THE GEOLOGICAL" STORY JAA\ES D. DANA or ^ oo THE GEOLOGICAL STOKY BRIEFLY TOLD BY JAMES i>. DANA "F (,KiPI.(MiV, "TEXT-BOOK OF G CORAL ISLANDS," WORKS OS MINERALOGY, ETC. AUTHOR OF A M A M A I. OF (iEol.oiir, " TF.XT-BOOK OF GEOLOGY, "CORALS XE W YORK : CINCINNATI : CHICAGO AMERICAN BOOK COMPANY Coi-YFK.in. 1 >!?>, KV AMERICAN BOOK COMPANY. GEOL. STOUY. PREFATORY SUGGESTIONS. EOLOGY is eminently an out-door science; for strata, rivers, ^~"^ oceans, mountains, valleys, volcanoes, cannot be taken into a recitation room. Sketches and sections serve a good purpose in illus- trating the objects of which the science treats, but they do not set aside the necessity of seeing the objects themselves. The reader who has any interest in the subject should therefore go for aid in his study to the quarries, bluffs, or ledges of rocks in his vicinity, and all places that illustrate geological operations. At each locality accessi- ble to him he should observe the kinds of rocks that there occur ; whether they consist of layers or not ; and their positions, whether the layers are horizontal, the position they had when made ; or whether inclined, a slope in the beds being evidence of a subterranean movement like that which takes place in mountain-making. Geology teaches that much the larger part of the rocks that con- sist of layers were made through the action of water ; and if such rocks are accessible, it is well, after learning the lessons of the book, to look among them for evidence of this mode of origin, either in the structure of the layers, in the nature of the material, in markings within the beds, or in the presence of relics of aquatic life, such as shells, bones, etc. If some of the layers in a bluff consist of sand- stone, others are pebbly, others clayey, and one or more are of 4 PREFATORY SUGGESTIONS. limestone, the kinds of changes in the waters that took place to produce such varied results should be made a point for investigation. If an excavation for a cellar is opened near an accustomed walk, it is best to look at the sections of the earth or sands thus made ; for these sands are very often in layers, and, in that case, they bear evidence that even there the loose material of the surface had been arranged by water, either that of the ocean or that of a river or lake. When the layers contain fossils, a collection should be made for study ; for they show what living species populated the waters or land when the rocks were forming; and in the height of a single bluff there may be records thus made of several successive popula- tions different from one another. If a beach or a cliff along the ocean is accessible, the action of the waves in their successive plunges may be watched to great ad- vantage ; for they are thus grinding up the stones and sands of the beuch and eroding and undermining the cliff. While viewing such work on a seashore, it will be a good time to consider that this but- tering goes on almost incessantly through the year, and year after year, and has so gone on along coasts and about reefs for indefinite ages. The cliff and the rocky ledges in the surf at its base should be closely examined, that the amount and kind of wear may lie appre- ciated ; and the action of the water over the beach should be studied in' order to understand why, after so much grinding, coarse sands and often pebbles are still left. If there are sand-flats exposed off the shores at low tide, there is a chance to discover by what currents or movements of the water they were formed, and whence came the sands thai compose them, which should be taken advantage of ; for these modern sand-flats are PKEFATOKV SUGGESTIONS. 5 identical in kind and mode of origin, although not in extent, with the sand-flats of ancient time out of which sandstones have been made ; the only possible difference being that in the earlier ages the waters were everywhere salt, and rivers gave little aid. And if the sandy surface is left rippled as the tide goes out, note this, for ancient sandstones often contain such ripple-marks over their layers ; or if the muddy portions are marked with the tracks of Mollusks, note this also, for in many rocks just such tracks occur. If coral reefs or shell rocks are forming along the shores, as in the West Indies, these formations should receive .special study; for many of the old limestones of the world were made in the same way. If a heavy rain has gullied a side-hill or proved disastrous to roads, nere is a fruitful field for study ; for the gullies are minia- ture valleys, and they illustrate how most great valleys were ex- cavated. the latter being as truly the work of running water as the former. The same gullied slope may exemplify also the for- mation of precipices and waterfalls, of crested ridges, table-topped summits, and groups or ranges of mountain peaks. These are some of the points of easy observation. Many others will occur to the reader after a perusal of the following pages. A few labeled specimens of minerals and rocks are absolutely indispensable for even a partial understanding of the subject, and the student should buy or beg them, if not able to do the better thing to collect them himself. Of MINERALS: 1, crystallized quartz; 2, two or three quart 7. pebbles of different colors ; l>, the variety of quartz called hornstone or m'nt ; 4, com- mon feldspar ; o, mica ; (i, black hornblende ; 7, a black or greenish-black crystal of augite, and better if in a volcanic rock ; 8, garnet ; 9, tourma- line; 10, ealcite (carbonate of lime), a cleavable specimen; 11, dolomite, or 6 PREFATORY SUGGESTIONS. magnesian carbonate of lime; 12. gypsum, or sulphate of lime; !">, pyrite (sulphide of iron) ; 14, magnetite, or magnetic iron ore; 15, hematite, or specular iron ore ; 16, limonite, the common iron ore often called " brown hematite"; 17, siderite, or spathic iron ore; 18, chalcopyrite, or yellow cop- per ore ; 11), galenite, or lead ore (sulphide of lead) ; 20, graphite. Of ROCKS : 1, 2, 3, common compact limestone of three different colors, one, at least, of these specimens with a fossil in it ; 4, chalk, a variety of compact limestone; 5, (5, white and clouded granular or crystalline lime- stone, of which the ordinary architectural marble is an example; 7, 8, red and gray sandstone; 9, conglomerate, called also pudding-stone; 10, shale, such as the slaty rock of the coal-formation, and other shales of the Silu- rian and Devonian; 11, slate, or argillyte, that is, common roofing-slate, or writing-slate; 12, 13, coarse and fine-grained grayish or reddish granite (to be obtained, like marbles and sandstones, in many stone-yards) ; 14, red or gray quartz-syenyte, of which the Scotch "granite" and Quincy "granite" are good examples; 15, gneiss, a piece that has the mica distinctly in planes, and hence is banded on a surface of transverse fracture ; l(i, mica schist ; 17, trap, an igneous rock; 18, trachyte, an igneous rock; 1!), lava, a cel- lular volcanic rock; 20, a piece of diatomaceous or infusorial earth. The above-mentioned minerals should at least be accessible to a class, if not in the hands of each student ; and it would be well if the collection were larger. Moreover, the instructor, if not a prac- tical geologist, should have by him the writer's Manual of Geology, or some other large work on the science, in order to be ready to answer the questions of inquisitive learners, and add to the exam- ples and explanations. The student should possess a hammer and a chisel. The best hammer has the face square, flat, sharp-angled, and the opposite end brought to an edge; this edge should have the same direction with the handle (as in the figure), if it is to be used for getting out rock-specimens, but be transverse to this, and thinner, if for obtaining fossils. The socket for the handle should be large, in PREFATORY SUGGESTIONS. 9 order that the handle may stand hard work. The chisel should be a stone-chisel, six inches long. Rock-specimens should be uniform in size, with straight sides ; say two inches by three, or three inches by four. Fossils had better be separated from the rock if it can be done safely. For measuring the dip, that is, the slope, of layers, an instrument called a clinometer is used, which can be had of the instru- ment makers. It is a compass having a pendulum hung at the center, the extrem- ity of which swings over a graduated arc. Tn the best kind the compass is three inches in diameter and has a square base. A clinometer apart from the compass may be easily extemporized by taking (see figure) a piece of board, al>c<1, cut to an exact square (three or four inches each side), hanging a pendulum on a pivot near one angle (n), describing on the board, with one leg of the dividers on the pendulum-pivot, an are of 90 (1> to c), and then dividing this arc into nine equal parts, each to mark 10, and sub- dividing these parts into degrees. Such a clinometer, well-gradu- ated, is sufficiently accurate for good work. Field work of the kind above pointed out makes the facts in the science real. It also teaches with emphasis the great lesson that ex- isting forces and operations are in kind the same that have formed the rocks, the valleys, and the mountains. It thus prepares the mind to appreciate geological reasoning and comprehend the inarch of events in the earth's history. FEW HAVEN, CONX., April 1, 1895. CONTENTS. PAfiK (iEOLOGY 11 TAUT I. ROCKS OR WHAT THE EARTH IS MADE OF ... 13-38 I. MINERALS 10 Consisting of Silica 10 Silicates 19 Carbonates 23 Sulphates 25 Ores 25 TI. KINUS 01- ROCKS 29 III. STRICTI-RE OF ROCKS 35 TAUT II. GEOLOGICAL CAUSES AND EFFECTS 39-121 I. MAKING OF ROCKS 39 Contributions of Plants and Animals 43 Chemical Work of Air and Moisture 58 Work of Winds 01 Work of Fresh Waters 03 Work of the Ocean 09 Work of Ice 78 Work of Heat 84 Solidification and Metainorphism 92 Veins and Ore Deposits 90 9 10 CONTENTS PAGK II. MAKING OF YAU.KYS 101 By Erosion 101 By Upheaval of Mountains 104 By Fractures of the Earth's Crust 104 III. MAKING OF MOUNTAINS ANI> ATTENDANT EFFECTS . . . 105 By Igneous Ejections 105 By Erosion of Elevated Lands 100 By Upturnings, Flexures, etc 108 PART III. HISTORICAL GEOLOGY 122-292 SUBJECTS AND SUBDIVISION* 122 Classification of the Animal Kingdom 125 I. ARCILKAN TIME 1:17 II. PALEOZOIC TIME 144 Cambrian Era 145 Lower Silurian Era 15:5 Upper Silurian Era U>4 Devonian Era 170 Carbonic Era 184 Post-Paleozoic devolution 202 III. MESOZOIC TIME 209 Triassic and Jurassic Periods 209 Cretaceous Period 226 Post-Mesozoic Revolution 285 IV. CENOZOIC TIME 2:57 Tertiary Era 287 Quaternary Era 249 V. OBSERVATIONS ON GEOLOGICAL HISTORY 280 Length of Geological Time 280 Progress in Development of the Earth's Features . . . 