Summit. Bright light at the summit, 2-3 weeks. Clouds ; January 10-17, bright light Brilliant light, just after activity in Kiiauea. Bright light for three or four days. Brilliant light for twenty four hours. Bright light at beginning. Brilliant light at first. Brilliant light for four months, varying ; at close, Kiiauea increases its activity. Bright light from March 27 to 30. Brilliant ; a lava-fountain of 500 feet ; a tidal wave on the coast ; Kiiauea very active. Brilliant. Brilliant more or less for eighteen months ; in June and August, 1873, a lava-fountain, 300-600 feet. Brilliant. Brilliant. Brilliant ; a submarine eruption. Brilliant; a lava-fountain of 900 feet; Pele's hair fell in Hilo. Briglit for a few days. Bright for a few hours. Vapors; no liglit seen. The table contains the dates of. ten periods of summit activity or iilumination independent of the great eruptions, — some short, but others prolonged for months, and varying greatly in brightness. All these minor displays have taken place without initi- ating or announcing earthquakes. It is obvious from the tables that the lens^ths of the inter- vals between the eruptions and the summit illuminations are too various, so far as now understood, to sustain the idea of periodicity. Relation to Seasons. — The evidence of a seasonal relation appears to be beyond question. Out of the whole number (nineteen), five, counting that of 1865, occurred in January, three in February, four in March, April, and May, and one in June, — making thirteen in the first six months of the year. Of the remainder four commenced in Auo-ust and two in No- vember. Thus fifteen out of the nineteen took place in the 220 VOLCANIC ACTION. wetter season. Add to these facts those from Kilauea, men- tioned on page 125, where the months given are March (?), January or June, May, Ma}^, October, April, April, March, and the number for the same months of the year becomes twenty or twenty-one out of twenty-seven.^ Full meteorological tables for a comparison of the months as to precipitation, both at the base and summit of the moun- tain, do not exist, and the discussion of this important question has therefore to be left unfinished. The following notes on the snows of Mount Loa are from Mr. J. S. Emerson of the Hawaiian Government Survey : — " The snow-cap of Mount Loa in general may be considered as making its first appearance in the early part of November, and as lasting until late into March. This is my impression from observa- tions the past season, which I think has not been particularly excepr tional. During the early part of November the snow-fall was quite light, and seemed to melt rapidly away at its lower edges. By the 25th there had been two heavy snow-storms, covering the mountain- top with a tliick coat, which lasted all through the winter. The snows are usually the heaviest in the month of February, I think, though I did not see the mountain during that month this year. My last view of Mount Loa was on March 29, when I could just distinguish patches or streaks of snow on the more protected portions of the summit." - The relation to barometric changes is an important subject for future study, with respect to which we have now no knowledge. There are also to be investigated variations in the amount of vapors over the active craters dependent on hygrometric changes. In view of the above facts it is probable that if there is any periodicity in eruptions it is more or less dependent on meteorological cycles. 1 This relation to the seasons, first recognized by Mr. Coan, is mentioned also by Mr. Green in his " Vestiges," etc., p. 332. ^ Letter to the author. PROGRESSIVE CHANGES IN THE MOUNT LOA CRATER. 221 Variations in Activiiy since 1843. — The copiousness of the subaerial discharges has diminished greatly since 1859. Before the end of that year, or in the seventeen years from 1843 to 1860, five of the eight great eruptions had occurred ; and of the three in the following twenty-seven years only one — that of 1880-1881 — was of great length. The frequent occurrence of the brilliant summit displays during the twelve years preceding the middle of 1880 is another striking fact. Six cases are reported ; and one was prolonged, with small interruptions, for eighteen months. The first of these displays occurred nearly four and a half years after the eruption of 1868. But Mr. Coan, the moun- tain chronicler, was absent in this country during one year ill the interval, — from the spring of 1870 to that of 1871. After the summit display of August, 1872, they came at short intervals, their lengths from the end of one yeai' to the beginning of another, reckoned in months, being five, three, ten, six, twelve. After February of 1877 there was the longer interval of three and a third years. Such short-period alternations seem to imply the recurrence after each of a sub- terranean discharge somewhere, if not a subaerial. The dis- play of 1877 quite certainly ended in a submarine eruption, and probably that of 1872 (pp. 202, 197). The Changes in Dejjth of the Summit Crater. — The changes since the year 1834, when the crater was visited by Douglas, have diminished its depth by at least four hundred feet, if we may trust — as we probably ought to do — his measurement " with a line and plummet," making it 1,270 feet. In 1840 Lieutenant Eld, U. S. N., of the Wilkes Exploring Expedition, made the depth on the west side 784 feet (p. 183), and in 1885 J. M. Alexander 800 feet (Plate X.). We know nothing as to variations in the level of the floor after and before an eruption, and nothing as to the down- plunges which have followed discharges. The terrace-levels 222 VOLCANIC ACTION. situated at the north and south ends of the crater may mark high lava-levels just previous to some ancient eruption, but they antedate history ; for Wilkes's map (p. 184) shows that they existed in 1840, very much as now. The map (Plate X.) by J. M. Alexander, which contains his ''estimates" of the dejDths of the terraces or '' plateaus " below the highest jDoint or summit, makes the terrace at the south end on a level with the upper of the two at the north end, suggesting thus that the two may mark one of the high lava-levels of the crater. In addition, it places the bottom of the South Crater (D), and that of the pit in the upper north terrace or plateau (A'), at or below the level of the bottom of the central crater, favoring the view that all three parts of Mokuaweoweo are still in active connection ; which view is sustained by the facts (1) that the fountain of May, 1880, was a South Crater fountain, and (2) that the pit A' was formed since 1874, as it is not in Lydgate's map of the crater of that year. 2. The Ordinary Work of the Mount Loa Crater. General Course of Action. — Although but few ascents to the summit crater have been made since the first by Douglas in 1834, and only five of these found the crater in action, there are still facts enough for important conclusions. The cycle of changes has been, beyond doubt, the same essen- tially as in Kilauea, — that is, when a discharge takes place : (1) the lava of the lava-column within the central conduit of the mountain falls to a level some distance below the crater (say one or more hundred feet), as a consequence of the loss by the outflow. Then begins (2) a rising of the lava of the column until it again shows part of its fiery top in the bot- tom of the crater engaged in its usual projectile work, and until finally it has reached a maximum height ; and then follows (3) a new discharge, and another time of inactivity for the crater. ORDINARY WORK OF THE MOUNT LOA CRATER. 223 The Projectile Action imthin the Crater. — Projectile ac- tion in the Mount Loa crater is in strong contrast with that of Kilauea. Instead of the Kilauea feature of low jets sug- gesting ordinary ebullition, witli only occasional throws to a height of one to two hundred feet, the descriptions of the summit action tell solely of fountains of clustered jets seventy-five to six and even nine hundred feet high, as if the height of the jets or the intensity of the action were proportional to the height of the lava-column. The four accounts of this activity — one in 1872, three in 1873, and one in 1880 — are alike in this respect. One of the three in 1873 describes the crater when the summit light appeared feeble from below, and the others when brilliant, and the former is scarcely less marvellous in its fountains. The evi- dence is almost conclusive that such fountains are of ordinary occurrence. This was the opinion of Mr. Coan ; and Mr. W. L. Green, in view of his summit observations in 1873 and the reported facts of others, ascribes to all the periods of summit illumination '"great fountains." 3. Causes op the Ordinary Movements within the Crater. The Rise of the Lava in the Conduit. — The rise of the conduit lava may be safely attributed in part, probably a large part, as in Kilauea, to the quietly acting ascensive force in the lava-column. The other volcanic agency of greatest prominence, as ad- mitted for other volcanoes, is that of the rising, expanding, and escaping vapors. The vesiculating effects of the vapors as regards the Mount Loa flow of 1880-1881 have been already described on page 166 ; and it remains to consider — 77^6 Cause of the High Projectile Action in the Summit Crater. — Higher projectile action in Mount Loa than in Kilauea through the escape of elastic vapors might come (1) from greater viscidity in the lava, or (2) from less specific 224 VOLCANIC ACTION. gravity of the material, or (3) from a larger supply of vapors. The. first of these causes cannot be the right one, for greater viscidity should lead to high cinder ejections ; on the contrary, the lavas show that they are as mobile as the Kilauea lavas by the velocity of the lava-streams and all the attending phe- nomena, and more by the free play of the fountains. The second is set aside by the identity of the lavas in density, even to the occurrence of heavy chrysolite lavas with a spe- cific gravity of 3-2. If neither of these explanations meets the case, we have only the third to appeal to, — a greater volume of elastic vapors. It is, accordingly, probable that the cause which can produce occasional jets of one to two hundred feet in Kilauea is capable of producing the jjrevaiUng high jets or fountains of the summit of Mount Loa. The amount of work done there is ordinarily at least one hundred to a thousand times greater than in Kilauea ; for the jets are five to ten times higher. But why should the volume of vapors in the lava- column be greatest at the summit ? This difference in amount could not be a fact if the vapors within the slowly ascending lavas were from the profound depths that supply the lava, or even from depths much below the sea-level. For, under such circumstances, (1) the differ- ence in the amounts carried up to the two craters would be small, since the rate of supply from below would be essen- tially uniform ; and (2) the difference in the height of the columns would be more favorable to Kilauea, whose lava- column rises above tide-level but thirty-seven hundred feet, than to Mount Loa, nine thousand feet higher. The area of the floor of Kilauea exceeds that of Mount Loa. But if fresh water from precipitation over the island sup- plies the vapors, then the difference in the heights of the lava-columns is greatly in Mount Loa's favor. A section of its lava-colurnn at the sea-level may receive moisture during the whole time of its rise to the summit, a distance 3-8 times ORDINARY WORK OF THE MOUNT LOA CRATER. 225 that for Kilauea. The ratio 3-8 to 1 for the difference in supply of moisture to the columns would be too large on account of the little precipitation over the upper part of the mountain and the much less extent of surface in this part ; but it may safely be put at 2 to 1, if not 2i to 1. The ascen- sive movement in the Mount Loa lava-column may be some- what more rapid than in the shorter conduit of Kilauea, provided the hotter central portion derives any upward thrust from the pressure of the cooler lateral portion, as suggested on page 168 ; and this cause would diminish the difference between the two as to the supply of vapor received, yet not largely. The fact here apparently established — that only through waters from the island-precipitation could Mount Loa get its larger supply — affords new evidence that the inland ivaters are the chief source of the vapors concerned in Hawaiian vol- canic action. Is there any other Source of the Projectile Actio?i / — The lava-fountains of the summit crater are so marvellous in size considering the density of the lavas, so near the incredible, that we naturally seek for other possible explanations. Hydrostatic pressure is out of consideration, inasmuch as the fountains are at the summit of the dome, and at times throw their jets fifty to a hundred feet above the mountain's top, — over fourteen thousand feet above the sea-level. Another source of projectile action has been suggested by Mr. Green, as briefly mentioned on page 175. In opposition to other writers on volcanoes, he sets aside the idea that vapor of water is concerned effectually in the projectile action even of Kilauea. The feeble amount of vapors observed by him over the fountain of the summit crater in 1873, and the gen- eral absence of vapors from the flowing lava-streams of 1859 and 1880-1881, besides other similar facts, have led him to his position on this point. He recognizes the fact ^ that great 1 Vestiges of the Molten Globe, pp. 75, 162-167, 175, 272-278, 309, 314. 29 226 VOLCANIC ACTION. heaps and columns of clouds form over an active crater, and rise at times to a height of many thousands of feet ; but ac- counts for these on the assumption that the heated current ascending from the active crater derives rapid accessions of air from either side, and this air, by being carried up to cold heights, yields the moisture by condensation, and so forms the column of clouds. Further, he finds a cause of some projectile action for the Kilauea lava-lakes and others in at- mospheric air carried down by the descending lavas of the jets into the lava-lakes, — as the crests of waves carry down air into the sea ; and for the rest of it, or that producing the crater-fountains like those of Mount Loa, he holds that the ascensive action in the conduit, after a time of quiet, sud- denly overcomes resistance or stoppages that have come to exist in the conduit at depths below, and, as a consequence, the lavas, suddenly released, are thrown up in fountains, like the jets of mineral oil from an artesian boring. Part of the argument as to the absence of vapors of water has already been met in the remarks on vesiculation, by showing (1) how extremely little moisture is needed to pro- duce vesiculation, and (2) how much moisture hot air will dissolve and make invisible. It has also been stated (3) that if a lava-stream, flowing down Mount Loa, has but a single fountain-head, as is generally supposed, though not proved, nearly all the vesiculation must occur at the source, so that for this reason and the heated air above it, the lava-stream should be vaporless, or appear so, except where there are fissures below for additional supply.^ Further (4), direct observation proves that the vapors come up out of the crater. They often rise directly from the orifice of the crater, too low down for the air-current to have got into action ; and in such cases there is an obvious source for * Mr. Green states, as an exceptional case, that at one place oii the Mount Loa flow of 1880-1881 the lavas spread into a large lake, and vapors rose from it in great amount. This is good evidence of the existence there of a local supply of lavas through a fissure. ORDINARY WORK OP THE MOUNT LOA CRATER. 227 the condensed moisture, and that is, the liquid lavas of the crater. Mr. Green expresses the fact well in the words : ^ " There is very often a large quantity of smoke seen to arise from the orifices of eruption, and this often spreads out in the higher regions of the atmosphere. There was a column, perhaps five hundred feet wide and ten thousand high, arising from the orifice of 1859 when we pitched our tent alongside it," — a point on the mountain ten thousand five hundred feet above the sea-level. Further (5), the feeble amount of vapor observed by him in 1873 over the fountain in the summit crater, so unlike what had existed a few days before, may have its explana- tion in the dryness of the atmosphere at the time. The air is generally dry at the summit, but must have its phases of unusual dryness, during which an unusual amount of escap- ing moisture would, for this reason, l^ecome invisible. (6) The summit fountain is a combination of jets, each of which must have had its initiating projectile act, and it con- tinues for weeks and months ; and this is at variance with the evidence from Kilauea, which makes the ascensive action very gradually and quietly lifting, instead of projectile. Finally (7), the cold atmospheric air carried down into a lava-lake by the jets could generate very little projectile power. The air, on entering the lavas, would encounter a temperature near 2000° F. if not beyond it, and hence the expansion would cause expulsion, or a speedy escape, in spite of any currents or intestine movements that might exist in the boiling caldron. For these reasons we may conclude that the old and gen- erally accepted explanation which attributes the projectile action chiefly to water-vapor is not seriously invalidated by the ingenious suggestions brought forward by Mr. Green. ^ Vestiges oi' the Molten Globe, p. 169. 228 ERUPTIONS OF MOUNT LOA AND KILAUEA. SOLFATARIC ACTION. The escaping vapors produce incrustations of sulphur at the mouths of fissures in and about the crater ; but owing to the intermittent character of the emissions, years often intervening between its periods as between times of erup- tions, no accumulations of sulphur or of other solfataric products exist about the summit. • In the caverns of lava-streams, where the escape of hot vapors is sometimes long continued when they are sit- uated over fissures, the same incrusting products have been observed as in Kilauea, among which glauber salt is sometimes abundant, as formerly in a cave near Kailua. Alum appears to be an unusual result in these basaltic regions. C. ERUPTIONS OF MT. LOA AND KILAUEA. In the following pages the subjects considered are: (I.) The Characteristics and Causes of Eruptions ; (II.) Metamorphism under Volcanic Action ; (III.) The Form of Mount Loa as a Result of its Eruptions; (IV.) The Relations of Kilauea to Mount Loa; (V.) General Volcanic Phenomena. Under the head of Eruptions, the principal topics are : the Kinds ; the Places of Outbreak ; the Causes ; the Characters of the Lava-streams ; the Position and Origin of the subordi- nate Lateral Cones. I. Characteristics and Causes of Eruptions. Eruptions are of two kinds : (1) Non-explosive eruptions, or quiet outflows, seismically attended or not; (2) Exp)losive eruptions, or catastrophic upthrows. There are also combi- nations of the two kinds. ORDINARY OR NON-EXPLOSIVE ERUPTIONS. 229 1. ORDINARY OR NON-EXPLOSIVE ERUPTIONS. Kilauea and Mount Loa are alike, as has been shown, in (1) their mode of work; (2) the southward position, in the crater, of the point of greatest activity; and (3) the general features of their eruptions. But in amount of eruptive work the summit crater is far ahead of Kilauea, and, in fact, it leads the world. Kilauea has had but one subaerial outflow of any magnitude in the last fifty years, and that only twelve miles long. Mount Loa, on the contrary, although nearly thirteen thousand feet up to the bottom of the crater, has had in the same time only one of its eight less than twelve miles long, and several between twenty and thirty-five ; and it has reached its height without a loss of eruptive power. It is reasonable, therefore, that Mount Loa should have most instruction to give about outflows. Height and Position op Outbreaks. The Height. — The place of outbreak of a Mount Loa eruption may have any height from the summit to levels far below the sea-level ; and this ''far below " may be (as the map on page 26 shows) 17,250 feet down, before reaching the actual foot of the eastern slope. The heights of known occurrence are mentioned in the table on page 217. The completion of the topographical survey of Hawaii, now in progress under the Government, will before long give more correct figures. The height of the source of the one Ki- lauea outflow, that of 1-', ' , ^~ panying sketch is a view. looking westward from the plain that was made hy the encroaching lavas ; it shows liow the lavas dammed up the already made valleys of West Oahu, and forced the drainage waters to take a north or south direction, nearly parallel with the base of the moun- tain, in order to reach the sea. The courses of these streams are given on the map. "^he depth of burial hy the East- Oahu lavas was probably some hundreds of feet. 302 VOLCANIC PHENOMENA 3. Evidence of Recent Change of Level. 1. Elevation. — Evidence of recent upward change of level is afforded by the elevated coral-reef along the sea-border. The dotted line on the map (Plate XIV.) has already been pointed to as approximately the inner limit of the raised reef ; the small dotted areas about Kahuku Point, the prom- inent north cape of the island, and in Laie, the district next southeastward, besides others west of Waimanalo, are the positions of hills or bluffs made of the reef-rock and consoli- dated drift-sands. The rock is in some parts a beautiful white fine-grained building-stone ; but generally it has sud- den transitions in texture and firmness, and much of it is a consolidated mass of broken corals, or else of standing corals made compact or nearly so with coral-sand. Along southern or southwestern Oaliu the height of the reef is fifteen to thirty feet ; and I estimated the amount of elevation indi- cated by it in 1840 at twenty-five or thirty feet. Kahuku Bluffs of Coral-rock and Drift-sands, with two Sections of the Drift-sand Rock. At the Kalmku blufi^s, which I visited anew in 1887, the solid coral reef-rock extends up in some places to a OF THE ISLAND OF OAHU. ;o3 height by estimate of fifty to sixty feet above tide-level ; and this is surmounted by drift-sand rock, made of beach coral-sands that were drifted into hills on the coast when the reef-rock was submerged, adding twenty feet or more to the height. There are large caverns in the bluffs, which are mostly witliin the upper layer of the coral-reef rock and have the drift-sand rock as the roof. In the preceding sketch a faint horizontal line may be seen passing by the top of the cavern ; it separates the beds of different origin. The coral reef-rock consists mostly of cemented masses and branches of corals of the kinds common in the modern reef, and also has often the corals in positions of growth. But the wind-drift beds consist of sand, and show the abruptly varying pitch in the layers connnon in wind-made drifts, as represented in the two sections to the right above. Another and more extended view of the bluffs is here added from a photograph by Dr. J. S. Pratt, of New York, taken on febESD Kahuku Bluffs, called Kahipa (from a pliotograph). the 5th of September, 1889.^ It exhibits finely the abrupt transition from the coral-reef rock to the drift-sand rock by the horizontal line of crevices which erosion has made, and also brings out distinctly the variations of pitch in the layers of the latter. The change of level along northern Oahu, according to 1 The author is indebted for the photograph to A. F. Judd, Chief- Justice of Honolulu. 304 VOLCANIC PHENOMENA the facts from Kahuku, appears to have been at least fifty feet, or twenty feet greater than the facts on the southern side indicate. Even with an accurate measurement of the height of the reef-rock the amount of elevation would remain doubtful, because the coral-reefs off the island are at present rarely up to low-tide level ; and this may or may not have been the fact before the change of level took place. The surface of the elevated reef of Oahu is exceedingly un- even from unequal construction and erosion, and its interior has in some places large and winding caverns, so that an overlying formation, were there one, would afford an example of imconformability by denudation. It is obvious that with greater elevation the unevenness would be as much greater, — large enough to get the credit, perhaps, of representing an interval of many thousands of years, although results of the " modern " period in geology. Denudation works rapidly among limestones, and especially so when the limestones have just left the water, with the usual irregularities of upper surface and texture. 