ffl IN MEMORIAM ffl 
 
 MARIVSJ'SPINELLO 
 
 1874-19O4 
 
 INSTRVCTOR IN ROMANCE 
 
 LANGVAGES IN THE 
 
 VNIVERSITY OF 
 
 CALIFORNIA 
 
 1902-4 
 
 DONO 
 AMICORVM 
 
// 
 
 -& 
 
NEW 
 
 TEXT-BOOK 
 
 OF 
 
 GEOLOGY 
 
 DESIGNED 
 
 FOR SCHOOLS AND ACADEMIES. 
 
 BY 
 
 JAMES D. DANA, Li,.D., 
 
 AUTHOR OF "A MANUAL OF GEOLOGY," "A SYSTEM OF MINERALOGY," OF REPOST8 
 
 OF WTLKES'S EXPLORING EXPEDITION ON GEOLOGY, ZOOPHYTES, AND 
 
 CRUSTACEA, "CORALS AND CORAL ISLANDS," ETC. 
 
 JFourtfj iEtJitton, 
 
 REVISED AND ENLARGED. 
 
 WOODCUT8. 
 
 \ 
 
 NEW YORK I CINCINNATI : CHICAGO 
 
 AMERICAN BOOK COMPANY 
 
 FROM THE PRESS OK 
 IVISON, BLAKEMAH & COMPANY. 
 
Entered, according to Act of Congress, in the year 1868. 
 
 BY THEODORE BLISS & CO., 
 
 in the Clerk's Office of the District Court of the United States for the EaSten 
 District of Pennsylvania. 
 
 Entered according to Act of Congress, in the year 1874. 
 
 BY IVISON, BLAKEMAN, TAYLOR, & CO., 
 in the Office of the Librarian of Congress, at Washington. 
 
 Copyright, 1883, 
 
 BY IVISON, BLAKEMAN, TAYLOR, 
 
PREFACE. 
 
 IN preparing this Text-book of Geology, the general plan 
 of my Manual has been retained. The science is not made 
 a dry account of rocks and their fossils, but a history of the 
 earth's continents, seas, strata, mountains, climates, and liv- 
 ing races ; and this history is illustrated, so far as the case 
 admits, by means of American facts, without, however, over- 
 looking those of other continents, and especially of Great 
 Britain and Europe. 
 
 In this FOURTH EDITION, fifty pages have been added to 
 the size of the work, in order to render the explanations 
 simpler and more complete, and to give also a fuller account 
 of the kinds of life which contribute to rock-making, of the 
 geographical distribution of marine species, and of the depths 
 of the seas. Each of these topics is illustrated by new cuts, 
 and the last by a general map showing the depth of the 
 Atlantic and Pacific oceans by bathymetric lines, based 
 mainly on that of Mr. H. N. Moseley, of the Challenger 
 expedition. The map of the vicinity of Naples is from 
 Murray's Handbook. 
 
 135480 
 
iv PREFACE. 
 
 No glossary of scientific terms is inserted, because the 
 volume is throughout a glossary, or a book of explanations 
 of such terms, and it is only necessary to refer to the Index 
 to find where the explanations are given. 
 
 The teacher of Geology, and the student who would ex- 
 tend his inquiries beyond his study or recitation-room, is 
 referred to the Manual for fuller explanations of all points 
 that come under discussion in the Text-book, including 
 a more complete survey of the rock-formations of America 
 and other parts of the world, with many sections and details 
 of local geology, a much more copious exhibition of the 
 ancient life of the several epochs and periods and of the 
 principles deduced from the succession of living species on 
 the globe, a more thorough elucidation of the depart- 
 ments of Physiographic and Dynamical Geology, a chap- 
 ter on the Mosaic Cosmogony, a large number of addi- 
 tional illustrations, with references to authorities and per- 
 sonal acknowledgments, besides a general chart of the 
 world. 
 
 The Text-book departs from the Manual in introducing 
 the subject of Dynamical Geology before that of Historical 
 Geology. This order has the advantage of supplying the 
 student early in the course with a knowledge of the forces 
 and operations in nature by which geological progress has 
 gone forward. It has, at the same time, its disadvantages, 
 inasmuch as the facts abou^ the earth's strata must be 
 
PREFACE. V 
 
 learned before the questions as to methods of formation 
 can be fully appreciated. These difficulties are so great 
 as regards the subject of mountain-making, that the study 
 of Chapter VI., under Dynamical Geology had better be 
 deferred until that of the Historical Geology is completed. 
 
 NEW HAVEN, CONN., September 1, 1883. 
 
TABLE OF CONTENTS. 
 
 INTRODUCTION 1 
 
 PART I. Physiographic Geology. 
 
 1. General Characteristics of the Earth's Features ...... 6 
 
 2. System in the Earth's Features 14 
 
 PART II. Structural Geology. 
 
 I. PETROLOGY, OR THE CONSTITUTION OF ROCKS 20 
 
 1. General Observations on their Constituents 20 
 
 2. Kinds of Rocks 29 
 
 II. CONDITION, STRUCTURE, AND ARRANGEMENT OF ROCK-MASSES 39 
 
 Stratified Condition . 44 
 
 1. Structure 44 
 
 2. Positions of Strata 50 
 
 3. Order of Arrangement of Strata 58 
 
 PART III. Dynamical Geology. 
 
 I. LIFE 62 
 
 A. Formative Effects 62 
 
 1. Kinds and Sources of Materials 63 
 
 2. Geographical Distribution of Marine Life 70 
 
 3. Peat Formations 75 
 
 4. Coral Reefs 77 
 
 B. Protective and Destructive Effects 80 
 
 II. CHEMICAL ACTION OF THE AIR AND WATERS 82 
 
 III. THE ATMOSPHERE 86 
 
 IV. WATER 90 
 
 1. Fresh Waters 90 
 
 2. The Ocean . . , 106 
 
vnii CONTENTS. 
 
 IV. WATER (continued). 
 
 3. Freezing and Frozen Waters, Glaciers, Icebergs 115 
 
 4. Formation of Sedimentary Strata 122 
 
 V. HEAT . . 124 
 
 1. Sources of Heat 124 
 
 2. Effects of Heat 128 
 
 1. Expansion and Contraction 128 
 
 2. Igneous Action and Results 130 
 
 3. Metamorpliism 145 
 
 4. Formation of Veins 150 
 
 VI. MOVEMENTS IN THE EARTH'S CRUST : THEIR CAUSES AND CON- 
 
 SEQUENCES 156 
 
 General Considerations 156 
 
 1. Evolution of the Earth's Fundamental Features 163 
 
 2. Formation of Mountain Chains . . 165 
 
 REVIEW OF THE ANIMAL AND VEGETABLE KINGDOMS. 
 
 Distinctions between an Animal and a Plant 173 
 
 1. Animal Kingdom 174 
 
 2. Vegetable Kingdom 186 
 
 PART IV. Historical Geology. 
 
 General Observations 190 
 
 I. ARCH.EAN TIME 199 
 
 II. PALEOZOIC TIME 204 
 
 I. AGE OF INVERTEBRATES, OR SILURIAN AGE ...... 205 
 
 1. Primordial Period 206 
 
 2. Canadian and Trenton Periods 210 
 
 3. Upper Silurian Era 219 
 
 II. AGE OF FISHES, OR DEVONIAN AGE 229 
 
 III. CARBONIFEROUS AGE, OR AGE OF COAL PLANTS 240 
 
 GENERAL OBSERVATIONS ON THE PALEOZOIC 266 
 
 DISTURBANCES CLOSING PALEOZOIC TIME 276 
 
 III. MESOZOIC TIME 283 
 
 REPTILIAN AGE 284 
 
 1. Triassic and Jurassic Periods 285 
 
 2. Cretaceous Period 310 
 
 GENERAL OBSERVATIONS ON THE MESOZOIC 324 
 
CONTENTS. ix 
 
 IV. CENOZOIC TIME 329 
 
 I. TERTIARY AGE, OR AGE OF MAMMALS 330 
 
 II. QUATERNARY AGE, OR ERA OF MAN 347 
 
 1. Glacial Period 348 
 
 2. Chainplain Period 355 
 
 3. Recent Period . . 359 
 
 III. LIFE OF THE QUATERNARY . . 362 
 
 IV. GENERAL OBSERVATIONS ON CENOZOIC TIME 373 
 
 V. GENERAL OBSERVATIONS ON GEOLOGICAL HISTORY . 375 
 
 VI. CONCLUDING REMARKS , 394 
 
 APPENDIX. 
 
 A. Map of the Vicinity of Naples 398 
 
 B. Catalogue of American Localities of Fossils 399 
 
 C. Geological Implements, etc 403 
 
 D. Catalogue of Minerals and Rocks for Instruction . , 405 
 
 INDEX , . , c ....... 407 
 
INTRODUCTION. 
 
 The Science of Geology. Beneath the soil and waters of 
 the earth's surface there is everywhere a basement of rocks. 
 The rocky bluffs forming the sides of many valleys, the ledges 
 about the tops of hills and mountains, and the cliffs along 
 sea-shores, are portions of this basement exposed to view. 
 Geology is the science that studies these rocks, not merely 
 to learn about ore-beds, coal, and building materials, but pri- 
 marily to gather from them facts about the earth's history, 
 the history of its rocks, features, and life. It is an outdoor 
 science, and' out of doors are found the best instruction-places 
 for pupils and teacher. 
 
 In most of the rocky bluffs over the country the rocks lie 
 in successive beds. The beds differ in thickness and in other 
 ways. They may be all sandstone, and show the grains of 
 sand distinctly under a pocket-lens. One or more of the beds 
 may contain pebbles, smoothly worn pebbles with sand, the 
 material of a gravel bed ; another may be a slaty layer, so soft 
 and fine-grained that if ground up and mixed with water it 
 will make mud, suggesting that it might have been formed 
 out of mud. Should it be inferred, after examining such a 
 bluff, that the beds were once real sand-beds, gravel-beds, 
 mud-beds, which in some way were spread out in succession, 
 and finally became hardened, it would be a right geological 
 conclusion. 
 
 1 
 
2 INTRODUCTION. 
 
 But the questions would arise : How were the pebbles 
 rounded ? How were the mud, sand, and gravel distributed 
 in beds ? Whence the sand, pebbles, and mud ? At the foot 
 of such a bluff there commonly lie heaps of loose sand and 
 stones derived from the bluff. The rains, frost, and other 
 causes keep wearing its surface, dropping grains and tumbling 
 down fragments; and thus the heaps of debris are formed. 
 If a stream runs by the base of such a bluff, the water when 
 in rapid flow will wear it and carry off the material, grinding 
 and rounding the fallen fragments. If the bluff stands on a 
 seashore, the waves will beat against its exposed front, and 
 aid other destroying agencies in the work of reducing it to 
 sand, stones, and mud for distribution off the shore and up 
 the beach. 
 
 All over the world the exposed rocks of hills, mountains, 
 and plains are undergoing wear and decay, and becoming 
 reduced to earth and coarser loose material. And if the 
 whole world is thus engaged, and has always been at this 
 work since rocks were first exposed to the action of the air 
 and waters, there ought to have been at all times material 
 enough for the soil and the rocky beds of all periods in the 
 history. 
 
 Along the sides of a river- valley may often be seen beds 
 of unsolidified sands and gravel, with sometimes clay, consti- 
 tuting low bluffs. These bluffs may be similar in the material 
 of the beds to the rocky bluff alluded to, and the absence of 
 consolidation may be the chief difference. Up or down the 
 valley evidence may usually be found that such beds of loose 
 material are much like deposits now made by the stream at 
 high flood-level ; that the waters where rapid are always mak- 
 ing and rounding pebbles, and in flood-times are carrying 
 down stream the ground-up material for deposition below. 
 If such beds of gravel and sand are at too high levels to be 
 made by modern floods, they are sure to be within the range 
 of some greater flood of past geological time. Along a sea- 
 
INTRODUCTION. 3 
 
 shore there are often similar bluffs which the sea has made ; 
 and great sand-flats off the coast, formed from sand and peb- 
 bles drifted by the sea-currents and waves ; and rivers carry 
 to the ocean a great amount of sediment to add to the marine 
 deposits. The inference from the facts that the hard rocks 
 are only consolidated deposits, and that they were spread out 
 in beds in the same ways that beds are now formed along 
 or off seashores, in river valleys, and about lakes, is right 
 according to the fullest evidence from geological investiga- 
 tion. Nine tenths of the rocks studied by the geologist are 
 water-made rocks, and nearly all the older water-made kinds 
 are of marine origin. 
 
 Eocky bluffs often consist in part or wholly of beds of 
 limestone. At the Bermudas, about Florida, and in other 
 warm seas, the process of making limestones out of shells 
 and corals can be studied; for the process is now going on 
 as in ancient time. 
 
 The beds of a bluff may contain shells, corals, bones, or 
 plant-remains, fossils, as they are called, from the Latin 
 word fossilis, signifying dug up. Such a discovery opens up 
 a new subject. The shells or bones could not have got there 
 except when the layer containing them was forming. They 
 are like the shells in the mud or sand of existing sea-bottoms 
 or sand-beaches. If they turn out to be marine fossils, the 
 bed is of marine origin. But another lesson is taught; for 
 the fossils make known what species were living in the seas 
 when the bed was made. In a bed higher up in the series 
 the fossils may be different in kind, showing that when that 
 bed was in progress the old species had gone and new kinds 
 had corne in. In this way geology has learned much with 
 regard to the life that existed on the globe w T hen each of 
 the successive rocks was made. Taking the whole geological 
 series of rocks together from the bottom to the top, the 
 maximum thickness of which is over twenty-five miles, 
 it is found that new kinds continue to appear, and the old 
 
4 INTRODUCTION. 
 
 to disappear, on passing up from one level to another. Thus 
 a history of the life of the globe, from the simplest forms 
 of the early rocks to mammals and man, has been to some 
 extent made out. 
 
 From the above explanations it is obvious that several 
 great subjects are treated under Geology. One is the struc- 
 ture of the globe, or the arrangement and characteristics of 
 the rocks. A second is the historical succession in the for- 
 mation of the rocks. A third is the historical succession in 
 the life of the globe. A fourth is the origin of the beds of 
 rock in the earth's structure ; for the rocks that were made 
 in the deep ocean, or in shallow oceans, or along sea-beaches, 
 or in lakes, or in river-valleys, and so on, will bear some 
 peculiarities in structure or fossils that will betray their 
 origin. 
 
 Further, rocks over large areas have often been raised or 
 pushed out of their original positions and made into moun- 
 tains ; and the times of these disturbances and the origin of 
 the mountains are other subjects for geological study. And 
 such upturned rocks have sometimes become crystallized, or 
 converted into marble, granite, mica schist, and the like ; and 
 this is another of its topics. 
 
 Over the earth's surface the valleys and deep canons have 
 been made by rivers and their tributaries. And this work of 
 the waters is one part of that of rock-making; for here the 
 waters have derived much of their material. Water has 
 worked also in the state of glaciers and icebergs. 
 
 Again, in many regions the earth's crust has been deeply 
 fractured. Sometimes mineral veins have formed in the fis- 
 sures. Often melted rock, from unknown depths, has come 
 to the surface and spread widely over it, thus adding fire- 
 made or igneous rocks to the water-made. Occasionally 
 volcanoes have formed over the larger fissures ; and in a few 
 places geyser-regions, like that of the Yellowstone Park, have 
 been left as the later work of the lingering fires. 
 
INTRODUCTION. 5 
 
 The above are the more prominent subjects in Geology. 
 
 Forces of past and present time the same. The preceding 
 review teaches that the physical forces now in action have 
 been the same, and under the same laws, through all past 
 time. Whether those of the waters, the winds, heat, cohe- 
 sion, or of whatever kind, they have produced results through 
 the ages like those observed about us, with little difference 
 except from greater intensity of action in early geological 
 time. To existing nature, therefore, we safely go for the 
 means of interpreting the geological records. 
 
 Subdivisions of the Science. The four principal branches 
 of the science are 
 
 1. Physiographic Geology, treating of the earth's physical 
 features ; that is, of the system in the exterior features of the 
 earth. This department properly includes, also, the system of 
 movements in the water and atmosphere, and the system in 
 the earth's climates, and in the other physical agencies or 
 conditions of the sphere. 
 
 2. Structural Geology, treating of the rocks of the globe, 
 their kinds, structure, arrangement in beds, and various con- 
 ditions or modes of occurrence. 
 
 3. Historical Geology, treating of the successive events in 
 the history of the rocks, and of the continents, oceans, moun- 
 tains, valleys, sea-limits, climates, and life. 
 
 4. Dynamical Geology, treating of the causes, or the 
 methods, by which all the earth's changes were brought 
 about, including the making of continents, of ocean-basins, 
 of rocks, of mountains, of valleys, the causes of all variations 
 in climate, and of all changes in the earth's features, and in 
 its living species as far as open to investigation. The word 
 dynamical is from the Greek 8w/a/u9, power or force. 
 
PART I. 
 
 PHYSIOGRAPHIC GEOLOGY. 
 
 UNDER the department of Physiographic Geology only a 
 brief and partial review is here made of the general features 
 of the earth's surface. 
 
 THE EARTH'S FEATURES. 
 1. General Characteristics. 
 
 1. Size and form, The earth has a circumference of about 
 25,000 (24,899) miles. Its form is that of a sphere flattened 
 at the poles, the equatorial diameter (7,926 miles) being 
 about 26 1 miles greater than the polar. 
 
 2. Oceanic basin and continental plateaus. About eight 
 elevenths of the earth's surface, or 144,000,000 of square 
 miles, are depressed below the rest, and occupied by salt 
 water. This sunken part of the crust is called the oceanic 
 basin, and the large areas of land between, the continents or 
 continental plateaus. The area of the continents is about 
 50,000,000 of square miles ; and that of the islands, 
 2,900,000. 
 
 3. Subdivisions and relative positions of the oceanic basin and 
 continental plateaus. Nearly three fourths of the area of the 
 continental plateaus are situated in the northern hemisphere, 
 and very nearly three fifths of the oceanic basin in the south- 
 ern hemisphere. The dry land, as shown in the following 
 figure, may be said to be clustered about the North Pole, 
 and to stretch southward in two masses, an Oriental, includ- 
 
8 
 
 PHYSIOGRAPHIC GEOLOGY. 
 
 ing Europe, Asia, Africa, and Australasia, and an Occidental, 
 including North and South America. The ocean is gathered 
 in a similar manner about the South Pole, and extends north- 
 
 Fig, i. 
 
 ward in two broad areas separating the Occident and Orient, 
 namely, the Atlantic and Pacific Oceans, and also in a third, 
 the Indian Ocean, separating the southern prolongations of the 
 Orient, namely, Africa and Australasia. 
 
 The Orient is made, by this means, to have two southern 
 prolongations, while the Occident, or America, has but one. 
 This double feature of the Orient accords with its great 
 breadth ; for it averages 6,000 miles from east to west, which 
 is far more than twice the mean breadth of the Occident 
 (2,200 miles). See the following map. 
 
 The inequality of the two continental masses has its paral- 
 lel in the inequality of the Pacific and Atlantic Oceans ; for 
 the former (6,000 miles broad) is more than double the aver- 
 age breadth of the latter (2,800 miles). Thus, there is one 
 broad and one narrow continental mass, and one broad and one 
 narrow oceanic area. 
 
 The connection of Asia with Australia, through the inter- 
 vening islands, is very similar to that of North America with 
 
THE EARTH'S FEATURES. 9 
 
 South America. The southern continent, in each case, lies 
 almost wholly to the east of the meridians of the northern ; 
 and the islands between are nearly in corresponding posi- 
 tions, Florida in the Occident corresponding to Malacca 
 in the Orient, Cuba to Sumatra, Porto Eico to Java, and the 
 more eastern Antilles to Celebes and other adjoining islands. 
 It is, therefore, plain that Australia bears the same relation 
 to Asia that South America does to North America. It is 
 also true that Africa is essentially in a similar position with 
 reference to Europe. 
 
 The northern portion of the Orient, or Europe and Asia 
 combined, makes one continental area ; and its general course 
 is east and west. The northern portion of the Occident, or 
 North America, is elongated from north to south. 
 
 4. Oceanic depression and Continental elevations. The mean 
 depth of the oceanic depression is about 12,000 feet; and the 
 mean height of the land nearly one twelfth this amount, or 
 1,000 feet. The greatest depth reached by soundings (south 
 of the Ladrones) is 27,450 feet ; the greatest height on the 
 land (in Mt. Everest of the Himalayas) is 29,000 feet ; and 
 hence the interval between the extremes of altitude and 
 depression is over ten miles. If as much of the land were 
 transferred to the oceanic depression as would bring both to 
 a common level, the ocean would still have a depth of about 
 10,000 feet (Peschel). 
 
 The mean height of each, Europe, Asia, and South America, 
 is, according to estimates, about 1,130 feet; of Africa prob- 
 ably not less than 1,130 feet ; of North America, 750 feet ; 
 of Australia, 500 feet. 
 
 The mean depths of the great oceans (as calculated by 
 Haughton from recent soundings) are : of the North Atlantic 
 and North Pacific oceans, 15,000 to 15,500 feet ; of the South 
 Atlantic and South Pacific (and probably the Indian Ocean) 
 about 13,000 feet. 
 
 5. The form of the ocean's bed. The accompanying map 
 shp<vs the general form of the ocean's bed beneath the larger 
 
10 PHYSIOGRAPHIC GEOLOGY. 
 
 oceans. From north to south, along the middle of the 
 Atlantic, there is a wide zigzag ridge or plateau, conforming 
 in trend to the American coast. It lies at a depth of 6,000 
 to 12,000 feet, while on either side the bottom slopes away 
 to depths mostly between 15,000 and 20,000 feet. In the 
 small area of 4,000 fathoms and over, situated to the north- 
 west of the island of St. Thomas, the United States Coast 
 Survey steamer " Blake" found, in 1883, a depth of 27,366 
 feet. This greatest depth and the largest Atlantic area of 
 deep water exist in the western part of the ocean. 
 
 The Pacific also has a central relatively shallow plateau, 
 having the direction of its longer axis between Fuegia and 
 southeastern Asia ; and its deepest portions are in its 
 western half. One deep area is east of Japan ; another, the 
 deepest, south of the Ladrones. 
 
 Thus in each ocean the greatest depths are in the northern 
 hemisphere and toward its western border. Northward in 
 the northern hemisphere the ocean shallows rapidly. The 
 depth in Behring's Straits is not over 150 feet; and between 
 Great Britain and Iceland it does not exceed 6,000 feet, and 
 is mostly under 600 feet. 
 
 The ocean's bottom has no steep ridges like those of ordi- 
 nary mountain scenery. But broad elevations exist in some 
 parts, as found in the soundings of the " Tuscarora " between 
 the Hawaian Islands and Japan. Besides these, there are 
 many mountain ranges rising abruptly from the depths, hav- 
 ing the islands of the ocean as their emerged summits, which 
 rival in length those of the continents. The Hawaian range, 
 if the coral islands in the line of the volcanic islands are 
 included (see following map), has a length of 2,000 miles ; 
 and it rises steeply from depths of 15,000 to 18,000 feet. 
 The mountains of Hawaii have a height above the ocean of 
 nearly 14,000 feet; and a depth of 17,000 feet was found 
 but 50 miles south of the island ; this making the whole 
 height near 31,000 feet. The islands of the tropical Pacific 
 make together an island chain about 5000 miles long; 
 
THE EARTH'S FEATURES. 
 
 Fig. 2. 
 
12 
 
 PHYSIOGRAPHIC GEOLOGY. 
 
 and they are the tops of a mountain chain of this great 
 length. 
 
 6. True outline of the oceanic depression. Along the 
 oceanic borders the sea is often, for a long distance out, quite 
 shallow, because the continental lands continue on undei 
 water with a nearly level surface ; then comes, usually at 
 
 Fig. 3. 
 
 a depth of 100 fathoms or 600 feet, a rather sudden slope 
 to the deep bed of the ocean. This is the case off the east- 
 ern coast of the United States, east and south of New Eng- 
 land. Off New Jersey, as the annexed map represents, the 
 deep water begins along a line about 80 miles from the 
 shore ; off Virginia this line is 50 to 60 miles at sea ; and 
 thus it gradually approaches the coast to the southward: 
 
YHE EARTH'S FEATURES. 13 
 
 while to the northward it continues 80 to 100 miles off 
 from the New England coast, and passes far outside of 
 Nova Scotia and Newfoundland (see map, p. 11). The 
 slope of the bottom, for the 80 miles off New Jersey, is 
 only 1 foot in 700 feet. The true boundary between the 
 continental plateau and the oceanic depression is the com- 
 mencement of the abrupt slope. The same abruptness at 
 the 100 fathom line exists in the Gulf of Mexico, as pointed 
 out by J. E. Hilgard. The British Islands are situated on a 
 submerged portion of the European continent, and are essen- 
 tially a part of that continent, the limit of the oceanic basin 
 the 100 fathom line being 50 to 100 miles outside of 
 Scotland and Ireland, and extending south around the Bay 
 of Biscay. West of the British Channel the depth increases, 
 in a distance of only ten miles, from 100 fathoms to 2,000. 
 New Guinea is in a similar way proved to be a part of Aus- 
 tralia. Such facts occur on most coasts; and they teach 
 that the oceanic depression is separated from the continental 
 plateaus by a defined outline. 
 
 7. Surfaces of the continents. The surface of a continent 
 comprises (1) low lands, (2) plateaus or talk-lands, and (3) 
 mountain-ridges. The mountain-ridges may rise either from 
 the low lands or the plateaus. The plateaus are great areas 
 of the surface situated several hundred feet, or a thousand 
 feet or more, above the sea, or above the general level of 
 the low lands. They are often parts of the great moun- 
 tain chains. Sometimes plateaus include a region between 
 mountain-ridges, and sometimes the mass of the mountains 
 themselves out of which the ridges rise. For example, the 
 regions of Northern and Southern New York are plateaus 
 (the former averaging 1,500 feet in height, the latter 2,000 
 feet) situated on the western borders of the Appalachian 
 chain ; and the same is true of the Cumberland Table-land in 
 Tennessee. Between the Sierra Nevada and the Wahsatch 
 there is a plateau of vast extent, having the Great Salt 
 Lake in its northeastern portion ; its height above the sea 
 
14 PHYSIOGEAPHIC GEOLOGY. 
 
 averages 4,000 feet ; the high ranges of the Humboldt moun- 
 tains rise out of it. The eastern part of New Mexico is a 
 plateau of about the same elevation, called the Llano Esta- 
 cado; and Mexico is situated in another, from which rise 
 various ridges and peaks. The Desert of Gobi, between the 
 Altai and the Kuen-Lun range, is a desert plateau about 
 4,000 feet high, while the plateau of Thibet, between the 
 Kueri-Lun range and the Himalayas, is 11,500 to 13,000 feet 
 above the sea. Persia and Armenia constitute another pla- 
 teau. These examples are sufficient to explain the use of 
 the term. 
 
 2. System in the Earth's Features. 
 
 L General form of the continents resulting from their reliefs. 
 
 The continents are constructed on a common model, as 
 follows: they have high borders and a low centre, and are, 
 therefore, basin-shaped. Thus, North America has the Appa- 
 lachians on the eastern border, the Eocky chain on the west, 
 and between these the low Mississippi basin. Fig. 4 illus- 
 
 Fig. 4. 
 
 trates this form of the continent. In the section, b repre- 
 sents the Eocky Mountain chain on the west, with its 
 lines of ridges at summit ; a, the Washington chain (includ- 
 ing the Sierra Nevada and Cascade range), near the Pacific 
 coast ; c, the Mississippi basin ; d, the Appalachian chain on 
 the east. 
 
 South America, in a similar manner, has the Andes on the 
 west, the Brazilian Mountains on the east, and other heights 
 along the north, with the low region of the Amazon and La 
 Plata making up the larger part of the great interior. Fig. 5 
 is a transverse section from west to east (W, E), showing the 
 
THE EARTH'S FEATURES. 15 
 
 Andes at a, and the Brazilian Mountains at b. In these 
 sections the height as compared with the breadth is neces- 
 sarily much exaggerated. 
 
 In the Orient there are mountains on the Pacific side, 
 others on the Atlantic ; and, again, the Himalayas, on the 
 
 Fig. 5. 
 
 A A 
 
 south, face the Indian Ocean, and the Altai face the Arctic or 
 Northern Seas. Between the Himalayas (or rather the Kuen- 
 Lun Mountains, which are just north) and the Altai, lies the 
 plateau of Gobi, which is low compared with the enclosing 
 mountains ; and farther west there are the low lands of the 
 Caspian and Aral, the Caspian lying even below the level of 
 the ocean. The Urals divide the 6,000 miles of breadth into 
 two parts, and so give Europe some title to its designation 
 as a separate continent. West of their meridian there are 
 again extensive low lands over Middle and Southern Euro- 
 pean Eussia. 
 
 In Africa there are mountains on the eastern border, and 
 on the western border south of the coast of Guinea ; there 
 are also the Atlas Mountains along the Mediterranean, and 
 the Kong Mountains along the Guinea ooast ; and the inte- 
 rior is relatively low, although mostly 1,000 to 2,000 feet in 
 elevation. 
 
 In Australia, also, there are high lands on the eastern and 
 western borders, and the interior is low. 
 
 All the continents are, therefore, constructed on the basin- 
 like model. 
 
 2, Relation between the heights of the borders and the extent 
 of the adjoining ocean. There is a second great truth with 
 regard to the continental reliefs; namely, that the highest 
 border faces the largest ocean. 
 
16 PHYSIOGRAPHIC GEOLOGY. 
 
 Each of the continents sustains the truth announced. 
 North America has its great mountains, the Rocky chain, on 
 the side of the great ocean, the Pacific ; and its small moun- 
 tains, the Appalachian, on the side of the small ocean. So, 
 South America has its highest border on the west ; and the 
 Andes as much exceed in elevation and abruptness the Rocky 
 chain as the South Pacific exceeds in capacity the North 
 Pacific. The Orient has high ranges of mountains on the 
 east, or the Pacific side, and lower, as those of Norway and 
 other parts of Europe, on the west ; and the Himalayas, the 
 highest of the globe, face the great Indian Ocean (besides 
 being most elevated eastward toward the great Pacific), while 
 the smaller Altai face the small Northern Ocean. In Africa 
 the eastern mountains, or those on the side of the Indian 
 Ocean, are higher than those on that of the Atlantic. In 
 Australia the highest border is on the Pacific side ; for the 
 South Pacific, taking into view its range in front of East 
 Australia, is greater than the Indian Ocean fronting West 
 Australia. 
 
 Hence the basin-like shape before illustrated is that of a 
 basin with one border much higher than the other ; and with 
 the highest border on the side adjoining the largest ocean. 
 
 3, System in the earth's feature-lines. The great masses of 
 land and the larger peninsulas have in general a triangular 
 outline, pointed southward. North and South America are 
 prominent examples under the principle ; Africa is another, 
 and India and the peninsula of Greenland are others. This 
 form is connected with the general fact that the directions 
 of coast lines, mountain-ranges, and the ranges of islands in 
 the ocean conform approximately to two systems r f trends, 
 one northeastward and the other northwestward. 
 
 North America derives its triangular outline (see map, 
 p. 11) from the northeastward trend of the eastern coast and 
 the northwestward of the western ; and these trends are 
 repeated in the mountain-ranges of the continent, the oldest 
 and those of most recent origin. In South America the north 
 
THE EARTH'S FEATURES. 17 
 
 coast has the northwestern direction, and the east coast, the 
 northeastern, and at the east cape the lines consequently 
 make nearly a right angle. The northeastward trend char- 
 acterizes the west coast of Europe and northern Africa, 
 Scandinavia, and the mountains of Norway. Consequently 
 the trough of the Atlantic and its zig-zag bottom "ridge" 
 trend like the American coast. On the contrary, the trend 
 of the Pacific ocean is parallel nearly with the west coast of 
 North America, and is northwestward, like that of its central 
 underwater plateau ; and the course is at right angles to that 
 of the north Atlantic. The 
 islands of the Pacific are, 
 as stated on page 10, 
 grouped in long lines, or 
 ranges, and nearly all these 
 lines have a general paral- 
 lelism to the longer axis 
 of the ocean. One ex- 
 ample, that of the Hawa- 
 ian or Sandwich Islands, 
 is shown in Fig. 6. But 
 
 _ _ _ , . H, Hawaii ; M, Maui ; 0, Oalm ; K, Kauai. 
 
 New Zealand has the trans- 
 verse or northeastward trend, and this is continued in 
 islands both to the north and south. 
 
 The two courses here pointed out vary toward north and 
 south on one side, and east and west on the other, as shown 
 in the ranges of islands northeast and north of Australia. 
 
 O 
 
 There are exceptions to the principle stated ; but these 
 would necessarily have come from the many diverse condi- 
 tions on which the making of the earth's ranges of moun- 
 tains and the outlining of its lands have depended. 
 
 The features described have a vast influence in adapting 
 the continents for man. 
 
 America stands with its highest border in the far west, and 
 with all its great plains and great rivers inclined toward the 
 
 2 
 
18 PHYSIOGRAPHIC GEOLOGY. 
 
 Atlantic ; for, through the Gulf of Mexico, the whole interior, 
 as well as the eastern border, has its natural outlet eastward. 
 Had the high mountains of the continent been placed on its 
 eastern side, they would have condensed the moisture of the 
 winds before they had traversed the land, and sent it back, in 
 hurrying and almost useless torrents, to the ocean ; but, being 
 on the western, all the slopes, from the Atlantic to the tops 
 of the Eocky Mountains, lie open to the moist winds, and 
 fields and rivers show the good they thus receive. 
 
 Again, the Orient, instead of rising into Himalayas on the 
 Atlantic border, has its great heights in the remote east, and 
 its vast plains, even those of Central Asia, have their natural 
 outlet westvjard, or toward the same Atlantic Ocean. Thus, 
 as Professor Guyot has said, the vast regions of the world 
 which are best fitted by climate and productions for man are 
 combined into one great arena for the progress of civiliza- 
 tion. Both the Orient and the Occident pour their streams 
 and bear a large part of their commerce into a common 
 ocean ; and this ocean, the Atlantic, is but a narrow ferriage 
 between them, and vastly better for the union of nations 
 than connection by as much dry land : 3,000 miles of dry 
 land would be, even in the present age, a serious obstacle 
 to intercourse; while 3,000 miles of ocean draw^ the east! 
 and west only into closer political, commercial, and social 
 relations. 
 
 I ; 
 
PART II. 
 
 STRUCTURAL, GEOLOGY. 
 
 THE term rock, in geology, is applied to all natural forma- 
 tions of rock-material, whether solid, like sandstones and 
 slates, or loose sand and gravel. All sandstones were once 
 beds of loose sand ; and there is every shade of gradation, 
 from the hardest sandstone to the softest sand-bed ; so that 
 it is impossible to draw a line between the consolidated and 
 unconsolidated. Geology does not attempt to draw the line, 
 regarding consolidation as an accident in the history of the 
 earth's beds or deposits : an accident that probably happened 
 to not a thousandth part of the sand-beds and mud-beds that 
 have existed ; and yet, to enough of them in each period for 
 the preservation of the wonderfully varied records that are 
 the materials of geological science. 
 
 Eocks may be studied simply as rocks, that is, with 
 reference to their composition, and collections may be 
 made containing specimens of their various kinds. Again, 
 they may be studied as rock-masses spread out over the 
 earth and forming the earth's crust ; and, with this in view, 
 the condition, structure, and arrangement of the great rock- 
 masses, sometimes called terrancs, would come up for 
 consideration. The two subjects under Structural Geology 
 are, therefore : 1. Petrology, or the Constitution of Eocks ; 
 2. The Condition, Structure, and Arrangement of Rock-masses 
 or Terranes. 
 
20 
 
 STRUCTURAL GEOLOGY. 
 
 I. PETROLOGY. 
 1. General Observations. 
 
 Rocks consist essentially of minerals, and the minerals of 
 the common rocks are of four groups : 
 
 1. QUARTZ, called in chemistry, silica and silicon dioxide. 
 
 2. SILICATES, or compounds of silicon in the dioxide state 
 with other substances. 
 
 3. CARBON, the chief element of charcoal and mineral coal, 
 and a constituent of carbonic acid or carbon dioxide. 
 
 4. CARBONATES, or compounds of carbon in the dioxide 
 state with other substances. 
 
 1. QUARTZ, OR SILICA. Quartz far exceeds all other 
 species in abundance. It consists of one atom of silicon 
 and two of oxygen, its formula being Si O 2 . It is one of the 
 hardest of common minerals ; does not melt before the blow- 
 pipe, and does not dissolve in water, or in the ordinary acids. 
 Its hardness and durability especially fit it for this place of 
 first importance in the material of the earth's foundations. 
 
 It is often seen in crystals like Figs. 7, 8, though generally 
 occurring in massive forms, or in grains or pebbles. It is 
 distinguished ordinarily by its glassy 
 aspect, whitish or grayish color, and an 
 absence of all tendency to break with 
 a bright even surface of fracture (a 
 quality of crystals called cleavage). 
 Although usually nearly colorless or 
 white, it is often reddish, yellowish, 
 brownish (especially smoky brown), 
 
 and even black; and the lustre is sometimes very dull, as 
 in chalcedony, flint, and jasper. The sands and pebbles of 
 the sea-shores and gravel-beds are mostly quartz, because 
 quartz resists the wearing action of waters better than any 
 
 Fig. 7. Fig. 8. 
 
CONSTITUTION OF EOCKS. 21 
 
 other common mineral. For the same reason, most sand- 
 stones and conglomerates consist mainly of quartz, 
 i- The hardness (on account of which it scratches glass 
 easily), infusibility, insolubility, non-action of acids, and 
 absence of cleavage are the characters that serve to distin- 
 guish quartz from the other ingredients of rocks. 
 
 But while quartz is so refractory, it easily fuses when 
 mixed and heated with potash, soda, lime, or an oxide of 
 iron, into glass. Ordinary glass is made by mixing powdered 
 quartz with soda or potash and sometimes lime, and subject- 
 ing the mixture to a high heat. Sodium carbonate is hence 
 conveniently used in blow-pipe experiments for distinguish- 
 ing quartz. 
 
 Although quartz is one of the original minerals of the 
 earth's crust, and has been mostly derived from the earlier 
 rocks of the globe, part of it has passed through living beings, 
 either plants or animals and is of organic origin ; for some of 
 the lowest species of these kingdoms of life have the power 
 of making, by secretion, siliceous shells or siliceous particles 
 or spicules in their texture ; and beds of limited extent have 
 been made of these microscopic siliceous shells and spicules. 
 (See page 67). 
 
 2. SILICATES. Many of the common rock-making minerals 
 are silicates, or combinations of silicon with certain basic 
 elements and oxygen; that is with the constituents of the 
 bases alumina, magnesia, lime, potash, soda, oxides of iron, and 
 a few others. 
 
 Pure alumina is the most important of the above-men- 
 tioned bases. It consists of aluminum and oxygen (A1 2 3 ). 
 It is very hard, infusible, and insoluble, and therefore adapted 
 to its place as second in abundance to silica. When crys- 
 tallized, it is the hardest of all known substances, except- 
 ing the diamond, it being the gem sapphire, and the essen- 
 tial ingredient of emery. The species is called corundum in 
 mineralogy. 
 
 Magnesia (magnesium and oxygen, Mg 0), well known 
 
22 STRUCTURAL GEOLOGY. 
 
 under the form of calcined magnesia, is as hard as quartz 
 when crystallized, and equally infusible and insoluble. 
 
 Lime (calcium and oxygen, Ca 0) is common quick-lime, the 
 calx of the Eomans, whence the term calcium for the metal. 
 
 Potash (potassium and oxygen, K 2 0) and soda (sodium and 
 oxygen, Na 2 0) are the alkalies ordinarily so called. 
 
 Iron protoxide (Fe 0) and Iron sesquioxide (Fe 2 3 ) are the 
 two oxides of iron whose constituents exist, like those of the 
 above bases, in many silicates. 
 
 The silicates which contain only the constituents of alu- 
 mina are infusible, as well as very hard. But those which 
 contain the elements of either of the other bases mentioned 
 are with few exceptions fusible, and therefore fit to be the 
 ingredients of igneous or volcanic rocks. 
 
 The following are the most common of these silicates : 
 
 1. Feldspar. The feldspars are silicates, containing the 
 constituents of alumina, a sesquioxide, along with those of 
 the protoxide bases, potash, soda, or lime. They are hard 
 enough to scratch glass, but less hard than quartz. They 
 break easily, or have cleavage, in two directions, with flat lus- 
 trous surfaces ; and the two cleavage-surfaces meet nearly or 
 quite at a right angle. The color is usually white or flesh-red, 
 and rarely dark brown or greenish. The specific gravity is 
 2.42.7. 
 
 The most common kind is a potash feldspar, and is called 
 orthoclase; another, named albite, is a sw&x-feldspar ; two 
 others, oligoclase and labradorite are soda-lime feldspars. 
 
 2. Mica. Mica is a silicate containing the constituents of 
 alumina, along with those of potash and lime, like the feld- 
 spars, but also those of magnesia and oxide of iron. Mica 
 cleaves easily into tough leaves, thinner than the thinnest 
 paper, which are somewhat elastic. It fuses with great diffi- 
 culty. Its most common colors are whitish, brownish, and 
 black. On account of its easy cleavage, transparency, and 
 difficult fusibility, it is often used in the doors of stoves. 
 The most common kind of mica has a light color and is 
 
CONSTITUTION OF KOCKS. 23 
 
 called muscovite; another, usually black in color (because of 
 the amount of iron present), is called biotite. Some micas 
 contain water, that is, are hydrous ; and these hydro-micas, as 
 they are called, are pearly in lustre, feel a little soapy, and 
 are sometimes mistaken for talc. 
 
 The minerals, quartz, feldspar, and mica are the constituents 
 of granite ; and they may be distinguished in it as follows : 
 the grains of quartz, by their more glassy lustre, grayer 
 color, and want of cleavage ; the grains of feldspar, by their 
 cleavage ; the grains of mica, by their very easy cleavage by 
 means of the point of a knife-blade into thin elastic leaves. 
 
 3. Chlorite. Resembles black mica in constitution, and, 
 when well crystallized, in its cleavage ; but it contains 14 per 
 cent of water and no potash. Moreover its leaves are not 
 elastic, its color is usually dark green, and it feels a little 
 greasy. It is often fine granular. 
 
 4. Hornblende and Pyroxene. Hornblende and pyroxene 
 are silicates of magnesium, calcium and iron, aluminum not 
 being an essential constituent. The usual kind of each in 
 rocks is black, or greenish black, and 2.8 to 3.2 in specific 
 gravity ; but white and light green varieties are common. 
 They equal feldspar in hardness ; unlike mica, they are 
 brittle. The crystals or crystalline grains have two equal 
 shining cleavages ; in hornblende the angle between the two 
 is about 124, in pyroxene, 87. Hornblende is often in 
 long slender crystallizations, and asbestus is a variety of it. 
 Both make hard and tough rocks. Pyroxene is a constituent 
 of trap, and of a large part of igneous rocks. 
 
 5. Talc ; Serpentine. Talc and .serpentine are hydrous 
 silicates of magnesium. They both \iave a greasy feel, 
 especially talc. Talc is very soft, so soft that it does not 
 feel gritty to the teeth. It is often in foliated plates or 
 masses like mica ; but the folia, or leaves, though separating 
 rather easily, and flexible, are not elastic. The usual color 
 is pale green. Soapstow or steatite is a massive variety of 
 talc, of whitish, grayish, or greenish color. 
 
24 
 
 STRUCTURAL GEOLOGY. 
 
 Serpentine. Contains much water (14 per cent). It is 
 usually a dark-green massive mineral or rock, of a very 
 fine-grained texture, and soft enough to be cut with a 
 knife. 
 
 6, The following minerals occur distributed in crystals 
 through many crystalline rocks: 
 
 Garnet; Tourmaline. These species, like the micas, are 
 aluminum silicates of magnesium, calcium and iron. Garnet 
 is often in dark red, brownish, or black crystals of 12 or 24 
 
 Fig. 9. 
 
 Fig. 10. 
 
 Fig. 11. 
 
 sides (dodecahedrons or trapezohedrons). The first of these 
 forms is represented in Fig. 9, showing garnets distributed 
 through a mica schist. Tourmaline (Fig. 10) is generally in 
 
 oblong 3, 6, 9, or 12-sided crys- 
 tals, shining and black; also at 
 times blue-black, brown, green, 
 and red. 
 
 Andalusite is simply an alu- 
 minum silicate and hence is in- 
 fusible. It is found in imbedded 
 crystals in clay slate, and some- 
 times in mica schist ; the form is 
 nearly a square prism. The in- 
 terior of the crystals is very frequently black or grayish-black 
 at the centre and angles (Fig. 11), while the rest is nearly 
 white ; and this variety is called made, or chiastolite. 
 
 Cyanite, Has the same composition as the preceding, 
 
CONSTITUTION OF ROCKS. 25 
 
 and like it is infusible. Usually occurs in mica schist or 
 gneiss in thin, blade-like, pale blue crystals. 
 
 Staurolite. Belated to the last two minerals, and infusible, 
 but it contains some iron. Its crystals are stout prisms of 
 128, of black or brown color ; they often have the form of 
 a cross, whence the name, from crtaupo? a cross. 
 
 3. CARBON. Carbon occurs pure among minerals only in 
 diamond and yraphitc. It is the chief element in mineral 
 coal, but is combined in it with more or less of hydrogen and 
 oxygen, and also some nitrogen. Charcoal, the carbo of the 
 Romans, is nearly all carbon. 
 
 1. Diamond ; Graphite. Diamond and graphite are both 
 pure carbon, but in different molecular states ; the former, 
 the hardest of minerals, crystallizing in octahedral and 
 related forms ; the latter, one of the softest, crystallizing 
 in hexagonal plates, with nearly the easy cleavage of mica 
 and the lustre of steel. Graphite is also called plumbago 
 and black-lead, and is the material of the mis-named lead- 
 pencils. It occurs in crystalline rocks in scales and masses, 
 and is ground up and subjected to pressure to prepare it for 
 making pencils. 
 
 2. Mineral Coal ; Mineral Oil. Mineral coal is not a true 
 mineral. It constitutes beds in various rock-formations, 
 and has been formed from wood or some kind of vege- 
 table material. There are three prominent kinds, differing 
 in the amount of oxygen and hydrogen that is present with 
 the chief ingredient carbon, and consequently in the amount 
 of inflammable gas given out on burning. This gas gener- 
 ally consists simply of carbon and hydrogen, and is largely 
 the carbo-hydrogen used in illumination. 
 
 1. Anthracite contains over 85 per cent of carbon. It 
 yields little that is volatile, and burns with a feeble blue 
 flame. 
 
 2. Bituminous Coal has less hardness and lustre than an- 
 thracite, contains usually 70 to 80 per cent of carbon, and 
 gives out on heating 20 to 40 per cent of volatile matter. It 
 
26 STRUCTURAL GEOLOGY. 
 
 hence burns with a bright yellow flame. It is the source 
 of illuminating gas, and will yield also mineral oil. Cannel 
 coal is a compact bituminous coal having a feeble lustre; 
 it often yields 40 to 50 per cent of volatile matter, and is an 
 available source of mineral oil. Bituminous coal is called 
 caking coal when it softens in the fire and cakes at surface, 
 so that a fire made of it requires poking to make it burn 
 freely ; non-caking kinds have not this quality, and hence are 
 preferable for fuel and economical purposes. 
 
 3. Brown Coal differs from bituminous coal in its brownish- 
 black powder, and in containing 2 or. 3 times as much oxygen 
 (15 to 25 or more per cent). The mineral coal from rocks 
 more recent than the true Carboniferous formation is often 
 improperly called brown coal, even when good bituminous 
 coal, without a brownish color to the powder. The name 
 lignite is sometimes also applied to it ; but true lignite is 
 coal that retains the fibrous texture of the original wood. 
 
 4. Mineral Oil is liquid carbo-hydrogen, and is chemically 
 related to illuminating gas. It was formed out of animal or 
 vegetable materials. Illuminating gas is often produced in 
 great quantities from the wells or sources yielding mineral 
 oil, and in some villages in oil regions the houses are heated 
 and lighted by it. Many black shales yield mineral oil 
 when heated. They do not contain the oil, but instead a 
 peculiar carbo-hydrogen compound (not yet satisfactorily 
 investigated) which yields the oil on heating. Mineral oil 
 on long exposure to the air combines with oxygen and finally 
 becomes a black fusible bitumen, or a coal-like substance 
 having little or no fusibility. 
 
 3. Carbonic Acid, or Carbon dioxide (C 2 ), is a gas contain- 
 ing 27.65 per cent of carbon and the rest oxygen. It con- 
 stitutes 3 out of 10,000 parts by volume of the atmosphere, 
 and is carried from the atmosphere to the earth by the rains. 
 It is formed in the combustion of wood, combustion consist- 
 ing chiefly in the combining of oxygen with the constituents 
 of the wood. It is also given out in the respiration of 
 
CONSTITUTION OF ROCKS. 
 
 27 
 
 animals, the' processes of life in animals being carried forward 
 through a sort of combustion, or a similar combination of 
 oxygen with the materials of the tissues. 
 
 4. CARBONATES. Compounds containing the elements of 
 carbonic acid or carbon dioxide with those of lime, magnesia, 
 etc. 
 
 1 Calcite, or Calcium carbonate (Ca C 3 ). The material 
 of limestone and marble. It crystallizes in many forms, a 
 few of which are represented in Figs. 12, 13. Its colors are 
 very various. It cleaves easily in three directions with 
 bright surfaces, as may be seen on examining even the grains 
 of a fine white marble. It is so soft as to be easily scratched 
 with a knife ; dissolves in diluted acid (hydro-chloric) with 
 effervescence, that is, with an escape of carbonic acid gas ; 
 and when heated (as in a lime-kiln or before the blow-pipe") 
 it burns to quick-lime without melting. By its effervescence 
 with acids it differs from all the minerals before mentioned. 
 
 2. Dolomite, calcium-magnesium carbonate (|-Ca .] Mg C 3 ); 
 that is, it differs from calcite in containing magnesium in 
 place of half of the calcium. Very much of the so-called 
 limestone of the world is magnesian limestone. It closely re- 
 sembles common limestone, but may often be distinguished 
 by its effervescing scarcely at all with acid unless heat be 
 applied. The trial may be made by dropping a particle, las 
 
28 STRUCTURAL GEOLOGY. 
 
 large as half a grain of wheat, into a test-glass* containing 
 a mixture, half and half, of hydro-chloric acid and water. 
 For iron-carbonate (siderite) see next page. 
 
 5. CHLORIDES. The only chloride forming rock-masses is 
 Common or Rock Salt It is sodium chloride (Na Cl). It is 
 
 easily distinguished by its taste. It constitutes beds, more 
 or less impure, in strata of various ages from the Silurian to 
 recent time ; which is accounted for by the fact that the 
 universal ocean is its source, and simple evaporation the 
 means of depositing it. Silurian rock salt occurs in "Western 
 New York and Canada ; and a great recent (early Quater- 
 nary) deposit, nearly 40 feet thick and remarkably pure, 
 occurs at Petit Anse, La., near the Gulf of Mexico. The 
 saline constituents of the ocean's waters constitute about 
 3.53 parts in 100 ; of which three-fourths or 2.65 are common 
 salt, the rest being, magnesium chloride 0.32, magnesium 
 sulphate 0.19, potassium chloride 0.12, calcium sulphate, or 
 gypsum, 0.16, sodium bromide 0. 06r=3.53, with traces also 
 of other ingredients. 
 
 6. IRON ORES. Iron ores are widely distributed in rocks, 
 and some of them form thick beds. Unlike the minerals 
 mentioned above they have a specific gravity above 3.5. 
 The most important are three oxides, two sulphides, and a 
 carbonate. 
 
 1. Hematite, or iron sesquioxide (Fe 2 3 ). It yields a red 
 powder, whence its name given it by the old Greeks, from 
 al/jia Hood. Its crystals have usually an iron-black color, 
 and high lustre ; but it is deep red when earthy or impure. 
 It is the source of the color in red sandstones and other 
 red rocks. 
 
 2. Limonite, or hydrous iron-sesquioxide, equivalent to 2 of 
 Fe 2 3 to 3 parts of water. It has a brownish-yellow powder. 
 It varies in color from black to brown and yellow. While red 
 ochre of painters is. impure hematite^ yellow ochre is impure 
 limonite. Limonite is the coloring/mgredient in a large part 
 of the brown and brownish yellow rocks and clays. The 
 
KINDS OF ROCKS. 29 
 
 water present goes off on heating and hence the mineral, and 
 all rocks colored by it, when heated turn red. It is formed 
 from the oxidation of various iron-bearing minerals (page 82), 
 and often makes deposits in marshes, whence its name from 
 the Greek for marsh. 
 
 3. Magnetite. Magnetite has an iron-black color, like 
 hematite ; but it is attracted by a magnet, and has, besides, 
 a black powder. It consists of 3 of iron to 4 of oxygen 
 (Fe 3 4 ). It is common in grains in a large part of rocks, the 
 calcareous (or limestones) excluded, and among the sands of 
 seashores and soils ; and like hematite, constitutes great beds 
 in some of the older rocks. 
 
 Iron protoxide never occurs as a mineral. 
 
 4. Pyrite. An iron-sulphide, (Fe S 2 ) of a brass-yellow color 
 and as hard nearly as quartz. It will strike fire with a steel, 
 and was named by the Greeks from irvp, fire. It is common in 
 rocks, in massive forms, crystals (often cubes), and in grains. 
 Pyrrlwtite is the name of another common iron-sulphide con- 
 taining proportionally less sulphur (Fe 7 S 8 ), having the grayish 
 yellow color of bronze, and so soft as to be easily scratched 
 with the point of a knife. 
 
 5. Siderite, or iron carbonate (Fe C 3 ), called also spathic 
 iron. It has approximately the cleavage and form of calcite 
 when crystallized, but is usually grayish in color. It changes 
 readily on exposure to brown (and to limonite), and is much 
 heavier than calcite, its specific gravity being 3.7 to 3.9. It 
 effervesces in heated dilute hydro-chloric acid, like dolomite. 
 
 The " iron-stone " or " clay iron-stone " of coal regions and 
 others, used as an ore of iron, is very often siderite ; but it is 
 often also hematite, and sometimes limonite. 
 
 2. Kinds of Rocks. 
 
 1. Fragmental and Crystalline Rocks. The minerals of 
 which a rock consists may be either (1) in broken or worn 
 grains or pebbles, like those of sand or mud or a bed of gravel ; 
 or, on the contrary, (2) they may be in crystalline grains, in 
 
30 STRUCTURAL GEOLOGY. 
 
 which case they were formed where they now are at the time 
 of the crystallization of the rock. Such crystalline grains are 
 angular, as may be seen on a surface of fracture, and, in- the 
 case of most minerals excepting quartz, show surfaces of 
 cleavage. Common white marble and granite are good 
 examples of rocks having a crystalline texture ; and also 
 loaf-sugar and steel, among products of art. 
 
 The rocks of the first kind, consisting of fragments of 
 other rocks, are called fragmental rocks ; and those of the 
 latter kind, crystalline rocks. 
 
 2, Fragmental rocks. These are the most common of 
 rocks. They constitute the chief part of the twenty miles 
 of beds, in depth (page 1), open to geological study. The 
 wear and decomposition of the oldest rocks produced the 
 fragmental material for those of the next age, and so on 
 through geological time; and the rocks made of such ma- 
 terial, as, for example, sandstones, shales, and conglomerates, 
 are the fragmental rocks. They are stratified rocks also, be- 
 cause they are in beds. They are also called sedimentary 
 rocks, because the material was in most cases deposited as a 
 sediment from waters. Most limestones also are fragmental 
 rocks, as explained on page 31. 
 
 Intermediate between rocks that are obviously fragmental 
 and crystalline there are others, of a flinty compactness, which 
 show no distinct grains, and are therefore not easily referred 
 to either division. To determine the division to which 
 such rocks belong, the beds affording them and others associ- 
 ated have to be studied. If these associated rocks are frag- 
 mented, then the compact beds are probably so also ; but if 
 these are crystalline, then they are probably related to the 
 crystalline. Experience among rocks is required to decide 
 correctly in all such cases. The examination of thin trans- 
 parent slices with the microscope is sometimes the only 
 means of distinguishing the two kinds. 
 ' The crystalline rocks are either mttamorphic or igneous. 
 
 3. Metamorphic rocks are those which have been changed 
 
KINDS OF ROCKS. 31 
 
 (metamorphosed) into crystalline rocks, and usually without 
 fusion. The rocks so changed are the ordinary fragmental 
 rocks and limestones. The alteration, when most perfect, 
 has consisted in a complete crystallization of the rock, and, 
 when least so, in its consolidation ; between which extremes 
 all gradations exist. Examples of metamorphic rocks are 
 architectural marble, mica schist, gneiss^aad much gran|te. 
 
 4. Igneous rocks are those which have come up melted 
 through volcanic vents, or through fissures opened to some 
 seat of melted rock within or below the earth's crust. They 
 include lavas, part of porphyry and granite, and other rocks 
 described beyond (page 37). 
 
 It appears from the definitions above given that the frag- 
 mental rocks have come from the working over and redistri- 
 bution of surface rock-material ; and the metamorphic, from 
 the crystallizing in certain regions, through some means, of 
 fragmental rocks. Of the three kinds, igneous rocks alone 
 have added to the amount of surface material. Besides 
 these, many veins contain mineral material from the earth's 
 depths. 
 
 5. Calcareous rocks. Calcareous rocks, so named from the 
 Latin calx lime, are the limestones. To a great extent they are 
 of organic origin, that is, have been formed from pulverized 
 animal relics, such as shells and corals ; and in this case they 
 are properly fragmental or sedimentary beds, although so 
 finely compact that this might not be suspected from their 
 texture. 
 
 Some limestones have been made from the accumulation 
 and consolidation of minute shells, called Rhizopods. These 
 shells being generally no larger than grains of sand, powder- 
 ing was not necessary. The limestone rocks formed of them . 
 hence may not be fragmental. Still, even these minute shells 
 are generally broken. Chalk is an example. 
 
 Limestones of mineral origin, that is, those made from 
 earlier limestones, occur, but are not very common. Lime- 
 stone conglomerates are of this kind. 
 
32 STRUCTURAL GEOLOGY. 
 
 Other calcareous rocks have been deposited from viaters 
 holding the material in solution, and are, therefore, of chemical 
 origin. Of this kind is the travertine of Tivoli near Kome in 
 Italy, and of Gardiner's Eiver in the geyser region of the 
 Yellowstone Park, and similar beds in many regions of 
 mineral springs, besides the petrified moss and trees of some 
 marshy places. 
 
 6. Siliceous rocks. Siliceous rocks are those that consist 
 largely of quartz, or silica. The name is from the Latin silex, 
 signifying flint, a variety of quartz. Siliceous material, or 
 quartz, like the calcareous, is, as stated on page 21, of both 
 mineral and organic origin ; but the mineral is vastly the 
 most abundant. It is also to a small extent a chemical pro- 
 duct, as in the siliceous depositions about geysers (page 142). 
 The silica of organic and chemical origin is usually in the 
 state of opal-silica. Opal-silica has less hardness and specific 
 gravity than quartz ; but by solution and consolidation, gener- 
 ally becomes true quartz, as in flint. 
 
 7. Hydrous rocks. A hydrous mineral is one containing 
 water ; and a hydrous rock contains a hydrous mineral among 
 its constituents (page 23). 
 
 8. Porphyritic rocks. A porphyritic rock is one having dis- 
 tinct crystals of feldspar disseminated through it, so that, 
 when polished, the surface appears spotted with a light- 
 colored mineral, usually between an eighth of an inch and 
 two inches in length. The red porphyry of Egypt and 
 the green porphyry of the eastern borders of Greece, much 
 used for ornamental purposes by the ancients, are typical 
 examples. Granite, gneiss, syenite, diorite, and other rocks 
 are said to be porphyritic when similarly spotted. 
 
 9. Massive, schistose, laminated, slaty, shaly rocks, Kocks 
 are termed massive when there is no tendency to break into 
 slabs or plates, as in the case of granite and most conglom- 
 erates ; schistose, if crystalline, when breaking into slabs 
 or plates, owing to the arrangement in layers of the mineral 
 ingredients, especially the mica or the hornblende ; lami- 
 
KINDS OF ROCKS. 33 
 
 netted, when splitting into slabs or flagging-stones, but not in 
 consequence of a crystalline structure ; slaty, when dividing 
 easily into thin, even, hard slates, like roofing slate ; sJialy, 
 when dividing easily into thin plates like slate, but the 
 plates irregular and often fragile. 
 
 The term schist is applied to a schistose rock ; flag, to a 
 laminated rock ; slate, to a slaty rock ; shale, to a shaly rock. 
 
 The kinds of rocks are here described under the four heads : 
 1. Fragmental Rocks, not calcareous; 2. Metamorphic Rocks, 
 not calcareous ; 3. Calcareous Rocks ; 4. Igneous Rocks. 
 
 I. Fragmental Rocks, not Calcareous. 
 
 The fragmental material which the wear and decomposi 
 tion of rocks ordinarily produces is either: (1) sand ; (2 
 gravel ; (3) mud, or earth: or (4) clay ; or mixtures of these 
 materials. Hence these are the constituents of the fragmental 
 rocks, and they determine their kinds. 
 
 1. Sand-beds; Gravel-beds. Most sand or gravel consists 
 chiefly of quartz ; but some beds are made of granite sand 
 or pebbles, or of fragments of other rocks. Some contain 
 much clay, or are argillaceous (so named from argilla, clay^ ; 
 some are red or brownish yellow, owing to the presence of 
 iron-oxide, and are hence ferruginous. Some will effervesce 
 slightly with acid, and are hence calcareous (page 31). Beach 
 sands often contain red grains of garnet ; and commonly black 
 grains of magnetite, which a magnet easily attracts. 
 
 2. Mud ; Earth ; Clay. Mud and earth contain, besides 
 grains of quartz, some pulverized feldspar, or else clay, with 
 more or less of other minerals. The terms argillaceous*, fer- 
 ruginous, calcareous, are here applied as above ; the calcareous 
 grains are usually derived from the grinding up of shells. 
 When Hack the color is due to carbonaceous material derived 
 from vegetable or animal decomposition. 
 
 Common clay is a mixture of pure clay with grains of 
 quartz, feldspar, and usually traces of hydrous iron-oxide, 
 
 3 . 
 
34 STRUCTURAL GEOLOGY. 
 
 (limonite), or else iron-carbonate. Owing to the iron, it burns 
 red, making red brick heat changing the iron-mineral present 
 to hematite (page 28). Occasionally, as in certain Milwau- 
 kee clays, the iron is in an iron-silicate, so that the heat 
 cannot oxidize it ; and consequently the brick it makes are 
 not red. Clays free from iron are required for white pottery ; 
 and free also from grains of feldspar for making ^re-brick, 
 because the potash of feldspar makes clay fusible. 
 
 Pure clay, or Imolin, is white, and feels greasy. It is an 
 aluminum silicate containing 14 per cent of water. It results 
 from the decomposition of feldspar (page 84). It is used in 
 making fine pottery and porcelain, and paper. 
 
 3. Sandstone. A rock made of sand, of red, gray, brown, 
 white and other colors. When of quartz sand it is a quart- 
 zose or siliceous sandstone ; if of granite sand, a granitic ; if 
 fine earthy or clayey, an argillaceous sandstone. It makes 
 a durable building stone when firm, if not much absorbent 
 of water when immersed in it, and if free from pyrite so as 
 not to rust on exposure. The brownish red is often called 
 freestone. The sandstone used for grindstones is even-grained 
 and more or less friable. 
 
 4. Conglomerate. Consolidated gravel. If the stones are 
 rounded the rock is often called a pudding-stone; and if 
 angular fragments, a breccia ; if the pebbles are of quartz, a 
 siliceous conglomerate ; if of limestone, a calcareous conglome- 
 rate. The stones may be a foot or more in diameter, though 
 usually much smaller. 
 
 5. Shale, A somewhat slaty rock made of clay or clayey 
 earth or fine mud. The colors are of all dull shades from 
 gray to red and black. Carbonaceous shale is the blackish 
 kind, yielding mineral oil when heated. 
 
 6. Tufa. A volcanic sandstone, composed of volcanic sand 
 or pulverized volcanic rocks : the color is usually brownish, 
 brownish-yellow, grayish, or reddish. 
 
f OF TM6 \ 
 
 VUlVKKSfTY t 
 KINDS OF ROCKS. 35 
 
 2. Metamorphic Rocks. 
 
 1. Granite, A crystalline rock, consisting of quartz, feld- 
 spar, and mica. Color, usually light or dark gray, or flesh- 
 red, the latter shade derived from a flesh-colored feldspar : 
 the quartz, uncleavable and usually grayish-white in color ; 
 the feldspar, white to flesh-red, and yielding smooth, shining 
 surfaces by cleavage; the mica, white to black, and afford ing- 
 thin, flexible leaves by cleavage. 
 
 2. Gneiss. Like granite in constitution, but having a bed- 
 ded structure, owing to the arrangement of the minerals, 
 the mica especially being in parallel planes ; it has, therefore, 
 a banded appearance on a surface of transverse fracture. If 
 the color of the gneiss is dark gray, it is banded usually with 
 black lines consisting largely of black mica. Along the 
 micaceous planes it breaks rather easily into slabs, which are 
 sometimes used for flagging. 
 
 3. Mica Schist. Eelated to gneiss, but consisting more 
 largely of mica, with usually more quartz and less feldspar, 
 and, in consequence of the mica, breaking into thin slabs. 
 The slabs have a glistening surface. In regions of mica 
 schist the dust of the roads is often full of shining particles 
 of mica. 
 
 4. Syenyte ; Hornblendic Gneiss ; Hornhlendic Schist. Syenyte 
 resembles granite, but contains hornblende, a black, brittle 
 mineral, in place of mica. A rock like gneiss, but contain- 
 ing hornblende in place of mica, is called syenyte gneiss. A 
 black or greenish-black rock consisting almost wholly of 
 hornblende and schistose is called hornblende schist ; or if not 
 schistose, Jiornblendyte. 
 
 5. Hydromica Schist. A slaty, fine-grained mica schist 
 feeling somewhat greasy to the fingers. It used to be called 
 talcose slate ; but it contains a hydrous mica instead of talc. 
 
 6. Chlorite Schist. A slaty rock containing the olive-green 
 mineral chlorite (page 23), (which gives it a dark green color.) 
 Much hydromica schist is chloritic. 
 
36 STRUCTURAL GEOLOGY. 
 
 7. Slate, Argillyte, Phyllyte. Names of roofing-slate and 
 allied slaty rocks. The texture is hardly crystalline to the 
 naked eye. The slates in the most perfect kinds are hard, 
 smooth in surface, and not absorbent of water. Color, blue- 
 black, purplish, red, greenish, and of other shades. Much 
 slate is a hydromica schist of very fine grain. 
 
 There is a gradual passage of the above rocks from granite 
 into gneiss; from gneiss into mica schist; and from mica 
 schist, hydromica schist, and chlorite schist into argillite. 
 
 8. Quartz Rock; Quartzyte. Names applied to the sand- 
 stone of a rnetamorphic region. Quartzyte is usually very 
 hard. It differs from massive quartz in consisting (as seen 
 under a lens) of grains of quartz. Itacolumite or flexible 
 sandstone, is a laminated porous quartzite containing minute 
 scales of a hydrous mica, and having some flexibility. Occurs 
 in the gold regions of North Carolina and Brazil. 
 
 9. Dioryte. Near syenyte ; but the feldspar is not ortho- 
 clase, as in syenyte, but oligoclase or labradorite. It is a 
 coarse or fine grained rock, grayish white to dark green in 
 color, and sometimes almost black. 
 
 3. Calcareous Rocks. 
 
 a. Non-metamorphic. 
 
 1. Common Limestone. A compact rock of grayish and 
 other dull shades of color to black, consisting either of calcite 
 or dolomite, but often impure from the presence of clayey or 
 earthy material. It breaks with little or no lustre. If con- 
 taining fossils it is called fossiliferous limestone ; if the fossils 
 are corals, coral limestone ; if remains of crinoids, crinoidal 
 limestone. For the distinctive characters, see page 27. When 
 impure, and therefore good for making hydraulic lime (quick- 
 lime that will make a cement which sets under water), it is 
 called hydraulic limestone. Chalk is a variety of limestone 
 soft enough to be used for marking. 
 
KINDS OF ROCKS. 37 
 
 Many varieties of common limestone are polished and used 
 as marbles ; they have black, reddish, yellow, gray, and other 
 colors ; kinds containing fossil shells are called shell-marbles. 
 
 2. Oblyte. A limestone consisting of concretions as small 
 as the roe of fish, or smaller, whence the name, from the 
 Greek MOV, egg. Oolite or oolitic limestone occurs in all the 
 geological formations, and is forming in modern seas about 
 the Florida keys and other coral reef regions. 
 
 3. Travertine. Stalactites are limestone concretions hang- 
 ing from the roofs of caverns ; and stalagmite is the same 
 material covering the floors ; both are formed from the calca- 
 reous waters that come through the roof, and are sometimes 
 called dripstone. A similar deposit from streams or ponds is 
 called travertine ; it is sometimes used for a building stone. 
 Petrified leaves and moss are made by the same kind of 
 waters. 
 
 b. Metamorphic. 
 
 Crystalline Limestone ; Architectural and Statuary Marble. - 
 
 Limestone having a crystalline texture, and, consequently, 
 glistening on a surface of fracture. A pure white kind, of fine 
 grain, is used for statuary, and both this and coarser varieties 
 for marble buildings. Most of the clouded marbles are here 
 included. 
 
 4. Igneous Rocks. 
 
 The following igneous rocks are of two series : I., the Horn- 
 blende-pyroxene series, containing, besides the feldspar, much 
 hornblende or pyroxene ; specific gravity above 2.75; colors 
 usually dark, from black to red and dark gray. IT. The Feld- 
 spathic series, the feldspar greatly predominating, with little 
 or no hornblende or pyroxene; specific gravity under 2.75 ; 
 colors usually light gray to red. 
 
 1. HORNBLENDE-PYROXENE SERIES. 1. Syenyte and Dioryte 
 (pp. 35, 36) occur as igneous rocks as well as metamorphic. 
 The latter is often a very fine-grained compact rock, and when 
 
38 STRUCTURAL GEOLOGY. 
 
 it contains disseminated feldspar crystals makes a variety of 
 porphyry. The red porphyry of Egypt contains in the mass 
 oligoclase and hornblende, and has disseminated crystals of 
 orthoclase. The green porphyry (or oriental verd-antique) has 
 labradorite and pyroxene in its compact mass, and hence is 
 more closely related to the following kind, dolerite. These 
 porphyritic rocks are supposed to be igneous. 
 
 2. Doleryte consists of the feldspar labradorite and pyrox- 
 ene, and has greenish-black, brownish-black, and black colors. 
 It is also often called trap. It may be either crystalline- 
 granular, or of a flinty compactness. It contains also grains 
 of magnetite. Basalt is a compact variety. Diabase is another 
 name for doleryte, used especially for doleryte older than 
 Tertiary. Chloritic doleryte is sometimes called melaphyre. 
 
 3. Peridotyte is a doleryte containing grains of a green sili- 
 cate, of a bottle-glass green color, called chrysolite or olivine. 
 
 4. Amphigenyte. The common lava of Vesuvius, contain- 
 ing a white potash-bearing mineral, called leucite (which is 
 garnet-like in its form) instead of a feldspar, and with it 
 pyroxene. 
 
 2. FELDSPATHIC SERIES. 1. Granite is here included so far 
 as it is an igneous rock. 
 
 2. Trachyte. Consists generally of orthoclase feldspar, 
 partly a glassy kind (sanidin), and has a rough surface. Horn- 
 blende is often sparingly present, and sometimes quartz. 
 
 3. Felsyte. Consists chiefly of orthoclase feldspar, like 
 ordinary trachyte, but is without glassy feldspar crystals and 
 has a smooth surface of fracture. Some quartz is often pres- 
 ent. Felsyte-porphyry consists of orthoclase in a compact con- 
 dition, with disseminated crystals of the same feldspar of a 
 paler color ; so that a polished surface is covered with angular 
 spots. The color is often red and the rock then resembles the 
 red porphyry mentioned under dioryte ; but its specific grav- 
 ity is under 2.75. 
 
 4. Lava. Any rock that has flowed in streams from a vol- 
 cano, especially if it contains cavities, or, in other words, is 
 
STRATIFIED ROCKS. 39 
 
 more or less scoriaceous. The most common kinds are 
 doleryte, peridotye, or trachyte in composition. 
 
 Scoria is a light lava, full of cavities ; and pumice, a white 
 or grayish feldspathic scoria, having the air-cells long and 
 slender, so that it looks as if it were fibrous. 
 
 Obsidian is volcanic glass, and Pitchstone and Pearlstone are 
 rocks that have a texture between that of stone and glass. 
 
 In the cooling of melted rock, the mass, if the process 
 goes on rapidly, may become glass throughout with only occa- 
 sional crystalline grains or stony points (called microlites 
 from their minuteness) scattered through it. With slower 
 cooling the stony points are more abundant, and may pre- 
 dominate, or they may make up the whole of the mass, 
 excepting perhaps some points which still remain as glass. 
 These peculiarities are detected only by the microscopic 
 investigation of thin slices. Frequently the microscope 
 detects an arrangement of the grains in lines indicating the 
 flow of the material when liquid, or what has been called a 
 fluidal structure. 
 
 II.-CONDITION, STRUCTURE, AND ARRANGE- 
 MENT OF ROOK-MASSES. 
 
 The rocks above described are the material of which the 
 great rock-masses or terranes of the globe consist. These 
 rock-masses occur under three conditions: 1. The Strati- 
 fied; 2. The Unstratificd ; 3. The Vein-form. 
 
 1. The Stratified condition. Stratified rocks are those which 
 lie in beds or strata. The word stratum (the singular of 
 strata) is from the Latin, and signifies that which is spread 
 out. The earth's rocky strata are spread out in beds of vast 
 extent, many of them being thousands of square miles in area 
 and thousands of feet in thickness. 
 
 The stratified rocks exposed to view over the earth far 
 exceed in surface the unstratified. They are the rocks of 
 
40 STKUCTUKAL GEOLOGY. 
 
 nearly the whole of the United States and of almost all of 
 North America, and not less of the other continents. Through- 
 out Central and Western New York, and the States south and 
 west, the rocks, wherever exposed, are seen to be made up of 
 a series of beds. And if the rocks are less distinctly strati- 
 fied over most of New England, it is, in general, only because 
 the structure has been partly obscured by the upturning and 
 crystallization which they have undergone since they were 
 formed. 
 
 Fig. 14. 
 
 The preceding figure represents a section of the rocks 
 along the river below Niagara Falls. It gives some idea of 
 the alternations which occur in the strata. In a total height 
 of 250 feet (165 feet at the Falls, at F, on the right) there 
 are, on the left, six different strata in view, and parts of two 
 others, the upper and lower, making eight in all. Number 1 
 is gray argillaceous sandstone ; 2, gray and red argillaceous 
 sandstone and shale ; 3, flagstone, or hard laminated sand- 
 stone ; 4, reddish shale and shaly sandstone ; 5, shale ; 6, 
 limestone ; 7, shale ; 8, limestone. Only two of these strata, 
 7 and 8, are in sight at the Falls (at F). The alternations 
 are thus numerous and various in all regions of stratified 
 rocks. Along the canon of the Colorado there are in some 
 places more than 8,000 feet of stratified beds, showing their 
 edges in lofty precipices, and in the mountains towering 
 above the adjoining plains. 
 
 It must riot be inferred that the earth is covered by a reg- 
 ular series of coats, the same in all countries ; for this is far 
 from the truth. Many strata occur in New York that are 
 not found in Ohio and the States west, and many in South- 
 
VEINS. 41 
 
 ern New York that are not in Northern ; and each stratum 
 varies greatly in different regions, sometimes being limestone 
 in one and sandstone or shale in another. 
 
 A stratum is a bed of rock including all of any one kind 
 that lie together, as either Nos. 1, 2, 3, 4, 5, 6, 7, or 8 in the 
 preceding figure. 
 
 A layer is one of the subdivisions of a stratum. A stratum 
 may consist of an indefinite number of layers. 
 
 A system includes all the various kinds of strata that were 
 formed in one age or period, as the Carboniferous system or 
 that of the coal era. A subdivision of a system, including 
 two or more related strata, is often called a series, or a group. 
 
 2. Unstratified condition. Unstratified rocks are those 
 which do not lie in beds or strata. Mountain-masses of 
 granite are often without any appearance of stratification. 
 The rock of the Palisades, on the Hudson, stands up with a 
 bold columnar front, and has no division into layers. Most 
 lavas of volcanoes have flowed out in successive streams ; 
 and, consequently, volcanic mountains are generally strati- 
 fied. But in some volcanic regions the rocks rise into lofty 
 summits without stratification. Although true granite bears 
 no marks of proper stratification, it very often passes insensi- 
 bly into gneiss, which is a stratified rock ; and there is evi- 
 dence in this fact that granite is often a stratified rock which 
 has lost the appearance of stratification in consequence of the 
 crystallization it has undergone. 
 
 3. Vein-form condition. When rocks have been fractured, 
 and the fissures thus made have been filled with rock-mate- 
 rial of any kind, or with metallic ores, the fillings are vein- 
 form, and called veins. Veins are large or small, deep or 
 shallow, single or like a complete network, according to the 
 character of the fractures in which they were formed. They 
 may be as thin as paper, or they may be rods in width. Figs. 
 15 to 18 represent some of the forms. In Fig. 15 there are 
 two veins, a and 6; in Fig. 16, a network of thin veins; in 
 Fig. 17, two, a, a, of very irregular form, a kind not uncom- 
 
42 
 
 STRUCTURAL GEOLOGY. 
 
 mon, and another, b, intersecting one of these; in Fig. 18, two 
 large veins, of still more irregular character cross one another. 
 
 Fig. 15. 
 
 Fig. 16. 
 
 Fig. 17, 
 
 Fig. 18. 
 
 Fig. 19. 
 
 ! 
 
 1 
 
 ' 
 
 !;' 
 
 ',!' 
 
 fi 
 
 1 
 
 
 
 ,' i 
 i 
 
 '; : ; 
 
 ''i 
 
 II 
 
 J 
 
 i'ii 
 
 'Si! 
 
 1.' 
 
 
 i. 
 
 ;f 
 
 ,1;- 
 
 '!;; 
 
 
 
 , ', 
 
 , 1 1 
 
 .' 
 
 I 1 
 
 y 
 
 
 
 !', 
 
 ' 
 
 ,1 
 
 'III 
 
 , ; 
 l'1'j 
 
 
 i 
 
 "i 
 'i 
 'It 
 
 1 
 
 Fig. 20. 
 
 ( . 
 
 Many veins have a landed structure, like Figs. 19 and 20. 
 
 Many metallic veins are thus banded, and have the ores 
 lying in one or more bands alternating with other stony 
 bands consisting of different minerals or rock-material, as 
 calcite, quartz, fluorite, etc., called the ganyue of the ore. 
 
STRUCTURE OF ROCKS. 43 
 
 In Fig. 20, representing a Cornwall lode, the middle por- 
 tion, I) c I, is made up of bands of agate, b, with two layers of 
 crystallized quartz, c, at centre ; a is a layer of quartz ; b, a 
 band of the copper ore of the vein, chalcopyrite 
 (copper pyrites) ; d, quartz with some fluorite. Flg * 21 
 
 When fissures have been filled with melted rock, 
 they are usually called dikes ; they have regular 
 walls, and are not banded, although sometimes 
 the sides differ a little from the middle. They 
 are often transversely columnar in structure; as 
 is illustrated in Fig. 21. 
 
 4. Relation of stratified and true unstratified rocks in the 
 earth's crust. The relations of the stratified and unstratified 
 rocks in the earth's crust will be understood after consider- 
 ing the origin of the crust. 
 
 The crust is believed to be the cooled exterior of a melted 
 globe. After the solidifying of the sphere at surface, the ocean 
 commenced at once to make fragmented stratified rocks over 
 the exterior through the wear of the crust-rocks, and the 
 stratifying of the sand or mud thus made ; while the contin- 
 ued cooling, going on very slowly, made unstratified rocks 
 beneath this first crust as its inner portion. The ocean thus 
 worked over and covered up with strata nearly all, if not all, 
 the original unstratified crystalline rocks. Hence the areas 
 of the unstratified rocks that were made in the first solidifi- 
 cation of the globe are of very small extent over the conti- 
 nents, if visible anywhere. 
 
 Geology has, for its study, chiefly stratified rocks. Much 
 the larger part of all the facts in geological history are de- 
 rived from rocks of this kind, and therefore the various details 
 with regard to their structure and arrangement are of the 
 highest importance. 
 
44 STRUCTURAL GEOLOGY. 
 
 / 
 
 
 
 Stratified Condition. 
 I. Structure. 
 
 1. Massive, laminated, and shaly structures. The massive 
 (Fig. 22, a), laminated (Fig. 22, &), and shaly (Fig. 22, c), 
 structures of layers have been explained on page 32. Sand- 
 stone is in general most perfectly laminated when argilla- 
 ceous, or containing much clay or fine earthy material The 
 same is true of limestone. The flagging stone used in most 
 Eastern cities for walks, is an example of a laminated sand- 
 stone, and of flags. It is from near Kingston, N. Y., and 
 other places on the west side of the Hudson. 
 
 2. Straticulate structure. The layers of a rock, as clays, 
 shales, sand-beds, sandstones, limestones, are often them- 
 selves stratified in a very thin manner, and while the thin 
 laminae separate easily in some cases (as in many clay-beds 
 and shales), they are indicated in others only by the banded 
 appearance of a surface of transverse fracture. The struc- 
 ture is straticulate. Only when the little layers are separable 
 is the structure laminated. 
 
 3. Beach structure. The structure of the upper part of a 
 beach is illustrated in Fig. 22, d. Instead of being composed 
 of evenly laid material, it consists of many irregular small 
 layers as deposited or thrown together by the waves during 
 storms. The lower part of the beach has an even slope of 
 usually 5 to 15 degrees, and the sands beneath are in beds 
 having the same slope. 
 
 4. Cross-bedded structure. In Fig. 22, e, the beds that are 
 obliquely straticulated or laminated are examples of the cross- 
 bedded structure. Such beds, which have sometimes great 
 extent, have resulted from the pushing along of the bottom 
 sands or earth by currents, causing at first a little elevation 
 or ridgelet, and then depositions successively over the front 
 or down-stream slope of the elevation. They alternate with 
 
STRUCTURE OF ROCKS. 
 
 45 
 
 other layers that are horizontal in bedding, because the in- 
 flowing tide alternates with the outflowing, or because, if of 
 fresh-water origin, such streams vary in flow from low water 
 
 Fig. 22. 
 
 to high. The succession of beds in Fig. e has been described 
 as the ebb-and-flow structure. It is common in stratified drift 
 as a result of river floods. 
 
 5. Flow-and-plunge structure. Where the waves plunge heav- 
 ily in connection with a flow of tidal or other currents, the 
 obliquely laminated layer is broken up into wave-like or 
 wedge-shaped parts, a few feet or yards long, as illustrated in 
 Fig. 23. This structure is common in stratified drift. 
 
 Fig. 23. 
 
 6. Quaquaversal or Wind-drift structure. Having the sub- 
 ordinate layers dipping in various directions, sometimes curv- 
 ing and sometimes straight, as shown in Fig. 22, /. The hills 
 of sand formed by the winds (as on a sea-coast or the shores 
 of large lakes) are usually thus stratified. The sands drifted 
 over the rising heaps form layers conforming to the outer sur- 
 face, and so may slope at all angles. In storms, the heaps 
 may be blown away in part, and afterward be completed 
 
46 
 
 STRUCTURAL GEOLOGY. 
 
 again; but the new layers will conform to the new outer 
 surface, and hence have a different direction. In this way, 
 by successive destructions and re-completions, a bed of sand 
 may be made which shall consist of parts sloping in one 
 direction and other parts in directions very different, with 
 numerous abrupt transitions, as illustrated in the figure. 
 
 Fig. 24. 
 
 Fig. 25. 
 
 7. Ripple-marks. A gentle flow of water, or its vibration, 
 over mud or sand, ripples the surface. The lighter winds 
 also make ripples over fields of sand. Layers of sandstone 
 and clayey rocks are often covered with ripple-marks (Fig. 
 24). 
 
 8. mil-marks. When the waters of a spreading or return- 
 ing wave on a gently sloping beach pass by shells or stones 
 lodged in the sand, the rills furrow out little channels. Fig. 
 25 shows such rill-marks alongside of shells (Lingulse) in a 
 Silurian sandstone. 
 
 9. Mud-cracks, earth-cracks. When a mud-flat is exposed 
 to the air or sun to dry, it becomes cracked to a few inches or 
 feet in depth. Fig. 26 represents mud-cracks in argillaceous 
 sandstone. Such cracks may subsequently become filled with 
 stony material, either sediment or material in solution ; and 
 
STKUCTURE OF ROCKS. 
 
 47 
 
 as such fillings are often made harder than the rock itself 
 they may stand as prominent ridges above a weathered surface 
 of the rock. It is actually a network of veins, but of very 
 shallow veins that were filled from above. In regions of 
 long droughts, the earth-cracks over prairies and alluvial 
 flats are sometimes many and deep, and over a foot wide. 
 
 Fig. 26. 
 
 Fig. 27. 
 
 Fig. 28. 
 
 10. Rain-prints (Fig. 27). The impressions of the large 
 rain-drops of a short shower made on a half-dry mud, have 
 often been preserved in the rocks. 
 
 11. Concretionary structure. Layers often contain small 
 spheres or disks of rock, which are called con- 
 cretions. They result from a tendency in mat- 
 ter to concrete or solidify around centres. 
 
 Some are no larger than grains of sand, or the 
 roe of fish, as in oolitic limestone (page 37). 
 Others are as large as peas or bullets, and 
 others a foot or more in diameter. 
 
 Fig. 28 represents a spherical concretion ; Fig. 29 a rock 
 made up of rounded concretions, having a concentric struc- 
 ture ; Fig. 30, one with flattened or disk-shaped concretions. 
 
 Concretions are usually spherical in massive sandstones. 
 lenticular in laminated sandstones or clays, and flattened disks 
 
48 
 
 STRUCTURAL GEOLOGY. 
 
 in argillaceous rocks or shales. All these kinds are shown in 
 Fig. 31. The balls are sometimes hollow, and the disks mere 
 rings. Frequently the concretions have a shell or other 
 organic object at centre (Fig. 32). They are often cracked 
 
 Fig. 29. 
 
 Fig. 30. 
 
 Fig. 31. 
 
 through the interior (Fig 33) from drying (some soft clayey 
 muds contracting to a tenth of their bulk) ; the outside in 
 such a case solidified while the inside was still moist. The 
 cracks may afterward become filled with other minerals. 
 
 Fig. 32. 
 
 Fig. 33. 
 
 Fig. 34. 
 
 Fig. 35. 
 
 Sometimes they contain a loose ball within, a concretion 
 within a concretion. A cavity lined with crystals (Fig. 34) is 
 called a geode. But the hollow balls so lined within are not 
 generally true concretions. 
 
 12. Columnar forms from con- 
 traction. a more or less perfect 
 columnar structure, due to con- 
 traction on cooling, is exemplified 
 often by igneous rocks, as repre- 
 sented in Fig. 35 and Fig. 119, 
 of page 145. The columns have 
 frequently transverse fractures, 
 but the fractures are usually less 
 
STRUCTURE OF ROCKS. 49 
 
 regular than in the preceding figure ; in many cases the top 
 of the sections of a column is concave upward, but often flat 
 and sometimes convex. The structure is sometimes found in 
 sandstone that has been heated, but generally the fracturing 
 so produced is very irregular. 
 
 13. Jointed structure, The rocks of a region are often di- 
 vided very regularly by numerous straight planes of fracture, 
 the most of them parallel to one another, and cutting through 
 vertically or at large angles to great depths. Such deep planes 
 of fracture may characterize the rocks over areas hundreds 
 of miles in extent. They are called joints ; and a rock thus 
 divided is said to present a jointed structure. In many cttses 
 there are two systems of joints or divisional planes in the 
 
 Fig. 36. 
 
 same region, crossing one another, and the undermining of 
 a bluff of jointed beds and tumbling down of masses leads 
 to the production of forms like those of fortifications or 
 broken walls, as shown in Fig. 36, representing a view 
 on the shores of Cayuga Lake. The directions of such joints 
 are facts which the geologist notes down with care. 
 
 14. Slaty cleavage. The term slaty has been explained on 
 page 33. But one important fact, not there stated, is that 
 the slates are often transverse to the bedding, that is, they 
 often cross the layers of stratification more or less obliquely, 
 instead of conforming to the layers or bedding like the shaly 
 structure. Slaty cleavage is in this respect like the jointed 
 structure; but it has the planes of fracture or divisional 
 
 4 
 
50 
 
 STRUCTURAL GEOLOGY. 
 
 planes so numerous that the rock divides into slates instead 
 of blocks ; and the two differ in mode of origin. Slaty cleav- 
 age is confined to fine-grained rocks. In Fig. 37 the lines of 
 bedding or stratification are shown at a, b, c, d, while the 
 
 Fig. 37. 
 
 Fig. 38. 
 
 transverse lines correspond to the direction of the slates. The 
 same is shown in Fig. 38 with the addition of a slight irreg- 
 ularity in the slates along the junction of two lasers. 
 
 2. Positions of Strata. 
 
 1. Original position of strata, horizontal position. Ordi- 
 dinary stratified rocks were once beds of sand or earth, or of 
 other rock-material, spread out by the currents and waves of 
 the ocean, or the waters of lakes or rivers, or by the winds. 
 
 When the larger portion of the beds over the North Amer- 
 ican continent were formed, the continent lay to a great 
 extent beneath the ocean, as the bottom of a great, though 
 mostly shallow, continental sea. The principal mountain- 
 chains the Eocky Mountains and the Appalachians had 
 not yet been made, and the surface of the submerged land 
 was nearly flat. The fact (1) that those beds were really 
 marine is proved by their containing, in most cases, marine 
 shells, crinoids, or corals, the relics of marine life ; and (2) 
 that the continental seas had great extent, by the fact that 
 the beds cover surfaces tens of thousands of square miles in 
 area, some of them reaching from the Atlantic border west- 
 ward beyond the Mississippi. In the large continental seas, 
 the deposits made by means of the currents and waves were 
 ; nearly or quite horizontal. As they increased, they would near 
 
POSITIONS OF STRATA. 
 
 51 
 
 the surface ; and here the action of the waves would tend to 
 chisel off and keep level the upper surface of the beds, whether 
 accumulations of sand or earth, or of shells or corals. If the 
 bottom over the region were very slowly sinking, the accumu- 
 lations might go on thickening, and the beds continue to 
 have the same level or horizontal position. Strata formed 
 along the borders of rivers and lakes have horizontal beds, 
 and so have those on the borders of the ocean; and for a 
 like reason, that the water works through, or with a reference 
 to, its surface, which is horizontal. Moreover, the bottom of 
 tho border of the Atlantic, south of Long Island, is (see Fig. 
 3, p. 12), for eighty miles from the coast-line, so nearly hori- 
 zontal that it deepens only 1 foot for every 600 to 700 ; and if 
 the area were above the ocean, no eye would detect that it 
 was not perfectly level. 
 
 Other beds were originally vast marshes, like the marshes 
 of the present day, only larger. Such was the condition of 
 the beds in the coal-formation that are 
 now coal. Many coal-beds contain 
 stumps of trees rising out of the coal 
 (Fig. 39) ; and they always stand verti- 
 cally on the bed, however much the lat- 
 ter may be displaced, showing that the 
 bed was horizontal when it was formed, 
 or when the trees were growing. 
 
 Exceptions to a horizontal position. When a river empties 
 into a lake or sea, the bottom of which, near its mouth, is 
 more or less inclined, the deposits of detritus made by the 
 
 Fig. 40. 
 
 Fig. 39. 
 
 river will for a while conform to the slope of the bottom, 
 as in Fig. 40. When rivers fall down precipices, they make 
 
52 STRUCTURAL GEOLOGY. 
 
 a steep bank of earth at the foot, whose layers, if any are 
 made, have the slope of the bank. In beach-made deposits 
 the layers have the slope of the beach (page 44). But these 
 and similar cases of exceptions to a horizontal position are of 
 small extent. 
 
 2. Dislocations of strata. Most of the strata of the globe 
 have lost their original horizontal position so as to be more or 
 less inclined ; and some are even vertical. They are occasion- 
 ally bent or folded, as a quire of paper might be folded, only 
 the folds are miles, or scores of miles, in sweep. 
 
 They have often also been fractured, and the separated 
 parts have been pushed, or else have fallen, out of their 
 former connections, so that the portion of a stratum on one 
 side of a fracture is often inches, feet, or even miles, above 
 that on the other side. 
 
 It is stated on page 1, that a thickness of rock equal to 18 
 or 20 miles is open to the geological explorer. This could 
 not be true were all strata in their original horizontal posi- 
 tion ; for in that case the most that would be within reach 
 would not exceed the height of the highest mountain. But 
 the upturning which the earth's crust has undergone has 
 brought the edges of strata to the surface, and there is hence 
 no such limit: however deep stratified beds may extend, 
 there is no reason why the whole should not be brought up 
 so as to be exposed to view in some parts of the earth's 
 surface. 
 
 The following are explanations of the terms used in de- 
 scribing the positions of strata : 
 
 7. Outcrop. The portions or ledges of strata projecting 
 out of the ground, or in view at the surface (Fig. 41). 
 
 2. Dip. The angle of slope of inclined or tilted strata. 
 In Figs. 41, 42, d p is the direction of the dip. Both the 
 angle of slope and the direction are noted by the geologist : 
 thus, it may be said of beds, the dip is 50 to the south, or 
 45 to the northwest, etc. 
 
 When only the edges of layers are exposed to view, it is 
 
DISLOCATIONS OF STRATA. 
 