282 Beginning and End of the Earth 288 Progress in Life 284 GEOLOGY. E word Geoloiju is from two Greek words signifying flu> start/ of the earth. As used in science it means an account of tlie rocks which lie beneath the surface and stand out in its ledges and mountains, and of the loose sands and soil which cover them ; and also an account of what the rocks are able to tell about the world's early history. By a careful study of the nature and positions of rocks, and the markings or relics they contain, it has been discovered how the rocks themselves were made; and also how the mountains and the continents, with all their variety of surface, were gradually formed. And, further, it has been ascertained not only that the earth had plants and animals long before Man appeared, but what were the kinds that existed in succession through the long ages. The subjects, therefore, of which geology treats are: I. The KIXDS OF ROCKS. II. The ways in which the rocks, valleys, mountains, and continents were made, or GEOLOGICAL CAUSES, AND THEIR EFFECTS. 11 12 III. The events during the successive periods in thp earth's history; that is, what making of rocks Avas going on in each period, what making of mountains and valleys, and what species were living in the waters and over the land in each, and how the world of the past differs from the world as it now is, all of which subjects, and others related, are treated under the general head of HISTOIUCAL GEOLOGY. PART T. ROCKS, OR WHAT THE EARTH IS MADE OF. ROCKS consist of minerals ; the ores and gems they contain are some of the minerals; and throughout the earth, to its center, the solid rocks have a crystalline structure. The most abundant element in minerals and in the earth's constitution is Osi/ycii. It makes part of the atmosphere, is one of the two constituents of water, and is an essential part of all rock-making minerals. Owing to its strong attractions for other elements, iron rusts, that is, becomes oxidized ; and most iron-bearing minerals in the rocks oxi- dize, wherever exposed to air and moisture. This oxida- tion produces the decay of the rocks, and promotes the conversion of them into gravel, sand, and soil. Of next importance in the constitution of rocks is Sili<-<>n (named from the Latin for Jlitif). All the rocks excepting limestones contain silicon in combination with oxygen, and also usually other elements. 13 14 CONSTITUTION OF ROCKS. Xext comes Carbon (named from the Latin for coal). It is the chief ingredient of coal and one of the constituents of limestone and of mineral oil and gas. It is a chief constituent also of all animal and vegetable tissues. In its pure crystallized state it is diamond, the hardest of all minerals, and also graphite or plmnbafjo (the material of lead pencils), which is among the softest of minerals. Aluminum (so named from the Latin for clay), combined with oxygen and other elements, is a chief constituent of clay, and also of very many of the rocks and hard minerals. Calcium (from the Latin for lime) is a chief constituent of limestone. Magnesium, potassium, sodium, are other common elements of rocks. Sulphur occurs pure in nature, especially in volcanic regions. It is a constituent of many ores, and also of gypsum among rock-making materials. Arsenic is an ingredient of many ores, but not of any rock. Hydrofjen (named from the Greek for ir, without the animal ; it shows the radiating plates in the cup-shaped cavity at the top. Still another, somewhat larger, ellipti- cal in shape instead of cylindrical, and in the living state, is presented in Fig. 16. The mouth is a very long one, and the arms or tentacles which serve to push in the prey it captures are Thecocyathus cylindraceus. 46 MAKING OF KOCKS. also long. It owes much of its power of capturing to the stinging qualities of these tentacles. The arrangement of the tentacles of a polyp around a center, and also that of the plates inside of the coral cup, is radiate; and hence Polyps, like some other kinds of life, are often called Radiate, animals. FIG. 16. Flabellum pavoninum. 3. Crinoids. Crinoids also are flower-like animals. They were once exceedingly abundant in the seas of the world, but now are rarely found. Two of the kinds are rep- resented in Figs. 17 and 18, the first an ancient species, and the second a modern one from the seas of the West Indies. The arms above are arranged around a center like the petals of a flower, and, like them, they may be opened out wide or closed up so as to look like a bud ; and this opening or closing the animal does at will. Below the radiating part, or body, there is a stem, sometimes a foot or more long, which, if the animal is alive, is planted below on LIMESTONES. the solid rock, or in the mud of the sea-bottom. Crinoids differ in many respects from polyps. One point is this: the coral which a polyp makes is all one piece, whether massive or branching; while the stony skeleton of the crinoid is in multitudes of pieces. The stem is a pile of little disks often circular and looking like button molds, as in Fig. 17; FIGS. 17, 18. IT Crinoids. Fig. 17, Woodocrinus elegans ; 18, Pentacrinus cai>ut-Medusa?, now living in the West Indies ; a-d, calcareous disks or plates of the stem, showing their 5-sided form. but sometimes 5-sided, as in Figs. 18 a, b, c, d, showing some of the forms. The arms also are made up of stony pieces. The cross lines on the arms in the above figures indicate the number of pieces of which each is made. The pieces are held together by animal membrane as long as the animal lives ; but when it dies, the pieces usually fall apart, and are scattered by the moving waters. 48 MAKING OF ROCKS. 4. Rhizopod Shells, or Foraminifers. Khixopods are among the simplest of all animals; they are very minute animals that have no organs of sense, and not even a mouth to eat with. Some of the shells are represented in Figs. 19 to 32 ; all are much enlarged excepting those in Figs. 31, 32 a, b. These animals have the faculty of extending out, at will, feelers FIGS. 19-32. 23 /^ 24 , Shells of Rhizopods. Fig. 19, Orbulina universa; 20, Globigerina rubra ; 21, Textularla g-lobulosa ; 22, Rotalia globulosa; 22 a, side view of Rotalia Boucana ; 23, Grammostomum phyllodes ; 24, n, Frondicularia annularis ; 25, Triloculina Josophina ; 26, Nodosaria vtilgaris ; 27, Lituola nautiloides ; 28, a, Flabellinarugosa ; 29, Chrysalidina gradata ; 30, a, Cuneolina pavonia ; 81, Nunimulites minimtilaria ; 32 a, b, Fusulina cylindrica. over the body that are a little root-like, and hence they are called Rliizopods, from the Greek for root-like feet. An enlarged view of one of the species, with the fiber-like arms extended, is shown in Fig. 33. A particle of food corning in contact with this network of root-like processes is enveloped and digested, the gelatinous substance of the body being nearly homogeneous, and all parts of it possessing the LIMESTONES. 49 power of digestion. All of the shells in Figs. 19-33 excepting those in Figs. 31, 32 a, b, are no larger than the finest grains of sand; and yet they FIG. SB. contain a number of cells, each of which corresponds to a separate one of the Rhizopod animals. Fig. 31 is a large foraminifer shaped like a com, and the Latin for coin, mnnntntf, suggested for it the name it bears, a Nummtdite. Rotaha veneta. Shells, corals, crinoids, and foraminifers consist almost solely of carbonate of lime, the material of limestone ; and hence their consolidation makes limestone. Shells, corals, and crinoids are usually more or less ground up under the action of the waves or currents of the ocean, and thus reduced to fragments or sand, before they are consolidated. Much coral limestone of existing seas the rock of coral reefs shows no trace of the corals of which it w r as made, because all were ground by the aid of the waves and cur- rents to a coral sand or coral mud before consolidation. But in other cases the rock contains fragments of the corals or crinoids, and sometimes entire specimens. Fig. 34 shows the aspect of a crinoidal limestone when the crinoidal remains are not wholly ground up; the disks and cylinders are portions of the stems of the crinoids. The coral reefs of the Pacific are coral-made limestones, and some of them are hundreds of square miles in area and DANA'S GEOL. STORY 4 50 MAKING OF ROCKS. many hundreds of feet in thickness. But besides corals, the shells of the coral-reef seas contribute largely to the limestone material. Foraminifers are so minute that they need no grinding FI. 34. in order to make a fine- grained rock. They live principally near the sur- face of the ocean, and their remains are especially abundant over the sea-bot- tom down to a depth of twelve or fifteen thousand feet, as has been proved by soundings in the Atlantic between Ireland and Newfoundland, and elsewhere. Chalk is made mainly of foraminifers, at depths from a few hundreds of feet to thousands ; and it is now being made, and has been through ages past, over the bottom of the ocean. There are also some plants, of the order of Seaweeds, that secrete lime, and which have thereby contributed to rock-making. Among these are included (1) coral-making plants, called Nullipores, so named from the fact that, while looking like, corals, they have no pores or cells; (2) Corallines, which are related to Nullipores, but have delicate jointed stems; (3) Coccoliths, microscopic calcareous disks, which are very abundant over some parts of the ocean's bottom and occur also in shallower waters. Crinoidal Limestone. SILICEOUS ROCKS. 51 2. Making of Siliceous Rocks or Masses. Some of the minutest and simplest of plants and animals make stony skeletons of silica instead of carbonate of lime, and hence form out of their stony skeletons beds of silica instead of beds of limestone. Although minute, often requir- ing a high microscopic power to make them visible, such species have thus been large contributors to rock-making through all geological history. Many of them are remark- able for their beauty of form and texture. The plants here included are called Diatoms. Nearly all are too minute to be distinguished without a lens. Some of the forms are shown, highly magnified, in the annexed figures, 35^40. They are strange forms for plants, and still are known to be of this king- dom of life. They have lived in i , n Diatoms highly magnified. such numbers over the bottoms of Fig. 35, Pinniilaria peregrina, Rich- shallow ponds, marshes, and Seas, mond, Va. ; 86, Pleurosigma an- gulatum, ibid. ; 37, Actinoptychus that the infinitesimal shells have . 