2. Subsidence. — A former subsidence of the island is ap- parently indicated by the coral-rock, through the depth to which it has been found to extend in Artesian borings. In these borings, described above, a depth of seven to eight hundred feet was found for the coral-rock, and more than one thousand for broken corals ; and over seven hundred is reported by Mr. McCandless from a well in the Eua district, alwut five miles west of Honolulu. The facts lead to the inference that the subsidence amounted to at least eight hun- dred feet, and that it corresponds to the coral-reef subsidence which Darwin's theory requires. Mr. McCandless informed me that fragments of corals like those of the modern reefs were brought up from the various levels. This evidence of subsidence to the amount stated is not, however, complete. Doubt remains because the corals brought up in fragments have not l)een examined by any one compe- OF THE ISLAND OF KAUAI. ' 305 tent to decide on their actual identity with existing species ; I could not find that any of them had been preserved. In a series of specimens of the beds passed through in an artesian boring in Honolulu, on the property of Mr. J. B. Atherton, for which I am indebted to President Merritt, coral or shell sand occurs more or less freely in all the samples, and some consist wholly of such sand, or of sand and larger fragments ; but the fragments were in general from the reef-rock, or if from corals, not of sufficient size for the identification of species. The well was carried to a depth of 655 feet, and beds of coral and shell sand were found at the following depths : between 12 and 65 feet, 70 and 190 feet, 200 and 230 feet, 275 and 280 feet, 290 and 320 feet, 355 and 400 feet, 455 and 480 feet, and 505 and 515 feet. The facts are not sufficient to answer the question as to the species that contributed material to the calcareous beds. We may hope that the study on the island of the specimens brought up in future artesian borings will remove the doubt that remains. III. ISLANDS OP KAUAI AND NIHOA. A. KAUAI.^ Kauai is nearly circular in form, and has an average di- ameter of twenty-nine statute miles. The land rises very gradually from the coast, except on the western side, where there is a precipice fronting the sea of o*ne to two thousand feet. Elsewhere there are usually cliffs of two or three hun- dred feet, above which commences a gently sloping shore- plain, two to five miles wide. This cliff occasionally retreats inward, leaving a sea-coast plain surrounded by an amphi- ^ This description of Kauai consists of extracts from the author's " Exploring Expedition Report " on the island, which was based on explorations for the larger part of a week in 1840. 39 306 VOLCANIC PHENOMENA theatre of steep hillsides. The surface of the interior is broken into ridges and valleys, many of great extent. The loftier summits tower up with steep, unbroken sides three or four thousand feet above the other heights around them, and some of the gorges are one to two thousand feet deep. The altitude of Waialeale, the highest peak, is estimated at eight thousand feet. Toward the west side of the island there is a mountain plain about four thousand feet above the sea. The valleys of Kauai are as much more extensive than those of other islands of the group, as its peaks are more irregular, abrupt, and broken. Hanalei valley, w^iich opens on the northern coast, is a wide plain for many miles, though becoming a narrow gorge above ; it separates a ridge on the east from the mass of mountains on the west. Hanapepe valley opens on the opposite or southern shore, and is one of the most extensive in the island and also the one most to be enjoyed for its beauty. Its waters, like those of Hanalei, rise in part from the peak Waialeale. At the " Falls," four miles up the valley, " we w^ere in an amphitheatre of surpass- ing grandeur, to which the long defile with its fluted or Gothic walls, decorated with leaves and flowers and a succession of cascades, made a fit entrance-way. On the left there stood, apart from the walls, an inclined columnar peak or leaning tower, overhanging the valley. From a gorge on the right, where the basaltic rocks stood out either side in curved ascending columns as if about to meet above in a Gothic arch, a stream leaped the precipice and fell in dripping foam to the depths below, where, gathering again its strength, it went on its shaded way down the gorge." The Wailua, the chief river of eastern Kauai, also has its noted w^aterfall ; but it is situated within the shore plain, two and a half miles from the sea. The stream, about thirty yards wide, divides and descends a precipice of one hundred and sixty feet. For the last two miles of its course the width is about fifty yards, and the depth sufficient for canoes ; but, owing to OF THE ISLAND OF KAUAI. 307 the sand-bar at its mouth, its fifty yards at the end become three or four. Nearly all the smaller streams are closed in a similar way by bars made of coral-sands, and so com- pletely that the}^ may generally be crossed at mouth on dry land, the water escaping through the sands. Among the lofty summits of the interior there is no well- defined crater. The ridges, as they reach toward the sea, are very distinctly seen to decline gradually into the shore plain, this plain being, in fact, but the base or foot of the mountains, continuing the slope of the ridges to the sea. Moreover, the plain and the ridges show not merely a continuity of surface, but also of internal structure. The river channels which in- tersect it, like those of the dividing plain of Oahu, are often three hundred feet deep, and have a uniform stratification, which extends, without changing essentially its inclination or general character, far toward the centre of the island. The layers are remarkably regular, and dip with the slope of the plain at an angle of one to five degrees. They are so nearly horizontal that the inclination is often hardly appar- ent. The dip is away from the interior toward the shores, the layers rising gradually toward the interior from the southern, eastern, and northern sides. The layers differ much in thickness, and enlarge toward the interior ; within five miles of the sea they vary from ten to one hundred feet in thickness : twenty to twenty-five feet is the mean. The rock is the usual light gray basalt found on Oahu and to the eastward. It varies from scoriaceous, recent-looking lava to the most compact. Chrysolite is usually present, and in the Hanapepe valley masses that had come from the moun- tains contained crystals an inch or more in tlieir several di- mensions. A tendency to a columnar structure is common in the layers, and in some regions, as in the valley just men- tioned, the columns are well defined and a marked feature in the scenery. Curved columns often occur in places where at first it 308 VOLCANIC PHENOMENA seems difficult to account for them by reference to the posi- tion of the cooling surfaces. The middle or interior of a layer, which in other parts is vertically columnar, pre- sents at times singular examples of contorted columns ; the straight columns curve to the right or left for a short dis- tance, and then gradually resume their original direction. The explanation may be found in the fact that over streams of cooling lava steam-holes remain for many months, and sometimes for a year or more after the eruption has ceased, emitting hot air and vapors ; and under such circumstances the cooling of the interior must take place very unequally ; curvatures of various forms might thus be produced, and still derive their peculiarities from the position of the cool- ing surfaces, or, what is equivalent, the direction in which the heat was drawn off. Besides the mountains and hills which along with the shore plain constitute the great mass of the island, there are some ridges near the eastern shores which appear to be distinct from the rest, since they lie between the border plain and the sea. One of these is the Hoary Head Ridge, which stands along the southeast corner of the island and passes inward toward Koloa. It has an abrupt front toward the interior, and an uneven serrated outline. Wailua River cuts through one of the ridges about half a mile from the sea ; and near by parallel layers of lava were distinct to the summit of each of the rugged peaks, dipping eight to ten degrees northeast- ward or nearly toward the sea. A similar dip occurs in the summits a few miles south of Wailua, near Nawiliwili. Eight or nine miles north of Wailua, back of Anahola, on the north- east shore of tlie island, there is a high border ridge with needle summits in which the usual stratification is apparent. One of the curiosities of the place is a hole through one of the summit needles near its base. Kauai has also its lateral craters near the sea in the vicinity of Koloa, much resembling those of Oahu. An area OF THE ISLAND OF KAUAI. 309 KoLOA Volcanic District. of eight or ten square miles, containing several cones, is rep- resented in the accompanying map. Black lavas, as bare as many of the lava-fields of Mount Loa, form the surface over a large part of the area, ;ind the lava-streams often have a ropy exterior and are bulged up into domes and ridges like modern lava- streams. One of the domes not far from Koloa contained within an open space or cav- ern, ten feet high, twenty broad, and fifty long, and the bulged layer which made the cover was about five feet thick; it was evidently a vapormade bulge. The roof was very rough, but not stalactitic. The waves of the ocean, driving over the black rocks into dark recesses, and rising in copious jets or dashing into foam, afford majestic sights wherever seen about these volcanic islands ; and some of the spout- holes of Koloa are unusually grand. The Koloa lava is the common black or brownish black, somewhat cellular basalt of such regions; and it is sometimes columnar. Along the banks of a stream there are well-defined prisms, about eighteen inches in diameter. The horizontal joints are flat, not concave. The number of volcanic hills is five ; and among them one contains two craters, and another three craters, as shown in the preceding map. With one ex- ception, they are low, with a rounded contour and barren earthy sides, looking as if made of dark-colored brickdust. The one exception, called the Old Crater, is represented to the left in the accompanying sketch. It stands about one liundred and fifty feet above the plain. Its steep and ragged summit consists of dark brown lava and scoria. The bare 310 VOLCANIC PHENOMENA sides are smooth till near the summit, where the lava breaks out in columns, so rude and jagged as scarcely to be col- umns, yet appearing columnar from below. It forms a nar- row wall, or crest, broken by numerous rents, and is mostly The "Old Crater" and Others of Koloa. wanting on the east-southeast and west-northwest sides. The crater is about one hundred and fifty yards wide at top, and has a depth of thirty or forty yards. The surface within is smooth, and consists of red earth, like the lower slopes of the exterior. The lava of the crest owes its roughness, in part, to a thin laminated structure and numerous vertical fractures. The laminae are from half an inch to two inches thick ; and although not easily separated, they stand out prominently over the worn or decomposed surface. The rock has been rendered very irregular froin disintegration, and at top the columns are sometimes unevenly tapering. Besides these sources of its rough features, the walls within are covered with lava in twisted shapes, forming patches plastered on the surface or hanging in stalactites. The rock of the crest is very cellular, and much of it is scoriaceous. To the eastward of the Old Crater, about three fourths of a mile, there is the small hill, with evenly rounded top, rep- resented in the foreground of the preceding sketch. It has a shallow cavity, about one hundred feet in diameter, broken down on one side, with walls of semi-columnar lava on the other. The lava is lamellar in structure, like that of the OF THE ISLAND OF KAUAI. 311 Old Crater, and the surface is covered with ropy and twisted slag-like scoria. The lavas of the Koloa district probably issued from some or all of these craters, and from fissures in the plain. All the hills, with one exception, lie nearly in the same line; and hence a large fissure was probably opened in the direc- tion of this line, from which the eruptions took place, certain points along the fissure becoming vents for continued erup- tion and giving origin to the cones, — the usual mode of action on Hawaii and in other volcanic regions. In the Old Crater the lavas appear to have boiled up to the top, and thus formed the crest, as a ridge is formed around a lake in Kilauea, and then subsided again, leaving the sides covered with pendent masses of scoria. The red soil of the Koloa district resembles that in other parts of the island. The effect of the growth of vegetation upon it, in bringing the iron into new combinations with or- ganic acids, is seen about Koloa, where there is a foot or so of dark loam. The cavernous surface of these lavas appears to soak up whatever waters fall, and the region is mostly barren except in the immediate vicinity of Koloa, where there is a fine stream and some marshy soil. The island of Kauai is thus like the other Hawaiian islands, in (1) the generally basaltic character of its lavas ; (2) the dependence of its slopes, and of the dip of the lava- streams in the central mountains and of the border plain, on the pericentric discharges of a great central vent, once exist- ing in the region to which the dips around point ; (3) the gentle angle of the lava-flows from the vent, ordinarily one to five degrees, and often hardly distinguishable from hori- zontality ; and also (4) in its recent-looking lateral cones. Moreover, the valleys and peaks indicate that its fires long ago ceased, — as long ago as those of eastern Oahu, if not before. The elevated plain in the western part of the island, about four thousand feet high, needs special investigation as to the 312 VOLCANIC PHENOMENA OF KAUAI. dip of the layers ; and so also the lofty precipice on the side fronting to the northwestward. There may be indications, as has been supposed, of a second great cone, and of the loss of a part of its mass by a profound subsidence. The fact that this precipice of Kauai has the same direction as, and is nearly coincident in line with, that of eastern Niihau, the island to the southwest, and that Niihau has beyond ques- tion lost the larger part of the original cone or dome by engulfment, are evidence that the subsidence appealed to is not an improbability. With regard to the origin of the eastern shore-ridge, there remains much doubt. It may be the result of a faulting and uplifting of the strata ; yet this is not probable. The shore plain, inside of it, is evidence that no extensive degradation has taken place over the surface of this plain since it was formed. It may be that we must look far back into the his- tory of Kauai for its explanation, to a period before the ma- terial of the present mountains was ejected, when an earlier cone was broken down, and this ridge was left, as Somma antedates the present cone of Vesuvius. In this case the shore plain must have derived its lavas from the volcanic mountain which subsequently rose. The Interiok of Volcanic Mountains. Dissected volcanic mountains, like Kauai, reveal facts with regard to the earlier progress of the cone — that is, the earlier work of the volcano — which in some cases enable the investigator to mark off stages in its history. The island of Kauai, therefore, deserves study, as much as the more famous Hawaii at the other end of the group. One significant fact observed by the author in 1840 has been mentioned, — the much greater thickness of the streams or layers of lava in the interior, — a thickness of a hundred feet occurring within five miles of the sea. The observa- THE INTERIOR OF VOLCANIC MOUNTAINS. 313 tions of the author the previous year .on Tahiti had proved that island to be essentially the remains of a single great volcanic mountain, the stratification along the sides of the valleys having a regular dip of usually 3° to 5° seaward (see map of Tahiti, p. 375). Moreover, the fact was observed that the '' layers become thicker toward the interior." It is stated in the author's " Report " that "five or six miles from the sea, bluffs of a thousand feet constitute apparently a single continuous bed, or at least there is no line of demar- cation separating it into parts. Not unfrequently the whole height exhibits a continuous columnar structure throughout." In the face of one precipice in the Matavai valley about five hundred feet high, where the columnar structure w\as dis- played with considerable perfection, the columns, which were ten to twenty inches in diameter, were at several places con- verged to a point and then restored to parallelism. The breadth occupied by one of these converging clusters was about ten feet ; but others were larger. The conclusion follows that the volcano in its earliest outflows poured out its deepest floods, and afterward the shallower streams, producing the ordinary tliin-stratified structure of the exterior and border resrion. Tahiti illustrates other points with regard to the occasional, if not common, condition of the central re^i-ion of the o-reater volcanic mountains, — that is, the region of the lava-column. The author observes^ that "in the lofty peak of Orohena the massive structure is still more remarkable. In the view from the top of Aorai (figure on p. 378) a surface of three to four thousand feet is exposed, almost bare of vegetation, and throughout it no trace of layers was detected. Instead, indi- cations of a columnar structure were observed. It was owing, apparently, to this even continuity of surface that the usual amount of vegetation was not spread over it, for there was 1 Exploration Expedition Geological Report on Tahiti, Bolabola, Maurua, pp. 294, 301, 305 ; New South Wales, p. 498. 40 314 VOLCANIC PHENOMENA OF KAUAI. only here and there a crevice that could sustain even a bush." Further, the thick layers of the interior differ from the thin-bedded in being much less vesicular, and " usually com- pact with only minute cellules, if any." Six to eight miles up the Papenoo valley rounded stones of a whitish crystalline dioryte-like rock were found by the author, which must have come from some of the central heights ; and they suggested the view that the massive character of the rock, through thousands of feet, was due to the cooling, on the decline of the volcano, of the great central mass of lava, or that of the lava-column ; and that the coarse crystallization of part of the rock was owing to the extreme slowness with which cooling in so thick a mass would go forward. On the island of Bolabola, another of the Society group, Ellis found, he states, "masses of rocks composed of feldspar and quartz ; " and on Maurua, a species of granite is reported as being in considerable abundance. The author's " Expedition Report," in citing these facts, adds that the rocks are very similar to a grayish Vv^hite feldspathic rock observed by him at Prospect Hill, in New South Wales, which there graduates through porphyritic kinds into an ordinary black basalt. Such facts led the author in 1839 and 1840 to the conclu- sion, which he has ever since held, that grade of crystalliza- tion in crystalline rocks is an expression of rate of cooling ; that " although the liquid rock of volcanic outflows generally cools without distinctly visible crystallization, or with only crystals of feldspar, or of augite, in a compact base, " the cooling is sometimes sufficiently gradual to allow of the whole crystallizing ; and in this case the texture throughout is crystalline and the rock much resembles a granite." And further, that " particular crystalline rocks have no necessary relation to time on our globe, except so far as time is con- nected with a difference in the earth's temperature or climate, and also in oceanic or atmospheric pressure ; for if the ele- THE INTERIOR OF VOLCANIC MOUNTAINS. 315 merits are at hand, it requires only different circumstances as regards pressure, heat, and slowness of cooling, to form any igneous rock the world contains." ^ Thanks to the investigations of Allport and Judd, and in this country of Messrs. Hague and Iddings, this not hasty inference is now an established fact in the science of igneous rocks. Elevation of the Island. Kauai has its growing coral-reef and its elevated reefs, and in these respects resembles Oahu. The growing reef is narrow, and is absent altogether on the side of the mountain cliff, where the depth is too great. The beaches of coral-sand are quite extensive on the eastern or windward shores. A low beach-made ridge continues along them, seldom interrupted, which is raised from ten to twenty feet above high tide, and in some places, where drifted by the winds, thirty to thirty-five feet. About tlie mouths of the streams the sands are often thrown up so as to close the stream entirely, as far as appears at the surface, and deltas of small extent ai-e sometimes formed, as off the mouth of the Hanalei valley, at Anahola, and at other places. The deposits contain, in some parts, the shells and corals of the present shores but little altered, and resembling beach- worn specimens. There is a small bank of this kind near the mouth of the Hanalei River, four or five feet above the existins: level of the sea. But such beds of shells are not connnon, and by far the greater part is without a fragment larger than a grain of sand. It is remarkable, also, that these sand de- posits, formed at the mouth of a river fifty yards wide, should be nearly pure from mountain detritus. The hills, two to three miles back, are covered with loose soil, and the banks of the stream, beyond the termination of the coral-sand de- posit, consist of soft earth from the adjoining declivities ; yet ^ Exploration Expedition Geological Report, |jp. 377, 378. 316 VOLCANIC PHENOMENA OF KAUAI. it is rare to find a basaltic pebble in the layers, and there is but a trace of earthy material. A few scattered points of a brown color and some of chrysolite may be detected. Facts of this kind show how uncertain is the evidence which a par- ticular deposit may present with regard to the nature of the surface of the country adjoining, or the amount of life in the waters. The fact stated is actually no more remarkable than the freedom of tlie present beach from basaltic material, for all these accumulations have had a beach origin. There are also solidified beach-deposits analogous to the drift sand-rock of Oahu, and as remarkable in character. One of the ridges on the shores of the Koloa volcanic district is here represented. It forms a chff of thirty-five feet ; the Bluff of Calcareous Drift-sands. cliff appears to be undergoing degradation from the action of the sea, and masses of large size are now lying at the foot. The ridge consists of a laminated calcareous rock, the thin layers of which lap over the ridge, exhibiting full proof of its drift origin. The dip, where greatest, amounts to twenty- five degrees. In some parts the rock is compact and impal- pable ; but generally it has a sandy texture, though seldom friable. The rains have worn or eroded the surface quite largely ; but in some places, where the waters have stood in cavities, the interior of the cavities has become hardened by infiltrating lime, and bowl-shaped depressions have been formed, lined with a crust of compact limestone three fourths of an inch thick and having no trace of a sandv structure. VOLCANIC PHENOMENA OF NIHOA. 317 This ridge is evidence of a change of level in the island of Kauai, though to what extent is not yet known. It was probably about as great as that of Oahu. B. NIHOA, OR BIRD ISLAND. The island of Nihoa is a remnant of a small half -submerged cone, fifty-two hundred feet long and sixteen hundred feet in mean width, situated about three hundred miles west-north- west from Kauai. It was surveyed in July of 1885 by Rev. Sereno E. Bishop, acting as assistant in the Hawaiian Govern- ment Survey ; and the following facts are from his report : — The island appears to be made up of the north side and of a portion of the east and west sides of a relatively small cone. The sea occupies its open centre in a large bay. From this bay there is for the most part an abrupt rise of forty to two hundred feet, and then a gradual rise to the summit of the cliffs which face the sea on the east, north, and west sides. The highest part to the northwestward is 900 feet above tide-level, and to the northeastward 869 feet. The island consists of scoriaceous layers made of well- cemented fragments, and has much loose scoria over the ashy soil of the surface. It is intersected by a great number of perpendicular dikes, "perhaps forty or fifty," from two to ten feet wide, having a nearly parallel course from east to west. Soundings about the island are required to obtain an idea of the form and size of tlie volcanic mountain of which it is a summit cinder-cone. The island of Kaula, twenty miles southwest of Niihau, was found by Mr. Bishop to be a cone of cinders or tufa, much like Punchbowl on Oahu ; and Leliua, an island near the north shore, was of the same general character. Kaula and Lehua are probably lateral cones of Niihau, made by submarine eruptions. 