 53 
 
 not safe to take the slope of the edges as the slope of the 
 layers ; for in Fig. 42 the edges on the faces 1, 2, 3, 4 are 
 
 Fig. 41. 
 
 all edges of the same beds, and only those of the face 1 
 would give the right dip. 
 
 The dip is measured by means of instruments called clino- 
 meters. In Fig. 43, abed represents a square block of 
 
 Fig. 43. 
 
 wood, having a graduated arc I c and a plummet hung 
 below a. Placed on the sloping surface A B, the position 
 
54 STRUCTURAL QEOLOGY. 
 
 of the plummet gives the angle of dip. This kind of clino- 
 meter is often made in the form of a watch and combined 
 with a compass. It is most convenient for use when it has 
 a square base. One like that figured is easily made out of a 
 piece of board ; it may be 3 to 4 inches on a side, and half 
 an inch or so thick. To avoid errors from the un evenness of 
 a rock, a board should be laid down first and the measure- 
 ment be made on its surface. But if the instrument has 
 a square base it is often best to measure the dip by holding 
 it between the eye and the rock, with one edge of the base in 
 the direction of the dipping layers. 
 
 8. Strike. The horizontal direction at right angles with 
 the dip. In Fig. 41, the dotted line s t represents the direc- 
 tion of the strike. It is measured by means of a small com- 
 pass which usually forms part of the clinometer. Such a 
 compass may be set in a clinometer made like the above 
 figure (Fig. 43). It need not be central in the square, but 
 should have the meridian line parallel to one of the four 
 sides. If the edges of the layers in view over a ledge are in 
 any part quite horizontal, the direction of those edges will 
 give the true strike ; but if they are at all inclined, a hori- 
 zontal line should be drawn, if possible, on the surface of 
 one of the layers. The clinometer may be used also for 
 measuring the dip of rocks that are rods distant, and the 
 slopes of distant mountains. 
 
 4. Fault. In the making of faults (aa, bb, Fig. 44) there 
 
 is first a fracturing, and then a 
 
 ^ Fig. 44. shoving up or down of the beds 
 
 on one side of the fracture ; that 
 is, a downthrow on ,one side or 
 an upthrow on the other. The 
 amount of displacement is the 
 amount of fault ; it may be a 
 foot or less, or 10,000 feet or more. 
 In Fig. 17, on page 42, the vein a is faulted along the line 
 of b. The friction attending the downthrow may cause a 
 
DISLOCATIONS OF STRATA. 
 
 55 
 
 bending of the layers in contact, as along the line bb, in 
 Fig. 44. The deepest fractures and faults have been produced 
 in connection with the making of mountains. 
 
 5. Folds or flexures. Folds or flexures in strata are repre- 
 sented in the following sections ; Fig. 45, A, B, and in the nat- 
 
 Fig. 45. 
 
 ural section, Fig. 46, from the Appalachian Mountains, a region 
 of numerous flexures on a grand scale, as well as of many faults ; 
 some flexures having a span of several miles, and others of 
 only a few feet or inches. 
 
 In Fig. 45, ax is the axis or axial plane of the fold. 
 
 Fig. 46. 
 
 The flexure very often has one side steeper than the other, 
 as illustrated above. In some regions the push by which they 
 were made w T as continued until the fold became vertical; 
 and, further still, until the top was pressed over beyond the 
 vertical, and fold of this kind followed fold, as illustrated in 
 Fig. 47. In more extreme cases 
 the push has continued until there 
 has been produced a complete over- 
 turn or inversion of the beds, as is 
 represented in the following section 
 (by Eenevier) from the Alps east of the Ehone, the whole 
 height of whic> is 6,500 feet. The bed A, which before 
 the folding was the uppermost stratum is folded back on 
 itself for more than three miles; and B, C, D, E, which 
 
 Fig. 47. 
 
56 
 
 STRUCTURAL GEOLOGY. 
 
 Section West to East. A, upper Eocene; B, 
 Nummulitic beds, or lower Eocene ; C, D, E, 
 Cretaceous (E. Neocoraian); G, Jurassic lime- 
 stone ; H, Carboniferous ; I, Metamorphic ; 
 M, Dent tie Morcles. 
 
 were originally underlying 
 strata, now overlie it, up- 
 side down. It is seen 
 that the strata C, D, E 
 are present only in the 
 overturned part of the fold ; 
 these beds must have cov- 
 ered G to the westward and 
 not to the eastward. 
 
 Flexures often have frac- 
 tures somewhere along the 
 bend ; and the fractures are 
 often lines of faults. 
 
 6. Anticline. An upward bend in the strata, sloping away 
 from a common plane in opposite directions, as the layers 
 either side of a. x in Fig. 45 A : the axis is here called an 
 anticlinal axis. The word anticline is from the Greek dvrl, 
 in opposite directions, and ic\ivw, I incline. 
 
 7. Syncline. A downward bend, the strata sloping toward 
 a common plane. In Fig. 45 B, a x, a x are anticlinal axes, 
 a f x f , between the others, a synclinal axis. The word syncline 
 is from the Greek avv, together, and /c\ivo). 
 
 8. Monocline. Having the strata sloping in only one direc- 
 tion, as when strata are fractured and those of one side are 
 lifted along the fracture. The word monocline is from the 
 Greek /JLOVOS, one, and K\LVW. 
 
 9. Geanticline, Geosyncline. Bendings of the earth's crust, 
 geanticline an upward bend, and geosyncline a downward bend. 
 These words are from the Greek for earth and the words anti- 
 cline and syncline. 
 
 In ordinary synclines and anticlines the flexures are those 
 of the strata which overlie the earth's crust. The bendings 
 of the earth's crust are necessarily of very small angle and 
 broad span, on account of its thickness ; one of 10 in a crust 
 25 miles thick with a span of only 25 miles is not to be 
 looked for. 
 
UNCONFORMABLE STRATA. 
 
 57 
 
 Fig. 49a. Fig. 49b* 
 
 The subject of flexures and faults is best studied by mak- 
 ing models out of sheets of moist clay (or better of paraffine 
 containing a little beeswax), using lampblack and red and 
 yellow ochre for coloring the different beds, and then making 
 cross-sections. 
 
 10. Effects of denudation on Flexed or Upturned Rocks ; Decapi- 
 tated Folds. If the top of the fold in Fig. 49 a were cut off at 
 a b, there would remain the part 
 represented in Fig. 49 b, in which 
 there is no appearance of any fold, 
 and only a uniform series of dips; 
 and although 1', 2', 3' appear to 
 be the lower strata of the series, 
 they are actually parts of 1, 2, 3. 
 
 A long series of such folds pressed together, and then decapi- 
 tated, would make a series of uniform dips over a wide ex- 
 tent of country, obscuring wholly the true stratification. 
 
 This obscuring of the true succession has been greatly in- 
 creased by the removal of the beds over great areas and the 
 filling up of intermediate depressions by soil: so that the 
 
 Fig. 50. 
 
 L 2 3 3'2'r 
 
 rocks are visible only at long intervals (as in Fig. 50). Many 
 
 of the difficulties in the study of rocks arise from this cause. 
 
 11. Unconformable strata. When strata have been tilted, 
 
 or folded, and, subsequently, horizontal beds have been laid 
 
 Fig. 51. 
 
 down over them, the two sets are said to be unconformable 
 because they do not conform in dip. It is a case of uncon- 
 formability in the stratification. Tims, in Fig. 51 the beds 
 
58 STRUCTURAL GEOLOGY. 
 
 a b are unconformable to those below them ; so also the tilted 
 beds c d are unconformable to those beneath, and the beds e f 
 to the beds c d. 
 
 It is plain that the folded rocks represented in Fig. 51 are 
 the oldest, and that the folding took place before the overly- 
 ing beds were deposited. Again, it is evident that the beds 
 below the line c d are older than the beds between c d and e f, 
 and also that they were tilted and faulted before the latter were 
 formed. Supposing the underlying folded or upturned rocks 
 were those of the Alps : if the upper of them were of the age of 
 the Chalk (the Cretaceous period) and contained marine fossils, 
 showing them to be of marine origin, and the unconformably 
 overlying beds belonged to some division of the Tertiary, the 
 geologist would conclude that the upturning, in which the 
 mountains were lifted above the sea, occurred after the period 
 of the Chalk, and before that to which the Tertiary beds 
 belonged. Or, if the latest underlying marine beds were of 
 the 1st period of the Tertiary, and the overlying of the 2nd 
 period, then the time of uplift would be more narrowly de- 
 termined as directly following the first of these periods. 
 These examples illustrate the importance to geology of obser- 
 | vations on unconformability in stratification. 
 
 Unconformability of overlap is a kind in which there is 
 scarcely any appreciable unconformability in dip, and no 
 upturning was concerned. It exists when the sea of one 
 era, after depositing horizontal beds, has, in the following 
 era, spread far over the land and has deposited another series 
 of beds with these new limits. These changes of sea-level 
 were going forward during the progress of most formations, 
 and, consequently, unconformability through overlap should 
 be common, though not always easily distinguished. 
 
 3. Order of Arrangement of Strata. 
 
 It has been explained that the strata are historical records 
 as to the past conditions of the earth's surface. In order 
 
EQUIVALENCY OF ROCKS. 59 
 
 that the records may make an intelligible history, there 
 must be some way of arranging them in their proper order, 
 that is, in the order of time. The determination of this order 
 is one of the first things before the geologist in his exam- 
 inations of a country. 
 
 Many difficulties are encountered. 
 
 1. The strata of the same period or time called equiva- 
 lent strata, because approximately equivalent in age differ, 
 even on the same continent. Sandstones and shales were 
 often forming along the Appalachians in Pennsylvania and 
 Virginia, when limestones were in progress over the Missis- 
 sippi Valley. The chalk-formation in England contains thick 
 strata of chalk ; but in Eastern North America the same for- 
 mation exists without any chalk. 
 
 2. When rocks have been forming in one region, there 
 have been none in progress in many others. Hence the series 
 of strata serving as records of geological events is nowhere 
 perfect. In one country one part may be very complete ; in 
 another, another part ; and all have their long blanks, that 
 is, large parts of the series entirely wanting. In New York 
 and the States west to the Mississippi, there is only part of 
 the lower half of the series. In New Jersey there is part of 
 the lower half and part of the upper half, with wide breaks 
 between. Over a large part of Northern New York there 
 exist only the very earliest of rocks. 
 
 The thickness of the fossiliferous series in the State of 
 New York, south of its centre, is about 13,000 feet, and north 
 of its centre they thin out to a few feet ; in Pennsylvania, 
 the thickness is about 30,000 feet (Lesley) ; in Indiana and 
 other adjoining States west and south, 3,500 to 6,000 feet. 
 In Great Britain, the whole thickness above the unfossiliferous 
 bottom-rocks is over 100,000 feet. 
 
 3. The rocks of a country are to a great extent covered 
 with earth or soil, so that they can be examined only at dis- 
 tant points. 
 
 4. The strata, in many regions, have been displaced, 
 
60 STRUCTURAL GEOLOGY. 
 
 folded, fractured, faulted, and even crystallized extensively, 
 adding greatly to the difficulties in the way of the geological 
 explorer. 
 
 The following are the methods to be used in determining 
 the true order of arrangement : 
 
 A. In sections of the rocks exposed to view in the sides 
 of valleys or ridges, the order should be directly studied, 
 and each stratum traced, as far as possible, through all the 
 exposed sections. 
 
 When, through large intervals, a covering of soil or water 
 prevents the tracing of the beds, other means must be used. 
 
 B. The aspect or composition of the rock may help to 
 determine which strata are identical. But this method 
 should be used with great caution, for the reason stated 
 above, in 1, that rocks made at the very same time may be 
 widely different ; and, conversely, those made in very differ- 
 ent periods may look precisely alike in color and texture. 
 
 C. Fossils afford the best means of determining identity. 
 This is so because of the fact, already mentioned, that the 
 fossils of an epoch are very similar in genera if not also 
 in species the world over ; and those of different epochs 
 are different in these respects. The geologist, by studying 
 the fossils of the several beds at any locality, learns which 
 kinds are characteristic of each bed, and the order of succes- 
 sion. Then, by comparing the beds of different localities, he 
 ascertains whether any are essentially alike in species, and 
 therefore of like age or period, and from this determination 
 continues further his study of the order of succession. By 
 pursuing this course, for all accessible localities over a coun- 
 try, and different countries, geologists have ascertained the 
 characteristic kinds of fossils for the successive strata through 
 the long series of formations ; and the lists which have been 
 thus made serve for the identification of strata in widely dis- 
 tant regions. By a comparison of fossils it was proved that 
 the chalk-formation exists in Eastern North America, al- 
 though there is no chalk to be found there. In the same 
 
EQUIVALENCY OF KOCKS. 61 
 
 manner, the equivalents in America of the principal subdivi- 
 sions of the rock series of Britain and Europe, Asia, and even 
 Australia, are approximately ascertained ; for this means of 
 determination is a universal one, applying to the equivalency 
 of rocks in different hemispheres as well as those on the same 
 continent. 
 
 This method has its doubts. These doubts arise (1) from the 
 fact that one continent may have received part of its species 
 from another long after their first appearance on that other ; 
 and, (2) from another fact, that the exterminations of species 
 which have taken place at the close of a period may have 
 been far more complete in one region than another, so that 
 certain species were living long in one after their disappear- 
 ance from the other. Again, there are doubts arising (3) from 
 the fact that, in any period, the life of one locality is very dif- 
 ferent from that of another, on account of differences in purity 
 of waters, muddy or rocky bottom, and temperature. The 
 removal of all doubts, especially with respect to the minor 
 subdivisions of the geological series on different continents, 
 or distant parts of the same continent, is not to be looked 
 for. Yet, by proceeding with care, and using not isolated 
 facts, but the whole range afforded by the fossils, animal as 
 well as vegetable, the general order of succession may be 
 made out for each country, if not the precise parallelism for 
 different countries. 
 
PART III. 
 
 DYNAMICAL GEOLOGY. 
 
 DYNAMICAL GEOLOGY treats of the causes or origin of 
 events in geological history, that is, of the origin of rocks, 
 of disturbances of the earth's strata and the accompanying 
 effects, of valleys, of mountains, of continents, and of the 
 changes in the earth's features, climates, and living species. 
 The agencies of most importance, next to. the universal 
 power of Gravitation and Cohesive and Chemical attraction, 
 are Life, the Atmosphere, Water, and Heat. 
 
 The following are the subdivisions of the subject here 
 adopted: 1. Life; 2. The Chemical action of the Atmosphere 
 and Waters; 3. Mechanical effects of the Atmosphere; 4. Me- 
 chanical effects of Water ; 5. Action of Heat ; 6. Movements 
 in the earths crust, and their consequences, including the fold- 
 ing and uplifting of strata, and the origin of mountains 
 and of the earth's general features. 
 
 I. - LIFE. 
 A. Formative Effects. 
 
 Life has done much geological work by contributing mate- 
 rial for the making of rocks. Nearly all the limestones of 
 the globe, all the coal, and some siliceous beds, besides por- 
 
ORGANIC MATERIALS OF ROCKS. 
 
 63 
 
 tions of rocks of other kinds, have been formed out of the 
 stony relics of living species. Both animals and plants have 
 been large sources of the material. The skeletons or stony 
 secretions of animals, after f ulrilling the purposes of life, have 
 been turned over to the mineral kingdom, to be made into 
 minerals and rocks. Similarly, from vegetable structures 
 have come beds of stone as well as beds of coaL 
 
 1. KINDS AND SOURCES OF ORGANIC MATERIALS. 
 
 A. Calcareous material, or that of which limestones consist, 
 has been derived chiefly from the following sources. 
 
 1. SHELLS OF MOLLUSKS. These include : 
 
 (1.) The ordinary bivalve shells, like the oyster and clam 
 (described on page 182 as Lamellibranch Mollusks). 
 
 Figs. 52-59, BBACHIOPOD MOLLUSKS. 
 
 BRACHIOPODS. Fig. 52, Waldheimia flavescens, interior view ; 53, loop of Tere- 
 bratula vitrea ; 54, id. Terebratulina caput-serpentis ; 55, Spirifer striatus ; 56, same, 
 interior of dorsal valve ; 57, Atliyris concentrica ; 58, 59, Atrypa reticularis, the latter 
 dorsal valve. 
 
 (2.) Other bivalve shells (those of Brachiopod Mollusks) 
 having symmetrical forms, as illustrated in Figs. 52 to 
 59. Figs. 52, 56, 59 show the characters of the interior of 
 
64 
 
 DYNAMICAL GEOLOGY. 
 
 the shells. In ancient time the shells of this tribe exceeded 
 all others in abundance, but now they are relatively few. 
 
 (3.) The univalves (shells of Gasteropod Mollusks), having 
 commonly spiral forms : like the snail and the kinds repre- 
 sented in Figs. GO to 65. 
 
 Figs. 60-65. 
 
 Figs. 66, 67, CORALS. 
 
 GASTEROPODS. Fig. 60, Pyrifusus Newberryi; 61, 62, Bulla speciosa;63, An- 
 clmra (Drepanoclieilus) Americana ; 64, Fasciolaria buccinoides ; 65, Margarita Nebra-S' 
 censis. 
 
 (4.) Other species (Cephalopods) some of which are repre- 
 sented in Figs. 347-351, on page 298. Besides these there 
 are still others (Bryozoans) which make small coral-like 
 and encrusting forms, illustrated on page 181. 
 
 2. CORALS (Figs. 66, 
 67). The stony secre- 
 tions, mainly of Polyps. 
 They contributed large- 
 ly to the older rocks of 
 the world and are still 
 making great lime- 
 stone formations. Fi<? 
 
 66 represents a living 
 coral, and 67, a fossil 
 species. 
 
 There are also Millepore or Hydroid Corals (page 184) 
 among the limestone-making species. 
 
ORGANIC MATERIALS OF ROCKS. 
 
 65 
 
 3. CRINOIDS. Species of 
 Echinoderms (page 184) hav- 
 ing radiating arms above, 
 about the mouth, and a 
 stem usually, for attachment, 
 the whole made of small cal- 
 careous pieces. Some lime- 
 stones were formed chiefly 
 from remains of Crinoids. 
 Of the three figures given, 
 68 represents an ancient kind 
 (reduced), and 70 is a living 
 Atlantic species (natural 
 size), from Wy ville Thomson' s 
 " Depths of the Sea," a 
 kind that plants itself in the 
 mud of the sea-bottom by 
 means of the appendages at 
 the base of the stem, instead 
 of being firmly attached or 
 rooted. Fig. 69 represents a 
 portion of a mass of ancient 
 limestone made up of frag- 
 ments of the stems of crin- 
 oids. The few existing spe- 
 cies occur in the ocean 
 at various depths to 2435 
 fathoms, but are most com- 
 mon between 80 and 400 
 fathoms. 
 
 4. FORAMINIFERS OR CAL- 
 CAREOUS SHELLS OF EHIZO- 
 
 PODS. These shells (Figs. 
 71-84) are mostly very small, 
 and yet through their abun- 
 dance they have been very im- 
 
 Figs. 68-70, 
 
 CRINOIDS : Fig. 68, Apiocrinus Roys- 
 sianus (a , lower part of stem ) ; 69, portion 
 of a mass of prinoidal limestone ; 70, Pen- 
 tacrinus Wyville-Thomsom. 
 
66 
 
 DYNAMICAL GEOLOGY. 
 
 portant in limestone-making. In size they are generally 
 between a grain of sand, and an eighth of an inch ; but Figs. 
 83 and 84 are of natural size, and still larger occur. They 
 are all marine, the fresh-water species not having calcareous 
 
 Pigs. 71-84, FORAMINIFERS, OR SHELLS OF RHIZOPODS. 
 
 Fig. 71 Orbnlina universa 72, Globigerina rubra ; 73, Textilaria globulosa, Ehr. ; 74, Rotalia 
 globulosa ; 74 a, Side-view of Rotalia Boucuna ; 7. r >, Grammostomum phyllodes Ehr. ; 
 76, Frondicularia annularis ; 77, Triloculina Josephiiia ; 78, Nodosaria vulgaris ; 79, Lit- 
 uola nautiloides ; 80 a, Flabellina rugosa 81, Chrysalidina gradata : 82 a, Cuneolina 
 Pavonia : 83, Nummulites nuinmularia : 84 a, b, Fusulina cyliudrica. 
 
 shells. Some kinds belong especially to the border region of 
 the ocean (Textilarias, Rotularias, Nodosarias, etc.), while 
 others (Globiyerinas, Fig. 72 etc., and Fig. 171, page 185) be- 
 long to the open sea, or are pelagic kinds. The latter often 
 make the fine mud or ooze of the sea-bottom in latitudes 
 inside of 60, constituting what is called the Globigerina 
 ooze. The chalk was made mainly of such materials. 
 
 5. SOME MARINE PLANTS, as (1) the Nullipores, which look 
 like corals but have no cells whence the name signifying 
 no pores ; (2) the Corallines, which are delicate, semi-calcare- 
 ous sea-plants ; (3) Ooccolitks, minute stony disks of a one- 
 celled sea-plant (named from KOK/COS, seed), and the related 
 Rhabdolitlis which are rod-like in shape. 
 
 B. Siliceous material of organic origin is far less abundant 
 than calcareous ; for quartz is mostly from mineral sources. 
 
ORGANIC CONTRIBUTIONS TO ROCKS. 
 
 67 
 
 Figs. 85-87, RADIOLABIANS. 
 
 1. ANIMAL IN ORIGIN. (1.) Many Sponges afford siliceous 
 spicules. The forms of some of the spicules are shown in 
 Figs. 250, 251, on page 234, and their fragments, among the 
 Diatoms in the figure on page 68. The horny fibres which 
 make up a sponge constitute the skeleton of a multitudinous 
 group ot minute sponge-animals which are somewhat related 
 to the Khizopods, The spicules, when present, occur within 
 these fibres and often bristle their surface. (In some sponges 
 they are calcareous.) Other sponges, like that of Fig. 374, 
 page 314, have the whole skeleton of silica; and these, 
 which are called (/lass or vitreous sponges, grow over the 
 ocean's bottom at various depths, but most abundantly be- 
 tween 90 and 100 fathoms. 
 
 (2.) The Eadiolarians (Figs. 85-87) are marine Khizopods 
 having siliceous shells 
 (often lacework-like), 
 which are usually sym- 
 metrical about the centre 
 or central line, and some- 
 times spherical. The 
 name is from the Latin 
 for radial. Another kind 
 is represented on page 
 
 186. They live in all zones. The Challenger expedition found 
 a "Radiolarian ooze" at depths between 11,000 and 23,000 
 feet. 
 
 2. VEGETABLE IN ORIGIN. Minute plants, called Diatoms 
 (from two Greek words referring to a subdivision which takes 
 place in the process of reproduction), have siliceous shells. 
 Some kinds are represented (part of them broken) in Fig. 
 88 ; they are from an earthy deposit near Richmond in Vir- 
 ginia. They grow so abundantly in both fresh and salt 
 waters that they make thick chalk-like deposits, and those 
 of the deep ocean, between 6,000 and 12,000 feet, are very 
 extensive. They live near the surface, and in certain parts of 
 the ocean, the Polar seas included, they often tint the 
 
68 
 
 DYNAMICAL GEOLOGY. 
 
 Fig. 88, DIATOMS. 
 
 water, and are sometimes massed together, they are so 
 abundant. Many sea-animals live on them. The flint, chert 
 and jasper, which form nodules and sometimes layers in lime- 
 stone and other rocks, have been 
 made largely from spicules of 
 Sponges, or the shells of Eadi- 
 olarians or Diatoms. 
 
 C. Phosphatic material, chief- 
 ly Calcium phosphate. Ver- 
 tebrate animals (Fishes, Am- 
 phibians, Eeptiles, Birds, and 
 Mammals or Quadrupeds) have 
 contributed very little calcare- 
 ous material to the rocks, com- 
 pared with inferior tribes of ani- 
 mals. But they have been an 
 important source of phosphate 
 salts, and the deposits are often 
 worked because the material 
 Bones, scales, and, to some extent, 
 all animal tissues of vertebrates and invertebrates contain 
 phosphatic material. The mineral apatite, common in many 
 crystalline limestones, is a calcium phosphate, and has some- 
 times had this source. Guano, which owes its value largely 
 to its phosphates, has been made chiefly from the excrements 
 of birds in dry regions where the birds long had undisturbed 
 possession ; as on some small coral islands in the Central 
 Pacific, islands off the Peruvian coast, the coast of equatorial 
 Africa, and in the Caribbean Sea. 
 
 Coprolites, or isolated excrements of reptiles and fishes, and 
 sometimes of other animals, occur in many rocks. Vegetable 
 tissues also afford phosphates, 100 parts of the ashes of ordi- 
 nary meadow grass affording 8 parts of phosphoric acid ; of 
 rye-straw, 4 parts; of clover, 18 parts; oc seaweeds, 1 to 5 
 parts. 
 
 The shells of certain Brachiopods the Lingnla and some 
 
 is valuable as a fertilizer. 
 
ORGANIC CONTRIBUTIONS TO ROCKS. 69 
 
 related species are largely phosphatic. These shells and 
 the shells of Crustaceans when fossilized are usually black, 
 because of the large amount of animal matter they contain, 
 this portion becoming carbonized. 
 
 D. Carbonaceous material. The most abundant contribu- 
 tions from the vegetable kingdom to rocks are the beds of 
 mineral coal, coal being made from woody tissues. Mineral 
 oil has in part the same source, and partly is of animal origin. 
 Graphite, which is pure carbon, is often also of vegetable 
 origin, coal sometimes occurring changed to graphite when 
 it has been subjected to high heat under pressure. Carbona- 
 ceous matters, of vegetable or animal origin, give the black 
 color to black limestones and most shales, as is proved by 
 the fact that when such rocks are burnt they become white, 
 owing to the combustion of the carbonaceous part. Diamonds 
 have probably been formed from the carbonaceous materials 
 of a shale, by long subjection to heat and moisture, under 
 peculiar conditions yet unexplained. 
 
 E. Aquatic species the largest rock-makers The kinds of 
 life which have contributed most material to the earth's rock- 
 formations, and which are most common as fossils, are the 
 aquatic, and particularly the marine. This is so because (1) 
 the accumulation of material making beds of rock has been 
 done mostly by the sea ; because (2) the species which have 
 the most stony matter in the structures, viz. corals, crinoirls 
 and shells are, with small exceptions, under the last division, 
 aquatic, and nearly all are marine; because (3) the animal 
 remains which are in the water readily become buried by 
 new depositions of clay or sand through the currents or 
 waves, and thus have a protection from destruction not 
 afforded to any extent to species of the land ; because (4) the 
 water and this kind of burial also serve often as a preventive 
 of complete decay. Coal has been made only where the 
 plants grew in or near marshes or shallow lakes, or were 
 drifted into bays or lakes ; for the leaves that fall in the dry 
 woods undergo complete decomposition, and pass away in 
 
70 DYNAMICAL GEOLOGY. 
 
 gaseous combinations. The bones of animals dropped over 
 the land disappear by becoming the food of other animals as 
 well as by decay; while those living about the shores of 
 lakes have often become buried in lacustrine deposits of clay 
 or finer earth, and thus have had their bones preserved. Mas- 
 todons have been mired in marshes and their skeletons pre- 
 served whole, while the thousands that died over the dry land 
 left no relics. 
 
 F. Fossilization. Shells, bones, corals, etc., after f ossiliza- 
 tion, have rarely their original composition. They have in 
 almost all cases lost at least the animal matter they con- 
 tained; frequently they are changed to quartz, sometimes 
 to pyrite, oxide of iron, or dolomite, and occasionally to an 
 ore of copper, or to a silicate of some kind. Wood is often 
 changed to quartz or to limestone. 
 
 2. GEOGRAPHICAL DISTRIBUTION OF MARINE LIFE. 
 
 The distribution of species is an important subject to the 
 geologist, but especially that of marine species, since the 
 stratified rocks and their fossils are very largely of marine 
 origin. 
 
 1. General Distribution in the Ocean. Eecent investigations 
 have shown that living species not only inhabit the bordei 
 regions of the oceans, but also extend widely and abundantly 
 over a large part of the ocean's depths. Fishes, Crabs and 
 other Crustaceans, Sea-worms, Echini, Star-fishes, Crinoids, 
 Corals, are abundant to depths of 10,000 to 13,000 feet, and 
 some of them to 18,000 feet. Crustaceans of large size, 
 allied to shrimps, many of them with good eyes, have been 
 found at all depths to 2,900 fathoms ; and large crabs, with 
 perfect eyes, at 1,700 fathoms. Some species have a very 
 wide range in depth ; one Coral (a disk-shaped kind, Bathy- 
 actis symmetrica) occurs (states Moseley) at depths from 30 
 to 2,900 fathoms. 
 
 2. Character of the Sea-bottom. The material of the ocean's 
 
DISTRIBUTION OF MARINE LIFE. 71 
 
 bottom is generally a fine grayish mud or ooze. But over 
 vast regions above 13,000 feet in depth occurs the Globigerina 
 ooze, and at these and greater depths other areas of Diatom 
 ooze, and smaller of Radiolarian ooze. 
 
 The character of the bottom shows that sediments from the 
 rivers of the continents are not carried far out to sea. Stones 
 of a pound weight, and larger, occur 100 miles southeast of 
 Long Island ; but these are supposed by Verrill to have been 
 carried out by shore ice. Clay with some fine quartz sand 
 and particles of mica make up the gray ooze ; and the winds 
 may be a principal source of the sand and mica. Pumice 
 and fine materials of volcanic origin are also widely distrib- 
 uted, indicating that the driftings by the winds from volcanic 
 islands have been to great distances and over very large areas. 
 The ooze has often a reddish color, which is attributed to the 
 oxidation of the iron of the pyroxene or hornblende in vol- 
 canic cinders ; and grains and nodules of oxide of manganese, 
 probably from the same source, are very common over the 
 ocean's bottom. 
 
 The bottom is the receiving place of all the dead remains 
 of the ocean's life, both plant and animal, exclusive of the 
 very large part that does not have a chance to reach the bot- 
 tom, because of the eaters. In the Challenger expedition, the 
 dredge, in one region, brought up a hundred or more shark's 
 teeth, and between 30 and 40 ear-bones of Cetaceans or ani- 
 mals of the whale tribe. Among the shark's teeth, one was 
 four inches wide at base, and apparently an Eocene tooth ; and 
 its being buried not more than a foot, although lying there 
 since the early Tertiary, is regarded as evidence of the very 
 small amount of detritus that falls over the bottom. 
 
 3. Causes limiting Distribution. The two prominent physi- 
 cal causes limiting distribution are the amount of (1) heat, 
 and (2) light. 
 
 a. Temperature. The temperature of the waters varies (1) 
 with the zones, from 90 F. in the tropics to 32 F., and even 
 28 F., in the polar seas ; (2) with the distribution of marine 
 
72 DYNAMICAL GEOLOGY. 
 
 currents, the warm currents from the equatorial regions, and 
 the cold from high latitudes ; (3) with the depth, the temper- 
 ature diminishing downward to 35 F. as a general thing, but 
 in some places to 28 in the polar regions and polar currents. 
 In depth, there is in the tropics a temperature of 45, and 
 often of 40, within 300 fathoms of the surface, and almost 
 everywhere of 40 and less, below 1,000 fathoms; so that 
 from 1,000 fathoms to the greatest depths, the variation is 
 only from 40 to 32 F., or in extreme cases to 28 F. 
 
 The influence of marine currents on the temperature is 
 great. The Gulf stream, a deep Atlantic current, carries heat 
 from the tropical to the polar seas. The portion of the broad 
 current which passes through the Florida Straits is as deep 
 as the Straits, 400 fathoms, and 83 to 44 F. in temperature, 
 and has a maximum velocity of 5 miles an hour. It washes 
 the deep-water border of the Atlantic basin at depths between 
 60 and 300 fathoms off Charleston, and between 60 and 150 
 fathoms (Verrill) southeast of New England ; crosses the 
 ocean northeastward to British seas, has a temperature of 45 
 off the Faroe Islands at a depth of 600 to 800 fathoms ; and 
 thence continues on pole- ward. From the polar regions the 
 waters, chilled down to 39-28 F., flow back, as the " Labra- 
 dor current" along the east coast of America, and also south- 
 ward beneath the warmer current over the ocean's depths 
 to the equator and beyond. Comparatively little goes out 
 through Behrings Straits, because the depth is only 150 feet. 
 
 In the Pacific, there is a warm or tropical current on the 
 west side, answering to the Gulf Stream of the Atlantic. 
 Again, on the east side of the South Pacific, a reverse flow 
 exists : a cold-water current from the southwest strikes the 
 submarine slopes of southern South America, and carries cold 
 to the equator, and thus narrows the region of tropical 
 waters. 
 
 b. Limiting range of Temperature for Species. The range 
 of temperature favorable to any marine species is small 
 generally not over 20 R, and often less than 15 F. Within 
 
DISTRIBUTION OF MARINE LIFE. 73 
 
 the favorable temperature the species thrive ; approaching the 
 limit, the size usually diminishes ; and beyond it, growth and 
 egg-development cease. A current too cold for species within 
 its reach is destructive, even more so than one of too much 
 warmth. The enlarging of the polar current by an increase 
 of high-latitude cold, as in a glacial era, might destroy the 
 sea- bolder life of the oceans nearly to the equator. 
 
 Co Light. Light is the chief limiting cause as to depth 
 (Fuchs). If it were temperature, multitudes of species might 
 grow hundreds of feet below their present level.. Light has 
 been found by experiment to penetrate downward in the 
 ocean 43 to 50 fathoms ; arid what passes this limit is 
 very feeble in amount. The species of depths less than 40 
 fathoms differ to a large extent from the deep-sea species, 
 or those below this limit ; they are (as stated by Fuchs) the 
 species of the light, the latter the species of the darkness. The 
 two ranges of species, the ocean-border (or species of the 
 light) and the deep-sea species (or those of the darkness) are 
 mingled somewhat between depths of 30 and 90 fathoms, and 
 some shore species extend down to a much greater depth. 
 
 The eyes of animals of the deep or dark sea-depths are often 
 blind, or else unusually large. The blindness is evidence of 
 darkness, and the large eyes, of adaptation to the very feeble 
 light of the regions. Env this feeble light may be, as Dr. 
 Carpenter, Wyville Thomson and others have supposed, that 
 of phosphorescence ; lor many Crustaceans, Alcyonia, Star- 
 fishes, and other kinds are brightly phosphorescent. 1 
 
 4. The Border Region, or that of the Animals of the Light. 
 Over the ocean's border region not only is the diversity of 
 temperature between the equator and the poles felt in full 
 
 1 The following are enumerated as the most characteristic types of the 
 dark sea-depths. Of Corals, Oculinidse, Cryptohelia and various solitary 
 species ; the Vitreous Sponges ; Crinoids (Pentacrinus, Rhizocrinus, Hyo- 
 crinus, Bathycrinus) ; of Echinoids, Echinothimse, Pourtalesire, Ananchytidse ; 
 of Asterioids, Brisinga ; Holotlmriae of sub-order Elasmopodia ; and Fishes, 
 ribbon -like in form, of the families Lepidopidse, Trachypteridse, Macruridse 
 and Ophidiidae. 
 
74 DYNAMICAL GEOLOGY. 
 
 force, but also that produced by the encroaching warm and 
 cold currents. Off Eastern North America down to Cape 
 Hatteras, the cold Labrador current cools the waters over 
 the border region between the Gulf Stream, in 65 fathoms, 
 and the shore line ; while south of this cape the Gulf Stream 
 has possession. 
 
 The other causes limiting distribution in the border regions 
 of the ocean are: (1) the condition of the water, whether 
 pure, or on the other hand, impure from sediments and fresh 
 waters received from the land ; (2) the character of the lottom, 
 whether of mud, sand, or rock, and whether firm, or easily 
 stirred and made impure by waves or currents. 
 
 Reef-forming Corals grow only in the sea-border regions of 
 tropical seas, and at shallow depths. They extend from the 
 equator to about latitude 28, where the sea-temperature of 
 the coldest month is not below 68 F. Owing to the warm 
 Gulf Stream, they occur in the Atlantic in 34 north latitude, 
 the Bermudas being of coral formation ; and owing to the cold 
 waters off western South America, they are excluded from 
 that coast south of Guayaquil. In depth the limit is 18 ta 
 20 fathoms. A vast variety of tropical species live and find 
 shelter among coral reefs. 
 
 Sea-weeds, like other plants, are species of the light ; they 
 grow mostly within 10 fathoms of the surface, and rarely 
 beyond 30. 
 
 In the sea-depths, or the region of darkness, the range of 
 temperature is for the most part small 55 to 30. Only 
 two well-marked divisions exist : that of the cold depths, the 
 temperature below 45 F. ; and that within the range of the 
 tropical currents (as the Gulf Stream in the North Atlantic), 
 the temperature mostly 45 to 55 F. 
 
 The border of the oceanic basin where swept by the Gulf 
 Stream (page 72), both on its west side and in the British 
 seas, is crowded with life, species of Crustaceans, Echino- 
 derms, Polyps, Mollusks, Worms, Fishes ; and some kinds 
 are larger than any of the same groups found in shallower 
 
PEAT-FORMATIONS. 75 
 
 waters. Wyville Thomson mentions his bringing up 20,000 
 of one species of sea-urchin at one haul ; and Verrill and 
 Agassiz state parallel facts from the American seas. 
 
 The life from the cold and warmer regions differs to a great 
 extent in species ; and yet the groups represented in the two 
 are largely the same. The colder depths are much less pro- 
 fuse in life, fail of some prominent groups, and contain many 
 of very peculiar characters. 
 
 The cold and warm currents are in places in abrupt con- 
 tact. The pushing of the former, along the eastern ocean- 
 border of North America, over the narrow warmer area by 
 westerly winds was probably the cause of the destruction of 
 Fishes, Crustaceans, etc., of the latter that took place during 
 the winter of 1881-82 (A. E. Verrill). 
 
 The following are further illustrations of the work of life. 
 
 3. PEAT-FOKMATIONS. 
 
 Peat is an accumulation of half-decomposed vegetable mat- 
 ter formed in wet or swampy places. In temperate climates 
 it is due mainly to the growth of mosses of the genus Sphag- 
 num. These mosses form a loose, spongy turf, and, as they 
 have the property of dying at the extremities of the roots 
 while increasing above, they may gradually form a bed of 
 great thickness. The roots and leaves of other plants, or 
 their branches and stumps, and any other vegetation present, 
 may contribute to the accumulating bed. The small Crusta- 
 ceans, Worms, and various other kinds of species living in the 
 waters, including often fresh-water Sponges, add to the ma- 
 terial ; the siliceous spicules of the sponges may generally be 
 found in the ashes of the peat. The carcasses and excrements 
 of large animals at times become included. Dust may also 
 be blown over the marsh by the winds. 
 
 In wet parts of Alpine regions there are various flowering 
 plants which grow in the form of a close turf, and give rise 
 to beds of peat, like the moss. In Fuecjia, although not south 
 
76 DYNAMICAL GEOLOGY. 
 
 of the parallel of 56, there are large marshes of such Alpine 
 plants, the mean temperature being about 40 F. 
 
 The dead and wet vegetable mass slowly undergoes a 
 change, becoming an imperfect coal, of a brownish-black 
 color, loose in texture, and often friable, although commonly 
 penetrated with rootlets. In the change the woody fibre loses 
 a part of its gases ; but, unlike coal, it still contains usually 
 25 to 33 per cent of oxygen. Occasionally it is nearly a true 
 coal. 
 
 Peat-beds cover large surfaces of some countries, and occa- 
 sionally have a thickness of forty feet. One tenth of Ireland 
 is covered by them ; and one of the " mosses " of the Shannon 
 is stated to be fifty miles long and two or three broad. A 
 marsh near the mouth of the Loire is described by Blavier as 
 more than fifty leagues in circumference. Over many parts 
 of New England and other portions of North America there 
 are extensive beds. The amount in Massachusetts alone has 
 been estimated to exceed- 120,000,000 of cords. Many of the 
 marshes were originally ponds or shallow lakes, and gradually 
 became swamps as the water, from some cause, diminished in 
 depth. 
 
 Peat is often underlaid by a bed of whitish shell marl, 
 consisting of fresh- water shells mostly species of Limncea, 
 Pliysa, and Planorbis which were living in the lake. The 
 beds of white chalky material consisting of the siliceous shells 
 of Diatoms, referred to on page 67, are often found beneath 
 peat. 
 
 Peat is used for fuel, and also as a fertilizer. Mack is 
 another name of peat, and is used especially when the ma- 
 terial is employed as a manure ; but it includes also impure 
 varieties not fit for burning, being applied to any black swamp- 
 earth consisting largely of decomposed vegetable matter. 
 
 Peat-beds sometimes contain standing trees and entire 
 skeletons of animals that had sunk in the swamp. The peat- 
 waters have often an antiseptic power, and flesh is sometimes 
 changed by the burial into adipocere. 
 
CORAL-REEFS. 77 
 
 4. CORAL-REEFS. 
 
 In tropical regions corals grow in vast plantations about 
 most oceanic islands and along the shores of continents. In 
 the shallow waters the patches or groves of coral are usually 
 distributed among larger areas of coral sand, like small groves 
 of trees or shrubbery in some sandy plains. 
 
 The corals have much resemblance to vegetation in their 
 forms and their modes of growth ; and the animals are so like 
 flowers in shape and bright colors that they are often called 
 flower-animals (page 184). Along with the corals there are 
 also great numbers of Shells, besides Crabs, Echini, and other 
 kinds of marine life. 
 
 The coral plantations are swept by the waves, and with 
 great force when the seas are driven by storms. The corals 
 are thus frequently broken, and the fragments washed about 
 until they are either worn to sand by the friction of piece 
 upon piece, or become buried in the holes among the growing 
 corals, or are washed up on the beach. Corals are not 
 injured by mere breaking, any more than is vegetation by the 
 clipping of a branch ; and those that are not torn up from 
 the very base and reduced to fragments continue to grow. 
 
 The fragments and sand made by the waves, and by the 
 same means strewed over the bottom, along with the shells 
 also of mollusks, commence the formation of a bed of coral- 
 rock, literally a bed of limestone, for the coral and shells 
 have the composition of limestone, and consolidation goes on 
 simultaneously. As the corals continue growing over this 
 bed, fragments and sand are constantly forming, and the bed 
 of limestone thus increases in thickness. In this manner it 
 goes on increasing until it reaches the level of low tide ; be- 
 yond this it rises but little, because corals cannot grow where 
 they are liable to be left for a day wholly out of water ; and 
 the waves have too great force at this level to allow of their 
 holding their places, if they were able to stand the hot and 
 drying sun. A bed of calcareous rock is thus produced which 
 is a coral reef. 
 
78 
 
 DYNAMICAL GEOLOGY. 
 
 Since reef-corals grow to a depth of only 100 feet (page 
 74), the thickness of the reef cannot much exceed 100 feet 
 if the sea-bottom remains at a constant level, except where 
 there are oceanic currents to transport to greater depths 
 the sand that is made. But should the reef -region be slowly 
 sinking, at a rate not faster than the corals can grow and 
 make the reef rise, then almost any thickness may be attained. 
 From observations about the coral regions of the Pacific, it is 
 supposed that some of the reefs have acquired a thickness of 
 two or three thousand feet or more, during such a slow sub- 
 sidence. 
 
 Fig. 89. 
 
 View of a high island, bordered by coral-reefs. 
 
 The coral formations of the Pacific are sometimes broad 
 reefs around hilly or mountainous islands, as shown in the 
 annexed sketch. To the left, in the sketch, there is an inner 
 reef and an outer reef, separated by a channel of water, the 
 inner of which (/) is called & fringing reef, and the outer (b) 
 
 Fig. 90. 
 
 Coral island, or atoll. 
 
 a barrier reef. They are united in one beneath the water. 
 At intervals there are usually openings through the barrier 
 reef, as at h, h, which are entrances to harbors. The channels 
 are sometimes deep enough for ships to pass from harbor to 
 harbor. 
 
CORAL ISLANDS. 79 
 
 Many coral-reefs stand alone in the ocean, far from any 
 other lands (Fig. 90). These are called coral islands or atolls. 
 
 They usually consist of a narrow reef encircling a salt- 
 water lake. The lake is but a patch of ocean enclosed by the 
 reef with its groves of palms and other 
 tropical plants. When there are deep open- 
 ings through the reef, ships may enter the 
 lake, or lagoon as it is usually called, and r'^ 
 find excellent anchorage. The annexed fig- 
 ure (Fig. 91) is a map of one of the atolls 
 of the Gilbert (or Kingsmill) Islands in the 
 Pacific. The reef on one side the wind- 
 ward is wooded throughout; but on the Apia, of the Gilbert 
 
 group. 
 
 other it has only a few wooded islets, the 
 
 rest being bare and partly washed by the tides. At e there 
 
 is an opening to the lagoon. 
 
 The Paumotu Archipelago, east-northeast of the Society 
 Islands, contains between 70 and 80 coral islands ; the Caro- 
 lines, with the Kadack, Ralick, and Gilbert groups on the 
 east and southeast, as many more ; and others are scattered 
 over the intervening ocean. Most of the high islands be- 
 tween the parallels of 28 north and south of the equator 
 (where the seas are sufficiently warm, page 74) have a fringe 
 of coral-reefs. 
 
 The limestone beds made from corals and shells are not 
 a result of growth alone, as in the case of the deposits formed 
 from microscopic organisms, but of growth in connection with 
 the breaking and wearing action of the ocean's waves and cur- 
 rents. Corals and shells, unaided, could make only an open 
 mass full of large holes, and not a solid rock. There must 
 be sand or fine fragments at hand, such as the waters can and 
 do constantly make in such regions, in order to fill up the 
 spaces or interstices between the corals or shells. If there is 
 clayey or ordinary siliceous sand at hand, this will suffice, 
 but it will not make a pure limestone ; in order to have the 
 rock a true limestone, the shells and corals must be the 
 
80 DYNAMICAL GEOLOGY. 
 
 source of the sand or fine fragments, for these alone yield 
 the needed calcareous material and cement. The limestone 
 made in this way by the help of the waves may be, and often 
 is, as fine-grained as a piece of flint or any ordinary lime- 
 stone, it having been formed, in such a case, of the finest 
 coral sand or mud. In other cases, it contains some imbedded 
 fragments in the solid bed ; in others, it is a coral conglom- 
 erate ; and, over still other large sheltered areas, it is a mass 
 of standing corals with the interstices filled in solid with 
 the sand and fragments. 
 
 Along the shores, above low tide, the sands are aggluti- 
 nated into a beach sand-rock, and the beds have the slope 
 of the beach, or 5 to 15. The waters contain lime (calcium 
 bicarbonate) in solution ; and as the sands, wet at high tide, 
 dry again when the tide is out, the calcareous cement is 
 deposited between the grains, and so consolidation goes for- 
 ward. The cement coats the grains with carbonate of lime ; 
 and either in this way, or by its own concretionary tenden- 
 cies, the rock sometimes becomes an oolyte (page 37). 
 
 The process of limestone-making now going on through 
 the agency of coral animals illustrates equally the method 
 from shells and crinoids. The extent of some of the modern 
 reefs matches nearly that of the largest Paleozoic reefs. On 
 the north of the Feejee Islands the reef-grounds are 5 to 15 
 miles in width. In New Caledonia they extend 150 miles 
 north of the island and 50 miles south, making a total length 
 of 400 miles. Along Northeastern Australia they stretch on. 
 although with many interruptions, for 1,000 miles. 
 
 B. Protective and Destructive Effects. 
 
 a. Protective Effects. Slopes are protected from erosion 
 through a covering of turf; sand-hills, from the winds, 
 through tufts of grass and other vegetation ; shores, from the 
 surf in many places, by a growth of long sea-weeds ; and the 
 
PROTECTIVE AND DESTRUCTIVE EFFECTS. 81 
 
 outer margins of coral-reefs, by a growth over the exposed 
 surface of calcareous vegetation, called JSTullipores. 
 
 Further, forests keep a vast amount of moisture in the wet 
 ground beneath them, which is gradually supplied to the 
 streams as from a reservoir, making them serviceable for 
 mills and other purposes through the year ; whereas, if 
 cut away, the rains fill suddenly the river-channels, pro- 
 ducing disastrous Hoods, and the long droughts which inter- 
 vene are seasons of dwindled and useless waters. And, 
 besides, the floods carry away the soil from the steep hill- 
 sides, and may reduce a productive region to one of rocky 
 ledges. These evils are already a reality in portions of North 
 America, and are on the increase. 
 
 b. Destructive Effects. Itocks, where jointed or fissured 
 or laminated, are torn asunder and often upturned by the 
 growth of seed in a crevice, and the subsequent enlarge- 
 ment of the root and stem, trunks sometimes growing to a 
 diameter of several feet and as gradually opening the crevice, 
 and thus displacing great masses. The same agency opens 
 crevices to moisture, and so promotes decomposition ; and it 
 prepares for the action of freezing in winter (page 115). 
 
 Boring animals cause destruction in various ways. The 
 mole, mouse, and some other animals tunnel embankments, 
 and open a channel for the exit of the confined waters, which 
 rapidly enlarges ; and sometimes a vast amount of erosion is 
 occasioned by the waters thus discharged. The levees of the 
 Mississippi are thus tunnelled by crawfish, occasioning great 
 floods and devastations. Boring shells, as the Saxicavoc 
 weaken the parts of rocks exposed to the surf. 
 
 The decay of vegetable and animal matters in the soil pro- 
 duces organic acids as well as carbonic acid, which erode 
 rocks and promote their decomposition. 
 
 The preying of one kind of life on another has had great 
 effect toward determining the prevalence, or the dwindling 
 and destruction, of species, besides giving occasion for adapta- 
 tions to new conditions. 
 
82 DYNAMICAL GEOLOGY. 
 
 II. CHEMICAL ACTION OF THE AIR AND 
 WATERS. 
 
 Geological work of a destructive kind is carried forward in 
 a quiet way through the chemical action of the constituents 
 of the earth's atmosphere and waters, preparing thus for the 
 rougher mechanical work of these agents ; aud the same pro- 
 cesses have their formative effects. 
 
 1. Oxygen is a constituent both of air and water, it being 
 mixed with nitrogen to form air, and combined with hydro- 
 gen to form water (H 2 0); and many substances in minerals 
 or rocks have an intense affinity for oxygen. 
 
 a. Iron rusts because of its tendency to combine with oxy- 
 gen ; and iron in the protoxide state (FeO) will take more 
 oxygen, and so pass to the sesquioxide state, (Fe 2 Q 3 FeC)*). 
 Consequently, a mineral containing iron in the former state, 
 like pyroxene, hornblende, black mica, and other species, 
 often goes to destruction through this affinity ; and hence 
 rocks containing these minerals (like trap) usually suffer 
 easy decomposition ; for disturbing one constituent is, like 
 taking a stone from an arch, destruction to the whole. The 
 other ingredients of the iron-bearing mineral are set free to 
 make earth, and commonly the associated minerals participate 
 in the decay and add to the earth. The iron in the sesquiox- 
 ide state makes a red earth, and is the species hematite. But 
 it generally combines with water, and becomes a brownish- 
 yellow earth which is yellow ochre, or the mineral called 
 limonite ; it may be pure limoriite, but it is usually mixed 
 with the other materials of the rock, or makes ochreous stains 
 over the surfaces of fissures or joints. 
 
 In this process of oxidation, moisture as well as air must 
 be present ; the oxygen taken up is usually derived from the 
 moisture. 
 
 b. Again, iron when combined with sulphur, constituting a 
 sulphide of iron, like pyrite (FeS 2 ), or pyrrhotite (FeS 8 ), 
 
CHEMICAL CHANGES. 83 
 
 oxidizes readily (unless in the firmest crystals), and passes to 
 the same state of yellow-ochre or limonite (4FeS 2 becoming 
 2Fe a O s +3H 2 O=2Fe a 3H,0 ). The sulphur also oxidizes and 
 becomes sulphuric acid, which is a destructive agent, owiner 
 
 * o O 
 
 to its tendency to take into combination many of the ingre- 
 dients of minerals, as lime, magnesia, soda, potash, alumina, 
 and also iron ; and it hence aids much in the work of destruc- 
 tion. This acid may combine with the iron, and so make 
 green vitriol ; but as its affinity for the substances above enu- 
 merated is stronger than for iron, the iron is usually left in 
 the ochreous state. 
 
 Now sulphide of iron, in the form of pyrite or pyrrhotite, 
 is disseminated more or less abundantly through nearly all 
 the rocks of the globe, occurring in most granite, syenyte, 
 gneiss, mica and other schists, and slates, sandstones, shales, 
 much trap, and many limestones ; and hence, rocks in all 
 lands are undergoing destruction through this agency. Many 
 a fair-looking building-stone is rendered worthless by it. It 
 is the mostjmiversal of rock-destroyers. When the minute 
 grains of pyrite in a granite or sandstone oxidize, the other 
 mineral particles of the rock are set loose and become discol- 
 ored with the ochre that is made ; and the sulphuric acid, at 
 the same time formed, eats into some of those grains to cause 
 their decomposition. Thus the granite either (a) disintegrates 
 into a loose granitic sand, or (b) it becomes decomposed to 
 earth or clay. Blocks of trap have a thin decomposed crust 
 which is incessantly receiving additions inside while losing 
 outside. 
 
 The decomposition of sulphide of iron in shales or clays 
 often forms alum, and makes alum-clays, because of the com- 
 bination of the sulphuric acid with the alumina of the rock, 
 and usually with some other base in the protoxide state, as 
 potash, soda, magnesia etc. 
 
 2. Carbonic Acid (C0 2 ) is present in the atmosphere, about 
 3 parts in 10,000 by volume consisting of this gas. It is 
 present in all rain-water, the rain-water deriving it from the 
 
84 DYNAMICAL GEOLOGY. 
 
 atmosphere. It is present in the soil, being produced where 
 the material of plants and animals is undergoing slow decom- 
 position; and thence it is given to the waters percolating 
 through soils. By all the methods mentioned, and also 
 through animal respiration, the sea derives carbonic acid. 
 Moreover, in the earlier ages of the globe, the amount of 
 carbonic acid in the atmosphere and waters far exceeded the 
 present. 
 
 Carbonic acid tends strongly to form combinations with 
 magnesia, lime, potash, soda, and with iron in the protoxide, 
 state. Hence a feldspar, since it yields potash, soda, or lime, 
 is liable to have its alkali carried off by percolating waters ; 
 and with such a loss, the mineral changes to a hydrous clayey 
 mineral called kaolin, the material used in making porce- 
 lain. Common feldspar yields on analysis 17 per cent of 
 potash, 18.5 of alumina, and 645 of silica; and kaolin, no 
 potash, 14 of water, 40 of alumina, and 46 of silica. Granite 
 and other rocks are often eaten into by this process, so as to 
 be fragile to the depth of a foot or more, and sometimes to a 
 depth of 50 or 100 feet. 
 
 Fig. 92. Fig. 93. 
 
 The depth of decomposition, by either method, is measured 
 by the depth to which moisture is absorbed; so that the 
 architectural value of a stone is inversely as its absorbent 
 quality. All cracks or joints by which water enters may 
 have a discolored border of like depth (Fig. 92); and the 
 process goes on by this means, in some granite, trap, and other 
 rocks, until the mass becomes reduced to what looks like a 
 pile of large spheroidal concretions (Fig. 93); and ends finally 
 in making earth, or loose sand, of the whole. 
 
CHEMICAL CHANGES. 85 
 
 When the iron-carbonate (called siderite) is left exposed to 
 the air and moisture, the iron oxidizes, and changes to limon- 
 ite. So any limestone that contains iron, replacing part of 
 the calcium or magnesium, will readily become brown and 
 crumble. 
 
 The decomposition of iron-bearing minerals is promoted by 
 the action of carbonic acid, or of an organic acid derived from 
 the soil waters. These acids extract the iron protoxide and 
 make with it a soluble salt of iron, and thus, by the aid of 
 streamlets, may carry the iron away. In order that carbonic 
 acid should thus take up iron, and make the soluble bicarbon- 
 ate, it must be under pressure, and the carriers now are the 
 organic acids ; but in ancient time, when the atmosphere 
 was much denser than at present, carbonic acid may have 
 done this work. The salt of iron becomes oxidized in the 
 low places or marshes to which it may be carried, because 
 the waters thus get more of the salt that they can dissolve, 
 and forms there a yellow or brown or brownish-black deposit 
 of limonite or a related ore. 
 
 The organic material of the soils, owing to its using oxygen 
 when decomposing, will take it from any Fe. 2 3 present, and 
 may thus change it to Fe 0, and this Fe O then combine 
 with the organic acid- or carbonic acid at hand. Many red 
 beds of rocks have lost the red color in spots or seams or 
 along cracks, by this method of deoxidation. 
 
 Waters containing carbonic acid readily erode limestone. 
 The limestone is taken up and a calcium bicarbonate is formed, 
 which is soluble. On evaporation, the bicarbonate loses its 
 excess of carbonic acid, and the limestone taken up is again de- 
 posited. Thus limestone strata are eroded, and caverns made ; 
 and through the depositions, the caverns are hung with stalac- 
 tites and floored with stalagmite. (See pages 102, 104). 
 
 Deposits formed; Rocks consolidated. (1) By the processes 
 above-mentioned, from iron-bearing limestone or iron carbon- 
 ate, great beds of limonite, of the purest quality, have been 
 made (some, over 100 feet deep) ; and they often lie in place, 
 
86 DYNAMICAL GEOLOGY. 
 
 that is. occupy the depressions produced by the decomposi- 
 tion. Those of Richmond and West Stockbridge in Massa- 
 chusetts, of Salisbury in Connecticut, of Millerton and other 
 places in eastern New York, and of many localities south of 
 New York in Pennsylvania and Virginia, are of this kind. 
 Again, the iron-salts carried to marshes the pockets of a 
 region have often made large beds of the related bog 
 ore ; but such ore is likely to contain sulphur (from decom- 
 posed pyrite) and phosphorus (from the decomposing organic 
 material present) and hence the iron afforded is of inferior 
 quality. 
 
 (2) From the feldspar decompositions have come large beds 
 of kaolin ; and some of the best and largest have been made 
 from quartzytes containing disseminated feldspar, as in the 
 southern margin of New Marlborough, Mass. 
 
 (3) Carbonated waters, besides forming stalactites, have 
 made large beds of limestone, like the travertine of JTivoli, 
 near Rome, and the so-called alabaster of Mexico. 
 
 Carbonated waters, besides serving in the consolidation of 
 limestones (page 80), often also consolidate sand-beds, gravel- 
 beds, and clay-beds, when grains of limestone are even sparingly 
 present; and very commonly the solidification takes place 
 around centres (some grain, or it may be fossil, serving as 
 the nucleus) and so makes concretions (page 47) in the bed, 
 complete consolidation often, following later. Again, consoli- 
 dation takes place to some extent through depositions of 
 limonite in pebble-beds and sand-beds. But the more com- 
 mon method of solidifying such fragmental deposits is through 
 siliceous waters (page 147). 
 
 III. THE ATMOSPHERE. 
 
 The following are some of the mechanical effects connected 
 with the movements of the atmosphere. 
 
 1. Transportation of sand, dust, etc. The streets of most 
 cities, as well as the roads of the country, in a dry summer 
 
WORK OF THE WINDS. 87 
 
 day, afford examples of the drift of dust by the winds. The 
 dust is borne most abundantly in the direction of the preva- 
 lent winds, and may in the course of time make deep beds. 
 The dust that finds its way through the windows into a neg- 
 lected room indicates what may be done in the progress of 
 centuries where circumstances are more favorable. 
 
 The moving sands of a desert or sea-coast afford the more 
 important examples of this kind of action. 
 
 On sea-shores, where there is a sea-beach, the loose sands 
 composing it are driven inland by the winds into parallel 
 ridges higher than the beach, forming drift-sand hills. They 
 are grouped somewhat irregularly, owing to the course of the 
 wind among them, and also to little inequalities of compact- 
 ness, or to protection from vegetation. They form especially 
 (1) where the sand is almost purely siliceous, and therefore 
 not at all adhesive even when wet, and not good for giving 
 root to grasses ; and (2) on windward coasts. They are com- 
 mon on the windward side, and especially the projecting 
 points, even those of a coral island, but never occur on the 
 leeward side, unless this side is the windward during some 
 portion of the year. The stratification in such drift-hills is 
 of the kind represented in Fig. 22 /, page 45, and shows that 
 the growing hill was often cut partly down or through by 
 storms, and was again and again completed after such dis- 
 asters. On the southern shore of Long Island series of such 
 sand-hills, 10 to 30 feet high, extend along for 100 miles. 
 They are partially anchored by straggling tufts of grass. The 
 coast of New Jersey down to the Chesapeake is similarly 
 fronted by sand-hills. They occur also on the east coast of 
 Lake Michigan. In Norfolk, England, between Hunstanton 
 and Weybourne, the sand-hills are 50 to 60 feet high. 
 
 Dust is carried by storm winds, sometimes hundreds of 
 miles. A shower covered the Cape Verdes with dust from 
 Africa, nearly 1,000 miles distant, and was 1,600 miles broad 
 (Darwin). Volcanic dust was carried, in 1835, from Guate- 
 mala to Jamaica, 800 miles. Birds and insects are thus car 
 
88 DYNAMICAL GEOLOGY. 
 
 ried to sea. In one dust-shower, about Lyons in France, 
 720,000 pounds of dust fell, and, of this, 90,000 consisted of 
 Diatoms and other organic relics (Ehrenberg). 
 
 2. Additions to land by means of drift-sands. The drift- 
 sand hills are a means of recovering lands from the sea. The 
 appearance of a bank at the water's surface off an estuary at 
 the mouth of a stream is followed by the formation of a beach, 
 and then the raising of hills of sand by the winds, which 
 enlarge till they sometimes close up the estuary, exclude the 
 tides, and thus aid in the recovery of the land by the deposi- 
 tions of river-detritus. Lyell observes that at Yarmouth, 
 England, thousands of acres of cultivated land have thus 
 been gained from a former estuary. In all such results the 
 action of the waves in first forming the beach is a very impor- 
 tant part of the whole. 
 
 3. Destructive effects of drift-sands. Dunes. Dunes are 
 regions of loose drift-sand. In Norfolk, England, between 
 Hunstanton and Weybourne, the drift-sands have travelled 
 inland with great destructive effects, burying farms and 
 houses. They reach, however, but a few miles from the 
 coast-line, and were it not that the sea-shore itself is being 
 undermined by the waves, and is thus moving landward, the 
 effects would soon reach their limit. East of Lake Michigan 
 the sand-hills have a height of 100 to 200 feet; and even 
 215 feet at Grand Haven, where, according to A. Winchell, 
 the forest has been buried so as to leave only the " withered 
 tree-tops projecting a few feet above the waste of sands." 
 In the desert latitudes, drift-sands are more extended in their 
 effects. 
 
 4. Abrasion ; Sand-scratches. The sands carried by the 
 winds, when passing over rocks, sometimes wear them smooth, 
 or cover the surface with scratches and furrows, as observed 
 by W. P. Blake on granite rocks at the Pass of San Bernar- 
 dino in California. Ledges and bluffs have been deeply 
 eroded and shaped or worn away by this agency. Similar 
 effects have been observed by Winchell in the Grand Traverse 
 
WORK OF THE WINDS. 89 
 
 region, Michigan. Glass in the windows of houses on Cape 
 Cod sometimes has holes worn through it by the same means. 
 The hint from nature has led to the use of sand, driven by 
 a blast with or without steam, for cutting and engraving 
 glass, and even for cutting and carving granite and other 
 hard rocks. 
 
 5. Winds as transporters of Moisture. The atmosphere takes 
 moisture from the ocean and land, proportionally to its tem- 
 perature, and transports it. If the air increases in tem- 
 perature as it passes over a continent, it keeps taking up 
 moisture, and so dries up the land ; if, on the contrary, it 
 loses in temperature, its capacity for moisture is lessened, 
 and it drops it, making rain and mists over the land. If the 
 warm wind strikes the cold side or summit of a mountain, 
 the moisture is largely dropped, so that little remains for the 
 region on the opposite side of the mountain, which therefore 
 experiences drought. 
 
 The trade winds are movements of the air within the 
 tropics westward, against the east side of the continents; 
 they are warm winds, well charged with moisture. Near 
 and over the continents they bend away from the equator 
 and thus pass to colder regions ; hence they are moist winds, 
 giving abundant rains. Consequently the eastern portions of 
 continents are regions of much rain ; and the farther back 
 from the east coast the higher mountains are set the larger 
 the surface benefited by the rains. The great Gulf of Mexico 
 is of immense service to North America as a source of water- 
 supply to the winds ; and so also is the position of the high 
 Rocky Mountains, so far away from the eastern coast. 
 
 The winds over the ocean, north of the parallel of 30 to 
 60, are movements of air eastward, and therefore against the 
 west side of the continents ; they are not warm winds, and 
 not abundant in moisture. Near and over the continents 
 they bend equator-ward and pass generally over warmer 
 regions ; hence they are drying winds ; and consequently the 
 western portions of continents are regions of less rain than 
 
90 DYNAMICAL GEOLOGY. 
 
 the eastern ; and on the western portions, between latitudes 
 25 and 35 exist the chief desert regions of the continental 
 borders. 
 
 Thus the winds are largely the distributers of fertility, the 
 locators of great forest regions and deserts, and the limiters of 
 distribution for the living species of the land ; and they have 
 done their work in the same way essentially through all past 
 time, and in general with like geographical effects over the 
 same regions from one age to another. America has always 
 been, as Guyot has styled it, the forest continent. 
 
 IV. WATER. 
 
 The following subdivisions are here adopted : 
 
 1. FRESH WATERS ; or those of Eivers and Lakes. 
 
 2. The OCEAN ; and, with it, the larger Lakes. 
 
 3. FROZEN WATERS, or Glaciers and Icebergs. 
 
 1. Fresh Waters. 
 
 A. Superficial Waters, or Rivers. 
 
 The working force or energy of moving waters depends on 
 gravity, and is determined, in any case, by (1) the volume of 
 water and (2) the amount of its fall. This energy may be 
 used up (1) in overcoming the friction due directly to the 
 motion, in which erosion of the bed may be produced; 
 (2) in transporting earth or stones, the source of most frag- 
 mental deposits; and (3) in overcoming the friction arising 
 from the abrasion of the particles of the transported material 
 against the bed and among themselves, another source of 
 erosion. 
 
 I. Erosion. 
 
 1. Sources of streams; Drainage-areas. The waters of riv- 
 ers descend in the form of rain and snow from the clouds, 
 and are derived by evaporation_both from the surface of the 
 
RIVERS. 91 
 
 land, with its lakes, rivers, and foliage, and from the ocean, 
 but mostly from the latter. The waters rise into the upper 
 regions of the atmosphere, and, becoming condensed into 
 drops or snow-Hakes, fall over the hills and plains. They 
 gather first into rills ; these, as they descend, unite into 
 rivulets ; these, again, if the region is elevated or mountain- 
 ous, into torrents ; torrents, flowing down the different moun- 
 tain valleys, combine with other torrents to form rivers ; and 
 rivers from one mountain-chain sometimes join the rivers 
 from another and make a common stream of great magnitude, 
 and great drainage-area, like the Mississippi or the Amazon. 
 
 The Mississippi has its tributaries among all the eastern 
 heights of the great Kocky Mountain chain, throughout a 
 distance of 1,000 miles, or between the parallels of 35 N. 
 and 50 N. ; and still another set of tributaries gather waters 
 from the Appalachian chain, between Western New York and 
 Alabama, Kills, rivulets, torrents, and rivers combine over 
 an area of millions of square miles to make the great central 
 trunk of the North American continent. 
 
 The amount of water poured each year into the ocean by 
 the Mississippi averages 19J trillions (19,500,000,000,000) 
 of cubic feet, varying from 11 trillions in dry years to 27 tril- 
 lions in wet years. This amount is about 25 per cent of that 
 furnished by the rains, the rest being lost mostly by direct 
 evaporation, but also in part by absorption into the soil and 
 strata and by contributing to the growth of vegetation. 
 
 Snowy mountains deal out water gradually under the 
 control of the sun and winds, day and night and summer and 
 winter making alternations in the supply to the streams. 
 Forest regions also are like reservoirs in holding on long, and 
 supplying gradually, the waters beneath them. 
 
 2. Erosion. Valley-making. Erosion or wear (termed also 
 denudation) and transportation are consequences of motion. 
 The rain-drop makes an impression where it falls (Fig. 27, 
 page 47) ; the rill and rivulet carry off light sand and deepen 
 their beds, as may be seen on any sand-bank or by many a 
 
92 DYNAMICAL GEOLOGY. 
 
 roadside ; torrents work with greater power, tearing up rocks 
 and trees as they plunge along, and, in the course of time, 
 make deep gorges or valleys in the mountain-slopes ; and 
 rivers, especially in periods of flood, hurry on with vast 
 power, making wider valleys over the breadth of a continent. 
 The slopes of a lofty mountain, exposed through ages to the 
 action described, finally become reduced to a series of valleys 
 and ridges, and the summit often to towering peaks and 
 crested heights, all these effects originating in the fall of 
 rain-drops or snow-flakes. 
 
 Flood-time is the period of active work. Before, streams are 
 often almost still from (1) want of slope, or (2) the friction be- 
 tween the large bed and the little water ; but at flood-height 
 the waters at their high level have (1) augmented slope, and, 
 (2) relatively to the amount of water, largely diminished 
 friction ; and hence comes the greater velocity. The Connect- 
 icut, to Hartford, 36 miles (in an air line), is a tidal stream, 
 zero in working force at low water and tide ; but in its 
 highest flood (30 feet at Hartford) it has a mean pitch to the 
 Sound of 10 inches a mile, and flows off with great rapidity. 
 On mountain streams the transition is often from almost or 
 quite zero to a succession of cataracts of vast working force. 
 
 Nearly all the deep valleys of the world owe their excava- 
 tion to running water. Their positions have sometimes been 
 determined by fissures in the earth's strata, or by the courses 
 of the lowlands left between mountain chains ; but, generally, 
 rivers have worked out their own channels from their begin- 
 nings onward to their present depth and extent. 
 
 With steep slope, as in many mountain regions, the stream 
 excavates rapidly, and carries off what it gathers instead of 
 depositing it, the powers of erosion and transportation being 
 great ; consequently the valley it makes is more or less 
 V-shaped. But, where the slope is gentle and the velocity 
 small, the erosion at bottom becomes feeble or null ; in times 
 of flood the waters spread over the banks and tend to widen 
 the valley as they rush along by its sides; at the same 
 
EROSION BY RIVERS. 93 
 
 time, with declining floods and slackening velocity, deposi- 
 tions take place of the transported material, owing to fric- 
 tion, making an alluvial flat, or flood-plain, where the 
 retardation is greatest on one or both sides, and so the 
 valley becomes U-shaped. Eivers, hence, have ordinarily a 
 narrow channel for the dry season, and a wide flood-plain 
 which is its bottom in time of flood. 
 
 3. Methods of Erosion. Erosion is carried forward mainly 
 by the following methods : 
 
 a. By the friction or strokes of the flowing waters. In a 
 rapid stream, especially when increased in depth and speed by 
 floods, the waters often throw themselves in large volumes into 
 cavities or recesses among the rocks, and thus tear away ob- 
 stacles, overcome cohesion in the softer deposits within reach, 
 wrench out masses of rock where the beds are laminated or 
 jointed (and nearly all rocks are jointed), and by this means, 
 and by undermining, make rapid destruction of exposed ledges 
 and piles of strata, and so carry on the excavation of tlis 
 channel. Where the pitch is large, the waters accumulate 
 working-force by the descent, augmenting the effects. Over 
 smoothly rounded or even surfaces, the effect is very feeble. 
 
 b. Bi/ the abrading action of transported earth and stones. 
 The earth and stones carried along by a stream abrade the 
 bottom and sides of the channel, and so carry forward the 
 work of excavation. There is mutual abrasion of the earth 
 and stones, resulting in increasing their fineness and their 
 transportability. A stream seldom does so much transport- 
 ing work as to lose all abrading power, and never when a 
 large and rapid torrent. 
 
 c. Aid from decomposition and solution. The decompos- 
 ing and dissolving action of the water takes an important part 
 in the work of denudation. Decomposition and disintegra- 
 tion (pp. 82-35) are going on over almost all exposed surfaces 
 of rocks, thus making softened material for the abrading and 
 transporting rills and rivers. Solution also has large effects, 
 especially in limestone regions ; it helps greatly in the exca- 
 
94 DYNAMICAL GEOLOGY. 
 
 vation of valleys, and finds in the joints of the rocks a chance 
 to begin the work (page 84). 
 
 The rounded stones, gravel, and earth of fields, and also the 
 material of most geological formations, has been made out of 
 pre-existing solid rocks, to a large degree by the wearing action 
 of waters, either those of streams over the land, or those of 
 the ocean. But this action is, and ever has been, greatly aided 
 by the processes of decomposition or disaggregation due to 
 the elements. This last-mentioned cause is sufficient alone to 
 turn angular blocks of most rocks into rounded masses. 
 
 The finer transported material is called detritus (from 
 the Latin for worn out} and also silt. The larger rounded 
 stones are termed bowlders. 
 
 4. Cascades, A cascade usually occurs on a rapid stream, 
 where in the course of it there is a hard bed of rock over- 
 lying a soft one. The hard bed resists wear, while the soft 
 one below yields easily : thus a plunge begins, which in- 
 creases in force as it increases in extent. At Niagara Falls, 
 80 feet of shale under-lie 80 feet of hard limestone (Fig. 14, 
 p. 40). Kills and rivulets made by a shower of rain along 
 road -sides or sand-banks often illustrate also this feature of 
 great mountain-streams. 
 
 5. Features produced where Strata are nearly Horizontal. 
 Mountains of Circumdenudation. When the rocks underlying 
 a region are nearly horizontal, the valleys cut by the rivers 
 have usually bold rocky sides. In many parts of the Eocky 
 Mountains the streams have worked their way down through 
 the rocks for hundreds, and in some places even thousands, of 
 feet. Such a place is often called a canon. 
 
 These canons are of wonderful depth and magnitude on the 
 Colorado Eiver, over the west slope of the Eocky Mountains, 
 between longitude 111 W. and 115 W. For 300 miles there 
 is a nearly continuous canon, 3,500 to 6,000 feet deep. The 
 following sketch, from one of the excellent photographs of the 
 region by the artist of Powell's Expedition, represents a por- 
 tion of it, called the Marble Canon. The rocks stand in 
 
CANONS; MOUNTAIN-SCULPTURE. 95 
 
 nearly vertical precipices either side of the stream, and the 
 height above the water to the top of the bluff' seen in the 
 distance is 5,000 feet. The deep gorge is the result of erosion 
 by the stream, which is still continuing its wearing action. 
 
 Fig. 94. 
 
 Cailon of the Colorado. 
 
 In large parts of the canon are crowds of peaks and 
 temple-shaped summits, some of them 5,000 feet high, all of 
 which are the work of the waters since the era of the early 
 Tertiary. Moreover, above the walls of the canon, over the 
 country to the northward, rise plateaus and mountains, in 
 which the strata are piled up to an additional altitude of 
 5,000 to 7,000 feet, which are portions of great formations 
 that once spread over the whole region. The mountain ridges 
 and peaks of Colorado, Uta.h, and the adjoining territories,, 
 
96 DYNAMICAL GEOLOGY. 
 
 12,000 to 14,000 feet in. height, are other fragments of the 
 same strata, and often show nearly horizontal beds to their 
 tops. 
 
 When mountain forms have thus been made they are some- 
 times called 'mountains of circumdenudation. Given a great 
 elevated plateau in a region of rains, and mountain-sculpturing 
 will go on about it, and may continue until all is ridge and 
 valley, not a square mile of the original plateau retaining its 
 flat surface ; and the resulting crested ridges may rise thou- 
 sands of feet above the bottoms of the valleys, if the plateau 
 is one of sufficient height. The Catskill Mountains, New 
 York, are an example of a mountain of circumdenudation ; 
 and most of the mountains of Utah and Colorado are other 
 examples. The wear is much the most rapid when there is 
 little vegetation over the surface. 
 
 The following figures, by Lesley, illustrate some of the 
 results of the sculpturing by water, in both horizontal and 
 upturned or flexed strata. In the production of such eleva- 
 tions, the ocean has sometimes taken part during the sub- 
 mergence of a continent ; but the final results are, in almost 
 all cases, due to the chisellings of fresh waters. The figures 
 here given are small, but the elevations they represent, as 
 illustrated in the Appalachians, Juras, and many other moun- 
 tain regions, are often thousands of feet in height. 
 
 When the beds are horizontal, or nearly so, but of unequal 
 hardness, the softer strata are easily worn away, and by this 
 means the harder strata become undermined. Table-lands 
 
 Fig. 95. Fig. 96. 
 
 are often thus formed, having a top of the harder rock, and 
 the declivities usually banded with projecting shelves and 
 intervening slopes. Figs. 95, 96 represent the common 
 character of such hills. Such flat-topped elevations in the 
 
or THE X 
 V;4VKG{TY } 
 k WATER. 
 
 97 
 
 Colorado region have been called mesas, from the Spanish 
 for table. 
 
 When the beds are inclined between 5 and 30, and are 
 alike in hardness, there is a tendency to make hills with a 
 long back slope and bold front ; but with a much larger dip, 
 the rocks, if hard, often outcrop in naked ledges. 
 
 When the dipping strata are of unequal hardness, and lie 
 in folds, there is a wide diversity in the results on the fea- 
 tures of the landscape. 
 
 Figs. 97, 98 represent the effects from the erosion of a 
 synclinal region consisting of alternations of hard and soft 
 
 Figs. 97-102. 
 
 strata. The protection of the softer beds by the harder is 
 well shown. This is still further exhibited in Figs. 99-102. 
 
 Anticlinal strata give rise to another series of forms, in 
 part the reverse of the preceding, and equally varied. Figs. 
 103-106 represent some of the simpler cases. When the 
 back of an anticlinal mountain is divided (as in Figs. 103 
 105), the mountain loses the anticlinal feature, and the 
 
 Figs. 103-106. 
 
 parts are simply monoclinal ridges. Tn Fig. 106 the anti- 
 clinal character is distinct in the central portion, while lost in 
 the parts on either side. In Fig. 106, to the right, a common 
 effect is shown of the protection afforded to softer layers by 
 
 7 . 
 
98 DYNAMICAL GEOLOGY. 
 
 even a vertical layer of hard rock: the vertical layer forms 
 the axis of a low ridge. 
 
 2. Transportation by Rivers, and distribution of trans- 
 ported Material. 
 
 1, Fact of transportation. It has been stated that the 
 massive mountains have been eroded into ridges and valleys 
 by running w.ater. The material worn out has been trans- 
 ported somewhere by the same waters. 
 
 Part of the transported material in all such operations 
 goes to form the great alluvial plains that occupy the river- 
 valleys throughout their course. Part is carried on to the sea 
 into which the river empties, where it meets the counteracting 
 waves and currents and is distributed for the most part along 
 the shores, filling estuaries or bays, or making deltas, and ex- 
 tending the bounds of the land. 
 
 Thus the mountains of a continent are ever on the move 
 seaward, and contribute to the enlargement of the sea-shore 
 plains. The continent is losing annually in mean height, but 
 gaining in width, or extent of dry land. 
 
 2, Transporting power of water. The transporting power 
 of running water is very great when the flow is rapid. 
 Large stones and masses of rocks are torn up and moved 
 onward by the mountain- torrent. It has been calculated, 
 after some trials, that a current of four miles an hour will 
 carry stones 2-J- inches in diameter ; of two miles, pebbles of 
 0.6 inch ; of two thirds of a mile, fine sand, about .064 in 
 diameter ; of one third of a mile, fine earth or clay, the 
 particles .016 in diameter; the mean diameter of the largest 
 transportable particles varying as the square of the velocity, 
 supposing them of like density. 
 
 Hence, as a stream loses in velocity it leaves behind the 
 coarser material, and carries only the finer ; if the rate be- 
 comes very slow, it drops the gravel or the sand, and bears 
 on only the finest earth or clay. Consequently, where the 
 
WATER. 99 
 
 current is swift, the bottom (and the shore also, wherever the 
 current strikes it) is stony or pebbly ; and where the water 
 is still, or nearly so, the bottom and shores are muddy. 
 
 3. Amount of material transported. The amount of trans- 
 ported material varies with the size and current of the rivers 
 and the kind of country they flow through. The Mississippi 
 carries annually to the Gulf of Mexico, according to Hum- 
 phreys and Abbot, on an average, 812,500,000,000 pounds of 
 silt, equal to a mass one square mile in area and 241 feet 
 deep, and its bottom waters push on enough more to make 
 the 241 feet 268 feet. The process slowly lowers the drain- 
 age area of the river, and the mean amount of lowering 
 indicated by the facts stated is one foot in 4,920 years. 
 The total annual discharge of silt by the GangeJTtfas r been 
 estimated at 6,368,000,000 cubic feet. 
 
 Besides the silt, rivers carry what the waters _ta_ke_ into 
 solution. The amount is generally between a third and a half 
 of that mechanically" 'transported ; but sometimes nearly an" 
 e^uaJjgeignt. If one Tialf, in the case of the Mississippi, 
 the interval 4,920 years becomes 3,280. The salts held in 
 solution are often about one half calcium carbonate, and the 
 rest calcium sulphate, sodium chloride (common salt), and 
 magnesian and potash salts, with traces of silica and other 
 ingredients. The contributions of these salts from rivers 
 to the ocean must be making a slow increase of its saltness. 
 In some cases the rivers carry the salts to inland seas or 
 plains, which have no drainage toward the ocean, and which 
 therefore are saline. Besides, arid plains become saline 
 because of the capillary action which brings moisture from 
 below to the surface, as evaporation goes on above depositing 
 the contained saline ingredients, such as the sodium chloride, 
 sodium carbonate, and magnesian salts of such places. 
 
 4. Alluvial or Fluvial formations. The deposits made by 
 the transported material which now constitute the alluvial 
 plains of the river-valleys cover a large part of a continent, 
 since rivers or smaller streams are almost everywhere at 
 
100 DYNAMICAL GEOLOGY. 
 
 work. They are made up of layers of pebbles or gravel, and 
 of earth, silt, or clay, especially of these finer materials. 
 Logs, leaves, shells, and bones occur in them : but these are 
 rare ; for whatever floats down stream is widely scattered by 
 the waters, and to a great extent destroyed by wear and decay. 
 The level of the alluvial plain is ordinarily that of the level 
 of the higher floods, and hence the name of 'flood-plain often 
 applied to it. The spreading waters, by here losing their 
 velocity, owing to friction, built up the deposits. The river 
 margin is often a little above flood-level. 
 
 5. Terraces. Eiver- valley or fluvial formations are often 
 in terraces. The terraces are in general a consequence of 
 floods far higher than ordinary floods (like those after the 
 Glacial era, page 355), their plains being true flood-plains. 
 But some terraces have been formed by the abrasion of 
 higher terraces. Others, on bays, are alluvial flats left high, 
 after a change of level ; and sea-shore flats and beaches, and 
 horizontal lines of wave-erosion on cliffs, have often been 
 left high in the same movements. 
 
 6. Estuary and Delta formations. The detritus-material 
 discharged by the river at its mouth tends to fill up the 
 bay into which it empties, and make wide flats on its 
 borders, and thus contract it to the breadth merely of the 
 river-current. 
 
 Where the tides are feeble and the river large, the deposits 
 about the mouth of the stream gradually encroach on the 
 ocean, and make great plains and marshy flats, which are 
 intersected by the many mouths of the river and a network 
 of cross-channels. Such a formation is called a delta. Fig. 
 107 represents the delta of the Mississippi, the white lines 
 being the water-channels and the black the great alluvial 
 plains. The delta properly commences below the mouth of 
 Eed Eiver, where the Atchafalaya lay on, or side-channel of 
 the river, begins. The whole area is about 12,300 square 
 miles ; about one third is a sea marsh, only two thirds lying 
 above the level of the Gulf. 
 
WATER. 
 
 101 
 
 The deltas of the Nile, Ganges, and Amazon are similar in 
 general features to the delta of the Mississippi. 
 
 The detritus poured into the ocean where the tides or cur- 
 rents are strong, and a considerable part of that where the 
 
 tides are feeble, goes to form sea-shore flats and sand-banks 
 and off-shore deposits. In their formation the ocean takes 
 part through its waves and currents, and hence they are 
 
102 DYNAMICAL GEOLOGY. 
 
 more conveniently described in connection with the remarks 
 on oceanic action. 
 
 B. Subterranean Waters. 
 
 1. Origin and course of subterranean waters. A part of the 
 waters that fall on the earth's surface on its mountains 
 as well as its plains sinks through the ground and into 
 the rocks beneath, wherever there are openings or crevices, 
 or looseness of texture, and thus becomes subterranean. 
 The waters usually pass easily through sandstones ; but 
 over a clayey or other compact stratum they accumulate, 
 and often make wet springy soil above ; or if the stratum 
 is inclined, they may descend to great depths, or come 
 to the light again wherever it outcrops at a lower level. 
 The descending waters sometimes gather into subterranean 
 streams, which have powers of abrasion. Over large areas 
 in some limestone regions, and many volcanic, surface streams 
 are wanting, because of the cavernous recesses ; the waters 
 carry on an underground system of drainage. Thus come 
 springs, subterranean streams large and small, and copious 
 out-flows beneath the sea-level along coasts. 
 
 A region of horizontal limestone abounds in sink-holes, as 
 well as caverns ; and sometimes rivers plunge down the 
 openings into the recesses below, and are lost, or emerge 
 again in fuller flow a mile or more away. 
 
 Ordinary waters easily erode limestone, because they con- 
 tain carbonic acid (page 83). Through the joints or fissures 
 the waters find a way downward, and the erosion they pro- 
 duce makes and widens the joints, forming often funnel- 
 shaped sink-holes. At the bottom of the sink-hole the 
 waters work laterally, eroding channels and chambers, in 
 long series and varying directions ; and if, later, they suc- 
 ceed in penetrating to a still lower level, another tier of 
 chambers is begun. Undermining also goes on, causing falls 
 of rock, and sometimes large enough to make feeble earth- 
 
WATER. 
 
 103 
 
 quakes; and thus the chambers become high and large. 
 Occasionally the roof for an interval caves in, and the cavern, 
 
 Fig. 108. 
 
 MAMMOTH CAVE. 
 
 with the river enclosed, becomes open to the light, and is 
 then an example of one method of making limestone gorges. 
 
104 DYNAMICAL GEOLOGY. 
 
 The preceding map (reduced from H. C. Hovey's interesting 
 work on American Caverns) represents the passages and 
 chambers of Mammoth Cave, Kentucky. This cave occu- 
 pies, with its windings, an area of several square miles in 
 the Carboniferous limestone. The length of the caverns in 
 this limestone in Kentucky (a rock 200 to 1000 feet thick) is 
 estimated by Prof. Shaler at 100,000 miles. Luray Cavern, 
 in Luray Valley, Virginia, is comparatively small, -but, as 
 described by Mr. Hovey, it is one of the most remarkable in 
 the world, for the beauty of its stalactitic hangings and the 
 grandeur of its subterranean chambers. 
 
 In many caverns, bones of the animals that have inhabited 
 them, including sometimes those of Man with his imple- 
 ments of stone or shell or other material, are found buried 
 beneath or within the stalagmite that covers the floor the 
 perpetual dripping keeping up its constant deposition (pages 
 37 and 85.) 
 
 Caves exist in the elevated coral reefs of the Pacific, which 
 are certainly of comparatively recent origin. One, on the 
 island of Atiu, near Tahiti, has " interminable windings " and 
 many chambers, "with fretwork ceilings of stalactite and 
 stalagmite " ( J. Williams). There are others on Oahu, which 
 give a passage to island streams. 
 
 The erosion is helped forward (1) by the oxidation of 
 pyrite (page 82) where it is present, the resulting sul- 
 phuric acid turning limestone into gypsum ; and also (2) by 
 the formation of nitric acid from the nitrogen of the air, 
 which erodes the limestone, making calcium nitrate. The 
 caves of Kentucky and Indiana have afforded a large amount 
 of this nitrate for the making of nitre. 
 
 Subterranean waters often become miner cd waters. They 
 are made calcareous by limestones along their course ; saline, 
 from the saline ingredients of rocks ; sulphureous, by decom- 
 posing iron sulphides ; carbonated, by any acid, as sulphuric, 
 attacking a limestone and setting carbonic acid free ; chaly- 
 beate, if iron is present in the last process ; and magnesian, or 
 
ARTESIAN WELLS. 
 
 105 
 
 of other quality, in connection with the last, when the decom- 
 position of any rock is going forward that can afford the 
 materials, and when the ocean is a source. They may be- 
 come warm waters through the decomposition of pyrite, etc., 
 or through subterranean heat, and may receive vapors and 
 various mineral materials from the depths below. 
 
 2. Artesian Wells. When strata are inclined, and water 
 descends along one of the layers between others that are 
 sufficiently close to confine it, the pressure increases with the 
 descent ; so that the water will rise through a boring made 
 down to it, and sometimes F . 1Qg 
 
 in a high jet. The principle ..f r ~~ ** a 
 
 is illustrated in Fig. 109, I 
 in which a b is the water- 
 bearing stratum, I c the 
 boring, and e b the amount 
 of descent. The height of 
 the jet falls much short of 
 I c, on account chiefly of the 
 underground friction. 
 
 Such wells are called Artesian wdls or borings, from the 
 district of Artois in France, where they were early made. 
 'The Artesian well of Grenelle in Paris is 1,798 feet deep, and 
 when first made the water dartsd out to a height of 112 feet. 
 One at St. Louis has a depth of 3,843-J- feet, but without get- 
 ting water, because the region for many miles around is one 
 of horizontal rocks. Such wells are made for agricultural 
 and manufacturing purposes in many dry regions, and they 
 have proved successful even in Sahara. 
 
 3. Land-Slides. Land-Slides are of different kinds : 
 
 1. The sliding of the surface earth, or gravel, of a hill down 
 to the plain below. This effect may be caused by the waters 
 of a severe storm wetting the material deeply and giving it 
 greatly increased weight, besides loosening its attachment to 
 the more solid mass below. 
 
 2. The sliding down a declivity to the plain below of the 
 
 Section illustrating the origin of Artesian wells. 
 
106 DYNAMICAL GEOLOGY. 
 
 upper layer of a rock-formation. This may happen when this 
 upper layer rests on a clayey or sandy layer and the latter 
 becomes very wet and greatly softened by the waters ; the 
 upper layer slides down on the softened bed. 
 
 3. The settling of the ground over a large area. This may 
 take place when a layer of clay or loose sand becomes wet 
 and softened by percolating waters, and then is pressed out 
 laterally by the weight of the superincumbent layers. But 
 such a result is not possible unless there is a chance for the 
 wet layer to move or escape laterally. Sometimes part of a 
 wet clayey layer, pressed to one side in this way, is left very 
 much folded, while the associated sandy layers have their 
 usual regular bedding. 
 
 2. The Ocean. 
 
 The ocean is vast in extent and vast in the power which 
 it may exert. But its mechanical work in Geology is mostly 
 confined to its coasts and to soundings, where alone material 
 exists in quantity within reach of the waves or currents. In 
 ancient time, when the continents had not their present 
 mountains, and were to a great extent submerged at shallow 
 depths, this work was performed simultaneously over a large 
 part of their surface, and strata nearly of continental area 
 were sometimes formed. In the present age, oceanic action 
 is almost wholly confined to the borders of the continents. 
 
 The saltness of the ocean gives it a density of 1.0245 to 
 
 1.0278, that of pure fresh water being 1. It is slightly 
 
 I the greatest in the tropics, because of the evaporation. A 
 
 cubic foot weighs about 64 pounds. There are three cou- 
 
 1 sequences of the saltness: (1) greater transporting power 
 
 I than fresh water, on account of its density ; (2) much quicker 
 
 \ deposition of sediment, the time required in salt water being 
 
 \a fifteenth of that in fresh, on account of the less adhesion of 
 
 ithe particles ; (3) a supply of common salt and magnesian 
 
 baits, etc., for making deposits of salts, and for use in chem- 
 
WORK OF THE OCEAN. 107 
 
 ical changes attending the making of rocks and minerals, it 
 being the largest of mineral springs (p. 28). 
 
 The mechanical effects of the ocean are produced by its 
 waves and currents. 
 
 I. Erosion and Transportation. 
 
 1. Waves, 7. General action. The force in oceanic waves 
 is a constant force. Night and day, year in and year out, 
 with hardly an intermission, they break against the beaches 
 and rocks of the coast ; sometimes gently, sometimes in heavy, 
 plunges that have the force of a Niagara of almost unlimited 
 breadth. The gentlest movements have some grinding action 
 among the sands, while the heaviest may dislodge and move 
 along, up the shores, rocks many tons in weight. Niagara 
 wastes its power by falling into an abyss of waters : while 
 in the case of the waves the rocks are bared anew for each 
 successive plunge. The waters are often loaded with gravel 
 and sand when they strike, and thus carry on abrasion. 
 Cliffs are undermined, rocks are worn to pebbles and sand, 
 and, through mutual friction, sand is ground to the finest 
 powder. Eocky headlands on windward coasts are especially 
 exposed to wear, since they are open to the battering force 
 from different directions. 
 
 2. Level of greatest eroding action. The eroding action is 
 greatest for a short distance above the height of half- tide, 
 and, except in violent storms, 
 
 it is almost null below low- 
 tide level. Fig. 110 represents 
 in profile a cliff, having its lower 
 layers,near the level of low tide, 
 extending out as a platform a 11 
 hundred yards wide. As the cuff, New south wales, 
 
 tide commences to move in, the 
 
 waters, while still quiet, swell over and cover this platform, 
 and so give it their protection ; and the force of wave-action, 
 
108 DYNAMICAL GEOLOGY. 
 
 which is greatest above half-tide, is mainly expended near 
 the base of the cliff, just above the level of the platform. 
 But for much battering effect a coast should be shelving, so 
 as to raise the waters as they advance. If deep alongside of 
 a cliff, there is simply a rise and fall, with little abrasion. 
 