35-40. senarius, ibid.; 38, Melosira suleata, ibid. ; a, transverse section of the same ; 39, Grammatophora marina, from the salt water at Stoningtou, Conn. ; 40, Bacillaria paradoxa, West Point. sometimes made beds scores of yards in thickness. The material of such beds looks like the finest of chalk. Owing to the hardness and extreme fineness of the grains, it was used as a polishing powder long before it was discovered that each particle was the skeleton of a 52 MAKING OF ROCKS. microscopic water plant. It is obtained from the bottoms of many marshes, and is sold for polishing; the packages in the shops from beds making the bottom of shallow ponds Richmond Infusorial Earth. a, Pinnularia peregrina; b, o, Odontidium pinmilatum ; <7, Grammatophora marina; e, Spongiolithis appemliculata ; /, Meloslra sulcata ; g, transverse view, Id.; h, Actino- cyclus Ehrenbergii ; i, Coscinodiscus apiculatus ; j, Triceratiuin obtusuin ; k, Actinop- tychus undulatus; I, Dictyocha crux; m, Dictyocha; >i, fragment of a segment of Actinoptychus senarius ; o, Navicula ; p, fragment of Coscinodiscus gigas. or marshes are sometimes labeled Silex. A bed of great extent in Virginia, near Richmond, is in some places thirty SILICEOUS ROCKS. 53 feet thick; and a little of the dust, under the miscroscope of Ehrenberg of Berlin who first made known the nature of these polishing powders presented the appearance shown in Fig. 41. All these forms were in the field of his microscope at one time. Nearly every particle is a Diatom or a fragment of one. Some Diatom beds near Monterey, in California, have a thickness exceeding fifty feet. Among animals making siliceous skeletons, the following are examples. (1) A kind illustrated in Figs. 42-44, related to the Bhizopods, but dif- fering in the forms of the shells, and in their consisting of silica. (2) Most Sponges, for sponges are animal in na- ture. Ordinary sponges are made of horn-like fibers ; but in the living state these fibers are covered thinly with a gelatinous coating which is in reality a layer of animal cells but little higher in grade than Rhizopods. In many of them these horny fibers are bristled with minute spicules of silica of various forms. A few of these forms are shown in Figs. 45-59. Some of the oblong pieces or fragments in Fig. 41, page 52, are spicules of ancient sponges. Other sponges consist wholly of fibers of transparent silica, excepting a thin coating of animal material. One of these siliceous sponges from the bottom of the East India seas COOC} coco Ooorc PCCOC ooocc oooco COO Radiolarians. 54 MAKING OF ROCKS. is shown in Fig. 60, half the natural size. The delicacy of the structure might hardly be inferred from the figure; for the sponge looks as if made of spun glass, and as if too fragile to be handled. Such siliceous sponges are common over the bottom of the ocean, and at various depths below the reach of the waves, whose violence they could not withstand. The flint of the world, or liornstone as the most of it is called (page 17), is nearly pure silica (or quartz), and, like quartz, it scratches glass easily. It is found imbedded in limestones and other rocks. It has been made mostly out of FKJS. 45-59. Siliceous Spicules of Sponges. spicules of Sponges, Diatoms, and Radiolarians, without any unusual degree of heat. This shows that such deposits, when under water, may be partly dissolved by the cold waters, and then consolidated without any external aid beyond that afforded by the saline ingredients of the waters. By the same means shells and other fossils have often been changed to quartz, or have undergone a true petrification. The harder parts of Worms, Insects, Spiders, Centipedes, and Crustaceans have contributed to the material of rocks, or occur imbedded in them ; so also do the bones and scales FIG. 60. Euplectella speciosa, or Glass Sponge, 56 MAKING OF ROCKS, of Fishes and Reptiles ; the bones and occasionally the feathers of Birds ; the bones and teeth of Quadrupeds of vari- ous kinds ; and remains of various other forms of life. Besides, the tracks of animals are occasionally met with on the sur- faces of layers, from those of Worms and Insects to those of Quadrupeds and Man. The living species of the globe that have contributed most to rocks are those of the waters, because rocks are mainly of aqueous origin ; and chiefly marine species, because the greater part of rock-making has l>een the work of the ocean. Oceanic life is in greatest profusion along the shallow waters off shore, down to a depth of one hundred and fifty feet ; the corals which make coral reefs in our present seas do not live much below this. But there is abundant life at greater depths, and life is not wanting even at a depth of 15,000 feet or more. Crabs with good eyes have been obtained from the sea-bottom at a depth of 5000 feet; lobsters without eyes at a depth of 5000 to 12,000 feet ; and a few living Mollusks from a depth exceeding 12,000 feet. Besides these species, there are through all these depths living Corals, Crinoids, and delicate siliceous Sponges related to that figured on page 55. But Rhizopods are the most abundant species (page 48), and with these, there are Radiolarians and the minutest and simplest of plants, Diatoms and Coccoliths. The Diatoms live in the ocean near the surface, but sink to the bottom as they die. The same is true of a large part of the Rhizopods. PEAT-BEDS. 57 3. Making of Peat-beds. Deposits of leaves, stems, and other remains of plants are always found in the water in marshy areas, where spongy mosses of the genus Sphagnum are growing luxuriantly, besides other water-loving plants small and large, with some kinds that can stand the water, but would thrive better were it drier. The moss, which is the chief plant in the increasing deposit, has the faculty of dying below while growing above; and thus its dead stems may be many yards long, while the living part at top is only about six inches long. The small plants and shrubs, and the trees, if such there be, shed their leaves and fruit annually, and these fall into the water. Annual plants die each year, and their stems are buried with the leaves. All the plants, the mosses excepted, sooner or later die, and thus branches and trunks are added at times to the accumulation in progress. Moreover, the bones of Birds and Quadrupeds and remains of Insects and other inferior kinds of life become buried in the deposit. The materials of plants buried under water undergo a kind of smothered combustion. They become black, then are reduced, below, to a pulpy state, or rarely to an imperfect coal ; and the mass thus altered constitutes what is called peat. Dry woody material consists one half of carbon, the main constituent of charcoal, along with two gases, oxygen and hydrogen ; and in the change the proportion of the gases 58 MAKING OF ROCKS. to the carbon is diminished about one fifth. The black color, one result of the change, is due to the carbon, as in the case of the black color of soils, many muds, and black clayey and calcareous rocks. The bed of peat sometimes increases until it is scores of yards in depth. Peat swamps are common over all conti- nents out of the tropics. Even the smaller swamps have usually a peaty bottom. The areas become superficial when the marshes dry up. The Dismal Swamp in Virginia and North Carolina is a peat swamp from one end to the other ; and no one has yet ascertained the depth of the peat. Ireland is noted for its peat swamps ; the " mosses," as they are called, of the Shan- non, are fifty miles long and two to three miles broad. The world has had its peat swamps in all ages since the first existence of abundant terrestrial vegetation; and these are the sources of all its coal-beds, each coal-bed having been at first a peat-bed. But the kinds of plants concerned in the making of the peat swamps have varied with the successive ages. 2. Quiet Chemical Work of Air and Moisture. When rocks are wholly under water, whether it be salt or fresh water, they are generally protected from decay. But if above the water, so that air as well as moisture has free access, nearly all become altered, and many crumble to sand or change to clayey earth. WORK OF AIR AND MOISTURE. 59 Blocks of some kinds of sandstone that would answer well for underwater structures, when left exposed to the air for a few years fall to pieces, or peel off in great concentric layers. Crystalline limestone (white and clouded marble) in many regions covers the surface with marble dust from its decay. Gneiss and mica schist are among the durable rocks ; and yet much of the gneiss and mica schist of the world undergoes slow alteration, so that in some regions these rocks are rotted down or have become soft earth or a gravel to a depth of fifty or a hundred feet, and even two or three hundred feet in tropical countries. This is the amount of decomposition produced in those places through a very long period of time, perhaps the whole time from the epoch of their elevation above the ocean. But it is no measure of the amount that would have taken place if the decayed portion had been removed as it was formed, as has often happened; for, in that case, alteration would have proceeded with much greater rapidity because of the freer access of air and moisture. The granite hills are often thought of as an example of the everlasting, as far as anything is so on the earth. But, while there is granite that is an enduring building stone, a large part of the granite of the world becomes so changed on long exposure that the plains and slopes around are thence deeply covered with the crumbled rock, and great masses may be shivered to fragments by a stroke of a sledge. Many granitic elevations over the earth's surface have dis- 60 MAKING OJT ROCKS. appeared beneath their own debris. Much trap-rock is as firm as the best granite. But other kinds are rotted down to a depth of many feet or yards, and sometimes only here and there a ledge shows itself above the ground as the remains of ranges of hills. Even the most solid trap, where exposed to the elements, has a decomposed outer layer, or is weathered, as the change is called. This crust is often but a line or two deep and has everywhere the same depth over blocks of like kind. But the uniformity in depth is owing to the fact that, as the elements eat inward, there is as gradual a loss of the altered grains over the outer surface. Thus invisible agencies are producing the slow destruction of the exposed parts of nearly all the rocks of the globe, even to the tops of the lofty mountains. The firmer kinds of slates (argillyte), some hard conglomerates and gneisses, and the compact limestones are among the rocks that defy the elements most successfully. In this way rocks have been prepared for the rougher geological work carried on by moving water and ice ; and through the same means the earth or soil of the world has to a large extent been made. This quiet work of air and moisture is chemical work ; and it is mostly performed through, the chemical action of two ingredients present in them, carbonic acid and oxygen. Other agencies aid in this slow destruction, as explained on pages beyond. WORK OF WINDS. 