318 PETROGRAPHY OF THE HAWAIIAN ISLANDS. IV. PETROGRAPHY OF THE HAA^AIIAN ISLANDS. BY EDWARD S. DANA. For our present knowledge of Hawaiian lavas we are in- debted in the first place to the general descriptions of J. D. Dana in the " Geology of the Exploring Expedition " (1849), and W. T. Brigham in his " Notes ^ on the Volcanoes of the Hawaiian Islands" (1868); also C. E. Dutton (1884) and others. On the other hand, on the petrographical side, there have been published the microscopic study of basaltic glass of Hawaii, especially Pele's Hair, by Krukenberg,''' in 1877 ; a paper by Cohen,^ devoted chiefly to the glassy basaltic lavas of Hawaii ; brief descriptions of isolated speci- mens of nepheline basalts believed to have come from Oahu, by Wichmann * and by Rosenbusch ; ^ tinally, a recent memoir by Silvestri,*^ describing a series of ancient and modern lavas from Kilauea collected by Professor Tacchini in 1883, The specimens — the results of whose study are detailed in the following pages — were collected by Prof. J. D. Dana on his trip to the Hawaiian Islands in 1887, and by the Rev. E. P. Baker, of Hilo, in 1888. The former were from Kilauea and parts of the coast region of Hawaii, and from Maui and Oahu ; the latter chiefly from the summit region of Mount Loa, and the summit crater Mokuaweoweo, but partly also from the cavern near Hilo, in the lava-stream of 1880-1881, remarkable for its stalactites, of which many fine specimens were included.^ 1 Memoirs of the Boston Society of Natural History, vol. i. part iii. 2 Mikrographie der Glasbasalte von Hawaii, petrographische Untersuchung von C. F. W. Krukenberg, Tiibingen, 1877. Also see preceding page 161. 3 N. Jahrbuch fUr Mineralogie, etc., 1880, ii. 23. 4 Jahrbuch, 1875, p. 172. s Mikroskopische Physiographie der massigen Gesteine, 1877, p. 510. « Comitato Geologico d' Italia, Bolletino, 1888, xix. 128-143, 168-196. ' Mr. Baker's extended trip over Hawaii, which comprised, besides an explora- tion of the summit crater, a visit to the sources of several of the great lava-streams, PETROGRAPHY OF THE HAWAHAN ISLANDS. * 319 Mt. Loa: Lavas of its Summit Crater, Mokuaweoweo, AND OF ITS LaVA-STREAMS. Of the summit specimens collected ])\ Mr. Baker, a consid- erable pvxYt are from the talus within the southern crater of Mokuaweoweo ao-ainst the neck between it and the central pit. (See Plate X.) A number of others are from the east- ern side of the central i3it ; and in the case of scattering specimens, the special source is mentioned more minutely beyond, when interest seems to attach to it. In general it may be said that all the specimens in hand from Mount Loa belong to the same class of basaltic lavas, although they vary widely : in color, from dark gray to light gray or dull brick-red ; in structure, from compact to highly cellular or vesicular, and from those of uniform grain to those which are prominently porphyritic with chrysolite or feldspar ; and in composition, from the very highly chryso- litic kinds to the feldspathic or augitic forms with little or no chrysolite. Specimens of pumice-like scoria are largely represented in the collection. The specimens may be divided pretty sharply into two groups ; and besides, there are several other types more or Jess distinct from these. Clinkstone-Jll'e Basalt. — The first of these doubtless in- cludes the rock which former observers have spoken of as resembling phonolite. Microscopically it has a uniform fine- grained texture, for the most part free from vesicles and ap- parently compact, though often found on closer examination to be minutely porous. The color varies from a dark bluish- gray to light gray, and to dull brick-red or brown, the grayish was undertaken in order to make the collections of rocks and gather facts with regard to the ernptions, and some extracts from his notes are published in -the " American Journal of Science," xxxvii. 52. The results have proved to be of very great interest. The specimens number about seventy, exclusive of the scoria and pumice, and of these fifty have been subjected to microscopic study. 320 PETROGRAPHY OF THE HAWAIIAN ISLANDS. kinds being the most common. The siDecihc gravity varies from 2-82 to 3-00. Some of the separate determinations on fragments freed from air by boiling are, — 3-00, 2-94, 3-00, 2-87, 2*82, 3-00, 2*82. Many of these specimens, as taken from the talus between the central and southern craters, are in the form of thin slabs, and their resemblance to clinkstone in the hand specimen, though not going beyond external asi^ect, is sufficiently close to explain their having been so named. As regards composition the rocks of this type are most strongly marked by the fact that the chrysolite, which is so common in large grains in the other specimens to be described, is absent or only sparingly present. The microscopic characters of this group of fine-grained compact rocks are also such as readily to distinguish them from the other forms.- In general, they consist of augite and plagioclase, with titanic, or magnetic iron, or both, prominent, but with little or no chrysolite. Their most interesting fea- ture is the form taken by the augite, which is only excep- tionally developed as an idiomorphic constituent, but on the other hand is not simply a formless substance filling the spaces between the feldspar. It is uniformly, though with varying degrees of distinctness, grouped in radiating forms, fan-shaped or feather-like, of great variety and beauty. This structure is eminently characteristic of this group of rocks. It is shown best in a fine-grained purplish-colored specimen (G. = 2-82). This is seen under the hand-glass to be minutel}^ porous though not properly vesicular, with minute slender red crystals (augite) projecting into the cav- ities. An occasional grain of chrysolite can be detected in the mass, and cleavage sections of feldspar are also seen. Under the microscope it is made up of lath-shaped feldspar individuals and the beautiful groupings of augites, these set out in relief by the fine grains of iron ore surrounding them. In the simplest cases the augite is bunched together in long parallel groups, slightly diverging at the extremities ; gener- PETROGRAPHY OF THE HAWAIIAN ISLANDS. 321 ally these branch off at various points into feather-like or dendritic forms, of such variety as to be beyond description. Groups of these forms radiating from a centre are common.^ Feather-like Forms of Adgite : a (X 35),^ (X 35), c (X 50) from Mokuaweoweo, d ( X 70) from Kilauea. The accompanying figure (1) shows several of the more complex of these forms [a, h, from the same specimen), and gives a fair representation of this remarkable structure. Fig. 2 gives the appearance of the entire field of the micro- scope, showing forms like the frost crystals occasionally seen on a stone pavement ; this figure is simplified by the omis- sion of some of the less defined parts. Some of the simpler rosettes are made up of both feldspar and ang:ite, alike radiating- from a common centre ; and fre- ^ Mr. H. Hensuldt, of New York, has called the writer's attention to an angitic lava from Tahiti, in which a pinkish, pleochroic angite is present in radiating groups of acicular crystals, often having a nucleus of chrysolite. The section is one of very exceptional beauty and interest, although the arrangement of the augite is hardly to be compared with that here described, since the individual crystals are sharp and geometrically grouped, — after the manner of the tourmaline in luxul- lianite, — which is in marked contrast to the feather forms of the Mount Loa augite. 41 322 PETROGRAPHY OF THE HAWAIIAN ISLANDS. quently the extremities of the feather ends are feldspar indi- viduals. Fig. 3 gives a detailed drawing of part of one of ll/lfi . i Feather-augite in Basalt from Mokuaweoweo (X 60). Detailed Drawing showing the Feather-like Grouping op Augite and Feldspar (X 100). the groups. It would seem that the feldspar was, as usual, first separated, and the augite, as it crystallized out into these dendritic forms, drew the feldspar needles into position with it. The two minerals are sometimes so intricately involved with each other that it requires close examination to sep- arate them. In polarized light the distinction comes out more sharply. Occasionally the feldspar is present in larger forms ; and more interesting to note is an occasional augite crystal (Fig. 1, h) that evidently belongs to an earlier generation, and shows the distinct cleavage, and more or less also the crystalline outline of the species. The alteration to which this specimen, with others like it, has been subjected, and to which the red or purple color of the rock in the mass is due, has stained the iron red, and reddened also the augite, although only exceptionally to such an extent as to make it opaque. The alteration spoken of may be simple weathering, although the occasional brick-red color rather suggests the PETROGKAPHY OF THE HAWAIIAN ISLANDS. 323 action of hot water or steam ; the feldspar remains perfectly clear and unchanged. From the specimen described, which may be taken as the type, we pass to the coarser-grained kinds on the one hand and to the very fine-grained on the other ; both of these still retaining, however, the same general characters. A highly cellular specimen (No. 74) with large vesicles, from the north- west brink of the crater, departs in general aspect most widely from the type ; but wliile relatively coarse-grained, it exhibits the same grouping, though somewhat more rigid and geometrical, and shows even more clearly the mutual relations of the feldspar and augite. In the finer-grained varieties the augite sometimes predominates so largely that the whole becomes like a confused carpet pattern of in- terlacing arabesque forms, though here, when an individual form can be traced out, it has great beauty and perfection, branching and rebranching like some delicate forms of vege- tation. Fig. 1, c, is an attempt to illustrate one of these forms, but it lacks the delicacy of the. original. These forms consist almost exclusively of augite, with very little feldspar. In another specimen of similar character a partial fluidal structure was noticed in the arrangement of the feldspar. When the iron grains are only sparingly present, and there has been no conspicuous alteration, the rock is of a light uniform gray ; but the presence of iron in large amount makes it nearly black and obscures this structure ; and when it and the augite are higlily altered, the rock is a bright brick-red, and in a section appears as a collection of nearly opaque red rosettes, the feldspar, however, still remaining clear. Glass is present occasionally, but usually in insignifi- cant amounts, and for the most part it is nearly or quite absent. This feather-form of augite which has been de- scribed is not entirely confined to the clinkstone-like vari- eties of lava, although eminently characteristic of them. It was occasionally noted more or less distinctly in some other 324 PETROGRAPHY OF THE HAWAIIAN ISLANDS. forms, especially the vesicular kinds to be mentioned later 4 (p. 329), where it is seen in the minute second-generation augite which formed in the last process of consolidation. All the facts observed serve to connect its formation with rapid cooling. Chrysolitic Basalt. — The second group of rocks makes a very marked contrast with those just described. These are of coarse grain, often open-cellular, and very highly chryso- litic ; on this account the specific gravity is much higher, it varying from 3'00 to 3*20.^ In many cases they have suf- fered some alteration which has given them a dull waxy sur- face, while the large grains of chrysolite are frequently iridescent, and sometimes have an almost metallic lustre. The color varies with the amount of iron-oxidation from light gray to dull reddish gray or brown. The mineral con- stituents present are those of normal basalt ; and most prom- inent among these is the chrysolite ; in some specimens it must make up nearly half the mass of the rock ; and in one case probably more, this particular specimen having the unusual specific gravity of 3-20. The chrysolite was evidently early separated from the magma, and the changes of condition through which the lavas have passed is well shown in the irregularly corroded or occasional broken form of many of the crystals and grains. Even when there is a distinct crystalline outline it is not a rare thing to find the crystal broken and the parts slightly separated. This is shown in the accompanying figures (4, a to/). Some of the corroded forms take very fantastic shapes. A novel and common feature of this chrysolite is the occurrence of very slender acicular forms. The length is often considerable, even when viewed microscopically, — in one case two to three millimetres, — but in breadth they are often hardly more than a line (note Fig. 4, a). This chrysolite shows the partial 1 Some of the separate determinations gave 3-09, 3-18, 3-09, 3-04, 3-00, 3-20, 300. PETROGRAPHY OF THE HAWAHAN ISLANDS. 325 alteration alluded to in a broad rim of brown iron oxide ; we can pa«s in the same slide from a crystal still preserving its Chrysolite in part with orientated titanic iron; a-f (X 55-60), from crystalline basalts of Mokuaweoweo; g (X lb) from basaltic glass, Mokuaweoweo; A (X 60) fron, Nanawale; ;. (X60), Kiiauea ; / (XlOO), crystal enclosing glass. Kilauea ;' rn (X 60) forked form, Maui; „ (X 60), portions of crystal enveloped by augite and clusters of magnetite grains, Maui. transparency throughout to those where only a string of chrysolite grains marks the position of the original individ- 326 PETROGRAPHY OF THE HAWAHAN ISLANDS. ual, and from these to the cases where a narrow brown line of iron oxide alone is left ; in a few cases the chrysolite is stained bright red, showing that there has been oxidation of the iron without h3'dration. The orientation of these peculiar rod-like forms, which are distinctly visible on a polished surface of the rock, is a mat- ter of some interest. The fact that in such a form as that of Fig. 4, h, and others like it, the plane of the optic axes is transverse to the longitudinal direction and the bisectrix nor- mal to the surface presented, shows that they are elongated in the direction of the vertical axis, the narrow dimension being that of the macrodiagonal. This chrysolite has often an unusually deep green color, possibly connected with the partial alteration, and then shows distinct pleochroism with the absorption least in the direction of the vertical axis. It often shows spherical inclusions of a pale brown glass, some- times arranged in parallel lines. The plagioclase feldspar is present in the ordinary forms, and shows no unusual features. The augite forms irregular grains crowded among the feldspars. Occasionally augite in larger more distinctly cr^^stallized forms appears, evidently belonging to an earlier generation. This earlier augite shows the tendency, often observed, to cluster about the chrysolite grains. The titanic iron is not as a rule abundant, and for the most part appears in long slender rods, often parallel among themselves over a limited area, and sometimes orientated by the chrysolite. In two or three of the specimens of this class the augite shows a tendency to assume the radiating form ; but this is the exception. Apatite is probably present in some sections, but only in small amount, and in most cases it was not detected. Glass is almost entirely absent from these rocks. The occasional fractured character of the chrysolite has been spoken of ; one specimen shows this in an extreme de- gree, the chrysolite being separated here into many angular fragments, for the most part showing no crystalline outline. PETROGRAPHY OF THE HAWAIIAN ISLANDS. 327 The feldspar and augite individuals have also suffered in the same way, and the ground mass has a curiously mottled microcrj'^stalline structure suggestive of some porphyry. This specimen stands comparatively alone, although two or three others are of somewhat similar character. The lavas of the svnnmit containing the most chrysolite were obtained, Mr. Baker states, from tlie southern border of the crater. Lavas with minute Crystals of Feldspar and Augite in their Cavities. — Allied to this second class of rocks just described are a number of specimens which are interesting because of their remarkable crystalline structure. One of these is a light gray rock, with only occasional vesicles. It is, how- ever, throughout open and porous, v^itli minute cavities into w^hich project thin tabular crystals of feldspar seen distinctly with a strong hand-glass. A light yellowish augite is also observed, but the crystals are less distinct. Iridescent grains of chrysolite are scattered through the mass, and the frac- tured surface shows the same long lines of this mineral that are seen in the sections. An interesting feature of this specimen and of others like it (including one very similar collected two or three hundred feet below the summit of the wall making the east-northeast side of Kilauea, called Waldron's Ledge, also others from Makaopuhi) is the presence in cavities of a mineral of a milk- white color in very minute nearly spherical forms. These are rather abundant through the mass of the rock, each little cavity containing one or two of them. They are so small (rarely more than -2 or -o"'"'- in diameter) that it is very diffi- cult to determine their form, especially as the crystalline faces are dull and give almost no reflections. A hexagonal outline can usually be made out, and occasionally a triangular face through which the angle of another crystal sometimes projects, as if they were complex penetration twins, which the nearly spherical form also suggests. Only one of these forms 328 PETROGKAPHY OF THE HAWAIIAN ISLANDS. was detected in the thin sections, and the free side of this had a hexagonal outline, the whole being divided into sectors which alternately had like extinction, the surface of the sector being mottled in polarized light after the manner of some crystals showing anomalous optical double refraction. The fact that these little white spheres occur also on the inner glazed sur- face of the vesicles would seem to mark them of subsequent origin, and hence probably zeolitic. Their form suggests a rhomboliedral zeolite grouped like phacolite or the Australian herschelite. Two or three other zeolitic minerals were ob- served in isolated cases, but too sparingly and in too minute forms to be satisfactorily identified. In other specimens of this class the color is somewhat darkened because of slight alteration, the texture is coarser, and the cavities larger. Here the clear glassy feldspar tab- lets are very distinct ; and augite crystals, red or brown on the surface and opaque, also project into the cavities. Octa- hedrons of magnetite are often seen implanted upon the augite needles ; and bi'oad plates of titanic iron, with rhom- bohedral planes on the edges, sometimes attain a relatively large size. The feldspar tablets were here large enough to allow of their being separated and examined optically. In form they are either rhombic or acute triangular in outline, be- ing bounded by the planes c (001) and y (201) ore and;i; (TOl), with the prisms very small when present at all. They can often be seen to be twins in accordance with the usual albite law. The extinction on the clinopinacoid made an angle of — 14° to — 15° with the basal edge, which conforms to typi- cal labradorite, as might have been anticipated. These highly crystalline specimens are also much like some of those collected from ejected masses about Kilauea, and they may here have had a similar origin. All the specimens that have been thus far described were obtained with a single exception (No. 74, already located) either from the talus in the southern crater against I'ETROcaiAPHY OF THE HAWAIIAN ISLANDS. 329 the wall of the neck that joins it with the central pit, or else from the east side of the interior of central Mokuaw^eoweo. Nothing can be said in regard to the relations in place of the two types of basalt, which have been described, and which occur together at the points mentioned. Other Varieties of the Lavas. — A number of the specimens cannot be classed in either of these two groups. They are light gray in color, not vesicular, and sparingly provided with chrysolite, if it is present at all, and characterized by a very uniform granular mixture of augite and plagioclase. A specimen taken from a vein in the western wall belongs here, also another stated to have come from the highest point on the edge of the crater. Still another specimen from the north brink is similar, but is porphyritic with patches of a glassy plagioclase. Another group of specimens, differing in aspect widely from those described, although not essentially so in composition, are the highly vesicular kinds, sometimes coarsely vesicular, and again w^ith very minute cavities. They have for the most part a common character. Large grains of chrysolite are usually present, often very large in comparison with the size of the vesicles themselves, and w^ith these also are some- times large crystals of augite and feldspar, often grouped together. The ground-mass filling up the space between these first separated constituents is a dark fine-grained mass of plagioclase and augite with minute grains of iron some- times so abundant as to render the whole nearly black and opaque. The augite sometimes shows a tendency to group itself in the radiating forms already described. A fluidal arrangement of the feldspar is the exception, though occasion- ally observed in indistinct form. Only in rare cases is the whole mass of the rock made up of this fine-grained mass without the large crystals. A specimen from the source of the 1843 flow belongs here. A specimen wdiich is described as the '• ordinar}^ ancient 42 330 PETROGRAPHY OF THE HAWAIIAN ISLANDS. lava of the eastern brink of the crater'' is a dark-colored, coarsely vesicular rock (G. = 3-00), with chrysolite abundant in large grains, and augite and feldspar also in large indi- viduals ; the amount of the fine-grained dark base of later formation is relatively small, and the augite is somewhat radiated. A peculiar feature of the section is the inclusion by the augite of large plagioclase individuals not regularly orientated, and giving the whole augite a peculiar mottled appearance. Specimens of Glass. — The Mount Loa collection includes a large number of specimens of the scoria, many pumice-like specimens, some of them of extreme lightness, and also speci- mens of glass. Several of the glassy kinds were exau^ined microscopically. One of them was a dense black com- pact mass, uniformly glassy on one side, but on the other largely devitrified ; the smooth surface of the glass was roughened by minute projections due to the chrysolite crys- tals. Its specific gravity is 2-01. Under the microscope the glass had a uniform brown color and amorphous character, except for numerous minute doubly refracting points scat- tered through it. Here and there were clusters of small chrysolite crystals, having sharp outlines, and perfectly clear except for occasional inclusions of the glass and minute black iron crystals. A section cut transversely showed with great beauty the gradual transition from the amorphous glass to the largely devitrified lava. The pale yellow-brown glass of the border contained here and there elongated microlites, of dark Ijrown color, due to the glass immediately surrounding them, and also minute crystallites like those described below. In the intermediate zone the microlites were more numerous, and were surrounded by a brown oval aureole of somewhat deeper color than the rest of the glass, this having a beautiful spherulitic structure in polarized light. The nucleus was sometimes transparent (feldspar), and about this were curious PETROGRAPHY OF THE HAWAHAN ISLANDS. 331 dark brown processes thrown off in curved lines (see Fig. 5). The highly devitrified portion consisted of a nearly continu- ous mass of dark brown spherulites, and crowded among 5. Feldspar Microlite surrounded by dark filaments within an oval of brown glass (X 90). 