 3. Action landward. Waves on shallow soundings have 
 some transporting power ; and, as they always move toward 
 the land, their action is landward. They thus beat back, 
 little by little, any detritus in the waters, preventing that loss 
 to continents or islands which would take place if it were cai - 
 ried out to sea. 
 
 4. Effect on the outline of coasis ; No excavation of narrow 
 valleys. As the action of waves on a coast tends to wear 
 away headlands, and at the same time to fill up bays with 
 detritus, it usually results in making the outline more regular 
 or even. There is nowhere a tendency to excavate narrow 
 valleys into a coast, like those occupied by rivers. Such 
 valleys are made by the waters of the land ; for the ocean 
 can work at valley-making only when it has already an open 
 channel for the waters to pass through, and then the valleys 
 are of very great width. If a continent were sinking slowly 
 in the ocean, or rising slowly from it, wave-action would still 
 be attended by the same results ; for each part of the surface 
 would be 'successively a coast-line, and over each there would 
 be the same wearing away of headlands and filling of bays, 
 instead of the excavation of valleys. 
 
 2. Tidal currents. Tidal currents often have great strength 
 when the tide moves through channels or among islands, and 
 then they are a means of erosion and transportation daily in 
 action, wherever there is rock, mud, or sand within their 
 reach. 
 
 The out-flowing current from bays, or that connected with 
 the ebbing tide, is deeper in its action, and has, therefore, 
 more excavating and more transporting power than the in- 
 flowing, or that of the incoming tide. The latter moves on 
 as a great swelling wave, and fills the bays much above their 
 
WORK OF THE OCEAN. 109 
 
 natural level ; but the out-flowing current begins along the 
 bottom before the tide is wholly in, owing to the accumula- 
 tion of waters, and when the tide changes it adds to the 
 strong current-movement already in progress. 
 
 The piling up of the waters in a bay by the tides, or by 
 storms, produces, especially if the entrance is not very broad, 
 a strong out-flowing current at bottom, which tends to keep 
 the channel deep and clear of obstructions. 
 
 The in-flowing tide, sweeping along a coast, checks partly 
 or wholly the outflow of the rivers. This causes a deposition 
 of more or less of the detritus which the rivers transport, near 
 or against the shores or flats just beyond the river-channel ; 
 and thus it often makes great sand-flats, which encroach 
 on the entrance. If a long point projects on the side of the 
 mouth first reached by the in -flowing tide, the tidal flow may 
 carry the detritus far beyond the river's mouth; but if no 
 such point exists, and the opposite cape is the longer, the 
 detritus will be thrown into the throat of the stream, and 
 the entrance become more or less choked. The river mouths 
 of the Connecticut shore, on the north side of Long Island 
 Sound, along which the in-flowing tide moves westward, illus- 
 trate well these facts. The two largest of the rivers, the 
 Connecticut and Housa tonic, are of the unfortunate kind, as 
 they have no eastern cape, while New Haven, having only 
 very small streams, is much better off, as regards depth of 
 water for entrance, because of a projecting eastern cape. 
 
 The bore or eagre of some great rivers is a kind of tidal 
 flow up a stream. It is produced when the regular rise of 
 the tide in the bay at the mouth of the river is obstructed 
 by the form of the entrance and its sand-banks, together with 
 the outflow of the river, so that the waters are for a while 
 prevented from entering, until, finally, all those of one tide 
 rush in at once, or in a few great waves. The eagres of the 
 Amazon, the Hoogly in India (one of the mouths of the 
 Ganges), and the Tsien-tang in China, are among the most 
 remarkable. In the case of the Tsien-tang, the water moves 
 
110 DYNAMICAL GEOLOGY. 
 
 up stream in one great wave, plunging like an advancing 
 cataract, four or five miles broad and 30 feet high, at a rate 
 of 25 miles an hour. The boats in the middle of the stream 
 simply rise and fall with the passage of the wave, being 
 pushed forward only a short distance ; but along the shores 
 there is often great devastation, the banks being worn away 
 and animals sometimes surprised and destroyed. 
 
 3. Currents made by winds. There are also currents pro- 
 duced by winds, especially when there are long storms, or 
 when the winds blow for months in one direction. The great 
 currents of the oceans, such as the Gulf Stream, are attributed 
 by some physicists to this source. Such currents, sweeping 
 by a coast, transport from one place to another in their course 
 more or less of the sand of the shores, often making long 
 sand-flats or spits off the shores to leeward, as on the south 
 coast of Long Island and the more southern parts of the 
 Atlantic border. The action is aided by the tidal currents. 
 In some cases the drifted sand may be in part carried back 
 again when the season changes to that in which the wind 
 blows from the opposite direction. Other portions of detri- 
 tus may be carried by them away from the land and distri- 
 buted in the deeper waters. 
 
 The great currents of the ocean are for the most part so 
 distant from the borders of the continents that little detri- 
 tus comes within their reach. As these currents have great 
 depth, often a thousand feet or more, their course is 
 determined partly by the deep-water slopes of the submerged 
 border of a continent, so that when the border is shallow 
 for a long distance out (as off New Jersey and Virginia, where 
 this long distance is even 50 to 80 miles), the main body of 
 the current is equally remote. Wherever it actually sweeps 
 close along a coast, it may bear away some detritus to drop it 
 over the bottom in the neighboring waters. The flow of the 
 Gulf Stream against the submerged slope of the oceanic basin 
 (about three-fourths of a mile per hour) is sufficient to keep 
 the bottom free from loose detritus. Verrill has suggested 
 
WORK OF THE OCEAN. Ill 
 
 that the burrowing of fishes for food aids, by loosening the 
 material. 
 
 The oceanic currents flowing from polar seas produce im- 
 portant effects by means of the icebergs which they bear into 
 warmer latitudes. These icebergs are sometimes freighted 
 with earth and rocks; and wherever they melt, they drop 
 all to the ocean's bottom. The sea about the Newfound- 
 land banks is one of the regions of the melting icebergs ; 
 and there is no doubt that vast submarine accumulations 
 of such material have been there made by this means. It 
 has been suggested that the banks may have been thus 
 formed. 
 
 2. Distribution of material, and the formation of marine 
 and fluvio-marine deposits. 
 
 1. Origin of material. The material used by the waves 
 and currents is either (1) the stones, gravel, sand, clay, or 
 earth produced by the wear of coasts ; or (2) the detritus 
 brought down by rivers and poured into the ocean, as ex- 
 plained on page 98. 
 
 The latter, in the present age, is vastly the most important. 
 But in the earlier geological ages, when the dry land was of 
 small extent, rivers were small and were but a feeble agency. 
 The ocean had then vastly greater advantages than now, be- 
 cause, as stated on page 106, the continents were mostly sub- 
 merged at shallow depths, or lay near tide-level within reach 
 of the waves and currents. 
 
 The decomposition or disintegration of exposed rocks 
 through the agency of air and moisture must have aided in 
 degradation formerly more than now, since in Paleozoic time 
 and earlier, carbonic acid gas, the chief agent of destruction, 
 was much more abundant in the atmosphere than it is now. 
 This agent is carried to the earth's surface by the rains, and 
 it is still effective in the decomposition of granite, gneiss, and 
 many other rocks. 
 
112 DYNAMICAL GEOLOGY. 
 
 2. Forces in action. In the distribution of the material, 
 the waves and marine currents have either worked alone, in 
 the manner explained on the preceding pages, or in conjunc- 
 tion with river-currents wherever these existed. 
 
 3. Marine formations, The marine formations are of the 
 following kinds : 
 
 Beach-accumulations. Beaches are made of the material 
 borne up the shores by the waves and tides and left above 
 low-tide level. This material consists of stones or pebbles, 
 sand, mud, -earth, or clay. It is coarse where the waves break 
 heavily, because, although trituration to powder is going on 
 at all times, the powerful wave-action and the undercurrent 
 carry off the finer material into the off-shore shallow waters," 
 where it settles over the bottom or is distributed by currents. 
 It is fine where the waves are gentle in movement, as in shel- 
 tered bays, or estuaries, the triturated material remaining in 
 such places near where it is made, and often being the finest 
 of mud. 
 
 Sand-banks, or reefs ; Shallow-water accumulations. Shal- 
 low-water accumulations may be produced in bays, estuaries, 
 or the inner channels of a coast, and over the bottom outside. 
 They consist usually of coarse or fine sand and earthy de- 
 tritus, but may include pebbles or stones when the currents 
 are strong. The material constituting them is derived from 
 the land through the wearing and transporting action either 
 of the waves and currents, or of rivers. The accumulations 
 may increase under wave-action in shallow water, until they 
 approach or rise above low-tide level, and then they form 
 sand-banks. Such sand-banks keep their place in the faco 
 of the waves, for the same reason as the platform of rock 
 mentioned on page 107 and illustrated in Fig. 110. 
 
 Fluvio-marine formations. Most of the accumulations in 
 progress on existing shores, whether sand-banks, or estuary, 
 or off-shore deposits, especially about well-watered continents, 
 contain more or less of river-detritus, and are modified in 
 their forms by the action of river-currents. Along the whole 
 
WORK OF THE OCEAN. 113 
 
 eastern coast of the United States south of New England, 
 and on all the borders of the Gulf of Mexico, the formations 
 in progress are mainly flumo-marine, that is, the combined 
 result of rivers and the ocean. The coast-region on the con- 
 tinent is now slowly widening through this means, and has 
 been widening for an indefinite period : This coast-region is 
 low, flat, often marshy, full of channels or sounds ; and facing 
 the ocean there is a barrier-reef, made of sand. 
 
 The rivers pour out their detritus especially during their 
 floods, and the ocean's waves and currents meet it as the tide 
 sets in, with a counter-action, or one from the sea, ward ; and 
 between the two the waters, as they lose their velocity, drop 
 the detritus over the bottom. When the river is very large 
 and the tides feeble, the banks and reefs extend far out 
 to sea. The Mississippi thus stretches its many-branched 
 mouth (page 101) fifty miles into the Gulf. When the tide 
 is high, sand-bars are formed ; and the higher the tides the 
 closer are the sand-bars to the coast. When the stream is 
 small, the ocean may throw a sand-bank quite across its 
 mouth, so that there may be no egress to the river-waters ex- 
 cept by percolation through the sand, or, if a channel is left 
 open, it may be only a shallow one. 
 
 3. Structure of the formations. 
 
 Beach-formations are very irregular in stratification in their 
 upper portions, where they are made by the toss of the waves 
 combined with drifting by the winds. The layers as shown 
 in Fig. 22 d, page 45 have but little lateral extent, and 
 change in character every few feet. But the sloping part 
 swept by the waves below high-tide level is very evenly 
 stratified parallel to . the surface ; and since this surface 
 pitches at an angle usually of 5 to 15, the beach-made 
 beds have the same pitch or dip. The coarser beaches have 
 the highest slopes. 
 
 The sand-banks and reefs made in shallow waters along a 
 
 8 . 
 
114 DYNAMICAL GEOLOGY. 
 
 coast have a regular and more horizontal stratification, and 
 are mostly composed of sand with some beds of pebbles. 
 They often vary much every mile or every few miles. The 
 extent and regularity of level of the submerged area off a, 
 coast will determine in a great degree the extent to which 
 the uniformity of stratification may extend ; and in this 
 respect the former geological ages, as observed on page 106, 
 had greatly the advantage of the present. 
 
 Ripple-marks (Fig. 24, page 46) are made by the wash of 
 the waters over a sand-flat or up a beach, or over the bottom 
 within soundings ; also by wave-action where the waters are 
 not flowing. JRill-m-arJcs (Fig. 25) are produced when the 
 return waters of a tide, or of a wave that has broken on a 
 beach, flow by an obstacle, as a shell or pebble, and are piled 
 up a little by it so as to be made to plunge over it, and so 
 erode the sands for a short distance below the obstacle. The 
 cross-bedded structure results from the rapid inward move- 
 ment of the tide, or the flow of any current, over a sandy 
 bottom: it makes a series of inclined layers by the piling 
 action dipping in the direction of the movement ; when the 
 movement ceases, the detritus may deposit horizontally for a 
 while ; and afterward the flow and its results may be repeated. 
 When there are plunging waves accompanying the rapid flow 
 of a current, the obliquely laminated layer is broken up into 
 short wave-like parts, as in the flow-and-plunge structure 
 (page 45). 
 
 The imbedded shells and other animal relics in a beach are 
 commonly broken ; those in the bays or off-shore shallow 
 waters out of the reach of the waves may be unbroken, or may 
 lie as they did when living ; but if the waters are not so deep 
 but that the shells or corals are exposed to wave-action, they 
 may be broken or worn to powder, and enter in this state into 
 the formation in progress. (See further, page 79, the remarks 
 on the formation of limestone from shells or corals.) 
 
 Deposits of broken shells under water are sometimes 
 made by fishes that have ta,keu tbe animals for food. Such 
 
FREEZING AND FROZEN WATERS. 115 
 
 beds made by fishes answer to the shell-heaps of human 
 origin. 
 
 In the sands of beaches near low-tide level, borings of Sea- 
 worms, or of some Mollusks or Crustaceans, may exist. 
 
 3. Freezing and Frozen Waters. 
 
 A. Freezing Water. 
 
 As water in the act of freezing expands after reaching 
 39 *2 F. (4 C.), freezing in the seams of rock opens the seams 
 and tears masses asunder. The expansion on reaching 32 F. 
 is l-35th lineally, and the density is diminished to 0*92. 
 The results of expansion are most marked in rocks that are 
 much fissured, or intersected by joints, or that have a slaty 
 or laminated structure. As the action continues through 
 successive years and centuries, it often results in great accu- 
 mulations of broken stone. The slope, or talus, of fragments 
 at the foot of bluffs of trap or basalt is often half as high 
 as the bluff itself. In tropical countries, bluffs have no such 
 masses of ruins at their base. 
 
 Granular rocks, whether crystalline or not, when they read- 
 ily absorb water, lose their surface-grains by the same freez- 
 ing process. Granite, as well as porous sandstones, may thus 
 be imperceptibly turning to dust, earth, or gravel. In Alpine 
 regions this action may be incessant. 
 
 Alternate freezing and thawing produces (as explained 
 by Kerr) a movement of earth and gravel on slopes, with 
 re-arrangements of the materials. 
 
 B. Frozen Water. 
 
 The effects of ice and snow are conveniently considered 
 under three heads: 1. The ice of Lakes and rivers; 2. Gla- 
 ciers; 3. Icebergs. 
 
116 DYNAMICAL GEOLOGY. 
 
 I . Ice of Lakes and Rivers. 
 
 The ice of lakes and rivers often forms about stones along 
 their shores, and sometimes over those of the bottom (then 
 called anchor-ice), making them part of the mass ; and other 
 stones sometimes fall on shore-ice from overhanging bluffs. 
 The ice serves as a float to the stones ; and in times of high 
 water, or floods, it may carry its burden high up the shores, 
 or over the flooded flats, to leave them there as it melts. 
 Large accumulations of bowlders are sometimes made, by 
 this means, on shores far above the ordinary level of the 
 waters. 
 
 2. Glaciers. 
 
 1. Glaciers are ice-streams, or rivers in which the moving 
 material is frozen instead of liquid water. 
 
 Like large rivers, they ordinarily have their sources in high 
 mountains, and descend along the valleys ; but (1) the moun- 
 tains are such as take snow from the clouds instead of rain, 
 because of their elevation ; and (2) they must be high and 
 extensive enough to take annually a large supply of snow 
 from the clouds, so that the snow may accumulate to a great 
 depth ; and (3) the region must be one of sufficient precipi- 
 tation. 
 
 Like lar^e rivers, many tributary streams coming from the 
 different valleys unite to make the great stream. 
 
 As with rivers, their movement is dependent on gravity, or 
 the weight of the material ; but the average rate of motion, 
 instead of being several miles an hour, is generally in sum- 
 mer but 10 to 18 inches a day, or ajnile in 18 to 20 years. 
 12 inches a day corresponds to a mile in 14-| years. The 
 rate is half less in winter than in summer. 
 
 As with rivers, the central portions move most rapidly, the 
 sides and bottom being retarded by friction. 
 
 The snow of the mountain-tops, called the ntfve, which is 
 
GLACIERS. 117 
 
 perhaps hundreds of feet deep, becomes compacted and con- 
 verted into ice mainly by its own weight, through the aid of 
 water penetrating it derived from partial melting ; and thus 
 the glacier begins. Through the occasional melting and freez- 
 ing, the change to ice is made more complete. As the glacier 
 starts on its course, the clouds furnish new snows to keep up 
 the supply and help press on tliti moving mass. 
 
 2. Descent below the snow-line, The height, in the Alps, 
 of the snow-line, or that below which the snow annually pre- 
 cipitated melts during the year, is 8,000 feet on the north side 
 of the Alps, aad 8,800 feet on the south side ; and the glacier 
 descends below this line 4,500 to 5,300 feet. The ice resists 
 the melting heat of summer because of its mass, like the ice 
 in an ice-house. Though starting where all is white and 
 barren, it passes by regions of Alpine flowers, and often con- 
 tinues down to a country of gardens and human dwellings 
 before its course is finally cut short by the climate. Thus, 
 the Bois glacier, an upper portion of which is called the Mer 
 de Glace, rises in Mont Blanc and other neighboring peaks, 
 and terminates, like two other glaciers, in the vale of Cha- 
 mouni. In a similar manner, two great glaciers descend from 
 the Jungfrau and other heights of the Bernese Alps to the 
 plains of the Grindelwald Valley just south of Interlachen. 
 
 Fig. Ill represents one of the ice-streams of the Mount 
 Eosa region in the Alps; from a view in Professor Agassiz's 
 work on Glaciers. It shows the lofty regions of perpetual 
 snow in the distance ; the bare rocky slopes that border it, 
 later on its course; and the many crevasses that intersect the 
 surface of the ice-stream. 
 
 3. Fractures attending the movement. Crevasses. Every 
 valley has its ridgy sides, its sharp turns, its abrupt narrow- 
 ings and widenings, its irregular bottom ; and the stiff ice, 
 compelled to accommodate itself to these irregularities, has, 
 consequently, profound crevasses made usually along its bor- 
 ders, besides multitudes of cracks that are not visible at the 
 surface ; also, still profounder chasms when wrenched, or 
 
118 
 
 DYNAMICAL GEOLOGY. 
 
 stretched, in turning some point ; longer crevasses, crossing 
 even its whole breadth, when the ice plunges down a steep 
 place in an ice-cascade, or when, on escaping from a narrow 
 gorge, it moves off freely again with increase of slope. Again, 
 it may lose all its crevasses, from their closing up, when the 
 rate of motion is lessened by diminished slope or otherwise. 
 
 Fig. 111. 
 
 Glacier of Zermatt, or the Corner Glacier. 
 
 4. Glacier torrent. The melting of the glacier, especially 
 during the warm season, gives origin to a stream of water 
 flowing beneath it, which becomes gradually a torrent of con- 
 siderable size, and finally emerges to the light from beneath 
 the bluff of ice in which the glacier terminates. Thence it 
 continues on its rocky course down the valley. 
 
GLACIERS. 119 
 
 5. Method of movement. The capability of motion in a 
 glacier is (Ij dependent partly on a degree of plasticity in ice. 
 Ice may be made, through pressure, to copy a seal, or may be 
 drawn out into cylinders ; or, if a slab is supported only at 
 the sides, it will become bent downward, through gravity. 
 
 (2) It is also due in part to the facility with which ice 
 breaks. The ice afterward becomes a solid mass when the 
 broken surfaces are brought into contact. This re-gelation 
 was first noticed by Faraday. It is easily tried by breaking 
 a lump of ice and bringing the surfaces again into contact : 
 if moist, as they are at the ordinary temperature, they at once 
 become firmly united. A glacier moves on and accommo- 
 dates itself to its uneven bed by bending or breaking ; and, 
 however fractured, it may, when the movement slackens and 
 the parts are pressed together, become as solid as before. 
 
 Again (3), the ice is everywhere penetrated by water during 
 nearly all the year, and this diminishes the friction within 
 the mass. This moisture comes from above, but is added to 
 below because of the heat of friction. The greater amount in 
 summer is a cause of the more rapid movement then. 
 
 Again (4), a glacier may here and there, at times, slide 
 along its bed, yet only portions at a time. 
 
 6. Transportation by Glaciers. Moraines. Glaciers become 
 laden with stones and earth falling from the heights above, 
 or coming down in crushing avalanches of snow and stones. 
 
 o O 
 
 The stones and earth make a band along either border of a 
 glacier, and such a band is called a moraine. When two 
 glaciers unite, or a tributary glacier joins another, they carry 
 forward their bands of -stones with them; but those on the 
 uniting sides combine to make one moraine. A large glacier, 
 like that in Fig. Ill, may have many moraines, or one more 
 than the number of its tributaries. Some of the masses of 
 rock on glaciers are of immense size. One is mentioned 
 containing over 200,000 cubic feet, which is equivalent 
 in cubic contents to a building 100 feet long, 50 wide, and 
 40 high. 
 
120 DYNAMICAL GEOLOGY. 
 
 The ice also gathers up masses of rock from any hillocks 
 in the surface beneath it, easily detaching and bearing off 
 great slabs when the rocks are jointed or fractured. 
 
 In the lower part of a glacier the several moraines lose 
 their distinctness through the melting of the ice; for this 
 brings to one level what was distributed through a consider- 
 able part of its former thickness, and the surface, therefore, 
 becomes covered with earth and stones. The bluff' of ice 
 which forms the foot of a glacier is often a dirty mass, show- 
 ing little of its real icy nature, in the distant view. 
 
 The final melting leaves all the earth and stones in un- 
 stratified heaps or deposits, to be further transported, eroded, 
 and arranged, by the stream that flows from the glacier. 
 
 7, Erosion by Glaciers, A glacier laden with stones will 
 have stones in its lower surface and sides, as well as in its 
 mass. As it moves down the valley, it consequently abrades 
 the exposed rocks over which it passes, smoothing and pol- 
 ishing some surfaces, covering others closely with parallel 
 scratches, and often ploughing out broad and deep channels, 
 besides having its abrading bowlders scratched or pclished. 
 
 Deep ploughing is accomplished only (1) when the rock 
 beneath is soft or fragile, or (2) when it is jointed, rifted, or 
 laminated. In the latter case the action is rending, rather 
 than abrading, and by this means the larger part of the 
 direct excavation by glaciers has been done. 
 
 The rocky ledges over which the ice has long moved are 
 often reduced to rounded prominences ; they then look, in the 
 distance, like groups of crouching sheep, and hence have been 
 called, in French, roches moutonnees. They are exhibited on 
 a grand scale in some of the valleys of the high ranges along 
 the summit of the Eocky Mountains, where were formerly 
 extensive glaciers; and Fig. 112 represents one of the scenes, 
 in the region of the " Mountain of the Holy Cross " (the re- 
 moter summit near the centre of the view), as photographed 
 by the photographer of the Expedition under Dr. Hayden. 
 Further, the stones in the ever-shifting ice wear one another, 
 
GLACIERS. 
 
 121 
 
 and may thereby become rounded at the angles ; and the very 
 fine dust thus made is carried down by the waters along the 
 crevasses to make beds of clay or earth, and give a milky hue 
 to the streams flowing from a glacier region. 
 
 Fig. 112. 
 
 View on Roche-Moutoimee Creek, Colorado. 
 
 Glaciers deepen and widen the valleys in which they move. 
 But in this work they are aided by the frosts, avalanches, and 
 especially by the torrents beneath the glacier. 
 
 8. Glacier regions. The best known of Glacier regions are 
 those of the Alps, in one of which Mont Blanc stands, with 
 its summit 15,760 feet above the sea. There are glaciers 
 also in the Pyrenees, the mountains of Norway, Spitzbergen, 
 Greenland, and other Arctic regions, in the Caucasus and 
 Himalaya, in the Southern Andes, in the Coast range and 
 
122 DYNAMICAL GEOLOGY. 
 
 Kocky Mountain summits of British America. Greenland 
 is a great glacier- covered land, sending many large streams 
 through the fiords of the border region to the polar seas. 
 
 3. Icebergs. 
 
 When glaciers, like those of Greenland, terminate in the 
 sea, the icy foot becomes broken off from time to time, through 
 the varying movement of the tides ; and these fragments of 
 glaciers, floated away by the sea, are icebergs. The geological 
 effects of icebergs have been stated on page 111. Sea-shore ice 
 sometimes carries stones and gravel far out to sea. 
 
 4. Formation of Sedimentary Strata. 
 
 The following is a brief recapitulation of the explanations 
 of the origin of deposits given in the preceding pages. Igne- 
 ous and other crystalline rocks are not here included. 
 
 1. Sources of material. The material of sedimentary rocks, 
 excluding limestones, has come mainly from the degradation 
 of pre-existing rocks. But another part (as that of lime- 
 stones, or infusorial earth) has been taken up from a state of 
 solution in the ocean or in fresh waters, through the agency 
 of life ; yet the waters have received the ingredients from the 
 rocks, either when the ocean first began to exist, or subse- 
 quently through the dissolving action of streams on exposed 
 rocks (page 111). 
 
 The Archaean rocks were the original source ; and in 
 Eastern North America, where the formations of the Green 
 Mountains and Appalachians have great thickness, Archaean 
 ridges existed both over New England and on the Atlantic 
 borders. 
 
 2. Means of degradation. The principal means of degrada- 
 tion are the following: 1. Erosion by moving waters, either 
 those of the sea or land (pages 90, 107); 2. Erosion by ice, 
 either that of glaciers, icebergs, or ordinary snow and ice 
 
FORMATION OF SEDIMENTARY ROCKS. 123 
 
 (page 120); 3. Pressure of the water descending into fissures; 
 4. Forming of substances, for example oxide of iron, in cracks, 
 this tending to open and deepen the cracks ; 5. Growth of 
 rootlets, roots, and trunks of trees, in crevices, resulting in 
 opening and tearing apart rocks, and often producing exten- 
 sive destruction of rocks, especially when they are jointed ; 
 6. Freezing of water in fissures (pa.ge 115); 7. Chemical 
 decomposition of one or more of the ingredients of a rock, 
 in the course of which process the rock becomes crumbled or 
 reduced to earth ; 8. Kemoval by solution, as of limestones by 
 carbonated waters ; 9. Undermining of rocks by any method ; 
 10. Expansion and contraction by heat (page 128.) 
 
 3. Formation of deposits The principal methods by which 
 deposits have been formed are the following : 
 
 1. By the waters of the sea. 1. Through the sweep of the 
 ocean over the continents ivlicn barely or partly submerged, 
 making (a) sandy or pebbly deposits near or at the surface 
 where the waves strike, or at very shallow depths where 
 swept by a strong current ; (/;) argillaceous or shaly deposits 
 near or at the surface, where sheltered from the waves ; and 
 also, at considerable depths, out of material washed off the 
 land by the waves or currents ; but not malting (c) coarse 
 sandy or pebbly deposits over the deep bed of the ocean, as 
 even great rivers carry only silt to the ocean ; and not mak- 
 ing (//) argillaceous deposits over the ocean's bed except along 
 the borders of the land, unless by the aid of a river like the 
 Amazon ; in which case, still, the detritus is mostly thrown 
 back on the coast by the waves and currents. 
 
 2. Through the waves and currents of the ocean acting 
 on the borders of the continent ; the results are the same as 
 above, except that the beds so made have less extent. 
 
 3. Through living species, and mainly Mollusks, Radiates, 
 and Khizopods, affording calcareous material for strata ; and 
 Diatoms and some Protozoans, siliceous material. Most rocks 
 made of corals and the shells of Mollusks have required the 
 help of the waves, at least to fill up the interstices. 
 
124 DYNAMICAL GEOLOGY. 
 
 2. By the waters of lakes. Lacustrine deposits are essen- 
 tially like those of the ocean in mode of origin, unless the 
 lakes are small, when they are like those of rivers. 
 
 3. By the running waters of the land. 1. Filling the valleys 
 with alluvium and other fluvial deposits, and moving the earth 
 from the hills over the plains (page 98). 2. Carrying detritus 
 to the sea or to lakes, to make, in conjunction with the action 
 of the sea, or lake-waters, delta and other sea-shore accumu- 
 lations (pages 99, 100). 
 
 4. By frozen waters. A. Acting in the condition of gla- 
 ciers, and thus : 1. Spreading the rocks and earth of the 
 higher lands over the lower, and, in the process, bearing on- 
 ward blocks of great size, as well as finer material (pages 119, 
 120). 2. Distributing rocks and earth in lines or moraines. 
 B. Acting as icebergs ; and, in this condition, transporting 
 stones and earth to distant parts of the ocean, as from the 
 Arctic regions to the Newfoundland Banks, and so contribut- 
 ing to deep or shallow water or shore sedimentary accumula- 
 tions, distinguished by their containing huge blocks of stone, 
 besides pebbles, and earth. 
 
 V. HEAT. 
 1. Sources of Heat. 
 
 The crust of the earth derives heat from three sources : 
 1. The sun, an external source ; 2. The earth's heated inte- 
 rior ; 3. Chemical and mechanical action. 
 
 1. The Sun. This agency is peculiar in being regularly in- 
 termittent, through the alternations in the seasons, in day 
 and night, in the time of aphelion and perihelion, and in the 
 eccentricity of the earth's orbit. The amount of heat im- 
 parted to the earth varies also with the density of the atmos- 
 phere, the denser atmosphere absorbing more heat ; and it 
 was greater in early time, when the proportion of carbonic 
 acid and of moisture was greater than now. The following 
 
HEAT. 125 
 
 are some of the causes to which change in climate has been 
 attributed : 
 
 1. A gradual diminution in the heat of the sun through 
 the geological ages. 
 
 2. Variations in th.3 condition of the sun's exterior, causing 
 periodical alterations in the amount of heat radiated, and 
 thus producing alternating cold and warm eras. 
 
 3. Variations in the level of the earth's surface, the climate 
 becoming changed when extensive regions have been lifted into 
 mountains, as during the Tertiary age, or when great areas in 
 high latitudes have been elevated to a less extent ; and espe- 
 cially when the change in the level of the land or sea-bottom 
 has diverted the oceanic currents from one course to another. 
 Elevating the sea-bottom between Europe and Greenland 
 would shut out the warm Gulf Stream from the Arctic region 
 and increase its cold. For, according to Croll's calculations, 
 this stream contributes to the North Atlantic Ocean 77,479,- 
 650,000,000,000,000 foot-pounds of energy, in the form of 
 heat, per day. Such a change might, therefore, make a 
 glacier-cold climate for the northern hemisphere. On the 
 contrary, a subsideaca opaning Behring Straits for the free 
 passage of the tropical current of the Pacific would amelio- 
 rate the arctic climate. 
 
 4. Variations in the eccentricity of the earth's orbit. The 
 earth, through all such variations, derives the same amount 
 of heat annually from the sun, but not the same for the 
 winter as for the summer. The maxima of eccentricity are 
 unequal, and aro passed once in 100,000 to 200,000 years. 
 The earth is at present near a minimum, and the distance 
 from the sun h about 93'9 millions of miles in aphelion 
 (which comes now in summer), and nearly 90'9 millions in 
 perihelion the difference, 3 millions. About 110,000 years 
 since, a maximum occurred, with the aphelion and perihelion 
 distances 96 '65 and 88*15 millions of miles the difference, 
 8| millions; and 850,000 years since, an extreme maximum, 
 with these distances, 99*3 and 85 '5 millions the difference 
 
126 DYNAMICAL GEOLOGY. 
 
 13 -8 millions of miles. When the aphelion comes in winter, 
 the cold of the winters is increased, the amount of heat re- 
 ceived being inversely as the square of the distance (which 
 ratio gives for the heat in winter, during the extreme maxi- 
 mum referred to, about fths that now received in that season); 
 and, also, the winter half of the year between the equinoxes 
 will be, at the extreme maximum, 36 clays longer than the 
 summer half (now, it is 8 days shorter) ; at the same time, 
 the summers will be proportionally hotter, but, in the same 
 proportion, shorter. In the southern hemisphere the reverse, 
 in each respect, is true. The cold of a Glacial era has been 
 thus accounted for, and also the warmth of warm eras, by 
 Croll ; but others reject the theory. It admits of two 
 Glacial eras in the same hemisphere during one prolonged 
 time of maximum, since the aphelion has a cycle of only 
 21,000 years ; but it makes the southern Glacial era to come 
 10,500 years after the northern. Further, the ice of a Gla- 
 cial era tends to intensify and perpetuate the glacial condi- 
 tion, since it can take and radiate, even in the sunshine, no 
 temperature above that of the freezing-point. 
 
 5. A change in the earth's axis has been regarded as a 
 source of variation in climate. But calculations by Mr. G. 
 H. Darwin, Haughton, and others, have shown that no such 
 change can have taken place sufficient for any marked result. 
 
 2. Internal Heat. The fact of a high heat in the earth's 
 interior is established in various ways. 
 
 1. The form of the earth is a spheroid, and a spheroid of 
 just the shape that would have resulted from the earth's revo- 
 lution on its axis, provided it had passed through a state of 
 complete fusion, and had slowly cooled over its exterior. 
 Hence is drawn the conclusion that it has passed through 
 such a state of fusion, which is strengthened by the other 
 evidence here given. Another conclusion also follows : namely, 
 that the earth's axis had the same position (or, at least, very 
 nearly the same) when cooling began as now. There is no 
 evidence that there has been at any time a change. 
 
HEAT. 127 
 
 2. In deep borings for water and in shafts sunk in min- 
 ing, it has been found that the temperature of the earth's 
 crust increases, on an average, one degree of Fahrenheit for 
 every 64 feet of descent. The rate of 1 F. for 64 feet of 
 descent, in the latitude of New York, would give heat enough 
 to boil water at a depth of 10,000 feet ; and at a depth of 
 about 35 miles the temperature would be 3,000 F., or that of 
 the fusing-point of iron. Since, however, the fusing tempera- 
 ture of any substance increases with the pressure, the depth 
 required before a material like iron would be found in a 
 melted state would be much greater than this. Experiments 
 on the temperature in artesian borings have to guard against 
 error from the heat caused by chemical changes in the rocks 
 below, such as decompositions of sulphides. 
 
 3. The great Pacific Ocean has nearly a complete girt of 
 volcanoes, extinct or active ; and all of its many islands that 
 are not coral are wholly volcanic islands, excepting New 
 Zealand and a few others of large size in its southwest cor- 
 ner. Volcanoes occur along many parts of the Andes from 
 Tierra del Fuego to the Isthmus of Darien, in Central America, 
 in Mexico, California, Oregon, and beyond ; in the Aleutian 
 Islands on the north; in Kamtchatka, Japan, the Philip- 
 pines, New Guinea, New Hebrides, and New Zealand on the 
 west; and on Antarctic lands both south of New Zealand 
 and of South America. The volcanic region thus bounded is 
 equal to a whole hemisphere ; and, besides, there are vol- 
 canoes in many parts of the other hemisphere. Outlets of 
 lire so extensively distributed seem to indicate that there is, 
 or must formerly have been, some universal seat of fire 
 beneath. 
 
 4. The flexures which the earth's crust and its strata have 
 undergone over regions of continental extent, and even as 
 late as the Cenozoic, indicate that there have been, up to the 
 middle Cenozoic, if not later, as great regions of liquid rock 
 beneath the earth's crust. 
 
 3, Chemical and Mechanical action. In the upturning and 
 
128 DYNAMICAL GEOLOGY. 
 
 flexure of rocks attending mountain-making there have been 
 movements on a grand scale ; and, through the transforma- 
 tion of this motion into heat, the rocks have received in some 
 cases a high temperature, sufficient to promote, through the 
 moisture present, the consolidation of rocks, and even their 
 crystallization or metamorphism ; and also, in the view of 
 Mallet, their fusion on a scale grand enough to originate vol- 
 canoes. This is probably one chief source of the heat through 
 which the metamorphism and consolidation of rocks have 
 been produced, the other chief source being the internal 
 heat. 
 
 Heat is produced by condensation : as when vapors are 
 condensed, or become liquid or solid ; when liquids (as water) 
 become solid ; when oxidation or other like change takes 
 place, as when pyrite oxidizes (p. 82), a process that has set 
 fire to beds of coal. 
 
 2. Effects of Heat. 
 
 The following are the effects of heat here considered : 
 
 1. Expansion and contraction. 
 
 2. Igneous action and results. 
 o. Metamorpliism. 
 
 4. Formation of veins. 
 
 5. The heat of the globe is also one of the causes of earth- 
 quakes, of change of level in the earth's crust, and of the 
 elevation of mountains : these subjects are considered in the 
 following chapter. It is an important agent also in all 
 chemical changes. 
 
 0. Expansion and Contraction. 
 
 (1) Heat from any subterranean source penetrating upward 
 may cause wide eliancjes of level Lyell has calculated that a 
 mass of sandstone a mile thick, raised in temperature to 1,000 
 
HEAT. 129 
 
 F., would have its upper surface elevated 50 feet. Fractures 
 and displacements would be likely to attend such movements. 
 
 (2) The changing heat of the day, which in some countries 
 amounts to 80 F. or more, and also that of the seasons, is a 
 force always at work. The expansion and contraction may 
 gradually move blocks of rock from their places. Tt will 
 move the heated side of the block outward ; and if this outer 
 part so moved cannot, because of any wedging or the friction 
 at the edges, return with the succeeding contraction, the mass 
 will move to it or have its edges fractured. The Bunker 
 Hill obelisk at Charlestown in Massachusetts has been proved 
 to swing back and forth with the passage of the sun over it. 
 
 (3) The alternating action of expansion and contraction peels 
 off the grains or outer surface of rocks, and is a prominent 
 means of obliterating glacier markings. 
 
 Slirinkagc-cracks. (1) In the cooling of liquid rocks 
 shrinkage-cracks are produced, and thence come the colum- 
 nar structure of trap, basalt, etc. (page 48). (2) Similar 
 columnar forms are sometimes produced in sandstone after 
 heating, though in general only irregular cracks result. 
 (3) Heat penetrates rocks over wide regions wherever meta- 
 morphism is in progress ; and the subsequent cooling and 
 contraction may leave multitudes of fractures, in long lines 
 or in reticulations, the subsequent filling of which may make 
 veins. 
 
 Drying is another source of shrinkage-cracks. Tt makes 
 the shallow mud-cracks (page 46), the deep soil-cracks, yards 
 in depth, in countries of fertile prairies that have a long hot 
 and dry season, and may produce far deeper joint-like cracks 
 in mud-made rocks (shales and argillaceous sandstones) as 
 they become slowly dried from subterranean heat. Further, 
 the drying of beds produces a sinking of the surface. A soft 
 mud may contract to a tenth of its bulk. All mud-beds 
 will suffer a large diminution in thickness on drying ; 
 and when under overlying strata the pressure may -prevent 
 shrinkage-cracks from forming. 
 
130 
 
 DYNAMICAL GEOLOGY. 
 
 2. Igneous Action and Results. 
 
 A. General Nature of Volcanoes and their products. 
 
 Volcanoes are mountain-elevations of a somewhat conical 
 form, which have a crater at centre, and eject, from time to 
 time, streams of melted rock. If the fire-mountain has at 
 present no active fires within, and is emitting no vapors, it is 
 said to be extinct. 
 
 Fig. 113. 
 
 MOUNT VESUVIUS: from a sketch by the author in June, 1834. n, the cone; 
 6, summit cinder-cone ; c, Somma, part of former outline of crater ; d, Hermitage (now 
 Observatory) ; e, Portici ; /, Herculaneum ; g, Torre del Greco. For Map, see p. 398. 
 
 The cavity or pit in the top of a volcanic mountain, 
 called the crater, where the lavas may often be seen in 
 fusion, is sometimes thousands of feet deep, but may be 
 quite shallow ; and in extinct volcanoes it is often wholly 
 wanting, owing to its having been left filled when the fires 
 went out. 
 
 The liquid rock issuing from a crater, and the same after 
 becoming cold and solid, is called lava. 
 
HEAT. VOLCANOES. 131 
 
 An active crater, even in its most quiet state, emits vapors. 
 These vapors are mostly simple steam, or aqueous vapor ; but 
 in addition there are usually sulphur gases, and sometimes 
 carbonic acid and hydrochloric acid. 
 
 In a time of special activity fiery jets are sometimes thrown 
 up to a great height, which are made of red-hot fragments, 
 the fragments of great bubbles of lava produced by the 
 escaping vapors. The fragments cool as they descend about 
 the sides of the crater, and are then called cinders. 
 
 When a shower of rain, or of moisture from the condensed 
 steam, accompanies the fall of the cinders, the result is a 
 mud-like mass, which dries and becomes a brownish or yel- 
 lowish-brown layer or stratum, called tufa. Tufa is often 
 much like a soft coarse sandstone, except that the materials 
 are of volcanic origin. 
 
 The materials produced by the volcano are, then 1. La- 
 vas ; 2. Cinders ; 3. Tufas ; 4. Vapors or Gases, which are 
 mostly vapor of water, partly sulphur gases, and in some 
 cases also carbonic acid, hydrochloric acid, and some other 
 materials. 
 
 The lavas are of various kinds. They are more or less cel- 
 lular ; sometimes light cellular, like the scoria of a furnace ; 
 but more commonly heavy rocks, with some scattered ragged 
 cellules or cavities through the mass. A stream of lava of 
 this more solid kind, in a crater, has often a few inches of 
 scoria at top, as a running stream of syrup may have its 
 scum or froth. The most of the scoria has this scum-like 
 origin. Pumice is a very light grayish scoria, full of long and 
 slender parallel air-cells. 
 
 The black and brown lavas having high specific gravity 
 (above 2.8) are doleryte and related kinds containing much 
 pyroxene or hornblende ; while the gray or light-colored 
 kinds, like the trachytes (below 2.7 in specific gravity), con- 
 sist chiefly of a feldspar (see p. 37). 
 
 A volcanic mountain is made out of the ejected materials ; 
 either (1) out of lavas alone ; or (2) of cinders alone ; or (3) 
 
132 DYNAMICAL GEOLOGY. 
 
 of tufas alone ; or (4) of alternations of two or more of these 
 ingredients. As the centre of the mountain is the centre of 
 the active fires, the ejections flow off or fall around it, and 
 hence the form of a volcanic peak necessarily tends to become 
 conical. 
 
 The average angle of slope of a lava-cone is from 3 to 10 ; 
 of a tufa-cone, 15 to 30; of a cinder-cone, 30 to 42; of 
 mixed cones, intermediate inclinations according to their con- 
 stitution. 
 
 The ordinary slope of a cinder cone is shown in Fig. 113. 
 Etna, about 10,000 feet high, and Mount Loa of Hawaii, 
 nearly 14,000 feet, consisting mainly of lava streams, have 
 an average slope of less than 10 degrees. The form of a cone 
 with a slope of 7 degrees which is the average for the 
 Hawaian volcanoes is shown in Figs. 114, 115. Fig. 114 
 has a pointed top, like Mount Kea, and Fig. 115 a rounded 
 outline, like Mount Loa, whose form is that of a very low 
 dome. 
 
 Fig. 114. 
 
 B 
 
 Mount Kea. 
 
 Fig. 115. 
 
 Mount Loa. 
 
 The highest of volcanic mountains on the globe are the 
 Aconcagua peak in Chili, 23,000 feet, and Sorata and Illi- 
 raani, in Bolivia, each over 24,000 feet. The former appears 
 to be still emitting vapors, showing that the 'fires are not 
 wholly extinct. The mountains Shasta. Hood, St. Helen's, and 
 others in California and Oregon, are isolated volcanic cones 
 
HEAT. VOLCANOES. 
 
 133 
 
 11,000 to 14,400 feet high, the last being the height of Mount 
 Shasta. The average slope of the upper half of Mount Shasta 
 is about 27. The slopes of most of the lofty volcanoes of 
 the Andes are between 25 and 34. 
 
 B. Volcanic Eruptions. 
 
 The process of eruption, though the same in general method 
 in all volcanoes, varies much in its phenomena. The funda- 
 
 Fig. 116. 
 
 Map of part of Hawaii. 
 
 mental principles are well shown at the great craters of Ha- 
 waii, the southeasternmost of the Hawaian (or Sandwich) 
 Islands. 
 
 1. Hawaian Volcanoes. 1. General description. Hawaii is 
 made up mainly of three volcanic mountains, two, Mount 
 Loa and Mount Kea (Figs. 114, 115, p. 132), nearly 14,000,feet 
 high ; and one (the western), Mount Hualalai, about 10,000 
 feet. Mount Kea is alone in being extinct. 
 
134 DYNAMICAL GEOLOGY. 
 
 Mount Loa has a great crater at top, and another inde- 
 pendent one 4,000 feet above the level of the sea (at P, Fig. 
 117). The latter is the famous Kilauea, called also Lua Pele 
 or Pele's pit, Pele being, in the mythology of the Hawaians, 
 the goddess of the volcano. 
 
 The accompanying map of the southeastern portion of Ha- 
 waii, Fig. 116, shows the positions of Mount Loa and Mount 
 Kea, and of the crater of Kilauea, besides other craters at the 
 summit of Mount Loa, and at P, A, B, C, K, and east of K. 
 
 2. Kilauea. The crater of Kilauea is literally a pit. It is 
 three miles in greatest length, and nearly two in greatest 
 breadth, and about seven and a half miles in circuit. It is 
 large enough to contain Boston proper to South Bridge, three 
 times over, or to accommodate 400 such structures as St. Pe- 
 ter's at Eome. The pit has nearly vertical sides of solid rock 
 (made of lavas piled up in successive layers), and has been 
 1,000 feet in depth after several of its eruptions, and 400 to 
 600 previous to its eruptions. The bottom is a great area 
 of solid lava, with one or more lakes or pools of liquid lava, 
 or crater-like openings, from which vapors rise. The largest 
 lake was, in 1840, 1,000 feet in diameter. The interior may 
 be surveyed from the brink of the pit, even when in most 
 violent action, as calmly and safely as if the landscape were 
 one of houses and gardens. 
 
 3. Action in Kilauea. The ordinary action, as well exhib- 
 ited in several great eruptions, is simply this. The lavas in 
 the active pools are in a state of ebullition, jets rising and 
 falling as in a pot of boiling water, with this difference, that 
 the jets are 30 to 100 feet high. Such jets, in lava as well 
 as water, arise from the effort of vapors to escape ; in water 
 the vapor is steam derived from the water itself ; in lavas it 
 is chiefly steam from waters that have gained access to the 
 fires, but also gases derived from materials in the lavas, or 
 from depths below. 
 
 The lavas of the pools or lakes overflow at times and spread 
 in streams across the great plain that forms the bottom of the 
 
HEAT. VOLCANOES. 135 
 
 crater. In times of great activity the pools and lakes are 
 numerous, the ebullition incessant, the jets higher, and the 
 overflowings follow one another in quick succession. 
 
 4. Cause of eruption. By these overflows the pit slowly 
 fills. In the intervals between 1823 and 1832, and 1832 and 
 1840, the bottom was raised 400 feet or more above the lowest 
 level, so that the depth was reduced from 1,000 to 600 feet 
 or less. The addition of 400 feet increased 400 feet the 
 height of the central column of liquid lava of the crater, and 
 caused a corresponding increase of pressure against the sides 
 of the mountain. The amount of this pressure is at least 
 two and a half times as great as that which an equal column 
 of water would produce. The mountain should be strong to 
 bear it. The lavas at such times may be in a state of violent 
 activity, and a large addition to the pressure against the sides 
 of the mountain comes from the force of the imprisoned vapors. 
 
 The consequence of this increase of pressure, both from the 
 lavas and the augmented vapors, may be, and has several 
 times been, a breaking of the sides of the mountain. One or 
 more fractures result, and out flows the lava through the 
 openings. Thus simple have been the eruptions. 
 
 In the eruption of 1840 the lavas first appeared at the sur- 
 face a few miles below Kilauea (at P, Fig. 116), and then 
 again at other points more remote, A, B, C, m ; finally a stream 
 began at n, a point 20 miles from the sea, which continued 
 to the shores at Nanawale. Here, on encountering the waters, 
 the great flood of lava was shivered into fragments, and the 
 whole heavens were thick with an illuminated cloud of vapors 
 and cinders, the light coming from the fiery stream below. 
 The lavas which escaped at this relatively small eruption 
 amounted to at least 15,400,000,000 cubic feet. 
 
 This eruption of Kilauea took place, it will be observed, 
 not over the sides of the crater, but through breaks in the 
 mountain's sides below; and the pressure of the column of 
 lava within, and that of the escaping vapors, appear to have 
 caused the break. 
 
136 
 
 DYNAMICAL GEOLOGY. 
 
 5. Summit- crater of Mount Loa. Eruptions have also taken 
 place from the summit-crater of the same mountain (Mount 
 Loa), or at a point nearly 14,000 feet high above the sea ; and 
 in each case there has been, not an overflow from the crater, 
 but an outflow through breaks in the sides of the mountain. 
 
 Fig. 117. 
 
 ISLAND OF HAWAII. L, Mount Loa; K, Mount Kea ; H, Mount Hualalai : P, 
 Kilauea or Lua-Pele ; 1, Eruption of 1843 ; 2, of 1852 ; 3, of 1855 ; 4, of !Si9 ; a, Wahnea ; 
 6, Kawaihae ; c, Wainaualii ; d, Kaliua ; e, Kealakekua ; /, Kaulanamauna ; g, Kailiki ; 
 h, Waiohinu ; i, Honuapo ; j, Kapoho ; fc, Nanawale ; I, Waipio ; ra, first appearance of 
 eruption of 1868 ; n, Kahuku. The course of the currents, 1, 2, 3, and 5, are from a map 
 by T. Coan, and 4, from one by A. F. Judd. 
 
 In 1852 there was first a small issue of lavas near the sum- 
 mit, and then another of great magnitude about 10,000 feet 
 above the sea-level. At this second outbreak the lava was 
 thrown up in a fountain, or mass of jets, two or three hundred 
 feet high ; and thus it continued in action for several days. 
 The forms of the fountain of liquid fire were compared by 
 
HEAT. VOLCANOES. 137 
 
 Kev. Mr. Coan to the clustered spires of a Gothic cathedral. 
 Similar lava fountains have been observed also at other erup- 
 tions of the volcano. 
 
 The pressure producing the jet in the case above mentioned, 
 so far as it was hydrostatic, was that of the column of lava 
 between the point of outbreak and the level of the lavas in 
 the summit-crater, 3,000 to 4,000 feet above. The same 
 pressure in connection with confined vapors must have caused 
 the breaking of the mountain in which the eruption began. 
 
 Usually, no great earthquakes accompany the Hawaian erup- 
 tions, sometimes not even slight ones, the first announcement 
 being merely " a light on the mountain." Moreover, when the 
 summit-crater has been thus active, Kilauea, though 10,000 
 feet lower on the same mountain and even a larger pit-crater, 
 commonly shows no agitation, no signs whatever of sympathy. 
 
 The black bands descending from the summit-crater, on 
 the map, Fig. 117, show the courses of four great outflows of 
 lava. The scale of the map is 38 miles to the inch. 
 
 6. Conclusions. These cases of eruption indicate (I) that 
 the lavas go on gradually increasing the pressure in the in- 
 terior by their accumulation, while augmented activity in the 
 production of vapors increases still further the pressure ; and 
 that finally the mountain, when it can no longer resist the 
 forces within, somewhere breaks and lets the heavy liquid 
 out. They show (2) that while earthquakes may attend vol- 
 canic action, they are no necessary part of it. They show (3) 
 that lavas may be so very liquid that no cinders are formed 
 during a great eruption ; for in the ebullition of the lava in 
 the boiling lakes of Kilauea, the jets (made by the confined 
 vapors) are usually thrown only to a height of 30 to 100 feet ; 
 and on falling back, the material is still hot and does not 
 become cooled fragments ; it either falls back into the pool or 
 lake, or becomes plastered to its sides. The liquidity of the 
 lavas is shown by the jetting out sometimes, from small holes, 
 of drops but a fourth of an inch thick, which fall back on one 
 another, adhere, and so make a model of a little fountain. 
 
138 DYNAMICAL GEOLOGY. 
 
 At some of the eruptions of Mount Loa the lava has con- 
 tinued down the mountain to a distance of 50 or 60 miles. 
 
 2. Vesuvius. Vesuvius is an example of another type of 
 volcano. The lavas are so dense or viscid that jets cannot 
 rise freely over the surface : the vapors are therefore kept 
 confined until they form a bubble of great dimensions ; and 
 when such a bubble, or a collection of them, bursts, the frag- 
 ments are sometimes thrown thousands of feet in height. The 
 crater, at a time of eruption, is a scene of violent activity, 
 and cannot be approached. Destructive earthquakes often 
 attend the eruptions. 
 
 The lavas at Vesuvius may flow directly from the top of 
 the crater ; but they generally escape partly, if not entirely, 
 through fissures in the sides of the mountain. 
 
 3. Comparison of Mount Loa and Vesuvius as to causes of 
 eruption and nature of the mountains. Of the two causes of 
 eruption, hydrostatic pressure and elastic force of con- 
 fined vapors, the latter appears to be the most effective at 
 Vesuvius, while the former may be at Hawaii. Mount Loa, 
 on Hawaii, is an example of the great free-flowing volcanoes 
 of the world, and the mountain is almost wholly a lava-cone. 
 Vesuvius is an example of a smaller vent with less liquid 
 lavas ; and the cone is made up of both solid lavas and cin- 
 ders. The activity in Mount Loa appears to be kept up 
 mainly by the fresh waters (rains) which fall over the moun- 
 tain and descend through the rocks to the fires ; while Vesu- 
 vius is in part, at least, supplied by salt waters from the 
 Mediterranean, as is proved by hydrochloric acid in its 
 vapors, and the chlorides among its saline incrustations. 
 The waters of any subterranean streams cannot be driven 
 back by the lavas, owing to the pressure above, and hence 
 they must enter and be taken up by the lavas. But in 
 all volcanoes there must be a gradual supply of lavas from 
 below, through the action of vapors of a deep-seated source, 
 or else the heat would sooner give out. 
 
 4. Trachytic hills. Feldspathic lavas, such as trachyte, are 
 
HEAT. VOLCANOES. 139 
 
 less common in modern volcanoes than the dolerytic. They 
 have in some cases preceded doleryte in the history of a 
 volcanic cone. They are less fusible than the latter, because 
 the feldspar orthoclase, which is the chief constituent, is a 
 mineral of rather difficult fusibility. In some cases these 
 feldspathic lavas have come up through fissures in so pasty a 
 state that they have swelled up into steep domes and cooled 
 in this form. Domes of this kind occur in Auvergne ; also in 
 the Black Hills (Newton and Jenny's Eeport). 
 
 5. Lateral cones of volcanoes. In eruptions through fissures 
 the lavas may continue issuing for some days or weeks through 
 the more open or widest part of the fissure, and consequently 
 form at this point a cone of cinders or lavas. Thus have 
 originated innumerable cones on the slopes of Etna and other 
 volcanic mountains. 
 
 6. Submarine eruptions. Eruptions may sometimes take 
 place from the submarine slopes of the mountain when it is 
 situated near the sea, as has happened with Etna and Mount 
 Loa ; and in such cases accumulations of tufa, or of solid 
 lavas, may form under water about the opened vent. Fishes 
 and other marine animals are usually destroyed in great 
 numbers by such submarine eruptions. 
 
 7. Subsidences of volcanic regions. Overwhelming of cities. 
 Among the attendant effects of volcanoes are the sinking 
 of regions in their vicinity that have been undermined by 
 the outflow of the lavas ; the tumbling in of the summit of 
 a mountain ; and earthquakes, or vibrations of the rocks and 
 also of the air, in consequence of fractures. Another is the 
 burial, not only of fields and forests, but even of cities and 
 their inhabitants, by the outflowing streams, or by the falling 
 cinders and accumulating tufas. Pompsii and Herculaneum 
 are two of the cities that have been buried by Vesuvius ; and 
 every few years we hear of some new devastation of habita- 
 tions or farms by this uneasy volcano. Pompeii was buried 
 beneath tufas alone ; Herculaneum lies under tufas, lava- 
 streams of several later eruptions, and aii Italian city. 
 
140 DYNAMICAL GEOLOGY. 
 
 C. Subordinate Volcanic Phenomena. 
 
 Solfataras. In the vicinity of volcanoes, and sometimes 
 in regions in which no volcanoes exist, there are areas where 
 steam, sulphur vapors, and perhaps carbonic acid and other 
 gases, are constantly escaping. Such areas are called sol- 
 fataras (from the Italian, solfo, sulphur, and terra, earth). 
 The sulphur gases deposit sulphur in crystals or incrusta- 
 tions about the fumaroles (as the steam-holes are called) ; and 
 alum and gypsum often form from the action of sulphuric 
 acid (another result from the sulphur gases) on the rocks. 
 
 Hot springs. Geysers. Fountains or springs of hot waters 
 are common in places of this kind, and are often so abundant 
 as to be used for baths. Such springs occur also in many 
 other parts of the world, especially in regions of upturned or 
 of eruptive rocks. In some cases the heat is produced by 
 chemical changes in progress beneath ; but often the source 
 is the same as for volcanic heat. 
 
 When the heated waters are thrown out in intermittent jets 
 they are called geysers. The Yellowstone Park in the Rocky 
 Mountains (between the parallels of 44 and 45 N., and the 
 meridians of 110 and 111 W.) is the most remarkable region 
 of geysers in the world, far exceeding that of Iceland. One 
 of the geysers the " Beehive " is represented in action in 
 Fig. 118. The action of geysers is owing (1) to the access of 
 subterranean waters to hot rocks, producing steam, which 
 seeks exit by conduits upward; (2) to cooler superficial 
 waters descending those conduits to where the steam pre- 
 vents farther descent, and gradually accumulating until the 
 conduit is filled to the top ; (3) to the heating of these upper 
 waters by the steam from below to near the boiling point ; 
 when (4) the lower portion of these upper waters becomes 
 converted into steam, and the jet of water or the eruption 
 ensues. The "Beehive" jet is 200 feet high. It plays 
 once a day; others play every hour= 
 
NON-VOLCANIC IGNEOUS EEUPTIONS. 141 
 
 Heated waters act on the rocks with which they are in con- 
 tact and decompose them ; and as such rocks usually contain 
 
 Fig. 118. 
 
 Beehive Geyser in action. 
 
 some kind of feldspar, they become slightly alkaline through 
 
142 DYNAMICAL GEOLOGY. 
 
 the alkali of the feldspar, and so are enabled to take up 
 silica and make siliicom solutions. The "soluble glass," used 
 as a cement, is a sodium silicate like that of the geyser. 
 The silica taken into solution is deposited again around the 
 geysers in many beautiful forms, and besides makes the bowl 
 or crater from which the waters are thrown out, and forms 
 numerous petrifactions. 
 
 When the region of a boiling pool consists of earth or mud, 
 mud-cones are formed, as in some parts of the Yellowstone 
 Park, and also at Geyoer Canon (a branch from Pluton 
 Canon), north of San Francisco, California. 
 
 Besides hot springs that deposit silica, there are others that 
 deposit calcium carbonate, making thus the kind of porous 
 limestone called travertine, as on Gardiner's River, Yellow- 
 stone Park. 
 
 In some cases the action of the heated waters on the rocks? 
 exposed to them gives origin to deposits of quartz crystals, 
 agate, opal, and different silicates and other minerals. 
 
 D. Igneous Eruptions not Volcanic. 
 
 It has been stated that eruptions of volcanoes generally 
 take place through fissures. Fissure-eruptions have also oc- 
 curred in regions remote from volcanoes ; and they have been 
 the source of ejections over the western slope of the Rocky 
 Mountains vastly greater than any from volcanic centres. 
 Such fractures of the crust of the earth must have descended 
 to some seat of fires or liquid rock. Whatever cause was 
 sufficient to break through to the fire-region below would 
 have sufficed to press out the liquid rock from beneath. The 
 narrow mass of igneous rock which fills such fissures is called 
 a dike (page 43). The liquid rock has sometimes merely 
 filled the fracture, without overflowing ; but in other cases it 
 has spread widely over the surface, making strata of great 
 extent and thickness. The outflow of liquid rock has often 
 been followed by sedimentary deposits over the region, and 
 
NON-VOLCANIC IGNEOUS ERUPTIONS. 143 
 
 then another outflow has taken place ; thus making alterna- 
 tions of fire-made and water-made strata. 
 
 The ordinary rocks of dikes are described on page 38. 
 The igneous rock is very often without cellules or air-cavities ; 
 and, if any are present, they are in general neatly formed, in- 
 stead of being ragged like those of lavas. Such a rock, having 
 the cavities filled with minerals (as quartz, calcite, zeolites, 
 etc.), is called an amygdaloid. The rock of an amygdaloid is 
 usually hydrous (and chloritic) throughout (owing, it is sup- 
 posed, to subterranean waters gaining access in some way 
 while the eruption was in progress) ; and the cavities were 
 formed in the outer or upper part where the diminished pres- 
 sure allowed of the water's passing to the state of vapor. 
 
 Dikes are common on all the continents, especially in the 
 regions between the summits of the border mountains and 
 the ocean which are usually between 300 and 800 miles in 
 breadth ; as, for example, between the Appalachians and the 
 Atlantic, and between the Rocky Mountains and the Pacific. 
 
 The Pacific slope of the Rocky Mountains ^500 to 800 
 miles wide) is remarkable for its lava floods. Some of them 
 are around volcanoes, or volcanic vents, but many were from 
 fissure eruptions remote from any central source. Along 
 Snake Elver (the southern fork of the Columbia), in Idaho, 
 a single field covers 24,000 square miles, and is 275 miles in 
 length from east to west. To the eastward there are some 
 volcanic " buttes," and the flow appears to have been west- 
 ward ; but it is evident from their size that these were not 
 the source of the widespread lavas. Of the many successive 
 outflows, the earliest were of grayish trachyte, the later, of 
 blackish dolerytc (C. King). As usual with la, /as coming 
 from great depth through fissures (where pressure prevents 
 vapor-expansion), no scoria occurs over the surface. 
 
 On the Upper Columbia, in Oregon, between the lofty Mt. 
 Hood, with its fellows of the Cascade Range, and Lewiston, 
 250 miles to the eastward, a similar lava-field has an area of 
 30,000 square miles, or, with the Mt. Hood region included, 
 
144 DYNAMICAL GEOLOGY. 
 
 40,000. For long distances there are walls bordering the 
 river 1,000 to 2,000 feet high, made of ranges of basaltic 
 columns, and toward Mt. Hood, the thickness is 3,500 feet. 
 Again, in Northern California, south of the combined vol- 
 canic area of Mt. Shasta and Lassen's Peak, on the west 
 slope of the Sierra, the lavas of large isolated fissure-erup- 
 tions were so copious as to have obliterated the deep valleys 
 of an old system of drainage, and forced the streams to make 
 new channels. The erosion then begun has since cut out 
 valleys 1,000 to 3,000 feet deep, partly along new routes, and 
 far down into the subjacent rocks, leaving the remnants of 
 the lava-field as caps of "Table Mountains." The miners 
 have tunnelled beneath the lava-cap for gold-bearing gravels, 
 and found rich deposits in the beds of the old streams. 
 (J. D. Whitney.) Nevada, Southern Utah, Colorado, New 
 Mexico, and Arizona have other wide lava-fields. 
 
 Still more wonderful are the fissure eruptions of the Dec- 
 can, in India, where a railway out of Bombay runs for 519 
 miles continuously over a lava-field; its area is not less than 
 200,000 square miles. 
 
 In Eastern North America, outflows through fissures made 
 the Palisades on the Hudson ; long narrow ranges through 
 the Connecticut valley, including, among the summits, Mt. 
 Tom andMt. Holyoke; ridges in Nova Scotia; others similar, 
 at intervals from New Jersey to North Carolina ; and others, 
 in the vicinity of Lake Superior. The rocks of the Salisbury 
 Craigs near Edinburgh, and of the Giants' Causeway and 
 Fingal's Cave, are other examples. 
 
 The lava-streams have sometimes alternated with sedimen- 
 tary deposits, made largely of beds of tufa and called "ash 
 beds." They have in many cases intruded between pre-existing 
 strata; and in this case have left effects of the heat on the 
 overlying as well as the underlying bed, that is, if moisture were 
 present to help the heat. Further, the intrusion of trachytic lava 
 has at times lifted the overlying strata high enough to make 
 subterranean dome-shaped masses 1,000 to 4,000 feet high 
 
NON-VOLCANIC IGNEOUS ERUPTIONS. 
 
 145 
 
 (named laccoliths, from the Greek for lake and stone) ; as in 
 the Henry Mountains, Southern Utah, where denudation has 
 exposed to view the laccoliths. (G. K. Gilbert.) Ten thou- 
 sand feet of Tertiary strata are described as having been thus 
 lifted, evidence of the vastness of the erupting force. 
 
 The following view (from a sketch by the author, in 1840) 
 represents a scene of columnar basalt in Illawarra, New South 
 
 Fig. 119. 
 
 Basaltic columns, coast of Illawarra, New South Wale.s. 
 
 Wales, another region of fissure eruptions. The verticality 
 of the columns is proof of the near horizontality of the flow 
 of basaltic lava. 
 
 3. Metamorphism. 
 
 1. Metamorphism. The term metamorphism signifies change 
 or alteration; and, in Geology, a change, in the earth's rocks 
 or strata demanding some heat, but less than for fusion, and 
 resulting in crystallization, or, at least, firm solidification. 
 Such changes may be either regional or local. 
 
 2. Regional Metamorphism. In regional metamorphism, 
 the regions undergoing change have often been thousands of 
 square miles in area, and the depth to which the alteration 
 has extended has sometimes exceeded 30,000 feet. The rocks 
 were originally uncrystalline limestones, shales, sandstones, 
 
 10 * 
 
146 DYNAMICAL GEOLOGY. 
 
 conglomerates. They are changed to crystalline limestone or 
 marble, mica-schist, gneiss, and the like (page 35). They 
 were originally in horizontal strata; they are now upturned 
 or folded, and are often intersected by veins. 
 
 New England is mostly covered by metamorphic rocks ; 
 and they spread over the eastern border of New York, to 
 New York Island. They are the rocks of the Adirondacks 
 and much of Canada ; of the Highlands of New Jersey and 
 Putnam County, N. Y. ; of the Blue Ridge and the Black 
 Mountains ; of a large area south of Lake Superior ; of high 
 ranges along the summit of the Eocky Mountains ; and of the 
 Sierra Nevada in California. They occur also in Scotland, 
 Wales, Cornwall, Scandinavia, and various other countries. 
 
 Proof that such crystalline rocks are metamorphic, and not 
 igneous, is found (1) in their bedded structure answering 
 usually to the original bedding of the strata ; and (2) in the 
 occurrence, in some portions of a metamorphic stratum, 
 where the change is least complete, of unobliterated fossils : 
 as in part of the marble of West Rutland and other places 
 in Vermont; the limestone and schists near Poughkeepsie 
 and elsewhere in Dutchess County, N. Y. ; in the Sierra 
 Nevada ; and in several localities in Europe. 
 
 3, Effects. The effects of metamorphism include : 
 
 (1.) Simple compacting and solidification ; as in making 
 quartzyte from sandstone, or a rock looking like granite from 
 granitic sandstone. 
 
 .(2.) A change of color; as the gray and black of common 
 limestone to the white color, or the clouded shadings, of mar- 
 ble ; and the brown and yellowish-browp of some sandstones 
 colored by iron, to red, making red sandstone and jasper-rock. 
 
 (3.) In most cases, a partial or complete expulsion of water, 
 but not in all ; for serpentine, a metamorphic rock, is one 
 eighth (or 13 per cent) water. 
 
 (4.) An evolving and expulsion of mineral oil or gas ; as 
 when bituminous coaljs changed to anthracite or graphite. 
 
 (5.) An obliteration of all fossils ; or of nearly all if the 
 
METAMORPHISM. 147 
 
 metamorphism is partial. The obliteration is usually pre- 
 ceded by the compression and distortion of the fossils. 
 
 (6.) Often a change in crystallization with little or none in 
 chemical constitution ; as when a limestone is turned to white 
 statuary marble ; and a sandstone or argillaceous rock, made 
 from the granulation of granite, gneiss, and related rocks, is 
 changed to granite or gneiss again. 
 
 (7.) In many cases, a change of constitution; for the ingre- 
 dients subjected to the metamorphic process often enter into 
 new combinations : as when a limestone, with its impurities 
 of clay, sand, phosphates, and fluorides, gives rise, under the 
 action of heat, not merely to white granular limestone, but to 
 various crystalline minerals disseminated through it, such as 
 rnic<(, fclds'par, scapolite, pyroxene, apatite, chondroditc, etc. 
 
 It is thus seen that metamorphism may fill a rock with 
 crystals of various minerals. Even the gems are among its 
 results ; for topaz, sapphire, emerald, and diamond have been 
 produced through metamorphic action. What is of more 
 value, it makes out of rude sandstones and limestones crystal- 
 line rocks, as granite and marble, for architectural and other 
 uses. Man's imitations of nature are seen in his little red 
 bricks. 
 
 4. Prosess. Water and heat are two agencies essential in 
 metamorphism. 
 
 Heat is important : (1) in order to produce that weakening 
 of cohesion in and among the particles of a rock which is the 
 preparatory step toward a recrystallization ; and (2) in order 
 to bring about the chemical changes that are required, nearly 
 all demanding a higher than the ordinary temperature, though 
 less than that of complete fusion. 
 
 Water is important because : (1) dry rocks (as illustrated in 
 a fire-brick) are bad conductors of heat ; (2) it helps greatly 
 in the weakening of cohesion ; (3 ) it takes up silica and alkali 
 from all rocks containing feldspar (p. 142) if heated (and 
 little heat is necessary), and thus becomes a siliceous solution, 
 which, on cooling, may deposit the silica as a cement among 
 
148 DYNAMICAL GEOLOGY. 
 
 the grains of the rock and so promote its solidification as in 
 altering sandstone to quartzyte and may also deposit quartz 
 in cavities or fissures ; (4) at higher temperature, in the state 
 of steam of high pressure, it decomposes readily most of the 
 silicates or the ordinary minerals of rocks, and so prepares for 
 the formation of new minerals thus making soniet lines feld- 
 spar, mica, hornblende, etc. The quartz grains of a sandstone 
 have often had the grains converted into minute crystals of 
 quartz by the deposition of silica over the exterior. 
 
 The source of the water is for the most part the rocks them- 
 selves ; for beds of sandstone, limestone, etc. contain, before 
 alteration, on an average at least 2 per cent of water (inde- 
 pendently of any in spaces between the beds), which means 
 2 pints of water to 100 pounds of the rock ; and since a cubic 
 inch of water will make a cubic foot of steam at the ordinary 
 pressure, this agent is in great quantity, and is well distributed 
 for action. 
 
 The source of the heat is (1) partly mechanical ; for meta- 
 morphism has generally taken place when the rocks were 
 undergoing shovings, foldings and faultings, and sometimes 
 crushings (see page 128) ; and (2) partly also, that of the 
 earth's interior heat conducted upward into the beds (page 
 127). 
 
 These are some of the various ways in which heated and 
 superheated waters have aided in metamorphic changes. 
 Direct experiments have shown that these kinds of crys- 
 tallizations do result from the action of heat. 
 
 Quartz crystals, feldspars, mica, and other species have 
 been artificially made by the subjection of the ingredients to 
 highly heated moisture. Siliceous solutions form in waters 
 below the boiling point ; and wherever they exist they may 
 work at consolidation, erosion, and the making of layers and 
 veins of quartz. Large corals in Florida have been hollowed 
 out by this means, and the cavities lined with quartz crystals 
 or agate. 
 
 The fossils of a limestone have been silicified and flint 
 
METAMORPHISM. 149 
 
 nodules made even in cold waters. The ordinary decompo- 
 sition of a feldspar or mica, of hornblende or pyroxene, 
 one or more of which silicates occur as constituents of 
 granite, syenite, trap, porphyry, trachyte, and of beds of tufa 
 when first deposited, sets free silica to make opal or quartz ; 
 and in some tufas of California and Colorado the clustered 
 tree-trunks of a former forest, as well as scattered logs and 
 stumps, have been petrified by silica from such a source. 
 
 Pressure is requisite for most metamorphic changes. Lime- 
 stone heated without pressure loses its carbonic acid and 
 becomes quick-lime ; but if under pressure, as has been proved 
 by experiment, the carbonic acid is not driven off. The 
 needed pressure may be that of an ocean above ; it may be 
 that of the superincumbent rocks, and a few hundred feet 
 only would suffice. 
 
 The similarity of an argillaceous sandstone to gneiss or 
 granite is often much greater than appears to the eye. When 
 a sandstone has been made out of a gneiss, it may have the 
 quartz of the gneiss, and also its feldspar, in a pulverized 
 state, along with its mica ; so that the change produced in it 
 by metainorphism might be mainly a change in state of crys- 
 tallization. By simply heating a bar of steel, and cooling it 
 slowly or rapidly, it may be made coarse or fine steel, the 
 process changing the grains by causing the molecules of the 
 small grains to combine, to make large ones in the coarser 
 kind, and the reverse for the finer. There is something analo- 
 gous in the change, above described, of an argillaceous sand- 
 stone to gneiss or granite. It cannot be asserted, however, 
 that the feldspar grains in the sandstone would always re- 
 main feldspar; they may contribute to the making of mica 
 and a mica-schist, or to that of some other mineral and 
 rock. 
 
 Often, however, the material derived from the wear of 
 gneiss and granite and other rocks is not only pulverized, 
 but also more or less decomposed. The feldspar, for example, 
 may have lost its alkalies, or the mica its oxide of iron and 
 
150 DYNAMICAL GEOLOGY. 
 
 alkalies, and in such a case the process of metamorphism 
 could not, of course, restore the original rock. The new 
 rock made would contain no feldspar or mica, if the alkalies 
 had been wholly removed, but it might turn out an argillite or 
 slate ; or, if much oxide of iron is present, a hornblende rock, 
 or a chlorite rock, or some other kind from which the alka- 
 lies, potash and soda, are absent. 
 
 3. Local Metamorphism. Local metamorphism has often 
 taken place in the walls of dikes of igneous rocks, or in the 
 adjoining parts of the strata over or between which they have 
 flowed, in consequence of the heat from the melted and cool- 
 ing rock, and sometimes after cooling has ceased. Near 
 dikes of trap, the rock is sometimes made cellular by escap- 
 ing steam, and filled with shrinkage-fissures made on cooling 
 or drying ; and besides these effects, various minerals have 
 been often formed, as epidote, chlorite, hematite, tourmaline, 
 garnet, out of the ingredients present in the adjoining strati- 
 fied rock, or the trap, or both, which are true examples 
 of metamorphic results. The waters of mineral springs, es- 
 pecially when they are heated, have often produced meta- 
 morphic effects in the rocks, and many mineral species have 
 been formed by these means. Such cases of local metamor- 
 phism, as well as the facts stated on page 148, show that the 
 mineral changes which take place in regional metamorphism 
 are possible and natural results of the conditions that have 
 existed at such times. 
 
 4. Formation of Veins. 
 
 L Nature and origin of spaces occupied by Veins. Some of 
 the forms and characters of veins are shown and explained 
 on page 42. Veins are the fillings of spaces in the rocks ; 
 and these spaces are usually (1) the cracks or fissures made 
 by uplifting or disturbing forces ; (2) by the expansion or 
 pressure of vapors ; (3) by shrinkage from cooling or drying ; 
 they may be (4) the openings between the layers or lamina of 
 
FORMATION OF VEINS. .151 
 
 a rock produced in the flexing of the beds, like those between 
 the leaves of a quire of paper when folded over ; or (5) open 
 spaces made in rocks by excavation, as caverns are made. 
 
 The uplifting and flexing of rocks which have resulted in 
 fissures and openings are often accompaniments of meta- 
 morphic change, and the fissures may have become filled before 
 the long era of metaraorphism had passed. The heat con- 
 cerned in such a case may be, as explained above, that de- 
 rived from the movements in the strata in connection with 
 that of the earth's depths. 
 
 2. Materials of Veins. Quartz is the most common, be- 
 cause siliceous solutions are easily made, they requiring little 
 heat. Granitic material, requiring higher heat, is also com- 
 mon, but especially in veins intersecting the more crystalline 
 rocks ; and vein granite is usually much coarser in crys- 
 tallization than ordinary granite. Other stony materials, less 
 common, are calcite. bar tie (barium sulphate), and fluorite 
 (calcium fluoride) ; but where these occur, quartz may also 
 be present. Along with the earthy minerals may occur gold, 
 or the various ores of copper, lead, silver, and other metals, 
 besides pyrite (iron sulphide) which is almost universally 
 present in ore-bearing veins or lodes. The earthy minerals 
 are called the yangue of the ore. The ores are usually dis- 
 tributed in one or more planes parallel with the walls of the 
 vein (Figs. 19, 20, p. 42), but often very irregularly ; and the 
 veins may vary greatly in size, as illustrated in Fig. 17, and 
 have their ores only in their broader parts. 
 
 3. Origin of Dikes. Fractures that reach down to liquid 
 rock become filled by it, and thus dikes are formed (page 43), 
 which are not true veins, though sometimes so called. 
 
 4. Origin of Vein Deposits. The following are common 
 methods : 
 
 1. When thefssures or openings have not descended to liquid rock, 
 and were filed from either side or below. Vein deposits of this 
 kind are very common. They include nearly all those con- 
 sisting of quartz or granite, whether containing metallic 
 
152 DYNAMICAL GEOLOGY. 
 
 ores or not, and most banded mineral veins (page 42). The 
 fissures, or openings, and part of the heat are a result of pro- 
 found disturbances such as give rise also to metamorphisin. 
 The material of the vein is brought into the opening from 
 the rock adjoining, either that directly adjoining, or that of 
 depths below. The fissured rocks being heated, as above 
 stated, all moisture or vapor present tends to decompose the 
 rock-material near the fissure; it takes alkalies from the 
 feldspars, and so becomes siliceous, and few minerals will with- 
 stand its action. The vapors press into the fissures or open- 
 ings, carrying the mineral material they can dissolve, and 
 depositing it ; and they keep up supplying material until the 
 fissure is filled or the supply of material is exhausted. It is 
 natural that veins in gneiss and mica-schist filled in this way 
 should often be granitic veins, for these rocks contain the 
 quartz, feldspar, and mica of granite ; or, that they should 
 often be quartz veins simply, which they are likely to be if 
 the temperature is not high enough to make or dissolve feld- 
 spar and mica. 
 
 Under the action, whatever metallic ores, or constituents 
 of gems, the fissured rock contains, are carried into the fissure 
 with the other mineral material ; and additions may be re- 
 ceived largely through vapors rising from its deeper parts. 
 
 By such means veins have been supplied with their gems 
 and ores. The quartz veins and seams in the slate rocks of 
 a gold region have in this way become gold-bearing veins, the 
 gold and quartz having been brought in by the same moisture, 
 and both having been gathered from the adjoining or under- 
 lying rocks. These openings, in the case of auriferous quartz 
 veins, were often openings between layers of the slate made 
 in the folding or upturning. Quartz veins are the usual 
 original sources of gold ; and the gold-bearing gravels, which 
 afford the metal by simple washing, and have yielded the 
 larger part of the gold in use, are the detritus made out of the 
 gold-bearing rocks. The same gravels often afford platinum, 
 iridium, and diamonds. 
 
FORMATION OF VEINS. 153 
 
 While fissures filled by this lateral inflow of material, in 
 connection with emanations from the depths below, may be 
 uniform in material across, as in many quartz veins or seams, 
 they may also consist of bands of different minerals, like 
 many metallic veins (page 42). In the formation of banded 
 veins the process has brought in for a while one kind of 
 mineral, as quartz, and deposited it over the walls of the 
 fissure; then, through some change, some other mineral or 
 ore, as an ore of lead, or one of zinc, or one of copper ; then 
 quartz again, QT fluorite, or calcite ; and so on until the fissure 
 was filled. 
 
 The above is one of the methods by which the earth's 
 precious metals have been gathered out of the rocks, in which 
 they were sparingly disseminated, into generous veins, and 
 thereby placed within reach of the miner. 
 
 2. Where the fissures haw descended to regions of liquid rock and 
 were filled from below. (a) Dikes of porphyry, doleryte, and 
 related rocks are sometimes the courses of veins of metallic 
 ores. The veins are generally situated near the walls of 
 the dike, and either in the igneous rock or in the rock 
 adjoining. 
 
 The veins may have been made (1) when the dike was 
 made, or (2) they occupy fissures made subsequently, but 
 during the same epocli of disturbance, or (3) they have been 
 formed later, the old plane of fracture being a plane of weak- 
 ness liable to be opened anew. The metallic materials of the 
 vein have been brought up as solutions or vapors, either from 
 the depths that afforded the igneous rock itself, or, more 
 probably, from the walls of a deep part of the fissure. 
 
 The veins of native copper at Ke ween aw Point, those of 
 the same metal with ores of copper in the Eed sandstone 
 (Triassico-Jurassic) of the Connecticut Valley, New Jersey, 
 and Pennsylvania, those of silver ores in Nevada and other 
 mines along the Rocky Mountains and Andes, thus originated, 
 that is, in connection with igneous ejections ; the ores not 
 coming up as a constituent part of the igneous rock, but 
 
154 DYNAMICAL GEOLOGY. 
 
 mainly through the aid of vapors, and often those of subter- 
 ranean waters. 
 
 (b) Frequently in regions of igneous ejections fissures have 
 been made that have received not igneous rock, but only 
 vapors or mineral solutions from below, and thus have be- 
 come metallic veins. Each of the regions just mentioned 
 contains examples of such veins. 
 
 The filling may continue in progress long after the igneous 
 rock is cooled, or as long as heated vapors continue to rise 
 through the fissure. Shrinkage-cracks and openings made 
 by vapors in the rock adjoining the fissure may spread the 
 mineral depositions widely on either side. The vent may 
 continue as a source of heat to surface waters, making hot 
 mineral springs and steaming pools or basins, about or from 
 which depositions may take place of a vein-like character, as 
 is going on now in Nevada and California. 
 
 At Leadville, in Colorado, the ores of silver and lead occur 
 in veins and deposits beneath a stream or bed of igneous 
 rock ; and they probably came up from depths below through 
 the fissures which were opened at the time of eruption, but 
 which may have long given passage to hot vapors. The 
 original material in the depths below may have been chiefly a 
 silver-bearing galenite (lead sulphide) ; but through the heat 
 and vapors from those depths, and ingredients met with above, 
 they are now different ores of silver, along with silver-bearing 
 galenite, mixed with lead carbonate, lead sulphate, iron oxide, 
 and other minerals, and much disguised by the mixture. They 
 occur mostly in connection with a limestone that was greatly 
 eroded in the process. 
 
 3. Fissures or cavities filed by infiltration or deposition from 
 above. Wide cracks opening to the surface have sometimes 
 been filled with sand or earth, producing a kind of vein or 
 dike. Small cracks through rocks, shrinkage-cracks, and 
 others have often been filled with calcite by infiltration from 
 above, and sometimes by other minerals held in solution by 
 infiltrating waters. 
 
FORMATION OF VEINS. 155 
 
 Depositions of galenite or lead ore (with sometimes nickel 
 and zinc ores) have taken place in cavities or caverns in lime- 
 stones, as in Wisconsin, Illinois, and Missouri, and Cumber- 
 land and Derbyshire, England. The ore is often supposed to 
 be in veins, when, actually in local deposits that were made by 
 supplies from above. Yet they often have great extent, and 
 are a valuable source of ore, as in the American localities men- 
 tioned (as first deduced by J. D. Whitney), and probably in 
 many others. The condition of the ore-beds shows that when 
 the deposition was in progress, the limestone underwent much 
 erosion from acid solutions concerned in or resulting from the 
 changes. 
 
 Many cases of extensive bodies of ore in cavities in lime- 
 stone appear not to be of the above-mentioned kind, but to be 
 properly vein deposits. They may in some cases have origi- 
 nated in fissures which produced ore-deposits only where they 
 intersected limestones, because only limestones were easily 
 rendered cavernous by the eroding vapors so as to afford 
 spaces for the ores. 
 
 5. So-called veins that are not true veins. In the course of 
 the earth's rock-making, metallic ores have often been de- 
 posited along with the detritus when a sedimentary bed was in 
 progress of formation ; they have been brought into marshes, 
 or spread over confined sea-margins and mud-flats, by run- 
 ning waters which took up the metal (in some soluble state 
 of combination) from the decomposing rocks of the region 
 around. Deposits of iron ores are thus made at the present 
 time (page 85), and those also of zinc, cobalt, nickel, and 
 copper were so made in early geological ages. When strata 
 containing such metalliferous layers have undergone uplifts 
 and crystallization, the nearly vertical beds look like veins. 
 The great deposits in the Archaean terranes of hematite an 3 
 magnetite are beds, not veins or dikes. 
 
156 DYNAMICAL GEOLOGY. 
 
 i 
 
 V. MOVEMENTS IN THE EARTH'S CRUST: 
 THEIR CAUSES AND CONSEQUENCES. 
 
 As a preparation for the study of the following pages, it is 
 important that the subject of flexures, fractures, and displace- 
 ments, explained on pages 52-56, should be well understood, 
 and also that the facts, on pages 217 and 276-281, connected 
 with the making of the Green Mountains and Appalachians 
 should have been previously perused. 
 
 1. Explanations already given. In the preceding chapters 
 the origin of many geological phenomena, and of some of the 
 earth's features, have been briefly explained. 
 
 A. Changes of level have been described as caused (1) by 
 change of temperature, this cause producing the expansion 
 and contraction of rocks (p. 128); (2) by undermining due to 
 subterranean water (p. 102) ; (3) by undermining due to vol- 
 canic outflows (p. 139). 
 
 B. Mountain forms have been described as often a result of 
 the sculpturing of elevated plateaus of nearly horizontal rock 
 by streams, as exemplified among some of the most majestic 
 mountains of the globe (p. 95). 
 
 C. Folding of beds has been shown to have been caused 
 when they are clayey, soft, and wet, by a lateral movement 
 produced through the pressure of superincumbent material 
 (p. 106). 
 
 D. Fractures and faultings of strata have been attributed (1) 
 to undermining by different methods (pp. 102, 139); (2) to 
 contraction or expansion ; (3) to shrinkage on drying, pro- 
 ducing deep or shallow fractures (p. 129) ; (4) to the expan- 
 sive force of vapors (p. 135) ; (5) to the hydrostatic pressure 
 of a column of lava (p. 135) ; and to other causes. 
 
 E. Lamination parallel to the bedding, as in the shaly struc- 
 ture, has been explained as a possible result of the pressure 
 to which wet argillaceous beds have been subjected through 
 the weight of overlying strata. 
 
MOVEMENTS IN THE EARTH'S CRUST 157 
 
 F. Metamorphism has been described as produced on a small 
 scale, (1) in the vicinity of dikes of igneous rock, through the 
 heat of the rock when it was cooling from fusion, if vapors 
 or moisture were present to aid ; and (2) also in the neigh- 
 borhood of hot springs (p. 150). 
 
 G. Earthquakes have been stated to result from fractures of 
 rocks in subterranean regions, consequent (1) on undermining 
 (p. 102) ; or (2) on movements and fractures attending volcanic 
 action (p. 139). 
 
 But none of the causes that have been considered explain 
 the great changes of level involving large parts of continents 
 or of oceanic areas ; or the phenomena attending the making 
 and uplifting of mountains; or the widespread or regional 
 metamorphism that has turned simultaneously sedimentary 
 beds over thousands of square miles into crystalline rocks ; or 
 the earthquakes that have shaken a hemisphere. 
 
 2. Relation in size between the earth and its mountains. 
 On a globe twelve feet in diameter, the height of the earth's 1 
 loftiest mountains would be represented by an elevation of 
 about one twelfth of an inch ; the whole difference of level 
 between the deepest part of the oceanic basin and the highest 
 point of the land, by twice this amount ; and the mean depth 
 of the ocean, by a depression of one twentieth of an inch. The 
 deformation of the sphere produced in the making of the con- 
 tinents and mountains was, therefore, very small. 
 
 3. Facts as to changes in level that are explained by a change 
 in water-level. The subject of the origin of changes of level 
 is complicated by the fact that the base from which such 
 changes are measured is the water-plane of the ocean, and 
 this is far from constant, especially in the vicinity of the 
 continents. 
 
 (1.) The deepening of any part of the oceanic basin would 
 produce apparent elevation of the land ; and the thousand 
 feet of mean elevation of the land above the ocean has been 
 attributed to this cause. 
 
 (2.) The lifting of mountains on a continent, or the piling 
 
158 DYNAMICAL GEOLOGY. 
 
 of ice to mountain heights (as in a Glacial era), makes the 
 pendulum move some seconds of arc toward the high region, 
 and alters correspondingly the level of the adjoining ocean, 
 and thus draws the waters over the land, diminishing the 
 actual height of the mountains above the sea ; even a thou- 
 sand feet of height in the land causing a displacement in the 
 pendulum and level, as has been found in different regions, 
 of five or six seconds. 
 
 (3.) The accumulation of ice of great thickness about either 
 pole would change the level of the ocean from the pole to the 
 equator, and in proportion, approximately, to the sine of the 
 latitude ; it would cause a like displacement in the pen- 
 dulum and level, and hence diminish the slope southward of 
 the land of a continent, besides submerging to some extent 
 the coast regions. The same result would follow from an 
 increase in the solid material of the arctic area through detri- 
 tus from northward-flowing rivers. But there would be no 
 effect in either case provided the crust beneath subsided to 
 an equivalent amount. 
 
 (4.) A gradual retardation of the earth's rotation (such as 
 tidal friction tends to occasion) would diminish centrifugal 
 iction, and hence should lead to a diminution in the depth of 
 equatorial waters (involving an emergence of tropical land), 
 and to an increase in that of the polar, provided a sinking of 
 the tropical crust does not take place as a consequence of the 
 change. The fact that the great mountain chain of Western 
 America is lowest in a portion of its tropical part is the oppo- 
 site of that which the retardation alone should produce. 
 
 4. Facts as to changes in level that are not explained by 
 changes in water-level or the earth's attraction. Some of the 
 above causes have produced effects which the geologist has to 
 study out. But the grander changes of level are not thus 
 explained ; and if not the grander, then not the larger part of 
 the smaller. The raising of mountain ranges, with the accom- 
 panying upturning or flexing, faulting and metamorphism of 
 slrata, have some other explanation. The lifting of a marine 
 
MOVEMENTS IN THE EARTH'S CRUST. 159 
 
 formation as the Cretaceous, with the crust it rests on 
 ten thousand feet higher in the Eocky Mountains than on 
 the Atlantic border, is an example of a large class of facts to 
 be explained by some different method ; and so is the lifting 
 of the same beds along the whole length of the mountains 
 from Central America to the Arctic, but with maximum effect 
 within the area of the United States. The subsidence of great 
 areas, in some cases 10,000 to 40,000 feet, the maximum 
 exceeding the maximum depth of the ocean, during the 
 accumulation of beds for mountain-making, is another effect 
 of some different cause ; and so are pr'obably very many of 
 the gentle oscillations of level which have attended the depo- 
 sition of the successive strata of a formation, as those of the 
 Carboniferous age. 
 
 5. Bearing of facts as to the direction of action of the moun- 
 tain-making force. The characteristics of the force at work 
 in mountain-making are to be largely learned from the results 
 produced. The following are some of these results : 
 
 (1) It has placed the mountains mostly along the borders 
 of the continents ; (2) it has made the highest mountains on 
 the borders of the largest oceans ; (3) it has pressed up strata 
 many thousands of feet in thickness into great folds, some 
 exceeding 10,000 feet in height, and forced fold against fold, 
 in succession, over breadths of one or more hundred miles, 
 and along belts a thousand and more miles in length ; (4) it 
 has made more numerous and much steeper flexures, and 
 more metamorphism and igneous eruptions, on one side of a 
 mountain range than on the other, so that a mountain range 
 is a one-sided structure ; (5) it has often made the larger part 
 of the flexures correspondingly one-sided ; that is, with one 
 slope steeper than the other. 
 
 The points here enumerated are well illustrated on the 
 pages already referred to. Unequal-sided flexures are repre- 
 sented in the sections from Pennsylvania and Virginia on 
 page 279 ; and in the figures (by Prof. Lesley) on page 97, 
 which, although ideal, present actual facts from the up- 
 
160 DYNAMICAL GEOLOGY. 
 
 turned rocks of Pennsylvania. The ideal section on page 55 
 (Fig. 47) exemplifies the common fact as to crowded, steep 
 reversed folds on one or the other side of a mountain area of 
 steeply flexed rocks : as is well illustrated in the Appalachian 
 chain from Alabama to New England and beyond. 
 
 The following figure represents a vertical section of the 
 anthracite region between Neshquehoning Valley (on the 
 west, left in section,) and Mauch Chunk. (From the Keport 
 
 Fig. 120. 
 
 Section of the Panther Creek Anthracite basin at Nesquehoning tunnel (T). 
 
 of C. A. Ashburner of the Geological Survey of Pennsylvania 
 under Prof. Lesley.) The length is about 1,200 yards (the 
 scale of the figure being 1,000 feet to the inch). The flex- 
 ures to the west have their summits pushed westward 40 
 beyond the vertical. The folded rocks consist of beds of 
 anthracite and intervening strata of shale and sandstone ; 
 and the anthracite beds include the great " Mammoth bed " 
 (lettered at its outcrop E, E 1 , E 2 ) which is 13 to 27 feet thick, 
 and the bed F (outcropping at F 1 , F 2 , F 3 , F 4 , F 5 ) 11 to 20 feet 
 thick, besides one of 8 to 9 feet. The " Mammoth bed," is 
 doubled on itself at E 1 . 
 
 The facts thus far published sustain the conclusion that 
 the mountain ranges of the Appalachian chain, and the 
 most of the flexures of the included strata, are inequilateral. 
 The Eocky mountain region exhibits this feature in .having 
 
MOVEMENTS OF THE EARTH'S CRUST. 161 
 
 several great, nearly parallel, mountain ranges between its 
 summit and the Pacific among them, the Wahsatch Moun- 
 tains, the Humboldt ranges, the Sierra Nevada and Cascade 
 Kange, and the Coast Kange and almost nothing to corres- 
 pond on the eastern ; in having its areas of igneous rocks 
 confined almost wholly to the western slopes, with its great- 
 est line of volcanoes not far from the ocean's border ; and in 
 having metamorphic rocks widely distributed on the western 
 side, and sparingly on the eastern. 
 