61 3. The Work of Winds. The wind, or moving air, works geologically by trans- portation, by the deposition of the material it transports, and by abrading and rending the rocks and other objects in its way. 1. Transportation and Deposition. The winds carry sands from one place to another; and wherever the earth's surface is one of dry sand, and the winds blow strongest and longest in one direction, great accumulations of sand are made. Even when the windows of a house in a city are ordinarily kept closed, the dust will get in. Seashores are often regions of sand, owing to the work of the waves. The heavy winds take up the loose, dry sands and carry them beyond the beach, to make ranges of sand hills, often 20 to 30 feet or more high. Thence the hills frequently travel inland, through the same means, sometimes burying forests, as on the west coast of Michi- gan, sometimes overwhelming villages, as in England and France, leaving at times only the top of a church spire to mark the site. The west winds have driven the sands of the Desert of Sahara over parts of Egypt, and ancient cities have thus been buried. The stratification of a hill of drifted sands is so peculiar that it is easy to tell when sand rocks have been formed through the agency of the winds. Fig. 61 represents a part of a section observed in the Pictured Rocks on the south 62 MAKING OF KOCKS. FIG. 61. Part of a Section of a Drift Sand Hill, showing the Stratification. shores of Lake Superior. The layers dip in many direc- tions. Such a structure is owing to the accidents to which the sand hills are exposed. A heavy storm perhaps aided by heavy waves at high tide often carries away part of a hill. Then the winds build it up anew, putting the successive drifts which make the successive layers over the new surface, differing much from the first in its slopes. The hill suffers from another storm, and is again built up during the period of quieter weather that follows. This may take place many times. The result is the kind of irregularity of stratification illustrated in Fig. 61. 2. Abrasion. Sands carried by winds over rocks often wear the surfaces deeply, as well exemplified in the semi-desert Via. 62. Wind-worn Rocks of the Egyptian Desert. regions of southern California, Nevada, and other dry parts of the west, in the Grand Traverse region near Lake Michi- gan, and elsewhere. This agency in dry countries has scoured WORK OF FRESH WATERS. 63 out gorges, shaped and undermined bluffs, and thus given to the landscape its prominent features. Fig. 62 illustrates the work of the winds in the Egyptian desert ; the upturned ledges have had their softer layers worn away, leaving a compact limestone layer as the summit of each. Even the harder rock yields; for the markings over the surface indi- cate the positions of fossils that are left projecting because siliceous. The abrading work, it is to be noted, is performed for the most part by the sand and gravel which the air trans- ports. Man has taken the hint, and now uses sand driven by steam to etch on glass and to carve granite and other rocks. 3. Rending. The rending power of moving air is shown at times in the tearing of houses to pieces or taking off of their roofs, in the overthrowing of walls and uprooting of trees. These effects depend, not on any transported sand in the air, but on the movement of the air in mass against the obstructing agent. 4. The Work of Fresh Waters. Running water is at work universally over a continent wherever the clouds yield rain and there is a slope to pro- duce movement; and it acts with greatest energy where the slope is greatest, or about high hills and mountains. It works at abrasion, transportation, and deposition, and with vastly greater efficiency than moving air. 64 MAKING OF EOCKS. The waters of the rains, mist, and dew about the mountain tops descend in drops and rills, and then gather into plunging streamlets and torrents ; the many torrents combine below into larger streams; and these, from over a wide region, unite to make the great rivers. The Mississippi has its arms reaching westward and northward to various summits in the Kocky Mountains, and eastward to the Appalachians ; and its greatness is owing to the vast breadth of the area it drains. Not only mountains, but all the small elevations over a land, and even its little slopes, have, \\liru it rains, their rills combining into torrents, and these into larger streams, which flow off to join some river. The waters of the clouds no sooner drop to the ground than they begin to tear off and carry away grains of earth from the rocks or slopes. The work over the larger part of a country may be almost wholly suspended in the dry season ; but when the rains set in, the surface is alive with its workers, small and great. Torrents become increased immensely in depth and force, and earth and often rocks are torn up and borne along in vast quantities. The little rills groove lightly the sand or gravel over which they flow. The streamlets, made by the uniting rills, cut deeper and wider channels. The torrents produced from the combined streams and streamlets gouge out and wear away even the harder rocks, and, as their volume increases, make great valleys. The subject of the making of valleys is illustrated on page 103. \VOI:K OF FIIKSH WATERS. 65 Where, along a valley, harder and softer layers of rock alternate, one lying above the other, the harder rocks wear slowly, while the softer yield easily ; and so a valley is made to have abrupt descents along its channel, and the stream goes in leaps or >.. The Work of the Ocean. The mechanical work of the ocean is carried forward chiefly through (1) its tidal movements ; (2) its waves ; and (3) its currents. 1. Tides. With each incoming tide the waters flow up the coast and into all bays and mouths of rivers, rising several feet and sometimes yards above low-tide level ; and then, with the ebb, the same waters flow back and once more leave the mud-flats and sand-banks of the bays and coasts exposed to view. This retreat of the tide allows the rivers to discharge freely and carry out their detritus to sea ; but soon again the inflow stops the outward movement and reverses it. During the time of slackened flow the waters drop their detritus, part about the mouth of the stream, part along the adjoining coast, and part in the shallow waters of the sea outside. The incoming tide is feeble in movement, swelling gently over the land and up the bays. It becomes rapid only where it passes through narrow channels, in which case the large body of water is forced to make up for the small passage- way by moving at greater speed. But the outflowing tide often moves rapidly over the bottom of bays, and especially when a river empties into the bay and adds to the amount of water. Besides, it takes up additional detritus from the bottom, and bears it out to sea. It thus prevents the 70 MAKING OF ROCKS. entrances to bays or harbors from becoming tilled up by the deposits of the iiiwashing tide. 2. Waves. The sea in its quiet state is rarely without some swell, which causes at short intervals a gentle move- ment on the beach and some rustling of the waters along rocky shores. Generally there are waves and breakers ; and when a heavy storm is in progress the waves rise to a great height and plunge violently upon the beach and against all exposed rocks, wave following wave in quick succession through days or it may be weeks together. With each storm the waves renew their violent strokes, and in many seas the action is almost incessant. The plunge on the beach grinds the stones against one another, gradually rounding them and finally reducing them to sand, and the sand to finer and finer sand. The waters after the plunge retreat down the beach underneath the new incoming wave; and this "undertow" carries off the finer sand made by the grinding, to drop it in the deeper waters off the coast, leaving . the coarser sand to constitute the beach. Thus wave-action grinds to powder and removes the feld- spar and other softer minerals of the sand, leaving behind the harder quartz grains; and consequently, the sand and pebbles of beaches consist mostly of quartz. Moreover, where beaches of sand line a coast there are offshore deposits of mud made out of the fine material carried seaward by the undertow. In no age of the world have sand-beds been WORK OF THE OCEAN. 71 formed without the making of mud-beds in their immediate vicinity. The cliffs, or exposed ledges of rock, are worn away under the incessant battering and afford new stones and sand for the beach and the shallow waters adjoining. Most rocky shores, especially those of stormy seas, show, by their rugged cliffs, needles, arches, and rocky islets, the effects of the storm-driven waves. It is to be remembered that the ocean, as stated on page 58, often finds the work of destruction facilitated by the weakening or decomposition the rocks have undergone through the quiet action of air and moisture. Another method of destruction is explained beyond on page 84. The waves, as they move toward the shores over the shelv- ing bottom, bear the sediment in the waters shoreward, and throw more or less of it on the beach ; and thus the beach grows in extent. The sediment is, in general, either what it gets from the battered rocks of the coast, or what the rivers pour into the sea. At the present time the Atlantic receives an immense amount of detritus through the many large streams of eastern North America; and, as a consequence, the shores are extensive sand-flats from New York south- ward; there are generally long beaches, with shallow basins or sounds inside, and wide low regions more inland. This Atlantic border has been growing seaward for ages through the means mentioned, with but little aid from the wear of seashore cliffs. But in the earlier geological ages 72 MAKING OF ROCKS. this was not so; for the continent was to a large extent more or less submerged, and the waves made a free sweep over its surface, battering the rocks wherever within their reach over the wide area, and thus making its own sedi- ment; for there were only small streams on the small lands to give any help, 3. Wind-made Currents. The winds, especially the prevail- ing storm winds, are the chief source of strong currents along sea-borders, as well as of high waves and careering breakers. They drive the waters before them, moving them to consider- able depths ; and where these currents sweep along a coast, they gather detritus from the bottom and from the beaches, and also from the discharging rivers, and drop it again where obstructing shores or capes are met. This drifting action often makes long sand-spits and sand-bars nearly all the way across the mouth of a bay. New York Bay is thus shut in, the entrances being narrow channels through the sand-bars. These channels are kept open by the outflow of the waters of the Hudson River and some New Jersey rivers, together with those of the outflowing tide. 4. Contributions to Sea-border Sands and Deposits by the Life of the Waters. In the warmer seas of the world MoU-uuJcx are very abundant. The heavier storm-waves tear them from the muddy bottom in or over which they are living, and throw them on the beach. There they are exposed to the incessant grinding which stones and ordinary sands expe- rience elsewhere, and thus they become reduced to sand. WORK OF THE OCEAN. 