6. Crystallites of various Forms (X 160). All from basaltic glass, Mokua- weoweo. them numbers of whitish nearly opaque crystallites. Many of the spherulites have a distinct nucleus of chrysolite or feldspar, and sometimes there is a medusa-like mass of dark brown bands radiating out from the nucleus. The crystallites (see Fig. 6) have sometimes a simple oval form., with a faintly indicated structure transverse to the longi- tudinal axis ; there are also compound forms with axes cross- ing at 90'', making a four-rayed star (6), or at 60^, and these last when repeatTed making a regular six-rayed star (c). Rarely these forms are resolved into a delicate skeleton form of the types indicated in d, e, f, and of many other less regular shapes. Similar forms of " crystalloids " are figured by Vogelsang in Plate VII. of his work '' Die Krystalliten." Chrysolite is distributed through the section in isolated crystals or in clusters. These crystals often enclose a con- siderable amount of the brown glass, and, while sharp in outline, have sometimes peculiar forms (Fig. 4, g), which are 332 PETROGRAPHY OF THE HAWAIIAN ISLANDS. interesting in connection with the corroded forms met with in the highly crystalhne basalts which have already been described. Feldspar is present in the more highly devit- rified portion ; aiigite not distinctly, except as some of the microlites are to be referred to it. Another specimen was lithoidal in character, and showed thronghout a distinct spherulitic structure. The nearly opaque spherulitic ground-mass contained many light brown transparent spherulites, and grains of chrysolite were scat- tered through as in the other. Lava-streams from. Mount Loa. — A considerable number of specimens are at hand from the streams of Mount Loa of different dates, and taken from points at various altitudes. For the most part they are simply the surface scoriaceous portions, and consequently without distinctive features. The flows of 1852, 1855-1856, 1859, are thus represented. There are also specimens of the normal crystallized lavas of the stream of 1880-1881 at Hilo ; of that of 1843 taken from near its source, which has been already alluded to ; and of 1868 and 1887. These are all dark-colored chrysolitic lavas, vesicular in a high degree, especially that from near Hilo (1881), and their characters are those of the vesi- cular forms spoken of on page 329. The specimens of the flows of 1868 are to be mentioned as particularly rich in chrysolite. Lava-stalactites from Caverns in Mount Loa Lava-streams. Perhaps the most interesting and remarkable formations connected with the lava-flows from Mount Loa are the deli- cate stalactites and stalagmites of lava which occur in the caverns. The specimens in the collection are mostly from a cavern in the lava-stream of 1881 near Hilo, as described on page 209. Figures of some of the forms of similar stalactites Plate XV. Stalactites from L AVA-CAVERNS NEAR IIlLO (J). PETROGRAPHY OF THE HAWAIIAN ISLANDS. 335 from the caverns of Kilauea are given by Brigliam, as more particularly mentioned later. According to the accounts given, the flowing lava-stream, crusted over at the surface, leaves behind it, when the molten material has flowed by, long caverns, usually five to ten feet in height, having a roof of one to three or more feet in thickness and a floor of the solidified lava. In the caverns are found hanging from the roof the slender lava-stalactites. In the Hilo cavern they were from a few inches to twenty or thirty in length, and in some places only six to eight inches apart. The diameter, which seems to have been determined by the size of the drop of the liquid material, does not vary much, Ijeing usually about a quarter of an inch. Beneath the stalactites, from the floor below, rise the clustered groups of the stalagmites. These delicate forms are so fragile that they hardly bear transportation, and it is consequently difficult to preserve the longer specimens in their original form. Through the kindness of Mr. Baker the writer has received an admirable series of them, part of which are shown, one third of the natural size, on the accompanying plate. These specimens were collected with great care and skilfully packed in moss, and although fractured at many points when they arrived in New Haven, and thus divided into sections an inch or two in length, it was found possible to cement them together in their original positions. The general aspect of the stalactites and stalagmites is so well shown in the series of figures on Plate XV. that but little description is needed. It will be noticed that while some are straight and nearly uniform, others are curiously gnarled and knotted, especially near their lower extremities. The end has often a little process thrown off at right angles, a little hook, or a close spiral of two or three turns, often tangled or knotted together. The simple rods are usually round, not often flat- tened except when there is a sudden change in direction, when they may l)e pinched together like a glass tube bent 336 PETROGRAPHY OF THE HAWAIIAN ISLANDS. when hot. The surface is exquisitely ornamented with most delicate markings. The stalagmites, formed by the drop- pings from above, are intricate clusters or piles of simple drops several inches in height, as well represented in Figures a and h on the plate. The exterior of the stalactites has usually a more or less bright metallic lustre, and, though sometimes dull and fine granular, the surface often reflects the light brilliantly from a multitude of crystalline facets ; these sometimes separate into distinct scales, shown to be largely hematite by their reddish streak, though magnetite is also present. Minute rounded crystals, apparently also of hematite, are sprinkled, often thickly, over the surface. Sometimes the metallic covering is very thin, or is not continuous, forming patches on a brown surface ; occasionally at the ends it is altogether absent, and the exterior is thus brown and glassy in aspect, 7 but still retains the polyhedral crystalline aspect ; this glass-like crust polarizes light, and is probably augite. ^ ^ ^ Over portions of the rods li'.Li^ "^^^^"""^P ^^ I '~^^1 — '^^^ i^ ^^1^ c^®6 of the straight uniform ones (see the plate) over the whole length — tlie sur- face is transversely ribbed or corded in the most delicate manner. The beauty and perfec- tion of these little ripple- marks, as seen under a Lava-stalactites (X f). hand-glass, are beyond description or adequate representation. They are parallel and symmetrical for a limited distance, but vary in fineness PETROGRAPHY OF THE HAWAUAN ISLANDS. and form with every change in direction of the stalactite itself. Their flow is especially varied abont each little projecting knob. Fig. 7 will give some idea of the trans- verse markings, bnt details of the structure can hardly be reproduced. The straighter portions of the stalactites are often solid throughout, though here and there they are hollow and con- sist of a mere shell. Often portions that are perfectly solid alternate with the cellular parts, or the solid parts contain a series of large vesicles. Fig. 8 gives longitudinal cross sections through a number of typical forms. In/ the lower cavity was thickly lined with crystals chiefly of feldspar. The exterior crust is seen in the cross section under the microscope to be very thin, and next to it comes usually a narrow but not always continuous band of augite, with occasional iron crys- tals. The solid parts contain within very slender lath-shaped feldspars of a con- siderable relative length, often from one quarter to one eighth of the diam- eter of the stalac- tite, as seen in a longitudinal section. In one case they showed a marked tendency to paral- lelism with the axis of the stalactite, but in other cases this was less distinct. A partial concentric arrangement as seen in a transverse section was also noted. The feldspars often have black longitudinal inclusions, probably of magnetite ; and their cross sections, square or 43 Longitudinal Sections of Lava-stalactites in outline (X f), showinfi open and solid portions, a solid and d open throughout, d with crystalline lining ; the lower part of / is thickly lined with crystals, chiefly feldspar. 338 PETROGRAPHY OF THE HAWAIIAN ISLANDS. Sections of L.vva-stalactites (X o) a longitudinal, b transverse (X 5). rectangular in outline, then have a large black centre of the same form. A rather deeply colored greenish yellow augite, somewhat pleochroic, is packed in among the feldspars, and occasionally shows sharp crystalline outlines. There are also numerous grains and octahedrons of magnetite, 9 and throughout a multitude of beautiful dendritic forms branching at angles of 90° or of 60°. This is one of the most marked characters of the sections. The areas, where these iron dendrites are crowded together, are less distinctly individual- ized, but no glass was noted. Chrysolite is also absent. Fig. 9 (a and h) will convey some idea of the appearance of the longitudinal and transverse sections. The fact that the structure is throughout coarsely crystalline with the normal constituents of the basalt — except the chrysolite — is an important point. The occasional cavities or open spaces in the solid parts of the stalactites are often beautifully lined with large rhombic tables of feldspar, perfectly clear, and so excessively thin as to suggest scales of mica ; also dark needles of augite, often curved and wire-like ; and octahedrons of magnetite. (See Fig. 8,/.) The feldspar plates have mostly the form of a symmet- rical lozenge (Fig. 10), with angles of 128° and 52° ; one side is shown by the clea.vage to be bounded by the basal plane, the other by the dome x (TOl). The extinction makes an angle of — 7° to — 9° with the basal edge, which conforms to that of andesine ; that is, a plagioclase somewhat more acidic than that determined in the rock mass. These feldspar plates are often marked on PETROGRAPHY OF THE HAWAHAN ISLANDS. 339 the edges with a thin black scale, presumably magnetite, with numerous minute circular open spaces containing many black points, as if the whole were formed by the drying of little bubbles. The augite crystals are often rough, and black witli magnetite. Where there are vesicular cavities, often filling the whole interior of the tube, these are lined with a comparatively smooth, shining web of feldspar plates and clusters of brown augite crystals, or of augite needles alone, woven together like basket-work. The dull surfaces of magnetite octahe- drons are scattered abundantly among the augite and feld- spar. The large quantit}^ of magnetite is shown by the fact that the magnet picks up many of the fragments of the stalactites, even when quite large. The specific gravity of fragments of the solid portion of a stalactite was found to be 2-98. The explanation of the process by which these unique vol- canic icicles have been formed is not easy to give. It is clear that further study, on the spot, of their occurrence and the cir- cumstances of their growth is called for. It seems at first most easy to think of them as made by the rather rapid drip- ping of the semi-viscid lava from the roof. The evidence at hand, however, shows pretty conclusively that they could not have been the result of simple direct fusion. The fact that they hang down from the solid crust, while the stalagmites formed by the dripping from above rise from the solid floor beneath, seems to prove that they were formed after the molten lava had passed by and the temperature had fallen below the point of fusion. If made directly from molten material, they could hardly be so perfectly crystalline throughout as they have been shown to be ; we should ex- pect to find them more like the glassy spatterings from the blow-holes of Kilauea mentioned on a later page. Moreover, the sorting out of the material is further evidence on the same side, — the crystalline shell of hematite and magnetite, 340 PETROGRAPHY OF THE HAWAIIAN ISLANDS. with its lining of augite, and within the solid crystalline mass, or the clusters of beautiful crystals chiefly of feldspar. Still again, the question has been raised as to whether the flow of a viscid liquid like the molten lava could form drops so small as the size of the stalactites shows must have been present. The fact that the lava rods or tubes of the stalactites are of nearly uniform size throughout their length, although bunched and knotted together at frequent points as has been described, is an important one.^ It separates them, as to mode of origin, from the stalactites of a limestone cavern, which form in a more or less conical shape from the flow down over the exterior surface of the lime-bearing solution. It seems to require that the shell should have formed first, and that these tubes should have lengthened by the material carried down within them, finally resulting in their becoming solid to a greater or less extent. This is confirmed by the fact that the parts seemingly most solid often prove to have at the centre minute crystal-lined cavities. The lengthening by the addition of material at the point of attachment above, the only other method that can be suggested, is difficult to conceive of. As the facts at hand are inconsistent with the theory of a direct formation from the melted condition, we are forced to speculate as to the power of the highly heated water- vapor, known to be present in large quantities, to form them from the roof by a sort of process of aqueo-fusion. This is a subject about which we know too little at present to make speculation very profitable, and the author prefers to drop the discussion here in the hope that further observations may throw important light upon the matter. The experiments 1 A stalactite from a Kilauea cavern collected by Prof. J. D. Dana is of interest here, since it forms an exception to those that have been described. Abont the first- formed stalactite, with its rather thick magnetite shell has been formed a second, somewhat vesicular and nearly concentric with it. This stalactite has the exterior coating of gypsum crystals spoken of by Brigham. PETROGRAPHY OF THE HAWAIIAN ISLANDS. 341 of Fouque and Levy in regcard to the formation of basalt with their important results, pursued the method of simple igneous fusion; and though Daubree has discussed the role of water in the formation of basalt and basaltic minerals, the investigations thus far made hardly seem to apply very closely to the present case. The fact that these stalactites occur also in the caverns of Kilauea has already been mentioned. Brigham describes them at some length ; and although it is hardly possible to accept all his statements literally, especially as to rate and conditions of growth, his remarks are quoted here at length :^ — " A formation which always excites the curiosity of visitors to Kilauea is found in many of the caves in the floor of the crater which have been undisturbed for several years. At first glance the tubes which hang from the roof and the curiously formed droppings beneath these seem to be of igneous origin. An exami- nation m situ, shows that this was not the case. The roof of these caves is about two feet thick and generally unbroken ; the stalac- tites do not occur under cracks, and indeed there is often no fresh lava over the surface. The formative process may be clearly seen as the tubes form from day to day ; and I have caught the steel- gray deposit in the drops on the end of the tubes upon my finger and watched its solidification. Usually the tubes are straight cylin- ders from one inch to three eighths of an inch in diameter, and some- times more than two feet long. The bore is almost never continuous ; and while externally they are smooth, within a mass of stony cells of considerable size is presented. As long as these tubes grow downward in the quiet upper region of the cave, they hang perpen- dicularly, but when they reach farther down the currents of air and steam blow the deposits to one side and the tube becomes distorted ; it may even return on itself. The drip in the bottom forms much thicker and more irregular stalagmites, as will be seen from the figure, which represents three actual forms, not occurring, however, in the same cave. Specimens have been found which exceed eight inches in diameter, and these are usually low and fiat-topped. The more slender ones sometimes rivse to a height of two feet ; and so 1 IvrciiioiT, ].!>. 4(;-2, i«:'.. 342 PETROGRAPHY OF THE HAWAIIAN ISLANDS. rapidly is the silica deposited that they seldom increase in diameter, but are true acrogens, none of the suspended silica running down the sides. In one cave the growth of the stalactites was at about the rate of an inch a week, but owing to the varying amount of water or steam the production is quite irregular. They are often coated with beautiful white crystals of gypsum, sometimes tipped with needle- like transparent crystals of the same mineral when the cave is high. The natives collect them with the upper open joint of a long bambu." The following analysis of the solid stalactite, by John C. Jackson, is given by Brigham : — SiOa AI.2O3 FeoOg MnO CaO MgO NaoO KjO G. == 2-9 51-9 13-4 15-5 08 9-6 48 30 11 = 100-1 Lavas of Kilauea. The specimens in hand from the volcano of Kilauea, which have been examined microscopically, include four specimens of the recent lava from the bottom of the crater, six speci- mens of the older lavas, two from Waldron's ledge on the northeast side, and four from the wall west of Halema'uma'u ; finally, a number from the ejected masses on the borders of the crater, especially on the west side. There are also a number of glassy and scoriaceous kinds. 1. The Rece7it Lavas. — The specimens of the recent lavas were taken from the stony part of the layer below an inch or more of glassy crust. They are dark-colored, vesicular basalts, containing chrysolite but not in very large amount. The irregular grains of chrysolite are often aggregated to- gether with augite crystals, and to a limited extent with the lath-shaped feldspars ; these constituents obviously represent- ing those which first separated from the magma. The mass of the solid portion of the rock is of uniform character, con- sisting of augite and feldspar, with the interstices between them black with the crowded grains or plates of magnetic and titanic iron ; about the borders of the vesicles the iron PETROGRAPHY OF THE HAWAIIAN ISLANDS. 343 is especially dense. It is very interesting to note that these specimens are the only ones among those from Kilauea which show distinctly the stellate feather-like forms of the augite and feldspar so characteristic of many of the Mount Loa lavas (as shown in Fig. 1, d, p. 321). The augite forms here are usually smaller and less varied, but there is the same grouping in parallel bundles diverging off at the ends into dendritic forms. The association between the augite and feldspar is also very close, as if the crystallization of the two had been almost sinmltaneous. Thus the feldspar not only forms in some cases the outer extremities of the feather, but sometimes also is a central rib flanked on both sides by the augite. Occasionally the chrysolite appears in the long slender forms noted as common amono; the Mount Loa lavas. One o of these is shown in Fig. 4, k, which also exhibits the peculiar feature of many of these rocks, often noted in other regions/ — the grouping of the titanic iron in parallel position about the chrysolite, normal to the vertical axis. An arrangement of the elongated forms of the titanic iron in parallel position over small areas is sometimes noted where there is no evident relation to the other constituents. Usually, however, the chrysolite is the controlling influence, and the individual often bristles with these little iron rods about its whole out- line, as seen in the section. Although these specimens were taken from so near the glassy crust, there is little or no glass shown in the thin section. A specimen from the bottom of the Little Beggar, the lowest part of Kilauea, shows very considerable alteration, the surface being covered, and the vesicles filled with crystals of gypsum ; the mass is rendered red and nearly opaque by the oxidation of the iron. A specimen of partially devitrified glass shows the presence of spherulites, like those mentioned in similar specimens from Mount Loa, increasing in number where the devitrification is 1 Of. Rosenbuscb, Massige Gesteine, 1887, p. 722. 344 PETROGRAPHY OF THE HAWAIIAN ISLANDS. most complete. Crystals of chrysolite and microlites of feld- spar are also present in large numbers. Some curious speci- mens from the spatterings about a blow-hole exhibit a vesicular glass with crystals of chrysolite and aggregates of augite and feldspar. The chrysolite encloses large amounts of glass, often in curiously arranged S3mimetrical bands. One of the crystals is represented in Fig. 4, /. 2. The Older Lavas. — Of the ancient Kilauea lavas one specimen from Waldron's Ledge is remarkable for its highly chrysolitic character, as its unusual density (G. = 3*18) well shows. It is a grayish compact rock, thickly sprinkled with greenish yellow chrysolite grains. Under the micro- scope the chrysolite is seen to be in large individuals, usually irregular grains, though also in indistinct crystals and occa- sional rod-like forms. These often contain abundant glass inclusions. The grains are often packed about with a poorly defined border of augite, and it is in this zone particularly that the little rods of titanic iron are regularly orientated, standing out from the chrysolite in the manner already described. Besides this, it is a granular mixture of augite and plagioclase, not showing any glass. The other specimen from the foot of Waldron's Ledge, is a light-gray cellular rock, highly crystalline, the minute cavities lined by plates of feldspar and tables of titanic iron. It is much like some of the specimens described from Mount Loa (p. 327), and with them is characterized by the same milk-white spherical mineral in the cavities, provisionally referred to phacolite. The lavas from the west wall of Kilauea west of Halema'u- ma'u are all closely similar in character among themselves ; they are dark-gray in color, vesicular, and contain a fair amount of chrysolite. The structure is throughout crystal- line, rather coarsely granular, and the chrysolite is marked by its usual bristling border of titanic iron. One or two of these show something of the radiatino;- augite forms. 3. Ejected Masses on the Borders of Kilauea. — The speci- PETROGRAPHY OF THE HAWAHAN ISLANDS. 345 mens from tlie borders of Kilauea are supposed to have been ejected at an explosive eruption about a century since. The larger part of the masses are described by Prof. J. D. Dana as being of a fine-grained, gray, slightly vesicular lava. Other specimens are reddish or chocolate-colored, coarsely granular and highly crystalline. In the latter the chrysolite is present in very large amount, and has suffered from alteration, — probably by the action of heated water- vapors, — so that the fractured surface is eitlier dull-red and opaque or else slightly iridescent. The feldspar crystals are clear and glassy, and where there are cavities they often project in distinct trans- parent plates from the walls. The crystals have an angle of extinction of — 14° with the h!c edge, and hence conform to labradorite, like those of similar occurrence among the Mount Loa specimens. Under the microscope the chrysolite is seen to be surrounded with a deep-red border, and the iron oxida- tion has penetrated into the mass of the crystal, sometimes along broad fracture-lines, and more generally in a network of fine wavy lines, giving it a peculiar feathery aspect. Not infrequently the oxidation has gone so far that the chrysolite is perfectly opaque, and by reflected light is bright brick-red. Three specimens among the examples of the light-gray lavas have peculiar cliaracters. One is a light-gray rock con- spicuous among all those under examination for its beautiful crystalline structure. It is very light and porous, and in each little cavity there are groups of crystals of feldspar in the usual rhombic plates, with minute slender needles of a pale yellow augite iridescent on the surface, and thick tables of titanic iron showing large rhombohedral planes (cr = 56°). These last have bright faces, often cavernous, and with a bluish steel-like tarnish. The augites are flattened parallel to the orthopinacoid, as shown by the parallel extinction and the oblique optic axis. Chrysolite is present in the mass of the rock, but hardly appears in the sections. Specific gravity, 310. 