 Thus it is proved that the force has in general acted 
 laterally, that is, from one side, as the pushing side, and 
 that it was, therefore, lateral pressure^ however it may have 
 been occasioned. It is to be noted that it has produced its 
 greatest effects along the borders of the continents over an 
 area one to eight hundred miles wide. It has made long 
 ranges, by simultaneous action, along the course of the pro- 
 gressing uplift, and has acted from nearly the same direction 
 in all the uplif tings of any region from Archaean time to the 
 present. 
 
 6. Bearing of known facts on the question as to the earth's 
 interior condition. From the great subsidences, like that 
 of 30,000 feet or more, which was a prelude to the making of 
 the Appalachians, it may be inferred that plastic rock exists 
 beneath, to be pushed aside so as to render subsidence pos- 
 sible. The great elevations have been explained only upon the 
 assumption of a flexible crust overlying something plastic. 
 
 The earth is believed to have slowly cooled from a state of 
 liquidity. It is urged by many physicists, though not by all, 
 that it has become solid throughout, as solid as steel or glass ; 
 the conclusion being based on the ground that if liquid within, 
 the crust would yield with the earth's rotation, and hence the 
 precession of the equinoxes arid the tides of the ocean would 
 be different in amount from what they actually are. It seems 
 to be evident that geological facts cannot be explained on the 
 basis of absolute solidity. There must have been in past 
 time, as many have urged, either a plastic layer between the 
 
 11 
 
162 DYNAMICAL GEOLOGY. 
 
 crust and a solid nucleus, or, at least, the remains of such 
 a plastic layer, wherever the great movements have taken 
 place. 
 
 But it is stated that if a plastic layer exists, and the crust 
 above it is thin, say twenty-five miles, the crust would 
 rest on the mobile sea underneath it like a floating mass, 
 the earth's surface being so nearly flat, and hence it would 
 be pressed down by any local addition to its weight, however 
 slight ; that it could not sustain mountain elevations, except 
 the lower part of the crust beneath the mountain were flexed 
 downward as the upper part was forced upward, so as to 
 leave a vacant space between, and thus make a float for the 
 mountain to stand on ; and it is held by some to be mathe- 
 matically demonstrated that a protuberance of the lower part 
 of the crust must necessarily accompany any elevation of the 
 upper part (Rev. O. Fisher). It lias been proved also that, 
 in the case of a crust of the small thickness stated, the force 
 from contraction and the gravity of the crust would be great 
 enough to produce all the inequalities of the earth's surface ; 
 but the same author reaches the conclusion that only a small 
 part of the actual inequalities could have resulted from its 
 action. 
 
 It seems to be evident that, with a crust so mobile as above 
 described, the lateral pressure generated within it could have 
 produced no long range of mountains, under one common 
 method of action ; nothing of that uniformity of results ex- 
 hibited in many great regions from Archaean time onward ; 
 no mountain borders for the continents ; no general system 
 of feature lines for the globe. 
 
 The facts would appear, therefore, to prove that the crust 
 must exceed twenty-five miles in thickness ; must be thick 
 enough to have in some degree the virtues of an arch, and yet 
 not so thick that flexures and displacements, und.er the condi- 
 tions existing, were impossible. The demands of physical 
 science as to a solid globe may perhaps be met by assuming 
 that whatever the condition of the plastic layer underneath 
 
MOVEMENTS OF THE EARTH'S CRUST. 163 
 
 the crust in past time, only the remains of it now exist, the 
 part of it beneath the oceans and the interiors of continents 
 having largely disappeared by solidification. 
 
 I. Evolution of the Earth's Fundamental Features. 
 
 Although it is not proved that lateral pressure or thrust in 
 the crust, resulting from slow cooling, was actually the chief 
 source of the movements in mountain-making, no other theory 
 of mountain-making has been substituted by those who reject 
 it. Having, consequently, no new theory to present, that 
 based on contraction from cooling is here explained. 
 
 The following have been set forth as the different steps in 
 the evolution of the earth's features. They correspond with 
 the fact that all changes in the progressing earth went for- 
 ward under a simple, comprehensive method of development. 
 
 1. The Mountain-borders of the Continents, highest and most 
 abounding in volcanoes on the sides of the largest Ocean. 
 The oceanic area, besides being much depressed below the 
 continental, has rather abrupt sides to the true oceanic basin, 
 as explained on page 12. The lateral pressure in the crust 
 being universal over the sphere, the force in the oceanic crust 
 would hence have acted obliquely upward against the crust 
 of the continental border. The action was that of a shove 
 or thrust from the direction of the ocean, and in each oceanic 
 area was somewhat proportional to its extent ; consequently, 
 bendings, uplifts, fractures, foldings of strata, earthquakes, 
 mountain-making, became eminently features of the conti- 
 nental borders, and most prominently so of the borders which 
 faced the largest oceans. 
 
 2. Method of action, and its progress in North America. 
 The two systems of forces engaged in the progress of North 
 America were those from the direction of the Atlantic and 
 the Pacific basins the latter the greatest. Under their 
 action the V-shaped Archsean dry land (map, page 199) was 
 
164 DYNAMICAL GEOLOGY. 
 
 first defined, one branch stretching northeastward to Labra- 
 dor and the other northwestward to the arctic seas, and thus 
 facing respectively the Atlantic and Pacific areas, while moun- 
 tains were made along the course of the Appalachian chain 
 and the Blue and Highland ridges. It follows, from the 
 courses of the arms of the V, and of the mountains, that the 
 Atlantic force acted mainly from the southeastward, and 
 the Pacific from the southwestward, and the two, therefore, 
 nearly at right angles to one another. It is also apparent 
 that the Pacific force even then was the greater, and hence 
 the Pacific Ocean the larger ; for the northwestward branch 
 of the V is far the longer. 
 
 Thus the Archaean nucleus was outlined, and the position 
 of Hudson's Bay determined within the arms of the V- From 
 this nucleal dry land progress went forward southeastward, 
 or toward the Atlantic, and southwestward, or toward the 
 Pacific, successive formations being added under gentle oscil- 
 lations, and the dry land gradually extending under changes 
 of level caused mainly by the same forces. Then, when the 
 Lower Silurian closed, appeared the Green Mountains ; and 
 when Paleozoic time was closing, appeared the Alleghany 
 part of the Appalachian chain, parallel to the eastern branch 
 of the Archaean heights. Later still rose the trap ridges of 
 the Mesozoic on the Atlantic border (p. 286 ), making an- 
 other parallel to the eastern branch, or tripling the arm of the 
 V on the east, and even repeating all the bends in the 
 Appalachians. 
 
 Again, on the Pacific side, other ranges were made, parallel 
 to the course of the Eocky Mountain chain ; among them 
 after tlge Jurassic period, the Sierra Nevada, and, after the 
 Cretaceous, the Wahsatch, and still later, Tertiary ridges 
 toward the coast, each epoch adding new parallels to the 
 western branch of the Archaean nucleus. Finally, in the 
 course of the Tertiary, the mass of the Eocky Mountains 
 rose to its full height above the ocean. 
 
 Each added range, as is seen, proves that the mountain- 
 
MOVEMENTS OF THE EAKTH'S CRUST. 165 
 
 making forces continued to act to a large degree from the 
 same directions as in Archaean time. 
 
 Thus, the continent made progress, adding layer after layer 
 to the rocks over its surface, and range after range in parallel 
 lines to its heights, until finally the continental area reached 
 its limit, and the great interior basin had its mountain-bor- 
 ders completed : on the east, the low Appalachians, and the 
 trap ridges of the Mesozoic ; on the west, the massive and lofty 
 Rocky Mountain chain, with the parallel ranges over its 
 western slopes. 
 
 It is explained beyond (on page 373) that, when the con- 
 tinent was thus far completed, there occurred a change in 
 the region of progress. The high-latitude operations of the 
 Quaternary then began. 
 
 On this view, the evolution of the features of the surface 
 went forward through one system of forces originating in oue 
 single cause, the earth's contraction from cooling. North 
 America, which is here appealed to for explanations, affords the 
 truest and clearest illustration of the principles involved in 
 the system of evolution, because it lies alone between the two 
 oceans, the Atlantic and Pacific, with the nearest continent, 
 South America, to the east of its meridians. The progress on 
 this account went forward with great regularity, each age 
 repeating the preceding in the direction of all oscillations or 
 uplifts. It was a single isolated individual making system- 
 atic progress throughout until its final completion, and exhibits 
 truly the system in the earth's development, whatever the 
 true theory of that development. Europe, in contrast, has 
 Africa on the south and Asia on the east ; it is, therefore, full 
 of complexities in its feature lines, and in the succession of 
 events that make up its geological history. 
 
 2. Formation of Mountain Chains. 
 
 1. A Geosyncline, or downward bend of the Crust, the first 
 step in ordinary Mountain-making. In the making of the 
 
166 DYNAMICAL GEOLOGY. 
 
 Appalachians there was first a slowly progressing subsidence ; 
 it began in, or before, the Cambrian or Primordial period, and 
 continued in progress until the Carboniferous age closed. As 
 the trough deepened, deposits of sediment, and sometimes of 
 limestone, were made, that kept the surface of the region near 
 the water level ; and, when the trough reached its maximum, 
 there were at least 30,000 feet in thickness of stratified rock 
 in it (page 277), and this, therefore, was the depth of the 
 trough. The Green Mountains began in a similar subsidence, 
 and at the same time; and the trough was kept full with 
 deposits as it progressed ; but it reached its maximum, or the 
 era of catastrophe, at the close of the Lower Silurian. Such 
 facts are in the history of many, if not all, mountains. 
 
 2, The bottom of the Geosyncline weakened by the Heat rising 
 into it from below. As planes of equal temperature within 
 the earth have a nearly uniform distance from the surface, the 
 accumulation of sedimentary beds in a sinking trough would 
 occasion, as Herschel long since urged, the corresponding 
 rising of heat from below, so that, with 30,000 feet of such 
 accumulations, a given isothermal plane would have been 
 raised 30,000 feet. Under such an accession of heat, the 
 bottom of the trough would have been greatly weakened, if 
 not partly melted off. If the lower surface of the crust had 
 dipped down this much into the plastic material that was 
 beneath it, it would have been actually melted off. The 
 lateral pressure, acting against a trough thus weakened, 
 would end, as has been suggested, in causing a collapse, that 
 is, a catastrophic break of the trough below, and a pressing 
 together of the stratified beds within it. And with this break 
 the shaping of the mountain would begin. 
 
 3. Character of the Mountain thus made. Under such cir- 
 cumstances the stratified rocks lying in the geosyncline or 
 trough would be folded, profoundly broken, shoved along 
 fractures, and pressed into a narrower space than they occu- 
 pied before. The crust beneath was that of the geosyncline ; 
 and lateral pressure, however powerful, could not possibly 
 
MOVEMENTS OF THE EARTH'S CRUST. 167 
 
 have given an upward bend at the time to the downward 
 Hexed crust. The flexures were flexures in the overlying 
 strata ; they were too small to have been made also in the 
 thick crust on which the strata lay (p. 160). They became 
 unequal-sided, as represented on page 279, and the mountain 
 itself inequilateral (p. 159), because there was a pushing 
 side in the mountain-making, the force coming mainly from 
 one direction (the oceanic, in the case of the Appalachians). 
 Faults of 10,000 to 20,000 feet were among the effects, be- 
 cause the crust was under the vast pressure, and could 
 break in oblique planes, where it could not bend ; and be- 
 cause after breaking, it would continue to yield and thus be 
 shoved up or down along the plane of fracture. Such a 
 mountain range, begun in a geosyncline and ending in a 
 catastrophe of displacement and upturning, has been named 
 a synclinore, it owing its origin to the progress of a geosyn- 
 cline. (The word is from the Greek for syncline, and opos, 
 mountain.) 
 
 On the side away from the chief source of movement, and 
 beyond the profoundest faults, the elevations that have taken 
 place have commonly made vast plateaus of nearly horizontal 
 beds, like the Cumberland mountain region of Tennessee and 
 its continuation through western and northern Pennsylvania, 
 to the Catskill Mountain plateau of southern New York, on 
 the outskirts of the Appalachian range ; and the Uintah 
 Mountain plateau and others of southern Utah, on the out- 
 skirts of the Wahsatch range. In such elevated areas, several 
 thousands of feet above the sea level, and of wide extent, 
 running waters have had their opportunity for sculpturing, 
 and have thus made some of the most majestic mountain 
 groups of ridges and peaks in the world. In Tennessee, the 
 region of great folds and faults directly east of the Cum- 
 berland plateau was at first, beyond doubt, of far greater 
 height than the plateau ; but owing to the vast amount of 
 fracturing as well as the steep slopes, denudation has finally 
 made it lower, and it is now the "Valley of East Tennessee," 
 
168 DYNAMICAL GEOLOGY. 
 
 while the plateau is " Cumberland Mountain." Not less was 
 the denudation in front of the Catskill plateau. 
 
 4. A Mountain Chain may comprise ranges of different epochs 
 of origin. The Appalachian chain consists of (1) mountains 
 of Archaean age ; (2) the Green Mountains, that date from 
 the close of the Lower Silurian; and (3) the Alleghanies, 
 that were formed at the close of the Carboniferous age. The 
 Green Mountains began in the same great geosyncline with 
 the Alleghanies ; but that part reached its completion first, 
 probably because so near the stable Adirondack border of 
 the continent. It is probable that the Archaean portion of the 
 Appalachian chain which includes the Blue Kidge, the 
 New Jersey Highlands, continued in Putnam County, N. Y., 
 some areas in western New England, and the Adirondacks, 
 corresponds to another older synclinoro. Thus a mountain 
 chain may comprise several ranges, made at widely different 
 epochs. 
 
 5. Metamorphism and other attendant effects. The heat 
 developed through the transformation of motion, added to 
 that rising into the strata from below, would produce all the 
 consolidation and crystallization that is, all the metamor- 
 phism which has been in any case observed, and on a scale 
 as vast as that of the mountain range so developed. It gives 
 a full explanation, therefore, of the origin of regional meta- 
 morphism. 
 
 The heat might be sufficient in some parts to reduce a rock 
 to a plastic state, and so obliterate all its original bedding. 
 One result of this would be to make a massive metamorphic 
 rock, like granite, in place of gneiss or other schistose kind ; 
 and another result, if the overlying rocks were fractured, and 
 so fissures opened down to the plastic rock, would be to fill 
 the fissures with the plastic rock, making dike-like veins of 
 granite, or of other material, according to the kind of rock so 
 fused. It might possibly give a long core, or central mass, 
 of granite to a mountain-range, a condition of the Sierra 
 Nevada which has been attributed by some to this cause. 
 
MOVEMENTS OF THE EARTH'S CRUST. 169 
 
 6. Slaty cleavage, jointed structure. Slaty cleavar/e has 
 been proved by experiments to result whenever fine-grained 
 rock-material is subjected to pressure ; and to be due to the 
 flattening of all air-cells and compressible particles, and 
 the arranging of all flat grains in planes at right angles to 
 the pressure. As it occurs in upturned or flexed rocks of fine 
 grain, the pressure producing upturning or flexure, and also 
 mountain-making, has been generally the cause. It conforms 
 to the bedding whenever the bedding is, as a consequence of 
 the upturning, at right angles, or nearly so, to the pressure. 
 
 A jointed structure, on the large scale observed in many 
 regions, has been another result of the slow uplifting or flex- 
 ing action from lateral pressure. The strain, after accumu- 
 lating through a long period, has ended in fractures of great 
 depth, evenness, and general parallelism, at right angles to 
 the direction of the pressure, and often also in a subordinate 
 system of fractures transverse to it ; sometimes also when 
 a warping of the beds was likewise in progress in joints 
 that were not parallel. Slowly accumulating pressure from 
 any other source would produce like results. 
 
 In many quartzose sandstones the grains are so loosely 
 coherent that the vibrations attending any upturning and 
 fracturing tend to shake out all traces of the original bedding. 
 At the same time, the lateral pressure produces planes of 
 apparent bedding and division at right angles to its direction, 
 - partly as a result of the strain attending the movements, 
 and partly owing directly to the pressure, as in slaty cleavage. 
 Hence quartzytes, which are metamorphic sandstones, seldom 
 retain their true bedding, but have nearly vertical divisional 
 planes instead. 
 
 ?. Geanticlines in Mountain-making. In the movements of 
 the earth's crust, there would necessarily be upward as well 
 as downward flexures, that is, geanticlines as well as geo- 
 synclines. The Appalachians, as explained a.bove, may, when 
 first made, have stood up in ridges, without having under- 
 gone any uplifting from an elevation of the crust underneath. 
 
170 DYNAMICAL GEOLOGY. 
 
 But, however this may be, the region actually experienced 
 elevation before the Triassic period opened, as is proved by 
 the position of the Triassic beds ; and this took place prob- 
 ably through a gentle, upward bending of the crust, such a 
 bending becoming possible after (although not before) the 
 region of the Appalachians had been made a portion of the 
 stable part of the continent. 
 
 The Eocky Mountains, in the Cretaceous era, within the 
 area of the United States, were 10,000 feet below their 
 present level, the sea covering them (p. 323). They were 
 raised as a whole during the Tertiary, and it must have been 
 through a low geanticline. While the Tertiary mountains 
 were in progress, the part of the force not expended in 
 producing them appears to have carried forward an upward 
 bend, or geanticline, of the vast Rocky Mountain region as 
 .a whole. 
 
 After the crust had become thickened by the earth's inter- 
 nal cooling, through the ages, and had been stiffened also by 
 the plication and solidification, and partly the crystallization, 
 of the strata, geosynclinal troughs over the continents, like that 
 of the Appalachian region, became less a possibility ; and con- 
 sequently the chief movement caused by the ever-continuing 
 lateral pressure would have been an upward one. It may be 
 for this reason that the mountain-chains received their great 
 height so largely in the Tertiary ; and that the areas over the 
 earth's surface that were affected by single movements, such 
 as the high-latitude movements of the Quaternary, were so 
 vast. There was, also, in the Quaternary, if Darwin's view as 
 to the formation of coral atolls (that presented on page 78) is 
 right, 1 a downward bending through the warm parts of the 
 
 1 Darwin's theory explains completely the observed facts with regard to 
 coral formations. But it assumes the fact of a great oceanic subsidence, which 
 has not been independently proved. It has been suggested that shells of 
 Rhizopods and the stony secretions of other forms of marine life may have 
 built up portions of the sea-bottom to within 100 or 120 feet of the surface - 
 the depth at which reef-corals can grow and that only the upper 120 feet 
 consist of coraJ-reef rock ; and, in order to account for the open interior, 
 
MOVEMENTS OF THE EARTH'S CRUST. 171 
 
 oceans, the coral island subsidence, affecting an area in 
 the Pacific over 5,000 miles in its longer diameter; an extent 
 far beyond that of the mountain-making geosynclines of 
 earlier time. It may be that the Pacific coral-island subsid- 
 ence was the counterpart of the geauticlinal movement over 
 the continents of the later Tertiary and early Quaternary. 
 
 8. Fractures and outflows of igneous rocks most numerous 
 in later geological times. Great floods of doleryte and trachyte 
 were poured out over the Kocky Mountain slope, after the 
 close of the Cretaceous period. The previous plications and 
 solidifications of the strata involved in the making of the 
 various ranges of mountains would have left the crust firm 
 and unyielding ; and, being too stiff to bend, it broke, and 
 hence the eruptions. It had broken at times before ; but at 
 this time the fractures became much more numerous, and the 
 floods of rock more extensive. Moreover, from this era ap- 
 pears to date the opening of the great volcanoes of the Cascade 
 range. In fact, the larger part of the volcanic eruptions of 
 the world are probably, for a like reason, of Tertiary and later 
 origin. 
 
 Such are the general steps of progress, and their explana- 
 tions, according to that theory of mountain-making which 
 attributes the movement to a lateral thrust in the earth's crust 
 
 or lagoon, of the coral island, it is further supposed that the structures were 
 begun on the rims of submarine craters. 
 
 The objections to this theory are : (1) that the existence of craters in the 
 lava accumulations made by submarine volcanic action is improbable ; (2) that 
 no craters of known volcanoes have even approximately the size of many of 
 the lagoons of atolls ; (3) that the lagoons are never circular, but as irregular 
 in outline, nearly, as the other islands of the ocean ; (4) that in the Feejee 
 group all the steps in the progress of an atoll assumed in the Darwinian 
 theory are exemplified, from the high volcanic island with a fringing reef, to 
 the atoll, 15 miles in diameter, having two small peaks of volcanic rocks in 
 the great lagoon. (See map of the Feejee group in the author's " Corals and 
 Coral Islands," 378 pp. 8vo, New York.) A few borings in a coral island to 
 a depth of 500 or 1,000 feet, with a drill large enough to give a core six inches 
 in diameter for examination, would settle the question as to whether the rock 
 below is of coral-reef origin or not. 
 
172 DYNAMICAL GEOLOGY. 
 
 
 
 as a result of contraction on cooling. The universality of 
 system in the features of continents and the characters of 
 mountains has as yet no other probable explanation. Specu- 
 lation has appealed to the power of crystallization as a 
 determining cause for at least the direction of the grand 
 feature lines. But of this there is too much uncertainty for 
 any confidence in the view. 
 
 To obtain an adequate idea of the slow progress of the earth 
 in the making of its mountains, it is necessary to remember 
 that the process has gone on only after immensely long 
 periods of quiet and gentle oscillations. After the beginning 
 of the Cambrian, the first period of disturbance in North 
 America of special note was that at the close of the Lower 
 Silurian, in which the Green Mountains were finished ; and 
 if time, from the beginning of the Silurian to the present, in- 
 cluded only 48 millions of years, (p. 375) the interval between 
 the beginning of the Cambrian and the uplifts and metamor- 
 phism -of the Green Mountains was at least 20 millions of 
 years. Another epoch of disturbance was that at the close of 
 the Carboniferous era, in which the rocks of the Alleghanies 
 were folded up ; on the above estimate of the length of time, 
 it occurred about thirty-six millions of years after the com- 
 mencement of the Silurian ; so that the Alleghanies were at 
 least 36 millions of years in making, the preparatory subsi- 
 dence having begun as early as the beginning of the Silurian, 
 The next on the Atlantic border was that of the displace- 
 ments of the Triassico-Jurassic sandstone and the accompany- 
 ing igneous ejections, which occurred before the Cretaceous 
 Pra? a t least five millions of years, on the above estimate of 
 the length of time, after the Appalachian revolution. Thus, 
 whatever the mountain-making force, an exceedingly long 
 time was required in order to accumulate a sufficient amount 
 to produce a general yielding and plication or displacement 
 of the beds, and start off a new range of prominent elevations 
 over the earth's crust. 
 
ANIMAL AND VEGETABLE KINGDOMS. 173 
 
 REVIEW OP THE ANIMAL AND VEGETABLE 
 KINGDOMS. 
 
 THE following pages on the Animal and Vegetable King- 
 doms are inserted in this place to prepare the student 
 for the following portion of the work, on Historical Geology, 
 in which the progress of life is a prominent part. 
 
 Distinctions between an Animal and a Plant. 
 
 1. An Animal, An animal is a living being, sustained by 
 nutriment taken into an internal cavity or stomach, through 
 an opening called the mouth. It is capable of perceiving the 
 existence of other objects, through one or more senses. It 
 has (except in some of the lowest species) a head, which is 
 the chief seat of the power of voluntary motion, and which 
 contains the mouth. It is fundamentally a fore-and-aft 
 structure, the head being the anterior extremity, and it is 
 typically forward-moving. With its growth from the germ, 
 there is an increase in mechanical power until the adult size 
 is reached. In the processes of respiration and growth, it 
 gives out carbonic acid and uses oxygen. 
 
 2. A Plant. A plant is a living being sustained by nutri- 
 ment taken up externally by leaves and roots. It is inca- 
 pable of perception, having no senses. It has no head, no 
 power of voluntary motion, no mouth. It is fundamentally 
 an up-and-down structure, and, with few exceptions, fixed. 
 In its growth from the germ or seed, there is no increasing 
 mechanical power. In the process of growth, it gives out 
 oxygen and uses carbonic acid. 
 
174 ANIMAL KINGDOM. 
 
 I. Animal Kingdom. 
 I. The Animal Structure. 
 
 The nature of an animal requires, for a full exhibition of 
 its powers, the following parts : 
 
 1. A stomach and its appendages to turn the food into 
 blood, with an arrangement for carrying off refuse material. 
 
 2. A system of vessels for carrying this blood throughout 
 the body, so as to promote growth and a renewal of the 
 structure. 
 
 3. A heart, or forcing-pump, to send the blood through the 
 vessels. 
 
 4. A means of respiration, or of taking air into the system 
 (as by lungs or gills), because this growth and renewal re- 
 quire the oxygen of the air to act in conjunction with the 
 blood, as much as a fire requires air in order that the fuel 
 may burn. 
 
 5. Muscles, or contractile fibres, to act by contraction and 
 relaxation in putting the parts or members in motion. 
 
 6. A brain, or head-mass of nervous matter, and a system 
 of nerves, branching through the body, to serve as a seat 
 for the will and for the power of sensation and motion, and 
 to convey the determinations of the will and sensation 
 through the body. 
 
 In the lowest form of animal life, as some microscopic 
 Protozoans, the stomach is not a permanent cavity, but is 
 formed in the mass of the tissue whenever a particle of food 
 comes in contact with the body. In other words, a stomach 
 is extemporized as it is needed. In species of a little higher 
 grade, as Polyps, there is a mouth and stomach, with mus- 
 cles, an imperfect system of nerves when any, and a means 
 of respiration through the general surface of the body; but 
 there is no distinct heart, and the animal is ordinarily fixed 
 to a support. 
 
ANIMAL KINGDOM. 175 
 
 2. Subdivisions of the Animal Kingdom. 
 
 Animals (with the exception of some inferior species for- 
 merly referred to the Articulates and of little geological 
 importance) have been divided into five groups, called sub- 
 kingdoms. These five sub-kingdoms are the following : 
 
 7. The Vertebrate: having (as in Man, Quadrupeds, Birds, 
 Reptiles, and Fishes) an internal jointed skeleton, of which 
 the backbone is called the vertebral column, and each of its 
 joints a vertebra ; and a bone-sheathed cavity along the back 
 for the great nervous chord. 
 
 The remaining sub-kingdoms have no vertebral skeleton and 
 are called Invertebrates. 
 
 2. The Articulate: having (as in Insects, Spiders, Crabs, 
 Lobsters, Worms) the body and its appendages (as the legs, 
 etc.) articulated, that is, made up of a series of joints. 
 
 3. The Molluscan: having (as in the Oyster, Clam, Snail, 
 Cuttle-fish) a soft, fleshy body without articulations or joints, 
 and without a radiated structure ; and the appendages, when 
 any exist, also without joints. The name is from the Latin 
 moUis, soft. 
 
 4. The Radiate: having (as in the Polyp, Medusa, Sea- 
 urchin, Star-fish) the body, both externally and internally, 
 radiate in arrangement, that is, having similar parts or organs 
 repeated around a vertical axis, as in a flower the parts are 
 radiately arranged about its centre or central axis. 
 
 Those Radiates which have the mouth the only opening to 
 the digestive cavity are called Coelenterates, from the Greek 
 for hoUoiu within. They include all Polyps, together with the 
 Medusae and other Acalephs (p. 184). 
 
 5. The Protozoan. Besides the above, there are other spe- 
 cies of so extreme simplicity that neither of the systems of 
 structure above mentioned is apparent in them, and these are, 
 therefore, in a sense systemless animals. Many have not even 
 a mouth. They include the Sponges, and also a large number 
 of minute species, visible only with the aid of a microscope. 
 
176 ANIMAL KINGDOM. 
 
 1. Sub-kingdom of Vertebrates^ 
 
 Class 1. Mammals. Warm-blooded animals that suckle 
 their young, as Man, Quadrupeds, Whales. Nearly all are 
 viviparous; a few (as the Opossum and other Marsupials] 
 are semi-oviparous, the young at birth being very immature, 
 and being therefore taken into a pouch (in Latin marsupium 
 signifies pouch) where they draw nutriment from the mother 
 until matured. 
 
 Class 2. Birds. Warm-blooded air-breathing animals, 
 oviparous, having a covering of feathers, and the anterior 
 limbs more or less perfect wings. 
 
 Class 3. Reptiles. Cold-blooded air-breathing animals, 
 oviparous, having a covering of scales or simply a naked skin 
 (as Crocodiles, Lizards, Turtles, Snakes) ; they breathe with 
 lungs (or are air-breathing) when young as well as after- 
 ward, being, in this respect, like birds and quadrupeds. 
 
 Class 4- Amphibians (as Frogs and Salamanders), which 
 differ from true Eeptiles in breathing by means of gills when 
 young, and afterward becoming air-breathing, the animal un- 
 dergoing, thus, a metamorphosis. 
 
 Class 5. Fishes. Cold-blooded oviparous animals, breath- 
 ing by means of gills, and having a covering of scales or simply 
 a naked skin. Among fishes : - 
 
 1. Teliosts (as the Perch, Salmon, and all common fishes) 
 have the scales usually membranous, the skeleton bony, and 
 the gills attached at only one margin. 
 
 The name is from the Greek reXeto? perfect, and ba-reov, 
 lone, alluding to the skeleton being all of it bony. 
 
 The scales in many are toothed or set with spines about 
 the inner margin (Fig. 125), wliile others have the margin 
 smooth (Fig. 124). Fishes having scales of the former kind, 
 as the Perch, have been called Ctenoids by Agassiz (from the 
 Greek /cre/9, comb) ; and those having scales of the latter 
 kind, as the Salmon, etc., Cycloids (from the Greek /cvtcXos, 
 circle). 
 
 2. Ganoids (as the Gar-pike and Sturgeon), having the 
 
VERTEBRATES. 
 
 Ill 
 
 scales bony and usually shining, and the skeleton often car- 
 tilaginous. The name is from the Greek ydvos, shining. 
 
 Fig. 120 represents one of the ancient Ganoids. The verte- 
 bral column extends to the extremity of the tail, so that the 
 tail-fin is vertcbratcd, while, in modern Gars and Teliosts, the 
 
 Fig. 120. 
 
 Palaeoniscus Freieslebeni ( x 
 
 vertebral column stops at the commencement of the tail, or 
 the tail-fin is non-vertebrate (Fig. 121). Agassiz called the 
 
 Figs. 121-129. 
 126. 
 
 GANOIDS (excepting 124, 125). Fig. 121, Tail of Thrissops (X ) ; 122, Scales of Cheiro- 
 lepis Traillii (X 12); 123 Palseoniscus lepidurus (X 6) ; 123, a, under-view of same ; 124, 
 scale of a Cycloid ; 125, id. of a Ctenoid ; 126, Part of pavement-teeth of Gyrodus 
 umbilicus ; 127, Tooth of Lepidosteus ; 128, id. of a Cricodus ; 129, Section of tooth of 
 Lepidosteus osseus. 
 
 former kind heterocercal, and the latter homocercal. The scales 
 are either rhombic, as in Figs. 121, or rounded. Some of 
 these rhombic bony scales are shown also in Figs. 122, 123. 
 The teeth (Figs. 127, 128) often have a folded or laby- 
 
 12 
 
178 
 
 ANIMAL KINGDOM. 
 
 rinthine texture within, as in Fig. 129, representing a part of 
 a section of a tooth enlarged. In one group, the Ganoids 
 have a pavement of teeth in the mouth, as in Fig. 126. 
 
 3. Selachians (as the Sharks and Rays), having a hard skin, 
 called sJiagreen, often rough with minute points, the skeleton 
 
 SELACHIANS. Fig. 130, Spinax Blainvillii (X i) ; 131, Spine of anterior dorsal fin, 
 natural size ; 132, Cestradon Philippi (x I) ; 133, Tooth of Lamna elegans ; 134, Tooth 
 of Carcharodon angustidens ; 135, Notidanus primigenius ; 136, Hybodus minor ; 137, 
 Hyb. plicatilis ; 138, Mouth of a Cestracion, showing pavement-teeth of lower jaw; 139, 
 Tooth of xVcrodus minimus ; 140, Tooth of Acrodus nobilis. 
 
 more or less completely cartilaginous, and the gills attached 
 by both margins. The name is from the Greek creXa^o?, car- 
 tilage. 
 
 Fig. 130 represents, much reduced, one of the order (a Spi- 
 nax), having the mouth, as usual, on the under surface of the 
 
ARTICULATES. 179 
 
 head and remarkable for the spine before each of the back 
 fins : one of the spines is shown, natural size, in Fig. 131. 
 Fig. 132 is an outline of another Selachian, of the genus Ces- 
 tracion, living in the vicinity of Australia, peculiar in having 
 the mouth at the extremity of the head, and also in the teeth 
 of the mouth having, in part, the form and appearance of a 
 pavement, as shown in Fig. 138. Figs. 133 to 137 are teeth 
 of different Selachians related to the Sharks; and Figs. 139, 
 140, pavement-teeth of Cestraciont species. The Cestraciont 
 Selachians were once very common, but the tribe is now 
 nearly extinct. 
 
 2. Sub-kingdom of Articulates. 
 
 Among Articulates there are three classes; one, including 
 the species adapted to live on land, and which, for this pur- 
 pose, breathe by means of air-vessels branching through the 
 body ; and two, of species adapted to live in water, and, 
 therefore, having gills. 
 
 7. Land Articulates, or the class of INSECTEANS. There are 
 three orders or grand divisions of Insecteans, namely : 1. In- 
 sects ; 2. Spiders ; 3. Myriapods (or Centipedes). 
 
 2. Water Articulates, including the two classes 1. CRUS- 
 TACEANS (as Crabs, Lobsters, etc.), and 2. WORMS. 
 
 CRUSTACEANS. 
 
 A knowledge of the principal subdivisions of Crustaceans 
 is especially important to the student in geology. There are 
 three orders : 
 
 1. The Decapods, or IQ-footcd species, as the Crab (Fig. 142), 
 Lobster, Shrimp. 
 
 2. The Tetradecapods, or 14-footed species, as the Sow-bay 
 (Fig. 143), found in damp places under logs, the Sand-flea in 
 the sands, or cast-up sea-weed of a beach (Fig. 144), etc. 
 
 3. The Entomostracans, or inferior species, having the feet 
 defective, as the Cyclops and related species (Figs. 146, 147)> 
 Daphnia, Limulus or Horse-shoe, and the Cypris and other 
 
180 
 
 ANIMAL KINGDOM. 
 
 Ostracoids (Fig. 149). These Ostracoids are generally minute 
 species, having a shell like that of a bivalve Mollusk, as Fig. 
 104 shows ; but inside of the shell, instead of an animal like a 
 
 Figs. 141-150. 
 
 ARTICULATES. 1. Worms: 141, Arenicola piscatorum, or Lob-worm (x J)- 2 - Crusts 
 ceans : 142, Crab, species of Cancer ; 143, au Isopod, species of Porcellio ; 144, an Amphi- 
 pod, species of Orchestia ; 145, an Isopod, species of Scrolls (x 2) ; 146, 147, Sapphirina 
 Iris, 146, female, 147, male (x 6) ; 148, Trilobite, Calymeue Blnmenbachii ; 149, Cythere 
 Americana, of the Ostracoid family (X 12) ; 150, Anatifa, of the Cirriped tribe. 
 
 clam, there is one more like a shrimp, with jointed legs. The 
 name is from the Greek ocrrpafcov, shell, the word from which 
 oyster is derived. 
 
 Among JSntomostracans, there are also the Barnacles and 
 other Cirripeds, one of which is represented in Fig. 150. 
 
 Trilobites (Fig. 148) are related to the Limulus or " Horse- 
 shoe" among the' lower Crustaceans. The tribe is inter-- 
 mediate in some points between Crustaceans and Scorpions, 
 It is now extinct. 
 
 3 Sub-kingdom of Mollusks. 
 
 There are three grand divisions or classes of Mollusks : 
 
 1. Ordinary Mollusks, as the Clam, Snail, and Cuttle-fish, 
 which have branchiae (gills). 
 
 2. Ascidian Mollusks, which have no branchiae and no dis- 
 tinct tentacles or arms, and which have only a leathery or mem- 
 branous exterior, and therefore are not found among fossils. 
 
 3. Brachiate Mollusks, which have two or more tentacles or 
 
MOLLUSKS. 
 
 181 
 
 arms, with no branchiae, and which are usually attached by 
 a stem ; many of which have two arms and a bivalve shell, 
 and others a circle or spiral of tentacles or arms and thus re- 
 semble flowers (Figs. 159, 160), though not radiate internally 
 like true Eadiate animals. 
 
 1. Ordinary Mollusks, These are of three orders : 
 7. Cephalopods : having the head surrounded by arms, and 
 large eyes ; the shell, when any exists as an external covering 
 for the body, is, with a rare exception, divided internally by 
 
 Figs. 151-160. 
 
 MOLLUSKS. 1. Cephalopods : Fig. 151, Nautilus, showing the partitions in the shell and 
 the animal in the outer chamber, 2. Gasteropoda: 152, Helix. 3. Pteropods : 153, Cleo- 
 dora. 4. Conchifers: 154, 155, 156, the last, the oyster. 5. Bracldopods : 157, Lingula, 
 on its stem ; 158, Terebratula, showing the aperture at l>, from which the stem for attach- 
 ment passes out. 6. Bryozoans : 159, Eschara, with the animals a little enlarged ; 160, 
 one of the animals out of the shell, more enlarged. 
 
 cross-partitions into a series of chambers, whence they are 
 called chambered shells, as in the Nautilus (Fig. 151) and Am- 
 monite (page 296). A few have an internal chambered shell ; 
 others an internal straight bone, which has sometimes a coni- 
 cal cavity. The name is from the Greek /c(f)a\rj, head, and 
 
 TTOl)?, foot. 
 
 2. Cephalates : havfng a head with distinct eyes, but no 
 arms around it, and usually a spiral shell, if any; as the 
 
182 ANIMAL KINGDOM. 
 
 Snail (Fig. 152) and other Univalves. The species of one 
 division that containing the Snail and all ordinary Uni- 
 valves are called Gasteropods, from the Greek yac-ri'ip and 
 Trot)?, implying that they crawl on their ventral surface, 
 this part acting, therefore, as a foot. In another division, they 
 have a pair of wing-like oars for swimming, and these are 
 called Pteropods (Fig. 153), from the Greek Trre/ooV, wing, and 
 TTOU?, foot. 
 
 3. Acephals (from a, without, and /fe<aXrJ, head} : having no 
 prominent head, and only imperfect eyes, if any ; and the 
 shell commonly of two parts called valves, placed either side 
 of the body, whence the common name of most of the species, 
 Bivalves; as the oyster, clam (Figs. 154-156). These species 
 are called Lamellibranchs, because they have thin lamellar 
 gills either side of the body, from lamella, a plate, and branchia, 
 a gill. The body has on either side a thin fold of ^kin called 
 the pallium, or cloak. 
 
 In Fig. 154, showing the inside of a valve, 1, 2 are impres- 
 sions of the two great muscles by which the animal closes the 
 shell, and p p is the impression of the margin of the mantle 
 or pallium, called the pallial impression. This mantle lies 
 next to the shell, and the shell is secreted by it ; the gills 
 are between it and the body of the Mollusk. In Fig. 155, 
 the pallial impression p p has a deep bend or sinus opening 
 toward the back margin of the valve. Shells having this 
 sinus in the impression are described as sinupallial, and those 
 without it as integripallial. In Fig. 156, of the oyster, there 
 is but one large muscular impression (at 2). 
 
 2, Brachiate Mollusks. These are of two orders : 
 
 7. Brachiopods : species (Figs. 157> 158) having a bivalve 
 shell, like the Lamellibranchs, but one of the vah^es dorsal 
 (or over the back), and the other ventral, instead of being on 
 the sides of the body ; moreover, the form is symmetrical 
 either side of a middle line ; that is, if a line be dropped 
 from the beak to the opposite edge (as from I to a in Fig. 
 158), the parts of the shell on the two sides of the line will 
 
RADIATES. 
 
 183 
 
 b equal. A line similarly drawn in the Lamellibranchs 
 divides the valve unequally (as in Fig. 154). The animals 
 have two spiral arms within, which serve as gills. The 
 name BracMopod, from the Greek /8/oa^tW, arm, and TTOVS, 
 foot, refers to these arms. 
 
 2. Bryozoans: species of minute size like a polyp in exter- 
 nal form, making often cellular corals which, though often in 
 thin plates or incrustations, sometimes delicately branch like 
 a moss, whence the name, from the Greek ftpvov, moss, and 
 a>ov, animal. They include the Cellepores, Flustras, etc. Fig. 
 159 shows a number of the animals protruded from their cells. 
 
 4. Sub-kingdom of Radiates. 
 
 There are three grand divisions of Kadiates : 
 
 Figs. 161-170. 
 
 RADIATES 1. Echinoderms : 161, Echinus, the spines removed from half the surface 
 (X 3); 162, Star-fish, Paleaster Niagarensis ; 163, Crinoid, Encrinus liliiformis ; 164, Cri- 
 noid, of the family of Cystideans, Calloeystites Jewettii. 2. Acalephs : 165, a Medusa, 
 genus Tiaropsis ; 166, Hydra (x 8) ; 167, Syncoryna. 3. Polyps : Fig. 168, an Actinia; 
 169, a coral, Dendrophyllia ; 170, part of a branch of a coral of. the genus Gorgonia, show- 
 ing one of the polyps expanded. 
 
 1. Echinoderms (Figs. 161 to 164): having a more or less 
 hard, inflexible exterior, which is often covered with spines, 
 
184 ANIMAL KINGDOM. 
 
 whence the name, from e^o>o?, a hedgehog, and Sep/ia, skin. 
 The mouth opens downward in all species except in some at- 
 tached species. Among them are : 7. Echinoids, in which 
 the exterior is a solid shell covered with spines, and the 
 mouth opens downward (Fig. 161 the spines are removed 
 from half of the shell) ; 2. The Asteriolds, or Star-fshes, in 
 which the exterior is rather stiff, but still flexible, so that the 
 animal flexes it in its movements (Fig. 162) and the viscera 
 extend into the arms ; 3. The Crinoids (including the Coma- 
 tulids), having flexible arms like star-fishes, but the rays and 
 body made of closely fitting solid calcareous pieces, and hav- 
 ing in the Comatulids arms for attachment, and in the other 
 Crinoids a stem and being thus plant-like. 
 
 Other kinds are the Holotliurwids, which are much like the 
 Echinoids in interior structure and the absence of arms, but 
 have no hard exterior shell, and are seldom found fossil ; and 
 the Ophiuroids, or Serpent-stars, which are near the Asteroids, 
 but have the arms very slender, with no groove beneath. 
 
 2. Acalephs (Figs. 165 - 167) : having a soft, flexible body, 
 usually of a jelly-like aspect, though rather tough, and mov- 
 ing, when free, with the mouth downward, as the Medusa 
 (Fig. 165). Some of the species called Hydroid Acalephs 
 (Figs. 166, 167), in one of their stages, if not through all, look 
 like Polyps ; and some of these Acalephs form corals, like the 
 Polyps. The Millepores are Acaleph corals. The other spe- 
 cies are mostly too soft to be common as fossils. 
 
 3. Polyps (Figs. 168-170) : having a soft body usually at- 
 tached to a support ; a mouth opening upward ; one or more 
 rows of tentacles arranged about the margin of a disk (some- 
 what like the petals of an Aster around its central disk) ; and 
 the mouth situated at the centre of the disk, as in Fig. 168. 
 Most corals are made by polyps. The coral is secreted within 
 the polyp in the same manner as bones are secreted within 
 other animals. Figs. 169, 170 represent portions of living 
 corals with the polyps expanded. The number of rays in the 
 cells of many modern corals (the Actinoids) is a multiple of 
 
PROTOZOANS. 185 
 
 six ; and that in many of the more ancient corals, those 
 called Cyatliophylloiil*, is a multiple of Jour. 
 
 5. Protozoans. 
 
 The subdivisions of Protozoans of geological importance 
 are those of the Sponges and Ehizopods. 
 
 1. Sponges. A sponge is an assemblage of minute Proto- 
 zoans produced by growth from a single germ. The united 
 animals secrete the horny fibre, and also, from an inner 
 layer, its siliceous spicules (see p. 67), when these are present. 
 In many the siliceous portion predominates ; and in some 
 tp. 314) the skeleton is wholly of silica. 
 
 Fig. 171. 
 
 Globigerina bulloides. 
 
 2. Rhizopods. PJiizopods are so called from the Greek for 
 root-like feet, because of the slender, thread-like appendages 
 (pseudopodia, false feet) which in many species are made as 
 they are protruded ; they serve for taking food, and often also 
 for digesting it. Those of special interest geologically are of 
 two groups. 
 
 1. Foraminifers, which have calcareous shells (p. 65), made 
 up usually of a group of cells spirally or alternately arranged 
 
186 
 
 VEGETABLE KINGDOM. 
 
 (Figs. 71 to 84, p. 66). The shells have minute pores (fora- 
 mina) through which the threads are protruded. Fig. 172 
 represents a living species much enlarged, with its pseudo- 
 podia extended ; and Fig. 171 the common Globigerina of 
 the sea-bottom, also greatly enlarged ; when alive and un- 
 mutilated, the latter has its shell covered with spines, as in 
 the figure, and its pseudopodia protruded along the spines 
 (Wyville Thomson). 
 
 2. Itadiolarians (or Polycystines), which have siliceous 
 shells, as explained and illustrated on page 67. Fig. 173 
 
 Fig. 172. 
 
 Fig. 173. 
 
 Fig. 172, Rotalia, living Rliizopod with pseudopodia protruded ; 173, Xiphacantha X 50, 
 
 a Radiolarian. 
 
 represents another species which has radiating spines; al- 
 though minute, it has some resemblance to the glass sponges. 
 In these species the protoplasmic animal mass (absent in thd 
 figures) is collected about the centre, and from it the pseudo- 
 podia radiate outward. 
 
 II. Vegetable Kingdom. 
 
 The two most prominent subdivisions of Plants are those 
 of (1) Cryptogams and (2) Phenogams. 
 
 The CRYPTOGAMS, or Flowerless plants, have no true flowers, 
 and hence the name from the Greek (tcpvjrro^ and yapo?), 
 referring to the concealed method of fructification. They 
 
CRYPTOGAMS. 
 
 187 
 
 comprise the Seaweeds, Mosses, Ferns, etc. They produce 
 spores in place of true seeds, the spore being a simple cellule, 
 while true seeds have about the germ-cellule more or less of 
 albumen and starch for the nutriment of the embryo plant. 
 
 The PHENOGAMS, or Floweriny plants, the term from the 
 Greek (fyaivw and 7^09), referring to the open method of 
 fructification ; that is, by means of stamens and pistils, the 
 central organs in flowers. All plants are here included that 
 have flowers, from the grasses to the ordinary forest trees. 
 
 I. Cryptogams. The lower Cryptogams consist of cellular 
 tissue alone; the higher, like Phenoganis, of both woody 
 fibre and cellular tissue. 
 
 Lower Cryptogams of the following kinds (A) have no leafy 
 stems: (1) Alya, or Seaweeds, embracing all flowerless and 
 leafless water plants; (2) Funyi, or the mushrooms, mould, 
 etc. ; (r>) Lichens, the dry gray -green and gray to brown and 
 black plants, growing in dry places, and often covering stones 
 and the bark of trees. An exposed rocky bluff usually owes 
 its color mostly to the lichens which cover it, and not to the 
 rock constituting it. The follow- 
 ing among the lower Cryptogams 
 (B) have leafy stems: (1) Mosses, 
 and (2) the Liverworts. 
 
 To the Alga3 belong the micro- 
 scopic Diatoms and Desmi'h, which 
 are one-celled (unicellular) plants, 
 living in both fresh and salt water. 
 The Diatoms (Figs. 174-179, and 
 88, p. 68) are siliceous, as already DIATOM s highly 
 explained. The Desmids are green, 
 secrete no silica, and are often 
 found fossil in flint and chert 
 (Figs. 241-247, p. 234). They 
 include also the calcareous Nullipores (p. 66), and semi- 
 calcareous Corallines; and also the microscopic Coccoliths 
 and Ehaldoliths (p, 66). 
 
 Figs. 174-179. 
 
 magnified ; 174, Pin- 
 nularia peregrina ; 175, Pleurosigma 
 angulatum ; 176, Actiuoptychussena- 
 rius ; 177, a, Melosira sulcata ; 178, 
 Giammatophora marina : 179, Baril- 
 ar'a paradoxa. 
 
188 
 
 VEGETABLE KINGDOM. 
 
 Higher Cryptogams. These Cryptogams, having bundles of 
 woody tissue in the stems, are called Acrogens, (from the 
 Greek afcpov, top, and yevvda), I grow) because they grow 
 upward and make stems, and in some cases high trees. 
 
 Acrogens are divided into (1) Ferny; (2) Lywpods, or 
 Ground-pines ; and (3) Equiwta, or Horsetails. Some tropical 
 ferns are trees 10 to 30 feet high, having a broad star of large 
 fronds at tli3 top. Ground-pines have the foliage of minia- 
 ture spruces or pines, and hence the name. In a former age 
 they grew into trees 40 feet or more in height, closely resem- 
 bling in aspect modern spruces or pines. The modern Equi- 
 seta (sometimes called scouring-rushes) are slender plants 
 with hollow stems, a little rush-like in habit. The stems 
 are jointed, and the divisions are easily broken apart at the 
 joints. Ancient species, called Calamites (because of their 
 reed-like form, from the Greek /caXa/^o?, reed), were 10 to 20 
 feet high. 
 
 II. Phenogams. Phenogams, or Flowering plants, are 
 divided into two sections, according to the mode of growth. 
 (1) The Exogens (so named from the Greek ef&>, outward, and 
 yevvdo), I groiv) have a bark separable from the wood, and 
 grow by the addition of a layer to the adjoining surfaces of 
 
 the bark and wood each 
 
 Figs. 180-183. 
 182 
 
 l.So 
 
 year, so that in a trans- 
 verse section of a stem 
 there are rings of growth 
 (Fig. 180) marking the 
 age of the stem. They 
 include all our common 
 trees and shrubbery and 
 a large part of smaller 
 plants. (2) The Endogens 
 (so named from evBov, 
 within t and yevvdw), have 
 no proper bark, and show 
 in a transverse section of the stem the ends of bundles of 
 
 Fig. 180, section of exogenous stem ; 181, id. of endo- 
 genous ; 182, fibres of the Conifer, Pinus Strobus, 
 showing dots, magnified 300 times ; 183, same of 
 Araucaria Cunningham!. 
 
PHENOGAMS. 189 
 
 fibres of woody tissue with more or less of spongy cellular 
 tissue (Fig. 181). They grow by additions to the bundles 
 of woody fibre, progressing from the exterior toward the 
 centre. They include the paliux, rattan, reed, grasses, indian 
 corn. When the bundles of fibres in a palm have reached the 
 centre, the juices can no longer ascend, and the plant dies. 
 Phenogams are divided into the following groups : 
 
 1. Grymnospenns (from ryv/juvos, naked, and ajr^r^a, seed}. 
 Growth exogenous ; the flowers exceedingly simple, there 
 
 being only one or two stamens, and the seed naked, the seed 
 in many species being on the inner surface of the scales of 
 cones ; as the Pine, Spruce, Hemlock, etc. The Gymnosperms 
 include (1) the Conifers, or the Pine-tribe of plants, usually 
 called evergreens; and (2) the Of/cads, or plants related to 
 the Ct/cas and Zamia, which have the leaves of a Palm (page 
 288), although, in fruit and wood, true Gymnosperms. 
 
 The wood of the Conifers is simply woody fibre without 
 ducts, and in this respect, as well as in the naked seed and 
 very simple flowers, this tribe shows its inferiority to the fol- 
 lowing subdivision. The fibres of Coniferous wood may be 
 distinguished, even in petrified specimens, by the dots (Fig. 
 182) along their surface, as seen under a high magnifier. The 
 dots look like holes, though really only thinner spaces. In 
 one division of the Conifers, called the Araucarice, of much 
 geological interest, these dots are alternated (Fig. 183). 
 
 2. Anyiospcrms (from dyyelov, vessel, and (TTrcp/jia, seed). 
 Growth exogenous ; the seed covered or contained in a seed- 
 vessel; as the Maple, Elm, Apple, Rose, and most of the or- 
 dinary shrubs and trees. 
 
 3. Endogcns. Growth endogenous, as above explained. 
 The flowers of Endosens include some of the most beautiful 
 
 O 
 
 kinds, as those of the Lily tribe, Orchids, etc. ; and the edible 
 products exceed in value those of all other plants, grasses 
 with wheat, indian corn, and other grains, being included, 
 as well as the fruits of several kinds of palm, banana, pine 
 apple, and other species. 
 
PART IV 
 
 HISTORICAL GEOLOGY. 
 
 HISTORICAL GEOLOGY treats of the order of succession in 
 the strata of the earth's crust, and of the changes that were 
 going on during the formation of each bed or stratum, that 
 is, of the changes in the oceans and the land ; of the changes 
 in the atmosphere and climate ; of the changes in the plants 
 and animals. In other words, it is an historical view of the 
 events that took place during the earth's progress, derived 
 from the study of the successive rocks. It is sometimes 
 called stratigrapfiical geology; but this term embraces only 
 a description of the nature and arrangement of the earth's 
 strata. 
 
 By using the means for determining the order of the sev- 
 eral formations mentioned on page 58, and by a careful study 
 of the organic remains (as fossils are often called) contained 
 in the rocks, from the oldest to the most recent, it has been 
 found that a number of great ages in the progress of this life, 
 and in other events of the history, can be made out. 
 
 The following have thus been recognized : 
 
 1. There was first an age, or division of time, when there 
 was no life on the globe ; or, if any existed, this was true 
 only in the later part of the age, and the life was probably 
 of the very simplest kinds. 
 
 2. There was next an age when Shells or Mollusks, Corals, 
 Crinoids, and Trilobites abounded in the oceans when the 
 
SUBDIVISIONS IN THE HISTORY. 191 
 
 continents were almost all beneath the salt waters, and when 
 there was, throughout its larger part, as far as fossils show, no 
 fishes and no terrestrial life. 
 
 3. There was next an age when, besides Shells, Corals, 
 Crinoids, Trilobites, and Worms, Fishes were numerous in 
 the waters, and when the lands, though yet small, were more 
 or less covered with vegetation. 
 
 4. There was next an age when the continents were at 
 many successive times largely dry or marshy land, and the 
 land was densely overgrown with trees, shrubs, and smaller 
 plants, of the remains of which plants the great coal-beds 
 were made. In animal life there were, besides the kinds 
 already mentioned, various Amphibians and some other 
 Reptiles of inferior tribes. 
 
 5. There was next an age when Reptiles were exceed- 
 ingly abundant, far outnumbering and exceeding in variety, 
 and many also in size and even in rank, those of the present 
 day. 
 
 6. There was next an age when the Reptiles had dwindled, 
 and Mammals or Quadrupeds were in great numbers over the 
 continents. 
 
 7. After this came Man; and the progress of life here 
 ended. 
 
 The above-mentioned ages in the progress of life and the 
 earth's history have received the following names : 
 
 1. Archaean Time or Age. The name is from the Greek 
 for beginning. 
 
 2. Age of Invertebrates, or the Silurian Age. 
 
 3. Age of Fishes, or the Devonian Age. 
 
 4. Age of Coal-Plants, or the Carboniferous Age. 
 
 5. Age of Reptiles, or the Reptilian Age. 
 
 6. Age of Mammals, or the Mammalian Age. 
 
 7. Quaternary Age, or the Age of Man. 
 
 The first of these ages the Arcliccan stands apart as pre- 
 paratory to the age of Invertebrates, or the Silurian, when the 
 systems of life, excepting the Vertebrate, were well displayed. 
 
192 HISTORICAL GEOLOGY. 
 
 The Silurian, Devonian, and Carboniferous ages were alike in 
 many respects, especially in the aspect of antiquity pervad- 
 ing the tribes that then lived, the shells, crinoids, corals, fishes, 
 coal-plants, and reptiles belonging to tribes that are now wholly 
 or nearly extinct. The era of these ages has, therefore, been 
 appropriately called Paleozoic time, the word Paleozoic corning 
 from the Greek vraXato?, ancient, and o>7/, life. 
 
 The next age was ushered in after the extinction of many 
 of the Paleozoic tribes ; and its own peculiar life approxi- 
 mated more to that of the existing world. Yet it was still 
 made up wholly of extinct species, and the most prominent 
 of the tribes and genera disappeared before or at its close. 
 This age corresponds to Mediaeval time in geological history, 
 and is called Mcsozoic time, from the Greek /u-eicro?, middle, and 
 0)77, life. 
 
 The next age, as well as the last, was decidedly modern in 
 the aspect of its species, the higher as well as lower. Both 
 are included under the division called Cenozoic time, from the 
 Greek /rati^o?, recent, and 0)77, life (the ai of Greek words 
 always becoming e in English, as, for example, in ether, 
 from the Greek alOr/p). 
 
 The following are, then, the grand divisions of geological 
 time adopted : 
 
 I. Archaean Time. 
 
 II. Paleozoic Time, including, 1. The Age of Invertebrates, 
 or Silurian; 2. The Age of Fishes, or Devonian; 3. The Age of 
 Coal- Plants, or Carboniferous. 
 
 III. Mesozoic Time, including the Reptilian Age. 
 
 IV. Cenozoic Time, including the Tertiary and Quaternary 
 Ages. 
 
 The following sections represent the successive formations 
 of the globe, arranged in the order of time, with the subdi- 
 visions corresponding to the Ages and Periods. 
 
AGES. 
 
 SUBDIVISIONS IN THE HISTORY. 193 
 
 Fig. 184. PALEOZOIC. AMERICAN PERIODS. FOREIGN SUBDIVISIONS. 
 
 Wenlock beds. 
 Upper Llandovcry. 
 
 Caradoc sandstone. 
 Bala limestone. 
 Llandeilo group. 
 
 TAvV</AXTrr\'uVH I- Archaean, 
 
 Arcluean 
 
194 HISTORICAL GEOLOGY. 
 
 AGES. Fig. 184. (continued). PERIODS FOREIGN SUBDIVISIONS. 
 
 Recent. 
 
 Champlain. 
 
 Glacial. 
 
 Recent. 
 
 Quaternary, or 
 Pleistocene. 
 
 Pliocene. 
 Miocene. 
 Eocene. 
 
 Upper Cretaceous. 
 Middle Cretaceous. 
 Lower Cretaceous. 
 
 Wealdea. 
 
 Oolite. 
 
 Lias. 
 
 Keuper. 
 
 Muschelkalk. 
 
 Bunter-sandstein. 
 
 In the preceding sections, Archwan is at the bottom, on the 
 left ; above it there are the names Silurian, Devonian, and so 
 on ; and the names of the Periods, Primordial, Canadian, 
 Trenton, etc., dividing off these Ages, on the right. 
 
 The names of the Periods in the first part of the section 
 (those of the Paleozoic), the first excepted, are derived from 
 the names of American rocks or localities. The names on 
 the other part are mostly European, as the series of rocks it 
 contains (those of Mesozoic and Cenozoic time) are more com- 
 plete in Europe than in America. 
 
SUBDIVISIONS IN THE HISTORY, 
 
 195 
 
196 HISTORICAL GEOLOGY. 
 
 The various strata in the formations of an age are very 
 diversified in character, limestones being overlaid abruptly 
 by sandstones, conglomerates, or shales, or either of these 
 last by limestones ; and each may be very different from the 
 following in its fossils. These abrupt transitions in the 
 strata are proofs that there were great changes at times in 
 the conditions of the region where the strata were formed, 
 and the transitions in the kinds of fossils are evidence of 
 great destructions at intervals in the life of the seas. Such 
 transitions, therefore, naturally divide off the ages into 
 smaller portions of time, or periods, as they are called. By 
 transitions similar in kind, but not so great, periods may 
 often be subdivided into still smaller parts, or epochs. 
 
 The map on page 195 represents the distribution of the rocks 
 of the different ages, as surface-rocks, over the United States 
 and Canada. The areas indicated by the different kinds of 
 lining are stated on the map. 
 
 The areas left white are of unascertained or doubtful age ; 
 cr. marks outcrops of Cretaceous on the Atlantic border ; 
 C., Cincinnati ; CL, Claiborne ; V., Vicksburg. 
 
 The Silurian strata may underlie the Devonian, end both 
 Silurian and Devonian the Carboniferous. The black areas 
 of the Carboniferous period do not, therefore, indicate the 
 absence of Devonian and Silurian, but only that the Car- 
 boniferous strata are the surface strata over the region. 
 There may even be exceptions to this remark with regard 
 to the surface strata ; for, over the areas thus marked Car- 
 boniferous, older rocks may occur in some of the bluffs along 
 the valleys, or occupy small areas in the region, which are 
 too limited to be noted on so small a map. 
 
 The map on page 197 represents the surface-rocks of the 
 State of New York and Canada, the several areas corre- 
 sponding to the periods. For the Silurian, the lines or dots 
 are drawn horizontally, as in the preceding, and for the De- 
 vonian, vertically. There is no Carboniferous, except near 
 the southern border of the State of New York. 
 
SUBDIVISIONS IN THE HISTORY. 
 
 197 
 
 Geological Map of New Yorlr and Canada. 
 
198 
 
 ARCHAEAN TIME. 
 
 No. 1. The Archseaii. 
 
 2. The Primordial Period. 
 
 3. The Canadian Period. 
 
 4. The Trenton Period. 
 
 5. The Niagara Period. 
 
 6. The Salina Period. 
 
 9. The Upper Helderberg Period. 
 
 10. The Hamilton Period. 
 
 11. The Chemung Period. 
 
 12. The Catskill Period. 
 
 Fig. 187. 
 
 ~ 
 
 Lower 
 Silurian. 
 
 Upper 
 Silurian. 
 
 Djvouian. 
 
 Carbonif- Devonian, 
 
 erous. 
 
 Silurian. 
 
 In the section in Fig. 187, the rocks of the successive 
 periods are represented in order, from the Archaean, in North- 
 ern New York, southwestward to the Coal-formation of Penn- 
 sylvania, showing that they succeed one another on the map 
 simply because they come to the surface in succession. The 
 amount of dip and its regularity are greatly exaggerated in 
 the section ; and there is no attempt to give the relative 
 thickness of the beds. 
 
GEOGRAPHICAL DISTRIBUTION. 
 
 199 
 
 L ARCHAEAN TIME. 
 1. Rocks: Kinds and Distribution. 
 
 1, Distribution. The Archaean era commenced with the 
 origin of the earth's crust, arid includes the oldest rocks of 
 the globe. Its formations are those upon which the fos- 
 siliferous rocks of the Silurian and subsequent ages have 
 been spread out, and the material out of which most of 
 these later rocks have been made. 
 
 The Archaean rocks extend around the whole sphere ; but, 
 
 Fig. 188. 
 
 Archaean Map of North America. 
 
 in general, they are concealed from view by subsequent for- 
 mations. In North America they are surface rocks over a 
 krge area north of the great lakes, shaped like the letter V, 
 
200 ARCII^AN TIME. 
 
 the longer branch of which area runs northwest to tlio Arctic 
 Ocean, and the shorter, northeast to Labrador. The white 
 area on the preceding map, in what is now British America, 
 is the portion of the continent here referred to. There is 
 also a small Archaean area in Northern New York (see map 
 page 197); the Highlands of Putnam County, New York, and 
 of New Jersey is Archaean, and so also in part the Blue 
 Pudge of Virginia; another south of Lake Superior; and a 
 fjv/ other spots east of the Rocky Mountains. Some high 
 ranges also of the Rocky Mountain region are Archaean. 
 
 In Europe Archaean rocks are in view in the great iron re- 
 gions of Sweden and Norway, in Bohemia, and in Scotland. 
 
 2. Kinds of Rocks. The rocks are mostly crystalline rocks, 
 such as granite, syenyte, gneiss, syenytic gneiss, mica 
 schist, hornblende schist, chlorite slate, and granular lime- 
 stone. But besides these there are some hard conglomerates, 
 quartz-rocks or gritty sandstones, and slates. The beautiful 
 iridescent feldspar called labradorite (page 22) is a common 
 constituent of some of the coarse crystalline or granitic rocks. 
 
 An abundance of iron is one characteristic of the beds. 
 The rocks very often contain hornblende, an iron-bearing 
 mineral, or black mica, also iron-bearing. Along with the 
 rocks there are, in some regions, immense beds of iron ore 
 (i i i, in Fig. 189). In Northern New 
 Pig. 189. York the beds are 100 to 200 feet thick. 
 
 Similar iron-ore beds occur in New Jer- 
 sey, Michigan, south of Lake Superior, 
 and in Missouri. Graphite is common 
 in some places, and constitutes 2 to 30 
 per cent of some beds, especially of the limestones. 
 
 3. Disturbance and Crystallisation of the Rocks. The layers 
 of gneiss and other schistose rocks, with the included lime- 
 stones, are nowhere horizontal ; but, instead of this, they 
 dip at all angles, and are often flexed or folded in a most 
 complex manner. Fig. 190 represents the folded character 
 of the Archasan rocks of Canada. The folded rocks in this 
 
ORIGIN OF THE ROCKS. 201 
 
 figure are overlaid by beds that are nearly horizontal, which 
 belong to the Lower Silurian. 
 
 Owing to the discolations and uplifts which the rocks have 
 undergone, the iron-ore beds look like veins ; and even the 
 strata of crystalline limestone have often a similar vein-like 
 
 Fig. 190. 
 2 
 
 Fig. 190, by Logan, from the south side of the St. Lawrence in Canada, between Cascade 
 Point and St. Louis Rapids ; 1, Archaean gneiss; 2, 2, Silurian strata. 
 
 appearance. Where strata have been thrown up so that the 
 layers stand vertical, the included bed of ore will be vertical 
 also, and will descend downward in the same manner as a 
 true metallic vein ; and through the breaking and faulting of 
 the strata many of those irregularities would result that are 
 so common in veins. 
 
 Gneiss, mica schist, granular limestone, and other crystal- 
 line rocks have been described on page 35 as metamorphic 
 rocks, rocks that were once horizontal sandstones, shales, 
 and stratified limestones, and which have been, by some pro- 
 cess, crystallized. The gneiss and schists in Archaean regions, 
 although upturned at all angles, are actually in layers or 
 strata alternating with one another, as common with ordinary 
 sandstones and shales ; and the ore-beds are conformable to 
 the layers of schist and quartzyte in which they occur. 
 
 4. Conclusions as to the Origin of the Rocks. The following 
 conclusions hence follow : 1. That the Archasan rocks here 
 referred to were originally horizontal strata of sandstones, 
 shales, and limestones; 2. That after their formation they 
 were pushed out of place by some great movement of the 
 earth's crust, which uplifted and folded them, so that now 
 they are nowhere horizontal; 3. That, besides being dis- 
 placed, they were also crystallized, that is, changed into 
 metamorpliic rocks. 
 
 The thickness of the Archaean rocks of Canada is stated to 
 exceed 30,000 feet. So great an accumulation of marine beds 
 is proof that the era was very long. 
 
202 ARCHAEAN TIME. 
 
 It is altogether probable that the time of the uplifting and 
 that of the metamorphism were the same. There may have 
 been many such metamorphic epochs in the course of Archaean 
 time. But, since even the latest beds of the Archaean are thus 
 upturned and crystallized, an extensive revolution of this kind 
 must have been a closing event of the age. Fig. 190 shows 
 that the upturning preceded the formation of the lowest Silu- 
 rian beds, for these lie undisturbed over the folded and crys 
 tallized Archaean. 
 
 Below the surface Archaean rocks there must be others, 
 constituting the interior portions of the earth's crust. If the 
 earth were originally a melted globe, as appears altogether 
 probable, the earth's crust is its cooled exterior. Whenever 
 the crust formed, its surface must have been at once worn by 
 the waves, wherever within their reach, and deposits of sand, 
 pebbles, and clay must have been formed; and in this way 
 the Archaean formations were begun. But at the same time 
 that these surface strata were in progress, the crust would 
 have been increasing in thickness within by the cooling 
 which was continuing its progress. Of the interior rock of 
 the crust little is known. 
 
 2. Life. 
 
 The Archaean rocks contain no distinct fossil-plants. If 
 plants existed then, they were Sea-weeds; for remains of 
 none higher than sea-weeds occur in the overlying Lower 
 Silurian formations. It is possible that Lichens existed over 
 the exposed rocks ; for such plants away from waters would 
 not have left their remains in the mud or sands of the seas. 
 There may also have been Fungi of simple kinds. But there 
 is reason to believe that Mosses and higher plants were all 
 absent, for none of these have been found in any Lower 
 Silurian strata. 
 
 The graphite, abundant in some beds in Canada, is probable 
 evidence of the existence of plants, because it is known that 
 
GENERAL OBSERVATIONS. 
 
 203 
 
 Fig. 191. 
 
 in later times graphite has been formed out of their remains. 
 The limestone beds suggest the idea that there was present 
 either vegetable or animal life ; for almost all limestones (see 
 page 63) are of organic origin. 
 
 The annexed figure represents 
 what has been regarded as a fossil 
 form, and named Eozoon Cana- 
 dense. It is supposed to have 
 been a coral-like mass made by 
 Protozoans of the class of Khizo- 
 pods, the simplest of all kinds 
 of animal life. Each dark layer 
 in the mass is supposed to mark 
 the position of the animals. Its 
 animal nature has not, however, 
 been placed beyond doubt. Still, 
 it is altogether probable that 
 Ehizopods existed in the waters Eozoou Canadense . 
 
 before the close of the Archaean 
 
 era, and that the beds of limestone have been made of 
 their minute shells, or else of calcareous Nullipores. 
 
 3. General Observations. 
 
 The large Archaean area on the map, page 199, represents 
 the main portion of the dry land of North America in the 
 later part, or at the close, of the Archaean age ; for it consists 
 of the rocks made during the age, and is bordered on its dif- 
 ferent sides by the earliest rocks of the next age. It is the 
 outline, approximately, of Archaean North America, or the 
 continent as it appeared when the Silurian age opened. It 
 is, therefore, the beginning of the dry land of North America, 
 the original nucleus of the continent. The smaller Archaean 
 areas mentioned appear to have been mountain ridges and 
 islands in the great continental seas. 
 
 Europe had its Archaean lands at the same time in Scandi- 
 
204 PALEOZOIC TIME. 
 
 navia, Scotland, Bohemia, and some other points ; and prob- 
 ably each of the other continents was then represented by its 
 spot, or spots, of dry land. All the rest of the sphere, except- 
 ing these limited areas, was an expanse of waters. 
 
 The facts to be presented under the Silurian age teach that 
 the great but yet unmade continents, although so small in the 
 amount of dry land, were not covered by the deep ocean, but 
 only by comparatively shallow oceanic waters. They lay just 
 beneath the waves, already outlined, prepared to commence 
 that series of formations the Silurian, Devonian, Carbonif- 
 erous, and others which was required to finish the crust for 
 its ultimate continental purposes. Portions may have been 
 at times a few thousands of feet under water, but in general 
 the depth was small compared with that of the ocean. 
 
 We thus gather some hints with regard to the geography 
 of America in the period of its first beginnings. 
 
 The outlines of the Northern Archaean area on the map, 
 page 199 the embryo of the continent and the directions 
 of the other Archaean lands are very nearly parallel to the 
 coast lines of the present continent. The Archasan lands, 
 both in North America and Europe, are largest in the more 
 northern latitudes. 
 
 II. PALEOZOIC TIME. 
 
 PALEOZOIC TIME includes three ages : 
 
 1. The Age of Invertebrates, or Silurian Age. 
 
 2. The Age of Pishes, or Devonian Age. 
 
 3. The Age of Coal-Plants, or Carboniferous Age. 
 
 In describing the rocks of these ages over North America, 
 and the events connected with their history, there are four 
 distinct regions to be noted, distinct, because in an impor- 
 tant degree independent in their history. These are, 
 
 1, The Eastern border region, or that near the Atlantic bor- 
 der, including Central and Eastern New England, New Bruns- 
 
SILURIAN AGE. 205 
 
 wick and Nova Scotia, and the coast region south of New 
 York. 
 
 2. The Appalachian region, or that now occupied by the 
 Appalachian Mountain chain, from Labrador on the north, 
 along by the Green Mountains, and the continuation of the 
 heights through New Jersey, Pennsylvania, Virginia, East- 
 ern Tennessee, and so south westward to Alabama. 
 
 3. The Interior Continental region, or that west of the Appa- 
 lachian region, continued over much of the present eastern 
 slope of the Rocky Mountain chain. 
 
 4. The Western border and Rocky Mountain region, from the 
 crest of the Rocky Mountains west ,vard. 
 
 I. AGE OF INVERTEBRATES, or SILURIAN AGE. 
 
 This Age is called Silurian from the region of the ancient 
 Silures in Wales, where the rocks occur. It was first so 
 named by Murchison. 
 
 The Age is naturally divided into Lower and Upper Silurian, 
 each corresponding, in America, to three periods, thus : 
 
 1. Lower Silurian. 
 
 '1. Primordial, or Cambrian Period : including the Cam- 
 brian of England, with the Lingula flags. 
 
 2. Canadian Period: including the Tremadoc slates, the 
 Skiddaw slates, and Stiper-stones group of Great Britain. 
 
 3. Trenton Period : including the Llandeilo flags, Bala 
 limestone, and Caradoc sandstone of Great Britain. 
 
 2. Upper Silurian. 
 
 1. Niagara Period: including the Wenlock beds of Great 
 Britain, with the Upper Llandovery. 
 
 2. Salina Period. 
 
 3. Lower Helderbcrg Period : including part of the Ludlow 
 beds of Great Britain. 
 
 4. Oriskany Period : including the upper part of the Lud- 
 low beds. 
 
206 PALEOZOIC TIME. LOWER SILURIAN. 
 
 1. Primordial Period. 
 I. Rocks: Kinds and Distribution. 
 
 The strata of the Primordial period, in America, over the 
 Interior Continental basin, are exposed to view at intervals 
 from New York to the Mississippi River ; beyond the river, 
 over some parts of the eastern and western slopes of the 
 Rocky Mountains ; and also in Texas. The area on the map 
 of New York and Canada (page 197) is that numbered 2, lying 
 next to the Archsean. There is reason to believe, from the 
 many points at which the strata come to the surface, that 
 they extend over the larger part of the continent outside of 
 the Archaean area represented on the map, page 199 though 
 concealed by other less ancient strata over most of the sur- 
 face. 
 
 Through the Interior region the lower rocks are in part a 
 sandstone, called the Potsdam sandstone, from a locality in 
 Northern New York. The sandstone beds contain, in many 
 places, ripple-marks (Fig. 24, page 46) ; mud-cracks (Fig. 26) ; 
 layers showing the wind-drift and ebb-ancl-flow structure 
 (Figs. 22 /, e) ; worm-burrows, and also occasionally the 
 tracks of some of the animals of the period. 
 
 In the Appalachian region in Vermont, north in Canada, 
 and in Pennsylvania, etc., the rocks are slates overlying 
 sandstone, along with some limestone, the whole 2,000 to 
 7,000 feet or more thick. 
 
 In the Eastern border region beds of the period occur at 
 Braintree, near Boston, at St. John's, New Brunswick, and 
 on the Labrador coast. These are the oldest of American 
 Primordial rocks, and have been distinctively called the 
 Acadian group. 
 
 In Great Britain the Primordial rocks are hard sandstones 
 and slates. The uppermost include the Lingula flags. They 
 are most extensively in view in North arid South Wales and 
 in Shropshire. The lower portion of the series, of great thick- 
 
PRIMORDIAL PERIOD. 207 
 
 ness, consisting of slates and other rocks, was named Cam- 
 brian by Sedgwick 
 
 In Lapland, Norway, Sweden, and Bohemia, Primordial 
 strata have been observed. If the strata of later date could 
 be removed from the continents, we should probably find the 
 Primordial beds extensively distributed over all the conti- 
 nents. 
 
 2. Life. 
 
 These most ancient of fossiliferous rocks contain no re- 
 mains of terrestrial life. The plants of the period that left 
 traces in the rocks were all Sea-weeds. Among animals, the 
 sub-kingdoms of Radiates, Mollusks, and Articulates were rep- 
 resented by water-species, and by these only ; there is no evi- 
 dence that there were any Vertebrates. 
 
 The older sandstone abounds in many places in a shell 
 smaller, in general, than a finger-nail, related to the Fig 192 
 modern Lingula (Fig. 192). It is the shell of a 
 Mollusk of the tribe of Brachiopods. It stood on 
 a stem, when alive, as represented in Fig. 157, page 
 181. These shells are so characteristic of the beds 
 
 i L -i j.1 prima. 
 
 in many regions as to have suggested the name 
 Lingula flags, or Lingula sandstone. Among Mollusks there 
 were only Brachiopods for the greater part of the Primordial 
 period ; but in the later division appear some species of La- 
 mellibranchs, Pteropods, Gasteropods, and Cephalopods. 
 
 Another tribe very prominent among the earliest of the 
 earth's animals is that of Trilobites, of the sub-kingdom of 
 Articulates, and class of Crustaceans. 
 
 One of the largest of them, and a kind characteristic of the 
 Lower or Acadian division of the Primordial, is represented 
 in Fig. 193, one sixth the natural size. Its total length, when 
 living, must have been eighteen inches or more, arid hence it 
 was about as large as any living Crustacean. The specimen 
 figured was found at Brnintree, south of Boston. As shown, 
 it had large eyes situated on the head-shield, evidence. 
 
208 
 
 PALEOZOIC TIME. LOWP;R SILURIAN. 
 
 Fi-?. 193. 
 
 like other points in the structure that the species, although of 
 
 the earlier division of the Primordial, were far removed from 
 
 simple germ-like forms. Tri- 
 lobites are supposed to have 
 had membranous or foliaceous 
 plates for swimming. Fig. 194 
 shows the track of a large 
 animal (reduced to one sixth) 
 found by Logan in the Canada 
 beds, which may have been 
 made by one of the great Trilo- 
 bites as it crawled over the sand. 
 The existence of marine worms 
 among the earliest animals of 
 the globe is proved by the 
 great numbers of worm- holes 
 or burrows in the sandstones, 
 now filled with hard sandstone 
 like that of the rock. They 
 are very similar to the holes 
 made by such worms in the 
 sands of sea-shores at the pres- 
 ent time. One species has been 
 called 
 
 Scolithus linearis. These worm-holes 
 
 are common in the European as 
 
 well as American Primordial sand- 
 stones. 
 
 There were also Crinoids of the 
 
 sub-kingdom of Eadiates (page 65), 
 
 for disks from the broken stems 
 
 of Crinoids are not uncommon. 
 
 And among Protozoans there were 
 
 Sponges, and probably the minute 
 
 Ehizopods (page 66). 
 
 Sponges among Protozoans, Crinoids among Eadiates, 
 
 THILOBITE. Paradoxidea Harlani 
 (x 4). 
 
 Fig. 194. 
 
 Track of a Trilobite (X |). 
 
PRIMORDIAL PERIOD. 209> 
 
 Brachiopods and some representatives of other tribes among 
 Mollusks, Worms and Trilobites among Articulates, and Sea- 
 weeds among Plants, make up the living species thus far dis- 
 covered; and iii this Primordial population, Trilobites took 
 the lead. There is as yet no evidence that the dry Primor- 
 dial hills bore a Moss or Lycopod, or harbored the meanest 
 Insect, or that the oceans contained a single Fish. 
 
 3. General Observations. 
 
 The ripple-marks, mud-cracks, and tracks of animals pre- 
 served in this most ancient of Paleozoic rocks are records 
 left by the waves, the sun, and the life of the period, as to 
 the extent and condition of the continent in that early era. 
 These markings teach that when the beds were in progress 
 a large part of the continent lay at shallow depths in the 
 sea, so shallow that the waves could ripple its sands ; that 
 over other portions the surface was a sand-flat exposed at 
 low tide ; or a sea-beach, the burrowing-place of worms 
 or a mud-flat, that could be dried and cracked under the 
 heat of the sun, or in a drying atmosphere. 
 
 With such evidences of shallow water or emerged flats 
 in a formation extending widely over the continent, it is a 
 safe conclusion that the North American continent was 
 at the time in actual existence, and probably not far from 
 its present extent ; and, although partly below the sea-level, 
 and in some places deeply so, it was generally at shallow 
 depths. The same may prove to have been true of the other 
 continents. There is, in fact, evidence of other kinds which, 
 taken in connection with the above, leaves little doubt that 
 the existing places of the deep ocean and of the continents 
 were determined even in the first formation of the earth's 
 crust in the early Archaean era, and that, in all the move- 
 ments that have since occurred, the oceans and continents 
 have never changed places. 
 
 This preservation of markings, seemingly so perishable, on 
 the early shifting sands, is a very instructive fact. They 
 
 14 
 
210 PALEOZOIC TIME. LOWER SILUKIAN. 
 
 illustrate part of the means by which the earth has, through 
 time, been recording its own history. The track of a Trilo- 
 bite, or of a wavelet, is a mould, in sand or earth, into which 
 other sands are cast both to copy and preserve it ; for if the 
 waves or currents that succeed are light, they simply spread 
 new sands over the indented surface, without obliterating 
 the mould ; and so the addition of successive layers only 
 buries the markings more deeply and thus protects them 
 against destruction. When, finally, consolidation takes 
 place, the track or ripple-mark is made as enduring as 
 the rock itself. 
 
 After the formation in North America of the great Primor- 
 dial sandstone, there was a change in the condition of the 
 surface, especially over the interior of the continent. For 
 limestone strata began then to form where sandstones were 
 in progress before. This change was probably some increase 
 in the depth and clearness of the Interior Continental sea. 
 Along the borders of this sea that is, in New York and 
 along the Appalachian region from Quebec into Virginia 
 the rock was a sandstone or shale, with some subordinate 
 strata of limestone. 
 
 2. Canadian and Trenton Periods. 
 
 The CANADIAN period is so named from Canada, where 
 the rocks are well displayed and have been most thoroughly 
 studied; and the TRENTON period, from Trenton Falls, just 
 north of Utica, the river at the Falls running between 
 high bluffs of Trenton limestone. 
 
 In Great Britain the first of these periods covers the era 
 01 the Tremadoc and Skiddaw slates, and the latter that of 
 the Bala limestone and Llandeilo flags. 
 
 I. Rocks: Kinds and Distribution. 
 
 In the Primordial period the rock deposits formed over the 
 North American continent were mainly of sands or mud, 
 
CANADIAN AND TRENTON PERIODS. 211 
 
 making sandstones and shales ; and but little limestone was 
 formed. The Canadian period is one of transition to a third, 
 the Trenton, when limestones were in progress over nearly 
 the whole breadth of the continent, the Appalachian and 
 Arctic regions, as well as the Interior Continental. 
 
 The rocks of the Canadian period to the eastward in New 
 York and Canada are, 1. A sandstone associated in places 
 with much limestone, and called, in allusion to the limestone, 
 the Calciferous sand-rock ; 2. South of Quebec, shale, sand- 
 stone, and thin beds of limestone, called the Quebec group ; 
 3. A limestone formation, called the Chazy limestone, from a 
 place of that name in Northern New York. The latter lime- 
 stone (with probably beds of the Quebec group) makes part 
 of the granular limestone or marble of the Green Mountains 
 from Vermont to Connecticut, and has great thickness also in 
 Pennsylvania and Virginia. In the Interior basin the rock 
 of the period is mainly limestone in Iowa and Wisconsin 
 the Lower Magnesian limestone excepting to the north, 
 where the upper part is sandstone (St. Peter's sandstone) and 
 along the south side of Lake Superior, where there is only 
 sandstone. The " Pictured Kocks " and the thick sandstones 
 of Keweenaw Point, remarkable for their intersection by trap 
 dikes and veins of copper, have been supposed to be of this 
 period, but are probably Primordial. 
 
 The Trenton period is remarkable for its extensive lime- 
 stone formation. The limestone occurs in Canada ; in New 
 York (the beds at Trenton Falls giving it its name) ; along the 
 Appalachian range ; in Ohio and other States of the Ohio and 
 Mississippi basin ; from Wisconsin, northwestward along the 
 west side of the Archaean area ; and in the Arctic regions. It 
 is in most places Mil of fossils. The " Birdseye " and " Black 
 Eiver" limestones are part of the Trenton formation. The 
 rock of the later part of the Trenton period (called the Cincin- 
 nati epoch), in New York, and the Appalachians, is shale and 
 sandstone, and even in the Interior basin the limestones are 
 often, as about Cincinnati, quite clayey or impure. The Utica 
 
212 PALEOZOIC TIME. LOWER SILURIAN. 
 
 shale and Lorraine shale belong to this era. The crystalline 
 limestone (marble) of Vermont and Western Massachusetts 
 and Connecticut, with the associated hydromica slate, clay- 
 slate, mica schist, and quartzyte, is Lower Silurian ; it con- 
 tains, at several localities in Vermont, Canadian and Tren- 
 ton fossils. 
 
 The thickness of the rocks of the Canadian and Trenton 
 periods in Pennsylvania is over 7,500 feet ; while in Illinois 
 it is but 750 feet, and in Missouri about 2,000 feet. 
 
 The rocks of this era in Great Britain are shales and shaly 
 sandstones, with but little limestone. The Tremadoc slates 
 are dark slates over 1,000 feet thick in Wales, passing below 
 into the Lingula flags, and above into the Llandeilo beds. The 
 Llandeilo flags are shaly sandstones ; and, together with the 
 associated shales, they have a thickness of many thousand 
 feet. Above them there are the Caradoc sandstone of Shrop- 
 shire, and the Bala formation, the latter sandy slates and sand- 
 stone, with thin beds of limestone, in Wales. In Scandinavia 
 the rocks are limestone, overlaid by slates and flags ; and in 
 the Baltic provinces of Eussia part of the Interior Conti- 
 nental portion of the Eastern Continent they are mainly 
 limestones. 
 
 2. Life. 
 
 The life of these periods, like that of the Primordial, was, 
 as far as evidence has been collected from the American or 
 foreign rocks, marine, plants excepted. 
 
 The plants found fossil are Sea-weeds, and also the first of 
 land plants, of the tribes of Lycopods and Ferns. 
 
 All the sub-kingdoms of animals were represented, with the 
 exception of the Vertebrates. Among Radiates there were 
 Corals and Crinoids ; among Mollusks, representatives of all 
 the several orders ; among Articulates, the water-divisions, 
 Worms and Crustaceans. 
 
 1. Radiates. The Canadian beds, especially the finer 
 slates and shales, are remarkable for the great abundance 
 
CANADIAN AND TRENTON PERIODS. 
 
 213 
 
 of very delicate plume-like remains of Kadiate life, called 
 Graptolites, from the Greek 7pac/>o>, / write. 
 
 GRAPTOLITES. Fig. 195, Dichograptus Logani, the central portion of a radiating group 
 of stems with parts of the stems ; 196', same, portion of one of the stems, and 196 a, part 
 of stems enlarged ; 197, Uiplojraptus pristis ; 198, 19J, Pnyilograptus typus ; 200, the 
 young of a Graptolite. 
 
 A few of the kinds are represented in Figs. 195, 196, 198- 
 200, and one spacies, from the later part of the Trenton 
 period, in Fig. 197. In the living state there were cells 
 along the notched margin, one for each notch, from which 
 little star-shaped animals extruded themselves. They be- 
 long to the tribe of Hydroids, under Acalephs, described 
 on page 184. 
 
 Fig. 201 represents one of the Corals of the Trenton. Its 
 shape is that of a curved cone, a little like a short horn, the 
 small end being the lower. At top, when perfect, the cavity 
 of the coral is divided off by plates radiating from the centre. 
 Such corals are called Cyatlwphijlloid corals, from the Greek 
 /cva9os, cup, and c])v\\ov, leaf, alluding to the cup full of radi- 
 ating leaves or plates. When living, the coral occupied the 
 interior of an animal similar to that represented in Fig. 168, 
 or Fig. 169 on page 183. 
 
 Another kind of coral, of a hemispherical form, and made 
 up of very fine columns, is represented in Figs. 202, 203, the 
 latter showing the interior appearance. It is called Chcctetes 
 lycoperdon. Another, of coarser columns, each nearly a 
 sixth of an inch in diameter, is called the Columnaria alveo- 
 
214 
 
 PALEOZOIC TIME. SILURIAN. 
 
 lata. In a transverse section the columns are divided off by 
 horizontal partitions. Masses of this coral have been found 
 that weigh each between two and three thousand pounds. 
 
 Fig. 204 shows the form of one of the Crinoids, though the 
 stem on which it stood is mostly wanting, and the arms are 
 not entire. The mouth was in the centre above, and the ani- 
 mal was related to the Comatula among star-fishes, from 
 which it differed in being attached to the sea-bottom by means 
 of a jointed stem. There were also true star-fishes in the seas. 
 
 Figs. 201-212. 
 
 204 
 
 202 
 
 RADIATES OF THE TRENTON PERIOD - Fig. 201, Petraia corniculum ; 202, 203, 
 Chsetetes lycoperdon; 204, Lecanocrinus elegans. MOLLTJSKS : Fig. 205, Stictopora 
 acuta ; 206, Orthis testudinaria ; 207, Orthis occidentalis : 208, Leptsena sericea ; 209 
 Ambonychia bellistriata ; 210, Raphistoma lenticularis ; 211, Orthoceras junceum. 
 ARTICULATES : Fig. 212, Asaphus gigas. ^ 
 
 2. Mollusks. Among Mollnsks Bryozoans were very com- 
 mon : the fossils are small cellular corals : one is shown in 
 Fig. 205. Brachiopods were still more characteristic of the 
 
CANADIAN AND TRENTON PERIODS. 215 
 
 period, and occur in vast numbers. Fig. 206 is Orthis testu- 
 dinaria ; Fig. 207, 0. Occident alis ; Fig. 208, Lepcena sericca. 
 There were also some Lamellibranchs, as Fig. 209, Arnbony- 
 ckia bellistriata ; and some Gasteropods, as Fig. 210, Raphi- 
 stoma lenticular is. Shells of Cepbalopods were especially 
 common under the form of a straight or curved horn with 
 transverse partitions. Fig. 211, Orthoceras junceum, repre- 
 sents a small species. One kind had a shell 12 or 15 feet 
 long and nearly a foot in diameter. The word Orthoceras is 
 from the Greek 6p66s straight, and /cepas horn. 
 
 There were some species also of the genus Nautilus. 
 
 3. Articulates. Fig. 212 represents one of the large Trilo- 
 bites of the Trenton rocks, the Asaphu* gigas, a species 
 sometimes found a foot long. Another Trilobite is the Caly- 
 mene Mumenbachii, represented in Fig. 148, page 180. 
 
 While Trilobites appear to have been the largest and high- 
 est life of the Primordial seas, Cephalopods, of the Orthoceras 
 family, far exceeded Trilobites in both respects in the Trenton. 
 The larger kinds must have been powerful animals to have 
 borne and wielded a shell 12 or 15 feet long. Although 
 clumsy compared with the fishes of a later age, they emu- 
 lated the largest of fishes in size, and no doubt also in their 
 voracious habits. Crustaceans, in their highest divisions, as 
 the Crabs, may perhaps be regarded by some . as of superior 
 rank to Cephalopods. But Trilobites, of the inferior division 
 of Crustaceans, without proper legs, living a sluggish life in 
 slow movement over the sands or through the shallow waters, 
 or skulking in holes, or attached like limpets to the rocks, 
 were far inferior species to the Cephalopods. 
 
 3. General Observations. 
 
 1. Geography. The wide continental region covered by the 
 Trenton limestone formation, stretching over the Appalachian 
 region on the east, and widely through the Interior basin, 
 must have been throughout a clear sea, densely populated 
 over its bottom with Brachiopods, Corals, Crinoids, Trilobites, 
 
216 PALEOZOIC TIME. 
 
 and the other life of the era. It may, however, have been a 
 shallow sea ; for the corals and beautiful shells of coral reefs 
 live mostly within 100 feet of the surface. 
 
 During the later part of the period, or that of the Cincin- 
 nati group, the same seas, especially on the north, became 
 more open to sediment, through some change of level or of 
 coast-barriers, and consequently much of the former life dis- 
 appeared, and other kinds, adapted to impure waters or to 
 muddy bottoms, supplied their places. 
 
 2. Disturbances during the Lower Silurian, and at its Close. 
 1. Igneous ejections in the Lake Superior district. During the 
 progress of the Canadian period there were extensive igneous 
 ejections through fractures of the earth's crust in the vicinity 
 of Lake Superior, about Keweenaw Point and elsewhere ; and 
 probably to some extent also over the bottom or area of the 
 lake itself, for this is indicated by the dikes and columnar 
 trap of Isle Eoyale, an islai in the lake. These rocks, which 
 were melted when ejected, now stand in many places in bold 
 bluffs and ridges ; and mixtures of scoria and sand make up 
 some of the conglomerate beds of the region. The sandstones, 
 penetrated by the dikes of trap, and made partly before and 
 partly after the ejection, have a thickness in some places of 
 six or eight thousand feet. The great veins of native copper 
 of the Lake Superior region are part of the results of this 
 period of disturbance. The copper occurs in masses, sheets, 
 strings and grains, all more or less crystalline, and one sheet 
 was 40 feet long and about 200 tons in weight. 
 
 2. Emergence of the region of the Green Mountains. The 
 changes from deep to shallow seas, or partly emerged flats, 
 during the Silurian era, are evidence that changes of level, 
 by gentle movements or oscillations in the earth's crust, were 
 going on throughout it. But after the Lower Silurian had 
 closed there appear to have been greater and more permanent 
 changes. The valley of Lake Champlain and the Hudson, as " 
 shown by Logan, probably dates from this time. The Green 
 Mountains were probably then made and became part of the 
 
LOWER SILURIAN. 217 
 
 stable dry land, like the Archaean regions. (See map, page 199.) 
 That they were not dry land before is shown by the Chazy 
 and Trenton limestones in their structure, for these are of 
 marine origin ; and that the region was above the water from 
 and after this time is indicated by the fact that the Trenton 
 formations were the latest there formed, and by the still more 
 important observation that near Hudson, in the Hudson Paver 
 valley, and near Bernardston, in the Connecticut Valley, there 
 are Upper Silurian rocks overlying unconformably the up- 
 turned older rocks. 
 