73 Every storm adds to the shells of the beach as well as to the shell-sand. Sand-deposits are thus made out of shells ; and they keep growing and may become of great extent. They are not deposits of quartz sand, but of calca- reous sand. The riner shell-sand is swept out into the shallow waters, and there produces a finer deposit. The hardening of such deposits makes limestone ; and the shells that happen to escape the grinding are its fossils. In this way limestones have been made in all geological ages. Shell-rocks are now forming at St. Augustine, Florida, and the limestone there made is used as a building stone. In other parts of tropical seas there are corals growing profusely within reach of the waves, and below to a depth of about 150 feet, with Mollusks and other kinds of sea life. .Many of the corals become broken or torn up by the waves and are carried to the beach, and there ground up and spread out in beach deposits and off-shore deposits. The shells of the reef-grounds add much to the coral sands. These beds of sand or mud harden in the water, and then become the coral-reef rock, a true limestone, similar to many of ancient time. Fig. 64 is a view of a coral island, or atoll, of the Pacific. The encircling reef consists wholly of coral-reef rock and overlying coral sands; and the whole height out of water is usually but 1.2 to 20 feet, or as high as the waves and the winds can throw the sands. The lake or lagoon within is an inclosed piece of the ocean, and often, when a channel 74 MAKING OF HOCKS. for entrance exists, it is an excellent harbor for shipping. Fig. 65 represents one of the ordinary high islands of the ocean with its shores bordered by coral reefs. Such reefs i<;. 64. Coral Island, or Atoll. are usually under water except at low tide. The inner reef / is called the fringing reef, and b, the barrier, or outer reef. At h there is a channel through the barrier opening to a large harbor. Such reefs and islands exist in various parts of the tropical Pacific, and also in the East Indies and High Island with Barrier (b) and Fringing (f) Reefs. the West Indies. They border northeast Australia for looo miles. 5. Oceanic Currents. The ocean has its system of circu- lation, or of great currents. The Gulf Stream is one of these great currents. Its waters flow westward in the tropical Atlantic, bend northward as they pass the West India seas, then flow northeastward, parallel with the North American coast as far as New- WOIiK OF THE OCEAN. 75 foundland, and then gradually curve eastward, toward Great Britain. Thence a part continues either side of Iceland to the Arctic seas, from which part returns as a cold Labrador current, along the coast of Labrador and farther south; another part continues eastward north of Europe and Asia. This great current moves but o miles an hour where swift- est, and at this rate only in part of the straits of Florida. Its average rate, parallel with North America, is 2^ miles an hour; but along the sides of the continent it is hardly felt at all anywhere along this coast, not even in the Florida straits. It hence gets no detritus from the Avear of coasts, and is too feeble to carry anything but the very finest silt. The ocean's bottom shows that it receives almost nothing either in this way or from the currents of great rivers. Local currents, made by storm winds along shores, have been far more important transporters and distributers of detritus than these oceanic currents. When, however, the continents were submerged a few hundred feet or less in ancient time, such currents, sweeping over the surface, would have done much work in Avearing rocks and transporting detritus, espe- cially in shalloAv Avaters and along narroAv channels. 6. Markings made over Sand-flats and Mud-flats. Both Avaves and gentle currents raise ripples over the sands ; and the ripple-marks made by the ocean in ancient times are often preserved in the rocks (Fig. 66). Wherever they occur they shoAv that the sands of Avhich the rocks Avere formed Avere within reach of Avaves or gentle currents. 76 MAKING OF ROCKS. The mud of a mud-flat or of a dried-up puddle along a roadside is often found cracked as a consequence of drying; and such mitdrcracke are frequently preserved in sedimentary rocks (Fig. 67). They are of great interest to the geologist; for they show that the layer in which they occur was not of deep-water origin; but beyond question, was exposed, for a while at least, above the water's surface to the drying air or sun, as mud is now often exposed along a roadside, or over the mud-flats of an estuary. Such cracks become filled with the next deposit of detritus, and this filling has often been PIGS. 60, 67. Ripple-marks. Mud-cracks. afterward so consolidated as to be harder than the rock out- side ; and hence on a worn surface the fillings of the cracks often make a network of little ridgelets, such as are shown in Fig. 67. WORK OF THE OCEAN. 77 Again, mud-flats sometimes have the surface covered with rain-drop impressions, after a short shower, in which the drops were large; and many shales (rocks made of mud or day) retain these markings (Fig. OS). Impressions of the foot- prints or trails of animals, also, and even those of in- sects, are not uncommon. Such delicate impressions are pre- served, because soon after Rain-drop Impressions, they are made they become covered with a layer of fine detritus ; and after that nothing can erase them short of the removal of the deposit itself. 7. Great Extent of Deposits of Aquatic Origin. The rocks that have been made by fresh waters and the oceans are of vast extent. They are the sandstones, conglomerates, and shales of the world; and they include the limestones also. The ocean has done far the larger part of the rock-making. In the earlier geological ages it worked almost alone; for the lands were very small, and only large lands can have large rivers and river deposits. Afterward, in the coal era, there was at least one large delta or estuary on the borders of the American continent, that of the St. Lawrence; and in later times, rivers have given important aid. During the last of the ages, after the continents had reached ne'arly their present extent, and the mountains their modern height 78 MAKING OF ROCKS. and numbers, the rivers did the larger part of the distribu- tion of rock material. Sedimentary rocks show that they were formed through the action of water, often by the rounded or water-worn pebbles they contain, or by the water-worn sand, or from a resemblance in constitution to a consolidated bed of mud or clay ; by their relics of aquatic life, and by the indica- tions of wave-action or current-action above pointed out; and by their division into layers, such as exist in known sediments or deposits from waters ; and when marine, they indicate it generally by the presence of remains of marine life. ('). The Work of Ice. 1. Expansion on Freezing. When Avater freezes it expands. If it freezes in a pitcher, the expansion is pretty sure to break the pitcher. If it freezes in the crevice of a rock, it opens the crevice; and by repeating the process, winter after winter, in the colder countries of the globe, it pries off and breaks apart rocks, and often makes a slope of broken blocks, or talus, at the foot of a bluff. By opening cracks in this way it gives air and moisture new chances to do their quiet work of destruction. 2. Transportation by the Ice of Rivers or Lakes. When water freezes over a river it often envelops stones along the shore; and then, whenever there is a breaking up, the ice with its load of stones is often floated off down stream; AVORK OF ICE. 79 or if the water of a stream or lake rises in consequence of a flood, the stones may be carried farther up the shore and dropped there, and so make, in time, extensive accumulations of stones, large and small. In cold countries ice often forms thickly about the stones in the bottom of a stream; and as it is lighter than water it may become thick enough to serve as a float to lift the stone from the bottom, so that both ice and stone journey together with the current, to become lodged some- where along the shores or dropped to the bottom. These are commonplace ways in which ice does geological work. Its greater labors are performed when it is in the condition of a glacier. 3. Glaciers. Glaciers are broad and deep streams of ice in the great valleys of snowy mountains like the Alps. The snows that fall about the summits above the level of per- petual snow accumulate over the high region until the depth is one or more hundred feet. At bottom it is packed by the pressure and becomes ice. Its weight causes the ice to descend the slopes, of the mountains and along the valleys, which it fills from side to side. The width of the ice of the valley may be several miles; its depth in the Alpine valleys is generally from 200 to 500 feet. The glaciers descend far below the line of perpetual snow to where the fields are green and gardens flourish; and this takes place because there is so thick a mass of ice. In the Alps the glaciers stretch down the valleys 4500 to 80 MAKING OF KOCKS. r>oOO feet below the snow-line. At (irindelwald two glaciers terminate within a short distance of the village. The rate of movement in the Alps in summer is mostly between 10 and 20 inches a day, and half this in winter: 12 inches a day corresponds to a mile in about 14. 1 , years. >'!(.. till. Glacier of Zermatt, or the Corner Glacier. Fig. 69. from a sketch in Agassiz's great work on glaciers, represents one of tliese great ice-streams or glaciers descend- ing a valley in the Moiit.a, Rosa region of the Alps. A valley often narrows and widens at intervals, or changes its slope from nearly vertical to a gentle incline, or to a hori- AVOUK OF ICE. 81 /ontal surfact'. The ice has to accommodate itself to all these variations. Ou turning an angle it Incomes liroken. or lias great numbers of deep -crevasses" made through it, espe- cially on the side opposite the angle. ()n commencing a rapid descent, great breaks, or crevasses, cross the glacier from one side to the other. On again reaching a level place, the ice closes up, and the glacier loses nearly all its crevasses. The ice is brittle, and freezes together when Kio. Til. Glacial Scratches and Planing. the separated parts are brought in contact again; so that. as it moves, it goes on breaking and mending itself. Ice is plastic; for it may be made into rods by pressing it through a hole, and will take the impress of a medal; so that in this way also it can accommodate itself to the changing character of the surface over which it moves. The steep upper slopes of the valley in which a glacier lies often send down stones and earth, or avalanches of DANA'S I.KOI.. >ioi:v 82 MAKING OP ROCKS. ice and rocks. Through such falls a line of earth and rocks is commonly made along either margin of the glacier, which is called a lateral moraine. These moraines are carried with the ice to where it melts, and there dropped, making a terminal moraine. Other blocks are taken up by the sides and bottom of the glacier. FIG. 71. View on Roche-Moutonnee Creek, Colorado. The rocks of the surface over which a glacier has moved are scratched, planed, or polished, often with great perfec- tion, as illustrated in Fig. 70. Ledges of rocks also are rounded, making \vlmt are called sheep-backs, or, in French, roches montonin'^. They are WORK OF ICE. 83 most likely to form where the rock has some portions much harder than others : these hard portions can best resist the wear and they become the sheep-backs. Fig. 71 represents the roch mot/ton IH'PS in a valley of the mountains of Colorado, a valley in the Rocky Mountains leading up to the .Mountain of the Holy Cross, seen in the distant part of the view. It is from the Report of Dr. Hay den for 1S7.">. Xo glaciers exist there now; but once they were of great extent and depth. The scratching and polishing are done by the stones in the bottom and sides of the glacier; and these stones also, as is natural, are planed off and scratched. 