44 346 PETROGRAPHY OF THE HAWAIIAN ISLANDS. Another similar rock is more compact, except for paral- lel lines of cavities partially filled with black glass. A third shows the same structure in part ; but the mass of the speci- men has a base of a very black glass with crystals of feldspar, augite, and broad plates of titanic iron running through it. In the large cavities the crystals of these minerals project out, though the surface of the cavity is lined with a glassy web. The specific gravity is 3* 15. One of the sections under examination is cut across the junction, and shows both the uniform fine-grained crystalline portion and the glassy part with its large enclosed crystals. A curious feature of the glass is the presence of a swarm of minute apatite needles running through it in every direction. These do not extend into the crystallized parts. Apatite usually appears as one of the very earliest secretions from the magma, and why it should be thus localized in these patches of glass while absent from the crystalline parts of the rock it is difficult to explain. In general, apatite has been found to be a rare constituent of the Hawaiian lavas. Two other specimens are gray compact rocks, extremely fine-grained except for occasional chrysolite grains. Another is peculiar in having small uniformly distributed patches of a dark-colored slightly opalescent glass, which is deep brown, and nearly opaque in the thin section except as it is pene- trated by apatite needles, which here also are confined to it. With the specimen from Kilauea proper belong those col- lected by Mr. Baker from Nanawale and Makaopuhi, the former chiefly remarkable for their chrysolitic character, the latter sparingly so. Several of the latter specimens are re- markable for that crystalline structure that has been several times remarked upon, and one of them contains the white zeolitic mineral. Former observers have dwelt at length upon the features of the glassy forms of the lava and the presence of glass in the partly crystalline varieties. This is probably to be explained PETROGRAPHY OF THE HAWAIIAN ISLANDS. 347 by the fact that the specimens which first present themselves to the collector on his visit to the interior of Kilauea are the superficial more or less scoriaceous or glassy forms, which con- stitute merely a crust, and do not represent the true character of the average lavas. The writer has found glass only a comparatively insignificant element in the normal rocks, and often wholly absent, even from those of recent eruption. Relation between the Rocks of the Summit Crater of Mount Loa and those of Kilauea. In general the lavas of the summit crater and of Kilauea, so far as examined by the writer, are strikingly similar in char- acter, all being augitic basalts, varying chiefly as regards the amount of chrysolite present. The clinkstone-like rock of Mokuaweoweo has not been observed at Kilauea ; but the feathery grouping of augite and feldspar which characterizes it belongs to the recent Kilauea lavas as well. The darker- colored vesicular basalts, which are highly chrysolitic, and hence of high specific gravity, are alike from both craters. Writers on volcanoes have attempted to draw conclusions in regard to the distribution of the heavier and lighter lavas according to altitude, limiting the former to the lower levels. This is a natural inference on a priori grounds ; but it does not rest on observation, as the facts already stated sufficiently show. It is a striking fact in connection with the mechanics of volcanic eruptions that lavas of the heaviest character (specific gravity, 3-15 and 3-20) should have been raised to an altitude of nearly fourteen thousand feet above sea-level. The chemical composition ^ of the Kilauea lavas is well shown by the series of analyses (fourteen in number) given 1 The remark made by Prof. J. D. Dana must be repeated here, that the early analyses published in the " Geological Report of the United States Exploring Ex- pedition," having been made for him by an inexperienced analyst, are entirely unreliable, and should not be (quoted. 348 PETROGRAPHY OF THE HAWAIIAN ISLANDS. by Silvestri, and also those — chiefly of glassy forms — given by Cohen. Of these analyses three by 8ilvestri (A, B, C) and two by Cohen (D, E) are quoted here ; namely, — A. Recent vitreous basalt, fresh and unaltered. B. Older basalt, also fresh. C. Older basalt, much altered. D. Compact basalt-obsidian. E. Pele's Hair. A. B. C. D. E. G. = 2-97 G. = 301 G. = 2-8U G. = 2-75 G. = 2'66 SiOg 4920 4882 48-00 53-81 5082 TiOa 1-72 1-16 . . . 201 undet. AI2O3 14-90 15-22 25-45 13-48 9-14 FeA 4-51 5-72 1755 302 733 FeO 12-75 9-65 1-20 7-39 7 03 MnO 28 0-67 tr. Ir. 38 CaO 9-20 10-40 220 10-34 11-63 MgO 3-90 4-65 098 646 7-22 Na.O 1-96 2-10 ( 323 1-02 K2O 0-95 0-90 1 0.64 3-06 P2O5 042 tr. tr. ... ... H2O 010 . . . 1 87 057 1-74 99-89 99-19 99 23 10095 9937 Of other specimens from the island of Hawaii there are two specimens from Pimaluu, on the southern coast, — one from the outside of a bomb and the other from an aa flow. The interesting point about these is the strongly accentuated flow- structure as shown in the feldspar microlites as they find their way around the occasional large crystals of chrysolite and augite. The fluidal character is as a rule entirely absent from the specimens before described, and in general is not so common in basic as in acidic lavas. Specimens from western and northwestern Hawaii, Kawai- hae, and Mahukono are again more or less vesicular chryso- litic basalts. Of these rocks that from Kawaihae is the most noteworthy because of the large clusters of glassy feldspar cryst;ils, which give it a striking porphyritic aspect. PETROGRAPHY OF THE HAWAHAN ISLANDS. 349 Lavas of Maui. From the island of Maui about a dozen specimens have been subjected to microscopical examination, of which three were collected by Rev. S. E. Bishop. The most recent lavas of Haleakala are represented by three specimens, all some- what scoriaceous. One of these is from the summit at an altitude of nearly ten thousand feet, the others from the bottom floor. They are all very highly chrysolitic, and of high specific gravity (G. = 3-10). The similarity of the hand specimens is so great that they might almost have been taken from the same block. They are dark-colored, very vesicular, and highly porphyritic, with both chrysolite and augite. The large and well-formed crystals of augite often have a narrow external zone of deeper color (violet-brown), and are distinctly pleochroic. They are usually mottled with inclusions of glass or iron. The chrysolite shows but few inclusions. The ground mass is thickly sprinkled with iron grains, making it nearly opaque ; small triclinic feldspar needles and a secondary augite in minute form are seen. In these specimens the feldspar must make up but a very incon- sideral^le proportion of the whole. These recent chrysolitic basalts in Haleakala are much more porphyritic and otherwise quite different from the basalts of Mount Loa and Kilauea. More different still are several specimens of the older lavas. One of these came from within the crater. It is a very fine-grained, dark bluish gray rock of uniform texture, perfectly fresh, and showing but few minute cavities. It is a feldspathic rock, presenting under the microscope a rather confused aggregation of feldspar and augite, the latter in minute grains, the whole thickly sprinkled with grains of iron. Chrysolite is occasionally noted in peculiar elongated forms, generally forked at both ends, and having a border of titanic iron grains, as before noted (Fig. 4, m). The most 350 PETROGRAPHY OF THE HAWAIIAN ISLANDS. marked peculiarity is the presence of minute scales of a dark brown mineral, probably biotite, which, however, is only present very sparingly. Another interesting specimen (30) which was obtained from the top of Haleakala is a thin, almost schistose rock, light gray in color and presenting the same sort of an aggre- gation of feldspar and augite under the microscope. Chry- solite, however, is a prominent constituent, especially in the hand specimen. There are also large elongated but usually ill-defined aggregates of magnetite grains marking the pres- ence of original large individuals, biotite or hornblende, which have been re-absorbed into the magma. Occasional remnants of the original mineral are noted, but in very small amount. Another curious feature of this rock is the presence of a zone of augite about the grains of chrysolite. One case of this is illustrated by Fig. 4, :^i. The chrysolite crystal, though sepa- rated into different parts, has throughout the same optical ori- entation, as indicated by the shading, while that of the augite varies from grain to grain. The mantle of magnetite grains about the upper end of the chrysolite seems to represent the re- mains of the augite which has disappeared. This re-absorption of augite is not commonly observed ; but this case, and still more another one where of a single augite crystal alone a large part has disappeared in this way, place the matter above doubt. This zonal arrangement of the augite about the chryso- lite has been noted by other observers in a number of cases. ^ The structure and composition of both these last-mentioned rocks suggest that they should perhaps be classed among the augite-andesites rather than the basalts. To decide this point we have the silica determinations, for which I am indebted to Mr. Henry L. Wheeler, of the Sheffield Scientific School. He found in the first (29) 48-42 p. c. SiO.,, and in the other 50-44 p. c, which conform to that of normal basalt. 1 See F. D. Adams, American Naturalist, 1885, p. 1087; G. H. Williams, Amer- ican Journal of Science, 1886, xxxi. 35. PETROGRAPHY OF THE HAWAHAN ISLANDS. 351 The remaining specimen from the top of Haleakala is a dark gray, almost black rock, of the finest grain, very com- pact and breaking with a conchoidal fracture. It is charac- terized by the large amount of iron in minute grains very thickly distributed, so as to make the section nearly opaque unless extremely thin. The feldspar microlites are the most prominent constituent, and these show a rather distinct flu- idal arrangement. The two specimens from Paia on Maui are much like those from Haleakala just mentioned, espe- cially No. 29, and like it they bear the same resemblance to andesite. A curious point about them is their readiness to alter, the exposed surfaces passing into a soft earthy mass of a light brown color. The specimens from Western Maui, collected by Rev. S. E. Bishop, are rocks of peculiar and interesting character. Mr. Bishop says that they are " crusts and soft interiors of the same formation (apparently flowing lava) found on Launiu- poko Hill, three miles south of Lahaina. A precisely similar formation occupies the front of Mount Ball, two and one half miles above Lahaina. The crusts are often rolled under the gray soft material. Many crusts of grotesque form lie about, from which the softer part has been washed away. Many portions of the gray soft mass are of great thickness. Much building stone has been hewn from it. It presents no appear- ances of being the result of any decay, being compact and of uniform texture, except the hard crusts, many of which are crumpled up as if in flowing, like pahoehoe." One of the specimens (28) is a whitish gray compact rock, whose surface is worn out into a series of deep holes between projecting ridges nearly one inch in height. The texture, though appearing closely compact at first sight, is seen by the glass to be minutely porous, and the surface is speckled with very small rusty spots. Under the microscope it is seen to consist almost exclusively of plagioclase, here and there porphyritically developed ; there are also the remnants of a 352 PETROGRAPHY OF THE HAWAHAN ISLANDS. bright green pleochroic mineral present in traces only, and obviously the original mineral whose disappearance has left the rusty spots ; it seems to be hornblende. A little biotite is also present. Iron is scattered through the mass rather sparingly in minute grains ; no augite was noted. Another specimen shows the transition from the firm rock to a soft chalky condition powdering under the fingers. The section is very like the other just described, though the feldspar is much clouded and an occasional red crystal of chrysolite is noted. A third specimen (32) is a flake from a large bowlder (8 X 5 X 4 feet) found one mile southwest of the summit of Mount Ball. Mr. Bishop remarks that in the eroded cliff bowlders occur cemented by mud, being ejectamenta from Mount Ball. The specimen is finely schistose, and so soft and friable as to separate easily into thin silvery scales, and by handling it is soon reduced to ^2 a fine powder. Microscopic examina- tion shows it to be very nearly the same in material with the others, but having a distinctly fragmental appear- ance. There is more chrysolite present in small broken fragments of crystals ; there is also a little brown biotite in scales. The mass is made up of pene- tration twins of plagioclase, according to the Carlsbad law, mostly arranged parallel to tlie brachypinacoid, and hence showing no other kind of twinning. The form of one of these groups is shown in Fig. 12. The cleavage marks the position of the basal plane, and the angle of the section (about 80°) shows that it is bounded by the planes c (001) and y (2OI). The extinction makes an angle of a few degrees with the basal edge, varying + or — with a slight change in the direction of the section. This optical character and the further fact that the acute bisectrix is nearly normal to the brachypinacoid would make the feldspar an oligoclase. PETROGRAPHY OF THE HAWAIIAN ISLANDS. 353 Occasional feldspar individuals are cut more nearly parallel to the basal plane, and have the usual elongated form, and show the twinning like the other specimen, but as a rule they all lie nearly parallel to the brachypinacoid. The amount of silica present, as; determined by Mr. Wheeler, is 61'6o p. c, which corresponds to the microscopic determination. This re- markable feldspathic andesyte is a totally diiferent rock from any other which has been as yet obtained from the islands, and the writer hopes to be in the position later to give ii more minute account of its occurrence and composition. Lavas of Oahu. Of the specimens in hand from the island of Oahu, six (33, 36, 40, 41, 44, 45) are from the Kaliuwaa valley, near Punaluu on the north side of the island ; four (27, 38, 39, 43) are from the Waialua plain ; one (42) from a point just north of Kahuku Bluff ; another (37) from a gulch beyond Monolua, four miles west of Honolulu ; and, finally, there are a num- ber of specimens of the tufa froui the Punchl^owl, near Hono- lulu. Among these specimens, two are forms of higlilv chrysolitic basalts ; these are the specimens from Kahuku Bluff and one of those from near Waialua. In the first of these (42) the chrysolite makes up probably two thirds of the mass of the rock ; it is present in distinct isolated crystals, having the characteristic form, each crystal having a rather broad, rusty border, though the interior is for the most part clear and unchanged. The chrysolite encloses grains of iron, but very little glass. The ground mass is a fine-grained mix- ture of augite and plagioclase with considerable iron, the augite being the more prominent constituent. In the specimen from Waialua (43) the chrysolite is also prominent ; its specific gravity is 3*06. With the chrysolite, the augite and feldspar also occur in large individuals besides being present in the base. The feldspar here contains dark- 45 354 PETROGRAPHY OF THE HAWAIIAN ISLANDS. colored glassy inclusions in large numbers, arranged parallel to the vertical axis. The base is a confused mixture of dirty brown augite and feldspar, with iron in considerable amount. The specimen (33) from a dike in the upper part of the Ka- liuwaa Valley is a very compact, nearly black basalt, unusual in showing occasional grains of j)yrite. The feldspar is fresh, but the augite is more or less altered and its place taken by a serpentinous substance, while occasional cavities are filled with a light-colored radiating zeolitic mineral showing feeble double refraction. Besides the usual magnetic iron, which is scattered through in grains or octahedral crystals, there are also curious aggregations of iron ore in very slender rod-like forms, sometimes crossing each other at right angles, but usually matted together with a confusedly reticulated struc- ture, sometimes in spherical aggregates. Specific gravity, 2-90- Chrysolite is present very sparingly in the remaining rocks, the hand specimen showing only here and there an isolated grain, and sometimes close search is needed to detect it. They are all light bluish gray basalts, with specific gravity ranging from 2*86 to 2-01. No very close study has been made of these specimens, but with a number of them their aspect, their highly feldspathic character, and the microscopic structure made it seem as if they might more properly be- long to the andesytes ; a silica determination of one of them (36, G. = 2-86) by Mr. Wheeler gave, however, only 50-55 p. c. Si02. Several of these rocks show more or less altera- tion, and in one of them (36) the occasional crystals of chrys- olite have entirely passed into serpentine. For the most part they are highly crystalline, but one of the group (45, G-. = 2*88) shows numerous patches of a dark brown glass ; this specimen is the most highly chrysolitic of the number, it being present in minute grains among the feldspar and augite, each grain having its orientated fringe of titanic iron. No nepheline- basalt was detected among the specimens in hand. pan Cl^irD* VOLCANOES AND DEEP-SEA TOPOGRAPHY. IT htis become a question of much interest as regards the origin of volcanic phenomena, whether the profound oceanic depths which occur in the vicinity of Hawaii and near some other volcanic islands are a result in any way of the volcanic action, — either through the undermining which the discharge of the enormous amount of material needed to make mountains over thirty thousand feet in height from the ocean's bottom, and 6° to 8° in mean slope, must have occasioned if it were not prevented by a continued and full supply from beneath, or through the gravitational pressure which has been appealed to as the cause of the ascensive force. But is not this inquiry fully answered by the principle sustained by Darwin, that the regions of volcanic islands in the Pacific are areas of elevation ? It would be so if Dar- win's conclusion were right. In the study of the ocean's islands and in Darwin's account of them, the author has found no facts that sustain the conclusion. The facts serve to prove, so far as there is any general rule, only that such islands have undergone less subsidence than the area of coral islands. The longer the continuance of volcanic action the larger becomes the volcanic mountain ; and this principle is suffi- cient to account for the great elevation of the mountains of Hawaii. There is reason for believing that the fires along 358 VOLCANOES AND DEEP-SEA TOPOGKAPHY. the Hawaiian line broke out all together at some time in the long past, but only Hawaii has kept on piling up lava- streams from that remote time of outbreak until now, and hence has come the altitude of these loftiest volcanic moun- tains of the Pacific; and this in spite, it may be, of much subsidence. The question of subsidence through volcanic action and its influence on oceanic topography i.s the subject before us. Its consideration involves a general study of the origin of the ocean's deep troughs ; and this demands, as the first step, a general review of oceanic topography, — for according to recent bathyraetric investigations, the deep troughs are part of the system of topography, and its grander part. We need for this purpose an accurate map of the depths and heights through all the great area. Such a map will ultimately be made through the combined services of the Hydrographic De- partments of the civilized nations. At the present time the lines of soundings over the oceans, especially over the Pacific and Indian, are few, and only some general conclusions are attainable. It is to be noticed that the sA^stem of features of the oceanic area are involved in the more general terrestrial system ; but since the former comprises nearly three fourths of the surface of the sphere, it is not a subordinate part in that system. With reference to this discussion of the subject the author has prepared the accompanying bathj-metric map. The Bathymeteic Map, and the general Features of THE Oceanic Depression displayed by it. The Map (Plate XVI.). — In the preparation of the bathy- metric map the recent charts of the Hydrographic Depart- ments of the United States and Great Britain were used,^ * The author is indebted to the Hydrographic Departments of G-reat Britain as well as the United States for copies of these ciiarts. BATHYMETRIC MAP. 359 which contain all depths to date, and the lists of new soundings published in German and other geographical jour- nals. In order that the facts on which the bathymetric lines are based may be before the reader, a large part of the depths are given, but in an abbreviated form, 100 fathoms being made the unit : 25 signifying 2,500 fathoms or nearly (between 2,460 and 2,550) ; 2-3, about 230 fathoms ; -4 about 40 fath- oms. Only for some deep points is the depth given in full. The addition of a plus sign (+) signifies no bottom reached by the sounding.^ In the plotting of oceanic bathymetric lines from the few lines of soundings that have been made, the doubts which constantly rise have to be settled largely by a reference to the general features of the ocean, and here wide differences in judgment may exist in the use of the same facts ; but through the depths stated on the map, the reader has the means of judging for himself. In the case of an island the lines about it may often have their courses determined by those of adjoining groups or by its own trend ; but in very many cases new soundings are needed for a satisfactory conclusion. Some divergences on the map from other published bathy- metric maps require a word of explanation. The northern half of the North Pacific is made, on other deep-sea maps, 1 On the map the bathymetric lines for 1,000, 2,000, 3,000, and 4,000 fathoms, besides being distinguished in the usual way by number of dots, have been made to differ in breadth of line, the deeper being made quite heavy in order to exhibit plainly the positions of the areas without the use of colors. The line for 100 fathoms is, as usual, a simple dotted line. As the bathymetric map herewith published is necessarily small, and none of the ordinary maps of the oceans give either deep-sea soundings or a correct idea of the trends of the oceanic ranges of islands, I state here that the charts of the United States Hydrographic Depart- ment for the Atlantic, Pacific, Indian, and Arctic oceans, may be purchased of dealers in charts in the larger sea-board cities. There are several large charts to each ocean. One of the firms selling them in New York City is that of T. S. & J. D. Negus, 140 Water Street. The occasional bulletins from the Hydrographic Depart- ments of America and Great Britain and Petermann's Mittheilungen contain nearly all the new data issued for the perfecting of such a chart. 360 VOLCANOES AND DEEP-SEA TOPOGRAPHY. part of a great 3,000-fatliom area (between 3,000 and 4,000) stretching from the long and deep trough near Japan far enough eastward to include the soundings of 3,000 fathoms and over in mid-ocean along the thirty-fifth parallel. It has seemed more reasonable, in view of present knowledge from soundings, to confine the deep-sea area off Japan to the border-region of the ocean, near the Kurile and Aleutian islands, and leave the area in mid-ocean to be enlarged as more soundings shall be obtained. Again in the South Pa- cific, west of Patagonia, the area of relatively shallow sound- ings (under 2,000 fathoms) extending out from the coast is on other maps bent southward at its outer western limit so as to include the area of similar soundings on the parallels of 40° and 50°, between 112° and 122° W. The prevailing trends of the ocean are opposed to such a bend, and more soundings are thought to be necessary before adopting it. It may be added here that in the Antarctic Atlantic, about the parallel of 66^° S. and the meridian of 13i° W., a large area of 3,000 and 4,000 fathoms has b6en located. It was based on a sounding in 1842 by Captain Ross, R. N., in which the lead ran out 4,000 fathoms without finding bot- tom. The sounding was, therefore, made before the means available were '• sufficient to insure the accuracy of such deep casts." The Feature-lines of the Oceanic and Bordering Lands. The courses of island-ranges and coast-lines have a bear- ing on the question as to the courses of the deep-sea troughs, and therefore, by way of introduction, they are here briefly reviewed.^ The system of trends in feature-lines takes new ^ This subject of the system in the earth's feature-lines is presented at lenqth, with a map, in the author's " Expedition Geological Report," pp. 11-23 and 414-424 ; and also more briefly in the "American Journal of Science," 1846, 2d series, ii. 381. FEATURE-LINES OF THE OCEANIC AND LAND AREAS. 361 significance from a bathymetric map, for the courses are no longer mere trends of islands or emerged mountain peaks, they are the trends of the great mountain ranges themselves ; and in the Pacific these mountain courses are those of half a hemisphere. Some of the deductions from such a maj) are briefly as follows : — 1. Over the Pacific area there are no prominent north- and-south, or meridional, courses in its ranges, and none over the Atlantic, except the axial range of relatively shallow water in the South Atlantic. And to this statement it may pertmently be added that there are none in the great ranges of Asia and Europe, excepting the Urals ; none in North America ; none in South America, excepting a part of those on its west side. 2. The ranges in the Pacific Ocean have a mean trend of not far from northwest by west, which is the course very nearly of the longer diameter of the ocean. One transverse range crosses the middle South Pacific, — the New Zealand, — commencing to the south in New Zealand and the islands south of it, with the course N. 35° E., and continuing through the Kermadec Islands and the Tonga group, the latter trending about N. 22° E. ; and this is the nearest to north and south in the ocean, except toward its western border. 