 During the progress of the Lower Silurian era a great thick- 
 ness of rock had been made over the Green Mountain region, 
 
 - probably 15,000 or 20,000 feet. These beds were laid down, 
 not in a sea 15,000 or 20,000 feet deep until it was full, but 
 in shallow waters over a bottom that was gradually sinking, 
 
 - and so gradually that the rock-material accumulating over 
 it kept it shallow. Then, when the slowly forming trough 
 had reached this depth, the epoch of catastrophe, that is, of 
 mountain-making, began when the beds were displaced and 
 folded, and consolidated or crystallized. Quartzose sandstones 
 were changed to hard quartzyte, the rock of high ridges in 
 Berkshire and Vermont ; earthy sandstones were made into 
 mica-schist and gneiss ; and common limestones came out 
 white or clouded marbles, now extensively quarried for archi- 
 tectural purposes in Canaan, Connecticut, Berkshire County 
 in Massachusetts, and at Eutland and elsewhere in Vermont. 
 Thus, this northern end of the Appalachian region was the 
 first of it to be made into mountains and become part of tho 
 stable land : the rest of it to the south, as well as the cen- 
 tral region of Southern New York, was still receiving, for a 
 long era afterward, new formations, and so preparing for 
 another time of mountain-making, that of the Alleghany 
 range. 
 
 Besides this uplifting and upturning in Western New Eng- 
 land, there was at the same time, as shown by Safford and 
 Newberry, a bending upward of the Lower Silurian beds along 
 
218 PALEOZOIC TIME. 
 
 a region extending southwestward from Lake Erie over Cin- 
 cinnati through Kentucky, which area was partly an emerged 
 peninsula or island through the rest of Paleozoic time. 
 
 In Great Britain and Europe also there were disturbances 
 at the close of the Lower Silurian. The range of Southern 
 Scotland has been referred to this epoch, and so also the 
 Westmoreland Hills, and mountains in North Wales, and 
 hills in Cornwall. 
 
 3. Life. There is no evidence that the system of life in 
 its progress during the Lower Silurian had so far advanced as 
 to include a terrestrial animal, or the lowest of Vertebrates. 
 Trilobites held the first position in the Primordial Period, Or- 
 thocerata and other Cephalopods in the Trenton. Among 
 Articulates there were neither Myriapods, Spiders, nor In- 
 sects as far as discovered ; for these are essentially terrestrial 
 animals, and the first species of them thus far found are of 
 Devonian age. 
 
 Among the genera of the Lower Silurian, only five have 
 living species. These are Lingula, Discina, Rhynchonella, and 
 Crania among Brachiopods, and Nautilus among Cephalopods. 
 The Linfjulcc of the Primordial are referred to another genus ; 
 but true species of the genus Lingula are reported from the 
 Trenton. These genera of long lineage thus reach through 
 all time from the Lower Silurian onward. All other genera 
 disappear, some at the close of the Primordial, others at 
 that of the Canadian or Trenton period, and some at the ter- 
 mination of subordinate epochs within these periods. 
 
 The extermination of species took place at intervals 
 through the periods, as well as at their close ; though those 
 at the latter were most universal. With the changes from 
 one stratum to another there were disappearances of some 
 species, and with the changes from one formation to another 
 still larger proportions became extinct. No Primordial spe- 
 cies are known to occur in the Canadian period ; very few of 
 the species of the Canadian period survive into the Trenton ; 
 and very many of those of the early part of the Trenton did 
 
UPPER SILURIAN. 219 
 
 not exist in the later part. Thus life and death were in pro- 
 gress together, species being removed, and other species ap- 
 pearing as time moved on. 
 
 3. Upper Silurian Era. 
 I. Subdivisions. 
 
 The Upper Silurian era in North America includes four 
 periods : the NIAGARA, the SALINA, the LOWER HELDERBERG, 
 and the ORISKANY. The name of the first is from the Niagara 
 River, along which the rocks are displayed ; that of the second, 
 from Salina in Central New York, the beds being the salt- 
 bearing rocks of that part of the State; that of the third, 
 from the Helderberg Mountains, south of Albany, where the 
 lower rocks are of this period ; that of the fourth, from Oris- 
 kany, a place in Central New York, northwest of Utica. 
 
 2. Rocks: Kinds and Distribution. 
 
 The rocks of the Niagara period are : 1. A conglomerate 
 and grit-rock called the Oneida conglomerate, which extends 
 from Central New York southward along the Appalachian 
 region, having a thickness of 700 feet in some parts of Penn- 
 sylvania ; together with shaly sandstones of the Medina group, 
 which spread westward from Central New York through 
 Michigan, and also southward along the Appalachian region, 
 being 1,500 feet thick in Pennsylvania; 2. Hard sandstones, 
 or flags and shales of the Clinton group, having nearly the 
 same distribution as the Medina formation, though a little 
 more widely spread in the west, and about 2,000 feet thick 
 in Pennsylvania ; 3. The Niagara group, occurring in Western 
 New York, and extending widely over both the Appalachian 
 and Interior Continental regions : it consists, at Niagara, of 
 shales below and thick limestone above ; mainly of limestone 
 in the Interior region ; and of clayey sandstone or shales in 
 the Appalachian region, where it has a thickness of 1,500 
 feet or more. The Niagara is one of the great limestone 
 
PALEOZOIC TIME. 
 ns of the continent, existing also in the Arctic 
 
 Eipple-marks and mud-cracks are very common in the 
 Medina formation. The example of rill-marks figured on 
 page 46 is from its strata in Western New York. 
 
 The Salina rocks are fragile, clayey sandstones, marlytes, 
 and shales, usually reddish in color, and including a little 
 limestone. They occur in New York and sparingly to the 
 westward, being thickest (700 to 1,000 feet thick) in Onon- 
 daga County, New York. 
 
 The salt of Salina and Syracuse, in Central New York, is 
 obtained from wells of salt water 150 feet and upward in 
 depth, which are borings into these saliferous rocks. From 35 
 to 45 gallons of the water afford a bushel of salt, while of 
 sea-water it takes 350 gallons for the same amount. No solid 
 salt is there found; but farther west, near Wyoming and 
 Warsaw, N. Y., a bed, 50 to 100 feet thick, occurs at a depth 
 of 1,200 to 1,500 feet; and near Goderich, in Canada, at a 
 depth of about 1,000 feet, a bed 14 to 40 feet thick. Gypsum 
 is common in some of the beds. 
 
 The Lower Heldcrberg group consists mainly of limestones, 
 and is the second limestone formation of the Upper Silurian. 
 The formation is well developed in the State of New York 
 and along the Appalachian region to the south ; it also occurs 
 in Ohio, Indiana, Southern Illinois, and Tennessee ; also 
 
 Fig. 213. 
 
 w 
 
 Section along the Niagara, from the Falls to Lewlston Heights. 
 
 along the Connecticut Valley, in Northern Maine, and in 
 New Brunswick and Nova Scotia. 
 
 The section, Fig. 213, represents the rocks on the Niagara 
 
UPPER SILURIAN. 221 
 
 River at and below the Falls. The Falls are at F ; the whirl- 
 pool, three miles below, at W ; and the Lewiston Heights, 
 which front Lake Ontario, at L. Nos. 1, 2, 3, 4 are different 
 sandstone strata belonging to the Medina group; 5, shale, 
 and 6, limestone, to the Clinton group ; 7, shale, and 8, lime- 
 stone, to the Niagara group. The next section (Fig. 214), 
 
 Fig. 214. 
 
 G 
 Section of the Salina and underlying strata, from north to south, south of Lake Ontario. 
 
 from the region south of the eastern part of Lake Ontario, 
 consists as follows : 5 b, Medina group, 5 c, Clinton group, 
 5d, Niagara group (shale and limestone), G, Salina beds. 
 (Hall.) 
 
 The Oriskany beds are mostly rough sandstones. The for- 
 mation extends from Oriskany, New York, southward along 
 the Appalachian region through Pennsylvania, Maryland, and 
 Virginia, where it is several hundred feet thick. It occurs 
 also in Northern Maine, and at Gasp4 on the Gulf of St. 
 Lawrence, where the rock is partly limestone. 
 
 In Great Britain the Upper Silurian rocks are first sand- 
 stones and shales, called, where occurring in South Wales, 
 Llandovery beds, and corresponding to the Medina and Clin- 
 ton groups. Above these there is the Wenlock limestone 
 group, consisting of limestone and some shale (and including, 
 in the upper portion, the Dudley limestone). These rocks 
 occur as surface-rocks near the borders of Wales and England. 
 Next comes the Ludlow group, of the age of the Lower Hel- 
 derberg and Oriskany beds. 
 
 In Scandinavia the Gothland limestone is the equivalent 
 of the Niagara. 
 
 3. Life. 
 
 The limestone strata and most of the other beds of the 
 Niagara group are full of fossils ; and so also are the rocks of 
 
222 
 
 PALEOZOIC TIME. 
 
 the Lower Helderberg period, and of the Wenlock and Lud- 
 low formations in Great Britain. Nearly all of the Salina 
 formation is destitute of them. 
 
 The life of the era was the same in general features as that 
 of the latter half of the Lower Silurian, though mostly dif- 
 ferent in species. 
 
 Figs. 215-227. 
 215 
 
 219 
 
 RADIATES: Fig. 215, Zaphrentis bilateralis, Clinton group ; 216, Favosites Niagarensis, 
 Niagara group ; 217, Halysites catenulata, id. ; 218, Caryocrinus ornatus, id. MOL- 
 LUSKS : Fig. 219, Peritainerus oblongus, Clinton gr. ; 220, Ortuis varica(x 2), Niagara 
 gr.j and Dudley limestone ; 221, Leptsena transversalis, id. ; 222, Strophomena rhomboida- 
 lis, id. ; 223, Rhynchotreta cuneata, U. S. and Great Britain, id. ; 224, Pterinea emacerata. 
 Niagara gr. ; 225, Cyclonema cancellata, Clinton gr. ; 226, Platyceras, angulatum, Niagara 
 gr. ARTICULATES : Fig. 227, Homalonotus delphinocephalus, id. 
 
 The only plants yet found in the Lower Helderberg and 
 underlying beds are Algce, or Sea-weeds ; but in the Oriskany 
 
UPPER SILURIAN. 223 
 
 beds of Gaspe are found remains of true terrestrial species, re- 
 lated to the Lycopods or modern Ground-pine. They were 
 about as large as the common Lycopodium dendroideum of the 
 present day. (Seepage 188.) Similar remains of plants have 
 been found also in the Upper Ludlow beds of Great Britain. 
 
 In the Animal Kingdom the sub-kingdom of Radiates was 
 represented most prominently by Corals and Crinoids; that 
 of Mollusks, by species of all the grand divisions, among which 
 the Brachiopod and Orthoceras tribes were the most character- 
 istic; and especially the Brachiopod, whose shells far outnum- 
 ber those of all other Mollusks ; that of Articulates, by Worms, 
 Ostracoids, and Trilobites; and, before the close of the era, by 
 the new form of Crustaceans represented in Fig. 235. 
 
 1. Radiates. Fig. 215 is a polyp-coral of the Cyatlwphyl- 
 loid tribe, showing the radiating plates of the interior ; Fig. 
 216, a species of Favositcs, a genus in which the corals have a 
 columnar structure (somewhat honey comb -like, whence the 
 name from the Latin favus, honeycomb), and horizontal parti- 
 tions subdivide the cells within; Fig. 217, Haly sites catenulata, 
 called chain-coral ; Fig. 218, a Crinoid, Caryocrinus ornatus, 
 the arms at the summit broken off; Fig. 164, page 183, another 
 Crinoid of the family of Cystideans, from the Niagara group ; 
 Fig. 162, page 183, a star-fish, also from the Niagara group. 
 
 2. Mollusks. Figs. 219 to 223, different Brachiopods of 
 the Niagara period; Figs. 228 to 234, other species charac- 
 teristic of the Lower Helderberg period ; Figs. 225, 226, Gas- 
 teropods; and Fig. 224, a Lamellibranch of the Niagara period. 
 Fig. 233 represents small slender tubular cones, called Tcntac- 
 ulites, which almost make up the mass of some layers in the 
 Lower Helderberg; the form of one enlarged is shown in Fig. 
 234; they are regarded as the shells of Pteropods. 
 
 3. Articulates. Fig. 227 is a reduced figure of a common 
 Trilobite of the Niagara group, a species of Homalonotus, 
 often having a length of 8 or 10 inches. Fig. 235 repre- 
 sents Eurypterus remipes, a species of a family of Crustaceans, 
 occurring first in the Utica shale ; it is sometimes nearly 
 
224 
 
 PALEOZOIC TIME. 
 
 a foot long. 
 
 Species of the same family occur in Great 
 Britain in the Ludlow beds, and one of them is supposed, 
 from the fragments found, to have been 6 or 8 feet long, 
 far surpassing any Crustacean now living; Fig. 236, an 
 Ostracoid Crustacean, the Lcperditia alta, of unusually 
 large size for the family, modern Ostracoids seldom exceed- 
 ing a twelfth of an inch in length. 
 
 Figs 228-236 
 
 MOLLUSKS : Figs. 228, 229, Pentamerus galeatus ; 230, 231, Rhynchonella ventricosa ; 
 232, Spirifer macropleurus ; 233, Tentaculites irregularis ; 234, id enlarged. ARTICU- 
 LATES : Fig. 235, Eurypterus remipes, a small specimen ; 236, Leperditia alta. Species 
 all from the Lower Helderberg group. 
 
 4. Vertebrates. The first remains of Vertebrates yet dis- 
 covered occur in the Upper Silurian. They are of fishes, and 
 have been found in the Ludlow beds of Great Britain. They 
 are teeth, scales, and other relics, chiefly of shark-like species. 
 The kinds are further described under the Devonian. 
 
 4. General Observations. 
 
 1. Geography, On the map, page 195, the areas over which 
 the Silurian formations are surface-rocks are distinguished by 
 
UPPEK SILURIAN. 225 
 
 being horizontally lined. It is observed that they spread 
 southward from the northern Archaean area, and indicate an 
 extension in that direction of the growing continent. 
 
 South of the Silurian area commences the Devonian, which 
 is vertically lined; and the limit between them shows ap- 
 proximately the course of the sea-shore at the close of the 
 Silurian age. It is seen that more than half of New York, 
 and nearly all of Canada and Wisconsin, had by that time 
 become part of the dry land ; but a broad bay covered the 
 Michigan region to the northern point of Lake Michigan, 
 for here Devonian rocks, and to some extent Carboniferous, 
 were afterward formed. The Archaean dry land, the nucleus 
 of the continent, had also received additions in a similar 
 manner on its eastern and western sides, through British 
 America.* 
 
 But, with all the increase, the amount of dry land in North 
 America was still small. Europe is proved by similar evi- 
 dence to have had much submerged land. The surface of the 
 earth was a surface of great waters, with the continents only 
 in embryo, one large area and some islands representing 
 that of North America, and an archipelago that of Europe. 
 The emerged land, moreover, was most extensive in the 
 higher latitudes. The rivers of a world so small in its lands 
 must also have been small. The lands, too, according to 
 present evidence, had no green sward over the rocks, except 
 during the closing part of the Silurian age. 
 
 The succession of Upper Silurian formations is as follows : 
 1. The Medina sandstone having at base the coarse grit called 
 Oneida conglomerate, occurring of great thickness along the 
 Appalachian region, and reaching north to Central New York, 
 
 * On the map referred to, page 195, lines of the Silurian and Devonian are 
 seen to extend from the Hudson River southwestward along the Appalachian 
 region. But the outcrop of the Silurian, here represented, is not evidence 
 that there was a strip of dry land along this region from the close of the Silu- 
 rian era, because there is proof that these Appalachian outcrops are a conse- 
 quence of the uplift of the Alleghany Mountains, an event of much later 
 date. (Page 277.) 
 
 15 
 
226 PALEOZOIC TIME. 
 
 and, besides, spreading westward beyond the limits of that 
 State ; ' 2. The Clinton group of flags and shales, having 
 the same Appalachian extension and great thickness, but 
 spreading on the north much farther westward, even to the 
 Mississippi; 3. The Niagara group, covering the Appalachian 
 region deeply with sandstones and shales, and New York with 
 shales and limestones, and spreading as a great limestone 
 formation through the larger part of the Interior region; then 
 (4) the limited Salina salt-bearing marlytes of New York, ex- 
 tending west through Canada, and over part of the Appala- 
 chian region southwest ; then (5) another limestone, but im- 
 pure, spreading over New York State and the Appalachian 
 region, and also some of the States west ; and also occurring 
 in the Connecticut Valley and over Maine to the Gulf of St. 
 Lawrence. These facts teach that geographical changes took 
 place from time to time, in the course of the era, corresponding 
 to these several changes in the formations. The clear conti- 
 nental seas of the Trenton period were succeeded by con- 
 ditions fitted to produce the several arenaceous and argilla- 
 ceous formations, of varying limits, which followed ; but clear 
 waters returned again at the epoch of the Niagara group, when 
 corals, crinoids, and shells covered the bottom of the conti- 
 nental sea and made the Niagara limestone formation. But 
 these seas in the Niagara epoch were less extended than those 
 of the Trenton ; for the Appalachian region, instead of being 
 part of the pure sea and making limestones, was receiving 
 great depositions of sand and clay, as if it were at the time 
 a broad reef, or bank, border' ig the Atlantic Ocean. 
 
 The Niagara epoch of limestone-making was followed by 
 the Salina or saliferous period. Since the beds are (1) clays 
 and clayey sands, (2) are almost wholly without fossils, arid 
 (3) afford salt, it may be inferred that Central New York was 
 at the time a great salt marsh, mostly shut off from the sea. 
 Over such an area the waters would at times have become too 
 salt to support life, owing to partial evaporation under the 
 hot sun, and too fresh at other times, from the rains. More- 
 
UPPER SILURIAN. 227 
 
 over, muddy deposits would have been formed ; for they are 
 now common in salt marshes wherever there is, as there was 
 then, no covering of vegetation, and the salt waters would 
 naturally have yielded salt on evaporation in the drier sea- 
 sons. Through an occasional ingress of the sea, the salt 
 waters might have been resupplied for further evaporation. 
 
 There is direct testimony as to the condition of the land 
 and shallowness of the waters in the regions where many 
 of the rocks were in progress; for ripple-marks and mud- 
 cracks are common in some layers, and are positive evidence 
 that the sands and earth that are now the solid rock were 
 then the loose sands of beaches, sand-flats, or sea-bottoms, or 
 the mud of a salt marsh. Such little markings, therefore, 
 remove all doubt as to the condition of Central New York in 
 the Salina period. 
 
 Similar markings indicate, also, the precise condition of 
 the region of the Medina sandstone, showing that there were 
 sand-flats, sea-beaches, and muddy bottoms open to the in- 
 flowing sea. Where the rill-marks were made (Fig. 24, page 
 46) the sands of the spot were those of a gently sloping flat 
 or beach ; the waters swept lightly over the sands, dropping 
 here and there a stray shell (as the Lingula cuneata) or a 
 pebble, which became partly buried; and then, as they 
 retreated, they made a tiny plunge over the little obstacle 
 and furrowed out the loose sand below it. The fineness of 
 the sand, lightness of the shells, and smallness of the furrows 
 are proof that the movements were light. 
 
 The great thickness of the several formations of the Upper 
 Silurian along the Appalachian region leads to many inter- 
 esting conclusions. It has been stated (page 217) that the 
 Appalachian formations of the earlier Silurian were equally 
 remarkable for their great thickness. The Appalachian re- 
 gion, from the Primordial era onward, was, hence, in strong 
 contrast with the Interior Continental region, where the 
 series of cotemporaneous beds are hardly one tenth as thick. 
 Taking this into connection with another fact, that very 
 
228 PALEOZOIC TIME. 
 
 many of the strata among the thousands of feet of Silurian 
 formations in the Appalachian region contain those evidences 
 of shallow water and mud-flat or sand-flat origin above ex- 
 plained, there is full proof that in the Silurian era the region 
 was for the most part, as already suggested, a vast sand-reef, 
 ever increasing by new accumulations under the action of the 
 waves and currents of the ocean. It was much of the time a 
 great barrier-reef lying between the open ocean and the Inte- 
 rior Continental sea ; and under its lee, this inner sea, opening 
 southward through the area of the Mexican Gulf, was often 
 in the best condition for the growth of the Shells, Corals, and 
 Crinoids of which the great limestones were made. 
 
 While the Appalachian region was alike in its general con- 
 dition through the earlier and later Silurian, the limits of the 
 formations in progress during these two eras were somewhat 
 different, as explained on page 217. The part of the Appala- 
 chian region which participated, during the Upper Silurian 
 era, in the great changes connected with the formation of 
 rocks, extended northward from Pennsylvania. into New York, 
 and not along the Green Mountains ; the rocks in the State 
 of New York have great thickness for some distance beyond 
 the Pennsylvania border, but thin out about the centre. 
 
 2. Life. In the Upper Silurian the highest species of the 
 seas and of the world continued for a while to be Mollusks, 
 of the order of Cephalopods. But before its close there were 
 fishes in the waters, and Vertebrates ever afterward existed as 
 the highest species. Corals and Crinoids were the only kinds 
 of life that had the semblance of flowers. These flower-ani- 
 mals foreshadowed the flowers of the vegetable kingdom for 
 ages before any of the latter existed. The Lycopods of the 
 later part of the Upper Silurian were flowerless plants, like 
 the Ferns. 
 
 Up to 1872, over 10,000 species of Silurian animals 
 ranging from Sponges to Fishes had been made known 
 through the study of fossils. 
 
DEVONIAN AGE. 229 
 
 II. AGE OF FISHES, or DEVONIAN AGE. 
 I. Subdivisions. 
 
 The Devonian formation was so named by Sedgwick and 
 Murchison, from Devonshire, England, where it occurs. 
 
 The Age may be divided into two eras, - an earlier and a 
 later, or that of the lower and that of the upper formations. 
 The Lower Devonian includes the CORNIFEROUS period ; the 
 Upper Devonian, the HAMILTON, CHEMUNG, and CATSKILI 
 periods. 
 
 2. Rocks: Kinds and Distribution. 
 
 1. Earlier and Later Eras. The Lower Devonian is remark- 
 able for a great limestone formation, which spread from New 
 York over a large part of the Interior region, and nearly 
 equalled the Trenton in extent; while the Upper includes 
 very little limestone, the rocks being mainly sandstones, 
 shales, and conglomerates. 
 
 2. Corniferous Period. The lowest rocks of this period are 
 fragmental beds, called the Cauda-Galli grit and the ScJio- 
 harie grit, having their distribution along the Appalachian 
 region, commencing in Central and Eastern New York and 
 extending southwestward. 
 
 Next follows the great Corniferous limestone, the lower 
 part of which is sometimes called the Onondaga limestone, 
 and the whole often the Upper Helderberg group. It stretches 
 from Eastern New York westward to the States beyond the 
 Mississippi. 
 
 The name Corniferous (derived from the Latin cornu, horn) 
 was given it by Eaton, from its frequently containing a kind 
 of flint called hornstone. This hornstone differs from true 
 flint in being less tough, or more splintery in fracture, though 
 it is like it in hardness and in consisting wholly of silica. 
 
 The limestone is in many places literally an ancient coral 
 reef. It contains corals in vast numbers and of great variety ; 
 
230 PALEOZOIC TIME. 
 
 and in some places, as at the Falls on the Ohio, near Louis- 
 ville, Kentucky, the resemblance to a modern reef is perfect. 
 Some of the coral masses at that place are 5 or 6 feet in di- 
 ameter ; and single polyps of the Cyathophylloid corals had 
 in some species a diameter of 2 and 3 inches, and in one, of 6 
 or 7 inches. 
 
 The same reef-rock occurs near Lake Memphremagog on 
 the borders of Vermont and Canada, and also at Littleton, 
 New Hampshire; but the corals have in these places been 
 partly obliterated by metamorphism. 
 
 3. Hamilton Period. The Hamilton formation consists in 
 New York of sandstones and shales, with a few thin layers of 
 limestone. It consists of three parts, corresponding to three 
 epochs : the lower part is called the Marcellus shale ; the 
 middle, the Hamilton beds ; and the upper, the Genesee shale. 
 It has its greatest thickness along the Appalachians. From 
 New York it spreads westward, where it is in part calcareous, 
 and forms the upper part of the "cliff" limestone. It in- 
 cludes a stratum of black shale (supposed to be of the epoch 
 of the Genesee shale), 100 to 350 feet thick, which yields in 
 some places 15 to 20 per cent of mineral oil. The formation 
 occurs also in Eastern Maine, New Brunswick, and at Gaspe, 
 on the Gulf of St. Lawrence. 
 
 The Hamilton beds afford an excellent flagging-stone in 
 Central New York, and on the Hudson River, near Kingston, 
 Saugerties, Coxsackie, and elsewhere, which is extensively 
 quarried and exported to other States. 
 
 4. Chemung Period. The Chemung beds are mainly sand- 
 stones, or shaly sandstones, with some conglomerate. They 
 spread over a large part of Southern and Western New York, 
 having great thickness in the Catskill Mountains. A shale 
 of the period in Northern Ohio is called the Erie shale. 
 
 The formation along the Appalachians is 5,000 feet thick. 
 It thins out to the west of New York, in Ohio, and Michigan. 
 
 In the following section, taken on a north-and-south line 
 south of Lake Ontario, No. 6 represents the beds of the 
 
DEVONIAN AGE. 231 
 
 Salina period ; overlaid by 7, the Lower Helderberg lime- 
 stone ; 9, the Corniferous, or Upper Helderberg limestone ; 
 10, a, b, c, the Hamilton beds; and 11, the Cheinung group. 
 
 Fig. 237 
 
 1 1 
 
 (T 7 = 9 10 a 
 
 Section of Devonian formations south of Lake Ontario. 
 
 5. Catskill Period. The rocks are sandstones, shaly sand- 
 stones, and shales ; they occur in Eastern New York, and are 
 2,000 to 3,000 feet thick in the Catskill Mountains. They 
 also extend southwestward along the Appalachians, being 
 5,000 to 6,000 feet thick in Pennsylvania. 
 
 In Great Britain the Devonian rocks include the Old Red 
 Sandstone, the prevailing rock of the age in Wales and Scot- 
 land. The thickness in some places is 8,000 to 10,000 feet. 
 This formation, besides sandstone, includes marly tes of red and 
 other colors, and some limestone. The distribution in Great 
 Britain is shown on the map, page 244. In Germany, in the 
 Rhenish provinces, there is a coral limestone very similar to 
 that of North America. 
 
 3. Life. 
 1. General Characteristics. 
 
 The Devonian of North America was characterized by 
 forests and an abundance of insects over the land, and 
 by fishes of many kinds in the waters. 
 
 2. Plants. 
 
 Figs. 238-240 represent portions of some of the plants. 
 Fig. 240 is a fragment of a Fern, and Figs. 238, 239, portions 
 of the trees, of the age. The scars or prominences over the 
 surface are the bases of the fallen leaves ; a dried branch of 
 a Norway spruce, stripped of its leaves, looks closely like 
 Fig. 239. By referring to page 186, it will there be seen that 
 
232 
 
 PALEOZOIC TIME. 
 
 among the Cryptogams there is one order, the highest, or 
 that of Acrogens, in which the plants have upward growth 
 
 Figs. 238-240 
 
 PLANTS. Fig. 238, Lepidodendron primsevum, from the Hamilton group ; 239, Sigillaria 
 Hallii, ibid. ; 240, Noeggerathia Halliana, from the Chemuug group. 
 
 like ordinary trees, and the tissues are partly vascular : it is 
 the one containing the Ferns, Lycopods, and Equiseta or Horse- 
 tails. The most ancient of land plants belong, to a great ex- 
 tent, to this order, the highest of Cryptogams, and were of 
 the three kinds just mentioned. Another portion are related 
 to the lowest order of flower-bearing plants or Phenogams, 
 called Gymnosperms (see page 188). 
 
 The groups represented under these divisions are the fol- 
 lowing: 
 
 I. Flowerless Plants, or Cryptogams, Order of 
 Acrogens. 
 
 1. Fern Tribe. The species have a general resemblance to 
 the ferns or brakes of the present time. 
 
 2. Lycopods, or plants related to the Ground-Pine. The 
 existing plants of this tribe are slender species, seldom over 4 
 or 5 feet high : some of the ancient kinds were of the size of 
 
DEVONIAN AGE. 233 
 
 forest-trees. These ancient species belong mostly to the Lepi- 
 dodendron family, in which the scars are contiguous and are 
 arranged in quincunx order, that is, alternate in adjoining 
 rows, as shown in Fig. 238. The name Lepidodendron is 
 from the Greek Xevrt?, scale, and Sev&pov, tree, and alludes to 
 the scar-covered trunk, which looks something in surface like 
 a scale-covered reptile. The Ground-Pine of modern woods, 
 although flowerless like the fern, has leaves very similar to 
 those of the Spruce or Cedar (Conifers) ; and this type of 
 plants is intermediate in some respects between the Aero- 
 gens and Gymnosperms (Conifers). 
 
 The Sigillarids, another family in this tribe, included trees 
 of moderate height, with stout, sparingly branched trunks, 
 bearing long linear leaves much like those of the Lepidoden- 
 drids ; but the scars on the exterior are mostly in parallel 
 vertical lines, as in Fig. 239, and Fig. 283, page 251, and not 
 in quincunx order, like those of the Lepidodendra. The name 
 is from the Latin sigillum, a seal, in allusion to the scars. 
 
 3, Equisetum, or Horse-tail Tribe. The Equiseta of mod- 
 ern wet woods are slender, hollow, jointed rushes, called 
 sometimes scouring-rushes. They often have a circle of slen- 
 der leaf-like appendages at each joint. The Calamites or Tree- 
 rushes, which are referred to this tribe, are peculiar to the 
 ancient world, none having existed since the Mesozoic. They 
 had jointed striated stems like the Equiseta, and otherwise 
 resembled them. But they were often a score of feet or more 
 in height, and over 6 inches in diameter. Some of them had 
 hollow stems like the Equiseta ; others had the interior of the 
 stems partially woody, and these were intermediate in some 
 respects between the Equiseta and the Gymnosperms. Fig. 
 286, page 251, represents a portion of one of these plants. 
 
 II. Flowering Plants, or Phenogams, of the Order 
 of Gymnosperms. 
 
 Conifers. The species are related to the common Pines 
 and Spruces, or more nearly to the Araucanian Pines of Aus- 
 
234 
 
 PALEOZOIC TIME. 
 
 tralia and South America. The fossils are merely portions of 
 the trunk or branches. 
 
 Conifers, Ferns, and Lepidodendrids have also been reported. 
 from some of the Devonian beds of Britain and Europe. 
 
 The hornstone, which is massive quartz, or silica, develops, 
 under the microscope, the fact that it was probably made 
 from the siliceous remains of plants and animals. Figs. 241 
 to 255 represent some of the species which have been detected 
 by Dr. M. C. White in specimens from New York and else- 
 where. Figs. 241 to 247 are microscopic plants, related to 
 
 Figs. 241-255. 
 
 241 
 
 2f,t 
 
 Microscopic Organisms from the Hornstone. 
 
 the Dcsmids ; Fig. 248 is another kind, called a Diatom, a 
 kind which forms siliceous shells, and which is probably one 
 of the sources of the silica of which the hornstone was made. 
 (See, on Diatoms and Desmids, pages 68 and 187.) Figs. 
 249, 250 are spicules of Sponges, also siliceous, and another 
 of the sources of the silica. Figs. 251, 252 are probably also 
 sponge-spicules. Figs. 254, 255 are fragments of the teeth 
 of some Gasteropod Mollusk. The last is from a hornstone 
 of the Trenton period which was found to afford the same 
 evidences of organic origin. 
 
 3. Animals. 
 
 The early Devonian was the coral period of the ancient 
 world. In no age before or since, not even the present, have 
 coral reefs of greater extent been formed. 
 
 Among Mollusks, Brachiopods were still the prevailing 
 kinds, though ordinary Bivalves or Lamellibranchs, and 
 
DEVONIAN AGE. 
 
 235 
 
 Univalves or Gasteropoda, were more abundant than in 
 the Silurian. A new type of Cephalopods commenced in the 
 Middle Devonian. Hitherto, the partitions or septa in the 
 shells, straight or coiled, were flat or simply concave; but 
 in the new genus Goniatites the margin of the plate has one 
 or more deep flexures, one of the flexures or pockets being at 
 the middle of the back of the shell. The name is from the 
 Greek yow, knee or. angle, fig. 266 (page 236) represents 
 one of the species, and Fig. 266 a shows some of the flexures 
 along the back of the shell. 
 
 Among Articulates there were Worms and Crustaceans, as 
 in earlier time, and the most common Crustaceans were Trilo- 
 bites. Besides these there were the first of Insects, the wings 
 of some species having been reported from the Devonian of 
 New Brunswick. 
 
 Figs. 256-260. 
 
 RADIATES, Pig. 256, Zaphrentis Rafinesquii ; 257, 257 a, Cyathophyllum rugosum : 
 258, Syringopora Maclurii ; 25 ( J, Aulopora cornuta ; 260, Favorites Goldfussi ; all of the 
 Corniferous period. 
 
 1, Radiates. Fig. 256, one of the Cyathophylloid corals, 
 Zaphrentis Rafinesquii ; Fig. 257, another, Cyathophyllum ru- 
 gosum, both from the Falls of the Ohio, and the latter form- 
 ing very large masses. Fig. 257 a is a top view of the cells 
 in Fig. 257. Fig. 260, a Favositcs from the same locality, 
 showing well the columnar structure characterizing the genus ; 
 
236 
 
 PALEOZOIC TIME. 
 
 the species F. Goldfussi occurs both in America and Europe 
 Figs. 258, 259 are small corals from Canada West. 
 
 2. MoUusks. Figs. .261 to 267, Brachiopods from the 
 Hamilton beds; Figs. 264, 265, Lamellibranchs, from the 
 
 2(31 
 
 Figs. 261-267- 
 
 MOLLUSKS : Fig. 261, Atrypa spinosa ; 262, Spirifer mucronatus ; 263, Chonetes setigera * 
 264, Graminysia bisuloata; 235, Microdon bellistriatus ; 266, 263 a, Goniatites Marcel- 
 lensis : all from the Hamilton group. ARTICULATES : Fig. 267, Phacops bufo, from 
 the Hamilton group. 
 
 same ; Fig. 266, the Cephalopod, Goniatites Marccllensis, from 
 the same ; Fig. 266 , a view of the back, showing the flex- 
 ures in the partitions, this species having but one flexure 
 or pocket. 
 
 3. Articulates.. Fig. 267, the Trilobite, Phacops bufo, one 
 of the common species of the Hamilton. The earliest re- 
 mains of Insects yet discovered have been found in beds 
 
DEVONIAN AGE. 
 
 237 
 
 Fig- 268 
 
 supposed to be of the Hamilton era, at St. John's, New 
 Brunswick. A wing of a gigantic species of May-fly is 
 represented in Fig. 268. 
 
 4, Vertebrates. The fishes 
 of the Devonian belong to 
 three orders : 1. the Selachians, 
 or Sharks; 2. the Ganoids; and 
 3. the Placoderms. The Placo- 
 dcrms are represented in Figs. 
 269, 270. The name, from the 
 Greek, alludes to the plates 
 that cover the body much like those of a turtle. 
 
 Some of the Ganoids are shown in Figs. 271-276. The 
 
 Figs. 269, 270. 
 
 Platephemera antiqua. 
 
 VERTEBRATES. Fig. 269, Pterichthys Milled (X ) ; 270, Coccosteus decipiens (X 
 
 Ganoids are related to the Gar-pike of some modern lakes 
 and rivers, a kind of fish now rarely met with. They have 
 bony, shining scales, and to this the name, from yavos, shin- 
 ing, alludes. As remarked by Agassiz, they have several 
 
238 
 
 PALEOZOIC TIME. 
 
 characters that aUy them to Eeptiles ; that is, (1) they have 
 the power of moving the head at the articulation between the 
 head and the body, the articulation being made by means of 
 a convex and concave surface ; (2) the air-bladder, which an- 
 swers to the lung of higher animals, has a cellular or lung- 
 
 Figs. 271-276. 
 271 
 
 GANOIDS. Fig. 271, Cephalaspis Lyellii (X |) ; 272, 273, scales of same ; 274, Holopty- 
 chius (X ) ; 275, scale of same; 276, Dipterus macrolepidotus ( X i); 276 a, scale ol 
 same. 
 
 like structure, thus approximating the species to air-breathers ; 
 (3) the teeth have in general a structure like that of the early 
 Amphibians. These early species had the tail vertebrated (or 
 heterocercal), as illustrated in Fig. 276. Fig. 271 represents 
 the Cephalaspis, having a flat and broad plate-covered head, 
 with rhombic scales over the body: Fig. 273 shows the 
 
DEVONIAN AGE. 239 
 
 form of some of the scales. Fig. 276 is a species of Dip- 
 ierus, covered with rhombic scales, put on, as in the pre- 
 ceding, much as tiles are arranged on a roof: Fig. 276 a 
 is one of the scales, natural size. Fig. 274 represents another 
 type of Ganoids, having the scales rounded (as shown in Fig. 
 275) and set on more like shingles; it is a Holoptychius. 
 
 A gigantic Placoderm from Ohio, called Dinichthys by 
 Newberry, had a head four feet wide, with dentate lower jaws 
 twenty inches long. It was related to the Coccosteus, and also, 
 according to its describer, to the modern Lepidosiren. 
 
 The Selachians, or sharks, belong in part to the family of 
 Cestracionts (pages 178, 179), or that in which the mouth has 
 a pavement of broad bony pieces for grinding. Others had 
 regular teeth, somewhat like those of ordinary sharks ; in one 
 
 Fig. 277- 
 
 Fin-spine of a Shark (x ). 
 
 group (the Hybodonts) the teeth had prominent points (Figs. 
 136, 137, page 178), and in another they were of a broad trian- 
 gular shape. There were species as large as the largest of mod- 
 ern time. Fig. 277 represents a fin-spine of a shark two thirds 
 its actual size, from the Corniferous beds of New York. 
 
 4. General Observations. 
 
 1. Geography. During the Silurian, there had been a grad- 
 ual gain of dry land on the north, extending the Archaean 
 continent (page 199) south ward. This gain continued through 
 the Devonian, so that the formations of the next age, the Car- 
 boniferous, extend only a short distance north of the southern 
 boundary of New York. The sea-shore was thus being set 
 farther and farther southward with the progressing periods. 
 
 The formations have their greatest thickness along the Ap- 
 palachian region, as in the Silurian age. And both this fact 
 
240 PALEOZOIC TIME. 
 
 and their successions lead to similar general conclusions to 
 those stated on page 228. 
 
 2. Life. The great feature of the Devonian age is the oc- 
 currence of forests of Acrogens and Conifers ; of Insects and 
 Myriapods, among terrestrial Articulates ; and of great Sharks 
 and Gars in the seas, as representatives of Vertebrates. No 
 Mosses are known to have existed as intermediate species 
 between Sea-weeds and the earliest Lycopods and Ferns. 
 
 With regard to Fishes, the earliest species belong to the 
 two high groups of the class, the Sharks and the Ganoids ; 
 the Ganoids being a type that is partly Eeptilian. The rocks 
 have afforded no evidence of any links between the Mollusk, 
 Worm, or Trilobite and these fishes. 
 
 III. CARBONIFEROUS AGE, or AGE OF COAL 
 
 PLANTS. 
 
 I. General Characteristics: Subdivisions. 
 
 The Carboniferous age was remarkable, in general, for 
 
 1. A low elevation of the continents above the sea-level 
 through long eras alternating with small submergences of the 
 same. 
 
 2. Extensive marshy or fresh-water areas over large por- 
 tions of these low continents. 
 
 3. Luxuriant vegetation, covering the land with forests and 
 jungles. 
 
 4. Scorpions, true Spiders, Centipedes, Insects, over the 
 land, and Amphibians and other Reptiles over the marshes 
 and in the seas. 
 
 But, while having these as its main characteristics, it was 
 not an age of continued verdure. There was, first, a long 
 period the Subcarboniferous in which the land was 
 largely beneath the sea ; for limestone, full of marine fossils, 
 is the prevailing rock, and there are but few, and mostly thin 
 coal-beds in the sandstones and shales. This period was fol- 
 lowed by the Carboniferous, or that of the true Coal-measures. 
 
CARBONIFEROUS AGE. 241 
 
 Yet even in this middle period of the age there were alterna- 
 tions of submerged with emerged continents, long eras of dry 
 and marshy lands luxuriantly overgrown with shrubbery and 
 forest- trees intervening between other long eras of great bar- 
 ren continental seas. Then there was a closing period, the 
 Permian, in which the ocean prevailed again, though with 
 contracted limits ; for the rocks are mainly of marine origin. 
 
 The Carboniferous period and age were so named from the 
 fact that the great coal-beds of the world originated mainly 
 during their progress. The term Permian was given to the 
 rocks of the third period by Murchison, De Verneuil, and 
 Keyserling, from a region of Permian rocks in Russia, the an- 
 cient kingdom of Permia, now divided into the governments 
 of Perm, Viatka, Kasan, Orenberg, etc. 
 
 2. Distribution of Carboniferous Rocks. 
 
 The Carboniferous areas on the map of the United States, 
 page 153, are the dark areas ; the black cross-lined with white 
 being the Subcarboniferous ; the pure black, the Carboniferous ; 
 the black dotted with white, the Permian. The last occur 
 only west of the Mississippi. 
 
 The following are the positions of the several great coal 
 areas in North America : 
 
 1. EASTERN BORDER REGION. 1. The Rhode Island area, 
 extending from Newport in Rhode Island northward into 
 Massachusetts. 
 
 2. The Nova Scotia and New Brunswick area. 
 
 II. ALLEGHANY and INTERIOR REGIONS. 1. The great Al- 
 legliany area, extending from the southern borders of New 
 York and Ohio southwestward to Alabama, covering the 
 larger part of Pennsylvania, half of Ohio, part of Kentucky 
 and Tennessee, and a portion of Alabama. To the northeast, 
 in Pennsylvania, this coal-field is much broken into patches,, 
 as shown in the accompanying map of a part of the State, the 
 black areas being those of the coal-district. 
 
 2. The Michigan area, covering the central part of the 
 State ^ f Michigan. 
 
242 
 
 PALEOZOIC TIME. 
 
 3. The Illinois or Eastern Interior area, covering much of 
 Illinois, and part of Indiana and Kentucky. ' 
 
 4. The Missouri, or Western Interior, covering part of Iowa, 
 Minnesota, Missouri, Kansas, Arkansas, and Northern Texas. 
 
 5. Besides these, there is a barren Carboniferous region 
 about the slopes and summits of the Eocky Mountains, as 
 around the Great Salt Lake in Utah, and also in California, 
 the workable coal-beds of the Rocky Mountain region being 
 Cretaceous or Tertiary. 
 
CARBONIFEROUS AGE. 243 
 
 III. ARCTIC KEGION. On Melville Island, and other isl- 
 ands between Grinnell Land and Banks Land, mostly north 
 of latitude 70, and on Spitzbergen and Bear Island north of 
 Siberia. 
 
 The areas of the coal-measures in North America have been 
 estimated as follows : 
 
 1. Rhode Island 500 square miles. 
 
 2. Nova Scotia and New Brunswick . 18,000 " " 
 
 3. Alleghany 60,000 " " 
 
 4. Michigan 5,000 
 
 5. Illinois and Missouri .... 120,000 " " 
 
 But of these, the workable portion probably does not exceed 
 120,000 square miles. 
 
 Carboniferous strata occur also in Great Britain and various 
 parts of Europe. The beds in England are distributed over 
 an area between South Wales on the west and the Newcastle 
 basin on the northeast coast (as shown by the black areas on 
 the following map), the most important for coal being the 
 South Wales region; the Lancashire district, bordering on 
 Manchester and Liverpool ; the Yorkshire, about Leeds and 
 Sheffield ; and the Newcastle. In South Wales the thickness 
 of the coal-measures is 7,000 to 12,000 feet, with more than 
 100 coal-beds, 70 of which are worked. 
 
 Scotland has some small areas between the Grampian 
 range on the north and the Lammermuirs on the south ; and 
 Ireland, several coal-regions of large extent, as at Ulster, Con- 
 naught, Leinster (Kilkenny) and Munster. 
 
 The coal-fields of Europe which are most worked are the 
 Belgian, bordering on and passing into France. Germany 
 contains only small coal-bearing areas ; and Russia in Europe 
 still less, although the Subcarboniferous and Permian rocks 
 cover large portions of the surface. 
 
 The area of the coal-measures in Great Britain and Ireland 
 is about 12,000 square miles; in Spain, 4,000; in France, 
 2,000 ; Belgium, 518. 
 
 Valuable coal-beds are not found in any rocks older than 
 
244 PALEOZOIC TIME. 
 
 those of the Carboniferous age, although black carbonaceous 
 shales are not uncommon even in the Lower Silurian. They 
 occur, however, in different Mesozoic formations, and also 
 
 Fig 279 
 
 Fig. 279, Geological Map of England. The areas lined horizontally and numbered 1 are 
 Silurian. Those lined vertically (2), Devonian. Those cross-lined (3), Subcarboniferous. 
 Carboniferous (4), black. Permian (5). Those lined obliquely from right to left, Triassic 
 (6), Lias (7 a), Oolite (7 ft), Wealden (8), Cretaceous (9). Those lined obliquely from left to 
 right (10, 11), Tertiary. A is London, B, Liverpool, C, Manchester, D, Newcastle. 
 
CARBONIFEROUS AGE. 245 
 
 occasionally in the Cenozoic, but not of the extent which 
 they have in the Carboniferous formations. 
 
 3. Kinds of Rocks. 
 
 1. Subcarboniferous Period. The Subcarboniferous strata 
 in the Interior Continental region are mainly limestone ; and, 
 as the limestone abounds in many places in Crinoidal re- 
 mains, the rock is often called the Crinoidal limestone. In 
 the Appalachian region, in Middle and Southern Virginia, the 
 rock is also limestone, and has great thickness ; but in North- 
 ern Virginia and Pennsylvania it is mostly a sandstone or 
 conglomerate overlaid by a shaly or clayey sandstone and 
 marlytes of reddish and other colors, the whole having a 
 maximum thickness of 5,000 to 6,000 feet. In the Eastern 
 border region, in Nova Scotia, the rocks are mostly reddish 
 sandstone and marlyte, with some limestone, the estimated 
 thickness 6,000 feet. 
 
 The prevailing rock in Great Britain and Europe is a lime- 
 stone, called there the Mountain limestone. 
 
 2. Carboniferous Period. 7. Rocks of the Coal-formation. - 
 The rocks of the Carboniferous period that is, those of the 
 Coal-measures are sandstones, shales, conglomerates, and 
 occasionally limestones ; and they are so similar to the rocks 
 #f the Devonian and Silurian ages that they cannot be distin- 
 guished except by the fossils. They occur in various alter- 
 nations, with an occasional bed of coal between them. The 
 coal-beds, taken together, make up not more than one fiftieth 
 of the whole thickness ; that is, there are 50 feet or more of 
 barren rock to 1 foot of coal. The maximum thickness in 
 Pennsylvania is 4,000 feet ; in Nova Scotia, 13,000 feet. 
 
 The following is an example of the alternations : 
 
 1. Sandstone and conglomerate beds 120 feet. 
 
 2. COAL . . . . . . ' , . . 6 " 
 
 3. Fine-grained shaly sandstone 50 " 
 
 4. Siliceous iron-ore . . . . . . . 1^ " 
 
 5. Argillaceous sandstone .......... 75 " 
 
246 PALEOZOIC TIME. 
 
 6. COAL, upper 4 feet shale, with fossil plants, and below 
 
 a thin clayey layer 7 feet 
 
 7. Sandstone 80 " 
 
 8. Iron-Ore 1 " 
 
 9. Argillaceous shale 80 " 
 
 10. LIMESTONE (oolitic), containing Producti, Crinoids, etc. 11 " 
 
 11. Iron-Ore, with many fossil shells ..... 3 " 
 
 12. Coarse sandstone, containing trunks of trees . . 25 " 
 
 13. COAL, lying on 1 foot slaty shale with fossil plants . 5 " 
 
 14. Coarse sandstone . . . . . . . 12 " 
 
 The limestone strata are more numerous and extensive in 
 the Interior Continental region than in the Appalachian; 
 west of the States of Missouri and Kansas limestone is the 
 prevailing rock. 
 
 Beds of argillaceous iron-ore or clay-ironstone are very com- 
 mon in coal-districts, so that the same region affords ore and 
 the coal for smelting it. Some of the largest iron-works in 
 the world, on both sides of the Atlantic, occur in coal-dis- 
 tricts. The ore is usually the carbonate of iron, impure from 
 mixture with some earth or clay. 
 
 The coal-beds often rest on a bed of grayish or bluish clay, 
 called the under-day, which is filled with the roots or under- 
 water stems of plants. When this under-clay is absent, the 
 rock below is usually a sandstone or shale. Above the coal- 
 bed the rock may be sandstone, shale, conglomerate, or even 
 limestone ; often the layer next above, especially if shaly, is 
 filled with fossil leaves and stems. In some cases, trunks of 
 old trees rise from the coal and extend up through overlying 
 beds, as in the annexed figure, by Dawson, from the Nova 
 Scotia Coal-measures. Occasionally, as in Ohio and Penn- 
 sylvania, logs 50 to 60 feet long lie scattered through the 
 sandstone beds, looking as if a forest had been swept off 
 from the land into the sea. 
 
 2. Coal-Beds. The coal-beds vary in thickness from a 
 fraction of an inch to 30 or 40 feet, but seldom exceed 8 feet, 
 and are generally much thinner : 8 to 10 feet is the thickness 
 of the principal bed at Pittsburg, Pa. ; 29 J feet, that of the 
 
CARBONIFEROUS AGE. 247 
 
 " Mammoth Vein " at Wilkesbarre, Pa. ; 37J feet, that of one 
 of the two great beds at Pictou in Nova Scotia. In these 
 thick beds, and often also in the thin ones, there are some in- 
 tervening beds of shale, or of very impure coal, so that the 
 
 whole is not fit for burning. 
 
 Fig 280. 
 
 Section of a portion of the Coal-measures at the Joggins, Nova Scotia, having erect stumps, 
 and also "rootlets " in the under-clays. 
 
 The coal varies in kind, as explained on page 18, that burn^ 
 ing with little flame being called anthracite, and that with 
 a bright yellow flame bituminous coal. When only 12 or 15 
 per cent of volatilizable substances are present, it is often 
 called semi-bituminous coal. In Pennsylvania the coal of 
 the Pottsville, Lehigh, and Wilkesbarre regions is anthracite : 
 that of Pittsburg and the West, bituminous coal ; and that of 
 part of the intermediate district, semi-bituminous, as desig- 
 nated on the map, page 242. 
 
 The coal also varies as to the impurities present. All of 
 it contains more or less of earthy material, and this earthy 
 material constitutes the ashes and slag of a coal-fire. Ordi- 
 nary good anthracite contains 7 to 12 pounds of impurities 
 in a hundred pounds of coal, and the best bituminous coals 3 
 to 7. In some coal-beds there is much sulphide of iron or 
 pyrite (a compound of sulphur and iron), and the coal is then 
 unfit for use. It is seldom that the sulphide is altogether 
 absent ; it is the chief source of the sulphur gases that are 
 perceived in the smoke or gas from a coal-fire. 
 
248 PALEOZOIC TIME. 
 
 Mineral coal, although it seldom breaks into plates unless 
 quite impure, still consists of thin layers. Even the hardest 
 anthracite is delicately banded, as seen on a surface of frac- 
 ture when it is held up to the light. This structure is absent 
 in the variety called Cannel coal, which is a bituminous coal, 
 very compact in texture, feeble in lustre, and smooth in frac- 
 ture. 
 
 3. Mineral Oil. Besides mineral coal, the rocks sometimes 
 afford, when heated, liquids consisting of carbon and hydro- 
 gen, called ordinarily petroleum or mineral oil, and bitumen ; 
 when purified for burning it becomes kerosene. Oil-wells are 
 largely worked at Titusville, in Pennsylvania, and about 
 Mecca, in Trumbull County, Ohio, regions of Subcarbonif- 
 erous rocks. The wells are borings into an inferior part of 
 the Subcarboniferous formation, or into the upper part of the 
 Devonian. When a boring reaches the oil-level, the oil rises 
 to the surface, and sometimes issues in a jet. The oil is there- 
 fore in subterranean cavities, and under pressure. It has 
 probably reached those cavities from some subjacent region 
 of oil-yielding shales or limestones. These shales, like the 
 Erie shale of the Chemung period, in Ohio, or the black shale 
 of the Genesee epoch of the Hamilton period, or the Utica 
 shale of the Lower Silurian, are black from the carbonaceous 
 material penetrating them ; and although they do not contain 
 any oil (for the solvents of it take up none from them, or but 
 traces), they contain compounds of carbon and hydrogen 
 (probably oxygenated) which, when the shale is heated, yield 
 the oil or liquid carbo-hydrogen. Thus the shales are oil- 
 yielding, though not oil-containing. The regions of wells are 
 mostly along lines of axes of disturbance ; and probably the 
 heat developed by the movement of disturbance caused the 
 production of the oil and its rising into any opened spaces 
 above. Petroleum is a result of the decomposition of vege- 
 table or animal substances. 
 
 4. Salt or Salines. The Subcarboniferous formation in 
 Michigan, in the Saginaw Valley, and in the adjoining region, 
 
CARBONIFEROUS AGE. 249 
 
 affords extensive salines, and many wells have been opened 
 by boring. The beds affording the saline waters consist of 
 clayey beds or marlytes, shale, and magnesian limestone, and 
 abound also in gypsum, thus resembling those of the Salina 
 period in New York (page 220). 
 
 3. Permian period, The upper part of the Carboniferous 
 formation (mostly barren of coal) in Pennsylvania and Vir- 
 ginia has been shown by its plants, and of Illinois, Kansas, and 
 Texas, by its fossil reptiles or mollusks, to be Permian. Per- 
 mian strata occur also in the Pocky-Mountain region. The 
 rocks are mostly reddish and gray sandstones and shales, with 
 some impure limestone. Similar rocks uccur in Great Britain 
 in the vicinity of several of the coal-regions, and also in 
 Germany and Russia. 
 
 4. Life. 
 
 1. Plants. 
 
 The plants of the forests, jungles, and floating islands of 
 the Carboniferous age, thus far made known, number about 
 300 species. Among the fossils there are none that afford 
 satisfactory evidence of the presence of either Angiosperms 
 3T Palms (page 189); for no net- veined leaves, allied in char- 
 acter to those of the Oak, Maple, Willow, Hose, etc., have been 
 found among them ; and no palm-leaves or palm-wood. More- 
 over, the plains were without grass, and the swamps and 
 woods without moss. At the present day Angiosperms, 
 along with Conifers or the Pine family, make up the great 
 bulk of our shrubs and trees ; Palms abound in all tropical 
 countries ; grass covers all exposed slopes where the climate 
 is not too arid ; and mosses are the principal vegetation of 
 most open marshes. 
 
 The view in Fig. 281 gives some idea of the Carboniferous 
 vegetation over the plains and marshes of the era. 
 
 The Carboniferous species, like their predecessors in the 
 Devonian age, belonged to the following groups : 
 
250 
 
 PALEOZOIC TIME. 
 Fig. 281. 
 
jr. ,, v ' '' f -v 
 
 f or Ti-ic \ 
 VNlVB?trITY s 
 CARBONIFEROUS AGE. 
 
 251 
 
 I. Cryptogams, or Flowerless Plants, Order of 
 Acrogens. 
 
 1, Fern Tribe. Ferns were very abundant, a large part of 
 the fossil plants of a coal-region being their delicate fronds 
 (usually called leaves). A portion of a fossil fern is repre- 
 
 Figs. 282-287- 
 
 Fig. 282, Lepidodendron aculeatum ; 283, Sigillaria oculata ; 284, Stigmaria ficoides ; 285, 
 Sphenopteris Gravenhorstii ; 28G, Culamites cannseformis ; 287, Trigoriocarpus tricuspi- 
 datus. 
 
 sented in Fig. 285. Besides small species, like the common 
 kinds of the present day, there were Tree-ferns, species that 
 
252 PALEOZOIC TIME. 
 
 had a trunk, perhaps 20 or 30 feet high, and which bore at 
 top a radiating tuft of the very large leaf-like fronds, resem- 
 bling the modern tree-fern of the tropics. One of the tree- 
 ferns of the Pacific is represented in Fig. 281, near the middle 
 of the view, and smaller ferns in front of it below. Tree- 
 ferns, however, were not very common in the Carboniferous 
 forests. The scars in fossil or recent tree-ferns are many 
 times larger than those of Lepidodendrids, and the fossils may 
 be thus distinguished. 
 
 2, Lycopodium Tribe, 1. The Lepidodendrids appear tc 
 have been among the most abundant of Carboniferous forest- 
 trees, especially in the earlier half of the Carboniferous Age, or 
 to the middle of the Coal Period. They probably covered both 
 the marshes and the drier plains and hills. Some of the old 
 logs now preserved in the strata are 50 to 60 feet in length, 
 strikingly contrasting with the little Ground-Pines of modern 
 times; and the pine-like leaves were occasionally a foot or 
 more long. The taller tree to the left, on page 250, is a Lepi- 
 dodendron. Fig. 282 shows the surface-markings of one of 
 the species, natural size. 
 
 2. Sigillarids. The Sigillarice were a very marked feature 
 of the great jungles and damp forests of the Coal period. 
 They grew to a height sometimes of 30 to 60 feet ; but the 
 trunks were seldom branched, and must have had a stiff, 
 clumsy aspect, although covered above with long, slender, 
 rush-like leaves. Fig. 283 represents a common species, ex- 
 hibiting the usual arrangement of the scars in vertical lines, 
 and also indicating, by the difference in the scars of the right 
 row from those of the others, their difference of form on the 
 outer surface of the tree and beneath the surface. 
 
 3. Stigmarice. The fossil Stigmaricc are stout stems, gen- 
 erally 2 to 3 or more inches thick, having over the surface 
 distinct rounded punctures or depressions. Fig. 284 is a por- 
 tion of the extremity of a stem, showing the rounded depres- 
 sions and also the leaf-like appendages occasionally observed. 
 The stems or branches are a little irregular in form, and spar- 
 
CARBONIFEROUS AGE. 253 
 
 ingly branched. They have been found spreading, like roots, 
 from the base of the trunk of a Sigillaria, and sometimes also 
 from that of a Lepidodendron ; and they are hence regarded 
 either as the roots or subaqueous stems of these trees. They 
 are an exceedingly common fossil, especially in the under- 
 clays of the Coal-measures (page 246). 
 
 3. Equisetum Tribe, Fig. 286 represents a portion of one 
 of the tree-rushes, or Calamites, of the Equisetum or Horse- 
 tail tribe. The specimens were very abundant in the great 
 marshes, through the whole of the Carboniferous Age. Some 
 of them were 20 feet or more high and 10 or 12 inches in 
 diameter. 
 
 Besides these Cryptogams there were also Fungi; but, as 
 already stated, no remains of Mosses from the rocks of the 
 age are known. 
 
 In the ideal view of a Carboniferous landscape, Fig. 281, 
 page 250, the broken trunk to the right is a Sigillaria. The 
 landscape, to be quite true to nature, should have been made 
 up largely of Sigillaria^, Calamites, and Lcpidodcndra, with 
 few tree-ferns. The Stigmariae should have been mostly con- 
 cealed beneath the water or soil, or in the submerged mass of 
 the floating islands. 
 
 II. Phenogams, or Flowering Plants, Order of 
 Gymnosperms. 
 
 1. Conifers. Trunks of trees, Coniferous in character, and 
 related especially to the Araucanian pines, are not uncommon. 
 
 2. Fruits. Besides the leaves, stems, and trunks already 
 alluded to, there are various nut-like fruits found in the Car- 
 boniferous strata. One is represented in Fig. 287 (page 251), 
 the figure to the left being that of the shell, and the other 
 that of the nut which it contained. Some of them are two 
 inches in length. The most of them were probably the fruit 
 of Conifers. 
 
 It is seen from the above that 
 
 1. The vegetation of the Carboniferous age consisted very 
 largely of Cryptogams, or flowerless plants. 
 
254 PALEOZOIC TIME. 
 
 2. The flowering plants, or Phenogams, associated with the 
 flowerless vegetation, were of the order of Gymnosperms, 
 whose flowers are imperfect and inconspicuous. 
 
 3. While, therefore, there was abundant and beautiful fo- 
 liage (for no foliage exceeds in beauty that of Ferns), the 
 vegetation was nearly flowerless. 
 
 4. The characteristic Cryptogams were not only of the 
 highest group of that division of plants, but in general they 
 exceeded in size and perfection the species of the present day, 
 many being forest-trees. 
 
 2. Animals. 
 
 1. Radiates. Among Piadiates, species of Crinoids were 
 especially numerous in the Subcarboniferous period. Figs. 
 288, 289, 290 represent some of the species. The radiating 
 arms are perfect in Fig. 288, but wanting in 289. Fig. 290 
 is a species of the genus Pentremites (named from the Greek 
 Tre^re, Jive, alluding to the five-sided form of the fossil). The 
 Pentremites had a stem made of calcareous disks, like other 
 Crinoids, but no long radiating arms at top. 
 
 Fig. 291 presents an upper view of a very common Coral 
 of the same period : it has a columnar appearance in a side 
 view. 
 
 2. Mollusks. The tribe of Bryozoans contained the singu- 
 lar screw-shaped (or auger-shaped) Coral shown in Fig. 292, 
 and named Archimedes (referring to Archimedes' screw). It 
 is made up of minute cells that open over the lower surface ; 
 each of the cells, when alive, contained a minute Bryozoum 
 (page 183). These fossils are common in some of the Subcar- 
 boniferous limestone strata. 
 
 Brachiopods were the most abundant of Mollusks through 
 the Carboniferous age, and especially species of the genera 
 Spirifer and Productus. Figs. 293 to 296 are of species from 
 the American Coal-measures: Fig. 295, a Spirifer ; Fig. 294, 
 a Productus; Fig. 293, a Chonetes ; Fig. 296, an Athyris, oc- 
 curring also in Europe. Fig. 297 represents one of the Gas- 
 
CARBONIFEROUS AGE. 
 
 255 
 
 teropods of the Coal-measures. Fig. 298 is a Pupa, the earli- 
 est yet found of land-snails : it is from the Coal-measures of 
 
 Figs. 288-298. 
 
 291 
 
 RADIATES : Fig. 288, Zeacrinus elegans ; 2SO, Actinocrinus proboscidians ; 290, Peutre- 
 inites pyriforniis ; 291, Lithostrotion Canadense. MOLLUSKS : Fig. 292, Archimedes 
 reversa; 293, Chonetes mesoloba; 294, Produetus Nebrascensis : 295, Spirifer cameratus ; 
 296, Athyris subtilita ; 297, Pleurotomaria tabulata ; 298, Pupa vetusta. 
 
 Nova Scotia ; others have been found in Illinois. The order 
 of Cephalopods contained but few and small species of the 
 old tribe of Orthocerata, but many of the Ammonite-like Go- 
 niatitcs. 
 
256* 
 
 PALEOZOIC TIME. 
 
 3. Articulates, Among Articulates, Crustaceans appeared 
 under a new form, much like that of modern shrimps, and 
 Trilobites were of rare occurrence. 
 
 Figs. 299-301. 
 
 CPIDERS: Fig. "299, Arthrolycosa antiquus ; 30<\ Eoscorpius carbonarius. INSECT : 
 Fiy. 301, Miamia Bronsoui. 
 
 Besides Insects (Fig. 301), there were also Myriapods, true* 
 Spiders (Fig. 299), and Scorpions (Fig. 300) ; the figures ^are 
 of Illinois species. The Insects include May-flies (Neurop- 
 ters), Locusts and Cockroaches (or Orthopterous insects), and 
 Beetles (or Coleopters). 
 
 4. Vertebrates. Fishes were numerous, both of the orders 
 of Ganoids and Selachians. All the Ganoids were of the art- 
 
CARBONIFEROUS AGE 
 
 257 
 
 cient type, having the tail vertebrated (or heterocercal), as 
 in Fig. 302, representing a Permian species of Palceoniscus. 
 Many of the Selachians, or Sharks, were of great size, as 
 shown by the fin-spines. Fig. 303 represents a small portion 
 of one of these spines, natural size, from the Subcarboniferous 
 beds of Europe. One of the largest specimens of the same 
 species when entire must have been 18 inches long. 
 
 Figs. 302, 303. 
 
 Fig. 302, Palseoniscus Freieslebeni (x); 303, Part of a spine of Ctenacanthus major. 
 
 Amphibian Reptiles occur through the age. They are called 
 Ldbyrinlhodonts, because the teeth, like those of the Ganoids, 
 are labyrinthine in the arrangement of the dentine. The ear- 
 liest traces are tracks found in the Subcarboniferous beds at 
 Pottsville, Pa. (Fig. 304); they are about four inches broad, 
 those of the fore-feet, as described by Dr. Lea, 5-fingered, and 
 those of the hind-feet 4-fingered. Fig. 305 represents a skele- 
 ton of another species from the Ohio Coal-measures, found by 
 Newberry. Some of the related Amphibians from Ohio are 
 long, like snakes. 
 
 17 
 
258 
 
 PALEOZOIC TIME. 
 
 True Reptiles appear to have been represented in the Coal 
 period by swimming species, or Enaliosaurs ; and, in the Per- 
 
 Figs. 304-306. 
 
 304 
 
 l-'ig. 304, Tracks of Sauropus primsevris (x ) ; 305, Raniceps Lyellii ; 306, a, Vertebra o,' 
 Eosaurus Acadianus. 
 
 mian period, by higher Crocodile-like Reptiles of the tribe of 
 Thecodonts. The Enaliosaurs (or sea-lizards, as the word sig- 
 nifies) had paddles like whales, and doubly concave vertebrae, 
 
CARBONIFEROUS AGE. 259 
 
 like fishes. (Figs. 361 and 365 represent Mesozoic species.) 
 A vertebra, found by Marsh in Nova Scotia, and referred by 
 him to the Enaliosaurs, is represented in Fig. 306; and Fig. 
 306 a, a transverse section, shows the biconcave character. 
 The Thecodouts also had the fish-like character of biconcave 
 vertebrae. They had the teeth in sockets, like the Crocodiles, 
 and hence the name Thecodont. 
 
 5. General Observations. 
 
 1. Formation of Coal, and origin of the Coal-measures. 7. 
 
 Origin of the Coal. The vegetable origin of coal is proved 
 by the following facts : 
 
 1. Trunks of trees, retaining still the original form and 
 part of the structure of the wood, have been found changed 
 to mineral coal, both in the Carboniferous strata and in more 
 modern formations, showing that the change may and does 
 take place. 
 
 2. Beds of peat, a result of vegetable growth and accumu- 
 lation, exist in modern marshes ; and in some cases they are 
 altered below to an imperfect coal. (See page 75, on the 
 formation of peat.) 
 
 3. Eemains of plants, their leaves, branches, and stems or 
 trunks, abound in the Coal-measures ; trunks sometimes ex- 
 tend upward from a coal-bed into and through some of the 
 overlying beds of rock ; roots or stems abound in the under- 
 clays. 
 
 4. The hardest anthracite contains throughout its mass 
 vegetable tissues. Professor Bailey examined with a high 
 magnifying power several pieces of anthracite burnt at one 
 end, like Fig. 307, taking fragments from the junction of the 
 white and black portion, and detected readily the tissues. 
 Fig. 308 represents the ducts, as they appeared in one case 
 under his microscope; and Fig. 309 part of the same, more 
 magnified. Fig. 310 shows the appearance of the spores of 
 Lycopods (Lepidodendrids) much magnified ; they are com- 
 mon in coal. 
 
260 
 
 PALEOZOIC TIME. 
 
 2. Decomposition of Vegetable Material. The Mineral Coal of 
 the Coal-measures consists (impurities excluded) of 77 to 97 
 per cent of carbon along with 2 to 6 of hydrogen and 2 to 15 
 of oxygen ; and woody material, whether of Conifers, Ferns, 
 Lycopods, or Equiseta, consists of about 50 per cent of car- 
 bon, 6 of hydrogen, and 44 of oxygen. To change the vege- 
 
 Pigs. 307-309. 
 
 309 
 
 
 Fig. 310 
 
 Vegetable tissues in Anthracite. 
 
 table material to coal, it is necessary to g^t rid of part of the 
 oxygen and hydrogen. Vegetable matter decomposing in the 
 
 open air like wood burnt 
 in an open fre passes into 
 gaseous combinations, and lit- 
 tle or no carbon is left behind. 
 Both the oxygen of the air 
 and that of the wood take part 
 in the combustion or decom- 
 position. But if the former 
 is more or less excluded by 
 a covering of earth (as of 
 strata) or of water (as in a 
 swamp), the combustion is 
 incomplete, and coal may re- 
 sult, consisting of the uncon- 
 
 sumed carbon combined with some hydrogen and oxygen. 
 The actual loss, by weight, in the transformation into bitu- 
 
 Spores and part of a Sporangium in bitumi- 
 nous coal of Ohio ( x 70). 
 
CARBONIFEROUS AGE. 261 
 
 ruinous coal, is at least three fifths of the wood, and in that into 
 anthracite, three fourths. Adding to this loss that from com- 
 pression, by which the material is brought to the density of 
 mineral coal, the whole redaction in bulk is not less than to 
 one fifth for the former, and to one eighth for the latter. In 
 other words, it would take 5 feet of vegetable matters to make 
 1 of bituminous coal, and 8 feet to make 1 of anthracite. 
 
 3. Impurities in Coal. The coal thus formed derived some 
 silica and other earthy ingredients from the wood itself, and 
 alumina from the Lepidodendrids, this earth existing in the 
 ash of modern Lycopods. By this means the best coal re- 
 ceived some earthy impurities, while the poorer coals contain 
 clay or earthy material carried over the marshes by the waters 
 or winds. Sulphur is a common impurity ; it usually occurs 
 combined with iron, forming pyrite or sulphid of iron. 
 
 4. Accumulation and Formation of Coal-beds. The origin of 
 coal-beds was, then, as follows : The plants of the great 
 marshes and shallow lakes of the Coal era, the latter with 
 their floating islands of vegetation, continued growing for a 
 long period, dropping annually their leaves, and from time to 
 time decaying stems or branches, until a thick accumulation 
 of vegetable remains was formed, probably 5 feet in thick- 
 ness for a one-foot bed of bituminous coal. The bed of ma- 
 terial thus prepared over the vast wet areas of the continent 
 early commenced to undergo at bottom that slow decomposi- 
 tion the final result of which is mineral coal. But, as the 
 coal-beds alternate with sandstones, shales, conglomerates, and 
 limestones, the long period of verdure was followed by 
 another of overflowing waters, and generally, in the case 
 of the region of the Interior basin of North America, oceanic 
 waters, as the fossils prove, which carried sands, pebbles, 
 or earth, over the old marsh, till scores or hundreds of feet in 
 depth of such deposits had been made. Thus the bed of 
 vegetable material was buried ; and under this condition the 
 process of decomposition and change to mineral coal went 
 forward to its completion ; it had the smothering influence of 
 
262 PALEOZOIC TIME. 
 
 the burial, as well as the presence of water, to favor the pro- 
 cess. 
 
 5. Climate of the Age. The wide distribution of the coal 
 regions over the globe, from the tropics to remote Arctic 
 lands, and the general similarity of the vegetable remains in 
 the coal-beds of these distant zones, prove that there was a 
 general uniformity of climate over the globe in the Carbon- 
 iferous age, or at least that the climate was nowhere colder 
 than warm-temperate. Besides, corals and shells existed dur- 
 ing the Subcarboniferous period in Europe, the United States, 
 and the Arctic within 20 of the north pole, and so profusely 
 as to form thick limestones out of their accumulations ; and 
 some Arctic species are identical with those of Europe and 
 America. The ocean's waters, even in the far north, were, 
 therefore, warm compared with those of the modern temper- 
 ate zone, and probably quite as warm as the coral-reef seas 
 of the present age, which lie mostly between the parallels of 
 28 cither side of the equator. 
 
 6. Atmosphere. The atmosphere was especially adapted for 
 the age in other respects. It contained a larger amount than 
 now of carbonic-acid gas, the gas which promotes (if not in 
 excess) the growth of vegetation. Plants derive their carbon 
 mainly from the carbonic acid of the atmosphere ; and hence 
 the mineral coal of the world is approximately a measure of 
 the amount of carbonic acid the atmosphere in the Carbonif- 
 erous era lost. The growth of the flora of tha,t age was a 
 means of purifying the atmosphere so as to fit it for the higher 
 terrestrial life that was afterward to possess the world. 
 
 Again, the atmosphere was more moist than now. This 
 follows from the greater heat of the climate and the greater 
 extent as well as higher temperature of the oceans. The con- 
 tinents, although larce during the intervals of verdure com- 
 
 O O o 
 
 pared with the areas above the ocean in the Devonian or Si- 
 lurian, were still small and the land low. It must, therefore, 
 have been an era of prevailing clouds and mists. A moist 
 climate would not, however, have been universal, since even 
 
CAKBONIFEROUS AGE. 263 
 
 the ocean has now its great areas of drought depending on the 
 courses of the winds. America is now the moist forest-conti- 
 nent of the globe ; and tiie great extent of the coal-fields of 
 its northern half proves that it bore the same character in the 
 Carboniferous age. 
 
 2. Geography. 7. Appalachian and Rocky Mountains not made. 
 On page 240 it is stated that the continents in this age 
 were low, with few mountains. The non-existence of the 
 Appalachians of Pennsylvania and Virginia is proved by the 
 fact that the rocks of these mountains are to a considerable 
 extent Carboniferous rocks; partly marine rocks, indicat- 
 ing that the sea then spread over the region ; partly coal-beds, 
 each bed evidence that a great fresh-water marsh, flat as all 
 marshes are, for a long while occupied the region of the pres- 
 ent mountains. 
 
 There is the same evidence that the mass of the Rocky 
 Mountains had not been lifted; for marine Carboniferous 
 rocks constitute a large part of these mountains, many beds 
 containing remains of the life of the Carboniferous seas that 
 covered that part of North America. Only islands, or archi- 
 pelagoes of islands, made by some Archaean and perhaps 
 also Paleozoic ridges, existed in the midst of the widespread 
 western waters. 
 
 2. Condition in the Subcarboniferous Period. Through the first 
 period of this age the Subcarboniferous the continent 
 was almost as extensively beneath the sea as in the Devonian 
 age. This, again, is shown by the nature and extent of the 
 Subcarboniferous rocks, the great crinoidal limestones. 
 The shallow continental seas were profusely planted with 
 Crinoids amid clumps of Corals. Brachiopods were here and 
 there in great abundance, many lying together in beds as oys- 
 ters in an oyster-bed; other Mollusks, both Lamellibranchs 
 and Gasteropods, were also numerous ; Trilobites were few ; 
 Goniatites and Nautili, along with Ganoid Fishes and Sharks, 
 were the voracious life of the seas, and Amphibian reptiles 
 haunted the marshes. 
 
264 PALEOZOIC TIME. 
 
 3. Transition to the Carboniferous Period. Finally, the Sub- 
 carboniferous period closed, and the Carboniferous opened. 
 But in the transition from the period of submergence to that 
 of emergence, required to bring into existence the great 
 marshes, a widespread bed of pebbles, gravel, and sand was 
 accumulated by the waves dashing rudely over the surface of 
 the rising continent; and these pebble-beds make the Mill- 
 stone grit that marks the commencement of the Carboniferous 
 period in a large part of Eastern North America, especially 
 along the Appalachian region, and also in Europe. ^ 
 
 4. Coal-plant Areas in the Carboniferous Period. Then began 
 the epoch of the Coal-measures. 
 
 The positions of the great coal areas of North America 
 (see map, page 195) are the positions, beyond question, of the 
 great marshes and shallow fresh- water lakes of the period. 
 But it is probable that the number of these marshes was less 
 than that of the coal areas. The Appalachian, Illinois, Mis- 
 souri, Arkansas, and Texas fields may have made one vast 
 Interior continental marsh-region, and those of Ehode Island, 
 Nova Scotia, and New Brunswick an Eastern border marsh- 
 region connected over Massachusetts Bay and the Bay of 
 Fundy. There is reason, however, for believing that a low 
 area of dry land extending from the region of Cincinnati into 
 Kentucky (page 217) divided at least the northern portion 
 of the Interior marsh. 
 
 The Michigan marsh-region appears also to have had its 
 dry margins, instead of coalescing with the Illinois or Ohio 
 areas. 
 
 It is not to be inferred that the marshes alone were cov- 
 ered with verdure. The vegetation probably spread over all 
 the dry land, though making thick deposits of vegetable re- 
 mains only where there were marshes under dense jungles 
 and shallow lakes with their floating islands. 
 
 5. Alternations of Condition : Changes of Level. It has been 
 remarked that the many alternations of the coal-beds with 
 sandstones, shales, conglomerates, and limestones (page 245), 
 
CARBONIFEROUS AGE. 265 
 
 are evidence of as many alternations of level, or at least of 
 conditions, during the era. After the great marshes of the 
 Continental Interior had been long under verdure, the salt 
 waters began again to encroach upon them in consequence of 
 a sinking of the land, and finally swept over the whole surface, 
 destroying the terrestrial and fresh-water life of the area,- that 
 is, the terrestrial and fresh-water Plants, Mollusks, Insects, and 
 Reptiles, but distributing at the same time the new life of 
 the salt waters. Then, after another long period, one perhaps 
 of many oscillations in the water-level, in which sedimentary 
 beds in many alternations were formed, the continent again 
 rose to aerial life, and the marshes and shallow lakes were 
 luxuriant anew with the Carboniferous vegetation. Thus the 
 sea prevailed at intervals intervals of long duration 
 through the era even of the Coal-measures ; for the associated 
 sedimentary beds, as has been stated, are at least fifty times 
 as thick as the coal-beds. In the Nova Scotia Coal area, the 
 waters which came in over the coal-beds were the brackish 
 or fresh waters of a great estuary, that at the mouth of the 
 St. Lawrence River of the Carboniferous period. 
 
 These oscillations continued until 3,000 to 4,000 feet of 
 strata were formed in Pennsylvania, and over 14,000 in Nova 
 Scotia. 
 
 The Carboniferous period was, therefore, ever varying in 
 its geography. A map of its condition when the great coal- 
 beds were accumulating would have its eastern coast-line not 
 far inside of the present, and in the region of Nova Scotia 
 and New England even outside of the present ; for there must 
 have been a sea-barrier in order that the deposits in the for- 
 mer region should have been of brackish or fresh- water origin. 
 The southern coast-line would pass through central Carolina, 
 Georgia, Alabama, and Northern Mississippi, then west of 
 the Mississippi, around Arkansas and the bordering counties 
 of Texas ; thence it would stretch northward, bounding a 
 sea covering a large part of the Rocky-Mountain region, for 
 the Coal period was, in that part of the continent, mainly a 
 
266 PALEOZOIC TIME. 
 
 time of limestone-making. On the contrary, in a map repre- 
 senting it during the succeeding times of submergence, the 
 coast-line would run through Southeastern New England, then 
 near the southern boundary of New York State, then north- 
 westward around Michigan, then southward again to Northern 
 Illinois, and then westward and northwestward to the Upper 
 Missouri region, or the Rocky Mountain sea. Through these 
 conditions, as the extremes, the continent passed several 
 times in the course of the Carboniferous period. 
 
 6. Condition in the Permian Period. Finally, in the Permian 
 period, the Appalachian region, and the Interior region east 
 of a north-and-south line running through Missouri, appear 
 to have been mainly above the ocean ; for the Permian beds 
 are mostly confined to the meridians of Kansas and the 
 remoter West. 
 
 GENERAL OBSERVATIONS ON THE PALEOZOIC. 
 
 1. Rocks, 7. Maximum thickness. The maximum thick- 
 ness of the rocks of the Silurian age in North America is at 
 least 25,000 feet ; of the Devonian, about 14,400 feet ; and of 
 the Carboniferous age, about 16,000 feet. 
 
 2. Diversities of the different Continental regions as to kinds of 
 rocks. The Paleozoic rocks of the Appalachian region are 
 mainly sandstones, shales, and conglomerates ; only about one 
 fourth in thickness of the whole consists of limestone. The 
 rocks of the Interior Continental are mostly limestone, full 
 two thirds being of this nature. 
 
 The difference of these two regions, in this particular, will 
 be appreciated on comparing the following general section of 
 the strata of the Interior with the section, on page 193, of the 
 rocks of New York, New York State lying on the inner 
 border of the Appalachian region. The Lower Silurian beds 
 in the Mississippi basin, as the section shows, consist mainly 
 of limestones ; so also the Upper Silurian, Devonian, and Sub- 
 carboniferous formations ; and the Carboniferous of the region 
 
GENERAL OBSERVATIONS. 
 
 267 
 
 contains more limestone than that of the East. In the Devo- 
 nian of the Interior the Hamilton is represented by a lime- 
 stone in parts of Michigan, Ohio, Canada West, and Illinois, 
 to Iowa, and besides this there is only a black shale, one to 
 three or four hundred feet thick. 
 
 In the Eastern-border region, about the Gulf of St. Law- 
 rence, there is a great predominance of limestones in the 
 
 Permian 
 
 Carboniferous 
 
 Subcarboniferous -| 
 
 ('In- in ii MI: .... 
 Hamilton 
 
 Corniferous. 
 
 Niagara 
 
 Cincinnati 
 
 Trenton 
 
 Canadian 
 'Potsdam 
 
 Coal Conglomerate. 
 Subcarboniferous limestone. 
 
 Subcarboniferous sandstone. 
 Black shale. 
 Cliff limestone. 
 
 Blue limestone and shale. 
 
 Trenton limestone ; Galena 
 limestone ; Black River 
 limestone. 
 
 Lower Magnesian limestone 
 (= Calciferous). 
 
 Potsdam sandstone. 
 
 of the Paleozoic rocks in the Mississippi basin. 
 
 formations. They prove the existence in that region of an 
 Atlantic-border basin similar in some respects to the basin of 
 the Interior, the two being separated by the Green Moun- 
 tains, that is, the northern part of the Appalachian region. 
 
 3. Diversities of the Appalachian and Interior- Continental regions 
 as to the thickness of the rocks. In the Appalachian region 
 the maximum thickness of the Paleozoic rocks is about 40,000 
 feet. But this thickness is not observed at any one locality, 
 it being obtained by adding together the greatest thicknesses 
 of the several formations wherever observed. The greatest 
 actual thickness in Pennsylvania is about 30,000 feet, 01 
 nearly six miles. 
 
268 PALEOZOIC TIME. 
 
 In the central portions of the Interior-Continental region 
 the thickness varies from 3,500 feet (and still less on the 
 northern border) to 6,000 feet ; and it is, therefore, from one 
 lixtli to one tenth that in the Appalachian region. 
 
 4. Origin of the deposits. The material of the fraymental 
 rocks, or those of sand, clay, mud, pebbles (the sandstones, 
 shales, earthy sandstones and conglomerates), was made (1) 
 by the wear of pre-existing rocks under the action of water ; 
 
 (2) by disintegration produced by partial decomposition ; and 
 
 (3) by disaggregation from expansion and contraction due to 
 daily and annual changes of temperature. The water was 
 mainly that of the ocean, and the power was that of its waves 
 and currents. But the water from the rains aided in the 
 wear, although there were no large rivers ; and, through the 
 carbonic acid it took up from the atmosphere, it was a great 
 agent in the disintegration of exposed rocks, feldspar, the 
 most common ingredient in crystalline rocks and also nearly 
 all iron-bearing minerals, yielding more or less easily under 
 the action. 
 
 The material of the coarser rocks may have accumulated 
 where the waves were dashing against a beach or an exposed 
 sand-reef, or else where currents were in rapid movement 
 over the bottom; for accumulations of pebbles and coarse 
 sand are now made under these circumstances. The material 
 of the earthy sandstones may have been the mud or earthy 
 sands forming the bottom of shallow seas. The fine clayey 
 or earthy deposits must have been made in either sheltered 
 bays or interior seas, in which the waves were light, and 
 therefore fitted to produce by their gentle attrition the finest 
 of mud ; or else in the deeper off-shore waters, where the finer 
 detritus of the shores is liable to be borne by the currents. 
 
 Accumulations of any degree of thickness may be made in 
 shallow waters, provided the region is undergoing very slow 
 subsidence ; for in this way the depth of the waters may be 
 kept sufficient to allow of constantly increasing depositions. 
 Thus, by a slow subsidence of 1,000 feet, deposits 1,000 feet 
 
GENERAL OBSERVATIONS. 269 
 
 thick may be produced, and the depth of water at no time 
 exceed 20 feet. The occurrence of ripple-marks, mud-cracks, 
 or rain-drop impressions in many beds of most of the forma- 
 tions proves that the layers so marked were successively near 
 the surface, and therefore that there must have been a grad- 
 ual sinking of the bottom as the beds were formed. 
 
 The limestones of the Paleozoic were probably made, in 
 every case, out of organic remains, either Shells, Corals, Cri- 
 noids, etc., or the minute Khizopods, which are known to 
 have formed, to a large extent, the chalk-beds of Europe. 
 Shells, Corals, and Crinoids must be ground up by the waves to 
 form fine-grained rocks ; while the shells of Ehizopods are so 
 minute as to be already fine grains, and may become compact 
 rocks by simple consolidation. 
 
 The hornstone in the limestones, as remarked on page 234, 
 may be wholly of organic origin. 
 
 2. Time-Ratios. Judging from the maximum thickness of 
 the rocks of the several Paleozoic ages in North America, and 
 allowing that five feet of fragmental rocks may accumulate 
 in the time required for one foot of limestone, the relative 
 lengths of the Silurian, Devonian, and Carboniferous ages 
 were not far from 4 : 1 : 1, and the Lower Silurian era was 
 four times as long as the Upper. 
 
 Time moved on slowly in the earth's first beginnings. The 
 condition of the earth in an age of Invertebrates, when all life 
 was the life of the waters, and nothing existed above the 
 ocean's level except it may be the humble lichen or fungus, 
 was very inferior to that of the Carboniferous, when the con- 
 tinents had their forests, the waters their fishes, and the 
 marshes their reptiles. Yet the length of time through which 
 the earth was groping under the first-mentioned condition 
 was vastly longer than under the last. Such is time in the 
 view of the infinite Creator. 
 
 3. Geography. 7. Close of Archaean time. The map on page 
 199 shows approximately the outline of the dry land of North 
 America at the close of the Archsean. The only mountains 
 
270 PALEOZOIC TIME. 
 
 were Archaean mountains, the principal of which were the 
 Laurentiau of Canada, the Adirondacks of Northern New York, 
 the Highlands of New Jersey and Dutchess County of New 
 York, the Blue Eidge farther to the southwest, and the Wind- 
 River and other eastern ridges of the Rocky Mountain region. 
 We cannot judge of the height of these mountains then from 
 what we now see, after all the ages of Geology have passed 
 over them, for the elements and running water have never 
 ceased action since the time of their uplift, and the amount 
 of loss by degradation must have been very great. 
 
 2. General Progress through Paleozoic time. The increase of 
 dry land during the Paleozoic has been shown (pages 225, 239) 
 to have taken place mainly along the borders of the Archaean, 
 so that the original area was thus gradually extending. This 
 increase is well marked from north to south across New York. 
 At the close of the Lowe* Silurian the shore-line was not far 
 from the present position of the Mohawk, indicating but a 
 slight extension of the dry land in the course of this very 
 long era; when the Upper Silurian ended, the shore-line 
 probably extended along a score of miles or so south of the 
 Mohawk. When the Devonian ended and the Carboniferous 
 age was about opening, the coast-line was just north of the 
 Pennsylvania boundary. 
 
 The progress southward was at an equal rate in Wisconsin, 
 where there is an isolated Archsean region like that of North- 
 ern New York. In the intermediate district of Michigan the 
 coast made a deep northern bend through the Silurian and 
 Devonian. In the Carboniferous the same great Michigan 
 bay existed during the intervals of submergence ; but it was 
 changed to a Michigan marsh or fresh-water lake, filled with 
 Coal-measure vegetation, during the intervening portions of 
 the Carboniferous period ; and, at the same times, as explained 
 on page 265, the continent east of the western meridian of 
 Missouri had nearly its present extent, though not its moun- 
 tains or its rivers. 
 
 3. Regions of rock-making, and their differences. The sub- 
 
GENERAL OBSERVATIONS. 271 
 
 merged part of the continent included far the larger portion, 
 and was the scene of nearly all the rock-making. Areas of 
 fresh-water, however, existed at times, especially in the Devo- 
 nian and Carboniferous, as is proved by the coal beds, and by 
 occasional fresh-water shells in shales and sandstones. 
 
 The rocks, as partially explained on page 269, varied in kind 
 with the depth, and with the exposure to the open sea. 
 
 This Interior Continental region, which was for the most of 
 the time a great interior oceanic sea, afforded the conditions 
 fitted for the growth of Corals and Crinoids and other clear- 
 water species, and hence for the making of limestone reefs 
 out of their remains ; for limestones are the principal rocks 
 of the interior. Yet there were oscillations in the level ; for 
 there are abrupt transitions in the limestones, and some sand- 
 stones and shales alternate with them. But these oscillations 
 were not great, the whole thickness of the rocks, as stated on 
 page 268, being small. 
 
 The Appalachian region, on the contrary, presented the 
 conditions required for fragmental deposits. It was appar- 
 ently a region of immense sand-reefs and mud-flats, with 
 bays, estuaries, and extensive submerged off-shore plateaus. 
 Here the change of level was very great; for within this 
 region occur nearly six miles of Paleozoic formations (page 
 267). This vast thickness indicates that while there were 
 various upward and downward movements over this Appala- 
 chian region through Paleozoic time, the downward move- 
 ments exceeded the upward even by the amount just stated. 
 These movements were in progress from the Potsdam period 
 onward; the formations of nearly every period exceed 8 to 
 10 times the thickness they have over the Interior region. 
 
 4. Mountains of Paleozoic origin. The mountains in Eastern 
 North America, made in the course of the Paleozoic ages, 
 were few. Those of the region south of Lake Superior about 
 Keweenaw Point, and to the west, probably rose during the 
 Canadian period, the second of the Lower Silurian. The 
 Green Mountain region became dry land after the close of the 
 
272 PALEOZOIC TIME. 
 
 Lower Silurian (page 2 16); but there is no reason to believe 
 that it was at its present level, for the Hudson Eiver Valley 
 east of Hudson, and part or all of the Connecticut Valley, was 
 beneath the ocean, and became covered by crinoidal and coral 
 reefs and other formations during the Lower Helderberg era, 
 and perhaps also during the early Devonian. The Devonian 
 and other beds of the vicinity of Gaspe, and of Nova Scotia 
 and New Brunswick, were raised into ridges before the Car- 
 boniferous age began, mountain-making having gone forward 
 in this Atlantic-border region after the close of the Devonian. 
 But the larger part of the continental area remained without 
 mountains. The Eocky chain had only some ridges as isl- 
 ands in the seas, and the Appalachians south of New England 
 were yet to be made. 
 
 5. Rivers ; Lakes. The depression between the New York 
 and the Canada Archaean, dating from Archaean time, was 
 the first indication of a future St. Lawrence channel. It con- 
 tinued to be an arm of the sea, or deep bay, through the Si- 
 lurian, and underwent a great amount of subsidence as it 
 received its thick formations. After the Silurian age marine 
 strata ceased to form, indicating thereby that the sea had re- 
 tired ; and fresh waters, derived from the Archaean heights of 
 Canada and New York, probably began their flow along its 
 upper portion, and emptied into the St. Lawrence Gulf of the 
 time not far below Montreal. 
 
 The raising of New York State out of water at the close 
 of the Devonian suggests that from that time the Hudson 
 Valley was a stream of fresh water. The valley itself, and 
 its continuation north as the Champlain Valley, date 
 from the close of the Lower Silurian, if not from the Ar- 
 chaean. 
 
 The Mississippi and its tributaries, east and west, were not 
 in existence in the Paleozoic ages. In the intervals of Car- 
 boniferous verdure, when the continent was emerged, the 
 Ohio and Mississippi basin were regions of great marshes, 
 lakes, and bayous, and not of great rivers ; for rivers could 
 
GENERAL OBSERVATIONS. 273 
 
 not exist without a head of high land to supply water and 
 give it a flow. 
 
 Over portions of Lake Superior there were extensive rock- 
 deposits and igneous eruptions in part of the Canadian period ; 
 and the thick accumulations show that deep subsidences were 
 then in progress there, as also in the region of the St. Law- 
 rence ; so that we may infer that the basin of this great lake 
 was already in process of formation before the Lower Silurian 
 closed. The extent and position of the great Michigan bay 
 through the Silurian and Devonian ages and much of the 
 Carboniferous, as mentioned on pages 225, 264, show that 
 Lakes Erie, Huron, and Michigan were then within the lim- 
 its of this bay. Whether deeper or not than other portions 
 of the bay, is not known. 
 
 Thus, Geology studies the Geography of the Paleozoic ages, 
 and traces North America through its successive stages of 
 growth. 
 
 4. Climate. No evidence has been found through the 
 Paleozoic records of any marked difference of temperature 
 between the zones. In the Carboniferous age the Arctic seas 
 had their Corals and Brachiopods, and the Arctic lands their 
 forests and marshes under dense foliage, no less than those of 
 America and Europe. The facts on this subject are stated on 
 page 262. 
 