4. Icebergs. In the Arctic regions the glaciers of Green- land, loaded with their moraines, extend down into the sea, and. the part in the water sooner or later breaks off and floats away as an iceberg. These icebergs are carried south by the Labrador current, and large numbers of them in the course of a season reach the Banks of Newfoundland. There they find the waters warmer, in consequence of the nearness of the Gulf Stream, and they melt and drop their burden of stones and earth into the waters. It has been sug- gested that the submerged Banks of Newfoundland owe their existence to the melting there and consequent unlading of icebergs. It thus appears that ice does geologic work (1), in the act of formation, through its expansion; (2) as glaciers, by transporting over the land earth and stones and rocks 84 MAKING OF ROCKS. some of the rocks as large as ordinary houses and dropping them when the ice melts; (.'>) by tearing off rocks from the ledges over which it may move, espe- cially where there are opened seams, or joints; (4) by wearing deeply into the soft rocks over which it mav move, and scratching and polishing hard rock ; (5j as JtoattHf/ ice or icebergs, by transporting rocks, stones, and earth over water from one region to another; moreover (6) it often makes temporary dams across valleys, that cause great devastation when they give way; and (7), it makes lakes in valleys and over a glaciated region by the drop- ping of moraines to act as dams. 7. The Work of Heat. The effects of heat here considered are the following: 1. Expansion and contraction from change of temperature. 2. The fusion of rocks, and their ejection through fissures and volcanic vents. 1. Expansion and Contraction. Owing to the alternation each day of sunlight and dark- ness, the surfaces of exposed rocks experience an alternate heating and cooling, and therefore alternate expansion and contraction. This cause, which is sufficient to break the solder of soldered metallic roofs on houses, to loosen the cemented blocks of a stone wall, and to give a perceptible movement to high stone towers, tends to start off the grains, WORK OF HEAT. 85 and sometimes separates an outer layer from ban 1 rocks, especially when the surface is weathered. As this agency is at work over the whole surface of the earth, it is an important addition, in a quiet way, to the chemical work of air and moisture, in the making of earth or gravel for the formation of rock deposits ; and it has been so ever since the sun first shone upon bare rocks. A foot or two of soil is a protection against this method of degradation. Again, heat gaining access to rocks beneath a region expands them and causes an elevation of the surface; and loss of heat produces a reverse effect. Fractures may attend such changes of level, and also light earthquakes. 2. Jfakiitf/ of Rocks thront/h Fusion: Volcanoes. 1. Volcanoes. igneous rocks are described on page 33 as having come up in a melted state to the earth's sur- face through fissures. In many cases they have been ejected at intervals from one and the same opening for long periods of time. When fissures are filled and closed by one eruption, they make dikes of igneous rock, and also one or more beds, or sheets, if the melted material flows from the fissure over the adjoining region. But when a vent remains open for many successive erup- tions it becomes then the center of a true volcano or ti re- mountain. The outflows of liquid rock, and ejections of volcanic sand or cinders from the vent on one side or the 86 MAKING OF KOCKS. other, produce a liill or mountain of a form more or less nearly conical. Fig. ~U represents Mount Shasta, one of the volcanic mountains of. western North America, having an elevation, according to AYhitney, of 14,440 feet. It is not now in action, yet has hot springs near its summit. It Mount Shasta, from the North, from a photograph by Watkins. also represents well the general form of the great volcanoes of the Cascade range to the north of it in Oregon, and also of those of Mexico, and of the Andes in South America. Of the latter, Cotopaxi is an active volcano 19,613 feet in height, and Arequipa another, 18,877 feet; WORK OF HEAT. 87 while Aconcagua, of Chile, an extinct cone, has a height of 23,000 feet, and is the loftiest peak in the Andes. Active volcanoes, in time of qniet, send forth only vapors. In periods of eruption, streams of lava (liquid rock) are poured out, either over the edge of the crater or more commonly through breaks in the sides of the mountain. At the same time cinders, or fragments of lava, are often thrown from the crater to a great height above the volcano, or the finer particles called ashes, which drift with the wind and descend in showers. De- posits of wet ashes make a fragmental rock resembling a sandstone or breccia, called tufa. Volcanic cones vary much in angle of slope. When made of dry cinders the angle is often 40 to 42. If formed through the alternations of lavas and cinders, or of tufas, the slope may be 30 or less, as in Figs. 72 and 73. Fig. 73 gives the slopes of the volcano of Jorullo, in Mexico. Many of the grandest volcanoes of the world, like Etna, and those of Hawaii, in the Sandwich Islands, have an exceedingly gentle slope, the height often only a twentieth of the breadth. Fig. 74 gives the slope of Mount Loa, FlG 74 Hawaii. Its height is 13,675 feet. Such cones are made almost solely of lavas; and they have so gentle a slope because the melted rock of the region flows off freely, it being of the more fusible kind, basalt. 88 MAKING OF ROCKS. The eruptions of volcanoes are owing mainly to the waters that gain access to the fires. The rains of the region pro- duce underground streams and trickling waters that descend and pass into the melted rock, there to be changed to vapor. Sea-water, when volcanoes are near or in the ocean, some- times presses its way in, or gains access suddenly through fractures. The vapor penetrating the liquid mass expands the whole, causing it to rise in the vent. With the increas- ing height of the column of melted rock in the mountain, the vapors become more active. The pressure from the high liquid column, and from the vapors, breaks the moun- tain, and the lavas run out, devastating the country, it may be, for a score of miles or more. When the sea gains sudden access to a volcanic vent, the eruption is ac- companied with violent qxiakings of the mountain. Every few years the country 011 one side or another of Vesu- vius is deluged with the fiery rock, cultivated fields are buried, and not unfrequently villages are destroyed. Pom- peii and Herculaneum were buried beneath the cinders of an eruption that took place in the year 70; and since then several streams of lava have flowed down over Hn- culaneum, adding to the depth at which it is buried. Mount Loa, on Hawaii, has had eight great eruptions through fissures in the sides of the mountain since 1840. There is a summit crater at a height of 13,7(>5 feet, and another, still larger, called Kilauea, nearly -1000 feet above the sea. The map, Fig. 7">, shows the courses of the erup- WORK OF HEAT. 80 tions. Mount Kea is another volcanic mountain, as high as Loa, and another, Mount Hualalai, is over 8000 feet high. FIG. "5. , *, TAELE LANDK/000 ,O ,0.00 --.....>> v-g" . . -^ : 1 -,.iiSc5.^' ^-f.f,e"s*-^- c ^;>- '^" ;"-" HAWAII F.ROM THE GOVEBJOTENT MAP The liquid rock comes up from some deep-seated iire- region. Volcanic mountains are very numerous along the Andes; in (,'entral America and Mexico; in Oregon and Washington 90 MAKING OF ROCKS. from Mount . Shasta to Mount Baker and beyond; in the Alaska archipelago on the north; all along the west side of the Pacific through Japan and the East Indies ; south- ward in the New Hebrides, Xew Zealand, and in Antarc- tic regions. Thus the Pacific, the great ocean of the globe, is girt with volcanoes, besides having many, though mostly extinct cones, over its surface. The Atlantic, in contrast with it, has none on its borders, except in the Gulf of Guinea on the coast of Africa, and in the West Indies ; and but few over its interior. 2. Hot Springs; Geysers. Hot springs often make deposits of silica on their borders, owing to the silica the heat has enabled the waters to take up from the rocks with which they are in contact. Such springs sometimes throw their waters in jets at longer or shorter intervals, and they art- then called geysers. One of the geysers of the Yellowstone Park, in the Rocky Mountains (where there are great num- bers of them), is represented in action in Fig. 7(5, taken from Hay den's Report for 1873. It throws the water to a height of 200 feet or more. The geysers of Yellowstone Park are mostly about the Fire-hole River, a fork of Madison River, and near Shoshone Lake, the head of Snake River, and not far from the head of the Yellowstone. The number of hot springs, hot lakes, and geysers in the Park has been stated to be not less than 10,000. 3. Solfataras. Solfataras are feebly active volcanic vents, where vapors issue and sulphur is deposited. Ki.:. Beehive Geyser in Action. 92 MAKING OF ROCKS. 8. Solidification and Metamorphism. 