3. The oceanic ranges are rarely straight, but instead change gradually in trend through a large curve or a series of curves. For example, the chain of the central Pacific be- comes to the westward north-northwest ; and the Aleutian range and others off the Asiatic coast make a series of con- secutive curves. Curves are the rule rather than the excep- tion. Moreover, the intersections of crossing ranges, curved or not, are in general nearly rectangular. 4. Approximate parallelisms exist between the distant ranges or feature-lines ; as (1) between the trend of the New Zealand range and that of the east coast of North America ; 46 362 VOLCANOES AND DEEP-SEA TOPOGRAPHY. and also that of South America (which is continued across the ocean to Scandinavia) ; also (2) between the trend of the foot of the New Zealand boot with the Louisiade group- and New Guinea farther west, and the mean trend of the islands of the central Pacific both south and north of the equator, and also that of the north shore of South America. These are a few examples out of many to be observed on the map. 5. The relatively shallow-water area which stretches across the North Atlantic from Scandinavia to Greenland — the Scandinavian plateau, as it may well be called — is con- tinued from these high latitude seas southwestward, in the direction of the axis of tlie North Atlantic (or parallel nearly to the coast of eastern North America and the opposite coast of Africa), and becomes the "Dolphin shoal." It may be a correlate fact in the earth's system of features that a Patagonian plateau stretches out from the Patagonia coast, or from high southern latitudes, in the direction of the longer axis of the Pacific, and embraces the Paumotu and other archipelagoes beyond."^ This Patagonia plateau also extends in the opposite direction over the Falkland Islands and far beyond. The above review of the earth's physiognomy, if accom- panied In^ a survey of the map, may suffice for the main purpose here in view : to illustrate the general truths, — that s^'stem in the feature-lines is a fact ; that the system is 1 As parallelisms may have importance that is not ii<>\v apparent, I draw atten- tion to one between the Mediterranean Sea that divides Europe from Africa, and the West India (or West Mediterranean) Sea that divides North from South America. Both have an eastern, middle, and ivestern deejj basin. Their depths (see map) in the East Mediterranean, are 2,170, 2,040 and 1,585 fathoms ; in the West Mediterranean (the three being the Caribbean, the West Caribbean or Cuban, and the Gulf of Mexico), 2,804, 3,428, and 2,080 fathoms. Further, in each Mediterranean Sea, a shallow-water plateau extends from a prominent point on the south side, northward, to islands between the eastern and middle of the deep basins, — one from the northeast angle of Tunis to Sicily, the other from the northeast angle of Honduras to Jamaica and Hayti, the two about the same in range of depth of water. And this last parallelism has its parallels through geological history, even to the Quaternary, when the great mammals made mi- grations to the islands in each from the continent to the south. ORIGIN OP THE DEEP-SEA TROUGHS. 363 world-wide in its scope ; and — since these feature-lines have been successively developed with the progress of geo- logical history — that the system had its foundation in the beginning of the earth's genesis and was developed to full completion with its growth. Facts beaeing on the Origin of the Deep-sea Troughs. In treating this subject, the facts from tlie vicinity of volcanic lands that favor a volcanic origin are first men- tioned ; secondly, those from similar regions that are not favorable to such an origin ; thirdly, facts from other re- gions bearing on the question. A. Facts apparently favoring a Volcanic Origin. 1. The Pacific soundings have made known the existence of two deep-sea depressions, if not a continuous trough, loitli- in forty miles of the Hawaiian Islands, — one situated to the northeast of Oahu, or north of Molokai, with a depth of 3,023 fathoms, or 18,069 feet ; and the other east of the east point of Hawaii, 2,875 fathoms, or within 750 feet of 18,000 feet. Again, 450 miles northeast of Oahu, there is a trough in the ocean's bottom, over 800 miles long, which runs nearly parallel with the group and has a depth of 3,000 to 3,540 fathoms ; and, as far south, another similar trough of prob- ably greater length has afforded soundings of 3,000 to 3,100 fathoms. The depths about the more western part of the Hawaiian chain of islands have not yet been ascertained, and hence the limits of the deep areas are not known. Such depths, so close to a line of great volcanic mountains, the loftiest of the mountains not yet extinct, appear as if the}' might have resulted from a subsidence conseqnent on the volcanic action. The subsidence might have taken place (1) either from 364 VOLCANOES AND DEEP-SEA TOPOGRAPHY. underminings, which the amount of matter thrown out and now constituting the mountain chain, with its peaks of 20,000 to 30,000 feet above the sea-bottom, shows may be large ; or (2) from the gravitational pressure in the earth's crust about a volcanic region which speculation makes a source of the ascensive force and of the upward rising of the lavas, — the subsiding crust following down the liquid surface beneath. In either case the mass of ejected material might be a measure more or less perfect of the maximum amount of subsidence. 2. In the western part of the North Pacific, at the south end of the volcanic group of the Ladrones, off the largest island of the group, Guam, the ''Challenger" found a depth of 4,475 fathoms, one of the two deepest spots yet known in the Pacific. The situation with reference to the group is like that off the east end of the Hawaiian group. 3. In the South Pacific, not far southwest of Tongatabu, the largest island of the Tonga or Friendly group, depths of 4,295 and 4,428 fathoms were obtained in soundings by Capt. Pelham Aldrich, of H. M. S. " Egeria," in latitudes 24° 49', 24° 37' S., and longitudes 175° 07', 175° 08' W. In latitude 24° 00' and longitude 175^ 16' the depth found was 3,692 fathoms; in 24° 27' and 176° 15', 530 fathoms; in 23° 12', 175° 40', 596 fathoms.^ 4. East of Japan and the Kuriles, a region of ranges of volcanoes, there is the longest and deepest trough of the ocean, first made known by the soundings of the United States ship " Tuscarora ; " the length is 1,800 miles, the depths 4,000 to 4,650 fathoms ; and farther northeast, south of one of the Aleutian Islands, a depth of 4,037 fathoms oc- curs again, also obtained by the "Tuscarora;" and depths of 3,100 to 3,664 fathoms exist still farther east. It is prob- able that the 4,000-line trough continues from the Kuriles *• American Journal of Science, 1889, xxxvii. 420, and Bulletin of the British Hydrographic Department of February, 1889. ORIGIN OF THE DEEP-SEA TROUGHS. 365 to this deep spot off the Aleutian volcanic range ; and if so, the length of the trough is over 2,500 miles. The map is made to suggest its extension still farther eastward ; but among the few soundings made off the more eastern Aleu- tians, the deepest are 3,664 and 3,820 fathoms, near longi- tude 165° W. The latter was obtained hy the "Albatross," of the United States Fish Commission, in 1888, in latitude 52° 20' N. and 165° W. Farther west the '■ Albatross " found, in latitude 52° 18' N. and longitude 163° 54' W., a depth of 2,848 fathoms; in 52° 20' N., 166° 05MY., 2,654 fathoms; in 52° 40' N., 166° 35' W., 2,267 fathoms. — indicating, as the report states, that the depression of 3.000 to 3,820 fathoms is not continued w^estward. Other similar facts may be found on the map ; and still others may exist which are not now manifest, owing to the sinking of oceanic areas and islands. But no cases can be pointed out which are more decisively in favor of volcanic origin. B, Facts from the A'icinity op VolcaxNic Regions apparently NOT REFERABLE TO A YOLCANIC ORIGIN. The ocean off the western border of North and South America affords striking examples of the absence of deep troughs from the vicinity of regions eminently volcanic. The South American volcanoes are many and lofty ; and still the ocean adjoining is mostly between 2,000 and 2,700 fathoms in depth ; and just south of Valparaiso, it shallows to 1,325 fathoms. The only exception yet observed is that of a short trough of 3,000 to 3,368 fathoms, close by the Peruvian shore. It may, however, prove to be a long trough, al- though certainly stopping short of Valparaiso. The waters, however, of the Pacific border of both South and North America deepen abruptly compared with those of the At- lantic border ; and the significance of this fact deserves consideration. 366 VOLCANOES AND DEEP-SEA TOPOGRAPHY. The facts off Central America are more remarkable than those off the coast to the south. The volcanoes are quite near to the Pacific coast, and still the depths are between 1,500 and 2,500 fathoms. The condition is the same off the west coast of North America. Of the two areas of 3,000 or more fathoms nearest to the east coast of the North Pacific, one is 600 miles distant in tlie latitude of San Francisco, and the other is w^ithin ten degrees of the equator and twenty degrees of the coast ; both are too far away to be a con- sequence of volcanic action in California, Mexico, or Central America. In the North Atlantic the European side lias its volcanoes, and has had them since the Silurian era, and yet the non- volcanic North American side of the ocean has far the larger areas of deep water and much greater mean depth. The Azores or Western Islands, which are all volcanic, have depths around them of only 1,000 to 2,000 fathoms and no local troughs. Iceland, the laud of Hecla, is in still shal- lower waters, with no evidence of local depressions off its shores. Tlie Canaries are volcanic, Imt no deep trough is near them. c. Facts from Regions not Volcanic which are unfavorable TO THE Idea of a Volcanic Origin. 1. In tlie North Pacific, near its centre, the area of 3,000 or more fathoms about 35° N. ; the two similar but smaller areas toward its eastern border ; the areas north of the Carolines, in the western part of the ocean ; the broad equa- torial area about the Phoenix Group ; the area in the South Pacific in 170° W., east of Chatham Island, and another just south of Australia, — are all so situated tha.t no reason is apparent for referring them to a volcanic origin. Some of the areas are in the coral-island latitudes, and the supposed volcanic basis of coral islands makes a volcanic origin pos- ORIGIN OF THE DEEP-SEA TROUGHS. 367 sible ; but their probable size and position appear to favor the idea of origin through some more fundamental cause. The area in the South Pacific, east of Chatham Island, is 450 miles distant from the land. The border of southern Australia, abreast of the deep-sea trough, has no known volcano. 2. 1)1 tlte Atlantic away from the West Indies. — The 3,000- fathom areas of the North and South Atlantic — that is, the three in the North Atlantic, the two in the South Atlantic, and the two equatorial, one near the coast of Guinea and the other near that of South America — occupy positions that sug- gest no relation to volcanic conditions. The Cape Verdes, north of the equator, are partly encircled by one of the deep areas, somewhat like the eastern end of the Hawaiian group ; but this bathymetric area appears to be too large to owe its origin directly to volcanic work in the group. The coast of Guinea near the 3,000-fathom area has nothing volcanic about it, and the opposite coast of South America, near an- other, is free from volcanoes. The only facts in the Atlantic that suggest a volcanic origin are the depression of 2,445 fathoms within forty miles of the west side of the volcanic Cape Verde Archi- pelago, and that of 2,060 fathoms within twenty miles of Ascension Island ; and a connection is possible. 3. In and near tlte West Indies. — The most remarkable of the depths of the Atlantic area are situated in and near the region of the West Indies, as is well illustrated and discussed by Mr. Alexander Agassiz in his instructive work on the '' Three Cruises of the Blake." The deepest trough of the ocean (4,561 fathoms) occurs within seventy miles of Porto Rico ; and yet this island has no great volcanic mountain, though having basaltic rocks. By the north side of the Bahama belt of coral reefs and islands, for 400 miles, as Mr. Agassiz well illustrates, the depth becomes 2,600 to 3,000 fathoms within twenty miles of the coast-line, and at 368 VOLCANOES AND DEEP-SEA TOPOGRAPHY. one point 2,774 within eight miles, a pitch-down of 1:2-5; and nothing suggests a volcanic cause for the abrupt descent. Cuba and Hayti are not volcanic, and look as if they were an extension of Florida, so that no grounds exist for assuming that the Bahamas rest on volcanic summits. One of the strangest of 3,000-fathom troughs is that which commences off the south shore of eastern Cuba, having there a depth of 3,000 to 3,180 fathoms. It is within twenty miles of this non-volcanic shore, and nearly three times this distance from Jamaica. No sufficient reason appears at pres- ent for pronouncing its origin volcanic. It is continued in a west-by-south direction to a point beyond the meridian of 85° W., or over 700 miles, making it a very long trough, and the depths vary from 2,700 to 3,428 fathoms. The depression extends on into the Gulf of Honduras, carrying a depth of 2,000 fathoms far toward its head, and in a small indenta- tion of the coast it, stops ; for nothing of it appears in the outline of the Pacific coast or the depths off it, and nothing in the range of volcanic mountains on the coast. Against the three deepest parts of the trough there are (1) the Grand Cayman reef, twenty miles north of a spot 3,428 fathoms deep ; (2) banks in 13 and 15 fathoms within fifteen miles of a depth of 2,982 fathoms ; and (3) Swan Island reef, fifteen miles south of a depth of 3,010 fathoms ; the first of the three indicating a slope to the bottom of 1 : 5, and the last of 1 : 4-4. Why these greatest depths in the trough, so abrupt in depression, should be on one side of shoals or emerged coral reefs, it is not easy to explain ; and the less so that the part of the trough south of Cuba has nothing volcanic near by in the adjoining mountain range, and the fact also that the westernmost end of the trough extends on for 175 miles, and there has a depth of 3,048 fathoms with 2,000 fathoms either side and no coral reefs. ORIGIN OF THE DEEP-SEA TROUGHS. 369 D. ArRANGEIMENT OP" THE DeEP-SEA TROUGHS IN THE HaLVES OF THE Oceans pointing to some other than a Volcanic Origin. The ivcstern half of the Atlantic and Pacific oceans con- tains much the larger part of the 3,000-fathom areas and all the depths over 4,000 fathoms. In the North Atlantic the areas of 3,000 and over in the western half, or off the coast of the United States, are very large ; and the bathy- metric line of 2,500 fathoms extends westward nearly to the 1,000-fathom line. This important feature can be ap- preciated for both oceans from a look at the map, without special explanations. As a partial consequence of this arrangement, the Pacific, viewed as a whole, may be said to have a westward sloj)e in its bottom, or from the South American coast toward Japan. This westward slope of the bottom exists even in the area between New Zealand and Australia, — the ocean in this area being shallow for a long distance from the coast on the east side and deepening to 2,500 - 2,700 fathoms close to that non-volcanic land, New South Wales or eastern Australia. In the Atlantic the slope is in the direction of its northeast- southwest axis, either side of the Dolphin shoal, but espe- cially the western side, rather than from east to west, it commencing in the Scandinavian plateau and ending in tlie great depths adjoining the West Indies. Owing to the system in the Atlantic topography, the Dol- phin Shoal — the site of the Atlantis of ancient and modern fable — is really an appendage to the Eastern Continent (that is, to Europe), and is shut off by wide abyssal seas from the lands to the west that have been supposed to need its gravel for rock-makins;. But the view that the west half of an oceanic basin is always the deepest becomes checked by finding in the In- dian Ocean that the only areas that are 3,000 fathoms deep or over are in the eastern part of the ocean, off the north- 47 370 VOLCANOES AND DEEP-SEA TOPOGRAPHY. west coast of Australia, and near western Java and Sumatra. The greatest depths in its western half, or toward Africa, are 2,400 to 2,600 fathoms.i Conclusions. 1. The facts reviewed lead far away from the idea that volcanic action has been jDi^edominant in determining the po- sition of the deep-sea troughs. It has probably occasioned some deep depressions within a score or two of miles of the centre of activity, ]:)ut beyond this the great depths have probably had some other origin. 2. It is further evident that the deep-sea troughs are not a result of superficial causes of trough-making. Erosion over the ocean's bottom cannot excavate isolated troughs. The coldest water of the ocean stands in the deep holes or troughs instead of running, as the reader of Agassiz's volume has learned. The superficial operation of weighting the earth's crust with sediment, or with coral or other organic-made limestone, and filling the depressions as fast as made, much appealed to in explanations of subsidence, has not produced the troughs ; for filled depressions are not the kind under consideration. Moreover, the areas are out of the reach of continental sedi- ments, and too large and deep to come within the range of possibilities of organic sedimentation or accumulation. The existence of the troughs is sufficient proof of this. The deep troughs of the West Indian and adjoining seas are in a region of abundant pelagic and sea-border life, and j^et the marvel- ^ In the Arctic seas, going north from the Scandinavian platean, the vrater deepens north of the hititude of IceUxnd, l)et\veen Greenland and Spitzbergen, to 2,000 fathoms, and farther north to 2,650 fathoms, in the longitude nearly of Green- wich ; and it is probable that the 2000-fathom area extends over the region of the North Pole. The continents of Europe (with Asia probably) and North America are proved, by the shallow soundings over the adjoining Arctic seas and the islands or emerged land, to extend to about 82|-'' N., which is about 450 miles from the pole. ORIGIN OF DEEP-SEA TOPOGRAPHY. 371 lous depths exist. And the depths of the open oceans are no less without explanation. Those close by the Bahamas, extending down to sixteen and eighteen thousand feet, are evidence of great subsidence from some cause ; and the coral reefs for some reason have manifestly kept themselves at the surface in spite of it. o. If superficially acting causes are insufficient, we are led to look deeper, to the sources of the earth's energies, or its in- terior agencies of development, to which the comprehensive system in its structure and physiognomy points. Whatever there is of system in the greater feature-lines, whether marked in troughs or in mountain chains or island ranges, must come primarily from systematic work within. The work may have been manifested in long lines of flexures or fractures as steps in the process, but the conditions which gave directions to the lines left them subject to local causes of variation, and between the two agencies the resulting physiognomy has been evolved. We have from the Pacific area one observation of a vol- canic nature bearing on the comprehensiveness of the system of feature-lines in the oceans ; and although I have already referred to it, I here reproduce the facts for use in this place. If the ranges of volcanic islands were, in their origin, lines of fissures as a result of comprehensive movements, the lines should continue to be the courses of planes of weakness in the earth's crust. The New Zealand line, including the Ker- madec Islands and the Tongan group, has been pointed to as one of these lines, and one of great prominence, since it is the chief northeastward range of the broad Pacific, and nearly axial to the ocean. The series of volcanoes along the axis of New Zealand is in the same line. It was noticed, at the Tarawera eruption of 1883, that four or Jive days after the outbreak, and three after it had subsided, White Island, in the Bay of Plenty, at the north end of the New Zealand series, became unusually active ; and two months later there 372 VOLCANOES AND DEEP-SEA TOPOGRAPHY. was a violent eruption in the Tonga group, on the Island of Niuafou. The close relation in time of the latter to the New Zealand eruption is referred to by Mr. C. Trotter, in " Nature " of Dec. 7, 1886.' May it not be that these dis- turbances were due to a slight shifting or movement along a series of old planes of fractures, successively from south to north, and hence that even now changes of level may take place through the same comprehensive cause that determined the existence of the earth's feature-lines? Owing to the long distance of the Tonga group from New Zealand, an affirma- tive reply to the question cannot be positively made ; but there is probability enough to give great interest to this branch of geological inquiry. * American Journal of Science, 1887, xxxiii. 311. DENUDATION OF VOLCANIC ISLANDS ; ITS AMOUNT A MARK OF AGE. SINCE the evidence from denudation of the lapse of time is, as already shown, a subject of much geological in- terest, and one discussed at length in the author's " Expedi- tion Geological Report," some facts and conclusions are here cited from it, especially those with regard to the island of Tahiti, of the Society Group, and the Hawaiian Islands. The island of Tahiti has nearly the shape, as regards out- line, of the figure 8, and was once a twin of volcanoes. Only the northern and larger of the two peninsulas is often visited, and to that the following remarks refer. It was originally a gently sloping cone of the type represented by the Hawaiian volcanoes ; for its beds of lavas, as seen in the sides of the valleys, slope at a small angle toward the shores ; mostly 3° to 10" — varying in some parts to 15° — on the north and west sides, where the author's examinations were made. Supposing the mean slope to be 8°, the height above the sea-level of the original cone — the diameter of the island being twenty miles — would have been nearly seventy-five hundred feet. It probably much exceeded this ; for the greatest height at the present time, according to an imper- fect measurement made by Lieut. W. M. Walker, U. S. N., of the Wilkes Exploring Expedition (who took as a base a line measured on the coral reef near Matavai), is about seven thousand feet. 374 DENUDATION OF VOLCANIC ISLANDS. The old cone is now a dissected mountain ; the dissector was running water. Valleys cut profoundly into its sides and lay bare the centre to a depth of from two thousand to nearly four thousand feet (by estimate) below the exist- ing summit ; and the deep valleys crowd on one another, owins; to the extent of the erosion. The topographic features of the island are shown on the accompanying map. This map is a copy m the main of that in Captain Wilkes's ''Narrative" of the Expedition; — in the main, because changes have been made by the author, removing some of the imperfections introduced by the art of the map-maker or engraver and his want of knowledge of the region. This liberty would not have been taken, were it not that part of the map was originally from a sketch by the author, communicated to the Hydrographic Department of the Expedition. This sketch comprised the northern third of the island, from the centre outward, between the Papenoo and Punaavia valleys, and was prepared from personal ol)- servations in the valleys of the region, obtained on an ascent of Mount Aorai, one of the two highest peaks, but without a proper survey beyond a few bearings. Being the only person of the Expedition who made the ascent, no other one had the opportunity for so comprehensive a view of the ridges and valleys of that part of the island. Of the central peaks, the highest, at a on the map, made seven thousand feet in height by Lieutenant Walker's measurement, is called Orohena ; the next highest, about five hundred feet lower, at 6, is the one called Aorai. The island in its present condition, as the map shows, is an admirable model of a deeply denuded or water-sculptured mountain-cone. To appreciate the precise conditions under which the denudation went forward, it has to be borne in mind that the waters from the rains and clouds are most abundant about the summits and higher portion of the DENUDATION OF VOLCANIC ISLANDS. 