 5. Life. 7. Appearance and disappearance of species. With 
 the beginning and progress of each formation in the series, 
 new species appeared, and the old ones more or less com- 
 pletely disappeared. Such changes in the life occurred in 
 connection even with the minor transitions in the rock-for- 
 mations, as in that from a bed of shale to sandstone or to 
 limestone, and the reverse. Thus, through the ages, life and 
 death were in concurrent progress. 
 
 2. Beginning and ending of genera, families, and higher groups. 
 - The following table of the tribe of Trilobites illustrates the 
 progress which took place in this group and exemplifies the 
 general fact with regard to other tribes : 
 
 18 
 
274 
 
 PALEOZOIC TIME. 
 
 Trilobites 
 
 Paradoxides 
 
 Bathy urus 
 
 Asaphus, Remopleurides 
 
 Calymene, Ampyx, Illaenus, Acidaspis, 
 and Ceraurus 
 
 Homalonotus and Lichas 
 
 Phillipsia, Griffithides 
 
 Silurian. 
 
 Dev. Garb. 
 
 Lower. 
 
 Upper 
 
 P. Pd 
 
 C. P 
 
 The vertical columns correspond to the Lower and Upper 
 Silurian, the Devonian, and the Carboniferous. The left- 
 hand column under Lower Silurian corresponds to the first, 
 or Primordial period ; and the three columns under the Car- 
 boniferous, to the Subcarboniferous, Carboniferous, and Per- 
 mian periods of the age. Opposite TRILOBITES, the black area 
 shows that the tribe began with the beginning of the Paleo- 
 zoic and continued nearly to its end. Next there is the name 
 of a genus which existed only in the Primordial period, it 
 having then many species, but none afterward ; with it there 
 were other genera which had species also in the later part of 
 the Lower Silurian. Then there is a genus, Bathyurus, which 
 continued from the Primordial through the Lower Silurian. 
 Then, others confined to the rest of the Lower Silurian ; others 
 that passed into the Upper Silurian, then to become extinct ; 
 others that continued into the Devonian; and two genera 
 confined to the Carboniferous. 
 
 In a similar manner the genera and families of Brachiopods 
 began at different periods or epochs, and continued on for a 
 while, to become, in general, extinct. Many genera ended in 
 the course of the Paleozoic and at its close ; only a few con- 
 tinued into later periods. 
 
GENERAL OBSERVATIONS. 275 
 
 3. Special Paleozoic psculiarities of the Life. The following 
 facts show in what respects the life of the Paleozoic ages was 
 peculiarly ancient : 
 
 a. Not only are the species all extinct, but almost every 
 genus. Fifteen or sixteen of the genera which existed in the 
 course of the Paleozoic have living species ; and all these are 
 Molluscan. 
 
 b. Among Eadidtes, the Polyps were largely of the tribe of 
 Cyatlwplvylloid corals, which is almost exclusively ancient or 
 Paleozoic. The Echinoderms were mostly Crinoids, and these 
 were in great profusion. Crinoids were far less abundant, 
 and of different genera, in the Mesozoic ; and now, few exist. 
 
 c. Among Mollusks, Bracliiopods were exceedingly abun- 
 dant : their fossil shells far outweigh those of all other Mol- 
 lusks. But in the Mesozoic they were much less numerous 
 than other Mollusks ; and at the present time the group 
 is nearly extinct. The Cephalopoda were represented very 
 largely by Orthoceratx, but few species of which existed in 
 the early Mesozoic, and none afterward. 
 
 d. Among Articulates, Trilobites were the most common 
 Crustaceans, a group exclusively Paleozoic. 
 
 e. Among Vertebrates, the Devonian Fishes were either 
 Ganoids, Placoderms, or Selachians, and the Ganoids had verte- 
 brated tails. Of this kind of Ganoids, but few species lived 
 in the first period of the Mesozoic ; and the whole group of 
 Ganoids is now nearly extinct. Of the Selachians, a large 
 proportion were Cestracionts, a tribe common in the Meso- 
 zoic, but now nearly extinct. 
 
 /. Among terrestrial Plants, there were Lepidodendrids, 
 Siyillarids, Catamites in great profusion, making, with Conifers 
 and Ferns, the forests and jungles of the Carboniferous and 
 later Devonian : no Lepidodendrid or Sigillarid existed after- 
 ward, and the Catamites ended in the Mesozoic. 
 
 Thus, the Paleozoic or ancient aspect of the animal life was 
 produced through the great predominance of Brachiopods, Cri- 
 noids, CyathophyllM Corals, Orthocerata, Trilobites, and verte- 
 
276 PALEOZOIC TIME. 
 
 brated-tailed Ganoids ; and that of the plants over the land, 
 through the Lepidodendrids, Sigillarids, and Calamites, along 
 with the Ferns and Conifers. In addition to this should be 
 mentioned the absence of Angiosperms and Palms among 
 Plants ; the absence of Teliost Fishes, and of Birds and Mam- 
 mals, among Vertebrates ; and of nearly all modern tribes of 
 genera among Radiates, Mollusks, and Articulates. 
 
 4. Mesozoic and Modern types begun in Paleozoic time. The 
 principal Mesozoic type which began in the Paleozoic was the 
 Reptilian. But besides these Reptiles there were the first of 
 the Decapod Crustaceans ; the first of Oysters ; the first of the 
 great tribe of Ammonites, the Goniatitcs being of this tribe ; 
 the first of Insects, Spiders and Centipedes. The type of In- 
 sects, or terrestrial Articulates, belongs eminently to modern 
 time ; for it probably has now its fullest display. 
 
 Thus, while the Paleozoic ages were progressing, and the 
 types peculiar to them were passing through their time of 
 greatest expansion in numbers and perfection of structure, 
 there were other types introduced which were to have their 
 culmination in a future ase. 
 
 DISTURBANCES CLOSING PALEOZOIC TIME. 
 
 1. General quiet of the Paleozoic Ages. The long ages ef 
 the Paleozoic passed with but few and comparatively small 
 disturbances of the strata of Eastern North America. There 
 were some early permanent uplifts in the Lake Superior 
 region, during the Lower Silurian ; again, after the Lower 
 Silurian, the Green Mountains were made ; and again, after 
 the close of the Devonian, there were disturbances and upturn- 
 ings in Eastern New Brunswick, part of Nova Scotia, and East- 
 ern Canada by Gaspe near St. Lawrence Bay. Besides these 
 changes there was, through the ages, a gradual increase on 
 the north in the amount of dry land ; and through parts of 
 all the periods, over a large part of the continent, slow oscil- 
 lations were in progress, varying the water-level and favoring 
 
APPALACHIAN REVOLUTION. 277 
 
 the increasing thickness of the rocks, and their successive 
 variations as to kind and extent. But these movements of 
 the earth's crust were exceedingly slow, probably less than 
 a foot a century. There may have been many occasional 
 quakings of the earth, even exceeding the heaviest of 
 modern earthquakes. There may have been at times sudden 
 risings or sinkings of portions of the continental crust. But 
 the condition of the strata of the interior of the continent, 
 and of the Appalachian region south of the Green Mountains, 
 indicates that general quiet prevailed through the long Paleo- 
 zoic ages. 
 
 2. The Appalachian the region of greatest change of level 
 through the Paleozoic, The region of greatest movement dur- 
 ing these ages was the Appalachian. For it has been show T n 
 that the oscillations which there took place resulted in sub- 
 sidences of one or more thousand feet with nearly every period 
 of the Paleozoic. In the Green Mountain portion the oscilla- 
 tions ceased after the close of the Lower Silurian era ; but not 
 until the subsidence there had reached probably 15,000 feet; 
 and in Pennsylvania and Virginia they continued through a 
 large part of the Carboniferous age, until the sinking amounted 
 to about 30,000 feet. But this sinking was quiet in its prog- 
 ress, as is proved by the regularity in the series of strata. 
 
 The thickness of the coal-beds indicates that the coal-plant 
 marshes were long undisturbed, and therefore that long periods 
 passed without appreciable movement. 
 
 3. Approach of the epoch of Appalachian revolution. The 
 era of comparative quiet alluded to came gradually to a close 
 as the Carboniferous age was terminating, and an epoch of 
 upturning and mountain-making began. There are mountains 
 to testify to this both in Europe and America. 
 
 In Eastern North America the disturbances affected Nova 
 Scotia and the coal area of Ehode Island and Southeastern 
 Massachusetts ; and, with far grander results, the Appalachian 
 region and Atlantic border from Southern New York to Ala- 
 bama. The Appalachian mountains are a part of the result, 
 
278 CLOSE OF PALEOZOIC TIME. 
 
 and hence the epoch is appropriately styled the epoch of the 
 Appalachian revolution. The region in Eastern America of 
 the deepest Paleozoic subsidence and of the thickest accumu- 
 lation of Paleozoic rocks, that is, the Appalachian, was now the 
 region of the profoundest disturbances and the greatest uplifts. 
 4. Effects of the disturbances. The fallowing are among 
 the effects of the disturbances along the Appalachian region 
 and Atlantic border : 
 
 1. Strata were upraised and flexed into great folds, some 
 of the folds a score or more of miles in span. 
 
 2. Deep fissures of the earth's crust were opened, and 
 faults innumerable were produced, some of them of 10,000 
 to 20,000 feet. 
 
 3. Eocks were consolidated; and over some parts sand- 
 stones and shales were crystallized into gneiss, mica schist, 
 and other related rocks, and limestone into architectural and 
 statuary marble. 
 
 4. Bituminous coal was turned into anthracite in Penn- 
 sylvania and Rhode Island. 
 
 5. In the end, the Appalachian mountains were made. 
 
 5. Evidence of the flexures, uplifts, and metamorphism. 
 The evidence that the rocks of the Appalachian region and 
 Atlantic border were flexed, uplifted, faulted, and otherwise 
 changed from their original condition, is as follows : 
 
 The Coal-measures and other Paleozoic strata, though 
 originally spread out in horizontal beds, are now in an uplifted 
 and flexed or folded condition ; and they are so involved to- 
 
 Fig. 312. 
 
 Section at Trevorton Gap, Pa., the dark bands representing coal beds. 
 
 gether in one system of flexures and uplifts that the whole 
 must have been the result of one system of movements. 
 Figs. 312-315 illustrate this, 
 
APPALACHIAN REVOLUTION. 
 
 279 
 
 Figs. 312 and 313, and 120 on page 160, represent sec 
 tions in the coal regions of Pennsylvania. In Fig. 313, the 
 
 Fig. 313. 
 
 Section on the Scliuylkill, Pennsylvania ; P., Pottsville on the Coal-measures ; 2, Calciferous 
 formation ; 3, Trenton ; 4, Hudson River ; 5, Oueida and Niagara ; 7, Lower Helcierberg ; 
 8, 10, 11, Devonian ; 12, 13, Subcarbonherous ; 14, Carboniferous or Coal-measures. 
 
 coal-beds are the upper to the left, numbered 147 the rest are 
 beds of underlying Paleozoic formations, as explained under 
 the figure. Fig. 120 shows the complicated folds in the an- 
 thracite coal measures, near Mauch Chunk; three steep anti- 
 clines occur in 1,200 yards. 
 
 Fig. 314. 
 
 I S.E. 
 
 Section from the Great North to the Little North Mountain through Bore Springs, Virginia ; 
 t, t, position of thermal springs ; n, Calciferous formation ; in, Trenton ; iv, Hudson 
 River ; v, Oneida ; vi, Clinton and Lower Helderberg ; vn, Oriskauy Sandstone and 
 Cauda-Galli Grit. 
 
 Fig. 314 was taken from the vicinity of Bore Springs, in 
 Virginia, and includes Silurian and Devonian beds. 
 
 L-vjtion of the Paleozoic formations of the Appalachians in Southern Virginia, between 
 Walker's Mt. and the Peak Hills (near Peak Creek Valley) : F, fault ; a, Lower Silurian 
 limestone ; b, Upper Silurian ; c, Devonian ; d, Subcarboniferous, with coal-beds. 
 
 Fig. 315 represents one of the great faults in South- 
 ern Virginia (between Walkei 's Mountain and Peak Hills) ; 
 
280 CLOSE OF PALEOZOIC TIME. 
 
 the break is at F, and the rocks on the left were shoved 
 up along the sloping fracture until a Lower Silurian lime- 
 stone (a) was on a level with the Subcarboniferous formation 
 (d), a fault of more than 10,000 feet. Such examples are 
 in great numbers throughout the Appalachians. In many 
 of the transverse valleys the curves may be traced for scores 
 of miles. 
 
 As shown in the above sections (Figs. 312-315), the folds, 
 instead of remaining in regular rounded ridges with even 
 synclinal valleys between, such as the flexing of the strata 
 might make, have been to a great extent worn away, or mod- 
 elled into new ridges and valleys, by the action of waters 
 during subsequent time ; and often what was the top of a fold 
 is now the bottom of a valley, because the folds would be 
 moot broken where most abruptly bent, that is, along the 
 axes of upward flexure, and hence would be most liable in 
 these parts to be cut away or gorged out by any denuding 
 causes. The figures on page 57 illustrate still further the 
 condition of folded strata before and after denudation. Some 
 of the Appalachian folds were probably 20,000 feet in height 
 above the present level of the ocean, or would have had this 
 height if they had remained unbroken, while in fact the 
 loftiest summits now are less than 5,000 feet, and few exceed 
 3,000 feet. 
 
 Over New England there are similar flexures. Those of 
 the Rhode Island coal-formation are very abrupt, and full of 
 faults, the coal-beds being much broken and displaced. 
 
 6. General truths with regard to the results. The follow- 
 ing are some of the general truths connected with the uplifts 
 and metamorphism : 
 
 1. The courses of the flexures and of the outcrops or 
 strike, and those of the great faults, are approximately north- 
 east, or parallel to the Atlantic border. There is a bend 
 eastward in Pennsylvania corresponding with the eastward 
 bend of the southern coast of New England, and then a change 
 to the northward in New England. 
 
APPALACHIAN REVOLUTION. 281 
 
 2. The folds have their steepest slope toward the northwest, 
 or away from the ocean. If Fig. 49 (page 57) represent one 
 of the folds, the left would be the ocean side, or that to the 
 southeast, and the right the landward side, or that to the 
 northwest. 
 
 3. The flexures are most numerous and most crowded on 
 that side of the Appalachian region which is toward the ocean, 
 and diminish westward. There is seldom, however, a gradual 
 dying out westward, the region of disturbance being often 
 bounded on the west by one or more of the great fractures 
 and faults, as in Eastern Tennessee and along the valley of 
 the Hudson. 
 
 4. The consolidation and metamorphism of the strata are 
 more extensive and complete to the eastward (or toward the 
 ocean) than to the westward. 
 
 5. The change of bituminous coal to anthracite, by the 
 expulsion of volatile ingredients, was most complete where 
 the disturbances were greatest, that is, in the more eastern 
 portions of the coal areas. The anthracite region of Penn- 
 sylvania (see map, p. 242) owes its broken character partly 
 to the uplifts and partly to denudation. To the westward 
 the coal is first semi-bituminous, and then, as at Pittsburg, 
 true bituminous. In Pthode Island, where the associated 
 rocks are partly true metamorphic or crystalline rocks and the 
 disturbances are very great, the coal is an extremely hard 
 anthracite, and in some places is altered to graphite, an 
 effect which may be produced in ordinary coal by the heat 
 of a furnace. 
 
 7, Conclusions. These facts lead to the following conclu- 
 sions : 
 
 1. The movement producing these vast results was due to 
 lateral pressure, the folding having taken place just as it 
 might in paper or cloth under a lateral or pushing movement. 
 
 2. The pressure was exerted at right angles to the courses 
 of the folds, as is the case when paper is folded in the manner 
 mentioned. 
 
282 CLOSE OF PALEOZOIC TIME. 
 
 3. The pressure was exerted from the ocean side of the 
 Appalachians ; for the results in foldings and metamorphism 
 are most marked toward the ocean. 
 
 4. The force was vast in amount. 
 
 5. The force was slow in action and long continued, and 
 not abrupt or paroxysmal as when a wave or series of waves 
 is thrown up by an earthquake shock on the surface of an 
 ocean. For the strata were not reduced by it to a state of 
 chaos, but retain their stratification, and show comparatively 
 little confusion, even in the regions of greatest disturbance 
 and alteration. 
 
 6. The action of the force was attended by the production 
 of heat. For without some heat above the ordinary tempera- 
 ture, it is not possible to account for the consolidation and 
 crystallization of the rocks. 
 
 7. The history of the Appalachian Mountains extends 
 through all the geological ages from the Archaean onward. 
 During the Silurian, Devonian, and Carboniferous ages the 
 formations were accumulating to a great thickness, while a 
 slow subsidence was in progress. When the Carboniferous 
 age was closing, and the subsidence had reached a depth of 
 several miles, there were other movements, producing flexures 
 of the strata, uplifts, faults, consolidation, and metamorphism, 
 and ending in the making of the mountains. And finally, 
 during these upliftings, moving waters commenced the work 
 of denudation, which has been continued to the present time. 
 
 8. Disturbances on other continents. The amount of con- 
 temporaneous mountain-making over the globe at this epoch 
 has not yet been clearly made out. Enough is known to ren- 
 der it probable that the Ural Mountains, with their veins of 
 gold and platinum, were made at the same time with the Ap- 
 palachians, and that uplifts and metamorphism also occurred 
 in other parts of Europe, and in Great Britain. Murchison 
 states that the close of the Carboniferous period was specially 
 marked by disturbances and uplifts ; that it was then " that 
 the coal strata and their antecedent formations were very 
 
MESOZOIC TIME. 283 
 
 generally broken up, and thrown, by grand upheavals, into 
 separate basins, which were fractured by numberless power- 
 ful dislocations." 
 
 The epoch of the Appalachian revolution was, then, a grand 
 epoch for the world. The extermination of life which took 
 place at the time was one of the most extensive in all 
 geological history, and must have been a consequence of the 
 great physical changes progressing over the earth's surface. 
 But it cannot be affirmed that the extermination was univer- 
 sal, although no fossils of the Carboniferous formation occur in 
 later rocks ; for these strata, as they are confined to portions 
 of the continental seas, testify only as to changes and de- 
 structions throughout those sea^ and not respecting the life 
 existing elsewhere. 
 
 III. MESOZOIO TIME. 
 
 1. Ages. Mesozoic or mediaeval time, in Geological his- 
 tory, comprises but one age, the EEPTILIAN. In the course 
 of it the class of Eeptiles passed its culmination ; that is, 
 its species increased in numbers, size, and diversity of forms, 
 until they vastly exceeded in each of these respects the Eep- 
 tiles of either earlier or later time. 
 
 2. Area of progress in rock-making. The area of rock- 
 making in North America, during Mesozoic time, was some- 
 what different from what it was in Paleozoic. Then, nearly 
 the whole continent, outside of the northern Archaean area, 
 was receiving its successive formations ; and the three great 
 regions were the Eastern border, the Appalachian, and the 
 Interior Continental. By the close of Paleozoic time the 
 Appalachian region and the Interior east of the Mississippi, 
 excepting its southern portion, had become part of the dry 
 land of the continent, as is shown by the absence of marine 
 strata of later date. The great areas of progress were conse- 
 
284 MESOZOIC TIME. REPTILIAN AGE. 
 
 quently changed, and became (1) the Atlantic border, (2) 
 the Gulf border, and (3) the Western Interior, or region west 
 of the Mississippi. In other words, the continent, from the 
 Mesozoic onward, until the close of the Tertiary period in the 
 Cenozoic, was receiving its new marine formations along its 
 borders, and in extensive areas over the part of the Interior 
 region embraced by the Summit region and slopes of the 
 Eocky Mountains. 
 
 These three regions are continuous with one another, the 
 Atlantic connecting with the Gulf border region on the south, 
 and the Gulf border region passing northwestward into the 
 Western Interior or Eocky Mountain region and Pacific 
 border. 
 
 In Europe no analogous change can be distinguished ; for 
 the continent was, from the first, an archipelago, and it con- 
 tinued to bear this geographical character, though with an 
 increasing prevalence of dry land, until the Cenozoic era had 
 half passed. Western England then stood as three or four 
 islands above the sea (the area marked as covered by Paleo- 
 zoic rocks on the map, page 244) ; and the area of future rock- 
 making was mainly confined to the intervals between these 
 islands and to the submerged area on the east and southeast. 
 It is probable that this area and a portion of Northeastern 
 France were, geologically, part of a large German-Ocean basin. 
 
 REPTILIAN AGE. 
 
 Periods. The Eeptilian Age includes three periods : 
 7. TnQSSic: named from the Latin tria, three, in allusion to 
 the fact that the rocks of the period in Germany consist of 
 three separate groups of strata. This is a local subdivision, 
 not characterizing the rocks in Britain or in most other parts 
 of Europe. 
 
 2. Jurassic: named from the Jura Mountains, situated on 
 the eastern border of France, between France and Switzerland, 
 where rocks of the period occur. 
 
TRIASSIC AND JURASSIC PERIODS. 285 
 
 8. Cretaceous : named from the Latin creta, chalk, the chalk- 
 beds of Britain and Europe being included in the Cretaceous 
 formation. 
 
 1. Triassic and Jurassic Periods. 
 I. Rocks: Kinds and Distribution. 
 
 The American rocks of the Triassic period have not yet 
 been separated from those of the Jurassic, except in the re- 
 gion west of the Mississippi. 
 
 In the Atlantic-border region these rocks occupy narrow 
 ranges of country parallel with the Appalachian chain, fol- 
 lowing its varying courses. One of these ranges occupies the 
 valley of the Connecticut between Northern Massachusetts 
 and New Haven on Long Island Sound, and runs parallel 
 with the Green Mountains: it has a length of about 110 
 miles. Another the longest of them commences at the 
 north extremity of the Palisades, on the west bank of the 
 Hudson Eiver, and stretches southwestward through New 
 Jersey, Pennsylvania (here bending much to the westward, 
 like the Appalachians of the State, as shown in the map on 
 page 242), and reaching far into the State of Virginia, 
 Another stretches almost in the line of the last through 
 North Carolina, There is another along Western Nova Scotia, 
 These, and some other smaller areas, are indicated on the map 
 on page 195 by an oblique lining in which the lines run from 
 the right above to the left below. 
 
 The rocks are mainly sandstones and conglomerates, but 
 include some considerable beds of shale, and in a few places 
 impure limestone. The sandstones are generally red or 
 brownish-red. The freestone of Portland, near Middletown 
 in Connecticut, and of the vicinity of Newark in New Jer- 
 sey, are from this formation. The pebbles and sand of the 
 beds were derived mainly from metamorphic rocks alongside 
 of the regions in which they lie ; and from some of the 
 coarser layers large stones of granite, gneiss, and mica schist 
 
286 MESOZOIC TIME. KEPTILIAN AGE. 
 
 may be taken. The strata overlie directly, but unconform- 
 ably, these metamorphic rocks. Near Kichmoud in Virginia 
 and in North Carolina there are valuable beds of bituminous 
 coal. 
 
 The several ranges of this sandstone formation are remark- 
 able for the great number of trap dikes and trap ridges inter- 
 secting them (page 43). Mount Holyoke in Massachusetts, 
 Edst and West Rocks near New Haven in Connecticut, and 
 the Palisades on the Hudson are a few examples of these 
 trap ridges. Trap is an igneous rock, one that was ejected in 
 a melted state from a deep-seated source of fire, through fis- 
 sures made by a fracturing of the earth's crust. The dikes 
 and ridges are exceedingly numerous, and have the same gen- 
 eral course with the sandstone ranges. They are so associated 
 with the sandstone formation that there must have been 
 some connection in origin between the water-made and the 
 fire-made rocks. The proofs that the trap came up through 
 the fissures in a melted state are abundant ; for the wall-rock 
 of the fissures is often baked so as to be very hard, and is 
 sometimes filled with crystallizations, as of epidote, tourma- 
 line, garnet, hematite, etc., evidently due to the heat. 
 
 West of the Mississippi, in the Western Interior region 
 southwest of Southern Kansas, there is a sandstone formation, 
 containing much gypsum (and hence called the gypsiferous 
 formation), but barren of fossils, except an occasional frag- 
 ment or trunk of fossil wood, which is regarded as Triassic. 
 Triassic beds occur also in Colorado and New Mexico, Utah 
 and Nevada. Along with Jurassic strata they enter into the 
 constitution of the Elk and Wahsatch mountains, and the 
 Sierra Nevada. These western Jurassic beds in many places 
 contain fossils, but only rarely so the Triassic. 
 
 In the vicinity of the Black Hills, in the region of the 
 Upper Missouri, there are some beds of impure limestone con- 
 taining marine fossils which are true Jurassic. 
 
 In Europe, the Triassic rocks of Eastern France and Ger- 
 many, east and west of the Ehine, consist of a shell limestone 
 
TRIASSIC AND JURASSIC PERIODS. 287 
 
 (called in German MuscJielkalJc) between an underlying thick 
 reddish sandstone (Buntcr Sandsteiri) and overlying strata of 
 reddish and mottled marlytes and sandstone (Keuper of the 
 Germans). In England (see No. 6 on map, page 244), the 
 formation consists of reddish sandstone and marlytes ; it is 
 mostly confined to a region running north-northwest just east 
 of the Paleozoic areas, and to an extension of this region 
 westward to Liverpool bay (or over the interval between the 
 two main areas) and up the west coast. 
 
 This formation, in Europe, contains in many places beds 
 of salt, and is hence often called the Saliferous group. At 
 Northwich in Cheshire, in England, there are two beds of 
 rock-salt, 90 to 100 feet thick; and in Europe there are simi- 
 lar beds at Vic and Dieuze in France, and at Wurtemberg in 
 Germany. 
 
 The Jurassic rocks of Britain and Europe are divided into 
 three principal groups : 
 
 1. The Liassic (No. 7 a on map of England, page 244), con- 
 sisting of grayish compact limestone strata, called Lias. 
 
 2. The Odlytic (No. 7b on map, page 244), consisting mostly 
 of whitish and grayish limestones, part of them oolitic (page 
 37). One stratum, near the middle of the series, is a coral- 
 reef limestone, much like the reef-rock of existing coral seas, 
 though different in species of coral. Near the top of the series 
 there are some local beds of fresh-water or terrestrial origin, 
 in what is called the Purbeck group, and one on the island 
 of Portland is named, significantly, the Portland dirt-led. The 
 Solenhofen lithographic limestone is a very fine-grained rock 
 (thereby fit for lithography), of the age of the Middle Oolyte 
 occurring in Pappenheim in Bavaria. 
 
 3. The Wealdcn (No. 8 on the map of England), a series 
 of beds of estuary and fresh-water origin, mostly clay aud 
 sand, but partly of limestone. They occur in Southeastern 
 England. They are named Wcalden from the region where 
 first studied, called the Weald, covering parts of Kent, Surrey, 
 and Sussex. 
 
288 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 2. Life. 
 
 1. Plants. 
 
 The vegetation of the Triassic and Jurassic periods included 
 numerous kinds of Ferns, both large and small, Catamites, and 
 Conifers, and so far resembled that of the Carboniferous age. 
 But there were no forests or jungles of Lepidodendrids and 
 Slgillarids. Instead of these Carboniferous types, a group of 
 trees and shrubs sparingly represented in the later Carbon- 
 iferous, that of the Cycads, was eminently characteristic of 
 the Mesozoic world. This group Las now but few living 
 
 species, and among 
 
 Fig * 31( the genera, Cycas 
 
 and Zamia are those 
 whose names are 
 best known. The 
 plants have the as- 
 pect of Palms ; and 
 
 Fig 316 a. 
 
 CYC ADS- Fig. 316, Cycas circinalis (x 
 
 ; 316a,leaf of a living Zamia (x 
 
 there was, therefore, in the Mesozoic forests a min^lincr of 
 
 O iD 
 
 palm-like foliage v/itli that cf Coniferj (Sprues, Cypress, and 
 the like). But the Cycads arc nut true Palms. They are 
 
TRIASSIC AND JURASSIC PERIODS. 
 
 289 
 
 Fig. 317. 
 
 Gymnosperms, like the Conifers both in the structure of the 
 wood and in the fruit. The resemblance to Palms is mainly in 
 the cluster of great leaves at the sum- 
 mit, and in the appearance of the exte- 
 rior of the trunk. Fig. 316 represents, 
 much reduced, a modern Cycas, and 
 31 6 a the leaf of a living Zamia, one 
 twentieth the actual length. The fossil 
 remains of Cycads are either their 
 trunks or leaves. A fossil species from 
 the Portland dirt-bed is represented in 
 Fig. 317- The trunks of some Cycads 
 have a height of 15 or 20 feet. In 
 one important respect these Cycads 
 resemble the Ferns, that is, in the unfolding of the young 
 
 Figs 318-322 
 
 Stump of the Cycad, Mantellia 
 (Cycadeoidea) megalophylla 
 
 Fig. 318, Podozamites lanceolatus ; 319, Pterophyllum graminioides ; 320, Clathropteris rec- 
 tiusculus; 321, Pecopteris (Lepidopteris) Stuttgartensis ; 322, Cyclopteris linnaeifolia. 
 
290 MESOZOIC TIME. REPTILIAN AGE. 
 
 leaf, the leaf being at first rolled up into a coil, and grad- 
 ually unrolling as it expands. The Cycads thus combine 
 peculiarities of three orders of plants, Ferns, Palms, and 
 Conifers, and are examples, therefore, of what are called 
 comprehensive types. 
 
 Fossil plants are common in the coal-regions of Eichmond, 
 Virginia, and in North Carolina, and occur also in other 
 localities. Figs. 318, 319 are parts of the leaves of two 
 species of Cycads, from North Carolina. Figs. 320 to 322 
 represent a few of the ferns : Fig. 320, a Clathropteris, from 
 East Hampton, Mass. ; Fig. 321, a Pecopteris, from Eichmond, 
 Va., and the Trias of Europe ; Fig. 322, a Cyclopteris, from 
 Eichmond, Ya. Large cones of firs have also been found. 
 Several of the American plants are identical in species with 
 those of the European Triassic, and a few nearer to Jurassic 
 forms. 
 
 2. Animals, 
 a. American. 
 
 The American beds of the Atlantic border region are re- 
 markable for the absence of true marine life : all the species 
 appear to be either those of brackish water, or of fresh water, 
 or of the land. 
 
 1. Radiates and Mollusks. In the beds of the Atlantic 
 border Eadiates are unknown ; and the remains of Mollusks 
 are of doubtful character. The Jurassic beds of the Eocky 
 Mountain region and its western borders contain many spe- 
 cies, and the Triassic of California a few. 
 
 2. Articulates. The shells of Ostracoid Crustaceans are 
 common in New Jersey, Pennsylvania, Virginia, and 
 
 North Carolina, but have not yet been found in New 
 England. Fig. 323 represents one of the little shells 
 of these bivalve species, called an Esthcria. It was 
 long supposed to be Molluscan. The EstJierioe are 
 brackish-water species. 
 
 A few remains of Insects have been found, and, what is more 
 remarkable, the tracks of several species. These tracks were 
 
TRIASSIC AND JURASSIC PERIODS. 
 
 291 
 
 made on the soft mud, probably by the larves of the Insects, 
 for certain kinds pass their larval state in the water. Fig. 
 324 represents one of these larves found in shale at Turner's 
 Falls in Massachusetts; it resembles, according to Dr. Le Conte, 
 the larve of a modern Ephemera, or May-fly. Figs. 325, 326 
 are the tracks of Insects. Pro- 
 fessor Hitchcock has named 
 nearly 30 species of tracks of 
 Insects and Crustaceans. 
 
 3. Vertebrates. There are 
 evidences of the existence of 
 Fishes, Reptiles, Mammals, and 
 probably Birds. With the ap- 
 pearance of the last two types 
 the sub-kingdom of Vertebrates 
 was finally represented in all its ARTICULATES. Fig. 324 
 
 Figs 324-326 
 
 325 
 
 H 
 
 / 
 
 A 
 f\ 
 
 r\ 
 
 r* 
 
 classes. 
 
 mediseva ( x H) ; 325, 326, Tracks of Insects. 
 
 1. The Fislws found in the American rocks are all Ganoids, 
 although Selachian remains are common in Europe. Fig. 327 
 represents one of the species, reduced one half; the tail is half 
 vertebrated. In other species of these rocks it is not at all 
 vertebrated, being like that of modern Ganoids ; and in them 
 this old paleozoic feature of the Ganoids is finally lost. 
 
 Fig. 327- 
 
 Fig. 327, GANOID, Catopterus gracilis ( x ) ; a, Scale of same, natural size. 
 
 2. Amphibians, of the tribe of Labyrinthodonts (page 257), 
 appear to have reached their greatest size and numbers in the 
 Triassic period. A foreign species is mentioned on page 300. 
 
292 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 Footprints of the Connecticut valley beds appear to indicate 
 the existence of American species. Figs. 330, 330 a, and 331, 
 331 a represent tracks of two of these. But among the kinds 
 
 Figs. 328-332. 
 
 REPTILES. Fig. 328, Bathygnathns borealis(X J) ; 329, Belodon priscus ; 329 a, section 
 of same; 330, 330 , fore and hind feet of Anisopus Deweyanus (X 1) ; 331, 331 a, ibid, of 
 A. gracilis (X !) ; 33-2, 332 a, ibid, of Otozoum Moodii (X is)- 
 
 so referred some were biped in locomotion ; and these, accord- 
 ing to Marsh, were probably Dinosaurs, as described below. 
 
 3. True Reptiles. 1. Dinosaurs. The Dinosaurs were 
 so named from the Greek deivog, terrible, and oavpoz, lizard, 
 some species being of great size. They were the leading 
 life of North America in Triassic and Jurassic time. In 
 the East they are known from the thousands of footprints left 
 by them in the Connecticut valley and New Jersey, and to a 
 small extent from bones, and these chiefly from Pennsylvania 
 and North Carolina; and in Western America from huge 
 skeletons found in the Eocky Mountain region. Many, as the 
 tracks show, were biped in locomotion, while others were 
 quadruped-like. The bipeds were of two tribes In one, 
 the animals made %-tord Hrd-Hke tracks, as in Figs. 333, 
 334 ; in the other, broad 4-toed or 5-toed tracks, as in 
 
TRIASSIC AND JURASSIC PERIODS. 
 
 293 
 
 Fig. 332 a (Fig. 332 being the corresponding fore-foot). 
 The track represented in Fig. 333 is actually eighteen inches 
 long, and that of Fig. 332 a, twenty inches , and probably 
 each of these biped Dinosaurs stood over twenty feet high. 
 Some of the 3-toed tracks are accompanied by impressions of 
 fore-feet, proving that the animals were not birds, and render- 
 ing it probable that none were so. The biped march of these 
 species is a bird-like characteristic, and it is connected with a 
 more or less bird-like pelvis, and sometimes with hollow bones. 
 Fig. 328 represents a tooth of a Dinosaur from Prince Ed- 
 ward's Island. 
 
 Figs 333, 334. 
 
 331 
 
 Fig. 333, Track of Brontozoum giganteam (X e) ; 334, SSlub of saudstoue with tracks of 
 Birds? and Reptiles ( X go). 
 
 Jurassic Dinosaurs of enormous size have been described 
 by Marsh from beds in Wyoming and Colorado. One named 
 by him, Atlantosaurus, had the thigh bone over 6 feet long, 
 and a length of body of probably 60 feet, showing a magni- 
 tude before thought impossible in a terrestrial animal. 
 
 2. Lacertians, or Lizard-like spesies, Fig. 329 represents a 
 tooth from North Carolina referred to a Lacertian called Belo- 
 don prisons. 
 
 3, Enaliosaurs. Found in the Triassic of Nevada* 
 
294 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 Fig. 335. 
 
 4. Mammals. In the North Carolina Triassic have been 
 found two jaw-bones (Fig. 335) of a species of Marsupial 
 the division of Mammals to which the modern Opossum of the 
 same region belongs. Several other Marsupials have been de- 
 scribed by Marsh from Jurassic beds in Wyoming and Colorado. 
 
 The facts prove that the 
 land population of Mesozoic 
 America included Insect*, 
 Amphibians, Reptiles, and 
 Marsupial Mammals; and 
 that the forests which cov- 
 ered the hills were mainly composed of Conifers arid Cycads. 
 Birds may have been present also : for (1) remains of true 
 Birds have been found in the Jurassic of Europe ; (2) it seems 
 hardly probable that Mammals should have preceded Birds ; 
 and (3) Birds, because terrestrial arid of slender bones, are 
 the least likely of species to be preserved. 
 
 Jaw-bone of Dromatherium sylvestre. 
 
 The European and British rocks of these periods, especially 
 
 337 Pigs. 336-339 
 
 RADIATES: Fig. 336, Prionastrsea oblonga(aCoral) ; 337, Encrinus liliiformis (aCrinoid); 
 338, Cidaris Blumenbacliii (an Echinus) ; 339, Spine of same. 
 
TRIASSIC AND JURASSIC PERIODS. 
 
 295 
 
 of the Jurassic, abound in marine fossils, and afford a good 
 idea of the Mesozoic life of the ocean. The remains of ter- 
 restrial life are also of great interest, Marsupial Mammals 
 occurring in the Triassic beds, and birds in the Jurassic. 
 
 1. Radiates. Polyp-corals are common in some Jurassic 
 strata : they are related to the modern tribe of corals, and not 
 to the ancient. Fig. 336 represents one of the Oolytic spe- 
 cies. Oinoids are of many kinds, yet their number, as com- 
 pared with other fossils, is far less than in the preceding 
 ages ; and they are accompanied by various new forms of 
 Star-fishes and Echini (page 183). Fig. 337 represents one 
 of the Triassic Crinoids, the Lily-Encrinite, or Encrinus lilii- 
 f or mis ; Fig. 338, an Echinus, from the Ob'lyte, stripped of its 
 spines ; and Fig. 339, one of the spines separate. 
 
 2. Mollusks. Brachiopods are few compared with their 
 number in the Paleozoic. The last species of the Paleozoic 
 genera, Spirifer and Leptcena, lived in the early part of the 
 
 Figs. 340-343. 
 
 340 
 
 MOLLUSKS: Fig. 340, Spirifer Walcotti ; 341, Gryphsea incurva ; 342, Trigonia clavellata ; 
 343, Viviparus (Paludina) fluviorum. 
 
 Jurassic period. Fig. 340 represents one of these last of the 
 Spirifer group. Lamellibraiichs and Gasteropods abound in spe- 
 cies, and under various new, and manv of them modern, genera. 
 
296 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 Species of the genus Gryplicea were common in the Lias and 
 later Mesozoic rocks : they are related to the Oyster, but have 
 the beak incurved. Fig. 341 represents a Liassic species. 
 Trigonia (Fig. 342) is a characteristic genus of the Mesozoic ; 
 the name alludes to the triangular form of the shell : the 
 species figured is from the Oolyte. Fig. 343 represents a 
 fresh- water snail-shell, a very abundant fossil in the fresh- 
 water limestone of the Wealden, closely resembling many 
 modern species. 
 
 But the most remarkable and characteristic of all Mesozoic 
 Mollusks were the Cephalopods. This order passed its maxi- 
 mum as to number and size in the Mesozoic, and hundreds of 
 species existed. The last of the Paleozoic types of Ortlwcerata 
 
 Figs 344, 345. 
 
 S44 
 
 MOLLUSKS : Fig. 344, Ammonites Humphreysianus ; 345, A. Jason. 
 
 and Goniatites lived in the Triassic period. In the same pe- 
 riod species of Ammonites, one of the most characteristic of 
 Mesozoic groups, became common ; and, in the earliest Juras- 
 sic, the first of Belemnites, another peculiarly Mesozoic type, 
 appeared. 
 
 The Ammonites had external chambered shells like the Nau- 
 
TRIASSIC AND JURASSIC PERIODS. 297 
 
 till (page 181) and Goniatites. Two Oolytic species are repre- 
 sented in Figs. 344, 345. One of them (Fig. 345) has the 
 side of the aperture very much prolonged ; but the outer mar- 
 gin of the shell, whether prolonged or not, is seldom well 
 preserved. The partitions (or septa) within 
 the shells of Ammonites are bent back in 
 many folds (and much plaited within each 
 fold) at their junction with the shell, so as 
 to make deep plaited pockets. The front 
 view of the outer plate, with the entrances to 
 its side-pockets, are seen in Fig. 346. The 
 fleshy mantle of the animal descended into 
 these pockets, and thus the animal was aided 
 in holding firmly to its shell. The siphuncle 
 in the Ammonites is dorsal. The Paleozoic 
 Goniatites were of the Ammonite family, but Ammonites tornatus . 
 the pockets were much more simple, the flex- 
 ures of the margins of the partitions being without plications. 
 
 The fossil Belcmnite is the internal bone of a kind of Ce- 
 phalopod, analogous to the pen or internal bone (or osselet) of 
 a Sepia, or Cuttle-fish (see Fig. 351). It is a thick, heavy fos- 
 sil, of the forms in Figs. 347, 348, having a conical cavity 
 at the upper end. The fossils are more or less broken at this 
 extremity ; when entire, the margin of the aperture is elon- 
 gated into a thin edge, and sometimes, on one side, into a thin 
 plate of the form in Fig. 349. The animal had an ink-bag 
 like the modern Sepia ; and ink from these ancient Cephalo- 
 pods has been used in sketching their fossil remains. Fig. 
 350 represents one of the ink-bags of the Jurassic Cephalo- 
 pods. Fig. 351 is another related Cephalopod, showing some- 
 thing of the form of the animal, and also the ink-bag in place. 
 
 3. Articulates. The Articulates included various shrimps, 
 or craw-fishes (Fig. 352, a Triassic species), Crabs, and Te- 
 tradecapod (or 14-footed) Crustaceans (Fig. 353, representing 
 a species something like the modern Sow-bug), but no Tri- 
 lobites ; also Spiders (Fig. 354), and species of many of the 
 
298 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 orders of Insects. Fig. 355 is a Libeliula, or Dragon-fly, of 
 the Jurassic period, from Solenhofen ; and Fig. 356, the wing- 
 case of a beetle, from the Stonesfield Oolyte. 
 
 Figs. 347-351. 
 
 MOLLUSKS : Fig. 347, Belemnites clavatus ; 348, B. paxillosus ; 348 , Outline of section 
 of same, near extremity ; 319, View, reduced, of the complete osselet of a Belemnite ; 350, 
 Fossil ink-bags of a Cephalopod ; 351, Acanthoteuthi.s antiquus. 
 
 4. Vertebrates. The Fishes were chiefly Ganoids or Sela- 
 chians. In the Triassic beds of Europe, as in America, oc- 
 curred the last species of the vertebrated-tailed Ganoids, and 
 the^rs^ of those having the tail not vertebrated. Fig. 357 
 represents one of the latter kind from the Lias. Among the 
 
TRIASSIC AND JURASSIC PERIODS. 
 
 299 
 
 SJiarks (or Selachians) the Cestraciont tribe, one of the most 
 ancient, characterized by a pavement of grinding teetli (page 
 
 Figs 352-356. 
 
 ARTICULATES : Fig. 352, Pempliix Sueurii ; 353, Archieoniscus Brodiei ; 354, Palpipes 
 prisons ; 355, Libellula ; 356, Wing-case of a Buprestis. 
 
 178), still continued, and was very numerously represented. 
 There were also, in the Jurassic beds, Sharks having sharp- 
 
 Fig. 357 
 
 VERTEBRATE : Fig. 357, Restored figure of /Echmodus (Tetragonolepis) from the Lias 
 (x J) ; 367 a, Scales of same. 
 
 edged teeth like those of the tribe of Sharks that inhabits 
 modern waters. 
 
 The genus Ccratodus, represented by species in the Trias, 
 
300 MESOZOIC TIME. REPTILIAN AGE. 
 
 has living species in Australia ; and they are Ganoids, related 
 to the modern Dipnoans, or fishes that, like the Lepidosiren, 
 have both gills and lungs. 
 
 Amphibians were common in the European Trias, as in the 
 American, and some were of gigantic size. 
 
 Figs 358-360. 
 
 VERTEBRATES: Fig. 358, Skull of Mastodonsaurus giganteus ( x i); 359, Tooth of same 
 (x ); 360, Footprints of Cheriotherium (x y?). 
 
 Among the Triassic Amphibians, one frog-like Labyrintlio- 
 dont had a skull over 2 feet long, of the form shown in Fig. 
 358 ; its mouth was set round with teeth 3 inches long (Fig. 
 359), and the body was covered with scales. The specimen 
 here figured was found iu Saxony. Tt is probable that some 
 of the American Reptilian species whose tracks are so com- 
 mon in the Connecticut Valley were of this type. Fig. 360 is 
 a reduced view of hand-like tracks, from the same locality as 
 the above, supposed to have been made by an animal of the 
 same species. The frogs of the present day are feeble and 
 diminutive compared with the Triassic Amphibians. 
 
 The True Reptiles included species for each of the elements > 
 the water, the earth, the air. 
 
 Among them there were, first, Swimming Reptiles, called 
 Enaliosaurs because they belonged especially to the sea (from 
 the Greek eVaXto?, of the sea, and aavpos, lizard) ; they prob- 
 
TRIASSIC AND JURASSIC PERIODS. 
 
 301 
 
 ably existed in the Carboniferous age (page 258), but became 
 numerous and of great size in the Middle Mesozoic. They 
 had paddles like Whales, and thus were well fitted for marine 
 life. The most common kinds were the Ichthyosaurs and Ple- 
 siosaurs. 
 
 Figs. 361-365 
 
 VEHTE3AATES : Fi-. 361, Ichthyosaurus communis (X ifo); 362, Head of same (X jfo) 5 
 3u3 o, 303 b, View and section of vertebra of same (X i) ; 364, Tooth of same, natural 
 size : 3oa, Plesiosaurus dolicliodeirus (x g^) > 365 a > 365 b > View and section of vertebra 
 of same. 
 
 The Ichthyosaurs (Fig. 361) had a short neck, a long and 
 large head, enormous eyes, and thin, doubly-concave, and 
 therefore fish-like, vertebrae. The name is from the Greek 
 Ix0vs> fi*h> an( i travpos, lizbrd. Fig. 362 represents the head 
 of an Iclithyosaur, one thirtieth the natural length, showing 
 the large size of the eye and the great number of the teeth. 
 Fig. 363 b is one of the vertebrtc, reduced, and Fig. 363 , a 
 transverse section of the same, exhibiting the fact that both 
 surfaces are deaply concave, nearly as in fishes ; Fig. 364 is 
 one of the teeth, natural size. Some of the Ichthyosaurs were 
 30 feet long. 
 
302 MESOZOIC TIME. REPTILIAN AGE. 
 
 The Plesiosaurs (named from the Greek TrXrja-ios, near, and 
 craiJpo?, because not quite like a Saurian), one of which is rep- 
 sented very much reduced in Fig. 365, had a long snake-like 
 neck, a comparatively short body, and a small head. Fig. 
 365 a represents one of the vertebrae, and 365 b, a section 
 of the same ; it is doubly concave, but less so, and much 
 thicker, than in the Iclithyosaurs. Some species of Plesiosaur 
 were 25 to 30 feet long. Another related Eeptile, called a 
 Pliosaur, was 30 to 40 feet long. Remains of more than 50 
 species of Enaliosaurs have been found in the Jurassic rocks. 
 
 Besides these swimming Saurians, there Avere numerous 
 species of Lacertians (Lizards) and Crocodilians 10 to 50 feet 
 long, and Dinosaurs, the bulkiest and highest in rank of the 
 Saurians, 25 to 60 feet long. 
 
 To the group of Dinosaurs belongs the Iguanodon, of the 
 Wealden beds, first made known by Dr. Mantell, whose body 
 was 28 to 30 feet long, and which stood high above the 
 ground quadruped-like, the femur, or thigh-bone, alone being 
 nearly 3 feet long. The hind feet were three-toed like those 
 of birds. Its habits are supposed to have been like those of 
 the ancient sloth-like animal called a Megatherium (page 365), 
 the animal grazing on the trees along the borders of the 
 marshes, estuaries, or streams in or about which it lived, and 
 able to lift its body on its hind legs for this purpose. It had 
 teeth li*ke the modern Iguana, (and hence the name, from 
 Iguana, and the Greek o8ou?, tootJi), but it had proportionately 
 a much shorter tail. The Megalosaur was another of the 
 gigantic Dinosaurs of the later part of the Jurassic period ; 
 it was a terrestrial carnivorous Saurian about 30 feet in length, 
 and was better fitted in its limbs for raising its body toward 
 an erect posture. The three-toed American Reptiles, whose 
 tracks are described on page 293, are those of other Dinosaurs ; 
 and these had the habit of bipeds. Many points in the 
 structure of the limbs and pelvis of the Dinosaurs are similar 
 to those of birds. 
 
 Reptiles adapted for the air that is, for flying are 
 
TRIASSIC AND JURASSIC PERIODS. 303 
 
 designated Pterosaurs, from the Greek Trrepov, winy, and 
 aavpos. The most common genus is called Pterodactylus. 
 The general form of a Pterodactyl is shown in Fig. 366. The 
 bones of one of the fingers are greatly elongated, for the purpose 
 
 Fig. 366. 
 
 VERTEBRATE. Pterodactylus crassirostris (x }) 
 
 of supporting an expanded membrane, so as to make it serve 
 (like an analogous arrangement in bats) for flying. The name 
 Pterodactyl is from the Greek irrepov, wing, and $aKTv\o$, 
 finger. The Jurassic Pterodactyls were mostly small, and 
 probably had the habits of bats ; the largest had a spread of 
 wing of about 10 feet. Unlike our common birds, they had 
 a mouth full of teeth, and no feathers. As Bats are flying 
 Mammals, so the Pterosaurs are simply flying Reptiles, and 
 have little resemblance to birds iu structure, except that 
 their bones are hollow, and adapted in form for the bird- 
 like characteristic of flying. 
 
 Besides the kinds of Eeptiles already mentioned, there were 
 Turtles in the Jurassic period; but, according to present 
 knowledge, the world contained no true Snakes. 
 
 Coprolites (or fossil excrements) of both Reptiles and Fishes 
 are common in the bone- beds. When cut and polished they 
 
304 MESOZOIC TIME. REPTILIAN AGE, 
 
 Fig. 367 
 
 TERTEBRATE. - The binl, Archaopteryx macrura. 
 
TRIASSIC AND JURASSIC PERIODS. 
 
 305 
 
 have a degree of beauty sufficient to give them some value in 
 jewelry. 
 
 Eemains of Birds have been found in the quarries of Solen- 
 hofen (page 287). They have revealed the fact that some at 
 least of the Mesozoic Birds (and of America, beyond question, 
 as well as Europe) were reptilian in some of their characters. 
 The skeleton found (Fig. 367) shows that the Birds had long 
 reptile-like tails consisting of many vertebrae, and finger-like 
 claws on the fore limb or wing, like those of the Pterodactyl 
 and Bat, fitting them evidently for clinging. But, while 
 thus reptilian in some points of structure, they were actually 
 Birds, being feathered animals, and having the expanse of 
 the wing made, not by an expanded membrane as in the 
 Pterodactyl, but by long quill-feathers. The tail-quills were 
 
 Figs 368, 369. 
 
 VERTEBRATES. Fig. 368, Amphitherium Broderipii (x2); 369, PKascolotherium 
 Bucklandi (x 2). 
 
 arranged in a row either side of the long tail. Th<e feet were 
 like those of birds. 
 
 Remains of Mammals occur in the Upper Trias (or base 
 of the Lias) of Germany, in the Lower Oolyte deposit at 
 Stonesfield, England, and in the Middle Purbeck beds of the 
 Upper Oolyte (page 287). Nearly 20 species have been made 
 out, 14 of them from relics in the Middle Purbeck. The 
 larger part, if not all, are Marsupials. Figs. 368, 369 repre- 
 sent the jaws of two species from Stonesfield, magnified twice 
 the natural size. 
 
 20 
 
306 MESOZOIC TIME. EEPTILIAN AGE. 
 
 As Marsupials are semi-oviparous Mammals, and therefore 
 are intermediate between ordinary Mammals and the inferior 
 and oviparous Vertebrates (page 176), it follows that both the 
 Birds and Mammals of the Mesozoic were in part, at least., 
 comprehensive or intermediate types, and partook of reptilian 
 features in the Eeptilian age. 
 
 3. General Observations. 
 
 1. American Geography. The Triassico-Jurassic sand- 
 stones and shales of the Atlantic border region are sedimen- 
 tary beds ; consequently, the long narrow ranges of country 
 in which they were formed were occupied at the time more or 
 less completely by water. 
 
 The absence of true marine fossils has been remarked upon 
 as proving that this water was either brackish or fresh ; and 
 hence the areas were estuaries or deep bays running far into 
 the land. 
 
 There was probably an abundance of marine life in the 
 ocean, if we may judge from its diversity on the other side 
 of the Atlantic ; but the sea-coast of the era must have been 
 outside of the present one, so that any true marine or sea-coast 
 deposits that were made are now submerged. The present 
 sea-border is shallow for a distance of 80 miles from the New 
 Jersey coast, the depth of water at this distance out being 
 but 600 feet. (See map, page 12.) 
 
 As all the depressions or valleys occupied by the estuaries 
 are parallel with the Appalachians (page 285), and since the era 
 of the formations was that next following the origin of these 
 mountains, the depressions were probably made at the time 
 the Appalachian foldings were in progress, or are great valleys 
 or depressions then left in the surface. 
 
 The level of the several sandstone areas above the ocean 
 proves that the land at the time was not far from its present 
 elevation, and therefore that the Appalachians had probably 
 nearly their present height. 
 
 The deposits contain footprints, ripple-marks, rain-drop 
 
TRIASSIC AND JURASSIC PERIODS. 307 
 
 impressions, and other evidences, on many of the layers, that 
 they were formed partly in shallow waters, and partly as 
 sand-flats, or emerging marshes and shores, over which reptiles 
 and birds might have walked or waded. If, then, they are 
 several thousands of feet thick, there must have been a 
 progressing subsidence of the valley-depressions, that is, a 
 sinking must have been going on. It is hence apparent that 
 oscillations of level, like those that characterized the Appala- 
 chian region before and during the Appalachian revolution, 
 were in progress. Two effects of this subsidence occurred : 
 (1) The sandstone beds were more or less faulted and tilted, 
 those of the Connecticut Valley receiving a dip to the eastward, 
 or southeastward, those of New Jersey and Pennsylvania to 
 the northwestward. (2) In the sinking of the valley-depres- 
 sion, an increasing strain was produced in the earth's crystal- 
 line crust beneath, which finally became so great that the crust 
 broke, fissures opened, and liquid rock came up. The dikes 
 and ridges of trap are this liquid rock solidified by cooling. 
 The existence of the dikes, and their parallelism to the general 
 course of the valley-depressions, prove (1) the fact of the 
 fractures ; (2) their resulting from the same cause which pro- 
 duced the sinking ; and (3) the fact of the igneous ejections. 
 The earth's crust along the Connecticut Valley was thus a 
 scene of igneous operations for more than 100 miles, and 
 through a vast number of opened fissures. All the Trias- 
 sico-Jurassic areas from Nova Scotia to Southern North Caro- 
 lina, a distance of 1,000 miles, were similarly broken through 
 and invaded by trap ejections. The Palisades of the Hudson 
 date from this period, probably the middle or later part of 
 the Jurassic period. 
 
 The Western Interior or Rocky Mountain region had been 
 mostly submerged during the Carboniferous age, as shown by 
 the fact that limestones were forming there in the Coal-Meas- 
 ure period, and fossiliferous sandstones in the Permian. The 
 Triassic sandstone there proves, by its nature, its gypsum in 
 many places, and the paucity of fossils, that, by some change, 
 
308 MESOZOIC TIME. REPTILIAN AGE. 
 
 the region had become mostly an interior shallow salt sea, 
 shut off to a great extent from the ocean. Such a sea would 
 have been made too fresh for marine life in the rainy season, 
 and probably too salt for almost all life in the hot season. 
 Hence, life would have been nearly or quite absent. The 
 salt waters by evaporation would have furnished gypsum to 
 the beds, as happens now sometimes from sea-water. It fol- 
 lows, then, from the beds of the Atlantic border as well as 
 those of the Western Interior, that the continent during the 
 era of these Mesozoic beds was to a less extent submerged 
 than in the greater part of the Paleozoic ages and the follow- 
 ing portion of the Mesozoic. The fossiliferous Jurassic beds 
 overlying the western Triassic show that, before the Jurassic 
 period had closed, the sea had again free access over it and 
 oceanic life was abundant. 
 
 2. Foreign Geography. The nature of the Triassic beds 
 of Britain and Europe shows that there were large shallow in- 
 terior seas also on the eastern .jicie of the Atlantic. The salt- 
 deposits in the beds, the paucity of fossils in the most of the 
 strata, and the prevalence of maiiytes, indicate the same coa- 
 ditions as existed in New York during the formation of the 
 Saliferous beds of the Upper Silurian (see page 100), and 
 somewhat similar to those in which the Eocky Mountain 
 Gypsiferous formation originated. The limestone that inter- 
 vened along the Rhine, between the two formations of sand- 
 stone and marlytes, shows an interval of more open sea ; yet 
 the impurity of the limestone suggests that the ocean had not 
 full sweep over the region. 
 
 The beds of the Jurassic period are almost all of them 
 evidence, both from their constitution and their abundant 
 marine life, that the free ocean again had sway over large 
 portions of the Continental area. Its limits in Great Britain, 
 however, became more contracted as the period passed, and 
 toward its close fresh- water and terrestrial beds were forming 
 in some places that had earlier in the period been under salt 
 water. 
 
TRIASSIC AND JURASSIC PERIODS. 309 
 
 3. Climate. The Jurassic coral-reefs of Britain indicate 
 that England then lay within the sub-tropical oceanic zone. 
 This zone now has the parallel of 27 to 28 as, in general, its 
 outer limit (lying mostly between 20 and 27) ; and, conse- 
 quently, its Jurassic limit, if including England, reached twice 
 as far toward the pole as now. It is possible, however, that 
 the line would have run along the British Channel, were it 
 not for the Gulf Stream of the era, which carried the sub- 
 tropical temperature northeastward through the British seas, 
 as it now does to Bermuda, in latitude 34. 
 
 The following are other facts of similar import. In Arctic 
 America species of shells allied to those of Europe and tropi- 
 cal South America occur in latitudes 60 to 77 1C'; and one 
 species of Belewinite and one of Ammonite are said to be iden- 
 tical with species occurring in these two remote and now 
 widely different regions. If not absolutely identical, the evi- 
 dence from them as to oceanic temperature is nearly the 
 same. Moreover, on Exmouth Island, in 77 16' N., remains 
 of an Ichthyosaur have been found, and in 76 22' N., on 
 Bathurst Island, bones of other large Jurassic Eeptiles (Teleo- 
 saurs). It is probable, therefore, that a warm-temperate 
 oceanic zone covered the Arctic to the parallel of 78, if not 
 beyond. No large living reptiles exist outside of the warm- 
 temperate zone. 
 
 DISTURBANCES CLOSING THE JURASSIC PERIOD. 
 
 After the Jurassic period, or near its close, the lofty ranges 
 of the Sierra Nevada, on the eastern boundary of California 
 and the western of the Great Plateau or Basin were made ; 
 and probably also the Huinboldt Eange, above 12,000 feet in 
 height, and other ranges over the dry plateau between the 
 Sierra Nevada and the Wahsatch Eange. Triassic and Ju- 
 rassic fossils have been found in the rocks of the Sierra Ne- 
 vada, while Cretaceous fossiliferous beds lie unconformably 
 over the upturned strata of the mountains; the latter fact 
 
310 MESOZOIC TIME. REPTILIAN AQE. 
 
 proving that the mountain-making occurred before the Creta- 
 ceous era, and the former, that it took place after the Juras- 
 sic era. The ejections of trap in the Triassico-Jurassic areas 
 of the Atlantic border occurred previous to the Cretaceous 
 period, and perhaps contemporaneously with the making of 
 the mountains on the Pacific border. 
 
 2. Cretaceous Period. 
 
 General characteristics, The Cretaceous, while the closing 
 period of Mesozoic time, was also, in some respects, a tran- 
 sition era between the Mesozoic and Cenozoic. During its 
 progress, as is explained beyond, occurred the decline, and, at 
 its close, the extinction, of a large number of the tribes of the 
 mediaeval world, while, at the same time, there appeared in 
 its course other tribes eminently characteristic of the modern 
 world. Among the modernizing features, the most prominent 
 are the Palms and Angiosperms among plants, and the Teliosts 
 among fishes. 
 
 The Palms and Angiosperms include nearly all the fruit- 
 trees of the world, and constitute far the larger part of mod- 
 ern forests. The Conifers and Cycads, wherever they now 
 occur near groves of Angiosperms, exhibit the contrast be- 
 tween the mediaeval foliage and that of the present age The 
 Teliosts (page 176) embrace nearly all modern fishes excepting 
 those of the order of Sharks, or Selachians. Their prevalence 
 was as great a change for the waters as the new tribes of 
 plants for the land. 
 
 I. Rocks: Kinds and Distribution. 
 
 In North America, the Cretaceous formation borders the 
 continent on the Atlantic side, south of New York, and along 
 the north and west sides of the Gulf of Mexico ; besides, it 
 spreads up the Mississippi Valley to the mouth of the Ohio ; 
 aod, more to the westward, from Texas, northward, over the 
 slopes of the Rocky Mountains, being now at a height in some 
 
CRETACEOUS PERIOD. 311 
 
 places of 10,000 to 12,000 feet above the sea. Its beds are 
 exposed to view in New Jersey and iri some portions of the 
 more southern Atlantic States, though mostly covered by the 
 Tertiary. They are largely displayed through Alabama and 
 Mississippi, and cover a great area west of the Mississippi. 
 (See map, page 195.) In the Eocky Mountain region they 
 occur east of the Wahsatch, and south in Colorado, New 
 Mexico, and beyond; also west of the Sierra Nevada iu 
 California of great thickness. In Colorado and New Mexico, 
 and on Vancouver's Island, there are valuable beds of brown 
 coal (sometimes called lignite) in the Cretaceous formation. 
 The coal-beds of Wyoming and Utah, near the Central 
 Pacific Eailroad, and part of those to the south, are made 
 Cretaceous by some geologists, and by others, Tertiary. 
 
 In England the formation occupies a region just east of 
 the Jurassic, stretching from Dorset on the British Channel 
 eastward, and also northeastward to Norfolk, on the German 
 Ocean, and continuing near the borders of this ocean, still 
 farther north, beyond Flamborough Head : it is numbered 9 
 on the map, page 244. Cretaceous rocks occur also in North- 
 ern and Southern France, and many other parts of Europe, 
 covering much of the territory between Ireland and the 
 Crimea, 1,140 miles in breadth, and, between the south of 
 Sweden and south of Bordeaux, 840 miles. 
 
 Among the rocks there are the following kinds : the soft 
 variety of limestone called chalk ; hard limestones ; ordinary 
 hard sandstones ; shales and conglomerates like those of other 
 ages ; but, more common than these, soft sand-beds, clay-beds, 
 and shell-beds, so imperfectly consolidated that they may be 
 turned up with a pick. 
 
 Many of the sand-beds or sandstones have a dark green 
 color, and are called (jrcm-sand. The green color is owing to 
 the presence of dark green grains which occur mixed with 
 more or less of common sand. They are a hydrous silicate of 
 iron and potash. This green-sand is often used for fertilizing 
 land, and when so used it is called marl ; it is extensively 
 quarried for this purpose in New Jersey, 
 
312 MESOZOIC TIME. REPTILIAN AGE. 
 
 Chalk-beds are the source of flint. The flint is distributed 
 through the chalk iu layers, these layers being made up of 
 nodules of flint, or masses of irregular forms. Although often 
 of rounded forms, they are not water-worn stones of foreign 
 origin, but were formed in place, like the Jiornstone in the 
 Corniferous limestone of New York (page 229). 
 
 Chalk constitutes a large proportion of the Cretaceous for- 
 mation in England and some parts of Europe. It occurs in the 
 Cretaceous of Western Kansas, but not on the Atlantic border. 
 
 The succession of beds in England is as follows : 1. The 
 Lower Cretaceous, consisting largely of the Green-sand and 
 other arenaceous beds, called collectively the Lower Green- 
 sand; 2. The Middle Cretaceous, containing the Upper Green- 
 sand and some other beds ; 3. The Upper Cretaceous, compris- 
 ing the Chalk-beds, the lower part of which is without flints. 
 
 The Cretaceous beds in North America consist of layers of 
 ^Green-sand, thick sand-beds of other kinds, clays, shell-beds, 
 and, in some places in the States bordering on the Mexican 
 Gulf (especially in Texas), limestone. The thickness of the 
 formation in New T Jersey is 400 to 500 feet ; in Alabama, 
 2,000 feet ; in Texas about 800, nearly all of it compact lime- 
 stone ; in the region of the Upper Missouri, 2,000 to 2,500 
 feet ; east of the Wahsatch, 9,000 feet or more. 
 
 2. Life. 
 
 1. Plants. 
 
 The first of Angiosperms and of Palms, as already stated, 
 $ate from the Cretaceous period. Leaves of a few American 
 species of the former are represented in Figs. 370 - 373 ; Fig. 
 ,')71, of a species of Sassafras ; Fig. 372, a Liriodendron ; and 
 Fig. 373, a Willow ; and with these occur leaves of Oak, Dog- 
 wood, Beech, Poplar, etc. 
 
 Besides these highest of plants, there were also Conifers, 
 Ferns, and Sea-weeds, as in former time, with some Cycads. 
 The microscopic Algse called Diatoms (page 187), which make 
 
CRETACEOUS PERIOD. 
 
 313 
 
 siliceous shells, and others called Desmids (page 187), which 
 consist of one or a few simple green cellules, were very abun- 
 dant. Both occur fossil in flint ; and a species of the latter 
 
 :570 
 
 Figs. 370-373. 
 
 Fig. 370, Leguminosites Mareouanus; 371, Sassafras Cretaceum ; 372, Lir.ndendron Meekii; 
 373, Salix Meekii. 
 
 is very similar to one from the Devonian hornstone figured 
 on page 234 (Fig. 241). The Diatoms are believed to have 
 contributed part of the silica of which the flint is formed. 
 
 2. Animals. 
 
 1. Protozoans. The simplest of animals, Rliizopods, of the 
 group of Protozoans (page 185\ were of great geological im- 
 portance in the Cretaceous period ; for the Chalk is supposed 
 to be made mostly of their minute calcareous shells. The 
 powdered chalk is often found to contain large numbers of 
 these shells, the great majority of which do not exceed a 
 
314 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 Fig. 374. Euplectella specioea, or Glass Sponge, 
 
CRETACEOUS PERIOD. 
 
 315 
 
 pin's head in size. A few of the forms are represented in 
 Figs. 375 to 379, all very much enlarged, except 379, which 
 is natural size. A very common kind resembles Fig. 83, (page 
 
 Figs. 375-379- 
 
 879 
 
 RHIZOPODS : Fig. 375, Lituola nautiloidea ; 376, Flabellina rugosa , 377, Chrysalidina 
 gnulata ; 378, Cimeolina pavonia ; 379, Orbitolina Texana. 
 
 66), and is called a Rotalia. Fig. 379 represents a large disk- 
 shaped species, called an Orbitolina, from Texas. 
 
 Besides the above Protozoans, Sponges were also very 
 abundant, and their siliceous spicules (page 185) were another 
 important source of the silica of the 
 flints. Some of the Sponges, both 
 of the Cretaceous era and of mod- 
 ern time in the deeper seas, consist 
 wholly, or nearly so, of silica. One 
 of the modern species, from deep 
 water in the Indian Ocean, is rep- 
 resented in Fig. 374. It consists of 
 a delicate network of fibres of silica, 
 and looks as if made of spun glass. 
 The Ventriculites were large Creta- 
 ceous sponges of similar character, having an inverted conical 
 shape. Fig. 380 represents another kind which was prob- 
 ably siliceous. 
 
 2. Radiates. Mollusks. Corals and Echini were Common 
 among Eacliates. Mollusks abounded, both of the Ammonite 
 and Belemnite types, besides others of genera not peculiar to 
 the Mesozoic. Many of the genera are represented in mod- 
 ern seas. 
 
 SPONGE. Siphonia lobata. 
 
316 MESOZOIC TIME. REPTILIAN AGE. 
 
 Figs. 391-393 are of some of the most characteristic La- 
 in ellibranchs from the American Cretaceous ; Fig, 391, an 
 Exogyra ; Fig. 392, an Inoceramus ; Figs. 393, 394, species of 
 Gryphcea, genera now extinct. Figs. 395, 396, represent 
 shells of Gasteropods, and 397 to 401, Cephalopoda, all 
 American except 399 ; Fig. 397, an upper front view of an 
 Ammonite, showing the pockets along the sides of one of the 
 partitions ; Fig. 397 a, a reduced view of the same Ammonite 
 in profile ; Figs. 398 to 400, three species of the Ammonite 
 family, but not true Ammonites, one, Fig. 398, being called 
 a ScapMtes (from the Latin scapha, a skiff \ resembling an 
 
 Figs. 391-394 
 
 JVIOLLUSKS : Fig, 391, Exogyra costata ; 392, Inoceramus problematicus ; 393, Gryphseo 
 vesicularis ; 394, G. Pitched. 
 
 Ammonite with the shell partly uncoiled, and thus made 
 somewhat to resemble a boat ; Fig. 399, a Turrilites, or tur- 
 reted Ammonite, an anomaly in the family, as the species are 
 almost all coiled in a plane ; Fig. 400, a Baculites, or straight 
 Ammonite, so named from the Latin bacculum, a walking-stick. 
 Some of the Ammonites of the Cretaceous period are 3 to 4 
 feet in diameter. 
 
 Fig. 401 represents a common New Jersey Belemnite. 
 
CRETACEOUS PERIOD. 
 
 317 
 
 3. Vertebrates, Among Vertebrates there were great num- 
 bers of the Tcliost or Osseous Fishes, fishes allied to the 
 
 897 
 
 Figs 395-401. 
 
 MOLLUSKS : Fig. 395, Fasciolaria buecinoides ; 396, Pyrifusus Newberryi ; 397, Ammo- 
 nites placenta ; 397 cr, id., in profile, reduced ; 39S, Scaphites larvaeformis ; 39f>, Turrilites 
 catena tus ; 400, Baculites ovatus ; 401, Belemnitella mucronata. 
 
 perch, salmon, pickerel, etc. They occur along with nurner- 
 
318 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 ous Sharks of both ancient and modern types (Cestracionts 
 and Squalodonts), and many also of Ganoids. Thus the an- 
 ' cient and modern forms of fishes were united in the popu- 
 lation of the Cretaceous seas, the former, however, making 
 
 Fig. 402. 
 
 Osmeroides Lewesiensis ( x |). 
 
 hardly more than a tenth of the species. Fig. 402 represents 
 one of these Teliost Fishes, related to the Salmon and Smelt, 
 
 Figs. 403, 404. 
 
 MOSASATJRS Fig, 403, Mosasaurus Hoffmanni ( x iV) > 404, Side of jaw of Edestosaurus 
 
 dispar(xi). 
 
CRETACEOUS PERIOD. 
 
 319 
 
 Fig. 405. 
 
 tr om the Chalk at Lewes, England. There were also Herring, 
 and many other kinds. 
 
 The Reptiles included species of several of the Jurassic 
 genera. Of these, there were PTEROSAURS, of the genus Ptero- 
 dactylus, and others, some, from Kansas rocks, 20 to 25 feet 
 in expanse of wing ; ENALIOSAURS, or Sea-Saurians, of the 
 genera Ichthyosaurus, Plesiosaurus, etc., 10 to 50 feet long; 
 and DINOSAURS, of the genera Iguanodon, Hadrosaurus, Lcelaps 
 (related to the Megalosaurs), etc., some of them fitted to raise 
 themselves and walk on their hind feet, like the three-toed 
 Reptiles of the Triassico-Jurassic era, in the Connecticut 
 Valley (page 293). 
 
 There was also a tribe, unknown before the Cretaceous, that 
 of the MOSASAURS : great snake-like Reptiles, 15 to 75 feet 
 long, swimming by means of four paddles, 
 literally the Sea-Serpents of the era. 
 The remains of the head of one, from the 
 banks of the river Meuse in Holland 
 (whence the name), are represented in Fig. 
 403. The American rocks have afforded 
 forty species of these Mosasaurs. The head 
 of the largest was four feet long, and the 
 mouth was hence of enormous size. Be- 
 sides, it had a joint in the lower jaw, either 
 side, in place of the usual suture (at a, in 
 Fig. 404), which enabled the two sides of a 
 jaw, as the bones (rami) w T ere not united at 
 their extremities, to act like a pair of arms, 
 iu working down the immense throat any 
 large animal it might undertake to swallow 
 whole. A tooth of one of the Mosasaurs, 
 half the natural size, is shown in Fig. 405. 
 
 Among more modern kinds of Reptiles 
 
 ,n . ,., .. Tooth of Mosasaurus prin 
 
 there were Crocodiles and Turtles; one of ceps(xi). 
 
 the latter, from Kansas, 15 feet in breadth, 
 
 according to Cope, between the tips of the extended flippers. 
 
320 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 Fig. 406-411. 
 
 HESPERORNIS REGALIS, 
 
 X & ; 407, lower jaw x ; 408,' 
 tooth X 4 ; 409, 410, vertebra} 
 X z ; 411, pelvis, side view 
 X s ' H, ilium ; is, ischium ; 
 1>, pubis ; a, acetabulum. 
 
CRETACEOUS PERIOD. 
 
 321 
 
 The Birds in America included Divers, Cormorants, Wad- 
 ers. Some of them, as made known by Marsh, had teeth 
 
 Fig. 
 
 Ichtliyornis victor of Marsh. 
 
 like a Eeptile. Fig. 406, from Marsh, represents the skele^ 
 ton of Hesperornis regalis, one-eighth the natural size, a 
 
 23 
 
322 
 
 MESOZOIC TIME. REPTILIAN AGE. 
 
 gigantic Diver, 5 to 6 feet in height, between an Ostrich and 
 a Loon in structure; and Fig. 412, Ichthyornis victor, half 
 the natural size, a bird as large as a pigeon. The latter had 
 biconcave vertebrae, like Fishes and Ichthyosaurs. 
 
 3. General Observations. 
 
 1. Geography. In North America the position of the Cre- 
 taceous beds along the borders of the Atlantic south of New 
 York, near the Mexican Gulf, and also over a large part of 
 the Rocky Mountain region, indicates that these border re- 
 gions and a large part of the Western Interior were under 
 
 Tig. 413. 
 
 North America in the Cretaceous Period ; MO, Upper Missouri region. 
 
 water when the period opened, as represented in the above 
 map (Fig. 413). The shaded part of the continent exhibits 
 the extent to which it was submerged. (This map should be 
 
CRETACEOUS PERIOD. 
 
 compared with that on page 199.) It shows that the Chesa- 
 peake and Delaware gulfs were in the ocean ; that Florida 
 was still under water ; that the region of the Missouri Eiver 
 was a salt-water region ; that the Eocky Mountain region was 
 largely submerged. This mountain region was in some parts 
 at least 10,000 feet lower than now, the Cretaceous beds hav- 
 ing this elevation upon it. The Mexican Gulf spread over 
 a large part of Georgia, Alabama, and Mississippi, extended 
 northward to the mouth of the Ohio, and then, west of 
 Missouri and Kansas, stretched far north over the present 
 slopes of the great Western mountains, reaching perhaps to 
 the Arctic Ocean, though on this point the evidence is not yet 
 decisive. The deposits, excepting those of Texas, appear to 
 be of sea-shore and off-shore formations ; the Texan compact 
 limestones were probably formed in clear interior waters. 
 
 In Europe the Chalk appears to have been accumulated in 
 an open sea, where the water was some hundreds of feet deep. 
 The material of the Chalk has been stated on page 313 to be 
 mainly the shells of Rhizopods, and that of the associated flint 
 to have been derived largely from Diatoms and Sponges.) 
 Ehizopods, Diatoms, and Sponges are now living in man}/ 
 parts of the ocean, over the bottom, even where the depth is 
 thousands of feet ; and the Ehizopods are making chalk-like 
 accumulations of vast area. There are, hence, in the present 
 seas, the conditions requisite for making chalk, and also flint. 
 The fossils of the Chalk are in many regions turned into flint, 
 and some hollow specimens are filled with quartz crystals, or 
 
 2. Climate. The corals and other tropical life of the rock;^ 
 indicate that the British seas were at least warm-temperate 
 to latitude 60 north. On the American side the temper- 
 ature of the waters appears to have been cooler, as it now 
 is, in corresponding latitudes ; and still it was considerably 
 warmer than the present. The warm oceanic zone which 
 spread over the British seas appears, from the distribution of 
 the fossils, to have reached the North American coast south 
 
324 MESOZOIC TIME. 
 
 of Long Island, and probably had no place on the coast north 
 of Cape Hatteras. The plants of the Upper Missouri region 
 indicate a warm-temperate climate over that territory. 
 
 GENERAL OBSERVATIONS ON THE MESOZOIC. 
 
 1. Time-Ratios. The ratios between the Paleozoic ages as 
 to the length of time that elapsed during their progress, or 
 their time-ratios, are stated on page 269 as probably not far 
 from 4:1:1. By the same method, it follows that the ratio for 
 the time of the Paleozoic and Mesozoic was nearly 4:1; and 
 for the Triassic, Jurassic, and Cretaceous periods, 1 : 1 j : 1. 
 That is, Mesozoic time was about one fourth as long as the 
 Paleozoic; and the three periods of the Mesozoic were not 
 far from equal, the Jurassic being one quarter the longest. 
 
 2. America!) Geography. On page 285 it is remarked that 
 the Mesozoic formations were confined to the Atlantic and 
 Gulf-border regions, and to an interior region west of the 
 Mississippi covering much of the Ptocky Mountain area, and 
 that the intervening portion of the continent had probably 
 become part of the dry land. The facts which have been 
 presented in the preceding pages have sustained this state- 
 ment. The Triassico-Jurassic beds, as has been shown, lie in 
 long narrow strips between the Appalachians and the coast, 
 and spread widely over the Rocky Mountain region and west 
 nearly to the Pacific. The Cretaceous beds cover the Atlantic 
 and Gulf borders, and also, like the Triassic, a very large part 
 of the slopes of the Rocky Mountains and the Pacific border 
 west of the Sierra Nevada. The eastern half of the continent 
 during the Mesozoic was, therefore, receiving rock-formations 
 only along its borders, while the western half had marine 
 deposits in progress over its great interior and on the ocean's 
 border. 
 
 The American Mesozoic deposits, for the most part, do not 
 bear evidence that they were formed in a deep ocean. They 
 appear to have accumulated m.unly along coasts, or in shallow 
 
REPTILIAN AGE. 325 
 
 waters off coasts, or in shallow inland seas ; the Cretaceous 
 limestone of Texas indicates a pure sea, like that required for 
 coral-reefs, but not necessarily one of great depth. 
 
 The Appalachians the eastern mountains of the continent 
 had nearly their present elevation before the early Meso- 
 zoic beds commenced to form (page 283). But the region of 
 the Rocky Mountains the western chain was to a great 
 extent still a shallow sea even during the Cretaceous period, 
 or when the Mesozoic era was drawing to its close (page 320). 
 
 Only one series of mountain-elevations can be pointed out, 
 with our present knowledge, as originating in Eastern North 
 America in the course of the Mesozoic era, although great 
 oscillations of level were much of the time in progress. This 
 one is that of the Mesozoic red sandstone and trap along the 
 Atlantic border region, as explained on page 307. 
 
 On the western side of the continent the mountain-making 
 after the Jurassic was on a far grander scale, the Sierra Ne- 
 vada and other high ranges dating from this epoch. 
 
 3. European Geography. Europe has its Mesozoic rocks 
 distributed in patches, or in several independent or nearly 
 independent areas, which show that it retained its condition 
 of an archipelago throughout Mesozoic time. The oscillations 
 of level, as indicated by the variations in the rocks, varia- 
 tions both as to the nature of the beds and their distribution, 
 - were more numerous and irregular than in North America, 
 The mountain-elevations formed, however, were few and small 
 compared with those that followed either the Paleozoic or 
 ' the Mesozoic era. One series of disturbances is referred to 
 the close of the Triassic, and another to that of the Jurassic. 
 
 Among the Mesozoic formations of the European continent 
 there are deposits of all kinds, those of sea-shores ; of off- 
 shore shallow waters ; of inland seas ; of moderately deep 
 oceanic waters ; and of marshy, or dry and forest-covered 
 knd. 
 
 Both in America and Europe there were some coal-beds 
 made, though of small extent compared with those of the 
 Carboniferous age. 
 
326 MESOZOIC TIME. 
 
 4. Life. The Mesozoic era witnessed (1) the decline of 
 some ancient or Paleozoic types of both plants and animals, 
 (2) the increase and culmination of mediaeval or Mesozoic 
 types, and (3) the beginning of some of the most important 
 of modern or Cenozoic types. 
 
 7. Disappearance of Ancient or Paleozoic features. Among the 
 ancient tribes of plants, the Calamities, or Tree-rushes, and 
 several genera of Ferns, disappear injbhe Jurassic. Among 
 the old Brachiopod tribes, the Spirifer and Leptcena families 
 end in the Triassic ; among higher Mollusks, the Silurian type 
 of Ortkoceras, and Devonian of Goniatites, have their last 
 species in the Triassic ; in Fishes, the Ganoids lose the verte- 
 brated feature of their tails, characterizing them in the Paleo- 
 zoic, in the same period, and thus bear evidence of progress. 
 
 2. Progress in Mesosoic features. The Cycads, among plants, 
 were those most characteristic of the Mesozoic : they after- 
 ward yielded to other kinds, and now are nearly an extinct 
 tribe. The Cephalopods, among Mollusks, existed in vast 
 numbers, both those with external shells, as the Ammonites, 
 and those without, as the Belcmnites. The whole number of 
 species of Cephalopods now known from the Mesozoic forma- 
 tions is nearly 1,200. Of these, about 950 were of the Nau- 
 tilus and Ammonite families. No Ammonite now exists, and 
 the only chambered species which are now living are 2 or 3 of 
 the genus Nautilus. The whole number of species of Cephal- 
 opods living in the course of the Mesozoic era may have been 
 three or four times 1,200, since only a part would have been 
 preserved as fossils. The sub-kingdom of Mollusks, therefore, 
 culminated in the Mesozoic era ; for its highest order, that of 
 the Cephalopods, was then ;it its maximum. 
 
 The type of Eeptiles was another that expanded and reached 
 its height, that is, its maximum in number, variety, and 
 rank of species, and commenced its decline in the 'Mesozoic 
 era. 
 
 There were huge swimming Saurians, Enaliosaurs, in the 
 place of whales in the sea ; bat-like Saurians or Pterodactyls 
 
REPTILIAN AGE, 327 
 
 flying through the air ; four-footed Saurians, both grazing and 
 carnivorous, many of them 25 to 50 feet long, occupying the 
 marshes and estuaries; great biped Saurians or Dinosaurs 
 over the land ; and snake-like Mosasaurs in the ocean, some 
 having the great length of 75 or 80 feet. 
 
 In the era of the Wealden and Lower Cretaceous there lived, 
 in and about Great Britain, 4 or 5 species of Dinosaurs 20 to 
 50 feet long, 10 to 12 Crocodilians, Lizards, and Enaliosaurs 
 10 to 50 feet long, besides Pterodactyls and Turtles; and 
 many more than this, since all that lived would not have left 
 their remains in the deposits. To appreciate this peculiarity 
 of mediaeval time, it should be considered that in the present 
 age Britain has no large Eeptiles ; in Asia there are only two 
 species over 15 feet in length; in Africa but one; in all 
 America but three ; in the whole world not more than six ; 
 and the largest of the six does not exceed 25 feet in length. 
 North America, during the Cretaceous, appears to have ex- 
 ceeded all the world beside in the number and size of its Eep- 
 tiles. The Mesozoic era is well named the Age of Eeptiles. 
 
 All the Mesozoic animals, excepting the Mammals, belong 
 to the oviparous divisions ; and the Mammals were mainly 
 Marsupial species, that is, semi-oviparous Mammals, as ex- 
 plained on page 176, species quite in harmony, therefore, 
 with the other life of the era. The Birds of the age, or at 
 least some of them, partook of the Eeptilian features of the 
 time, having long tails like the associated Eeptiles (though 
 feathered tails), with other peculiarities of the scaly tribes ; 
 and some even had reptile-like teeth. The long-tailed birds 
 and Pterodactyls were the flying creatures of the age ; the 
 Ichthyosaurs and Plesiosaurs, and the like, the " great whales " ; 
 the Teleosaurs, Iguanodon, and other gigantic species of the 
 estuaries and marshes, the creeping species. These, along 
 with the small Marsupials of the Cycadean and Coniferous 
 forests, were the more prominent kinds of Mesozoic life. 
 
 3. Introduction of Cenozoic features. Among plants the 
 first of Angiosperms (or the order including all trees having 
 
328 MESOZOIC TIME. 
 
 a bark excepting the Conifers, as the Oak, Maple, Apple, etc.), 
 and the first of Palms are found in the Cretaceous. These 
 become the characteristic plants of Cenozoic time. 
 
 Among Vertebrates there was a great expansion, if not the 
 first, of the great order of Teliost or Osseous Fishes, the species 
 characteristic of earlier time having been either Selachians 
 (Shark tribe), Ganoids, or Placoderms (page 237). The first 
 of the modern genus of Crocodilus occurs in the Jurassic ; the 
 first of Birds in the Triassic or Jurassic, the Reptilian 
 Birds ; the first of Mammals in the Triassic, Marsupials, or 
 semi-oviparous Mammals. 
 
 Of the classes of Vertebrates^Fishes and Reptiles commence 
 in the middle and later Paleozoic, and Birds and Mammals 
 in the early or middle Mesozoic. 
 
 Extermination of life at the close of the Cretaceous. At the 
 . close of the last period of the Mesozoic era the Cretaceous 
 there was an extermination of species over a large part of 
 the Continental seas as complete as that closing the Paleozoic 
 era. In Europe, Asia, and Eastern North America no Cre- 
 taceous species have been found fossil in any Tertiary strata. 
 In the Rocky Mountain region and the Pacific border it is 
 probable that some Cretaceous species continued on into the 
 Tertiary, as stated beyond (page 337). There is no reason for 
 asserting that the species of the open ocean were exterminated ; 
 on the contrary, it is believed that at least one Cretaceous 
 Mollusk" a Terebratula still exists in the depths of the 
 Atlantic. 
 
 Besides the destruction of species, there was the final ex- 
 tinction of several families and tribes. The great family of 
 Ammonites, and many others of Mollusks, all the genera of 
 Reptiles excepting Crocodilus, and others in all departments 
 of life, came to their end at the close of the Cretaceous or 
 soon after. 
 
 Extermination over so wide a range of Continental seas 
 must have been due to a cause which acted as widely, and 
 no other appears to be sufficient excepting a change of climate 
 
CENOZOIC TIME. 329 
 
 in the north. The Arctic and other high-latitude regions 
 may have been elevated more than those of lower latitudes, 
 for Tertiary rocks do not occur on the eastern borders of the 
 American continent north of the parallel of 42 1ST. to show 
 that the continent was then below its present level. Con- 
 nected with the elevation of the land to the north there may 
 have been an exclusion of warm oceanic currents from the 
 Arctic seas ; for in Behring Straits the depth of water is less 
 than 200 feet. By these means a semi-glacial epoch may have 
 been occasioned which sent cold oceanic currents from the 
 north along the sea-borders and Continental seas to the south. 
 Should the cold winds and cold oceanic currents of the north- 
 ern part of the existing temperate zone penetrate for a single 
 year into the tropical regions, they would produce a general 
 extermination of the plants and animals of the land, and also 
 of those of the coast and sea-borders, as far as the cold oceanic 
 currents extended. A change to a climate no colder than the 
 present would have been sufficient probably for all the de- 
 struction that took place, since the life of the Cretaceous seas, 
 even in Northern Europe, was largely that of the warm-tem- 
 perate zone. 
 
 While the emergence of northern lands here appealed to 
 may have taken place as the Cretaceous period closed, there 
 appears to have been no mountain-making of much extent 
 until the Tertiary age had already far advanced (page 346). 
 
 IV. -CENOZOIC TIME. 
 
 1. CENOZOIC TIME covers two ages : 1. THE TERTIARY AGE, 
 or AGE OF MAMMALS ; and 2. THE QUATERNARY, or AGE OF 
 MAN. 
 
 2. General characteristics. In the transition to this era the 
 life of the world takes on a Dew aspect. Trees of modern 
 types Oak, Maple, Beech, etc., and Palms unite with 
 
330 CENOZOIC TIME. 
 
 Conifers to make the forests; Mammals of great variety and 
 size, Herbivores, Carnivores, and others, successors to the 
 small semi-oviparous Mammals, tenant the land in place of 
 Reptiles ; Birds and Bats possess the air in place of reptilian 
 Birds and Pterodactyls ; Whales and Teliost or common 
 Fishes, with Sharks, mainly of modern type, occupy the 
 waters in place of Enaliosaurs, and almost to the exclusion 
 of the ancient tribes of Cestraciont Sharks and Ganoids. 
 Finally Man appears when Mammals were passing their 
 maximum in grade and magnitude, and becomes the domi- 
 nant species of the finished world. 
 
 'I. TERTIARY AGE, or AGE OP MAMMALS. 
 
 The Mammals of this age are all extinct species, and the 
 other species of life largely so ; the number of living species 
 of Invertebrates (Radiates, Mollusks, and Articulates) varies 
 from perhaps one per cent in the early part of the age to 
 90 in the latter. In the Quaternary the Mammals of the 
 earlier part are nearly all of extinct species ; the Invertebrates 
 are almost wholly of living species. 
 I . Periods. 
 
 The Tertiary strata have been divided by Lyell into three 
 groups : 
 
 1. Eocene (from the Greek ydx;, dawn, and KCLLVQS, recent) : 
 species nearly all extinct. 
 
 2. Miocene (from nelcov, less, and /catuo?) : less than half 
 the species living. 
 
 3. Pliocene (from TrXetW, more, and /caivos) : more than 
 half the species living. 
 
 These subdivisions are not necessarily those marked off 
 by the grander physical changes of a continent. 
 
 In North America there was : 
 
 1, The Lignitic period, corresponding to the Lower Eocene, 
 or else intermediate between the Tertiary and Cretaceous. 
 
TERTIARY AGE. 331 
 
 The beds follow on conformably after the Cretaceous; and 
 then, as the period closed, these Lignitic strata, along with 
 the underlying Cretaceous, which were also largely lignitic, 
 were together upturned, lifted into mountains, and partly ren- 
 dered metamorphic ; and this happened both in the Eocky 
 Mountain region and in California. This mountain-making 
 epoch makes a natural ending of the period. 
 
 2. The Alabama period, corresponding to the remainder 
 of the Eocene. The beds in the Rocky Mountain region 
 overlie nearly or quite horizontally the upturned Lignitic 
 and Cretaceous beds. On the Gulf of Mexico they include 
 the marine beds of Claiborne, Alabama, and of Jackson and 
 Vicksburg, Mississippi. The close of the period was marked 
 off by a change over the lower part of the Mississippi Valley 
 about the Gulf; for no marine Tertiary strata later than 
 Eocene exist in those regions. The country in the line of 
 Florida to the northwest, now 300 to 700 feet above the sea- 
 level, is the western boundary of the area of the later Ter- 
 tiary. 
 
 3. Yorktown, or that of the beds of Yorktown, Virginia, in 
 which 20 to 40 per cent of the species are living, usually 
 called Miocene, but possibly including part, at least, of the 
 Pliocene. 
 
 A fourth has been separated as Pliocene, or the Sumter 
 epoch, based on observations on the beds in Sumter and Dar- 
 lington districts, South Carolina ; but according to Conrad, it 
 may not be distinct from the Yorktown. 
 
 2. Rocks: Kinds and Distribution. 
 
 The beds are either of marine or of fresh-water origin. 
 
 The marine Tertiary beds of North America border the 
 continent south of New England along both the Atlantic 
 Ocean and the Mexican Gulf, overlying the Cretaceous in 
 part. The most northern locality is on Martha's Vineyard. 
 (See map, page 195, in which the area is lined obliquely from 
 the left above to the right below.) They spread northward 
 
332 CENOZOIC TIME. 
 
 to the mouth of the Ohio, and also westward into Texas, west 
 of the Mexican Gulf. 
 
 The marine Tertiary beds do not, like the Cretaceous, 
 stretch north and northwest up the eastern slopes of the 
 Kocky Mountains ; but, instead, there are over these slopes 
 extensive fresh-water Tertiary strata (formed in and about 
 great lakes), with in many places some of the lowest beds of 
 brackish-water origin, as shown by the fossils. This fresh- 
 water Tertiary extends over the summit region of the Kocky 
 Mountains ; and there the lower part includes not only 
 brackish-water, but also salt-water, beds, along with those 
 of fresh-water formation. Marine Tertiary occurs also in 
 California and Oregon, not far from the coast. 
 
 The Lignitic period, or early Eocene, includes brackish- 
 water, and associated fresh-water, strata in the Upper Mis- 
 souri and Eocky Mountain regions. They are remarkable for 
 containing extensive beds of good mineral coal, called brown 
 coal or lignite, whence the name of the period. These coal- 
 beds are worked at Evanston, Coalville, and other places on 
 or near the Central Pacific Eailroad. In Colorado and New 
 Mexico the Lignitic Tertiary passes downward, according to 
 the statements of some observers, into lignitic strata that 
 belong to the Upper Cretaceous. 
 
 Lignitic beds underlying the marine Tertiary of the Missis- 
 sippi Valley south of the Ohio are also of this era. 
 
 The Alabama period, or the Middle and Later Eocene, 
 comprises the marine Tertiary of the Gulf border from Mis- 
 sissippi eastward, and the lower beds of the Tertiary forma- 
 tion along the Atlantic border. 
 
 To the Yorktown period, or Miocene, belong the marine Ter- 
 tiary beds of the Atlantic border from New Jersey to South 
 Carolina, overlying the Eocene ; and fresh-water strata of great 
 extent in the Upper Missouri region and elsewhere over the 
 eastern slopes of the Eocky Mountains. 
 