1. Solidification. The two most common methods of solidification of fragmental deposits are (1) by means of lime carbonate (strictly bicarbonate) ; and (-) by silica. All waters contain some carbonic acid gas. The rains take it from the atmosphere and carry it down to the soil, lakes, and oceans ; and the respiration of animals and the de- composition of organic matter are other sources. When calca- reous sands, as those of coral, or shells, or powdered lime- stone, are wet by carbonated waters, these waters take up some of the lime carbonate in the form of bicarbonate; and this lime carbonate they deposit among the grains, as the water evaporates, and the excess of carbonic acid is exhaled, cementing them together. The process goes on also under Avater where there is no evaporation, as in the conversion of closely compacted coral sands and shell sands below tide level into coral limestone or shell limestone. \Vaters containing a little soda or potash in solution will dissolve the silica of organic relics, such as sponge spicules and ])iatoms, even when cold, and more readily when hot. The masses of flint or hornstone found in some beds of chalk and many other kinds of limestone were made out of such relics in the sea through their partial solution and consolidation, and generally without heat above the ordinary temperature. Hot waters, as explained on page 18, are very likely to SOLIDIFICATION AND METAMORPHISM. 93 hold silica in solution ; and if so, such waters, as they cool, will deposit the silica among the grains of quartz sand, or pebbles, and produce the firmest of rocks. Oxide of iron, also, is sometimes a cement, even of common gravel beds. Some of the oldest of sandstones and shales are still soft, or feebly consolidated, because not furnished with any cementing material. 2. Metamorphism. Metamorphism, like metamorphosis, means change of some fundamental kind. In geology it may be change only in texture ; but it includes also changes in the nature or composition of the minerals of a rock. It is change produced when rocks are subjected to heat with moisture, for heat cannot be distributed through the rocks without the agency of moisture to become steam and so give it diffusion. When melted rock ascends along a fissure, it heat a the walls, and the effects of the heat are in part metamorphic effects. Sometimes it only consolidates the rocks. But, besides this, if a limestone is intersected by the fissure, the heat may crystallize the limestone to a depth of some inches or feet, converting thereby the compact rock into one of crystalline texture looking like coarse loaf sugar. This crystallization is one kind of metamorphism. It may also make epidote or garnet, or some other mineral, in the wall of the fissure, if the elements of the mineral are present in any of the intersected rocks. This chemical change is a second kind of metamorphism. 94 MAKING OF ROCKS. Other examples occur sometimes about hot springs. The waters of geysers deposit a large amount of silica in the form of opal, making opal basins for themselves to play in, and spreading the opal widely over the region around. They also produce the petrifaction of wood, changing the trunk of a tree into silica. The above cases are examples of load metamorphism ; that is, metamorphic change in a rock adjoining a I<-<) or <>(> feet of depth. As the heated region has often been hundreds of miles long and thousands of square miles in area, and the temperature for the most part over 1000 F., it is not sur- prising that crystallization and other changes of great rock formations should have been a result. The larger part of the rocks of New England and of much of the Atlantic border to the south, of Canada to the north, of the northern part of New York, Michigan. Wisconsin, and Minnesota, of large areas in the summit region of the Rocky Mountains, and over the Pacific slope, are meta- morphic rocks. '.). Veins and Ore Deposits. 1. General Characters. Veins fill fissures in the earth's rocks. They may cut across the rocks vertically or nearly so, as in Fig. 77 (act, bb) ; or be much inclined, as in Fig. 78. The fissures may be regular, with nearly paral- lel Avails for long distances ; but they commonly vary greatly VEINS AND OKE DEPOSITS. 97 ill width along their course. The width may be that of paper, or of hundreds of feet. Besides veins interaectimj the strata, there are others of large size as well as small, that are the fillings of oniony* between the layers of a laminated or schistose rock, as FIGS. 77, 7N Intersecting Veins, /, xion by the streams of the land; (H) by >ij>liftiti.000 feet high, as already stated, and numer- 10() MAKING OF MOUNTAINS. ous others in that chain, were made by volcanic, action. Mount Etna, in Sicily, is nearly 11,000 feet high; two volcanic mountains of Hawaii are nearly 14,000 feet high ; Ori/aba, in Mexico, 18,200 feet. This is the least important of the methods by which moun- tains have been formed. 2. Mountains and Hills produced by the Erosion of Elevated Lands. In all mountain regions the lofty summits and ridges have been shaped out mainly, as already explained, by running water, and such heights are therefore examples of the results of erosion on elevated lands. I Jut the mountain-making is more completely the work of erosion when a region of horizontal rocks, which was a lofty plateau when first raised, has undergone long erosion. Owing to the height, perhaps several thousand feet, the torrents which the rains make and feed have a steep descent, and therefore great- eroding power; and ultimately such a plateau has often been reduced to a region of profound valleys and precip- itous ridges. The elevations described on page 10.> as the remnants of a great rock-formation, are examples of moun- tain sculpture of this kind. These remains are battlemented heights, temples of mountainous dimensions, towers, and columns. The Oatskills are a group of high summits ,'JOOO to 4000 feet above the sea level, carved by running water out of an elevated region of nearly horizontal rocks. Such examples are common over the world. For, in the changes EROSION OF ELEVATED LANDS. 107 of level which the earth's crust has undergone, areas have often been lifted without much disturbance of the beds. The elevations have often a broad cap of harder rock at top, and if of much breadth they are called mesas, or table-moun- tains, from the Spanish mesa, a table. Many mesas over the Pacific slope have at top thick sheets of some igneous rock, Avhich has served to protect the rock below from wear. Examples of monumental forms on a small scale oc- cur iu Colorado, and have given the name of Monu- ment Park to the region. Fig. (S4 is a sketch of one of its scenes, from Hayden's Iveport for l!S7o. Such effects of erosion may have been produced mainly by rains and running water; but they are in part due to the winds ; to the quiet Scene in M n ment Park, Colorado. work, chemical in nature, of air and moisture ; to the alternate heating and cooling of the surface in consequence of the daily changes of temperature ; and in frosty regions, or where the winters are cold, to the freezing of moisture over the surface. Over undisturbed regions of Tertiary and Quaternary for- mations of moderate elevation, erosion has often reduced the once level surface to a collection of hills. In some parts of 108 MAKING OF MOUNTAINS. the eastern slope and summit of the Kocky Mountain region the Tertiary is worn into a labyrinth of valleys and variously shaped ridges, needles, and table-like elevations. This mountain-making by erosion is an external sculpturing of the earth's surface, and not true mountain-making. 3. Mountains made by Upturnings and Flexures of Rocks, and Bendings of the Earth's Crust. Mountain ranges have been made, for the most part, through bendings of the earth's crust, and the upturning, flexing, and faulting of the rocks. 1. Upturned Rocks. The layers of stratified rocks were orig- inally, with small exceptions, horizontal, this -being the posi- tion which layers of sediment usually have when forming. Now, very commonly, they are more or less upturned. Some- times the angle of inclination is small ; but in most mountain regions the beds are steeply inclined, and often are ver- tical or nearly so. In the study of the inclined position of strata the geologist studies the origin of mountains. The inclination of the beds below a horizontal plane is called the dip; and the horizontal direction at right angles to the >li/> is the strike. When the roof of a house slopes in opposite direc- tions from a horizontal ridge-pole, the angle of slope or the pitch of the roof corresponds to the dip; and the direction of the ridge-pole, to the strike. Some of the positions of upturned rocks are shown in the following figures. Fig. 85 represents a ledge of rocks pro- UPTUJININGS AND FLEXURES OF ROCKS. 109 jecting above the ground ; dp is the direction of the dip, aiid st that of the strike. Fig. 8G represents a portion of the coal- formation with stumps of trees rising out of the coal-beds, Fins. S5, S6. Upturned Strata. which have lost their vertical position because of the upturn- ing of the strata. 2. Flexures. Figs. 87-91 represent flexures or folds of the strata, such as are of common occurrence. The folds in a FIGS. 87-91. Flexed or Folded Strata. mountain region are sometimes many miles in span ; and often one arch rises beyond another. The Appalachians and Jura Mountains are full of examples. 110 MAKING OF MOUNTAINS. The upward bend (at ax in. Figs. 87-90) is called an a nfi- cline, from the Greek signifying inclined in opposite directions; and the downward bend (at a'x') a syncline, meaning inclined together. ax, a'x' are the positions of the axial planes of the folds, and the intersections of these planes with the surface of the strata are the axes of the folds; ax an iiti<-l/nt, and a'x' a syiH-Hiuil ".'/*. In Fig. 91 three folds are raised together. on. n m iv v vi v vr YIV m ir Section from the Great North, to the Little North, Mountain, through Bore Springs, Virginia, tf, positions of thermal spi-in*.'-. Fig. 92 represents an actual section six miles long, from a part of the Appalachians, illustrating well the flexures. But it illustrates another fact : that, since the flexures were made, the region has been worn by waters, either those of rivers or the ocean, so that the tops of the flex- ures are worn off, and where they once were there are now often valleys ; siich a valley is represented in Fig. 92, to the left of the middle above II. The tops of such folds were broken deeply while the bending and stretching was in progress, and the breaks would have opened upward; and therefore these should be the parts most deeply eroded. The thin black layer over IV, on the left, was once con- tinuous with IV, near the middle of the section ; and so with the rest. To the right the beds are vertical. Another view of upturned and eroded rocks as they UFTUIiNINGS AND FLEXUllES OF HOCKS. Ill occur at a place in western Colorado is given in Fig. 93. The strata in the foreground have the dip and order of superpo- sition the reverse of those more distant, showing that a twist is connected with the upturning. Other examples of folding Ym. 93. Upturned Strata of the West Slope of the Elk Mountains, Colorado. The light-shaded stratum, Triassieo-.Junis>u - ; that to the right of it, Carboniferous; that to the left, Cretaceous. and of subsequent degradation, from the Alleghanies, are illus- trated in Figs. 94-99. In each case the harder stratum in the series determines in a large degree the final form of the hill and the landscape effect of the erosion. Fig. 100 represents a still more remarkable case of flex- ures and subsequent erosion ; the folded region has been Fis. 94 99. Degradation of a Folded Mountain Region. worn away to a nearly level surface, so that the existence of flexures is to be ascertained only in vertical sections of the rocks. Regions of such folded rocks are generally very difficult to study, because of the extensive erosion. 