375 island, and are there perpetually at work. In these upper parts, therefore, or above fifteen hundred feet, forests and shrubbery cover the ridges and valleys wherever there is a foothold : but toward the coast, or below a level of one Map of Tahiti, tlie corul-reefs excluded; the lower side is the northern, or that toward the equator : PP, village of Papenoij ; M, of Matavai ; P, of Papaua ; T, of Toanoa ; P', of Papieti, the largest ; P", of Punaavia. The valleys are named from the villages on the coast at their termination. thousand to fifteen hundred feet, the slopes, down to the grove-clad border-plain of the island, are grass-covered and look bare in the distant view. The following are the features due to the erosion : — 1. The ridges and valleys are arranged nearly radially. 376 DENUDATION OF VOLCANIC ISLANDS. 2. The highest peaks are about the centre. 3. The valleys terminate for the most part near the sea- level instead of extending deeply beneath it, as is proved by the fact that the outline of the island is nearly even, instead of being indented with deep bays. 4. The larger of these valleys abut at their heads against the central peaks in lofty precipices, — precipices of two to nearly four thousand feet. Some of the larger val- leys are widest at the centre of the island and terminate under the peaks in vast amphitheatres. 5. The ridges toward the borders of the island are somewhat broad-backed, but over the interior very narrow. Above an elevation of three thousand feet or so (as I found in my ascent), the top edge of tlie ridges for much of the way is but three or four feet wide, — too thin to be repre- sented on a map of so small a scale as the above ; and in some spots it diminishes to a foot, and even, at times, to a thin edge of bare rock ; and from the crest the declivities either side pitch off steeply one to two thousand feet. 6. Within a mile or two of ihe central peaks erosion has reduced the height of some of the narrow ridges a thousand feet or more, or still further lowered and thinned them until dwindled to a mere pinnacled wall at the base of the peaks. A view of a portion of one of these thinned- down ridges (called, on the island, the Crown) is here intro- duced. The ascent of one of the highest peaks is possible only along a ridge that has kept unbroken its con- nection with the summit, and an experienced guide is needed to make sure of the right and safe way. M^^m^fi ill ii-/-a The " Crown " at the head of the Papiete Valley. DENUDATION OF VOLCANIC ISLANDS. 377 Some incidents connected with the author's ascent of Aorai will make the facts better appreciated : ^ — " We commenced the ascent by the ridge on the west side of the Matavai Valley, and, by the skilfulness of our guide, were generally able to keep the elevated parts of the ridge without descending into the deep valleys which bordered our path. An occasional descent and a climb on the op- posite side of the valley were undertaken ; and although the sides were nearly perpendicular, it was accomplished with- out much difficulty, by clinging from tree to tree, with the assistance of ropes, at times, where the mural front was otherwise impassable. By noon of the second day we had reached an elevation of five thousand feet, and stood on an area twelve feet square, the summit of an isolated crest in the ridge on which we were travelling. To the east we looked down two thousand feet into the Matavai vallev ; to the west a thousand feet into a branch of the Papaua valley, the slopes either way being from sixty to eighty degrees, or within thirty degrees of perpendicular. On the ^ On the excursion I had with me only two Tahitians. The ascent was made after Captain Wilkes had left Tahiti with his vessel, the " Vincennes," and hence the mistaken statement in his " Narrative " that I was accompanied by others of the expedition. Very few of the natives then living had ever been to the summit of this moun- tain, and great difficulty was found in obtaining a guide acquainted with the route. Paths led as lar as the Feiis, or mountain plantains, an elevation of one thousand to fifteen hundreil feet ; but beyond this the tops of the ridges are mostly covered with a wiry brake (Gleichenium), which grows in some places to a height of ten feet, and is almost impenetrable. In order to pass through it, we had to break it down by throwing our bodies at full length upon it or by diving into it ; or, where too high to admit of this mode of progress, we had recourse to burrowing, pushing aside and breaking oft" its crowded stems, and thus we dug our way for rods. In addition to the brake, the shrubbery often formed a dense thicket, impassable ex- cept with a hatchet. These obstacles made progress slow ; and without a native tc lead the wa}^ the jaunt, difficult in itself, would have been quite impracticable in the five days allotted to it. Another discomfort on the route was the want of water, which, after a few days of dry weather, is seldom to be found in the valleys near the summit. A traveller in the mountains of Tahiti should go well provided against this inconvenience. We found dew from the leaves a great luxury ; and the news that water had been found in a valley created a sensation of pleasure scarcely describable. 48 378 DENUDATION OF VOLCANIC ISLANDS. side of our ascent, and beyond, on the opposite side, our peak was united with the adjoining summit by a thin ridge, reached by a steep descent of three hundred feet. This ridge was described, by our natives, as no wider at top than a man's arm ; and a fog coming on, they refused to attempt it that day. The next morning being clear, we pursued our course. For a hundred rods the ridge on which we walked was two to four feet wide, and from it we looked down on either side a thousand feet or more of almost perpendicular descent. Beyond this the ridge continued narrow, though less dangerous, until we approached the high peak of Aorai. This peak had appeared to be conical and equally accessible on different sides; but it proved to have but one place of approach, and that along a wall with precipices of two to three thousand feet, and seldom exceeding two feet in width at top. In one place we sat on it as on the back of a horse, — for it was no wider. — and pushed ourselves along till we reached a spot where its width was doubled to two feet, and, numerous bushes again affording us some security, we dared to walk erect. We at last stood perched on the sum- Peaks of Orohena, with Pitoiiiti to thk left. (As seen from the summit of Aorai.) mit edge, not six feet broad. The ridge continued beyond for a short distance, with the same sharp, knife-edge char- acter, and was then broken off by the Punaavia valley. Our height afforded a near view of Orohena ; it was sepa- DENUDATION OF VOLCANIC ISLANDS. 379 rated from us only by the valley of Matavai, from whose profound depths it rose with nearly erect sides. The peak is saddle-shaped, and the northern of the two points is called Pitohiti/ These summits, and the ridge which stretches from them toward Matavai, intercepted the view to the southward. In other directions the rapid succession of gorge and ridge that characterizes Tahitian scenery was open be- fore us. At the western foot of Aorai appeared the Crown. Beyond it extended the Punaavia valley, the only level spot in sight ; and far away, in the same direction, steep ridges, rising behind one another with jagged outline, stood against the western horizon. To the north, deep valleys gorge the country, with narrow precipitous ridges between ; and these melt away into ridgy hills and valleys, and finally into the palm-covered plains bordering the sea. " On the descent we followed the western side of the Papaua valley, along a narrow ridge, such as has been de- scribed, only two or three feet wide at top, with precipices either side of not less than a thousand feet. Proceeding thus for two hours, using the bushes as a kind of balustrade though occasionally startled by a slip of the foot one side or the other, our path suddenly narrowed to a mere edge of naked rock, and, moreover, the ridge was inclined a little to the east, like a tottering wall. Taking the upper side of the sloping wall, and trusting our feet to the bushes while cling- ing to the rocks above, carefully dividing our weight lest we should precipitate the rocks and ourselves to the depths below, we continued on till we came to an abrupt break in the ridge of twenty feet, half of which was perpendicular. By means of ropes doubled around the rocks above, we in turn let ourselves down, and soon reached again a width of three feet, where we could walk in safety. Two hours more at last brought us to slopes and ridges where we could breathe freely." ^ The sketch on page 378 is from the author's note-book of 1839 ; it was not used in his Report. 380 DENUDATION OF VOLCANIC ISLANDS. The peculiarities here described characterize all parts of the island. Toward the high peaks of the interior the ridges which radiate from or connect with them become mere mountain walls with inaccessible slopes, and the val- leys are from one to three thousand feet in depth. The central peaks themselves have the same wall-like character. It is thus with Orohena and Pitohiti, as well as Aorai ; and owing to the sharpness of the summit edge, rather than the steepness of the ascent, Orohena is said to be quite inaccessible. Now contrast this dissected volcanic mountain v/ith those of the Hawaiian Islands : ^ — "Mount Loa, whose sides are still flooded with lavas at intervals, has but one or two streamlets over all its slopes, and the surface has none of the deep valleys common about other summits. Volcanic outflows have kept its surface essentially even, and by its continuation to this time, the waters have had scarcely a chance to make a beginning in denudation. Mount Kea, which has been extinct for a long period, has a succession of valleys on its windward or rainy side which are several hundred feet deep at the coast and gradually diminish upward, extending in general about one half or two thirds of the way to the summit. But to westward it has dry declivities, which are comparatively even at the base, with little running water. A direct connection is thus evinced between a windward exposure and the existence of valleys. And we observe also that the time since volcanic action ceased is approximately or relatively indicated ; for it has been long enough for the valleys to have advanced only part-way to the summit. Degradation from running water would of course commence on such slopes, — that is, the wind- ward slopes, — at the foot of the mountain, where the waters are necessarily more abundant and more powerful in denud- 1 Pages 379-392: " On the Origin ot the Valleys and Ridges of the Pacific Islands." DENUDATION OF VOLCANIC ISLANDS. 381 ing action, in consequence of tlieir gradual accumulation on their descent. '^ Haleakala, or eastern Maui, offers the same facts as Mount Kea, indicating the same relation between the features of the surface and the climate of the different sides of the island. On eastern Oaliu the valleys are much more exten- sive ; yet still the slopes of the original cone may be in part distinguished. And thus we are gradually led to Kauai, where the valleys are very profound and the former slopes can hardly be made out. The facts are so progressive in character that all must be equally attributed to the running water of the land. The valleys of ]Mount Kea, extending some thousands of feet up its sides, sustain us in saying that time only is required for explaining the existence of any similar valleys in the Pacific. " The Report adds the following in explanation : — "Suppose a mountain sloping around like a volcanic dome of the Pacific. The excavating power at work proceeds from the rains or condensed vapor, and depends upon the amount of water and rapidity of slope. The transporting force of flowing water as shown by Hopkins increases as the sixth power of the velocity, — double the velocity giving sixty-four times the trtinsporting power. Hence, if the slopes are steep, the water gathering into rills excavates so rapidly that every growing streamlet ploughs out a gorge or furrow ; and con- sequently the number of separate gorges is very large, and their sizes comparatively small, though of great depth, — a condition well illustrated on northeastern Maui. The exca- vation above, for a while, is feeble in amount; the waters accumulate as they descend, causing, especially during the rainy seasons, the denudation to be greatest below, and in this part the gorge or valley most rapidly forms. In its progress it enlarges from below upward, though also increasing above, while at the same time the many tributaries are making lateral branches. Toward the foot of the mountain the 382 DENUDATION OF VOLCANIC ISLANDS. excavating power gradually ceases when the stream has no longer m this part a rapid descent, — that is, whenever the slope is not above a few feet to the mile. The stream then consists of two parts, the torrent of the mountains and the slower waters below, and the latter is gradually lengthening at the expense of the former. " After the lower waters have nearly ceased excavation, a new process connnences in this part, — that of widening the valley. The stream, which here effects little change at low water, is flooded in certain seasons, and the abundant waters act laterally against the inclosing rocks. Gradually, through this undermining and denuding operation, the narrow bed be- comes a flat strip of land between lofty precipices, through which, in the rainy seasons, the streamlet flows in a winding course. The streamlet, after the flat bottom of the valley is made, deposits detritus on its banks, which in some places so accumulates as to prevent an overflow of the banks by any ordinary freshet. Such is the origin of the deep channels with a riband of land at bottom that cut through the di- viding plain of Oahu, and which are common toward the shores of many of the Pacific islands. " The torrent part of the stream, as it goes on excavating is gradually becoming more and more steep. The rock- material operated upon consists of layers of unequal hard- ness, varying but little from horizontality while dipping to- ward the sea, and this occasions the formation of cascades. AVhenever a softer layer wears more rapidly than one above, it causes an abrupt fall in the stream : it may be at first but a few feet in height ; but the process begun, it goes on with accumulating power. The descending waters in this spot add their whole weight, as well as a greatly increased velocity, to their ordinary force ; and the excavation- below goes on rap- idly, removing even the harder layers. The consequences are, a fall of increasing; heio-ht, and a basin-like excavation di- rectly beneath the fall. Often, for a short distance below. DENUDATION OF VOLCANIC ISLANDS. 383 the stream, moves quietly before ru.shing again on its torrent course ; and when this result is attained by the action, the height of the* fall has nearly reached its limit so far as exca- vation below is concerned, though it may continue to increase from the gradual wear and removal of the rocks over which it descends. " As the gorge increases in steepness, the excavations above deepen rapidlj^ — the more rapid descent more than compen- sating, it may be, for any difference in the amount of water. Moreover, as the rains are generally most frequent at the very summits, the rills in this part are kept in almost constant action through the year, while a few miles nearer the sea they are often dried up or absorbed among the cav- ernous rocks. The denudation is consequently at all times great about the higher parts of the valley, especially after the slopes have become steep by previous degradation, and finally an abrupt precipice forms its head. " The waters descending the ridges either side of the valley, or gorge, are also removing these barriers between adjacent valleys, and are producing, as a first effect, a thinning of the ridge at summit to a mere edge ; and as a second, its partial or entire removal, so that the two valleys may at last be separated only by a low wall, or even terminate in a common head, — a ivide amjy/iitheatre enclosed hy the lofty r}%ountams. In one case the ridge between the two valleys, which toward the shores of the island has rather a broad back, high up in the region of mists and frequent rains becomes a narrow wall, and thus connects with the central summit. In the other, the ridge finally terminates abruptly, and a deep valley separates it from the main mountain. '•' We have here to remember that these mountain streams at times increase their violence a million-fold when the rains swell the waters to a flood. There is everything favorable for degradation which can exist in a land of perpetual sum- mer : and there is a full balance ag-ainst the frosts of colder 384 DENUDATION OF VOLCANIC ISLANDS. regions in the exuberance of vegetable life, since it occasions rapid decomposition of the surface, covering even the face of a precipice with a thick layer of altered rock, and with spots of soil wherever there is a chink or shelf for its lodgment. The traveller ascending a valley on one of these islands on a summer day, when the streams are reduced to a mere rill which half the time burrows out of sight, seeing the rich foliage around, vines and flowers in profusion covering the declivities and festooning the trees, and observing scarcely a bare rock or stone excepting a few, it may be, along the bottom of the gorge, might naturally question with respect to the agents which had channelled the lofty mountains to their base. But tliough silent, the agents are still on every hand at work : decomposition is in slow but constant j)rogress ; and the percolating waters are acting internally if not at the surface. Moreover, at another season, he would find the scene changed to one of noisy waters careering over rocks and plunging down heights w^ith frightful velocity. Then the power of the stream would not be disputed." The Report concludes with the remark : — " With literal truth, therefore, we may speak of the valleys of the Pacific islands as the furrowings of time, and read in them marks of age. We learn from such facts how com- pletely the features of an island may be obliterated by this simple process ; that even a cluster of peaks like Orohena, Pitohiti and Aorai of Tahiti may be derived from a simple volcanic dome or cone. Mount Loa contains within itself the material from which an island like Tahiti might be modelled that should have nearly twice its height and four times the geographical extent." Great denudation on the leeioayxl side of an island is an exception to the usual rule. It is a consequence, on Oahu, of the sharp-crested twenty-mile precipice facing to the wind- ward} The trade-winds become chilled on striking the 1 See page 282 and Map on Plate XIII. DENUDATION OF VOLCANIC ISLANDS. 885 summit of the precipice, and ready, therefore, to drop their moisture ; but as they are moving on, they get beyond the summit before much of the moisture falls, and so the lee- ward slopes receive the water. In the upper part of the Nuuanu valley, within two miles of the paU, one hundred and thirty-two inches of rain fall a year, and nearly one hun- dred inches less than this at Honolulu, although brief sprink- lings occur almost daily over the city. Konahuanui and Lanihuli, in the view from Honolulu, are generally under clouds ; but from Kaneohe, they are usually imcovered. A nearly similar condition exists in West Maui, owing to the thinness of the rocky walls at the head of its great val- leys. Very broad valleys are consequently made there on the leeward side, as in Oahu, as shown on Plate XII. ; but these valleys end below rather abruptly in a slender gulch, which may be, for the most of the year, a "dry run;" the ex- cessively dry and hot airs of the lower plains carrying away the water and supplying almost none. This subject of denudation and the making of valleys is so well illustrated, also, by the facts which the author observed in New South Wales in the interval between his visit to Tahiti in 1839 and to the Hawaiian Islands in 1840, that a few additional pages are here cited from his Report.^ " The great depth, extent, and number of the vallej^s of New South Wales are calculated to excite wonder and per- plex us much in the study of their origin. In some of these sandstone regions the gorges intersect the country in endless succession, and are alike in their inaccessible precipices of one, two, or three thousand feet. They are deep gulfs, with walled sides, composed of horizontal layers of sandstone. These layers seem once to have been continuous ; and what is the force which has thus channelled the mountain struc- ^ Pages 526-532 : on " Degradation of the Rocks of New South Wales and Formation of the Valleys." 49 386 DENUDATION OF VOLCANIC ISLANDS. ture ? Are they ^ stupendous rents in the bosom of the earth ? ' ^ Are they regions of subsidence ? Can it be that they were ijever filled, but were depressions left between the heaps of accumulating sediment that constitute the sand- stone, which depressions were afterwards enlarged by the sea during the elevations of the land ?^ Or may we adopt the ' preposterous ' idea that simple running water has been the agent ; and if so, was it fresh water or that of the ocean ? " The forms of these valleys are as remarkable as their ex- tent. Major Mitchell states that Cox River rises in the vale of Clywd, 2,150 feet above the sea, and leaves this expanded basin through a gorge 2,200 yards wide, flanked on each side by rocks of horizontally stratified sandstone 800 feet high : here it joins the Warragamba. Some of its tributaries rise at a height of 3,500 feet above the sea, and the ravines they occupy cover an area of 1,212 miles. From this he calculates that one hundred and thirty-four cuhic miles of stone have been removed from the valley of the Cox.^ " The facts observed by us are sufficient to substantiate the general conclusion of Major Mitchell. The Kangaroo valley is another example of a valley two to three miles in width, and a thousand to eighteen hundred feet deep, opening out- ward through a comparatively narrow gap ; and by a rough calculation from our own examinations and the map of Ma- jor Mitchell, the amount of rock necessary to fill the valley is equivalent to a rectangular ridge twelve miles long, two miles wide, and two thousand feet deep. This is but a small example, however, compared with those of the interior. Mr. Darwin remarks upon this peculiarity of form, — their extent and width and many branches, yet narrow openings at their lower extremity ; and he observes that the same is the char- acter of the bays along the coast. 1 Count Strzelecki, in his " New South Wales and Van Diemen's Land," p. 57. - Darwin, in his " Volcanic Islands," p. 137. 8 Mitchell's Expedition into Australia, ii. 352. DENUDATION OF VOLCANIC ISLANDS. 