 The Pliocene Tertiary, besides including possibly marine 
 beds in South Carolina, as mentioned above, comprises fresh- 
 
TERTIARY AGE. 333 
 
 water beds in the Upper Missouri region, and to the south, 
 where they overlie the Miocene fresh-water strata, and, like 
 them, are of lacustrine origin. 
 
 The Tertiary rocks are generally but little consolidated ; 
 they consist mostly of compacted sand, pebbles, clay, earth 
 that was once the mud of the sea-bottom or of estuaries, 
 mixed often with shells, or are such kinds of deposits as now 
 form along sea-shores and in shallow bays and estuaries, or 
 in shallow waters off' a coast. There are also limestones 
 made of shells, and others of corals, resembling the reef- 
 rock of coral seas. The latter are found mainly in the States 
 bordering on the Mexican Gulf. Another variety of rock is 
 buhrstone, a cellular siliceous rock, flinty in texture, used, on 
 account of its being so hard and at the same time full of 
 irregular cavities, for making millstones. It is found iu 
 South Carolina and Alabama. 
 
 The Tertiary of Great Britain occurs mostly in the south' 
 eastern part of England, in the London basin as it is called, 
 and on the southern and eastern borders of the island, adjoin- 
 ing the Cretaceous. 
 
 On the continent of Europe the Paris basin is noted for its 
 Eocene strata and fossil Mammals. Other Tertiary areas are 
 those of the Pyrenean and Mediterranean regions, those of 
 Switzerland, of Austria, etc. Some of the marine Fig <Li4. 
 Eocene beds contain Ehizopods (p. 185) having 
 the shape of a coin, called Nummulite (from 
 the Latin nummus, a coin). One is here figured, 
 of natural size ; it has the exterior of half oT 
 it removed to show the cells within. Occasion- 
 ally the beds are so far made up of these Nummulites that 
 the rock is called Nummulitic limestone. 
 
 These marine Eocene strata spread very widely over Lu- 
 rope, Northern Africa, and Asia, occurring in the Pyre- 
 nees, forming some of their summits ; in the Alps to a height 
 of 10,000 feet ; in the Carpathians, in Algeria, in Egypt, Avhere 
 the most noted pyramids aro made of Nummulitic limestone, 
 
334 CENOZOIC TIME. 
 
 in Persia, in the Western Himalayas (the region of Cash- 
 mere), to a height of 16,500 feet. The later Tertiary forma- 
 tions are much more limited in distribution, and many are of 
 terrestrial or fresh-water origin. 
 
 The rocks are similar to those of North America, but in- 
 clude more of hard sandstone and limestone. The sandstone 
 is a very common building-stone in different parts of Europe, 
 being soft enough to be worked with facility, yet generally 
 hardening on exposure, owing to the fact that it contains cal- 
 careous particles (triturated shells), which render the perco- 
 lating waters or rain calcareous, so that on evaporating they 
 produce a calcareous deposit, as a cement, among the grains 
 of sand. 
 
 The Eocene formation of Southeastern England consists of 
 beds of clay and sand, the lowest of sand sometimes contain- 
 ing rolled flints. The Lower Eocene includes the Thanet 
 sands, Woolwich beds, and London clay ; the Middle Eocene, 
 the lower Bagshot beds ; the Upper Eocene, the Barton clay, 
 Bembridge beds, and the Hernpstead beds near Yarmouth. 
 The Older Pliocene includes the Coralline crag and Eed crag 
 of Suffolk ; and the Newer Pliocene, the Norwich crag, which 
 is of fluvio-marine origin. No marine Miocene beds have 
 yet been identified in Great Britain. 
 
 I. Life. 
 1. Plants. 
 
 \ The great feature of the Tertiary vegetation is the preva- 
 lence of Angiosperms, the tribe of plants which, thus far, is 
 unknown before the Cretaceous. Leave? of Oak, Poplar, Maple, 
 Hickory, Dogwood, Mulberry, Magnolia, Cinnamon, Fig, Syca- 
 more, Willow, and many others, have already been found in 
 both American and European Tertiary strata, besides the re- 
 mains of Palms and Conifers. A leaf of a Tertiary Fan-palm 
 (species of Salal), found in the Upper Missouri, must have 
 been, when entire, 12 feet in breadth. Nuts are also common 
 in some beds, as at Brandon, Vermont. Fig. 415 is the 
 
TERTIARY AGE. 
 
 335 
 
 leaf of an Oak ; Fig. 416, of a species of Cinnamon ; Fig. 417, 
 of a Palm ; Fig. 418, the nut of a beech, closely like that of 
 
 Figs. 415-419. 
 
 f'ig. 415, Quercus myrtifolia?; 416, Cinnainomum Mississippiense ; 417, Calamopsis Danae ; 
 418,Fagus ferruginea?; 419, Carpolithes irregnlaris. 
 
 the common beech ; Fig. 419, another nut, from Brandon, of 
 unknown relations. Figs . 420-425. 
 
 The Eocene Plants of Great 420 
 Britain included Palms, and 
 among those of Central and South- 
 era Europe there were many spe- 
 cies related to the trees of Austra- 
 lia; while the Miocene and Plio- 
 cene had much similarity to those 
 of America. 
 
 The microscopic plants which 
 form siliceous shells, called Diatoms (Figs. 420 to 425, all 
 
 Diatoms. 
 
336 
 
 CENOZOIC TIME. 
 
 greatly enlarged), make extensive deposits in some places. 
 One stratum near Richmond, Virginia, is 30 feet thick, and 
 is many miles in extent ; another, near Monterey, California, is 
 50 feet thick, and the material is as white and fine as chalk, 
 which it resembles; another, near Bilin in Bohemia, is 14 
 feet thick. The material from the latter place was used as a 
 polishing-powder (and called Tripoli, or polishing-slate) long 
 before it was known that its fine grit was owing to the re- 
 mains of microscopic life. Ehrenberg has calculated that a 
 cubic inch of the fine earthy slate contains about forty-one 
 thousand millions of organisms. Such accumulations of Dia- 
 toms are made both in fresh waters and salt, and those of the 
 ocean at all depths. 
 
 2. Animals. 
 
 The most prominent fact with regard to the Tertiary In- 
 vertebrates is their general resemblance to modern species. 
 Although a number of the genera are extinct, and nearly 
 every Eocene species, there is still a modern look in the re- 
 Figs. 426-430. 
 
 LAMELLIBRANCHS : Fig. 426, Ostrea sellseformis ; 427, Crassatella alta ; 428, Astarte 
 Conradi ; 429, Cardita planicosta. GASTEROPOD : 430, Turritella carinata. 
 
 mains, and the specimens have often the freshness of a shell 
 from a modern beach. 
 
TERTIARY AGE. 
 
 337 
 
 The preceding are figures of a few Mollusks of the marine 
 Eocene, from Claiborne, Alabama. Fig. 426 represents an 
 Eocene Oxtrea ; Fig. 427, a species of Crassatella ; Fig. 428, an 
 Astarte; Fig. 429, a Cardita ; and Fig. 430, a Turritella. 
 
 Figs. 431 to 434 are species of Miocene shells, from 
 Virginia ; Figs. 431, 432, represent a very common Crepidula. 
 
 Figs. 431-434. 
 433 
 
 GASTEROPOD : Figs. 431, 432, Crepidula costata. LAMELLIBRANCHS : Fig. 433, 
 Yoldia liniatula ; 434, Callista Sayana. 
 
 upper and under sides. The species of the epoch include the 
 common Oyster and Clam, and other modern species; and 
 these are, therefore, among the most ancient of living species 
 on the globe. The Lignitic beds of the Ilocky Mountain 
 region in Wyoming Territory and elsewhere contain a very 
 few Cretaceous species, among them the Inoceramus proble- 
 maticus. 
 
 "With regard to Vertebrates the points of special interest 
 are the following : 
 
 1. In the class of Fishes : (1) The prevalence of Tdiosts, 
 or fishes allied to the Perch and Salmon, as already stated ; 
 and (2) the abundance of Sharks, some of them having teeth 
 6 inches long and broad. The teeth of sharks are the durable 
 part of the skeleton ; they are very abundant in both Eocene 
 and Miocene beds. Fig. 436 represents a tooth of the Car- 
 charodon angustidens. The larger teeth above alluded to belong 
 to the Oarcharodon megalodon, and are found at different places 
 on the Atlantic border from Martha's Vineyard southward. 
 
 22 
 
338 
 
 CENOZOIC TIME. 
 
 Figs. 435, 436 
 
 Fig. 435 represents the tooth of another common kind t>f 
 Shark, a species of Lamna, from Claiborne. 
 
 In the class of Reptiles : The existence of numerous Croco- 
 diles and Turtles. The shell of one of the Miocene turtles, 
 
 found fossil in India, had a length of 
 12 feet, and the animal is supposed 
 to have been 20 feet long. The first 
 of true Snakes, moreover, occur in 
 the Eocene. 
 
 Dinosaurian remains, unknown in 
 Europe above the Cretaceous, occur 
 sparingly in the Lignitic beds of the 
 Rocky Mountain region, and have 
 strengthened the doubt whether these 
 beds are not part of the Upper Cre- 
 taceous. 
 
 In the class of Birds : The species 
 found are not long-tailed, or in any 
 respect reptilian, but resemble mod- 
 ern birds ; they are related to the 
 Pelican, Waders, Pheasants, Perclicrs, 
 TEETH OF SHARKS. - K , 486, twre,, Owls, Woodpeckers, and 
 
 Carcharodon angustidens ; 435, Other Kinds. 
 Lamna elegans. T f -i 
 
 The 
 
 occurrence of the first of Whales, the first of Carnivores, Her- 
 bivores, Rodents, Monkeys, and of other tribes, indicating a 
 large population of brute animals, different from the present 
 in species, though, in general, related to the modern kinds 
 in form and structure. A few, however, are widely diverse 
 from anything in existence, such combinations as the mind 
 would never have imagined without aid from the skeletons 
 furnished by the strata. 
 
 In the early Eocene there appear to have been more Her- 
 bivores than Carnivores ; but afterward the Carnivores were 
 as common as now. 
 
 Cuvier first made known to science the existence of fossil 
 
TERTIARY AGE. 
 
 339 
 
 Tertiary Mammals. The remains from the earthy beds about 
 Paris had 'been long known, and were thought to be those of 
 modern beasts. But, through careful study and comparisons 
 with living animals, he was enabled to bring the scattered 
 bones together into skeletons, ascertain the tribe to which 
 they belonged, and determine the food and mode of life of the 
 ancient but now extinct species. Cuvier acquired his skill 
 by observing the mutual dependence which subsists between 
 all parts of a skeleton, and, in fact, all parts of an animal. A 
 sharp claw is evidence that the animal has trenchant or cut- 
 ting molar teeth, and is a flesh-eater ; a hoof, that he has broad 
 molars and is a grazing species ; and, further, every bone has 
 some modification showing the group of species to w r hich it 
 belongs, and may thus be an indication, in the hands of one 
 well versed in the subject, of the special type of the animal, 
 and of its structure, even to its stomach within and its hide 
 without. 
 
 One of these Paris beasts from the middle Eocene beds is 
 called a Palcotherc, from the Greek vraXato?, ancient, and 
 v, wild beast. It is related to the modern Tapirs (Fig. 
 
 Fig. 437- 
 
 Tapirus Indicus. 
 
 437), and was of the size of a horse. Another kind, called a 
 Xiphodon, was of more slender habit, and somewhat resembled 
 
340 CENOZOIC TIME. 
 
 a stag, as shown in Fig. 438. There were others, related to the 
 hog, or Mexican Peccary ; also some Carnivores, a Bat, and an 
 Opossum. 
 
 Among American Eocene Mammals there is a species of 
 whale of great length, called a Zeuglodon, from %6vy\Tj, yoke, 
 and o5ou9, tooth, in allusion to the fact that part of the teeth 
 have two long prongs which give them a yoke-like shape. 
 
 Fig 438 
 
 Xiphodon gracile. 
 
 The bones occur in many places in the Gulf States, and in 
 Alabama the vertebrae were formerly so abundant as to have 
 been built up into stone walls, or burned to rid the fields of 
 them. The living animal was probably 70 feet in length. 
 One of the larger vertebrae measures a foot and a half in length 
 and a foot in diameter. 
 
 The Lignitic beds, or early Eocene of North America, have 
 afforded no Mammalian remains. But, from the overlying 
 Middle or Later Eocene, of the Green Eiver basin, near Fort 
 Bridger, a large number of species have been obtained. The 
 skull of one kind, of elephantine size, having six horn-cores, 
 and called by Marsh Dinoceras, in allusion to its horns, is rep- 
 resented in Fig. 341. It was somewhat related to the Ehino- 
 ceros. There were also the earliest of the Horse tribe, called 
 Orohippus ; and it is remarkable that these Eocene Horses 
 had four usable toes (Fig. 440) instead of the one only of the 
 
TERTIARY AGE. 
 
 341 
 
 modern Horse. The relations in the foot of the latter to dif- 
 ferent kinds of Tertiary Horses are illustrated in Figs. 440 - 443. 
 
 Fig. 439. 
 
 Dinoceras mirabile ( x |). 
 
 In Fig. 443 it is shown that the modern Horse has one 
 usable toe, the third, and rudiments of two others, the second 
 
 Figs. 440-443 
 441 
 
 443 
 
 \ 
 
 EZ 
 
 FEET OF SPECIES OF THE HORSE TRIBE. -Fig. 440, Orohippus, of "the Eocene 
 (x |-); 441, Anchitherium, of the Miocene; 442, Hipparion. of the Pliocene ; 443, the 
 modern Horse. 
 
342 
 
 CENOZOIC TIME. 
 
 and fourth, in what are called the splint-bones. In the Hip- 
 parion, of the Pliocene (Fig. 442), the second and fourth have 
 hoofs, but they are not usable. In Anchitherium, of the Mio- 
 cene (Fig. 441), the second and fourth toes come to the ground, 
 and are therefore usable. In Orohippus (Fig. 440), not larger 
 than a small-sized dog, there are four toes, and all are usable. 
 
 Other "Wyoming species are related to the Tapir and Hog, 
 some approaching in characters the Paris Paleotliere. There 
 were also Monkeys, some Carnivores related to the Cat and 
 Wolf, Bats, Squirrels, Moles, and Marsupials. 
 
 The Miocene beds of the " Bad Lands " on the White Kiver, 
 in the Upper Missouri region and elsewhere in the West, have 
 afforded remains of other Mammals. 
 
 Among them are several 
 
 Fig. 444. 
 
 Tooth of Titanotherium Proutii (X 4)- 
 
 Carnivores related somewhat to the Hyena, Dog, and Panther ; 
 many Herbivores, including Rhinoceroses, species approaching 
 the Tapir, Peccary, Deer, Camel, Horse; Kodents. Fig. 444 
 
 Fig. 445. 
 
 Teeth of Rhinoceros (Hyracodon) Nebrascensis. 
 
 represents a tooth, half the natural size, of a Titanothere, an 
 animal related to the Tapir and Paleothere, but of elephan- 
 tine size, standing probably 7 or 3 feet high. Fig. 445 repre- 
 
TERTIARY AGE. 
 
 343 
 
 sents a few of the teeth of an animal related to the Khinoceroses. 
 Another species, the Brontotherium, nearly as large as an 
 Elephant, but related somewhat to the Rhinoceros, had a pair 
 of great horns. 
 
 Fig 440. 
 
 Oreodun gracilis. 
 
 Fig. 446 represents the skull of another Miocene Mammal, 
 called an Oreodon, which is intermediate between the Deer, 
 
 Camel, and Hog. Remains of 
 
 Fig 447. 
 
 Camel and Rhinoceros, and some of 
 the tapir-like beasts, have been 
 found in the Miocene of the Atlan- 
 tic border. 
 
 In the Pliocene beds of the 
 Upper Missouri region still other 
 species occur; including Camels, a 
 Rhinoceros, an Elephant, a Masto- 
 don, Horses, Deers, a Wolf, a Fox, 
 a Tiger, a range of species quite 
 Oriental in character. 
 
 Among Mammals of the Euro- 
 pean Miocene there were Elephants, Mastodons, Deer, and 
 
 Dinotherium giganteum (x 4TT). 
 
344 
 
 CENOZOIC TIME. 
 
 other Herbivores, many Carnivores, Monkeys, Ant-eaters, etc. 
 One of the most singular species is the Dinothere, the form 
 of the skull of which is shown in Fig. 447 ; its actual length 
 is 3 feet 8 inches. It appears to have had a proboscis like 
 an Elephant, but the tusks proceeded from the lower instead 
 of upper jaw, and were bent downward. 
 
 The earliest of the Bovine or Ox group occur in the Euro- 
 pean Pliocene. 
 
 4. General Observations. 
 
 1. Geography. The Tertiary period completed mainly the 
 work of rock-making along the borders of the continent, which 
 
 Figs 448 
 
 Map of North America in the early part of the Tertiary Period. 
 
 had been in progress during the Cretaceous period. The ac- 
 companying map shows approximately the part of the conti- 
 nent of North America under the sea toward the middle of 
 
TERTIARY AGE. 345 
 
 the Eocene Tertiary, or when the Lignitic period was near its 
 close. By comparing it with the map of the Cretaceous con- 
 tinent, page 322, it is seen that in the interval the Kocky 
 Mountain region had become dry land. The occurrence of 
 brackish- water beds in the Lignitic Tertiary of the Upper 
 Missouri region, and of salt-water beds, as well as brackish- 
 water, in the Lignitic of the summit of the mountains, indicate, 
 as shown by Hayden, that the passage from the marine condi- 
 tion of the Cretaceous era gradually changed into that of the 
 fresh-water lakes and dry land of the later Eocene. The 
 gradualuess of the transition is further shown in the occur- 
 rence of Lignitic or coal-bearing beds in the Upper Creta- 
 ceous. After the Eocene, the elevation went forward, but 
 still with extreme slowness, for in the Miocene the eastern 
 slopes of the mountains were covered with immense fresh- 
 water lakes, whose borders were the haunts of the Mammals 
 of the era ; and these lakes were continued, though of dimin- 
 ished size, into the Pliocene. The Cretaceous beds are now 
 10,000 feet above the sea-level, showing that this amount of 
 elevation has taken place since that era ; but this height may 
 not have been fully attained before the closing part of the 
 Pliocene period. The area of the Mississippi river-system, 
 embracing the slopes of the Eocky Mountains on the west 
 and those of the Appalachians on the east, then for the first 
 time attained its full dimensions. The Mexican Gulf was 
 much larger in the Eocene period than at present ; but there 
 was not that long extension northward which it had during 
 the Cretaceous period. Florida was still submerged, and also 
 all the bays of the Atlantic coast south of New York. After 
 the Eocene epoch the Mexican Gulf became much more con- 
 tracted by an elevation of the coast along the Gulf, accom- 
 panying which the part of Georgia northwest of Florida, 
 where Eocene and Cretaceous beds had been formed in the 
 sea, was raised 300 to 700 feet above the sea-level. By the 
 close of the Tertiary period the continent appears to have 
 reached nearly its present outline. 
 
346 CENOZOIC TIME. 
 
 Besides the gradual changes, there was in the Eocky Moun- 
 tain region, and also in California, the making of mountain 
 ranges. At the close of the Lignitic period there were up- 
 turnings of the Lignitic and underlying formations ; and the 
 Wahsatch, with other high ranges in Colorado and the adjoin- 
 ing regions, are part of the results. Probably at the same 
 time the Cretaceous strata of California, west of the Sierra 
 Nevada, were made into mountains that are now part of 
 the coast ranges. This then was one of the great mountain- 
 making epochs iii American Geological history. 
 
 In the Orient the Eocene era was one of very extensive 
 submergence of the land, as shown by the distribution of the 
 nummulitic beds over Europe, Asia, and Northern Africa, as 
 stated on page 333. Before the close of the Eocene, the 
 greater part of these Continental seas became dry land, and 
 in general continued so afterward ; for the marine Miocene and 
 Pliocene are, comparatively, of limited extent. Many of the 
 great mountains of the globe, as the Pyrenees, Alps, Carpa- 
 thians, Himalayas, etc., received then a large part of their 
 elevation, as is proved by their containing Eocene rocks in 
 their structure, or by their bearing them about their summits. 
 Thus it is learned that the elevation of the Pyrenees, though 
 commenced before the close of the Cretaceous, was mainly 
 produced in the middle or later part of the Eocene, as also 
 that of the Julian Alps, the Apennines and Carpathians, and 
 that of heights in Corsica. The Himalayas, in their western 
 part about Cashmere, have nummulitic or Eocene beds, at a 
 height of 16,500 feet ; so that even this great chain, although 
 earlier elevated to the east, was not completed before the 
 Middle Eocene ; and even later than this it received a consid- 
 erable part of its elevation, as later Tertiary beds at lower 
 levels show. The elevation of the Western Alps, including 
 Mont Blanc, is referred by Elie de Beaumont to the close or 
 latter part of the Miocene period; and that of the Eastern 
 Alps, along the Bernese Oberland, to the close of the Plio- 
 cene. An elevation of 3,000 feet took place in Sicily after 
 the Pliocene. 
 
QUATERNARY AGE. 347 
 
 Many parts of the region of the Andes were raised 3,000 
 to 5,000 feet or more in the course of the Tertiary period. 
 
 Climate. During the Eocene, Palms abounded in Britain, 
 evidence of a sub-tropical or warm-temperate climate in its 
 latitudes; and the Arctic regions had forests consisting of 
 Beech, Plantain, Willow, Oak, Poplar, Walnut, Magnolia, Red- 
 wood, showing a mean temperature of at least 48 F. (Heer.} 
 In the Miocene, Southern Europe had a sub-tropical climate, 
 but England had lost its palms and was cooler. 
 
 In North America, the Eocene palms and other plants of 
 the Upper Missouri region show that the temperature of 
 North Carolina characterized then the region of the Upper 
 Missouri, the vicinity of the Great Lakes, and also Vermont, 
 where exists the Brandon deposit of nuts and lignite. 
 
 The Camels, Rhinoceroces, and other animals of the Pliocene 
 of the Upper Missouri, seem to prove that a warm-temperate 
 climate prevailed there in that closing epoch of the Tertiary. 
 
 It is therefore plain that the Earth had not as great a diver- 
 sity of zones of climate as now ; and that Europe was little if 
 any colder in the Eocene than in the Jurassic era. If the 
 interval between the Cretaceous and Tertiary was one of un- 
 usual cold, through Arctic and other elevations, as suggested 
 on page 328, the cold epoch had mostly passed when the 
 Eocene era opened. 
 
 II. QUATERNARY AGE, or ERA OP MAN. 
 
 1. General characteristics, The Quaternary age was re- 
 markable (1) for high-latitude movements and operations both 
 north and south of the equator ; (2) for the culmination of the 
 type of brute Mammals ; and (3) for the appearance of Man on 
 the globe. 
 
 2. Periods. The periods are three : 
 
 1. The Glacial, or the period when, over the higher latitudes, 
 the continents underwent great modifications in the features 
 *? the surface through the agency of ice. 
 
348 CENOZOIC TIME. 
 
 2. The Champlain, when the ice disappeared, and the same 
 high-latitude portions of the continent, and to a less extent 
 the lower, were below their present level, and became covered 
 by extensive fluvial and lacustrine formations, and along sea- 
 coasts by marine formations. 
 
 3. The Receni or Terrace period, begun by a rising of the 
 land nearly or quite to its present level. 
 
 I . Glacial Period. 
 
 The following are some of the facts, characterizing the 
 Glacial period : 
 
 1. Transportation. The transportation of a vast amount 
 of earth and stones from the higher latitudes to the lower. 
 
 The transported material consists of earth, gravel, stones, 
 and bowlders, and includes, in America, nearly all the earth, 
 as well as stones, of the surface in the latitudes of New Eng- 
 land and farther north. It extends over hills and valleys, 
 and varies in depth from a few feet to hundreds. A large 
 part of the material is in an unstratifted condition, large 
 stones and small, pebbles and sand, being mingled pell-mell. 
 Part, especially that in the valleys or depressions of the sur- 
 face, is stratified, and thus bears evidence of deposition by 
 flowing waters, like fluvial and lacustrine formations. 
 
 The transported material is called Drift, and the unstratified 
 part of it till (from the Scotch). The till, especially its lower 
 part, is often a clayey eaith, or a clayey mixture of earth and 
 stones with frequent bowlders, called the bowlder-clay ; it is 
 in general firmly compacted because of the clay. In the 
 valleys the clay is often straticulate. 
 
 The drift-covered region of North America, or that over 
 which the great southward movement took place, extends 
 from the Atlantic border of New England and Labrador, west- 
 ward, for more than 1,200 miles, Dakota and Lake Winnipeg 
 being near the western border : but, farther north, it extends 
 across the continent ; and along the Eocky Mountains and 
 the Pacific border spreads southward again. 
 
GLACIAL PERIOD. 349 
 
 The southern limit of travel for the unstratified drift, or 
 till, is not fully made out. It is supposed to have had its 
 course from Cape Cod (though perhaps lying miles outside of 
 it) to Long Island arid Perth Amboy, N. J. ; through New 
 Jersey northward and westward to Oxford ; through Pennsyl- 
 vania to a point north of Pittsburg ; through Ohio, by Dan- 
 ville, to the Ohio east of Cincinnati ; thence for a few miles 
 in Kentucky ; thence northwestward and westward through 
 Middle Indiana and Illinois, and- the States west, and to have 
 included (Upham) the Coteau de Missouri in Dakota. The 
 stratified drift (which is mostly a deposit of the Champlain 
 period, as explained beyond) occurs much farther south along 
 the river-valleys, and reaches even to the State of Mississippi 
 in the Mississippi valley. 
 
 The travelled stones are of all dimensions, from that of a 
 small pebble to masses as large as a moderate-sized house. 
 One at Bradford in Massachusetts is 30 feet each way, and 
 its weight is estimated to be at least 4,500,000 pounds. 
 Many on Cape Cod are 20 feet in diameter. One lying on 
 a naked ledge at Whitingharn in Vermont measures 43 feet 
 in length and 30 in height and width, or 39,000 cubic feet in 
 bulk, and was probably transported across Deerfield Valley, 
 the bottom of which is 500 feet below the spot where it lies. 
 There are many great bowlders of trap from 50 to 1,250 tons 
 in weight along the western border of the Triassico-Jurassic 
 area in Connecticut, the line reaching to Long Island Sound, 
 just west of New Haven; and others of great magnitude 
 occur farther south on Long Island. 
 
 The directions of travel, as learned by tracing the stones in 
 numerous cases to the ledges whence they were derived, are, 
 in general, between southwestward and southeastward. The 
 distance to which the stones were transported in North Am- 
 erica, as learned by comparing them with the rocks in place 
 to the north, is mostly between 10 and 40 miles, though in 
 some cases over 200 miles. The material was carried south- 
 ward across the Great Lakes and across Long Island Sound 
 
350 
 
 CENOZOIC TIME. 
 
 the land to the south, in each case, being covered with stones 
 from the land to the north. 
 
 Besides this northern Drift, there are similar accumulations 
 of earth and stones belonging to the same era, distributed 
 locally about some of the Appalachian ridges, south of Drift 
 latitudes ; also on a grand scale about the higher ridges of the 
 summit of the Eocky Mountains, and in the Sierra Nevada 
 and other ranges and heights of the Pacific border region. 
 
 Fig. 449. 
 
 Drift groovings or scratches. 
 
 2. Scratches. The rocky ledges over which the drift was 
 borne are often scratched, in closely crowded parallel lines, as 
 in the preceding figure (Fig. 449), and planed off besides. The 
 scratchings or groovings are sometimes deep and broad chan- 
 nellings, and at times a yard or more deep and several feet 
 wide, as if made by a tool of great size as well as power. 
 The scratches occur wherever the drift occurs, provided the 
 underlying rocks are sufficiently durable to have preserved 
 them, and they are usually of great uniformity in any given 
 region. In some places two or more directions may be ob- 
 served on the same surface. They are found in the valleys 
 and on the slopes of mountains, to a height, on the Green 
 
GLACIAL PERIOD. 351 
 
 Mountains, of 4,400 feet, and on the White Mountains of 
 5,500 feet. They have nearly a common course over the 
 higher lands of a region, and even cross slopes and the 
 smaller valleys, without following the direction of the slope 
 or valley; hut they generally conform to the directions of 
 the great valleys of the land, aad often to the smaller when 
 they have much breadth. In the Hudson Elver Valley, be- 
 tween the Catskills and Green Mountains, the scratches have 
 mostly the course of the valley; and also in the Connecticut 
 River Valley, the Merrimack, and other valleys. 
 
 The stones, or bowlders, of the till are often scratched as 
 well as the rocks, and in this respect they differ from those 
 of stratified drift; the latter have lost all scratches by river 
 abrasion. 
 
 3. European Drift. The Drift in Europe presents the same 
 general course and peculiarities as in North America. It 
 reaches south in some places to about latitude 50. The 
 region south of the Baltic, and parts of Great Britain, are 
 covered with drift and stones from Scandinavia. The distance 
 of travel varies from 5 or 10 miles to 500 or 600. About the 
 Alps and other high mountains south of Drift latitudes there 
 are local accumulations of Drift of the Glacial area, and also 
 scratches over the surface rocks. 
 
 4. Fiords. Fiords are deep, narrow sea-channels running 
 many miles into the land. They occur on the coasts of Nor- 
 way, Britain ; of Maine, Nova Scotia, Labrador, Greenland ; 
 on the coast of Western North America north of the Straits of 
 De Fuca ; along that of Western South America south of 
 latitude 41 S. 
 
 Fiords are thus, like the Drift, confined to the higher lati- 
 tudes of the globe, the Drift-latitudes ; and the two may have 
 been of contemporaneous origin. 
 
 5. Origin of the Drift. Nothing but moving ice could have 
 transported the Drift with its immense bowlders. 
 
 Glacier Theory. The ice is performing this very work now 
 in the glacier regions of the Alps and other icy mountains, 
 
352 CENOZOIC TIME. 
 
 and stones of as great size have in former times been "borne 
 by a slow-moving glacier from the vicinity of Mont Blanc 
 across the lowlands of Switzerland to the slopes of the Jura 
 Moun tarns, and left there at a height of over 2,000 feet above 
 the level of Lake Geneva. Moreover, there are in many 
 places deposits of bowlder-clay, made of the earth formed by 
 trittiration of stones against stones during the moving of the 
 glacier. Further, there are scratches, of precisely the same 
 character as to numbers, depth, and parallelism, on the gran- 
 itic and limestone rocks of the ridges ; and besides, the trans- 
 ported material is left unstratified over the land, wherever it 
 is not acted upon and distributed by Alpine torrents. 
 
 Icebergs also transport earth and stones, as in the Arctic 
 seas ; and great numbers are annually floated south to the 
 Newfoundland banks, through the action of the northern or 
 Labrador current, where they melt and drop their great bowld- 
 ers and burden of gravel and earth to make deposits over the 
 sea-bottom. But icebergs could not have covered great sur- 
 faces so regularly with scratches, Again, there are no marine 
 relics in the unstratified drift to prove that the continent was 
 under the sea in the Glacial period. 
 
 There is* a seeming difficulty in the glacier theory, from the 
 supposed want of a sufficient slope in the surface to produce 
 movement. But a slope in the under surface is not needed, 
 any more than for the flowing of pitch. Pitch, deposited in 
 continued supply on any part of a plain, would spread in all 
 directions around; and this it would do if, instead of a plain, 
 the surface beneath had an ascending slope. The slope of the 
 upper surface of a plastic or fluid substance determines the 
 rate of flow, not that of the under surface. Hence, if ice were 
 accumulated over a region so that the upper surface had the 
 requisite slope, there would be motion in the mass in the 
 direction of this slope, whatever the bottom slope might be. 
 At the same time the slope of the land at bottom, or the courses 
 of the valleys, would determine to some extent the movement 
 at bottom ; just as oblique grooves in a sloping board, down 
 
GLACIAL PERIOD. 353 
 
 which pitch was moving, would determine more or less com- 
 pletely the direction of the movement in the grooves. 
 
 A semi-continental glacier. All the facts or phenomena con- 
 nected with the northern Drift are fully explained by refer- 
 ence to a great northern semi-continental glacier as the cause ; 
 and those relating to local Drift about high mountains, south 
 of Drift latitudes, by referring them to local glaciers. But 
 icebergs drifted down the coast, and probably crossed the 
 Hooded region of the Great Lakes. Ice-floes descended rivers, 
 dropping their stones by the way. On the Mississippi, the 
 floating ice may have reached the Gulf of Mexico and the 
 chilled waters have destroyed much tropical life. 
 
 The height to which scratches and drift occur about the 
 White Mountains proves that the upper surface of the ice in 
 that region was 6,000 or 6,500 feet ; and hence that the ice 
 was not less than 5,000 feet thick over that part of North- 
 ern New England. Facts also show that the surface height 
 in southwestern Massachusetts was at least 2,800 feet; in 
 southern Connecticut, 1,000 feet or more ; in the Catskills, 
 3,000 feet (Smock). 
 
 Since the slopes of the upper surface of a glacier deter- 
 mine the general direction of movement, and therefore of 
 transportation and abrasion, the lines of scratches or of drift 
 are an indication as to the position of the ice-summit. The 
 prevailing direction over the higher lands of New England 
 and eastern Canada is southeastward, and that over western 
 New York and Pennsylvania and the country north and 
 northwest to Winnipeg Lake, is southwcstward. The lines con- 
 sequently converge northward, toward the part of the Canada 
 water-shed west of north from Montreal and a region extend- 
 ing thence northeastward toward the Arctic regions ; and 
 hence along this course there must have been the summit of 
 a great ice range. Farther west, over the dry interior of the 
 continent (where the present amount of annual precipitation 
 is only 12 to 20 inches), the ice thinned out or was absent. 
 
 It is consequently evident that the ice of the Glacial era 
 
 23 
 
354 CENOZOIC TIME. 
 
 in America was not an ample " ice-cap " covering the north- 
 ern latitudes nearly half way to the equator, but that the ice 
 stretched southward from a polar area along the courses of 
 greatest atmospheric precipitation ; which courses were three 
 in number : one of great width and height on the Atlantic 
 side, the moist side of the continent ; a second, of compara- 
 tively narrow limits, on the Pacific side ; and a third, follow- 
 ing the higher ridges of the Rocky Mountains. 
 
 The stones and earth transported by the Continental glacier 
 were gathered up mostly by its lower part, from the surface 
 of hills or ridges that projected into it, and even from the 
 plains beneath it. In New England, where there were no 
 peaks rising above the upper surface to be a source of aval- 
 anches, as in the Alps, many of the masses thus taken aboard 
 exceed 1,000 tons in weight. 
 
 -Excavating action of the Glacier. With a thickness of 
 even 2,000 feet the glacier would have had great excavating 
 force, although the abrading power was not great. Soft 
 rocks would have been deeply ploughed up by it, and all 
 jointed and fissile rocks, soft or hard, would have been torn 
 to fragments, and the loosened masses borne off. By this 
 means, and most of all through the erosion of subglacial 
 streams, valleys were excavated and widened. 
 
 Drift in other Countries. The drift phenomena of Europe 
 lead to the same general conclusion : that amount of precipi- 
 tation determined to a large extent the distribution of the ice ; 
 temperature being the other chief condition. The southern 
 limit is, on an average, 10 higher in latitude in Europe than in 
 America, corresponding to the modern fact as to the climate 
 of the region. The great European ice-range followed the 
 course of the Scandinavian mountains, the moist mountain- 
 border of Western Europe. The Alps, although outside of 
 the area of northern drift, had glaciers over 2,000 feet above 
 their present limit ; and enormous bowlders from the Alps 
 (one of 3,000 tons) lie high on the Juras, to the west of the 
 plains of Switzerland. With such facts from the Alps, large 
 
GLACIAL PERIOD. 355 
 
 estimates as to the thickness of the ice in America lose their 
 apparent extravagance. In Asia the precipitation was too 
 small to make a glacier over the lower plains. 
 
 Greenland is at the present time a glaciated continent, 
 nearly as northern America was in the Glacial era. The ice 
 moves where the slope of surface is less than half a degree. 
 In the Glacial era, the Greenland ice stood, in some parts of 
 the Coast region, 3,000 feet above its present level ; which is a 
 small difference compared with the thickness of ice produeed 
 by the Glacial era in more southern and moister latitudes. 
 
 On the possible origin of a yladal climate, see page 125. 
 
 2. Champiain Period. 
 
 The Champiain period, as is proved by marine relics and by 
 other facts described beyond, was an era of depression in the 
 continents over the higher latitudes below the present level, and 
 a depression which, within certain limits, increased to the 
 northward. It was also a period, as indicated by the terres- 
 trial life, of warmer climate than the Glacial ; and, probably, 
 because of the lower level of the northern or high-latitude 
 lands. The warmer climate appears to have determined the 
 melting of the great glacier, and it caused this melting to go on 
 widely over its surface ; so that, when it had thinned down 
 the ice to within 500 or 1,000 feet, the disappearance of the 
 rest of the ice went forward with accelerated progress. 
 
 (1) The melting was thus the great event of the opening 
 part of the Champiain period ; and it must have caused im- 
 mense floods in all valleys, vastly beyond those from the 
 breaking up of an ordinary winter. 
 
 With the melting of the lower 1,000 feet, and during the 
 era of floods, there would have been (2) the deposition of the 
 earth, gravel, and stones contained therein ; and in the de- 
 position, wherever the material fell over the land, it would 
 have gone down pell-mell and been left (a] unstratified ; while, 
 whatever fell into flowing streams, lakes, tidal estuaries, or 
 along sea-coasts, would have been (V) stratified. The stratified 
 
356 CENOZOIC TIME. 
 
 deposits of the Champlain period are then either (1) of river- 
 valley origin, (2) lacustrine, or (3) estuary or marine. 
 
 After the era of floods or the Diluvial part of the Champlain 
 period, the depositions in what may be called the Alluvial 
 part of the period went on more quietly; and many land 
 shells, bones, and other relics are contained in the river- 
 valley deposits then made. 
 
 The Diluvial beds consist of earth, clay, sand or pebbles, 
 or of mixtures of these materials. And the Alluvial are partly 
 the same, but more commonly of finer earth and clay. 
 
 The river-border deposits occur in all or nearly all the 
 river- valleys within the drift latitudes of the North American 
 continent, from Maine to Oregon and California; and they 
 exist farther south, extending along the Mississippi Valley to 
 the Gulf of Mexico. The cold water descended the valley in 
 a vast flood to the Gulf, bearing on its surface much drift ice 
 from the dissolving glacier, the fact of the flood and that 
 of the floating ice being proved, as Hilgard has shown, by the 
 nature of the stratified deposits, and the occurrence of northern 
 bowlders, 100 to 150 pounds in weight at least, as far south 
 as the State of Mississippi. Facts prove also that the cold 
 waters and ice in the Gulf were destructive to the tropical 
 life along its northern borders. 
 
 These river- valley deposits form at present elevated plains 
 on one or both sides of the valley. Their elevation above the 
 river is greater in Northern New England than in Southern ; 
 and there is, in general, a like difference between those of the 
 northern and southern parts of the States west of New Eng- 
 land ; this height, in valleys remote from the coast, is mainly 
 due to the height of the flood. 
 
 The view in Fig. 450 represents a scene on the Connecti- 
 cut, a few miles below Hanover in New Hampshire, where 
 there are three different levels, or terraces, in the alluvial 
 formation ; the upper shows the total thickness of the for- 
 mation down to the river-level. 
 
 As the Glacial flood declined, the waters gradually fell below 
 
QUATERNARY AGE. 
 
 357 
 
 the top of the flood-made valley formation, and in most cases 
 far below it, leaving it as a high terrace plain, with sometimes 
 one or more lower terraces (Fig. 450). The lower terraces 
 may have been made by changes in the river as it subsided ; 
 or they may be only different levels of the bottom of the great 
 Hooded stream, like the Hats at different depths in any broad 
 river or bay. The main channel of the flooded stream was 
 
 Fig. 450. 
 
 Terraces on the Connecticut River, south of Hanover, N. H. 
 
 kept large and deep where the flow along the valley was most 
 violent, and less deep where less violent. Terraces have often 
 great height above a narrow gorge, because the waters were 
 there dammed by floating ice or other means. 
 
 Terraces in river-valleys have sometimes resulted from an 
 elevation of the land, this giving a stream greater pitch, and 
 hence causing an excavation of its bed to a lower level. But 
 examples of such are mostly confined to the parts of river- 
 valleys toward the sea-coast. 
 
 In many places, the upper part of the terrace formation, 
 for 10 to 40 feet, is coarsely stony, while underneath it usu- 
 ally consists of sandy, pebbly, or clayey layers. This over- 
 lying coarse bed shows that the flood, toward the close of the 
 
358 CENOZOIC TIME. 
 
 glacier, was suddenly augmented in depth and violence. Such 
 coarse beds occur where the now was most violent, and they 
 often top one of the lower terraces, these being low because of 
 the violence of the flow over them. 
 
 The lacustrine deposits are of similar character to those of 
 the valleys, and of like distribution over the continent ; and 
 they are equally elevated above the present level of the water 
 they border. 
 
 The sea-border deposits, or those formed on sea-shores and 
 estuaries, are found at many places on the coasts of New Eng- 
 land, both the southern and eastern. At several localities in 
 Maine they afford shells at heights not far from 200 feet 
 above the sea-level. They form deposits of great thickness 
 along the St. Lawrence, as near Quebec, Montreal, and King- 
 ston ; at Montreal they contain numerous marine shells at a 
 height of 400 to 520 feet above the river. They border Lake 
 Champlain, being there 393 feet in height above its level ; 
 and, besides marine shells, the remains of a whale have been 
 taken from the beds. 
 
 In the Arctic regions similar deposits full of shells are 
 common, at different elevations up to 600 or 800 feet, and in 
 some places 1,000 feet, above the sea-level. 
 
 These sea-border deposits, now elevated, must have been at 
 the water-level, or below it, when they were formed ; that is, 
 in the Champlain period. The facts prove that the river St. 
 Lawrence was at that time an arm of the sea, of great breadth, 
 with the bordering land 400 to 500 feet lelow its present level; 
 that Lake Champlain was a deep lay opening into the St. Law- 
 rence channel, and that it had its whales and seals as 1 well as 
 sea-shells ; that the coast of Maine was in part 200 feet belov/ 
 its present level, and Southern New England 10 feet. 
 
 There is some reason for the opinion that the whole north- 
 ern portion of the continent was less elevated than now ; and 
 abo that the depression was greatest to the north, since the 
 sea-border Champlain formations on both the Atlantic and 
 Pacific sides are above the present sea-level, and at higher 
 
QUATERNARY AGE. 359 
 
 elevations to the north, or near the northern boundary of the 
 United States, than they are to the south. 
 
 The facts here stated with regard to elevated river- valley, 
 lacustrine, and sea-border formations in North America have 
 their parallel in Europe. In Great Britain the Glacial period 
 was followed by one of depression, in which its northern por- 
 tions were over 1,000 feet below their present level. The re- 
 markable terraces or benches of Glen Eoy, in Scotland, are 
 three in number, and 1,139, 1,039, and 847 feet above the 
 sea-level. In Sweden there are sea- border beds with shells 
 very similar to those of Maine and the St. Lawrence ; and 
 facts prove that the White Sea was then connected with the 
 Baltic, and possibly with the Caspian. 
 
 While, therefore, the facts relating to the Glacial period 
 favor the view that the northern portions of the continents 
 were then raised above their present level, those of the next or 
 Champlain period suggest that they were afterward beloiv 
 their present level. If so, there was an upward high-latitude 
 movement for the Glacial period and a downward for the 
 Champlain period; and the latter movement brought to its 
 close the era of ice, by occasioning a warm climate. 
 
 3. Recent Period. 
 
 When the Champlain period was in progress, the upper 
 plain of the sea-border formations, now so elevated, was at 
 the sea-level ; and the high alluvial plains along the rivers 
 were the flood-grounds of the rivers. The land has since been 
 raised ; and, consequently, the sea-border formations are now 
 high above tide-level. Some of them were of beach origin, 
 and the height of these equals nearly the amount of eleva- 
 tion; others were submerged mud-banks or sea-bottoms, as 
 proved by their fossils, and these were carried up to a less 
 height above the sea, according to their depth beneath its sur- 
 face. The formations thus elevated often make a series of 
 terraces or " benches " alon^ a coast. 
 
 O 
 
 The elevation also led the rivers over the elevated region, 
 
360 CENOZOiC TIME. 
 
 especially toward the coast, to erode their beds through the 
 Champlain deposits of the valley to a lower level, and so make 
 terraces on one or both sides, as represented in Fig. 451. But 
 the terraces over the continent away from the coasts may be 
 mainly due (p. 357) to the subsiding of the waters after the 
 Hood was at iU, height and had done its chief work of deposi- 
 tion, and only slightly, where at all, to this elevation. 
 
 Fig. 451. 
 
 Section of a valley with its terraces completed. 
 
 As already stated, the sea-border formations of both sides 
 of the continent are raised high above existing tide-level, and 
 most so to the north. Hence, while the Champlain period was 
 one of a low level in the continent, especially at the north 
 (certainly along its coasts, and probably over its whole 
 breadth), the Recent period began in a rising again, until 
 the region before depressed reached its present height ; and 
 this rising was greatest at the north. It is hence probable that 
 there were high-latitude oscillations in this part of geological 
 history an upward movement in the Glacial period, a down- 
 ward in the Champlain period, an upward again in the Recent 
 period ; but how far such changes were general over the hem- 
 isphere is unknown. It does not appear that the movement 
 resulted anywhere in the raising of a mountain-range. 
 
 In Europe there was a second Glacial era, in which the 
 njrtharu portions of that continent were again covered with 
 ice, and glaciers spread anew from the Alps over part of Low T er 
 Switzerland. It appears to have occurred at the close of the 
 Champlain period, and to have been connected witli the ris- 
 ing of the land that introduced the Recent period, the 
 rising having carried the land above its present level. Proofs 
 
QUATERNARY AGE. 361 
 
 of the occurrence of such an epoch are found in the remains 
 of the Eeindeer and other sub-arctic animals, in Southern 
 France (page 369), in deposits that are subsequent in date to 
 true Champlain deposits. 
 
 The Eecent period is, hence, opened by this second Glacial 
 epoch, while it closes with the modern or historical era. 
 
 Modern Changes of Level. 
 
 The sea, the rivers, the winds, and all mechanical and 
 chemical forces are still working as they have always worked ; 
 and, too, the earth is undergoing changes of level over wide 
 areas, although it has beyond question reached an era of com- 
 parative repose. 
 
 These changes of level are either paroxysmal, that is, 
 take place through a sudden movement of the earth's crust 
 as sometimes happens in connection with an earthquake ; or 
 they are secular, that is, result from a gradual movement 
 prolonged through many years or centuries. The following 
 are some examples : 
 
 1. Paroxysmal In 1822 the coast of Western South 
 America, for 1,200 miles along by Concepcion and Valparaiso, 
 was shaken by an earthquake, and it has been estimated that 
 the coast near Valparaiso was raised at the time 3 or 4 feet. 
 In 1835, during another earthquake in the same region, there 
 was an elevation, it is stated, of 4 or 5 feet at Talcahuano, 
 which was reduced after a while to 2 or 3 feet. In 1819 
 there was an earthquake about the Delta of the Indus, and 
 simultaneously an area of 2,000 square miles, in which the 
 fort and village of Sindree were situated, sunk so as to be- 
 come an inland sea, with the tops of the houses just out of 
 water ; and another region parallel with the sunken area, 50 
 miles long and in some parts 10 broad, was raised 10 feet 
 above the delta. These few examples all happened within 
 an interval of sixteen years. They show that the earth is 
 still far from absolute quiet, even in this its finished state. 
 
362 CENOZOIC TIME. 
 
 2. Secular, Along the coasts of Sweden and Finland, on 
 the Baltic, there is evidence that a gradual rising of the land 
 is in slow progress. Marks placed along the rocks by the 
 Swedish government, many years since, show that the change 
 is slight at Stockholm, but increases northward, and is felt 
 even at the North Cape, 1,000 miles from Stockholm. At 
 Uddevalla the rate of elevation is equivalent to 3 or 4 feet in 
 a century. 
 
 In Greenland, for 600 miles from Disco Bay, near 69 N.. 
 to the frith of Igaliko 60 43' N., a slow sinking has been 
 going on for at least four centuries. Islands along the coast, 
 and old buildings, have been submerged. The Moravian set- 
 tlers have had to put down new poles for their boats, and 
 the old ones stand "as silent witnesses of the change." 
 
 It is believed also that a sinking is in progress along 
 the coast of New Jersey, Long Island, and Martha's Vine- 
 yard, and a rising in different parts of the coast-region be- 
 tween Labrador and the Bay of Fundy. There are deeply 
 buried stumps of forest-trees along the sea-shore plains of 
 New Jersey, and other evidences of a change of level (G. H. 
 Cook.) 
 
 The above cases illustrate movements by the century, or 
 those slow oscillations which have taken place through the 
 geological ages, raising and sinking the continents, or at 
 least changing the water-line along the land. 
 
 This fact is to be noted, that these secular movements of 
 modern time over the continents are, for the most part, so far 
 as observed, high-latitude oscillations, just as they were in the 
 earlier part of the Quaternary. 
 
 Life of the Quaternary. 
 
 The invertebrate animals of the Quaternary, and probably 
 also the plants, were very nearly if not quite all identical 
 with existing species. The shells and other invertebrate 
 remains found in the beds on the St. Lawrence, Lake Cham- 
 
QUATERNARY AGE. ANIMAL LIFE. 363 
 
 plain, and on the coast of Maine, are similar to those now 
 found on the coast of Maine or Labrador, or farther north. 
 
 The life of the Quaternary of greatest interest is the Mam- 
 malian, which type, as regards brutes, culminated in the 
 Champlain period. This culmination was manifested in 
 (1) the number of species, (2) the multitude of individuals, 
 (3) the magnitude of the animals, the period in each of 
 these particulars exceeding the present time. 
 
 Along with the brute Mammals of the Quaternary ap- 
 peared also Man. 
 
 I. Brute Mammals. 
 
 1. Europe and Asia. The bones of Mammals are found in 
 caves that were their old haunts; in Drift and stratified 
 Champlain deposits along rivers and lakes; in sea-border 
 deposits ; in marshes, where the animals were mired ; in ice, 
 preserved from decay by the intense cold. 
 
 The caves in Europe were the resort especially of the 
 Great Cave-Bear (Ursus spelceus), and those of Britain of the 
 Cave-Hyena (Hycena spelcea). Into their dens they dragged 
 the carcasses or bones of other animals for food, so that relics 
 of a large number of species are now mingled together in 
 the earth, or stalagmite, which forms the floor of the cavern. 
 In a cave at Kirkdale, England, portions of a very large num- 
 ber of Hyenas have been made out, besides remains of an 
 Elephant, Lion, Tiger, Bear, Wolf, Fox, Hare, Weasel, Rhi- 
 noceros, Horse, Hippopotamus, Ox, Deer, and other species, all 
 then inhabitants of that country. A cave at Gaylenreuth is 
 said to have afforded fragments of at least 800 individuals of 
 the Cave-Bear. The Cave-Hyena is regarded as a large 
 variety of the Hyoena crocuta of South Africa, and the Cave 
 Lion, a variety of Felis leo, the Lion of Africa. But many of 
 the species are now extinct. 
 
 The fact that the numbers of species and of individuals in 
 the Quaternary was greater than now, may be inferred from 
 comparing the fauna of Quaternary Great Britain with that 
 
364 
 
 CENOZOIC TIME. 
 
 of any region of equal area in the present age. The species 
 included gigantic Elephants, two species of Rhinoceros, a Hip- 
 popotamus, three species of Oxen, two of them of colossal size, 
 the Irish Deer (Megaceros Hibernicus), whose height to the 
 summit of its antlers was 10 to 11 feet, and the span of 
 whose antlers was in some cases 12 feet, Deer, Horses, Wild 
 Boars, a Wild-cat, Lynx, Leopard, a Tiger larger than that of 
 Bengal, a large Lion called a Machcerodus, having sabre-like 
 canines sometimes eight inches long, the Cave-Hyena, Cav&* 
 Bear, besides various smaller species. 
 
 Fig. 452. 
 
 Skeleton of Mastodon giganteus. 
 
 The Elephant (Elcphas primigcnius) was nearly a third 
 taller than the largest modern species. It roamed over 
 Britain, Middle and Northern Europe, and Northern Asia, 
 even to its Arctic shores. Great quantities of tusks have 
 been exported from the borders of the Arctic sea for ivory. 
 
QUATERNARY AGE. ANIMAL LIFE. 365 
 
 These tusks sometimes have a length of 12 feet. Near the 
 beginning of the century one of these Elephants was found 
 frozen in ice at the mouths of the Lena ; and it was so well 
 preserved that Siberian dogs ate of the ancient flesh. Its 
 length to the extremity of the tail was 16 J feet, and its 
 height 9-J feet. It had a coat of long hair. But no amount 
 of hair would enable an Elephant now to live in those bar- 
 ren, icy regions, where the mean temperature in winter is 
 40 F. below zero. Siberia had also a hairy Rhinoceros. 
 
 Although there were many Herbivores among the Qua- 
 ternary species of the Orient, the most characteristic animals 
 were the great Carnivores. The period was the time of tri- 
 umph of brute force and ferocity, and the Orient was espe- 
 cially the scene of its triumph. 
 
 2. North America, In the Champlain period there were 
 great Elephants and Mastodons, Oxen, Hordes, Stays, Beavers, 
 and some Edentates, in Quaternary North America, unsur- 
 passed in magnitude by any in other parts of the world. 
 Herbivores were the characteristic type. Of Carnivores there 
 
 Fig 453. 
 
 Megatherium Cuvieri ( X T V- r 
 
 were comparatively few species ; no true cavern species have 
 been discovered. Fig. 452 (from Owen) represents the speci- 
 men of the American Mastodon now in the British Museum. 
 
366 CENOZOIC TIME. 
 
 The skeleton set up by Dr. Warren in Boston has a height 
 of 11 feet and a length to the base of the tail of 17 feet. 
 It was found in a marsh near Newburgh, New York. The 
 American Elephant was fully as large as the Siberian. 
 
 3. South America, South America had, at the same time, 
 its Carnivores, its Mastodons, and other Herbivores; but it 
 was most remarkable for its Edentates, or animals related to 
 the Sloths. 
 
 Fig. 453 shows the form and skeleton of one of these 
 animals, the Megath&re. It exceeded in size the largest 
 Rhinoceros : a skeleton in the British Museum is 18 feet 
 long. It was a clumsy, sloth-like beast, but exceeded im- 
 mensely the modern Sloth in its size. Another kind of 
 Edentate had a shell like a turtle, and was somewhat re- 
 lated to the Armadillo. One of them is called a Glyptodon 
 (Fig. 454). The animals of this kind were also gigantic, the 
 Glyptodon here figured having had a length, to the extrem- 
 ity of the tail, of nine feet. 
 
 South America was eminently the continent of Edentates. 
 
 Fig. 454. 
 
 Glyptodon clavipes 
 
 4. Australia. Quaternary Australia, in the Champlain 
 period, contained Marsupial animals almost exclusively, like 
 modern Australia ; but these partook of the gigantic size so 
 characteristic of the Mammalian life of the period. One 
 species, called Diprotodon, was as large as a Hippopotamus, 
 and another, the Nototherium. was as large as an ox. 
 
QUATERNARY AGE. MAN. 367 
 
 5. Conclusions. The facts sustain the following conclu- 
 sions : 
 
 1. The Champlain period of the Quaternary was the cul-j 
 minant time of Mammals, both as to numbers and magni- 
 tude. 
 
 2. Each continent was gigantic in that type of Mammalian 
 life which is now eminently characteristic of it : The Orient, 
 in Carnivores, and, it may be added, also in Monkeys ; North 
 America, in Herbivores ; South America, in Edentates ; Aus- 
 tralia, in Marsupials. 
 
 3. The climate of Great Britain and Europe, where were 
 the haunts of Lions, Tigers, Hippopotamuses, etc., must have 
 been warmer than now, and probably not colder than warm- 
 temperate. The climate of Arctic Siberia was such that shrubs 
 could have grown there to feed the herds of Elephants, and 
 hence could not have been bcloiv sub-frigid, for which degree of 
 cold it is possible the animals might have been adapted by 
 their hairy covering. 
 
 4. The Champlain period, the meridian time of the Quater- 
 nary Mammals, was hence, as before stated, one of warmer 
 climate over the continents than the present, and much 
 warmer than that of the Glacial period. The species may 
 have begun to exist before the Glacial period ended in Eu- 
 rope ; but they belonged pre-eminently to the Champlain 
 period, when the sinking of the land over the higher latitudes 
 had introduced the warmer climate. 
 
 5. The larger part of the great Mammals of the Quater- 
 nary disappeared with the close of the Champlain period or 
 in the early part of the Recent period, while others found 
 refuge in the tropics. They were animals of a warmer cli- 
 mate than now belongs to the regions which they then inhab- 
 ited ; and the cold of the second Glacial era, with which the 
 Recent period opened, probably brought about the extermina- 
 tion and forced migration. 
 
 Such an epoch of cold could not have been passed through 
 by Europe without some refrigeration of the climate of N@rth 
 
368 CENOZOIC TIME. 
 
 America, since the two continents are bound together by a 
 common Arctic. The remains of Reindeers have been found 
 in Southern New York and near New Haven in Connecticut ; 
 but the latter, at least, were found in Champlain deposits, and 
 are no evidence as to a second Glacial epoch. 
 
 Among the Mammals of Europe which existed before the 
 close of the Champlain period, some are now living ; as the 
 Eeindeer, Marmot, Ibex, Chamois, Elk, Wild Boar, Goat, Stag, 
 Aurochs, Urus, Wolf, Brown Bear, and others. 
 
 2. Man. 
 
 1. Relics of Man. The earliest relics of Man in Europe 
 are rude flint implements, as arrow-heads, chisels, etc. ; flint- 
 chippings, or the chips thrown off in making the implements ; 
 rude carvings ; human bones and skeletons ; the bones of the 
 animals used for food, split lengthwise, this being done to get 
 at the marrow ; charcoal, and other remains of fires. They 
 occur associated with the remains of the Cave-Bear, Cave- 
 Hyena, Cave-Lion, Elephant, and other species. They date 
 from the Champlain period, and perhaps, in part, from the 
 earlier Glacial period. 
 
 2. The Paleolithic Era, As the only implements of early 
 Man in Europe were of stone, the era in human history has 
 been called the " Stone age " ; and this earliest part of that 
 age, above referred to, has been designated the Paleolithic 
 era, from the Greek TraXato?, ancient, and X/#o?, stone. Por- 
 tions of skeletons referred to this era have been found in 
 Belgium, and some other countries. The Belgian skulls are 
 " fair average skulls " ; " the lowest yet discovered cannot be 
 regarded," says Huxley, as " the remains of a human bei no- 
 intermediate between Man and the Apes." The stone imple- 
 ments are never polished, and are of ruder make than those 
 of the later part of the Stone age. 
 
 3. The Reindeer Era. The second section of the European 
 Age of Stone has been called the Reindeer era. It was the 
 time of the second Glacial epoch, and it is distinguished by 
 
QUATERNARY AGE. MAN. 369 
 
 the occurrence of large numbers of the bones 01 the Rein- 
 deer in the caves of Southern France, along with the human 
 relics. The flint implements of this era are well made, but un- 
 polished ; and among the relics there are implements of bone 
 or horn, and drawings of animals upon these materials. One 
 of these drawings from Southern France, made on ivory, is 
 copied in Fig. 455. It represents the hairy Elephant of the 
 
 455. 
 
 Elephas primigenius ; engraved in ivory ( X f ). 
 
 era. Remains of the Elephant, Cave-Bear, Cave-Hyena, Cave- 
 Lion, occur in the same deposits, and also others of existing 
 species, as the Elk, Ibex, Aurochs, Urus, etc. Perfect skele- 
 tons of man have been found in some of the caverns. Those 
 of Southern France are in part of tall size, 5 feet 9 inches 
 to 6 feet, having well-shaped heads, and a large facial angle 
 (85). One, from a cave at Mentone (on the Mediterranean 
 near the borders of France and Italy), was of a man full 6 feet 
 in height ; and it lay buried in the stalagmite of the cave, 
 with flint implements and shell ornaments around, and a 
 chaplet of stag's teeth across its head. 
 
 4. The Neolithic Era. A third era is named the Neolithic 
 (from z/eo?, new, arid \i0os). The relics are polished stone im- 
 plements, broken pottery, bones of the dog. All remains of 
 extinct Champlain Mammals and the Reindeer are absent. 
 The race of men in Denmark resembled the Laplanders. 
 
 24 
 
370 
 
 CENOZOIC TIME. 
 
 To later time in this era belong the earlier "lake-dwellings " 
 of Switzerland, structures built on piles in the lakes in 
 which the only implements are of stone. But in the later, 
 about the western Swiss lakes, there are bronze implements, 
 and these are of the " Bronze age." 
 
 In America, rude stone implements have been found (first 
 by C. C. Abbot) in the stratified gravel near Trenton, N. J., 
 which has afforded also Mastodon bones; testifying to the 
 existence there of Man in the Chainplain period, if not in 
 the Glacial. The human skull reported from ancient gravels 
 of Calaveras County, California, is still of doubted antiquity, 
 and partly because so like a modern Indian's skull. 
 
 5. Modern Human Relics. In still later deposits, buried 
 coins, statues, temples, cities, are found among the earth's 
 fossils, contrasting strangely with the remains of the species 
 
 Figs 456, 457. 
 
 456 
 
 Iluman skeleton from Guadaloupe. 
 
 Conglomerate containing coins. 
 
 with which the history of the world's life began. Fig. 457 
 represents a coin conglomerate, containing coins of silver, of the 
 reign of Edward I., found at a depth of ten feet below the bed 
 
QUATERNARY AGE. MAN. 371 
 
 of the river Dove in England ; and Fig. 456, a portion of a 
 human skeleton firmly imbedded in a modern shell-limestone 
 of Guadaloupe, the former owner of which was two centuries 
 since a righting Carib. ?)fe^ 
 
 6. Man at the Head of the System of Life. With the crea- 
 tion of Man a new era in Geological history opens. In earliest "T 
 time only matter existed, dead matter. Then appeared life, , 
 - unconscious life in the plant, conscious and intelligent life in '^f^' 
 
 the animal. Asjes rolled by, with varied exhibitions of animal' , 
 
 $&<- ^\ 
 and vegetable life. Finally Man appeared, a being made of 
 
 matter and endowed with life, but, more than this, partaking'^ ' 
 of a spiritual nature. The systems of life belong essentially ' 
 to time ; but Man, through his spirit, to the opening and infinite^, 
 
 " 
 
 disobedience of any moral law, the only one subject to degra-^^ " 
 dation through excesses of appetite and violation of moral , 
 
 
 law, the only one with the will and power to make nature's J 
 forces his means of progress. 
 
 Man shows his exalted nature in his material structure. 
 His fore-limbs are not made for locomotion, as in all quad- 
 rupeds ; they are removed from the locomotive to the cephalic 
 series, being fitted to serve the head, and especially the intel- 
 lect and soul. Man stands erect, his body placed wholly 
 under the brain, to which it is subservient; and his feet 
 are simply for support and locomotion, and not, as in the 
 Monkeys, grasping or prehensile organs for climbing. His 
 whole outer being, in these and other ways, shows forth the 
 divine feature of the inner being. 
 
 3. Extinction of Species in Modern Times. 
 
 Species are becoming extinct in the present era, as they 
 have in the past. Man is now a prominent means of this 
 destruction. The Dodo, a laiye bird looking like an overgrown 
 chicken in its plumage and wings (Fig. 458), was abundant in 
 
372 CENOZOIC TIME. 
 
 the island of Mauritius until early in the commencement of 
 the eighteenth century. 
 
 Fig. 458. 
 
 Dodo, with the Solitaire in tae background. 
 
 The Moa or Dinornis is a New Zealand bird of the Ostrich 
 
CENOZOIC TIME. 373 
 
 kind that was living less than a century since ; it was 10 or 
 12 feet in height, and the tibia (" drumstick ") 30 to 32 inches 
 long. In Madagascar remains of a still larger bird, but of 
 similar character, occur, called an jfflpyomis ; its egg is over 
 a foot (13i inches) long. The Auk, a bird of Northern seas, 
 has become extinct within the last 25 years ; the last was 
 seen in 1844. These are a few of the examples of the modern 
 extinction of species. 
 
 The progress of civilization tends to restrict forests and 
 forest-life to narrower and narrower limits. The Buffalo once 
 roamed over North America to the Atlantic, but now lives 
 only on the Eocky Mountain slopes west of the Missouri Eiver. 
 The beaver, wolf, bear, and wild-boar were formerly common 
 in Britain, but are now wholly exterminated. 
 
 GENERAL OBSERVATIONS ON THE CENOZOIC 
 
 ERA. 
 
 1. Contrast between the Tertiary and Quaternary ages in geo- 
 graphical progress. The review of Cenozoic time has brought 
 out the true contrast in the results of the Tertiary and Qua- 
 ternary ages. 
 
 The Tertiary carried forward the work of rock-making and 
 of extending the limits of the dry land southward, southeast- 
 ward, and southwestward, which had been in progress through 
 the Cretaceous period, and, indeed, ever since Archaean time. 
 
 The Quaternary transferred the scene of operations to the 
 broad surface of the continent, and especially to its middle 
 and higher latitudes. 
 
 Through the Tertiary the higher mountains of the globe 
 had been rising and the continents extending ; and hence the 
 great rivers with their numerous tributaries which are the 
 offspring of great mountains on great continents began to 
 exist and to channel out the mountains and make valleys 
 and crested heights. In the Glacial epoch this work went 
 forward with special energy. The exposed rocks yielded 
 
374 CENOZOIC TIME. 
 
 before the moving glacier, and the earth and bowlders formed 
 were taken up ibr distribution over the continental surface. 
 Torrents, fed by the melting ice, were also at work, and with 
 even greater abrading power than the ice. Thus the excava- 
 tion of valleys and the shaping of hills and mountains were 
 everywhere in progress. In the Champlain period, the low 
 level at which the land lay, and the melting of the ice, with 
 the dropping of its earth and stones, enabled the flooded 
 streams to fill the great valleys deep with alluvium. In the 
 Recent period, which followed, the upward movements of the 
 land led to a completion of the terracing of the Champlain 
 deposits along the sea-shores and about the lakes and rivers, 
 and finished off the action of the rivers and vegetation in 
 spreading fertility over the land. 
 
 Thus, under the rending, eroding, and transporting power 
 of fresh water, frozen and unfrozen, eminently the great 
 Quaternary agent, in connection, probably, with high-lati- 
 tude oscillations of the earth's crust, the making of the earth 
 was finally completed. 
 
 2. Life. In the Cenozoic era, as in the preceding, species 
 were disappearing and others took their places. The Mam- 
 mals of the early Eocene are different in species from those 
 of the later ; and these from the Miocene, the Miocene from 
 the Pliocene, and the Quaternary from the Pliocene. 
 
 According to the present state of discovery, Mammals com- 
 menced in the Mesozoic era, late in the Triassic period, and 
 the Mesozoic species were all Marsupials. They were tho 
 precursor species, prophetic of that expansion of the new type 
 which was to take place after the Age of Eeptiles had closed 
 In the early Eocene, at the opening of the Age of Mam- 
 mals, appeared Herbivores and Carnivores of large size. Tho 
 Herbivores were mostly Pachyderms, related to the Tapir, 
 Hog, and Rhinoceros, and distantly to the Stag. The true 
 Stag family among Ruminants commenced in the Miocene ; 
 the Elephant tribe, in the Miocene ; the Bovine or Ox family, 
 in the Pliocene, or late in the Tertiary. 
 
LENGTH OF GEOLOGICAL TIME. 375 
 
 GENERAL OBSERVATIONS ON GEOLOGICAL 
 HISTORY. 
 
 1. Length of Geological Time. 
 
 By employing as data the relative thickness of the forma- 
 tions of the geological ages, estimates have been made of the 
 time-ratios of those ages, or their relative lengths (pages 269, 
 324). These estimated time-ratios for the Paleozoic, Meso- 
 zoic, and Cenozoic are 12 : 3 : 1. But the numbers may 
 be much altered when the facts on which they are based 
 are more correctly ascertained. It is quite certain that the 
 first of the Paleozoic ages the Silurian was, at the least, 
 four times as long as either the Devonian or Carboniferous ; 
 and probable that Mesozoic time was not less than three 
 times that of the Cenozoic. 
 
 Hence comes the striking conclusion that the longest age 
 of the world since life began was the earliest, when the 
 earth numbered in its population only Radiates, Mollusks, 
 and Marine Articulates, and, toward its close, Fishes. And 
 the time of the earth's beginnings before the introduction of 
 life must have exceeded in length all subsequent time. 
 
 The actual lengths of these ages it is not possible to deter- 
 mine even approximately. All that Geology can claim to do 
 is to prove the general proposition that Time is long. If time 
 from the commencement of the Silurian included 48 millions 
 of years, which some geologists would pronounce much too 
 low an estimate, the Paleozoic part, according to the above 
 ratio, would comprise 36 millions, the Mesozoic 9 millions, 
 and the Cenozoic 3 millions. 
 
 One of the means of estimating the length of past time is 
 that afforded by the rate of recession of the Falls of Niagara. 
 The river below the Falls flows northward in a deep gorge, 
 with high rocky walls, for seven miles, toward Lake Ontario. 
 It is reasonably assumed that the gorge has been cut out by 
 the river, for the river is annually making progress of this 
 
376 HISTORICAL GEOLOGY. 
 
 very kind. From certain fossiliferous Quaternary beds over 
 the country bordering the present walls, and other evidence, 
 it is proved that the present gorge, about six miles long, was 
 made after the middle of the Champlain period. The pres- 
 ent annual progress of the gorge from the cutting and under- 
 mining action of the waters has been variously estimated 
 from three feet a century to one foot a year. At the larger 
 estimate of one foot a year, the six miles would have required 
 31,000 years ; or double this if six inches a year, as made by 
 one observer ; and if the estimate be one inch a year, or 8 J 
 feet a century, the time becomes nearly 380,000 years. The 
 calculation may be regarded as establishing, at least, the 
 proposition that Time is long, although it affords no satis- 
 factory numbers. Other modes of calculation fully establish 
 this general proposition. 
 
 2. Geographical Progress in North America 
 
 The principal steps of progress in the continent of North 
 America are here recapitulated : 
 
 1. The continent at the close of the Archaean lay spread 
 out mostly beneath the ocean (map, page 19 9). Although thus 
 submerged, its outline was nearly the same as now. The dry 
 land lay mostly to the north, as shown on the map. The 
 form of the main mass approximated to that of the letter V, 
 and it had a southeast and a southwest border nearly parallel 
 to its present outline. 
 
 2. Through the Paleozoic ages, as the successive periods 
 passed, the dry land gradually extended itself southward 
 owing to a gradual emergence : that is, the sea-border at 
 the close of the Lower Silurian was probably as far south 
 as the Mohawk Valley in New York ; at the close of the Upper 
 Silurian it extended along not far from the north end of 
 Cayuga Lake and Lake Erie ; and by the close of the Devo- 
 nian age the State was a portion of the dry land nearly to 
 its southern boundary. This progress southward of the sea- 
 
GEOGRAPHICAL PROGRESS. 377 
 
 border in New York may be taken as an example of what 
 occurred along the borders of the Archaean, to the west- 
 ward. In other words, there was through the Silurian and 
 Devonian ages a gradual southerly extension of the dry part 
 of the continent, that is, to the southeastward and the 
 southwestward. 
 
 By the close of the Carboniferous age, or before the opening 
 of the Mesozoic era, the dry portion appears to have so far 
 extended southwardly as to include nearly all the area east of 
 the Mississippi and north of the Gulf States, along with a part 
 of that west of the Mississippi, as far nearly as the western 
 boundary of Kansas. 
 
 3. Before the Silurian age began, and in its first period, 
 great subsidences were in progress along the Lake Superior 
 region, when the thick Huronian and Potsdam formations 
 were made. The facts show that the depression of the lake, 
 and probably that of some of the other great lakes, and 
 also that of the river St. Lawrence, began to form either 
 during the closing part of the Archaean age or in the early 
 part of the Silurian age. 
 
 4. During the Paleozoic ages, rock-formations were in pro- 
 gress over large parts of the submerged portions of the conti- 
 nent up to the sea-borders, and some vast accumulations of 
 sand were made as drifts or dunes over the flat shores and 
 reefs. These rock-formations had in general ten times the 
 thickness along the Appalachian region which they had over 
 the interior of the continent ; and they were mostly fragmental 
 deposits in the former region, while mostly limestones in the 
 latter. Hence two important conclusions follow : 
 
 First. The Appalachian region was through much of the 
 time an exposed shore-reef or flat of great extent, parallel in 
 course with the present sea-border as well as that of the 
 ancient Archsean area ; while the interior was a shallow sea 
 opening southward freely into the Gulf of Mexico, and only 
 during some few of the periods with the same freedom east- 
 ward directly into the Atlantic. Most of the western part 
 
378 HISTORICAL GEOLOGY. 
 
 of the sea (west of Missouri) appears to have been too deep 
 for deposits between the Lower Silurian and Carboniferous 
 eras. 
 
 Secondly. The Appalachian region was undergoing, through 
 the Silurian and Devonian ages, great changes of level, the 
 deposits having been made in shallow waters ; the region was 
 slowly sinking, not faster than the rate of deposition, and the 
 amount of subsidence exceeded by ten times that in the In- 
 terior Continental region. 
 
 5. Of this Appalachian region, the Green Mountain por- 
 tion was upturned, rendered metamorphic, and elevated above 
 the ocean's level, at the close of the Lower Silurian; and 
 at the same time the valley of Lake Champlain and Hudson 
 Eiver was formed, if not earlier begun. 
 
 This valley and the depressions of the Great Lakes, and 
 also those of the lakes extending in a line through British 
 America northwestward from Lake Superior to the Arctic 
 regions, lie not far from the borders of the Archaean continent, 
 and, therefore, between the portion of the continent that was 
 comparatively stable dry land from the time of the Archaean 
 onward, and that portion which was receiving rock-formations 
 and undergoing oscillations of level. To this they appear to 
 owe their origin. 
 
 6. As the Paleozoic era closed, an epoch of revolution oc 
 curred, in which the rocks of the Appalachian region south of 
 New York and west of the Blue Eidge underwent (1) extensive? 
 flexures or foldings ; (2) immense faultings in some parts ; (3) 
 consolidation, and, in some eastern portions, crystallization 
 or metainorphism, with the loss of bitumen by the coal-beds 
 changing them into anthracite. These changes affected the 
 region from New York to Alabama. The effects of heat and 
 uplift were more decided toward the Atlantic than toward the 
 interior, showing that the force producing the great results 
 was exerted in a direction from the Atlantic inland, or from 
 the southeast toward the northwest. The Alleghany Moun- 
 tains were then made ; and they were, consequently, in ex- 
 istence when the Mesozoic era opened. 
 
GEOGRAPHICAL PROGRESS. 379 
 
 These mountains are parallel to the eastern outline of the 
 original Archaean continent. 
 
 Similar changes may have taken place on the Pacific side ; 
 but the facts thus far observed are opposed to such a con- 
 clusion. 
 
 This epoch of revolution was a time of mountain-making 
 also in Europe. 
 
 7. In the early or middle Mesozoic period (the continent 
 being largely dry land, as stated in the latter part of 2), 
 long depressions in the surface of the continent, made in the 
 course of the Appalachian revolution and situated between 
 the Appalachians and the sea-border, were brackish-water 
 estuaries, or were occupied by fresh-water marshes and 
 streams ; and Mesozoic sandstone, shale, and coal-beds were 
 formed in them. The Connecticut Valley region of Mesozoic 
 rocks (page 285) is one example. At the same time there 
 were formations in progress over the Eocky Mountain region, 
 a vast area from which the sea was not excluded, or only in 
 part. At the close of the Jurassic period, the Sierra Nevada, 
 and some other great ranges on the western side of the con- 
 tinent were made. 
 
 8. In the later Mesozoic, or the Cretaceous period, the 
 continent had its Atlantic and Gulf border yet under water, 
 and Cretaceous rocks were formed about them, and thus the 
 continent continued its former course of enlargement south- 
 eastward (see map, page 320). The Western Interior sea, 
 opening south into the Gulf of Mexico, just alluded to, still 
 existed, and deposits were made in it over a very large part 
 of the great region reaching from Kansas on the east to the 
 Colorado on the west and north perhaps to the Arctic Ocean. 
 The Pacific border was also receiving an extension like the 
 Atlantic, 
 
 9. In the early Cenozoic, or the Tertiary age, the extension 
 of the Atlantic and Pacific borders was still continued. With 
 its close the progress of the continent in rock-making south- 
 eastward and southwestward was very nearly completed. 
 
380 HISTORICAL GEOLOGY. 
 
 After the Eocene era had in part passed, at the close of 
 the Lignitic period, there was the making of the Wahsatch 
 Mountains and other ranges in the Eocky Mountain region, 
 and of Coast ranges, west of the Sierra Nevada in California. 
 
 The Western Interior sea became greatly contracted after 
 this last mountain-making epoch hy the progressing elevation 
 of the Rocky Mountain region, and the Mexican Gulf reduced 
 greatly in size (map, page 345). During the middle of the 
 Eocene Tertiary, the Ohio and Mississippi emptied into an 
 arm of the Gulf just where they now join their waters ; at 
 the close of the Eocene the Ohio had taken a secondary place 
 as a tributary of the Mississippi. The great Missouri River, 
 the real trunk of the Interior river-system rather than the 
 Mississippi, began its existence after the Cretaceous period, 
 and reached its full size only toward the close of the Tertiary, 
 when the Rocky Mountains finally attained their full height. 
 
 10. The elevation of the Rocky Mountains, like that of the 
 Appalachians, was the raising of the land along a region par- 
 allel with the outline of the original Archaean dry land (see 
 map, page 199). The elevation of the Sierra Nevada of Cali- 
 fornia was a doubling of this same line on the west ; while 
 the elevation of the trap ridges and red sandstone of the early 
 Mesozoic along the Atlantic border (page 286) was a doubling 
 of the line on the east ; finally the elevation of the Cretaceous 
 with the Lignitic Tertiary tripled the line of heights on the 
 Pacific side ; and the later elevation of the Miocene added a 
 fourth line of heights to the border of the great Pacific Ocean. 
 
 11. The continent being thus far completed, as the Qua- 
 ternary Age was drawing on, operations changed from those 
 causing southern extension to those producing movements 
 of ice and fresh waters over the land, especially in the higher 
 latitudes ; and thereby valleys, great and small, were exca- 
 vated over the continent ; earth and gravel were transported 
 and made to cover deeply the rocks and spread the continent 
 with fertile plains and hills ; and, as the final result, those 
 grand features and those qualities of surface were educed that 
 were requisite to make the sphere a fit residence for Man. 
 
PROGRESS OF LIFE. 381 
 
 3. Progress of Life. 
 
 1 Fact of progress of life, Life commenced, among 
 plants, in Sea-weeds ; and it ended in Palms, Oaks, Elms, the 
 Orange, Rose, etc. It commenced among animals in Lin- 
 gulce (Mollusks standing on a stem like a plant), Crinoids, 
 Worms, and Trilobites, and probably earlier in the simple sys- 
 temless Protozoans (page 185) ; it ended in Man. Sea-weeds 
 were followed by Lycopods, Ferns, and other Flowerless plants, 
 and by Gymnosperms, the lowest of Flowering plants ; these 
 finally by the higher Flowering species above mentioned, the 
 Palms and Angiosperms. Radiates, Mollusks, and Articulates, 
 which appeared in the early Silurian, afterwards had Fishes 
 associated with them; later, Reptiles; later, Birds and in- 
 ferior Mammals; later, higher Mammals, as Beasts of prey 
 and Cattle ; lastly, Man. 
 
 2. Progress from marine to terrestrial life, The Silurian 
 was eminently the marine age of the world. The plants 
 found fossil in the Silurian until near its close are sea- weeds, 
 and the animals all marine. The animals of the Devonian, 
 also, are largely marine ; but there is a step taken in terres- 
 trial life by the expansion of the type of land-plants, and the 
 appearance of Insects. 
 
 In the Carboniferous age, and through the Mesozoic era, 
 the continents, or large areas over them, underwent alterna- 
 tions between a submerged and a dry land state, leading a kind 
 of amphibian existence. The Carboniferous age had, besides 
 its aquatic life, Insects, Spiders, Centipedes, terrestrial Mol- 
 lusks, Amphibian and other Eeptiles, and a great profusion 
 of forest-trees and other terrestrial vegetation. In the Meso- 
 zoic, to Reptiles were added Birds and Mammals, eminently 
 terrestrial kinds of life. 
 
 The Cenozoic was distinctively a continental era. The 
 continents became mostly dry land after its earliest period ; 
 and, as the Age of Man approached, they had their full size 
 and their present diversities of surface' and climate. With 
 
332 HISTORICAL GEOLOGY. 
 
 the increased variety of conditions fitted for terrestrial life 
 there was, beyond question, a great augmentation in the 
 number and variety of terrestrial species. Birds and Insects 
 have probably their greatest numbers and variety of species 
 in the present age. Marine species still abound, but rela- 
 tively to the terrestrial they are far less numerous and less 
 extensively distributed than in the Mesozoic and earlier ages. 
 
 3. Progress was connected with a constant change of species, 
 new species appearing as others disappeared. No species of 
 animal survived from the beginning of life on the globe to 
 the present time, nor even through a single one of the several 
 geological ages ; and but few lived on from the beginning of 
 any one of the many periods to its close, or from one period 
 into another. 
 
 There were widespread exterminations, closing some of 
 the ages, as the Carboniferous and the Eeptilian ; there were 
 less general exterminations, closing the periods on each of the 
 continents; and others, still less general, at intermediate 
 epochs; and often some disappearances accompanied each 
 change in the rock-depositions that were in progress. For, 
 in passing from one bed to another above, some fossils fail 
 that occur below; and from the strata of one epoch to an- 
 other, still larger proportions disappear ; and sometimes with 
 the transitions to rocks of another period or age, very nearly 
 all the species are different. The rocks of the continents, 
 that are open to examination, were made in Continental seas 
 and the borders of the oceans adjoining; and hence their 
 testimony with reference to exterminations does not extend 
 to the Oceanic areas. 
 
 Of all genera of animals now having living species, only 
 one, the Mplluscan genus Distinct,, had species also in the 
 earliest Silurian, unless the Lingulelicc, of the Primordial, 
 were, as formerly supposed, true Lingulct. Every other genus 
 of that early time sooner or later numbered only extinct spe- 
 cies. Afterward in the Lower Silurian, Nautilus and a few 
 others were added to Di&wna. 
 
PROGRESS OF LIFE. 383 
 
 Such unbroken lines prove the oneness of plan or system 
 through geological history. 
 
 Nearly fifteen hundred species of Trilobites have been 
 found fossil in the Paleozoic rocks, and in later formations 
 none. Over 1,000 species of the Ammonite group occur in 
 the Mesozoic rocks, the last then, or in the early Tertiary, 
 disappeared. 500 species of the Nautilus tribe have been in 
 existence : now there are but two or three. Over 1,000 spe- 
 cies of Ganoids have been found fossil : the tribe is now 
 nearly extinct. The remains of 2,500 species of plants and 
 over 40,000 species of animals have been found in the rocks, 
 not one of which is now in existence. Thus the old has been 
 ever passing away. But the number of kinds of fossils dis- 
 covered cannot be the number of species that have existed ; 
 and the above numbers of marine species may safely be mul- 
 tiplied by ten, and of terrestrial by a thousand. 
 
 4. Progress not always begun by the introduction of the low- 
 est species of a group. Mosses, although inferior to Lycopods 
 and Ferns, appear to have been of later introduction, for no 
 remains have been found in the Carboniferous or Devonian 
 rocks, although there are relics of both of the other tribes of 
 plants. 
 
 The earliest of Fishes, instead of being those of lowest 
 grade, were among the highest : they were Ganoids, or reptil- 
 ian Fishes. Trilobites, found in the first fauna of the Silu- 
 rian, are not the lowest of Crustaceans. No fossil Snakes 
 have been found below the Cenozoic, although large Eeptiles 
 abounded in the Mesozoic. Oxen date from the later Ter- 
 tiary, long after the first appearance of many higher Mam- 
 mals, as Tigers, Dogs, Monkeys, etc. 
 
 There was upward progress in the grand series of species, 
 as stated on page 381 ; but there was not progress in all cases 
 from the lowest species to the highest. 
 
 5. The earliest species of a group were often those of a compre- 
 hensive type. The Ganoid fishes are an example of these 
 comprehensive types. As stated on page 238, they were in- 
 
384 HISTORICAL GEOLOGY. 
 
 termediate in some respects between Fishes and Eeptiles; 
 they were fishes comprehending in their structure some Rep- 
 tilian characters, and hence called comprehensive types. 
 
 The earliest Mammals were Marsupials, or species of Mam- 
 mals comprehending in their structure some characteristics of 
 oviparous Vertebrates (see page 176), and, therefore, in certain 
 respects intermediate between Mammals and Oviparous Ver- 
 tebrates. 
 
 The vegetation of the coal-era consisted largely of trees al- 
 lied to the Lycopods or Ground-pine of the present day ; and 
 these, as well as the Lycopods, constitute a type intermediate 
 in some points between Ferns and Pines or Conifers (page 
 233). 
 
 In the Mesozoic the most characteristic plants w r ere Cy- 
 cads; and these comprehended in their structure something 
 of three distinct types. They are closely like Conifers in 
 structure and fruit ; but they are like Ferns in the way the 
 leaves unfold and in some other points, and like Palms in 
 their foliage (page 288). 
 
 These comprehensive types embraced in their natures usu- 
 ally the features of some type that was to appear in the fu- 
 ture. Thus, the Ganoid fishes of the Devonian foreshadowed 
 the Amphibians, the first fossils of which occur afterward in 
 the early Carboniferous. 
 
 6. Harmony in the life of a period or age, Through the ex- 
 istence of these comprehensive types, and also in other ways, 
 there was always a striking degree of harmony between the 
 species making up the population or the fauna and flora 
 of each period in the world's history. 
 
 Among the plants of the Carboniferous age there were - 
 (I) the highest of the Cryptogams, or Flowerless plants, the 
 Ferns ; (2) the lowest of Phenogams (Gymnosperms), or Flow- 
 ering plants, species having only inconspicuous and imperfect 
 flowers, and hence almost flowerlcss ; and (3) the intermediate 
 types of Lycopods (Lepidodendrids and Sigillarids). 
 
 Again, in the Mesozoic the terrestrial Vertebrate life in- 
 
PROGRESS OF LIFE. 385 
 
 eluded (1) Reptiles, which are oviparous species ; (2) Birds, 
 also oviparous species ; (3) reptilian Birds, having long tails 
 like the Reptiles, and in part, at least, true teeth, a compre- 
 hensive type ; (4) Reptiles that had the hollow leg-bones, and 
 the biped locomotion, of birds, with some other bird-like char- 
 acteristics; (5) semi-oviparous Mammals, or Marsupials, an 
 intermediate type between ordinary Mammals and the ovip- 
 arous Reptiles and Birds. 
 
 7. Causes of the extinction of species and tribes. 1. Some 
 cpecies of plants and animals require dry land for their sup- 
 port and growth ; some, fresh-water marshes or lakes ; some, 
 brackish water ; some, sea-shore or shallow marine waters ; 
 some, deeper ocean-waters. 
 
 Hence (a) movements in the earth's crust submerging large 
 Continental areas, or raising them from the condition of a sea- 
 bottom to dry land, would exterminate life : sinking them 
 in the ocean, extinguishing terrestrial life ; raising them from 
 the ocean, extinguishing marine life. In early times, when 
 the Continental surface was in general nearly flat, a change of 
 level of a few hundred feet, or perhaps of even 100, would 
 have been sufficient for a wide extermination. If a modern 
 coral island were to be raised 150 feet, its reef-forming corals 
 would all be killed ; or if sunk in the ocean 150 feet, the 
 same result would follow, because the species do not groAV 
 below a depth of 100 feet. And if all the coral-reefs of the 
 Pacific Were simultaneously sunk or raised to the extent 
 stated, there would be a total extinction of a large number of 
 species. 
 
 (&) Along a sea-coast, the bays and inlets sometimes are 
 closed by barriers thrown up by the sea, and hence become 
 fresh, killing all marine life. Again, barriers are often washed 
 away by the sea, and then salt water enters, destroying fresh- 
 water life. 
 
 2. Species also endure a limited range of temperatures : 
 some are confined thereby to the equatorial regions only; 
 some, to the cooler part of the tropical zone ; some, to the 
 
386 HISTOKICAL GEOLOGY. 
 
 warmer temperate latitudes ; some, to the middle temperate ; 
 some, to the colder temperate ; some, to the frigid zone ; and 
 few species live through two such zones. So also, for the 
 same reason, they are confined to specific ranges of height 
 above the sea-level ; or of depths below the ocean's surface. 
 
 Hence, (a) as the earth has gradually cooled in its climates 
 from a time of universal tropics to that of the present condi- 
 tion, the larger part of those tribes or families that were fitted 
 for the earlier condition of the globe in the course of time 
 became extinct. 
 
 Again, (6) any temporary change of climate over the 
 globe from cold to warm or warm to cold would have 
 exterminated species. An increase in the extent and height 
 of Arctic lands would have increased the cold directly, be- 
 sides shutting out from the northern seas the warm cur- 
 rents of the oceans ; and thereby cold winds would have 
 been sent south over the continents, and cold oceanic cur- 
 rents south along the borders of the oceans, or the Conti- 
 nental seas. This cause is one capable of carrying destruc- 
 tion over the Occident and Orient simultaneously. 
 
 On the contrary, a diminution in the extent of Arctic 
 lands, making the higher regions open seas, and opening the 
 Arctic to the warm currents of the oceans, or an increase in 
 the extent of tropical lands for the sun to heat, would have 
 increased the heat of the globe and sent a warm climate far 
 north. 
 
 Such changes are destructive to living species. It is sug- 
 gested on page 329 that the destruction of life at the close 
 of the Mesozoic may have arisen from the cause here ex- 
 plained. 
 
 3. Any cause that in past time led to variations in species 
 tended to obliterate old characteristics and introduce those 
 that were new. 
 
 8, A parallelism between the progress in the system of life and 
 the development from the embryo or young state of a species. 
 The young gar-pikes (Ganoids) of North American waters have 
 
PROGRESS OF LIFE. 387 
 
 a vertebrated tail ; and so it was with the Gars of the young 
 world. The young of the higher Crustaceans, Shrimps, Lob- 
 sters, and Crabs, are very similar, strangely similar, it might 
 be said by one not familiar with the generality of Nature's 
 laws, to many Crustaceans of the young world, that is, of its 
 earliest age after life began. Again, the young of the higher 
 Insects are grubs and caterpillars ; and these are related in 
 important respects to Worms, the lowest of Articulates and 
 the kind that long preceded Insects. This principle, announced 
 by Agassiz, might be illustrated by examples from all depart- 
 ments of the animal kingdom. 
 
 9, Progress always the gradual unfolding of a system. Man 
 the culmination of that system. There were higher and lower 
 species appearing through all the ages, but the successive pop- 
 ulations were still, in their general range, of higher and higher 
 grade ; and thus the progress was ever upward. The type or 
 plan of vegetation, and "the four grand types or plans of ani- 
 mal life, the Eadiate, Molluscan, Articulate, and Vertebrate, 
 were each displayed under multitudes of tribes and species, 
 rising in rank with the progress of time, and all under rela- 
 tions so harmonious and so systematic in their successions 
 that they seem like the expression in material living 
 forms of one divine purpose. A scheme carried forward 
 by infinite wisdom should exhibit, through each step of its 
 progress, that complete adaptation to external conditions 
 which pervades the actual system of Nature, and could result 
 in no other than this very system. Its progress, if by divine 
 power, should be, as zoological history attests, a development, 
 an unfolding, an evolution. 
 
 With every new fauna and flora in the passing periods, 
 %here was a fuller and higher exhibition of the kingdoms of 
 life. Had progress ceased with the Eeptilian age, the system 
 might have been pronounced the scheme of an evil demon. 
 But, as time moved on, higher races were introduced; and 
 finally Man came forth, not in strength of body, but in 
 the majesty of his spirit ; and then living nature was full 
 
388 HISTORICAL GEOLOGY. 
 
 of beneficence. The system of life, about to disappear as a 
 thing of the past, had its final purpose fulfilled in the crea- 
 tion of a spiritual being, one having powers to search into 
 the depths of nature and use the wealth of the world for 
 his physical, intellectual, and moral advancement, that he 
 might thereby prepare, under divine aid, for the new life in 
 the coming future. 
 
 Thus, through the creation of Man completing the system 
 of life, all parts of that system became mutually consistent 
 and full of meaning, and Time was made to exhibit its true 
 relation to Eternity. 
 
 10. The progress in the system of life, a progress in ceph- 
 alization. A frog in the young state is a tadpole ; that is, has 
 a long tail behind, and outside gills either side of the head, 
 and it is hardly above the lower fishes in grade. On passing 
 to the adult state, the body is shortened in behind by the loss 
 of the tail, the fish-like gills are dropped off from the head, and, 
 simultaneously, the anterior or head extremity becomes vastly 
 improved in its structure and functions. This transfer of 
 forces anteriorly marked in abbreviation behind and improve- 
 ment in the rest of the animal, especially in the organs of the 
 head, that is, cephalically (the Greek Ke$a\ri meaning luad} ) 
 is an example under the principle of cephalization. There is 
 similar headward progress in all development from the young 
 state, whatever the class of animal ; and in Man, at the head 
 of the system, many years pass before the structure has the 
 degree of cephalization that belongs to maturity. In a fly, 
 the young, a maggot, is much like a worm, the body consisting 
 of a number of similar segments and the head extremity little 
 superior to the opposite. But in the adult fly, this extremity 
 has its well-constructed head and senses, and the posterior ex- 
 tremity, besides being reduced in relative size, aids no longer 
 in locomotion ; the development is, in a wonderful degree, a 
 cephalization of the structure. Such examples of the prin- 
 ciple of cephalization are afforded by every part of the animal 
 kingdom. 
 