387 " The ideca that runnmg water was the agent in these openi- tions appears not so ' preposterous ' to us as it was deemed by Mr. Darwin, and we think that Major Mitchell was right in attributing the effects to this cause. The extent of the results is certainly no difficulty with one who admits time to be an element which a geologist has indefinitely at command. We need but refer to the facts from the Pacific islands to show that New Holland, after all, is not the most remarkable land in the world for valleys of denudation. "We should consider that the rock material is far more yielding than that of basaltic Tahiti. Indeed the whole rock, from the uppermost layer to the deposits below the coal, is remarkably fragile, considering the age of the de- posits, crumbling readily, and often breaking without diffi- culty between the fingers ; and besides it is much fissured. Even the harder fossiliferous Wollongong rock, as has been described, falls to pieces of itself when exposed to the air. Moreover, there are occasionally clayey or argillaceous lay- ers which are still softer ; and many of those of the coal formation are not firmer than the material of a common clay-bank. The denudation of such material requires no preparatory decomposition, as with many igneous rocks, but takes place from wear alone, and wiih but slight force in the agent. " It is obvious, for the same reason, that the material car- ried off by denudation ought not to appear in fragments through the lower country. A short journey along a rapid stream would reduce even large masses to powder. The plains of the Kangaroo valley are covered in places with basaltic pebbles or bowlders ; but the sandstone, which is the prevailing rock along the bed of the stream and in the en- closing hills, has scarcely a representative pebble in the de- bris. The sandstone blocks are worn to sand and earth by the torrents, while the harder basalt is slowly rounded. On the plains of Puenbuen similar facts were apparent. The 388 DENUDATION OF VOLCANIC ISLANDS. hills contain sandstone and basalt, but only the latter ap- pears as bowlders or pebbles over the plains, or along the streams below. " This Sydney sandstone does not even require running water to promote degradation. In many caverns along cliffs, the rock gradually falls to pow^der by a species of efflorescence. There are numerous instances of this along the coves of Port Jackson, where the crystallization of the saline spray reduces the rock to its original sand ; and in the interior of the country there are large caves, formed apparently by this same process, though probably from the .crystallization of nitrates. Near Puenbuen, these caves are from six to twenty feet deejD, and from four to forty long. The roof is arched, and appears to be constantly crumbling, while the bottom is covered with a fine, dry, ash-like sand, into which the feet sink several inches. The same operation is going on along the summits of the Illawarra range ; and one huge block was found so hollowed out in this way as to be a mere shell, which sounded under the hammer like a metallic vessel. " These various facts bring; before us some idea of the yielding nature of the rock which the waters have to con- tend with in the denudation of this country, and they also illustrate the various processes at w^ork. We allude to a single other mode of degradation before passing : it is the action of growing trees and their roots, both in opening fissures and tumbling blocks down the precipices. It is a cause influencing very decidedly the characters of cliffs, and at the same time preparing the rock for decomposition and wear. " The credibility of the view here favored is further sus- tained by the character of the streams. The great ex- tent of the floods and the rapid rise of the rivers attending them have been alluded to. The stream of the Kangaroo Grounds, when visited by the writer, was a mere brook, DENUDATION OF VOLCANIC ISLANDS. 389 fordable in any part ; and it flowed along with quiet miir- murinirs. But a few weeks before the brook was a river thirt}' feet deep, driving on in a broad torrent, and flooding the valley. If, as has been shown, the transporting power of running water increases as the sixth power of the velo- city, and a stream of fifteen miles an hour has more than ten times the transporting power of one moving ten miles an hour, and more than a million times that of a stream of two miles an hour, we can comprehend how inadequate must be the conceptions of this force which we derive from view- ing the streams at low water. " This rise in the Kangaroo Grounds is an index of what takes place every few years over the whole countr3^ Sur- prise at the amount of degradation subsides before such facts ; we rather wonder that sandstones so soft and fragile, which have been exposed probably from the Oolitic period, still cover the surface to so great an extent as they do at the present time. " Mr. Darwin derived his principal argument against the hypothesis of denudation from the forms of the valleys, — their width, extent, and ramifications, and yet narroiu em- bouchures. But we find on consideration that this form is a necessary result of the mode of denudation under the cir- cumstances existing. In the account of the valleys of the Pacific islands it has been shown that the gorges change their character where the slopes become quite gradual, from a narrow defile with convergent sides to a broad channel with vertical walls and flat bottom. The same cause should produce a like effect in Australia. A stream, in making a descent of two or three thousand feet from the higher sum- mits to the level of the sea, gradually deepens its bed by wear. Since the waters are increasing in quantity from various sources as they flow onward, this deepening of the gorge should be most rapid at its lower extremity ; and it would continue in progress until the bed in that part be- 390 DENUDATION OF VOLCANIC ISLANDS. came so low or gradual in slope, that the waters had lost to a large degree their eroding force, and any excavation at bottom was made up by the material deposited along its course. This fact determines a permanent height for the bottom of the lower valley. As the stream continues its wearing action in the same manner, the lower valley is gradually prolonged upward, retaining nearly the same slope at bottom (one or two feet to the mile) ; consequently the steeper portion of the gorge is at the same rate becoming shorter and still steeper. Thus the head of the stream may finally become a series of cascades, or, as happens at times in the Pacific, it may be reduced mostly to a single cascade of a thousand feet or more. " The progress of this change may be better understood from the f olio win o; diao:ram : — Ai — B A B C D is the rock to be cut through by the stream. Suppose denudation to produce first the course C n^. The stream is filled, as is commonly the case, by lateral channels and rills down the sides of the gorge, as well as by the main source ; and the amount or depth of water is thus in con- stant increase, as it flows onward. Denudation is conse- quently most rapid the farthest from the head, or toward n^ ; the valley, tlierefore, increases in depth in this part till the slope has l^ecome so gentle here as to counterbalance the greater amount of water, at which point the bottom of the valley ceases to increase in depth ; in this condition v^ n^ be- comes the bottom of the lower valley, and C n^ the steeper portion above it. In the same manner the valley bottom continues to prolong at nearly the same slope, and C u^, C n*, C 71^ become successively the course of the stream DENUDATION OF VOLCANIC ISLANDS. 391 descending into it. And even C if' is not an exaggeration of possibilities, for many examples of it are met with. '' But the results explained are but a part of the actua-l course of things in these regions of horizontally stratified rock. As on Oahu and elsewhere, when the denudation at bottom has reached its limit, the waters exert but little degrading power except during floods, and this takes place by the sides of the overflowing stream; at the same time depositions of detritus take place along its banks. The result is that the rocks bounding the valley are worn away below, and are often undermined ; the valley widens at bottom to a flat plain, while the enclosing wall by the pro- cess becomes nearly vertical. A narrow riband of land be- tween high precipices of rock is therefore a necessary result of the action. " Degradation still continues along the upper or steep part of the main stream, and also along the many streamlets and rills pouring down the valley's sides ; and in each of these streamlets there is a tendency to produce below a flat-bot- tomed valley. The consequence is that they increase the width and extent of the main valley-plain ; for whenever they become thus flat-bottomed, they contribute to its lateral enlargement. " At the same time the bluffs at the lower extremity, or em- bouchure, of the main valley remain without much change, since the denudation is mostly confined to the vicinity of the streamlets alluded to, and these streamlets are most abun- dant above, they being produced and fed mainly by the rains in the higher parts of the mountains. It is natural enough, therefore, that the valleys should not only become flat below and precipitous in their sides, but also that they should widen least at their lower extremity. We see, consequently, no necessity of appealing to any other cause than that of run- ning water to account for the most stupendous results in Australia. 392 DENUDATION OF VOLCANIC ISLANDS. '• It has been supposed that the sea has been largely con- cerned in the denudation which has produced the Australian valleys. We find no reason for attributing any of the val- leys to this source, although it is possible that some modifi- cations may thus have resulted. The facts at Port Jackson are a sufficient reply on this point. The cliffs of the estuary actually undergo very little change from the action of its waters, and are far more altered by the mode of efflorescence described and by rills of running water ; and such action as is exerted tends to remove headlands instead of deepening the coves. " The proper action of the sea is seen in the character of the sandstone shores of East Australia, and especially in the wide platform of rock below high-tide level lying at the foot of lofty cliffs. This platform is a simple projection of the lower layer of the cliff' ; from above it, the waves have carried away the rock to a distance inward of fifty to one hundred and fifty yards. At Port Jackson, Newcastle, and WoUono-onu; Point are fine exhibitions of it." NOTE ON HAWAIIAN PRONUNCIATION. The follovvins;- rules comprise nearly all that is essential for correctness in the pronunciation of Hawaiian words, except on one point, — that of accentuation : — 1. Sound the vowels as in Italian, and the consonants (eight in number, A, k. I, m, )i, J), t, w) as in English, except ?o, the pronunciation of wliich is between that of w and v. 2. Make as many syllables in a word as there are vowels. The word Hawaii is not an exception, although the distinction of the closing sylla- bles might not be perceived by one unfamiliar with tiie spoken language. Turn has two syllables, ICa-tc; Kilauea has five, Ki'la-ii-e'a; but the second and third are nearly blended in the pronunciation. 3. Never make a syllable end with a consonant. Thus, Ilo'no-lu'lu is right, not Hon' o-hc' lit ; Ha'le-a'ka-la, noi Hal' e-ak'a-la. In Hawaiian all words as well as syllables end in a vowel, and two consonants have always a vowel between them. 4. An apostrophe between two vowels implies that a Jc is dropped, and that an interruption of the voice is there required in pronunciation, — as in Halemauma''u. INDEX. A A, features of, 9, 33. formation of, 192, 206, 241. Abich, M., eruption of Vesuvius in 1834, 267. Adams, O. B., Mount Loa crater in 1873, 201. Agassiz, A., Three Cruises of the Blake, 367. Alexander, J. M., map of Mokuaweo- weo, 40, 181. cataracts of lava at Mount Loa crater, 237. volcanoes over cross-fissures, 263. Alexander, W. C.,on Kilauea in 1833, 56, 57. Alexander, W. D., Surveyor-General, maps of the Islands, 27, 270. trip up Haleakala, 270. Allen, O. D., analysis of scoria crust of Kilauea, 163. Analyses of rocks, 163, 342, 348. Andesyte, 6, 353. Andrews, Dr. L., Mount Loa crater in 1843, 185. Arctic Sea, depths of, 370. Ascensive force, 16, 170. Ashes, volcanic, 1. Atlantis, 369. Augite, in lavas, 4. feathery, in Hawaiian lavas, E. S. Dana, 319. Australia, denudation in, 385. Bahamas, depths near, 368. Baker, E. P., eruption of 1868, 89. Kilauea in 1889, 123. Baker, E. P., source of lavas of 1852, 188; of eruption of 1880-1881, 205. Mount Loa crater in 1885, 210; in 1888, 215. lava-stalactites with bent ends, 210. collections of rocks, 318, 335, 346. Baldai-san eruption, 253. Basalt, 6. Basaltic structure, 7. Basalt-volcano, 142. Basic and acidic rocks, 146. Bathymetric map, 358. Bingham, H., on Kilauea, 55. Bird. Miss Isabella L., Mount Loa cra- ters in 1873, 199. Bird Island, 317. Bishop, A., 38, 47. Bishop, S. E., survey of Oahu, 285. survey of Bird Island, 317. rocks of Western Maui, 351. Black Ledge in Kilauea, 34, 46, 127. Blow-holes, Blowing-cones, 17, 49, 58, 71. Boiling action in Kilauea. 68, 153, 159. lava-lakes of 1840, 69. Bombs, so-called, 10, 245. Brigham, William T., memoir by, 40. Kilauea in 1864-1865, 85; in 18G8, 89; in 1880, 96. map of Kilauea, 84, 134, 138. on formation of Pele's hair, 160. Mount Loa in 1851, 186; in 1864, 193; in 1880, 203, 204. on lava-stalactites, 341. on vapors, 155 50 394 INDEX. Budd, Thomas A., Lieut., depth of Kilauea, 67. Byron's Voyage and Journal, 37, 50, 54. Carbonic acid, 8. Castle, S. N., Kilauea in 1837, 59. Caves in lava-stream near Hilo, 209. in elevated coral-reef, Oahu, 303, Challenger Expedition, Mount Loa in 1875, 202. Chamberlain, L., on Kilauea, 53. Chase, Captain, Kilauea in 1838, 59. Cheever, H. T., Island World of the Pacific, 81. Chrysolite of lavas, 6, 298, 324, 327, 343. Cinders, 1, 7. Cinder-cones, 3, 13, 279. Coan, T., publications of, 38. 40. on Kilauea in 1840, til ; in 1844, 1846, 74, 76; in 1848, 80; in 1851, 81; in 1853; 81; in 1855, 82; iu 1856-1858, 83; in 1862, 84; in 1863, 85; in 1866, 88; in 1868, 89; in 1869, 1871, 1872, 92; in 1874, 94; in 1879, 95. Mokuaweoweo in 1843, 185; in 1849, 185; in 1851, 186 ; in 1852, 186: in 1855, 189; in 1859, 193; in 1865, 194; in 1868, 194; in 1872-1874, 197-199; in 1875-1877, 202; in 1880, 203; in 1881, 204, 205. map of Kilauea in 1844, 75. Coan, T. Munson, on Kilauea in 1855. 82. Cohen, analyses by, 348. Columnar basalt. 7. Conduit, volcanic, 15, 151. Cones, forms of, 11, 13. cinder-made, 3. cinder, in Haleakala, 279 ; of Oahu, 292. debris, in Halema'uma'u, Coan, 170, 171; in 1887, 103, 11.3, 119, 130; views of, 107, 111. 121. lateral, 13, 22, 245. tufa, 14; of Nanawale, 64; of Oahu, 292. Copper sulphate, or copper vitriol, at the sulphur-banks of Kilauea, 73. Crater, characters and origin of, 1, 149, 230. work within, 16, 20, 23, 153, 222, 265. Cummings, Miss C. F. Gordon, Kilauea in 1879, 95. Dampier, R., sketch of Kilauea by, 38. 52. Dana, E. S., petrography of Hawaii, 318; of Maui, 349; of Oahu, 353. Darwin, valley-making in New South Wales, 386. Daubree, A., entrance of water to vol- canic conduit, 158. Debris-cones, 103, 113, 119, 130, 170, 171. destruction of, 176. Deep-sea troughs and topography, 360. origin of, 363. Denudation of volcanic islands, 373; of Tahiti, 373 ; of Hawaiian Islands, 380; of New South Wales, 385. cause and methods of, 381, 386. Diabase, 6. Diamond Head, 282, 293. Dibble, I., eruption of 1789, 41. Dioryte, 6. Dissociation iu liquid lava, 158. Dodge, F. S., paper of, 41. map of Kilauea, Plate HI., 34, 106. Kilauea in 1886-1888, 106, 109. sections of Halema'uma'u in 1888, 120. size of Keanakakoi and Kilauea- iki, 66. Doleryte, 6. Dolphin .shoal, 362. Douglas, David, publications of, 38. on Kilauea, 57-59. Mount Loa in 1834, 183. Drayton, J., sketch of Kilauea, 32, 136. plan of Haleakala, 274. Driblet-cone, 17, 71, 85, 147. Driblet-cones, making of, 160. Dutton, C. E., report of, on Hawaiian volcanoes. 140 Kilauea in 1882, 97. Mount Loa in 1882, 210. INDEX. 395 Earth's feature-lines, comprehensive character of, 371. Earthquakes, 22. of Hawaii in 1868, 89, 231; of 1886, 98, 99; of 1887.211. agency in eruptions, 231. of Mount Loa, discharging Ki- lauea, 231. Effluent discharges, 2, 169. Eld, Henry, Lieut., depth of Kilauea, 67. on Mount Loa crater, 183. Ellis, William, Journal of , 35. sketch of Kilauea by, 46, 47, 50. Emerson, J. S., paper of, 41. Kilauea in March, 1886, and map, 100, 101, 106. Erosion. See Denudation. Eruptions, submarine, 2. subaerial, 3. of Kilauea in 1823, 45 ; 1832, 55; 1840, 61; 1868, 88; 1886, 98. . periodicity or not of, 124. dependence on rains, 125. of Mount Loa in 1832, 180 ; 1843, 185; 1852, 186; 1855, 189; 1859, 191; 1868, 194; 1877, submarine, 202; 1880-1881, 204; 1887, 211. characteristics and causes of, 15, 21, 228, 230. explosive, 23 ; of Kilauea in 1789, 41 ; of Tarawera, 246 ; of Kraka- toa, 249; of Baldai-sau, 253. Fault-planes, 174. Felsyte, 5. Flames in Kilauea, Brigham, 88, 96. observed in 1887, 119. Floating island of 1838, 60. of 1882-1886, 98-100. disappearance of, 176. Fountains in summit crater of Mount Loa, 198, 199, 201, 203, 219, 223, 225. of Mount Loa eruptions in 1852, 187; 1859,191; 1868,195; 1887, 212, 236. Fouque, dissociation of elements, 8. Fuller, Mount Loa eruption of 1852, 187. Fumaroles, 3. Fusibility of rocks, 7, 144. effect of, on volcanic action and on forms of cones, 12, 143. Gabbro, 6. Gases, volcanic, 7. Glass, volcanic, 4, 330. Glauber salt, 8, 228. Goodrich, Joseph, letters of, 38, 53-55. Granite, 5. Granulyte, 5. Gravitational pressure, effects of. 179, 235. Gi-een, William L., Vestiges of the Molten Globe, 41. eruption of 1859, 192. eruption of 1868, 196. Mount Loa crater in 1873, 200. on source of Mount Loa fountains, 225. theory of the origin of the earth's features, 263. Gulick, O. H., Kilauea in 1863, 84. Gypsum, 8, 73. Hale.\kala, features of, 273. Drayton's map of, 273. action ending in cinder-ejections, 274, 279. last eruption of, and origin of crater, 277. a solid mountain, according to Preston's pendulum experiments, 279. Halema'uraa'u, first mention of name by Count ytrzelecki, 60. sections of 1S86-1S88, Dodge, 120. See, further, Kilauea. Haskell, R. V., Mount Loa ei'uption of 1859, 191. Hawaii, general features, 28. Hawaiian Islands, features of, 25. • publications on, 35. origin of, 259, 261. deep-sea troughs near, 363. denudation in, 380. rocks of, E. S. Dana, 318. Hawes, G. W., analysis by, 163. ;96 INDEX. Heat, loss of, in conduit, 16. Heights of Hawaiian mountains, 25. Hematite, 7. Hillebrand, William, Kilauea in 1868, 89, 233. Hilo, 29. Hitchcock, C. H., projected stones about Kilauea, 43. Mount Loa crater in 1883, 210. Kakuku eruption of 1888, 196. Hitchcock, D. W., Mount Loa in 1870, 197 ; in 1888, 214. eruption of 1880-1881, 204. formation of aa, 206. Hitchcock, E, G. and H. R., Mount Loa crater in 1873,201. Honolulu. 282. Hualalai, Mount, 28. Hydi'ostatic pressure, etfects of, 179, 235. Jackson, J. C, aiialy.sis of a lava- stalactite, 342. Jocelyn, S. S., engraver of the first sketch of Kilauea, 36. Johnston-Lavis, on bombs, 11. Jones, George, earthquakes of 1887, 211. Journal of the Mission Deputation of 1823, 35. Judd, Dr. G. P., on Mount Loa crater, 183. Kaliuw'aa, on Oahu, 287. Kauai, features of, 305. structure of, 306. lateral cones, 309. elevated sand-hills, 316. Kea Range in the Hawaiian Islands, 127. Keanakakoi, 66. Kilauea, view of, Drayton's, 32; El- lis's, 46, 47, 50; Dampier's, 52; Chase ♦ and Parker's, 60; Perry's, 87. Map of. Lieutenant Maiden's, 51 ; Wilkes's, 66, 133, 135; Lyman's, 79: Brigham's, 84, 134, 138; Lydgate's, 93, 94. floor of, and other interior features, 34. Kilauea, eruption of 1789, 41, 95, 249; 1823, 45; 1832, 55; 1840, 61, 67; 1868, 98; 1886, 98. a basalt-volcano, 142. cycle of movement in, 141. lava-column, size of, 151. ordinary work of, 153. lifting of floor of, C. Lyman, 76. 170. lifting of floor of Ilalenia'uma'u, Dodge, 109, 120; source of ascen- sive action, 175. contrast with Vesuvius, 34, 265. relation to Mount Loa, 258. rocks of, E. S. Dana, 342. Kilauea-iki, 60. Kinney, H., eruption of Mount Loa, 1852, 187. Kohala Range, 28. Krakatoa, 249. Kiukenberg, C. Fr. W., on Pele's hair, 161. Labradokite, 6. Laccolitlis, Laccolites, 15. Ladrones, great depth near Southern, 364. Lapilli, 18. Lateral cones, origin of, 245. Lava, 1, 4. See, further. Rocks. Lava-streams, 9, 114. rate of flow of, Coan, 189. Leucite, Leucite-rock, 5. Limonite, 7. Loa Range, 27. Loomis, E., Kilauea in 1824, 54. Lydgate, map of Kilauea, 93, 94. Lyman, Chester, Kilauea in 1846, 76. debris ridge of Kilauea, in 1846, 77, 139. ascensive action, 78, 170. map of Kilauea, 79. Lyman, E. E., conflict of lava-streara and water-stream, 206. Lyman, F. S., Mount Loa, fountain of, "l852, 188. Kilauea in 1868, 89, 194. Lyons, C. J., Kilauea in 1878, 94. Lyons, L., eruption of 1859, 101. INDEX. 397 Maby, J. H., Kilauea in 1886, 98. Maiden, Lieutenant, map of, 38. Map of Hawaii, frontispiece; of Ha- waiian Islands, 26, 261; of Kilauea (see Kilauea) ; of Mokuaweoweo, 40, 181; of Maui, 271; of Oahu, 283; of Tarawera region, 247 ; of Tahiti, 37.5. bathymetric, 358. Marcasite, 8. Maui, description of, 269. map of, 271. eccentric form of craters, 281. rocks of, E. S. Dana, 349. west, crater of, 280. drift-sand ridge, 282. Merritt, VV. C, summit of Mount Loa in 1888, 215. Metamorphic action, 178. Metamorphisrn in connection with vol- canic action, exemplified in the sta- lactites and in ejected blocks, 254. Microlites of lavas, E. S. Dana, 331. Mitchell, Major, valleys of New South Wales, 386. Mokuaweoweo. See Mount Loa. Mount Loa, map of cratei-, of J. M. Alexander, 181; of Wilkes, 184; de- scription of, 180. eruption of 1832, 180; 1843, 185; 1852, 186; 1855, 189; 18.39, 191; 1868, 1877, submarine, 202; 1880- 1881, 204; 1887, 211. periodicity in eruptions, 217. relation to seasons, 219. ordinary activity, including lava- fountains hundreds of feet in height, 221, 222. rate of flow of lavas, 238. heights of place of outbreak and relations to diameters of crater, 229, 230 cause of eruptions of, 235. form of dome due to volcanic ac- tivity, 2.56. rocks of, E. S. Dana, 319. Narrati\e of the Mi.ssion Deputation of 1823, 35. New South Wales, denudalion. 385, New Zealand, explosive eruption of, 246. range of islands, 361, 371. Nichols, J. W., Kilauea in 1874, 94. Nihoa, island of, 317. Nordhoff, Northei-n California, Oregon, and the Sandwicli Islands, 90. Oahu, features of, 282, 285. precipice of, 282, 288, 290. tufa-cones of, 292, 299. salt lake of, 297. evidence of change of level. 302. artesian borings, 293. Obsidian, 5. Oceanic depths about the Hawaiian Isl- ands, 363. topography, Pacific, 360, 363, 366; Atlantic, 365, 367, 369; Arctic, 370. Olivine. See Chrysolite. Pacific Ocean topography, 860. Pahoehoe, 9, 33. formation of, 192. Pal agon ite, 7, 292. Paris, T. D., Mount Loa, eruption of 186S, 194. Parker; Captain, Kilauea in 1838, 59. Patagonian plateau, 362. Pele's hair, first mention of, Ellis, 48. formation of, in 1840, 70; in 1880, 160. description of, 160, 161, 348. Pericentric action, 1. Perry, sketch of Kilauea, of 1864, 87. Phacolite, 328. Pickering, C, eruption of Kilauea, 64. on Halema'uma'u in 1840, 68, 73. Pitchstone, 5. Pit-craters, 33. Polynesian Researches, Ellis. 36. Porphyry, 5, 6. Preston, E. D., pendulum experiments on Haleakala, 279. Prestwich, J., Water in Volcanic Erup- tions, 157. Projectile action, 21 ; cause of, 16, 17, 158. eruption of Kilauea, 41. Pumice, 5, 42. 198 INDEX. Punchbowl, 282, 292. Pyrite, 8. QuARTZ-syenyte, 5. Quartz-trachyte, 5. IvKD iron-oxide, 7. lihyolyte, 5, 7. Richardson, Mount Loa in 1865, 194. Rocks of Hawaiian Islands, E. S. Dana, 318. basaltic, 319. specific gravit}' of, 320. feathery forms of augite in, 320. chrysolite of, 324, 327, 343. cavities having minute crystals of labradorite and augite, 326. glassy lavas, 33U. the heavier chrysolitic, independent of altitude, 347. degree of crystalline texture de- pends on rate of cooling and not a maik of geological age, 314 of Kilauea, E. S. Dana, 342, 348, glass often absent or nearly so. 347. of Mount Loa, 819. of Oahu, 259, 353. ejected blocks, about Kilauea. 344. relations of Kilauea rocks and those of Mount Loa summit. 347. ScACCHi, A., on Vesuvius, 265. Scandinavian plateau, 362. Scoria, scoriaceous lava, 9. origin of, 162. thread-lace, 163. Shepherd, Capt. John, R. N., 61. Silvestri, on Hawaiian rocks, 318, 348. Solfntara, 3, 8, 73, 228. Soundings, oceanic, 360. Stalactites of Kilauea in 1840, 71: in 1864, Brigham, 86. of cave near Hilo, 209; E. S. Dana, 332. Stewart, C. S., publications of, 37, 52, 55. Strzelecki, publications of, 39, 60. Strzelecki, valley-making in New South Wales, 386. Sulphur-banks of Kilauea, 73. Sulphurous acid, 8. Superfluent discharges, 2. 169. Syenyte, 5. Tacchini, on Hawaiian rocks, 318. Tahiti, interior mountains of. 313. denudation of, 373. ascent of Mount Aorai, 377. Trachyte, 5, 7. Tufa,V. Tufa-cones, 14, 292, 299. Tufa-hills near Nanawale, 64. Valleys. See Denudation. Van Slyke, L. L., paper of, on Kilauea in 1886, 41, 102. Vapors, of fresh-water origin, 155, 224, 225. effects of, in volcanic action, 154. expansive force of, 161. Vaudi-ey, eruption of 1859, 191. Vesicles, origin of, 20, 161. Vesiculation, mechanical effects of, 168. amount of moisture required for, 166. Volcanic aslies, 1. gases, vapors, 1. rocks, 4; glass, 4, 7. action, 2, 15. eruptions. See Eruptions. cones, forms of, 11. islands, denudation of, 373. mountains, interior of, 312. Volcano, characters of, 1. Volcanoes in lines, 27. not safety-valves, 264. of Hawaii and Vesuvius, contrasts and resemblances, 265. Volcanoes and deep-sea topography, 3.57. Walker, W. M., Lieut., height of Tahiti peak, 373. Water, actions of, in the conduit of a volcano, 167. in eruptions, 169. INDEX. 399 Water, for volcanic action, sources of, 19, 155. fresh, source of high projection of liquid lava on Hawaii, 223, 225. amount required for vesiculation, 166. action of vapor of, or steam, 7, 16, 19. West India Seas, depths in, 367. and Mediterranean, parallelism between, 362. Wheeler, H. L., composition of lavas, 350, 354. White Island, New Zealand, 248, 371. Whitney, H. M., eruption of 1868, 89, 195; of 1877, 202. Wichmann, on Hawaiian rocks, 318. Wilkes, Charles, Capt. (later, Admiral), Narrative of, 39, 62, 66, 67. measurements of Kilauea, 67. on Mount Loa, 183. map of Tahiti, 374. University Press : John Wilson & Son, Cambridge.