PROGRESS OF LIFE. 389 
 
 The principle is exemplified, also, in the relations of the 
 inferior species of a group to the higher. A Lobster and a 
 Crab (both Decapod Crustaceans) are essentially alike in fun- 
 damental points of structure. The Lobster has a very large 
 and powerful tail (abdomen), a long and loosely compacted 
 head, and also large and spreading head-organs ; while the 
 Crab, much the higher species, has the tail reduced to a small, 
 feeble organ, hid away in a groove under the thorax, and, at 
 the same time, the head and the organs of the senses and 
 mouth connected with it are closely compacted. Abbrevia- 
 tion behind, and compacting and improvement in front, con- 
 nected with differences of grade, are here well displayed. 
 
 Thus grade among the species of a group is marked by dif- 
 ferences in the degree of cephalization of the structure ; and 
 this is so through all groups. 
 
 If, then, difference in grade among species is manifested 
 in difference in cephalization, and if also the stages in the 
 development of a species mark progress in cephalization, it is 
 plain that the scheme of progress for the animal kingdom in- 
 volved throughout progressing cephalization. In geological 
 history there were vertebrate-tailed Ganoids before the non- 
 vertebrate-tailed, tailed Amphibians and Birds before the 
 tailless, Worms before the compact and highly cephalized 
 Insect, Shrimps and Lobsters before Crabs ; and so in other 
 branches of the Animal Kingdom. In Man, the last term in 
 the series, cephalization reached its extreme limit. 
 
 The system of progress hence involved also changes in ani- 
 mal structures. An animal with the high senses of an Insect 
 could not have the form of a Worm ; or those of a Crab, the 
 form of a Lobster ; or those of Man, the body or head of a 
 Monkey. 
 
 11. Were the intervals between species or groups in the suc- 
 cession, through past time, abrupt, or gradual ? As Geology is 
 the history of the progress of the earth and its life, the science 
 is naturally looked to for a decision of the great question, 
 Whether, in the succession of species during past time, there 
 
390 HISTORICAL GEOLOGY. 
 
 were gradual transitions between them or not. Its testimony 
 could not, however, be decisive, unless the record, in some 
 parts at least, were a nearly unbroken one. 
 
 There is abundant evidence that, to a large extent, it is, as 
 has been claimed, a very broken record. For example : there 
 is not, on the eastern half of North America, the Atlantic bor- 
 der included, a species of the marine Molluscan or Radiate 
 life of that border during the long Triassic and Jurassic periods. 
 That there were abundant species in the seas is evident from 
 the rocks of these eras in Europe. Coast deposits on the 
 Atlantic must have been made ; but they are out of reach be- 
 neath the ocean's waters. Again, two jaw-bones of one species 
 of Marsupial Mammal are all the relics that have been found 
 of these animals in rocks of the North American Triassic, 
 Jurassic, and Cretaceous periods, or the whole of Mesozoic 
 time ; and yet, if there were one species in the Triassic, and 
 two individuals, there were probably a large number of species, 
 and multitudes must have lived and died through the Meso- 
 zoic era. In Europe, one single specimen of a bird has been 
 found in Jurassic rocks, out of the myriads of individuals and 
 the great numbers of species that must then have lived. Only 
 a very few kinds of plants have been found in the Mesozoic 
 formations of North America, and yet, the continent must 
 have been buried in foliage through all the successive periods 
 after the Carboniferous age. 
 
 It has to be admitted that we know very little about the 
 past terrestrial life of the globe, and also that there are some 
 great breaks in the succession of marine life. Moreover, 
 breaks, as geological history shows, may exist where the rocks 
 follow one another consecutively without any apparent inter- 
 ruption. 
 
 Now, in the succession of species made known by geology, 
 the transitions connecting species or groups are abrupt, and 
 not gradual. Some of the links between genera have been 
 partially filled out by recent discoveries, as, for instance, that 
 between the modern Horse and the Tapir-like Mammals of 
 
PROGRESS OF LIFE. 391 
 
 the Eocene (page 341), and that between the Elephant and 
 the Mastodon, etc. ; but still the species and genera of Horses 
 stand apart. In the long geological succession of groups there 
 are even fewer examples of blendings than occur in existing 
 life. 
 
 Yet it has to be admitted that the above facts with regard 
 to the breaks in the series of rocks weaken greatly this evi- 
 dence against gradual transitions. And its force is further 
 lessened by the fact that geological exploration has not ex- 
 tended to all parts of the world, or exhausted discovery in the 
 portions that have been investigated. This is especially 
 true of the terrestrial life of the globe ; but not so strongly 
 with regard to the marine life, particularly the Paleozoic part, 
 since the rocks of the earlier ages are mainly of marine origin, 
 and abound in fossils. 
 
 There are still some breaks that are most remarkable, what- 
 ever allowance be made for imperfection of records. (1.) Tri- 
 lobites and Brachiopods come abruptly into geological history 
 with no recognizable traces of their antecedents. (2.) Fishes, 
 the first of Vertebrates, appear in the later Silurian, with no 
 species between them and the Invertebrates as their precursors. 
 (3.) The leaves of Angiosperms (or trees of modern tribes re- 
 lated to the Willow, Elm, Magnolia) and also the Palms, are 
 found fossil in the Cretaceous rocks of the continents, and none 
 whatever as yet in the Jurassic. 
 
 The Triassic rocks have afforded bones of the first Mam- 
 mals, Marsupial Mammals ; but nothing with regard to the 
 line of predecessors connecting them with inferior oviparous 
 species. The Tertiary rocks of all the continents abound, in 
 many places, in remains of true Mammals. Yet not a trace 
 of one has been found in the Cretaceous strata; and this is 
 true even in the Rocky Mountain region, where the strata are 
 mostly of shallow-water origin, and partly of fresh-water for- 
 mation. These last are examples, it is true, from terrestrial 
 species. But the very long blank antecedent to the Marsu- 
 pials and to the true Mammals may well suggest the pro- 
 
392 HISTORICAL GEOLOGY. 
 
 priety of making further search before assuming that in the 
 gradation upward there were no greater interruptions than are 
 illustrated by the variations among existing Mammals. 
 
 In the case of Man, the abruptness of transition is still 
 more wonderful. The Man-ape, nearest in structure to Man, 
 has a cranium of but 34 cubic inches in capacity, or half that 
 of the lowest of existing Man, and no link between has been 
 found. No human remains that the past fifteen years of 
 active search have brought to light afford evidence of the ex- 
 istence of a race less perfectly erect than existing Man, or 
 nearer to the Man-ape in essential characteristics. The Man- 
 apes of the present day, the Gorilla, Chimpanzee, and Orang- 
 Utan, are the terminations of lines of succession that reached 
 up to them. But, as to the line supposed to end in Man, not 
 the first link has been found. Thus geological discovery 
 leaves Man alone at the head of the system of life, far re- 
 moved from his nearest allies among the brute races. 
 
 12. Origin of Species. Such is the direct evidence from 
 Geology as to the transitions between species. The other 
 considerations, derived from Geology, that have been regarded 
 as bearing on the question of the origin of species, are 
 
 1. That the system of life exhibits so perfect harmony, 
 and so complete oneness of law in its several lines and suc- 
 cessions, that it may be truly called a system of development 
 or evolution, whatever the method by which it was carried 
 forward. 
 
 2. That since the physical progress of the globe was under 
 the action of natural law, so the same may naturally have 
 been true of its organic progress. 
 
 3. That, as regards geological history, time is long. 
 
 These arguments in themselves are an insufficient basis for 
 a settlement of the great question. 
 
 Science derives other evidences from the study of living 
 plants and animals ; but this is not the place for their presen- 
 tation. Still other arguments come from a priori, abstract, or 
 metaphysical considerations, and these too would be here out 
 of place. 
 
PROGRESS OF LIFE. 393 
 
 The biblical student finds, in the first chapter of Genesis, 
 positive statements with regard to the creation of living be- 
 ings. But these statements are often misunderstood ; for 
 they really leave the question as to the operation of natural 
 causes for the most part an open one, as asserted by Augus- 
 tine, among the Fathers of the Church, and by some biblical 
 interpreters of the present day; for it says that there were 
 but four fiats for the whole ; or but two, excluding the first 
 for the beginning of life, and the last for the creation of Man. 
 And it plainly implies that, after the fiats, that is, through 
 these expressions of the Divine Will, the new developments 
 went forward successively to the completion of the grand 
 system. 
 
 In view of the whole subject, the following appear to be 
 the conclusions most likely to be sustained by further re- 
 search. 
 
 1. The evolution of the system of life went forward through 
 the derivation of species from species, according to natural 
 methods not yet clearly understood, and with few occasions 
 for supernatural intervention. 
 
 2. The method of evolution admitted of abrupt transitions 
 between species ; as has been argued from the abrupt transi- 
 tions that occur in the development of animals that undergo 
 metamorphosis, and the successive stages in the growth of 
 many others. 
 
 3. External agencies or conditions, while capable of pro- 
 ducing modifications of structure, have had no more power 
 toward determining the directions of progress in the evolution, 
 than they now have in determining the course of progress in 
 development from a living germ. 
 
 4. For the development of Man, gifted with high reason 
 and will, and thus made a power above Nature, there was 
 required, as Wallace has urged, the special act of a Being 
 above Nature, whose supreme will is not only the source of 
 natural law, but the working force of Nature herself, 
 
394 CONCLUSION. 
 
 CONCLUDING REMARKS. 
 
 Geology may seem to be audacious in its attempts to unveil 
 the mysteries of creation. Yet what it reveals are only some 
 of the methods by which the Creator has performed his will ; 
 and many deeper mysteries it leaves untouched. 
 
 It brings to view a perfect and harmonious system of life, 
 but affords no explanation of the origin of life, or of any of 
 nature's forces. 
 
 It accounts for the forms of continents ; but it tells nothing 
 as to the source of that arrangement of the wide and narrow 
 continents and wide and narrow oceans that was necessary 
 to the grand result. 
 
 It teaches that strata were made in many successions as 
 the continents lay balancing near the water's level, sometimes 
 just above the surface, sometimes a little below ; but it does 
 not explain how it happened that the amount of water was 
 of exactly the right quantity to fill the great basin, and admit 
 of oscillations of the land beneath or above its surface by only 
 small changes of level ; for if the water had been a few hun- 
 dred feet below the level it now has, the continents would 
 have remained mostly without their marine strata, and the 
 plan of progress would have proved a failure ; or if as much 
 above its present level, the land through the earlier ages would 
 have been sunk to depths comparatively lifeless, with no less 
 fatal results both to the series of rocks and the system of 
 
CONCLUSION. 395 
 
 marine and terrestrial life ; and in the end there would have 
 been broad and narrow strips of dry land and archipelagoes, 
 in place of the expanded Orient and Occident. 
 
 It may be said to have searched out the mode of develop- 
 ment of a world. Yet it can point to no physical cause of 
 that prophecy of Man which runs through the whole history ; 
 which was uttered by the winds and waves at their work over 
 the sands, by the rocks in each movement of the earth's crust, 
 and by every living thing in the long succession, until Man 
 appeared to make the mysterious announcements intelligible. 
 For the body of Man was not made more completely for the 
 service of the soul, than the earth, in all its arrangements 
 from beginning to end, for the spiritual being that was to 
 occupy it. In Man, the bones are not merely the jointed 
 framework of an animal, but a framework shaped throughout 
 with reference to that erect structure which befits and can 
 best serve Man's spiritual nature. The feet are not the 
 clasping and climbing feet of a monkey ; they are so made as 
 to give firmness to the tread and dignity to the bearing of the 
 being made in God's image. The hands have that fashioning 
 of the palm, fingers, and thumb, and that delicacy of the 
 sense of touch, which adapt them not only to feed the mouth, 
 but to contribute to the wants of the soul and obey its 
 promptings. The arms are not for strength alone, for they 
 are weaker than in many a brute, but to give the greater 
 power and expression to the thoughts that issue from within. 
 The face, with its expressive features, is formed so as to re- 
 spond not solely to the emotions of pleasure and pain, but to 
 shades of sentiment and interacting sympathies the most 
 varied, high as heaven and low as earth, ay, lower, in de- 
 based human nature. And the whole being, body, limbs, and 
 head, with eyes looking, not toward the earth, but beyond an 
 infinite horizon, is a majestic expression of the divine feature 
 in Man, and of the infinitude of his aspirations. 
 
 So with the earth, Man's world-body. Its rocks were so 
 arranged, in their formation, that they should best serve Man's 
 
396 CONCLUSION. 
 
 purposes. The strata were subjected to metamorphism, and 
 so crystallized that he might be provided with the most per- 
 fect material for his art, his statues, temples, and dwellings ; 
 at the same time they were filled with veins, in order to supply 
 him with gold and silver and other treasures. The rocks were 
 also made to enclose abundant beds of coal and iron ore, that 
 Man might have fuel for his hearths and iron for his utensils 
 and machinery. Mountains were raised to temper hot climates, 
 to diversify the earth's productiveness, and, pre-eminently, to 
 gather the clouds into river-channels, thence to moisten the 
 fields for agriculture, afford facilities for travel, and supply 
 the world with springs and fountains. 
 
 The continents were clustered mostly in one hemisphere 
 to bring the nations into closer union ; and the two having 
 climates and resources the best for human progress, the 
 northern Orient and Occident, were separated by a narrow 
 ocean, that the great mountains might be on the remoter bor- 
 ders of each, and all the declivities, plains, and rivers be turned 
 toward one common channel of intercourse. So, also, the 
 species of life, both of plants and animals, were appointed 
 to administer to Man's necessities, moral as well as physical. 
 
 Besides these beneficent provisions, the forces and laws of 
 nature were particularly adapted to Man, and Man to those 
 laws, so that he should be able to take the oceans, rivers, and 
 winds into his service, and even the more subtle agencies, 
 heat, light, and electricity ; and the adjustments were made 
 with such precision that the face of the earth is actually 
 fitted hardly less than his own to respond to his inner being : 
 the mountains to his sense of the sublime, the landscape, with 
 its slopes, its trees, its flowers, to his love of the beautiful, and 
 the thousands of living species, in their diversity, to his various 
 emotions and sentiments. The whole world, indeed, seems 
 to have been made almost a material manifestation, in multi- 
 tudinous forms, of the elements of his own spiritual nature, 
 that it might thereby give wings to the soul in its heavenward 
 aspirings. It may therefore be said with truth that Man's 
 
CONCLUSION. 307 
 
 spirit was considered in the ordering of the earth's structure 
 as well as in that of his own body. 
 
 It is hence obvious that the earth's history, which it is the 
 object of Geology to teach, is the true introduction to human 
 history. 
 
 It is also certain that science, whatever it may accomplish 
 in the discovery of causes or methods of progress, can take no 
 steps toward setting aside a Creator. Far from such a result, 
 it clearly proves that there has been not only an omnipotent 
 hand to create, and to sustain physical forces in action, but 
 an all-wise and beneficent Spirit to shape all events toward a 
 spiritual end. 
 
 Man may well feel exalted to find that he was the final 
 purpose when the word went forth in the beginning, LET 
 LIGHT BE. And he may thence derive direct personal assur- 
 ance that all this magnificent preparation is yet to have a 
 higher fulfilment in a future of spiritual life. This assurance 
 from nature may seem feeble. Yet it is at least sufficient to 
 strengthen faith in that Book of books in which the promise 
 of that life and " the way " are plainly set forth. 
 
APPENDIX. 
 
 A. Map of the Vicinity of Naples. 
 
 THE accompanying map serves to illustrate the sketch on 
 page 130. It covers in breadth just 20 miles. It shows the 
 position of Vesuvius ; its cone and crater ; the cinder-cone 
 within the crater ; and the outer margin (called Sonima, on 
 
 the north) of a larger cone and crater, probably that of 
 A.D. 79, previous to the eruption which destroyed Pompeii. 
 The crater, after some of its eruptions, has been 2000 feet 
 deep ; at other times it has within a solid lava-plain near its 
 top, and a cinder-cone at centre, which was the case at the 
 time of the author's visit in June, 1834. To the southeast 
 of Vesuvius lies Pompeii, tufa-covered; and west of it, on 
 the coast, Herculaneum, beneath tufa of the year 79, the 
 lavas of six subsequent eruptions separated by thin layers of 
 soil, and the cities of Eesina and Portici. West of Naples, 
 
APPENDIX. 399 
 
 Lake d'Agnano occupies the crater of a volcano ; the Solfa- 
 tara, an area now of steaming fissures, with sulphurous and 
 other vapors, another; and Astroni is a volcanic cone made 
 of tufa. Pozzuoli, with the Temple of Serapis, whose few 
 standing columns bear evidence of great changes of level in 
 the land, occupies a point just west of the limits of the 
 map; and north of it are the volcanic cones of Monte Nuovo 
 (thrown up in 1538) and Monte Barbaro, of unknown date. 
 
 B. Catalogue of American Localities of Fossils. 
 
 THE following catalogue of American localities of fossils contains 
 only some of the more important, and is intended for the conven- 
 ience especially of the student-collector. 
 
 Localities of Fossils. 
 
 Acadian Group. Coldbrook, Ratcliffe's Millstream, St. John, New 
 Brunswick. Long Arm of Canada Bay, Newfoundland. 
 
 Potsdam Group. Swanton, Vt. Braintree, Mass. Keeseville (at 
 "High Bridge"), Alexandria, Troy, N. Y. Chiques Ridge, Pa. Falls of 
 St. Croix, Osceola Mills, Trempaleau, Wisconsin. Lansing, Iowa. St. 
 Ann's, Isle Perrot, C. W. Near Beauharnois on Lake St. Louis, C. E. 
 
 Calciferous. Mingan Islands, St. Timothy, and near Beauharnois, 
 C. E. Grand Trunk Railway between Brockville and Prescott, St. Ann's, 
 Isle Perrot, C. W. Amsterdam, Fort Plain, Canajoharie, Chazy, Lafarge- 
 ville, Ogdensburg, N. Y. 
 
 Quebec Group. Mingan Islands, Point Levi, Philipsburg, and near 
 Beauharnois, C. E. Point Rich, Cow Head, Newfoundland. Cuts in Black 
 Oak Ridge and Copper Ridge, Knoxville and Ohio Railroad, Tenn. Malade 
 City, Idaho. 
 
 Chazy Limestone. Chazy, Gal way, "Westport, N. Y. One to three 
 miles north of "the Mountain" Island of Montreal, C. E. St. Joseph's 
 Island, Sault Ste. Marie, C. W. Knoxville, Lenoir's, Bull's Gap, Kings- 
 port, Tenn. 
 
 Bird's-eye Limestone. Amsterdam, Little Falls, Fort Plain, Adams, 
 Watertown, N. Y. 
 
 Black River Limestone. Watertown, N. Y. Ottawa, C. W. 
 Island of Montreal, and near Quebec, C. E. 
 
 Trenton Limestone. Adams, Watertown, Boonville, Turin, Jackson- 
 burg, Little Falls, Lowville, Middleville, Fort Plain, Trenton Falls, N. Y. 
 Pine Grove, Aaronsburg, Potter's Fort, Milligan's Cove, Pa. Highgate 
 
400 APPENDIX. 
 
 Springs, Vt. Montmorency Falls and Beauport Quarries near Quebec, 
 Island of Montreal (quarries north of the city), C. E. Ottawa, Belleville, 
 Trenton (G. T. R. R., west of Kingston), C. W. Copper Bay, Mich. El- 
 kader Mills, Turkey River, Dubuque, Iowa. Falls of St. Anthony, St. 
 Paul, Mineral Point, Cassville, Beloit, Quimby's Mills near Benton, Wis. 
 Warren, Rockton, Winslow, Dixon, Freeport, Cedarville, Savanna, Rockford, 
 111. Murfreesborough, Columbia, Lebanon, Tenn. 
 
 Utica Slate. Turin, Martinsburg, Lorraine, Worth, Utica, Cold Spring, 
 Oxtimgo and Osquago Creeks near Fort Plain, Mohawk, Rouse's Point, N. Y. 
 
 Rideau River along railroad at Ottawa, bed of river two miles above, C. W. 
 Cincinnati Group. Pulaski, Rome, Lorraine, Boonville, N. Y. 
 
 Penn's Valley, Milligan's Cove, Pa. Oxford, Cincinnati, Lebanon, 0. 
 Madison, Richmond, Ind. Anticosti, opposite Three Rivers, C. E. 
 Weston on the Humber River, nine miles west of Toronto, C. W. Little 
 Makoqueta River, Iowa. Savannah, Green Bay, "Wis. Thebes, Alexander 
 County ; Savanna, Carroll County ; Scales's Mound, Jo Daviess County ; 
 Oswego, Yorkville, Kendall County ; Naperville, Dupage County ; Wilming- 
 ton, Will County, 111. Cape Girardeau, Mo. Drummond's Island, Mich. 
 
 Nashville, Columbia, Knoxville, Tenn. 
 
 Medina Sandstone. Lockport, Lewiston, Medina, Rochester, N. Y. 
 Long Narrows below Lewistown, Pa. Dun das, C. W. 
 
 Clinton Group. Lewiston, Lockport, Reynolds Basin, Brockport, Roch- 
 ester, Wolcott, New Hartford, N. Y. Thorold on Welland Canal, Hamilton, 
 Ancaster, Dundas, C. W. Hanover, Ind. 
 
 Niagara. Lewiston, Lockport, Gosport, Rochester, Wolcott, N. Y. 
 ThoroM, Hamilton, Ancaster, C. W. Anticosti, C. E. Arisaig, Nova 
 Scotia. Racine, Waukesha, Wis. Sterling, Graf ton, Savanna, Chicago, 
 Joliet, 111. Marblehead on Drummond's Island, Michigan. Springfield, 
 Cedarville, Ohio. Delphi, Waldron, Jeffersonville, Madison, Logansport, 
 Peru, Ind. Louisville, Ky. The " glades " of West Tennessee. (Coral- 
 line Limestone. Schoharie, N. Y.) 
 
 Onondaga Salt Group. Buffalo, Williamsville, Waterville, Jerusalem 
 Hill (Herkimer County), N. Y. Gait, Guelph (G. T. R, R.), C. W. 
 
 Lower Helderberg Limestones. Dry Hill, Jerusalem Hill (Herki- 
 mer County), Sharon, East Cobleskill, Judd's Falls, Cherry Valley, Carlisle, 
 Schoharie, Clarksville, Athens, N. Y. Pembroke, Parlin Pond, Me. 
 Gaspe, C. E. Arisaig, East River, Nova Scotia. Peach Point, opposite 
 Gibraltar, Ohio. Thebes, Devil's Backbone, 111. Bailey's Landing, Mo. 
 " Glades " of Wayne and Hardin Counties, Tenn. 
 
 Oriskany Sandstone. Oriskany, Vienna, Carlisle, Schoharie, Pucker 
 Street, Catskill Mountains, N. Y. Cumberland, Md. Moorestown and 
 Frankstown, Pa. Bald Bluffs, Jackson County, 111. Four miles S. W. 
 of St. Mary's, Ste. Genevieve County, Mo. 
 
 Cauda-galli Grit. Schoharie (Fucoides Cauda-galli), N. Y. 
 
 Schoharie Grit. - Schoharie, Cherry Valley, N. Y. 
 
 Upper Helderberg Limestones. Black Rock, Buffalo, Williamsville, 
 
APPENDIX. 401 
 
 Lancaster, Clarence Hollow, Stafford, Le Roy, Caledonia, Mendon, Auburn, 
 Onondaga, Cassville, Babcock's Hill, Schoharie, Cherry Valley, Clarksville, 
 N. Y. Port Colborne, and near Cayuga, C. W. Columbus, Delaware, 
 White Sulphur Springs, Sandusky, Ohio. Mackinac, Little Traverse Bay, 
 Dundee, Monguagon, Mich. North Vernon, Charlestown, Kent, Hanover, 
 Jeffersonville, Ind. Louisville, Ky. 
 
 Marcellus Shales. Lake Erie shore, ten miles S. of Buffalo, Lancaster, 
 Alden, Avon, Leroy, Marcellus, Manlius, Cherry Valley, N. Y. 
 
 Hamilton Group. Lake Erie shore, Eighteen Mile Creek, Hamburg, 
 Alden, Darien, York, Moscow, East Bethany, Bloomfield, Bristol, Seneca 
 Lake, Cayuga Lake, Skaneateles Lake, Moravia, Pompey, Cazenovia, Delphi, 
 Bridgewater, Richland, Cherry Valley, Seward, Westford, Milford, Portland- 
 ville, N. Y. Widder Station (G. T. R. R.), near Port Sarnia, C. W. New 
 Buffalo, Independence, Rockford, Iowa. Devil's Bake Ovan, Jackson 
 County, Moline, Rock ' Island, 111. Grand Tower, Mo. Thunder Bay, 
 Little Traverse Bay, Mich. Jeffersonville, Ind. Nictaux, Bear River, 
 Moose River, Nova Scotia. 
 
 Genesee Shale. Banks of Seneca and Cayuga Lakes, Lodi Falls, Mount 
 Morris, two miles south of Big Stream Point, Yates County, N. Y. 
 (Genesee or Portage. Delaware, Ohio. Rockford, North Vernon, Ind. 
 
 Danville, Ky.) 
 
 Portage Group. Eighteen Mile Creek on Lake Erie, Chautauqua Lake, 
 Genesee River at Portage, Flint Creek, Cashaqua Creek, Nunda, Seneca and 
 Cayuga Lakes, N. Y. 
 
 Chemung Group. Rockville, Philipsburg, Jasper, Greene, Chemung 
 Narrows, Troopsville, Elmira, Ithaca, Waverly, Hector, Enfield, Franklin, 
 X. Y. Gaspe, C. E. 
 
 Catskill Group. - Fossils rare. Richmond's quarry above Mount Up- 
 ton on the Unadilla, Oneonta, Oxford, Steuben County, south of the Canis- 
 teo, N. Y. 
 
 Subcarboniferous. Burlington, Keokuk, Columbus, Iowa. Quincy, 
 Warsaw, Alton, Kaskaskia, Chester, 111. Crawfordsville, Greencastle, 
 Bloomington, Spergen Hill, New Providence, Ind. Hannibal, St. Genevieve, 
 St. Louis, Mo. W T illow Creek, Battle Creek, Marshal, Moscow, Jonesville, 
 Holland, Grand Rapids, Mich. Mauch Chunk, Pa. Newtonville, Ohio. 
 Ice's Ferry, on Cheat River, Monongalia County, W. Va. Red Sulphur 
 Springs, Pittsburg Landing, White's Creek Springs, Waynesville, Cowan, 
 Tenn. Big Bear and Little Bear Creeks, Big Crippled Deer Creek, Miss. 
 Clarksville, Huntsville, Ala. Windsor, Horton, Nova Scotia. 
 
 Carboniferous. South Joggins, Pictou, Sydney, Nova Scotia. Wilkes- 
 barre, Shamokin, Tamaqua, Pottsville, Minersville, Tremont, Greensburg, 
 Carbondale, Port Carbon, Lehigh, Trevorton, Johnstown, Pittsburg, Pa. 
 Pomeroy, Marietta, Zanesville, Cuyahoga Falls, Athens, Yellow Creek, Ohio. 
 
 Charlestown, Clarksburg, Kanawha, Salines, Wheeling, W. Va. Saline 
 Company's Mines, Gallatin County ; Carlinville, Hodges Creek, Macoupin 
 County ; Colchester, McDonough County ; Duquoin, Perry County ; Mur- 
 
 26 
 
402 APPENDIX. 
 
 physborough, Jackson County ; Lasalle ; Morris, Mazon, and Waupecan Creeks, 
 Grundy County ; Danville, Pettys' Ford, Vermilion County ; Paris, Edgar 
 County ; Springfield, 111. Perrysville, Eugene, Newport, Horseshoe of Little 
 Vermillion, Veraiilliori County ; Durkee's Ferry, near Terre Haute, Vigo 
 County ; Lodi, Parke County ; Merom, Sullivan County, Ind. Bell's, Casey's, 
 and Union Mines, Crittenden County ; Hawesville and Lewisport, Hancock 
 County ; Breckenridge, Giger's Hill, Mulford's Mines, and Thompson's Mine, 
 Union County ; Providence and Madisonville, Hopkin's County ; Bonhar- 
 bour, Daviess County, Ky. Muscatine, Alpine Dam, Iowa. Leavenworth, 
 Indian Creek, Grasshopper Creek, Juniata, Manhattan, Kansas. Rockwood, 
 Emory Mines, Coal Creek, Careyville, Tenn. Tuscaloosa, Ala. 
 
 Triassic. Southbury, Middlefield, Portland, Conn. Turner's Falls, 
 Sunderland, Mass. Phoenixville, Pa. Richmond, Va. Deep River and 
 Dan River Coal-fields, N. C. 
 
 Cretaceous. Upper Freehold, Middletown, Marlborough, Blue Ball, 
 Monmouth County ; Pemberton, Vincenton, Burlington County ; Black- 
 woodtown, Camden County ; Mullica Hill, Gloucester County ; Woods- 
 town, Mannington, Salem County ; New Egypt, Ocean County, N. J. 
 Warren's Mill, Itawamba County ; Tishomingo Creek, R. R. cuts, Hare's 
 Mill, Carrollsville, Tishomingo County ; Plymouth Bluff, Lowndes County ; 
 Chawalla Station (M. & C. R. R.), Ripley, Tippah County ; Noxubee, Macon, 
 Noxubee County ; Kemper, Pontotoc and Chickasaw Counties, Miss. 
 Finch's Ferry, Prairie Bluff, on Alabama River ; Choctaw Bluff, on Black 
 Warrior River ; Greene, Marengo, and Lowndes Counties, Ala. Fox Hills, 
 Sage Creek, Long Lake, Great Bend, Cheyenne River, etc., Nebraska. 
 Fort Barker, Fort Hayes, Fort Wallace, Kansas. Fort Lyon, Santa Fe, 
 New Mexico. 
 
 Eocene. Everywhere in Tippah County ; Yockeney River ; New Pros- 
 pect P. 0., Winston County ; Marion, Lauderdale County ; Enterprise, 
 )larke County ; Jackson, Satartia, Yazoo County ; Homewood, Scott County ; 
 hickasawhay River, Clarke County ; Winchester, Red Bluff Station, Wayne 
 Bounty ; Vicksburg, Amsterdam, Brownsville, Warren County ; Brandon, 
 Byram Station, Rankin County ; Paulding, Jasper County, Miss. Clai- 
 oorne, Monroe County ; St. Stephen's, Washington County, Ala. Charles- 
 ton, S. C. Tampa Bay, Florida. Fort Washington, Fort Marlborough, 
 Piscataway, Md. Maiibourne, Va. Brandon, Vt. In New Jersey, at 
 Farmingdale, Squankum and Shark River, Monmouth Co. Green River, 
 Fort Bridger, Wyoming. Canada de las Uvas, Cal. 
 
 Miocene. Gay Head, Martha's Vineyard, Mass. Shiloh, Jericho, 
 Cumberland County, and Deal, Monmouth County, N. J. St. Mary's, Eas- 
 ton, Md. Yorktown, Suffolk, Smithfield, Richmond, Petersburg, Va. 
 Astoria, Willamette Valley, John Day Valley, Oregon. San Pablo Bay, 
 Ocoya Creek, San Diego, Monterey, San Joaquin and Tulare Valleys, Cal. 
 White River, Upper Missouri Region. Crow Creek, Colorado. 
 
 Pliocene. Ashley and Santee Rivers, S. C. Platte and Niobrara 
 Rivers, Upper Missouri. John Day Valley, Oregon. Sinker Creek, 
 Idaho. Alameda County, Cal. 
 
APPENDIX. 403 
 
 C. Geological Implements, Specimens, etc. 
 
 1. Implements. The student requires for his geological excur- 
 sions and research the following implements : 
 
 (1.) A hammer. If his object is to get specimens of hard rocks, or obtain 
 minerals from such rocks, it should have the form in Fig. 459, the edge being 
 in the direction of the handle. But if fossils are to be collected, 
 this edge should be transverse to the handle. The face should 
 be flat, and nearly square, with its edges sharp instead of rounded. 
 The socket for the handle should be large, that the handle may 
 be strong. The hammer, for ordinary excursions, should weigh 
 1 pounds exclusive of the handle ; the handle should be about 
 12 inches long. Another is required for trimming specimens, 
 weighing half a pound. 
 
 (2. ) A steel ch'iscl, 6 inches long, such as is used by stone- 
 cutters. Also, another half this size. 
 
 (3.) A clinometer, with magnetic needle attached. The best 
 kind is a clinometer-compass 3 inches in diameter, having a 
 square base about 3| inches each side, two sides of the base being parallel to the 
 north and south line of the compass. 
 
 (4.) A small magnet. A magnetized blade of a pocket-knife is a good 
 substitute. 
 
 (5.) A measuring-tape 50 feet long. The field geologist should know ac- 
 curately the measurements of his own body, his height, length of limbs, step 
 or pace, that he may use himself, whenever needed, as a measuring-rod. 
 
 (6. ) In many cases, a pick, a crow-bar, a sledge-hammer of 4 to 8 pounds' 
 weight, and the means of blasting, are necessary. 
 
 (7.) Besides the above, a barometer and surveyor's instruments are occa- 
 sionally required. Of the latter, a hand-level is a desirable instrument for 
 determining small elevations by levelling ; it is a simple brass tube, with 
 cross-hairs, bubble, and mirror. A first-rate aneroid barometer is excellent 
 for all heights between 5 feet and 2,000 feet ; and, having one, the hand- 
 level is superfluous. 
 
 2. Specimens. Specimens for illustrating the kinds of rocks 
 should be carefully trimmed by chipping to a uniform size, pre- 
 viously determined upon : 3 inches by 4 across, and 1 inch through, 
 is the size commonly adopted. In the best collections of rocks, the 
 angles are squared and the edges made straight with great precision. 
 They should have a fresh surface of fracture, with no bruises by 
 the hammer. It is often well to leave one side in its natural 
 weathered state, to show the eifects of weathering. 
 
 Specimens of fossils will, of course, vary in size with the nature 
 
404 APPENDIX. 
 
 of the fossil. When possible, the fossil should "be separated from 
 the rock ; but this must be done with precaution, lest it be broken 
 in the process ; it should not be attempted unless the chances are 
 strongly in favor of securing the specimen entire. The skilful use 
 of a small chisel and hammer will often expose to view nearly all 
 of a fossil when it is not best wholly to detach it. When the 
 fossils in a limestone are silicined (a fact easily proved by their 
 scratching glass readily and their undergoing no change in heated 
 ucid), they may be cleaned by putting them into an acid, and also 
 applying heat very gently, if effervescence does not take place 
 without it. The best acid is chlorohydric (muriatic) diluted one 
 half with water. 
 
 Collections both of rocks and fossils should always be made from 
 rocks in place, and not from stray bowlders of uncertain origin. 
 
 3. Packing. For packing, each specimen should be enveloped 
 separately in two or three thicknesses of strong wrapping-paper. 
 This is best done by cutting the paper of such a size that when 
 folded around the specimen the ends will project two inches (more 
 or less, according to the size of the specimen) ; after folding the 
 paper around it, turn in the projecting ends (as the end of the finger 
 of a glove may be turned in), and the envelope will need no other 
 securing. Pack in a strong box, pressing each specimen, after thus 
 enveloping it, firmly into its place, crowding wads of paper between 
 them wherever possible, and make the box absolutely full to the 
 very top (by packing-material if the specimens do not suffice), so 
 that no amount of rough usage by wagon or cars on a journey of a 
 thousand miles would cause the least movement inside. 
 
 4. Labelling. A label should be put inside of each envelope, 
 separated from the specimen by a thickness or more of the paper. 
 The label should give the precise locality of the specimen, and the 
 particular stratum from which taken, if there is a series of strata at 
 the place ; it should also have a number on it corresponding to a 
 number in a note-book, where fuller notes of each are kept, together 
 with the details of stratification, strike, and dip, sections, plans, 
 changes or variations in the rocks, and all geological observations 
 that may be made in the region. A specimen of rock or fossil of 
 unknown or uncertain locality is of very little value. 
 
APPENDIX. 
 
 405 
 
 D. List of Minerals and Rocks. 
 
 The minerals and rocks enumerated below are those of 
 highest importance to the geological student. The list of 
 minerals includes 100 specimens ; that of rocks, 70. Good 
 collections containing the 170 specimens numbered as be- 
 low and labeled can be purchased for twenty to twenty-five 
 dollars ; and all schools and academies in which the subject 
 is taught should be provided with one. The order in the fol- 
 lowing list of minerals is that of the author's small Manual 
 of Mineralogy. 
 
 Minerals. 
 
 1. Native Sulphur. 
 
 2. Graphite. 
 
 3. Native Copper. 
 
 4. Ckalcopyrite (Copper pyrites). 
 
 5. Malachite (Copper carbonate). 
 
 6. Galeuite (Lead sulphide) ; a, 
 
 coarsely crystallized ; b, fine 
 granular. 
 
 7. Sphalerite (Zinc blende) ; a, 
 
 brown or yellow ; b, black. 
 
 8. Calamine (Zinc silicate). 
 
 9. Cassiterite (Tin ore). 
 
 10. Pyrite (Iron disulphide) : a, cubes ; 
 b, massive ; c, decomposing and 
 having a copperas-like taste. 
 
 11 Pyrrhotite (Iron sulphide). 
 
 12. Hematite (Iron sesquioxide) : a, 
 
 ciystallized ; b, massive ; c, 
 earthy red oxide or ochre. 
 
 13. Magnetite (Magnetic iron ore) : a, 
 
 octahedral crystals ; b, granular 
 massive. 
 
 14. Limonite (Hydrous iron-sesqui- 
 
 oxide, Brown hematite) : a, 
 botryoidal or stalactitic ; b, 
 earthy or yellow ochre ; c, bog 
 iron ore. 
 
 15. Siderite (Iron carbonate) : a, light 
 
 gray ; b, dark brown from par- 
 tial alteration toward limonite. 
 
 16 Manganese oxide, either Pyrolu- 
 
 site or Psilomelane. 
 
 17 Corundum (Alumina, A1 2 3 ). 
 
 li Fluorite (Fluor Spar, Calcium flu- 
 oride) : a t crystal ; b, massive. 
 
 18. Gypsum (Hydrous calcium sul- 
 
 phate) : a, selenite ; b, massive 
 earthy. 
 
 19. Apatite (Calcium phosphate). 
 
 20. Guano : a, b, two varieties. 
 
 21. Calcite (Calcium carbonate) : a, 
 
 cleavage rhombohedron ; b, 
 crystalline ; c, travertine j d, 
 stalactite ; e, stalagmite. 
 
 22. Dolomite (Magnesian calcium car- 
 
 bonate). 
 
 23. Barite (Barium sulphate). 
 
 24. Quartz : a, crystals ; b, group of 
 
 crystals or drusy quartz ; c, 
 massive glassy ; d, smoky ; e, 
 opaque, pebbles, /, flint, horn- 
 stone, or chert ; g, jasper ; h, 
 chalcedony. 
 
 25. Opal : a, common ; b, infusorial 
 
 earth (Diatom earth, electro- 
 silicon of the shops). 
 
 26. Pyroxene : a, black or greenish- 
 
 black crystals in a volcanic 
 rock ; b, green pyroxene. 
 
 27. Amphibole : a, b, hornblende, 
 
 black, and greenish-black ; c, 
 
 actinolite, green ; d, treinolite, 
 
 white ; e, asbestus. 
 Beryl. 
 Chrysolite. 
 Garnet : a, dodecahedral crystal ; 
 
 b, trapezohedral or dodecahed'vl 
 
 crystals in the rock. 
 
 31. Zircon : 2 crystals. 
 
 32. Epidote. 
 
406 
 
 APPENDIX. 
 
 33, 34. The Micas. 33, Muscovite : 
 
 a, b, two varieties ; 34, Biotite. 
 35. Scapolite. 
 
 36-39. The Feldspars. 36, Labra- 
 dorite ; 37. Oligoclase ; 38, Al- 
 bite ; 39, Orthoclase; a, white; 
 
 b, flesh-colored. 
 
 40. Chondrodite. 
 
 41. Tourmaline : a, black crystal ; b, 
 
 specimen in the rock. 
 
 42. Andalusite : chiastolite in slate. 
 
 43. Cyanite. 
 
 44. Staurolite : 2 specimens. 
 
 45. Talc : a, foliated ; b, steatite (soap- 
 
 stone). 
 
 46. Glauconite (Green earth). 
 
 47. Serpentine : a, light green ; b, 
 
 48. Kaolinite (Kaolin). 
 
 49. Chlorite : massive granular. 
 
 50. Bitumen. 
 
 51. Mineral coal : a, anthracite ; I, 
 
 bituminous coal ; c, cannel cod ; 
 d, brown coal ; e, lignite. 
 
 52. Peat : a, imperfectly changed ; b, 
 
 good peat ; c, muck. 
 
 Rocks. 
 
 1. Fmgmental non-calcareous. 
 
 I. Sand : a, ordinary of seashore ; b, 
 
 magnetic iron sand with gar- 
 net sand, from seashore. 
 
 2. Clay : a, common brick-clay 
 
 (burns red) ; b, Fire-brick or 
 Potters' clay (burns white). 
 
 3. Sandstone : a, white or grayish ; 
 
 b, red ; c, brown ; d, granitic ; 
 e, laminated argillaceous (flag- 
 ging stone) ; f, micaceous. 
 
 4. Conglomerate : a, ordinary ; b, 
 
 grit ; c, calcareous. 
 
 5. Shale : a, gray or reddish ; b, car- 
 
 bonaceous (black). 
 
 6. Tufa (volcanic sandstone or con- 
 
 glomerate). 
 
 2. Metamorphic Rocks. 
 
 7. Granite : a, light gray ; b, flesh- 
 
 colored, not coarse ; c, coarse 
 vein granite ; d, porphyritic ; e, 
 a granite with outer part rusted 
 from partial decomposition. 
 
 8. Gneiss : a, b, two varieties. 
 
 9. Mica schist : a, b, two varieties ; 
 
 c, garnetiferous. 
 
 10. Hydromica schist : a, b, ordinary 
 varieties. 
 
 II. Chlorite schist. 
 
 12. Argillite (Roofing slate) : a, dark 
 
 gray or blackish ; b, red. 
 
 13. Syenyte or Quartz-Syenyte. 
 
 14. Syenyte-gneiss (Hornblende 
 
 gneiss). 
 
 15. Hornblende schist. 
 
 16. Dioryte. 
 
 17. Labradioryte. 
 
 18. Quartzyte. 
 
 19. Buhxstone. 
 
 3. Calcareous Rocks. 
 
 Limestone ; A, Uncrystalline : a, 
 common (better if fossiliferous) ; 
 b, black ; c, light colored ; d, 
 hydraulic ; e, chalk ; /, shell 
 limestone (from St. Augustine, 
 Florida) ; B, Crystalline or meta- 
 morphic : White marble ; g, 
 gray or clouded ; li, reddish or 
 brownish, (partially metamor- 
 phic of Tennessee, which con- 
 tains fossil corals of the Chajtetes 
 group). 
 
 Dolomite (Magnesian limestone) ; 
 a, uncrystalline ; b, crystalline, 
 white marble. 
 
 Verd-antique marble. 
 
 4. Igneous Rocks. 
 
 Doleryte : a, compact from East- 
 ern America Triassic areas (Dia- 
 base) ; b, same, hydrous or chlo- 
 ritic ; c, amygdaloidal ; d, from 
 modern eruptions ; e, dolerytic, 
 or ordinary lava ; /, scoriaceovis. 
 
 Peridotyte (Chrysolitic doleryte, 
 Basalt). 
 
 Trachyte : a, ordinary ; b, pum- 
 ice. 
 
 Felsyte : a, light gray or whitish ; 
 a, red porphyry. 
 
 Pitchstone or Pearlstone. 
 
 Obsidian. 
 
 Concretions: a, b, c, claystones, one 
 
 of them spherical ; d, oolyte. 
 Geode : 2 specimens. 
 Silicified wood : 2 specimens. 
 Silicified fossils in limestone. 
 
INDEX. 
 
 NOTE. The asterisk after the number of a page indicates that the subject referred to is 
 Illustrated by a figure. 
 
 Acadian group, 206. 
 Acalephs, 183,* 184. 
 Acanthoteuthis, 298.* 
 Acephals, 182* 
 Acrodus minimus, 178.* 
 
 nobilis, 178. x 
 Acrogens, 188. 
 
 Carboniferous, 251. 
 
 Devonian, 232, 
 Actinia, 183.* 
 Actinocrinus proboscidialis, 
 
 255* 
 
 JSpyornis, extinction of, 373. 
 Ages in Geology, 190, Ul. 
 Alabama period, 331, 332. 
 A:bite, 22. 
 Algae, 187. 
 
 Alleghany coal-area, 241. 
 Alluvial deposits, 99, 356. 
 Alps, glaciers in, 121. 
 Alum, 83. 
 
 Ambonychia bellistriata, 214.* 
 America, North, Geography of, 
 
 See GEOGRAPHY. 
 Ammonites, 293.* 
 
 Humphrey sianus, 206.* 
 
 Jason, 296.* 
 
 placenta, 317.* 
 
 tornatus, 297 * 
 
 of Mesozoic, 326. 
 Amphibians, 176, 291,* 300.* 
 Amphigenyte, 38. 
 Amphipods, 180.* 
 Amphitherium, 305.* 
 Amygdaloid, 143. 
 Anatifa, 180.* 
 Anchitheriuui,341.* 
 Anchura Americana, 64.* 
 Andalusite, 24. * 
 Angiosperms, 189. 
 
 Cretaceous, 312, 313.* 
 
 Tertiary, 334, 335.* 
 Animal kingdom, 173, 174. 
 Anisopus, tracks of, 292.* 
 Anogens, 186. 
 Ant-eaters, 344. 
 Anthracite, 25, 247- 
 
 basin, Penn. 160.* 
 Anthracite, origin of, 146, 281 
 
 vegetable tissues in, 260.* 
 Anticline, 55 * 66. 
 Apiocrinus, 65.* 
 
 Appalachian revolution, 277. 
 Appalachians, formation of, 
 164, 165, 168, 277, 378. 
 
 folded rocks of, 279.* 
 
 thickness of formations 
 
 of, 230, 277. 
 Araucariae, 189*. 
 Archjean time, 191, 199. 
 
 N. America, 199.* 
 Archseoniscus Brodiei,299.* 
 Archaeopteryx, 304.* 
 Archimedes reversa, 255.* 
 Arctic coal-area, 243. 
 Arenicola piscatorum, 180.* 
 Argillyte, 36. 
 Artesian wells, 105.* 
 Arthrolycosa, 256 * 
 Articulates, 175, 179, 180.* 
 Asaphus gigas, 214.* 
 Ascidians, 180. 
 Astarte Conradi, 336.* 
 Athyris conceutrica, 63.* 
 
 subtilita, 255.* 
 Atmosphere, agency of, 86. 
 Atolls, 78.* 
 Atrypa, 63,* 236.* 
 Auk, extinction of, 373. 
 Aulopora cornuta, 235.* 
 Australia, basaltic columns of, 
 145.* 
 
 Marsupials of, in Quater- 
 nary, 366. 
 Azoic. See ARCH.EAN. 
 
 Bacilaria paradoxa, 187.* 
 Baculites ovatus, 317.* 
 Bagshot beds, 334. 
 Bala formation, 212. 
 Barnacles, 180.* 
 Basalt, 38. 
 
 Basaltic columns, 48,* 145.* 
 Bathygnathus borealis, 292.* 
 Beach formations, 44, 45,* 
 
 112,113 ' 
 Bear, cave, 363. 
 Beetles, 256. 
 
 Belemnitella mucronata, 317.* 
 Belemnites, 297, 298,*,317.* 
 Belodon priscus, 292.* 
 Bembridge beds, 334. 
 Bernese Alps, 117. 
 Bilin, infusorial bed of, 336. 
 
 Biotite, 23. 
 Birds, 176. 
 
 Cretaceous, 320,* 321 .* 
 
 of Connecticut Valley. 
 293.* 
 
 of Solenhofen, 304,* 327. 
 
 Tertiary, 338. 
 Birdseye limestone, 211. 
 Bituminous coal, 25, 146, 247. 
 Black River limestone, 211. 
 Black slate of Devonian , 230. 
 Bog ore, 86. 
 Bore, 109. 
 
 Bowlders, 94, 119, 348, 341 
 Bracluopods, 63 * 181,* 182, 
 214 * 222,* 224,* 23o,* 
 255,* 275. 
 
 Brandon fossil fruits, 335.* 
 Breccia, 34 
 Brontotherium, 343. 
 Brown coal, 26, 311 332. 
 Bryozoans, 181,* 183 
 Buhrstone, Tertiary, 333. 
 Bulla speciosa, 64.* 
 Bunter Sandstein,287. 
 Buprestis, 299.* 
 
 Calamites, 188, 233, 251,* 253, 
 
 275. 
 
 in Triassic, 288 
 Calamopsis Danae, 335.* 
 Calaveras skull, 370. 
 Calcareous rocks, 31, 36. 
 Calciferous sand-rock, 211. 
 Calcite, 27.* 
 Callista Sayana, 337-* 
 Callocystites Jewettii 183.* 
 Calymene Blumenbachii, 180.* 
 
 215. 
 
 Cambrian, 207. 
 
 Camel, Tertiary American 342. 
 Canadian period, 210. 
 Cancer, 180.* 
 Canons, 94, 95.* 
 Caradoc sandstone, 212. 
 Carbon, 25. 
 Carbonates, 27,* 29. 
 Carbonic acid, 26, 83. 
 Carboniferous age, 240. 
 Carcharodon angiistidens, 
 
 178 * 337, 338.* 
 inegalodou, 837. 
 
408 
 
 INDEX. 
 
 Cardita planicosta. 336 * 
 
 Coelenterates, 175. 
 
 Decapods, 179, 180.* 
 
 Caryocrinus oruatus, 222.* 
 
 Coin-conglomerate, 370.* 
 
 Delta, of Mississippi, 101.* 
 
 Cascades, 94. 
 
 Colorado, canon of, 40, 95.* 
 
 Deltas, 100. 
 
 Catopterus gracilis, 291.* 
 Catskill period. 231. 
 
 Columnaria alveolata, 213. 
 Comatulids, 184. 
 
 Dendrophyllia, 183.* 
 Denudation, 57,* 91. 
 
 Cauda-galli grit, 229. 
 
 Comprehensive types, 383. 
 
 Desmids, 187, 234.* 
 
 Cave animals of Quaternary. 
 
 Concretions, 47,* 48.* 
 
 Detritus, 94. 
 
 363. 
 
 Conformable strata, 57.* 
 
 Devonian age, 229. 
 
 Cenozoic time, 329. 
 
 Conglomerate, 34. 
 
 hornstone, microscopic or 
 
 general observations on, 
 
 Conifers, 188,* 189, 233, 253. 
 
 ganisms in, 234. * 
 
 373. 
 
 Connecticut River sandstone 
 
 Diabase, 38. 
 
 Cephalaspis, 238.* 
 
 and footprints, 285. 
 
 Diamond, 25. 
 
 Cephalates, 181.* 
 
 terraces, 357.* 
 
 Diatoms, 67, 68,* 187,* 335 * 
 
 Cephalizatiou, progress in, 388. 
 
 trap rocks, 286. 
 
 in hornstone, 234.* 
 
 Cephalopods, 181.* 
 
 .Continents, basin -like shape 
 
 deposits of, 312. 
 
 of Mesozoic, 326. 
 
 of, 14.* 
 
 Tertiary, 335.* 
 
 Cestracionts, 178,* 179, 239, 
 
 origin of, 163. 
 
 Dikes, 43,* 143, 286. 
 
 299. 
 Chsetetes lycoperdon, 213, 
 
 Contraction a cause of change 
 of level, 156. 
 
 Dicotyledons, 188. 
 Dinoceras, 341.* 
 
 214.* 
 
 Coprolites, 68, 303. 
 
 Dinornis, extinction of, 372, 
 
 Chain -coral, 222,* 223. 
 
 Coral islands, 78,* 170. 
 
 Dinosaurs, 302, 338. 
 
 Chalcedony, 20. 
 
 reef of the Devonian, 
 
 Dinothere, 3i3.* 
 
 Chalk, 31,36,211,323. 
 
 229. 
 
 Dioryte, 36, 37. 
 
 Champlain period, 348, 355. 
 
 reefs, 74, 77.* 
 
 Dip, 52, 53.* 
 
 Chazy limestone, 211. 
 
 Corals, formation of, 64,* 184. 
 
 Diprotodon, 366. 
 
 Cheirolepis Traillii, 177.* 
 
 recent, 183.* 
 
 Dipterus. 238.* 
 
 Cheirofheriuni, 300.* 
 
 Coralline crag, 334. 
 
 Discina, 218, 382. 
 
 Chenmng period, 230. 
 
 Corallines, 66, 187. 
 
 Dislocated strata, 52. 
 
 Chlorite. 23. 
 
 Corniferous limestone, 229. 
 
 Dodo, extinction of, 371, 372.* 
 
 Chlorite schist, 35 
 
 period, 229. 
 
 Doleryte, 38, 39, M3. 
 
 Chonete? mesoloba 255.* 
 
 Cornwall lode, 43.* 
 
 Dolomite, 27. 
 
 setigera, 236.* 
 
 Crabs, 179, 180.* 
 
 Drift, 348. 
 
 Chrysolite. 38. 
 
 Crassatcllaalta.336.* 
 
 sand-beds, 45,* 88. 
 
 Cidaris Blumenbachii, 294.* 
 
 Craters, 130. 
 
 scratches, 88, 349, 350.* 
 
 Cinders, 131. 
 
 Crepidula costata, 337.* 
 
 Dripstone, 37 
 
 Cinuamomum, Tertiary, 335.* 
 Circumdenudation, 94. 
 
 Cretaceous period, 285, 310. 
 America, map of, 320. 
 
 Dromatherium sylvestre,294.* 
 Dudley limestone, 221. 
 
 Clathropteris. 289.* 
 
 Crevasses, 117. 
 
 Dunes, 88. 
 
 Clay, 33. 
 
 Crinoidal limestone, Subcar- 
 
 Dykes. See DIKES. 
 
 Clay-slate, slate, 36. 
 
 boniferous, 245. 
 
 Dynamical Geology, 62. 
 
 Cleavage, slaty, 49, 50,* 169. 
 
 Crinoids, 65 * 183,* 184. 
 
 
 Cliff-limestone, 230- 
 
 Jurassic, 294.* 
 
 
 Climate, cause of changes in, 
 
 Primordial, 208. 
 
 Eagre, 109. 
 
 124. 
 
 Silurian, 208, 214 * 222* 
 
 Earth, size and features of, 6. 
 
 Carboniferous, 262. 
 
 223. 
 
 relation to Man, 394. 
 
 Cretaceous, 323. 
 
 Subcarboniferous. 254, 
 
 features, origin of, 156. 
 
 Jurassic, 309. 
 
 255.* 
 
 interior of, 161- 
 
 Paleozoic, 273. 
 
 Crocodiles, 319. 
 
 Earthquakes, origin of, 102, 
 
 Quaternary, 367. 
 
 Crustaceans, 179, 180.* 
 
 138,157. 
 
 Tertiary, 347. 
 
 Cryptogams, 186, 187. 
 
 Ebb-and-flow structure, 45.* 
 
 Clinometer, 53 * 
 
 Crystalline rocks, 29. 
 
 Echini, 183.* 
 
 Clinton group, 219. 
 
 Crystallization. See META- 
 
 Mesozoic, 294.* 
 
 Coal, kinds of, 25. 
 
 MORPHISM. 
 
 Echinoderms, 183.* 
 
 formation of, 259. 
 deprived of bitumen, 281. 
 Coal-areas of Britain and Eu- 
 
 Ctenacanthus major, 257.* 
 Ctenoids, 176, 177.* 
 Currents, oceanic, 108, 110. 
 
 Edentates, Quaternary, 365.* 
 Edestosaurus, 318.* 
 Elephants, Quaternary, 364, 
 
 rope, 244.* 
 
 Cyanitc, 24. 
 
 365 
 
 - i -areas of N. America, 241, 
 
 Cyathophylloid corals, 185, 
 
 Tertiary, 343 
 
 242.* 
 
 213,214,*222 ; *235.* 
 
 Elephas primigenius, 364, 
 
 -beds, characters of 246 
 
 Cyathophyllum rugosum, 
 
 369.* 
 
 -beds, formation of, 261. 
 
 235.* 
 
 Elevation of coast of Sweden, 
 
 -beds of Triassic, 290. 
 
 Cycads. 189. 
 
 362. 
 
 -beds, flexures in, 278 * 
 
 Triassic and Jurassic, 
 
 of Alps, 34G. 
 
 -formation, rocks of, 245. 
 
 288.* 
 
 of Green Mountains, 216. 
 
 -plantsofRichmond,289* 
 
 Cycloids, 176, 177.* 
 
 of Himalayas, 346. 
 
 290. 
 -plants of the Carbonifer- 
 
 Cyclonema cancellata, 222 * 
 Cyclopteris linnseifolia, 289.* 
 
 of Rocky Mountains, 345. 
 of Western South Amer- 
 
 ous, 250.* 
 
 Halliana, 232.* 
 
 ica, 347. 
 
 Coccoliths, 66. 187 
 
 Cypris, 179. 
 
 of Quaternary, 348. 
 
 Coccosteus, 237 * 
 
 Cystideans, 183,* 223 
 
 Elevations, causes of, 128, 156. 
 
 Cockroaches, 256. 
 
 Cythere Americana, 180.* 
 
 Emery, 21. 
 
INDEX. 
 
 409 
 
 Enaliosaurs, 258,* 300,* 301,* 
 
 Freestone of Portland, Ct., 285. 
 
 Gypsiferous formation, 286. 
 
 319. 
 
 Fresh waters,actiou of, 90. 
 
 Gypsum, 104, 220, 24!). 
 
 Enorinus liliifonnis, 183,* 
 
 Fruits, Carboniferous, 253 * 
 
 Gyrodus umbilicus, 177.* 
 
 294.* 
 
 Tertiary, 334, 335.* 
 
 
 Endogens, 188,* 189. 
 
 Fungi, 187. 
 
 
 England, geological map of, 
 
 Fusuliua, 66.* 
 
 :Ialy sites catenulata, 222.* 
 
 244.* 
 
 Fusus Newberryi, 317.* 
 
 Hamilton period, 230. 
 
 Entomostracans, 179, 180.* 
 Eocene, 330. 
 
 
 Harmony iu the life of an age, 
 384. 
 
 Eosaurus Acadianus, 258.* 
 
 Ganges, detritus of, 99. 
 
 [lawaii, volcanoes or, 133,* 
 
 Eoscorpius carbonarius, 256.* 
 
 Saugue, 42. 
 
 136* 
 
 Eozoou, 203.* 
 
 Ganoids, 170, 177.* 
 
 Heat, 124, 128. 
 
 Ephemera, 291. 
 
 Carboniferous, 257.* 
 
 evidence of internal, 126. 
 
 Eiiuiseta, 188, 233, 253. 
 Equivalent strata, 59. 
 
 Devonian, 237.* 
 Triassic,291.* 
 
 Height of Aconcagua peak, 
 132. 
 
 Erie shale, 230. 
 
 Garnet, 24.* 
 
 of Sorata, 132. 
 
 Erosion by rivers, 90, 93, 102. 
 
 Gasteropods, 64,* 181,* 182. 
 
 of Shasta, 132. 
 
 glacial, 120. 
 
 Geanticline, 56, 169. 
 
 Hematite, 28. 
 
 oceanic, 107.* 
 Eruptions of volcanoes, 133. 
 
 Genera, long-lived, 275, 382. 
 Genesee shale, 230. 
 
 Hempstead beds, 334. 
 tlerculaneum, 13i>. 
 
 non-volcanic, 142. 
 
 Genesis, 393. 
 
 Elesperornis regalis, 320.* 
 
 Eschara, 181.* 
 
 Geodc, 48.* 
 
 Heterocercal, 177,* 238.* 
 
 Estheria ovata, 290.* 
 
 Geography, progress in North 
 
 Hipparion,341.* 
 
 Estuary formations, 100. 
 
 America, 163, 203, 204, 
 
 Hitchcock, E., tracks de- 
 
 Euplcctella speciosa, 314.* 
 
 272, 376. 
 
 scribed bv, 292.* 
 
 Eurypterus remipes, 224.* 
 
 American, in Archaean, 
 
 Holoptychius, 238.* 
 
 Exogens, 188.* 
 
 199 * 203, 269. 
 
 Ilomalonotus, 222.* 
 
 Exogyra costata, 316.* 
 
 in Carboniferous, 263. 
 
 Ilomocercal, 177.* 
 
 Extermination of species, 218, 
 
 iu Cretaceous, 320.* 
 
 Hornblende, 23. 
 
 273, 328, 371. 
 
 in Devonian, 239. 
 
 Hornblende rocks, 35, 37. 
 
 methods of, 385- 
 
 in Mesozoic, 324. 
 
 Horn?tone, 229. 
 
 
 in Paleozoic, 269. 
 
 microscopic remains in. 
 
 Fa^us, 335 * 
 
 in Quaternary, 373. 
 
 234.* 
 
 Fan-palm, 334. 
 
 in Silurian, 215, 224. 
 
 Horse, fossil, 340, 341.* 
 
 Fasciolaria buccinoides, 64,* 
 
 in Tertiary, 344.* 
 
 Hot Springs, 140, 141.* 
 
 317.* 
 
 Triassic, 306. 
 
 Hudson's Bay, 164. 
 
 Faults, 54,* 279 * 
 Favosites Goldfussi, 235.* 
 
 Goosynclinc, 56, 165. 
 Geysers, 140, 141.* 
 
 . idson River shale, 212. 
 Hyaena, species of, 363. 
 
 Niagarensis, 222.* 
 Feldspar, 22, 37. 
 
 Giant's Causeway, 144. 
 Gilbert Islands, 79.* 
 
 Hybodus, species of, 178.* 
 Hydroid Acalephs, 184.* 
 
 Felsyte, 38. 
 
 Glacial period, 347, 348, 360. 
 
 Ilydromica schist, 35. 
 
 Ferns, 187, 188. 
 
 Glacier, great, of Switzerland, 
 
 
 Devonian, 232.* 
 
 117.* 
 
 
 Carboniferous, 251.* 
 Fiords, 351. 
 
 scratches, 350.* 
 theory of the drift, 351. 
 
 Ice of lakes and rivers, 115, 
 116. 
 
 Fishes, 176.* 
 
 Glaciers, 116. 
 
 glacier, 115, 116, 347. 
 
 Age of, 229. 
 
 Glen Roy, benches of, 359. 
 
 Icebergs, 115, 122, 3f>l. 
 
 Carboniferous, 257.* 
 
 Globigerina, 66,* 185,* 186. 
 
 Ichthyornis victor, 321.* 
 
 Devonian, 237.* 
 
 Glyptodon, 866.* 
 
 Ichthyosaurus, 301.* 
 
 Mesozoic, 209,* 318.* 
 
 Gneiss, 35. 
 
 Igneous rocks, 31, 37, 130, 
 
 Silurian, 224. 
 
 Goniatites, first of, 235. 
 
 145,* 171. 
 
 Teliost, 317, 318.* 
 Fish-spines, 239,* 257.* 
 
 last of, in Triassic, 293. 
 Marcellensis, 236.* 
 
 ejections of Lake Superior 
 region, 216. 
 
 Flags, 33, 44. 
 
 Gorgonia, 183.* 
 
 ejections, Triassic, 286. 
 
 Flint, 20, 312. 
 
 Grammysia bisulcata, 236 * 
 
 lguanodon,302, 319. 
 
 Flint arrow-heads, 368. 
 
 Granite, 35, 38. 
 
 Infusorial beds, Tertiary, 336. 
 
 Flow-and-plunge structure, 
 
 Graphite, 25, 69, 146, 200,202. 
 
 Ink-bag, fossil, 298* 
 
 45,* 114. 
 
 Graptolites, 213.* 
 
 Inocerarnus problematicus. 
 
 Fluvio-marine formations, 111. 
 
 Greenland, glaciers of, 121. 
 
 316,* 337. 
 
 Folded rocks, 55* 156, 200, 
 
 changes of level in, 362. 
 
 Insects, 179. 
 
 279.* 
 
 Green Mountains, emergence 
 
 first of, 236. 
 
 Footprints. See TRACKS. 
 
 of, 216. 
 
 Carboniferous, 256.* 
 
 Foraminifera, 65,* 185.* 
 
 limestone of, 211. 
 
 Devonian, 237.* 
 
 Fossilization, 70. 
 
 Green-sand, 311. 
 
 Jurassic, 299.* 
 
 Fossils, use of, in determining 
 
 Gryphsea, 295,* 316.* 
 
 Triassic, 299.* 
 
 the equivalency of stra- 
 
 Guadaloupe, human skeleton 
 
 Irish Deer, 364. 
 
 ta, 3, 60. 
 
 of, 370.* 
 
 Iron ore, Archaean , 200.* 
 
 list of localities of, 399. 
 
 Gulf of Mexico, progress of, 
 
 Iron ores, 28, 85, 86. 
 
 number of species of, 228, 
 
 345. 
 
 Carboniferous, 246, 
 
 383. 
 
 Gulf Stream, 72, 125. 
 
 Isopods, 180.* 
 
 Fragrnental rocks, 29, 33. 
 
 Gymnosperms, 189. 
 
 Itacolumite, 36. 
 
410 
 
 INDEX. 
 
 Jasper, 20. 
 
 Joint* ia rocks, 49,* 169. 
 
 Jurassic period, 285. 
 
 Kaolin, 34, 84, 86. 
 Kerosene, 248. 
 Keuper, 287. 
 
 Keweenaw Point, 211, 216. 
 Kilauea, 14. 
 Kingsmill Islands, 79.* 
 Kirkdale cavern, 363. 
 
 Labradorite, 22, 38, 200. 
 
 Labyrinthodouts, 257,* 300.* 
 
 Laccoliths, 145. 
 
 Lacustrine deposits, 358. 
 
 Lake Champlain in Quater- 
 nary, 358. 
 
 Mempliremagog, Devo- 
 nian coral-reef of, 230. 
 
 Lakes, origin of Great, 272, 
 377. 
 
 Lake-dwellings, 370. 
 
 Lamellibranchs, 181,* 182. 
 
 Laminated structure, 32, 44, 
 45.* 
 
 Lamna clegans, 178,* 338.* 
 
 Lind-slides, 105. 
 
 Lava, 38, 130, 143. 
 
 Layer, 41. 
 
 Lecanocrinus elegans, 214.* 
 
 Leguminosites, 313.* 
 
 Leperditia alta, 224.* 
 
 Lepidodendra, 233. 
 
 Lepidodendron aculeatum, 
 
 251.* 
 priinaevum, 232.* 
 
 Lepidosteus, 177.* 
 
 Leptaena sericea, 214.* 
 transversalis, 222.* 
 
 Leptaenas, last of, 295. 
 
 Lesley, results of denudation 
 96.* 
 
 Leucite, 38. 
 
 Level, change of, in Green- 
 land, 362. 
 
 changes of, in the Quater- 
 nary, 358, 360, 361. 
 origin of changes of. 106, 
 128, 139, 156. 
 
 Level. See ELEVATION. 
 
 Lias, 287. 
 
 Libellula,299.* 
 
 Life, agency of, in rock-mak- 
 ing, 62. 
 
 distribution of marine, 70. 
 general laws of progress of, 
 
 protective and destructive 
 effects of, 80, 81. 
 
 Life. See SPECIES. 
 
 Lignite, 26, 311, 332, 347. 
 
 Lignitic period, 330, 332, 345. 
 
 Limestone, 36, 37. 
 
 formation of, 63, 77, 86, 
 269. 
 
 Limestones of Mississippi Val- 
 ley, 267.* 
 
 Limonite, 28, 85. 
 
 Limulus, 179, 180. 
 
 Lingulse, 68, 181,* 207,* 218, 
 
 382. 
 
 Lingula nags, 207. 
 Liriodendron Meekii, 313* 
 Lithostro t ion (Juiiadense , 255. * 
 Llandeilo flags, 212. 
 Llandovery beds, 221. 
 Localities of fossils, list of, 399. 
 Locusts, 256. 
 London clay, 334. 
 Lorraine shale, 212. 
 Lower Ilelderberg, 220. 
 Ludlow group, 221. 
 Lycopods, 188,223,232,*251 * 
 
 Machaerodus, 364. 
 
 Made, 24. 
 
 Madagascar JEpyornis of, 373. * 
 
 Maguesiau limestone, 27, 36, 
 
 211. 
 
 Magnetite, 29. 
 Magnolia, 334. 
 Mammals, 176. 
 
 Age of, 330. 
 
 first of, 294.* 
 
 Jurassic, 305 * 
 
 Tertiary, 3i9, 338.* 
 
 Triassic, 294,* 305. 
 Mammoth Cave, 103.* 
 Man, Age of, 329, 347, 368. 
 
 fossil, of Guadaloupe. 
 370.* 
 
 the head of the system of 
 
 life, 371, 387. 
 
 Tlap of Pennsylvania coal re- 
 gion, 242.* 
 
 of England, 244.* 
 
 of Ilawaian Is., 17 * 133 * 
 136.* 
 
 of Mammoth Cave, 103.* 
 
 of vicinity of Naples, 398.* 
 
 of N. Jersey Coast, 12.* 
 
 of N. America, Archaean, 
 199.* 
 
 of N. America, Cretace- 
 ous, 320.* 
 
 of N. America, Tertiary, 
 344.* 
 
 of New York and Canada, 
 197.* 
 
 of Ocean, 11.* 
 
 of United States, 195.* 
 
 of World, 8* 
 Marble, 37. 
 
 of Green Mountains, 211, 
 
 217. 
 
 Marcellus shale, 230. 
 Margarita Nebrascensis, 64.* 
 Marine formations, 112. 
 Marl, 76, 311. 
 Marsupials, 176, 366. 
 
 Triassic, 294,* 305.* 
 
 Jurassic, 305.* 
 
 Massive structure, 32, 44, 45.* 
 Mastodon, Quaternary, 364.* 
 
 Tertiary, 343. 
 Mastodonsaurus, 300.* 
 Mauna. Sec MOUNT. 
 May-flies, 256.* 
 Medina group, 219, 223. 
 
 Medusae, 183,* 184. 
 Megacerod Hiberuicus, 364. 
 Mega.lo.iaur, 302. 
 Megatuere, 3u5.* 
 MeUphyre, 38. 
 Mer-dc-glace, 117. 
 Mesozoic time, 283. 
 
 general observations on, 
 324. 
 
 geography of, 324. 
 
 life of, 326. 
 
 Metauiorpliic rocks, 30, 35, 37. 
 
 Mefcamorphism, nature and 
 
 cause of, 128, 145, LJV, 
 
 168. 
 
 Miamia Bronsoni, 256.* 
 Mica, 22. 
 Mica-schist, 35 
 Michigan coal -area, 241. 
 Microdon bellistriatus, 236.* 
 Microiites, 39. 
 
 Microscopic organisms, 66,* 
 67,* 68,* 187, 234,* 
 
 235.* 
 
 Millepores, 184. 
 Mineral coal. See COAL. 
 
 oil, 26, 248. 
 Miocene, 330. 
 
 Mississippi River, amount of 
 water of, 91. 
 
 delta, of, 101.* 
 
 detritus of, 99. 
 Moa, extinction of, 372. 
 Mollusks, 175, 180, 181.* 
 Monadnock,349. 
 Monocline, 56. 
 Moraines, 119. 
 Mosasaur, 318,* 319.* 
 Mountains, making of, 159. 
 163, 165, 216, 345. 
 
 of Paleozoic origin, 271. 
 
 made after the close of tue 
 Paleozoic, 277. 
 
 made after the Jurassic, 
 309. 
 
 made during the Tertiary, 
 344. 
 
 See ELEVATIONS. 
 Mount Blanc, 117. 
 
 Holyoke, 144, 286. 
 
 Loa, 133,* 136* 138. 
 
 Tom, 144. 
 
 Vesuvius, 130 * 138, 398. 
 Muck, 76. 
 Mud-cones, 142. 
 Mud-cracks, 46. 
 Muschelkalk, 287. 
 Muscovite, 3. 
 Myriapods, 179, 256. 
 Naples, map of vicinity, 398.* 
 Nautilus, 181,* 218, 382. 
 
 in the Silurian, 215. 
 Nautilus tribe, number of ex- 
 tinct species of, 383 
 Neolithic era, 369. 
 N(Sv<, 116. 
 
 New Brunswick coal-area, 241. 
 New Caledonia reefs, 80. 
 New South Wales cliff, 107.* 
 Niagara Falls, rocks of, 40,* 
 
INDEX. 
 
 411 
 
 Niagara Falls group, 219. 
 
 River, gorge of, <J4, 375. 
 Noeggerathia. See CYCLOP- 
 
 TEBIS. 
 
 North America, form of, 14. 
 geography of. See GEOG- 
 RAPHY. 
 
 Norwich crag, 334. 
 Notidauus priinigenius, 178.* 
 Nototherium, 366. 
 Nova Scotia coal-area, 241. 
 Nullipores, 66, 187. 
 Nuummlltes, 66,* 333.* 
 Nummulitic limestone, 333. 
 Nuts, fossil, 251,* 253, 334.* 
 
 Oak, 334. 
 
 Obsidian, 39. 
 
 Ocean, depression of, 9, 12.* 
 
 effects of, 106. 
 
 Oceanic basin, 6,11,* 70, 156. 
 Ochre, yellow, 28, 82. 
 Ohio, coral-reef of Falls of, 
 
 230. 
 
 Oil, mineral, 26, 248 
 Old red sandstone, 231. 
 Olivine, 38. 
 
 Oiieida conglomerate, 219. 
 Onondaga limestone, 229. 
 Oolitic structure, 47. 
 Oolyte, 37, 287. 
 Orbitolina Texana, 315.* 
 Oreodoa gracilis, 343.* 
 Orient, charactcriotics of, 6. 
 Origin of species, 392. 
 Oriskany period, 205, 21U, 221. 
 Orohippus, 340, 341.* 
 Orthis occidentals, 214.* 
 
 testudiuaria, 214.* 
 
 varica, 222 * 
 Orthoceras junceum, 214.* 
 
 last of, 296, 326. 
 Orthoclase, 22. 
 
 Osmeroides Lewesiensis, 318.* 
 Ostracoids, 180.* 
 
 of Triassic, 290- * 
 Ostrea sellseformis, 336.* 
 Otozoum Moodii, 292.* 
 Outcrop, 52.* 
 Ox, first of, 344. 
 Oyster, Tertiary, 337. 
 
 Paleaster Niagarensis, 183.* 
 Palaeoniscus lepidurus, 177.* 
 
 Freieslebeni, 177,* 257.* 
 Paleolithic era, 368. 
 Paleothere, 339. 
 Paleozoic time, 204. 
 
 disturbances closing, 276. 
 
 general observations on, 
 
 266. 
 
 Palephemera mediaeva, 291.* 
 Palisades, 286. 
 Palms, first of, 312. 
 
 Tertiary, 335.* 
 Palpi pes priscus, 299.* 
 Paludina Fluviorum, 295.* 
 Paradoxides Harlani, 208 * 
 Paris basin, Tertiary animals 
 
 of, 339. 
 Paumotu Archipelago, 79. 
 
 Pearlstone, 39. 
 Peat, formation of, 75. 
 Peccary, fossil, 342. 
 Pecopteris btuttgartensis. 
 
 289.* 
 
 Pemphix Sueurii, 299.* 
 Pentacrinus Wyville-Thom- 
 
 soni, 65.* 
 Pentamerus galeatus, 224. * 
 
 oblougus, 22^.* 
 Pentremites, 254, 255.* 
 Peridotyte, 38, 39. 
 Permian period, 241, 249. 
 Petraia corniculum, 214.* 
 Petroleum, 248. 
 Petrology, 19, 20. 
 Phacops bufo, 236.* 
 Phascolotherium, 305.* 
 Phenogams, 187, 188. 
 Phyllyte, 36, 
 
 Physiographic Geology, 6. 
 Pictured rocks, 211. 
 Pitchstone, 39. 
 Plants, 67, 80, 173, 186. 
 
 Carboniferous, 249,* 250.* 
 
 Cretaceous, 312.* 
 
 earliest marine, 202, 207. 
 
 Devonian, 232.* 
 
 Silurian, 228. 
 
 Tertiary, 335.* 
 
 Triassic, 288,* 289. 
 Platephemera antiqua, 237.* 
 Platyceras augulatum, 222.* 
 Plcsiosaurs, 301,* 302, 319. 
 Plourotomaria tabulata, 255.* 
 Pliocene, 330. 
 Pliosaur, 302. 
 Plumbago, 25. 
 
 Podozamites lanceolatus, 289.* 
 Polycystines, 186. 
 Polyps, 184.* 
 Polythalamia. See FORAMI- 
 
 NIFERA. 
 
 Pompeii, 139, 398. 
 Porphyritic rocks, 32, 38. 
 Portland (England) dirt-bed, 
 
 (Connecticut) freestone, 
 
 285. 
 
 Potsdam sandstone, 206. 
 Primordial period, 206. 
 Prionastraea oblonga, 294.* 
 Productus Nebrascensis, 255 * 
 Protozoans, 175, 185,* 313. 
 Pterichthys, 237.* 
 Pterinea emacerata, 222.* 
 Pterodactyl, 303,* 319. 
 Pterophyllum, 289.* 
 Pteropods, 182.* 
 Pterosaurs, 303,* 319, 
 Ptilodictya, 214.* 
 Pudding-stone, 34. 
 Pumice, 39, 131 
 Pupa vetusta, 255.* 
 Pyrifusus, 64,* 317.* 
 Pyrite, 29, 82. 
 Pyroxene, 23. 
 Pyrrhotite, 29, 82. 
 
 Quadrupeds. See MAMMALS. 
 Quaquaversal structure, 45.* 
 
 Quartz, 20.* 
 
 Quartz rock, or Quartzyte, 36. 
 Quaternary, 329, 347, 367. 
 Quebec group, 211. 
 Quercus, Tertiary, 335.* 
 
 Radiates, 175, 183.* 
 Radiolarians, 67,* 186.* 
 Rain-prints, 47,* 306, 
 Rauiceps Lyellii, 258.' * 
 Raphistoma lenticularis, 214. * 
 Rays, 178. 
 
 Reefs, coral, 77, 78.* ' 
 Re-gelation, 119. 
 Reindeer era, 361, 368. 
 Reptiles, 176 
 
 Mesozoic, 291, 292 * 300 * 
 318,* 328. 
 
 Paleozoic, 258.* 
 Reptilian age, 284. 
 Rhabdoliths, 66, 187. 
 Rhinoceroses, Tertiary, 342.* 
 
 Quaternary, 364. 
 Rhizopods, 65,* 67,* 185.* 
 
 Cretaceous, 313, 
 
 formation of deposits by, 
 
 65, 67 
 
 Rhode Island coal-area, 241. 
 Rhynchonella pyramidatum, 
 
 Rhynchotreta cuneata, 222.* 
 Rill-marks, 46 * 114. 
 Ripple-marks, 46,* 114 
 Rivers, action of, 90 
 
 of Paleozoic origin, 272. 
 River terraces, 357,* 360* 
 Roches moutonne"es, 120, 121.* 
 Rock, definition of, 19. 
 Rocks, constituents of, 20. 
 
 formation of sedimentary, 
 90, 100, 111, 112, 122 
 
 fragmented, 29. 
 
 kinds of, 29. 
 
 metainorphic, 35, 145. 
 
 of Mississippi Valley, sec- 
 tion of, 267.* 
 
 origin of Archaean, 201. 
 
 origin of Paleozoic, 268. 
 
 thickness of Paleozoic in 
 North America, 267, 
 
 377. 
 
 Rocky Mountains, origin of, 
 164, 170, 345. 
 
 Mountain coal-area, 382. 
 Rotalia, 6,* 186.* 
 
 Sabal, 334. 
 
 St. Lawrence River in the Qua- 
 ternary, 358. 
 
 St. Peter's sandstone, 211. 
 Saliferous group of Britain 
 and Europe, 287. 
 
 rocks of New York, 220. 
 Salina rocks, 220, 226. 
 Salisbury Craigs, 144. 
 Salix Meekii, 313 * 
 Salt, 28. 
 
 of coal formation, 248. 
 
 of Salina, etc., 220. 
 
 of Triassic, 287. 
 Sand, 33, 86. 
 
412 
 
 INDEX. 
 
 Sand-banks, 112. 
 Sand-scratches, 88. 
 Sandstone, 84, 36. 
 Sapphire, 21. 
 
 Sassafras (Jretaceum, 313.* 
 Sauropus primsevus, 258.* 
 Scaphites larvaeformis, 817 * 
 Schist, schistose rocks, 32, 35. 
 Schoharie grit, 229. 
 Scolithus linearis, 208. 
 Scoria, 39, 131. 
 Scorpions, first of, 256.* 
 Sea-beaches elevated, 358. 
 Sea-weeds, 187. 
 
 Section of New York rocks, 
 198.* 
 
 of the series of rocks, 193 * 
 Sections of Paleozoic rocks, 
 
 231,* 267,* 2i~9.* 
 Sedimentary beds, formation 
 
 of, SO, 100, 111, 112, 122. 
 Selachians, 178.* 
 
 Carboniferous, 256.* 
 
 Devonian, 239,* 
 Serolis, 180* 
 Serpentine, 23. 
 Shale, 32, C3, 34, 44.* 
 Sharks, 178, 256.* 
 
 Devonian. 239.* 
 
 Teeth, 178,* 299, 338.* 
 Shasta, height of. 133. 
 Siderite, 29, 85. 
 SigillariaHallii,232.* 
 
 Carboniferous, 252.* 
 Silica, or Quartz, 20. 
 Silicates, 20, 21. 
 Siliceous rocks, 32 
 
 shells, microscopic, 66, 
 67,* 68,* 185* 180,* 
 187,* 234,* 312, 335.* 
 
 waters of Geysers, 142. 
 Silt, 94, 99, 100. 
 Silurian age. 205. 
 
 Upper, 219. 
 Siphonia lobata, 315.* 
 Slate, 32, 33, 36- 
 Slaty cleavage, 32, 49,* 156, 
 
 169, 
 
 Sloths, gigantic, of Quater- 
 nary, 366.* 
 Snakes, first of, 338. 
 Soapstone, 23. 
 
 Solenhofcn lithographic lime- 
 stone. 287. 
 Solfataras, 140. 
 Solitaire, 372.* 
 South America, form of, 14. 
 
 changes of level in, 361. 
 Spathic iron, 29. 
 Species , exterminations of, 218, 
 
 Sphagnous mosses, 75. 
 Sphenopteris Gravenhorstii 
 
 251.* 
 Spicules of Sponges, 67,* 185, 
 
 234,* 314.* 
 Spiders, 179, 256.* 
 Spinax Blainvillii, 178.* 
 Spirifer cameratus, 255.* 
 macropleurus, 224.* 
 mucrouatus, 236.* 
 
 Spirifer striatus, 63.* 
 
 Tracks of insects, 291.* 
 
 Hcitcotti, 295.* 
 
 of reptiles, Carboniferous, 
 
 Spirilers, last of, 326. 
 
 258.* 
 
 sponges, 67* 185, 314.* 
 
 of reptiles, Triassic, 292. * 
 
 Cretaceous, 315.* 
 
 of Trilobites, 208.* 
 
 Sponge-opicules, 67.* 
 
 Transportation by rivers, 98. 
 
 in hornstone, 234.* 
 
 Trap, 38. 
 
 Spores in coal, 259.* 
 
 of Connecticut Valley, 
 
 stalactites, 37. 
 
 etc., 286. 
 
 Stalagmite, 37. 
 
 columnar, 145.* 
 
 Star-fishes, 184.* 
 
 Travertine, 32, 37, 142. 
 
 Statuary marble, 37. 
 
 Tree-ferns, 251. 
 
 Staurolite, 25. 
 
 Trenton period, 210. 
 
 Steatite, 23. 
 
 Triassic period, 285. 
 
 Stictopora acuta, 214.* 
 
 Trigonia clavellata, 295.* 
 
 Stigmarise, 251,* 252. 
 Strata, definition of, 39, 41. 
 
 Trigonocarpus tricuspidatus, 
 
 251.* 
 
 positions of, 50, 51 * 53* 
 
 Trilobites, 180,* 207, 208,* 
 
 58. 
 
 214,* 222,* 236*275. 
 
 3traticulate structure, 44. 
 
 beginning and ending of 
 
 Stratification, 39, 40,* 44.* 
 
 fnera, 273.* 
 
 Strike, 54.* 
 
 ,131. 
 
 Strophomena rhomboidalis, 
 
 Turrilitcs catenatus, 317.* 
 
 222. 
 
 Turritella carinata,.33G.* 
 
 Subcarboniferous period, 240, 
 
 Turtles, Cretaceous, 319. 
 
 245- 
 
 Jurassic, 303. 
 
 'Submarine eruptions, 139. 
 
 Tertiary, 338. 
 
 Subsidence of coast of New 
 
 
 Jersey, 362. 
 of Greenland, recent, 362. 
 Subsidences of volcanic re- 
 
 Unconformable strata, 57.* 
 Under -clays, 246. 
 Unstratified condition, 41.* 
 
 gions, 139. 
 Subterranean waters, 102. 
 Sweden, Quaternary of, 359. 
 changes of level in, 362. 
 Syenyte, 35, 37. 
 
 Upper Helderberg, 229. 
 Upper Silurian, 219. 
 Ursus spelseus, 363. 
 Utica shale, 211. 
 
 Syncline, 56.* 
 Synclinorc, 167. 
 Syringopora Maclurii, 235.* 
 System, definition of, 41. 
 
 Valleys, formation of, 91. 
 Veins, 41,* 129, 150. 
 Vertebrate-tailed fiehes, 177,* 
 238* 
 
 
 Vertebrates, 175, 176. 
 
 Talc, 23. 
 Talcose slate, 35. 
 
 first of, 224. 
 
 T7V*oTiT7ino 1QA =' ; 1^?R QQQ 
 
 Tapirus Indicus, 339.* 
 Teliost fishes, 176.* 
 Cretaceous, 317,318,*328. 
 
 Vesuvius, J.oJ," 100,0*70. 
 Viviparus fluviorum, 295.* 
 Volcanoes, 130. 
 
 Tertiary, 337. 
 Tentaculites, 223, 224.* 
 Terebratula, 63,* 181.* 
 
 Waldheimia, 63.* 
 Water, action of, 90. 
 
 Terebratulina, 63.* 
 Terraces on Connecticut River, 
 
 freezing and frozen, 115. 
 Waves, action of, 107. 
 
 357.* 
 of Scotland, 359. 
 origin of, 100, 355, 359. 
 
 Wealden, 287. 
 Wenlock limestone, 221. 
 Whales, first of, 338. 
 
 Tertiary age, 330. 
 Tetradecapods, 179.* 
 
 Winds, effects of, 86, 110. 
 Wind-drift structure, 45,* 88 
 
 Tetragonolcpis, 299.* 
 
 Woolwich beds, 334. 
 
 Thanct sands, 334. 
 Thecodonts, 259. 
 
 Worms, 179, 180,* 208. 
 
 Thrissops, 177.* 
 Tidal currents, 108. 
 Tiger, 343. 
 
 Xiphacantha, 186.* 
 Xiphodon gracile, 340 * 
 
 Time, length of geological, 
 
 Yoldia limatula, 337.* 
 
 375. 
 Time-ratios, 269, 324, 375. 
 
 Yorktown period, 331. 
 
 Titanothere, 342.* 
 
 
 Tourmaline, 24.* 
 
 Zamia,189,288.* 
 
 Trachyte, 38, 39, 14a 
 Trachytic hills, 138. 
 Tracks of Birds, 203.* 
 
 Zaphrentis bilateralis, 222.* 
 Rafinesquii, 235.* 
 Zeacrinus elegans, 256.* 
 
 of^Cheirotherium, 300.* 
 
 Zeuglodon, 340. 
 
 of 
 
PUBLICATIONS OF THE AMERICAN BOOK COMPANY. 
 
 Chemistry. 
 
 Brewster's First Book of Chemistry. 
 
 By MARY-SHAW BREWSTER 66 cents. 
 
 A course of experiments of the most elementary character for the guidance of chil- 
 dren in the simplest preliminary chemical operations. The simplest apparatus is em- 
 ployed. 
 
 Clarke's Elements of Chemistry. 
 
 By F. W. CLARKE $1.20. 
 
 A class-book intended to serve not only as a complete course for pupils studying 
 chemistry merely as part of a general education, but also as a scientific basis for sub- 
 sequent higher study. 
 
 Cooley's New Elementary Chemistry for Begin- 
 ners. 
 
 By LE ROY C. COOLEY 72 cents. 
 
 This is emphatically a book of experimental chemistry. Facts and principles are 
 derived from experiments, and are clearly stated in their order. 
 
 Cooley's New Text-Book of Chemistry. 
 
 By LE ROY C. COOLEY 90 cents. 
 
 A text-book of chemistry for use in high schools and academies. 
 
 Eliot and Storer's Elementary Chemistry. 
 
 Abridged from Eliot and Storer's Manual, by WILLIAM RIPLEY 
 
 NICHOLS, with the co-operation of the authors $1.08. 
 
 Adapted for use in high schools, normal schools, and colleges. 
 
 Steele's New Popular Chemistry. 
 
 By J. DORMAN STEELE, Ph. D $1.00. 
 
 Devoted to principles and practical applications. Not a work of reference, but a 
 pleasant study. Only the main facts and principles of the science are given. 
 
 Stoddard's Qualitative Analysis. 
 
 By JOHN T. STODDARD, Ph. D 75 cents. 
 
 An outline of qualitative analysis for beginners. The student is expected to make 
 the reactions and express them in written equations. 
 
 Stoddard's Lecture Notes on General Chemistry. 
 
 Part I. Non-Metals $0.75. 
 
 Part II. Metals. . i.oo. 
 
 Designed as a basis of notes to be taken on a first course of experimental lectures 
 on general chemistry, to relieve the student from the most irksome part of his note- 
 taking. 
 
 Youmans's Class-Book of Chemistry. 
 
 By EDWARD L. YOUMANS, M. D. Third edition. Revised and 
 
 partly rewritten by WILLIAM J. YOUMANS, M. D $1.22. 
 
 Designed as a popular introduction to the study of the science for schools, colleges, 
 and general reading. With a colored frontispiece and 158 illustrations. 
 
 Copies mailed, post-paid, on receipt of price. Full price-list sent on application. 
 
 AMERICAN BOOK COMPANY, 
 
 NEW YORK .: CINCINNATI : CHICAGO. 
 
 1*68] 
 
PUBLICATIONS OF THE AMERICAN BOOK COMPANY. 
 
 Zoology and Natural History. 
 
 Cooper's Animal Life. 
 
 By SARAH COOPER $1.25. 
 
 Animal life in the sea and on the land. A zoology for young people. Especial at- 
 tention has been given to the structure of animals, and to the wonderful adaptation of 
 this structure to their habits of life. 
 
 Holder's Elementary Zoology. 
 
 By C. F. HOLDER $1.20. 
 
 A text-book designed to present in concise language the life-histories of the groups 
 that constitute the animal kingdom, giving special prominence to distinctive character- 
 istics and habits. 
 
 Hooker's Child's Book of Nature. 
 
 Part II. Animals. By WORTHINGTON HOOKER, M. D. $0.44. 
 
 While this work is well suited as a class-book for schools, its fresh and simple style 
 can not fail to render it a great favorite for family reading. 
 
 Hooker's Natural History. 
 
 By WORTHINGTON HOOKER, M. D $0.90. 
 
 For the use of schools and families. Illustrated by three hundred engravings. The 
 book includes only that which every well-informed person ought to know, and excludes 
 all which is of interest only to those who intend to be thorough zoologists. 
 
 Morse's First Book in Zoology. 
 
 By E. S. MORSE, Ph. D $0.87. 
 
 Prepared for the use of pupils who wish to gain a general knowledge concerning 
 the common animals of the country. The examples presented for study are such as 
 are common and familiar to every school-boy. 
 
 Nicholson's Text-Book of Zoology. 
 
 By H. A. NICHOLSON, M. D $1.38. 
 
 Revised edition. A work strictly elementary, designed for junior students. Illus- 
 trated with numerous engravings. It contains an Appendix, Glossary, and Index. 
 
 Steele's New Popular Zoology. 
 
 ByJ. DORMAN STEELE, Ph.D $1.20. 
 
 This book proceeds, by natural development, from the lowest form of organism to 
 man. A cut is given of every animal named, since a good picture of an object is worth 
 more than pages of description. 
 
 Tenney's Elements of Zoology. 
 
 By SANBORN TENNEY, A. M $1.60. 
 
 Illustrated by seven hundred and fifty wood engravings. It gives an outline of the 
 animal kingdom, and presents the elementary facts and principles of zoology. 
 
 Tenney's Natural History of Animals. 
 
 By SANBORN TENNEY and ABBY A. TENNEY. . . . $1.20. 
 
 A brief account of the animal kingdom, for the use of parents and teachers. Illus- 
 trated by five hundred wood engravings, chiefly of North American animals. 
 
 Copies mailed, post-paid, on receipt of price. Complete price-list sent on applica- 
 
 AMERICAN BOOK COMPANY, 
 
 NEW YORK : CINCINNATI :- CHICAGO. 
 
 [* 7 i] 
 
THIS BOOK IS DUE ON THE LAST DATE 
 STAMPED BELOW 
 
 AN INITIAL FINE OF 25 CENTS 
 
 WILL BE ASSESSED FOR FAILURE TO RETURN 
 THIS BOOK ON THE DATE DUE. THE PENALTY 
 WILL INCREASE TO 5O CENTS ON THE FOURTH 
 DAY AND TO $1.OO ON THE SEVENTH DAY 
 OVERDUE. 
 
 
 ' :'. 
 
 !S9 
 
 LD 21-50m-8,-32 
 
16765 
 
 
 13