112 MAKING OF MOUNTAINS. Ledges and ridges in which the strata slope only in one direction are often one side or part of a great fold. But in many cases, by slioving along faidts and over the rocks beyond there is only a slope in one direction made, and this is called a monocline) from the Greek for one and incline. General View of Folds in the Archaean Rocks of Canada. '3. Fractures and Faults. Besides flexures, great and small fractures have been made in large numbers during epochs of upturning or mountain-making. Fig. 1()1 repre- sents strata thus broken ; and, moreover, the beds are faulted or displaced along the fractures. The beds numbered 1, 1, 1 were once a single continuous layer; FIGS, lul ln->. Fractures and Faults. and so with the others; but at the time of fracture there was a dropping of the middle portion, so that along each fracture there is now a fault, or displacement?. Another ease is illustrated in Fig. 102; here as the fracture was UNCONFOBMABLB STKATA. 113 irregular in its course, the displacement has brought pro- jecting parts of the two sides together. Veins have often been rendered irregular in width, or entirely interrupted, in this way. Fig. 82 on page 1)8 is another example of such irregularities. The figures represent faults or displacements of only a few feet or yards; but in many faults, produced in the making of a range of mountains, the rocks of one side of a fracture have been pushed up, or have dropped down, thousands of feet. \Yheii fractures are very numerous in the rocks of a region, and iu parallel planes of great extent and regu- larity, and have the walls in contact or nearly so, they are called join I*. 4. Unconformable Strata. Hocks are often laid down hori- zontally o/w n/if i//-/ir'inii>(i/royre#is of life. There has been, as above intimated, a succession in the species of plants and animals that have lived upon the globe. Tin- curliest kinds were followed by others, and these by still others, and so on, through age after age, before the final appearance of Man. The plants and animals that lived in the successive periods left their relics that is, stems or leaves, shells, corals, bones, and the like in the mud or sand of the sea-bottom, seashore flats, and beaches, and in other deposits of the era; and these sand-beds and mud-beds are now the rooks of those periods. Hence in the rocks of one era AVC find different relics, or fossils, from those of the preceding or following era. Geologists have ascertained the kinds that belong to the successive rocks, or eras of the world; so that, if they come upon an unknown rock with fossils, in a country not before studied, it is only necessary to compare the fossils found with the lists already made out. For a long part of early time after life was abundant there were no fishes in the world. The discovery of a 124 HISTORICAL GEOLOGY. fossil fish in a bed of rock is evidence that the bed does not belong to the formations of that earliest time, but to one of some later period. After the first appear- ance of fishes the kinds changed with the progress of time; so that if, in the case of our discovery, we can ascertain the subdivision of the class to which our fossil fish be- longed, we can then decide approximately the age of the rock which afforded it. No herring, cod, and salmon are known to have existed until near the last of the geolog- ical ages; and if the species turned out to be related to these, we should conclude that the rock was among the later in geological history ; and a determination of the species might lead to the precise epoch to which it per- tained. Bones of beasts of prey, cattle, and horses are found only in rocks of the last two geological eras. Thus, owing to the succession of life on the globe, the geologist is enabled to arrange the fossiliferous rocks in the order of their formation, that is, the order of time. If a stratum in one locality contains 110 fossils, or if its fossils have been obliterated by heat producing metamor- phism, the stratum is traced by the geologist to another locality, with the hope of there discovering fossils, or at least of finding them in an underlying or overlying stratum. In this and other ways doubts are gradually removed, and the true succession in any region is made out. The history has thereby been divided into four grand sections : CLASSIFICATION OF ANIMALS. 125 I. ARCH^EAX TIMK; that is, Iwyiuniny time; the word Archaean is from the Greek for beginning. II. PALEOZOIC TIME, or the era of the ancient forms of life; Paleozoic being from the Greek for ancient and life. III. MESOZOIC TIME, or the era of mediceval forms of life ; Mesozoic, from the Greek, signifying middle and life. IV. CEXOZOK: TIME, or the era of the more recent forms of life ; Cenozoic signifying recent and life. Paleozoic, time, which was probably threefold longer than all later time, has been divided into five eras: (1) the CAMBRIAN; (2) the LOWER Sn.ruiAx; (8) the UPPER SILURIAN; (4) the I )K v< \ i A x ; and (/>) the C AKBOXK; ERA. The Cambrian and the Lower Silurian eras correspond to the REIGX OF TRILOBITES, the Upper Silurian and Devonian to the EEIGX OF FISHES, and the Carbonic, era to the REIGX OF AMPHIBIAXS. Mesozoic time corresponds to the REIGX OF REPTILES. Cenozoic time is divided into two eras, called (1) the TERTIARY, or ERA OF MAMMALS; and (2) the QUATER- XARY, or ERA OF MAN. The above-mentioned names of the grander divisions of geological time give a general idea of the progress in life. For its better appreciation a brief account is here given of the principal groups in the, classification of animals. Classification of the Animal Kingdom. The kingdom of Animals has five primary divisions Pro- tozoans, Radiates, Non-articnlates, Articulates, and Vertebrates. 126 HISTORICAL (JEOLOGY. 1. Protozoans. These are mostly microscopic species, with no differentiation into tissues and organs. Most of them have not even a mouth. In the typical Protozoans, the body consists only of a single cell. The Rhizopods (p. 48) and lladiolarians (p. oo) are here included. The word Protozoan, from the Greek, means frrxt or .s///jy;/<>.s/ . The Crinouls, represented on page 47, are other exam- ples of Radiate animals. o. No n- Articulates. 1. J/o//*>ro/V/.s. Molluscoids are di- vided into Bracliiopods and Bryozoans. A Bmchiopod has a pair of shells, or in other words, a shell consisting of two valves like a Clam, Scallop, or Oyster. But, as Figs. lOo to 112 show, the shells are sym- FK;S. KI.V112. -^.< no Brachiopods. Fig. 105, Waldheirala flavescens ; 106, loop of Terebratula vitiva ; 10", Terebratulina cai>ut- serpentls ; 109, Spirifer sti-iatus ; 109, same, showing interior of dorsal valve ; 110, Athyris coucentrica ; 111, Atrypa retleularis ; 112, same, showing interior of dorsal valve. metrical in form, so that a vertical line through the middle (Fig. 110) divides them into equal halves. Moreover, the valves are, respectively, dorsal and ventral, not, as in the Clam, right and left. Inside of the shell there is often a loop-shaped or spiral 128 HISTORICAL GEOLOGY. Rhynchonella psitta- cea, showing the spiral arms. arrangement for the support of a pair of spiral arms. In Fig. 113 one of these arms is rolled up spirally, and the other is FIG. us. extended out of the shell. The mouth is opposite the middle of the lower margin, whereas in a Clam it is at one end. Bryozoans are minute species, but they form compound groups, many of which re- semble Corals in form and stony texture. The animals look like polyps externally, as shown in Fig. 114, which represents them projecting out of their cells, enlarged to eight times their natural size. Fig. 114 a shows the animal wholly out of its cell and more enlarged. Fig. 115 is a a view of one of the delicate Cor- FH;S. 114, nr>. als, natural size; the dots show the positions of the little cells of the animal. The species are called Bryozoans, meaning moss- animals, the name alluding to the Corals, which are sometimes moss-like in delicacy and form. They also make crusts over shells and stones. Although so small, these Bryozoaii Corals arc a prominent constituent of some ancient limestones. 2. Mollusks. These are animals l:.ke the Oyster, Clam, Snail, and Cuttlefish; having a soft, fleshy, bag-like body, with sometimes an external shell for its protection, or an inter- 114 Bryozoans. Fig. 114, Kseliara, showing- animals extended out of their cells ( x s>; 1 14 , one of the animals remo\ rl | from its cell more enlarged ; 115, Ptilodictya feiiestrata, natural si/e ; llau, portion of surface of wiine enlarged. CLASSIFICATION OF ANIMALS. 129 nal bone or shell to give a degree of firmness to the fleshy body. The following are the principal groups : Lainellibranchs have bivalve shells as in the Clam, Mussel, FIG. 119. 117 FIGS. 116-118. 116 Mollusks. Fig. 116, LAMELLIBEANCH : Avicula Trentonensis ; Figs. 117, 118, GASTROPODS : 117, Murchisonia bicincta ; 118, Pleurotomaria lenticularis. and Oyster. Fig. 116 shows one of the Mussel-like species. They are called Lainellibranchs because the gills (or branchiae), which lie against the body on either side, are thin, lamellar organs. Gastropods include Snails and all i other species having a spiral shell and a single continuous chamber within, and also some species with shells of other forms, and some without shells. Figs. 117, 118 are examples. The name is from the Greek for venter, or the under side of the body, and foot, because the animals crawl on the ventral surface. DANA'S GEOL. STORY 9 Modern Pteropod. Styliola (x o). 130 HISTORICAL GEOLOGY. Pteropods, now represented only by a few small species, having thin translucent shells (or none), have often slender conical forms, and this was the common form in ancient time. As Fig. 119 shows, they are furnished with short paddles, which they put out for use in swimming. The figure repre- sents a species from the Gulf of Mexico, five and a half times its natural size. Cephalojwds, the highest of Mollusks, are so named from the Greek for head and foot, the feet or arms being arranged FIG. 120. Modern Cephalopod. The Calamary or Squid, Loligo vulgaris (length of body, 6 to 12 inches) ; i, the funnel through which the water and ink are thrown out; p, the "pen." around the mouth. The eyes are very large as in Fishes. In one division of them, that of the Squids and related species (Fig. 120), the animal has an internal bone (p) sometimes called from its form the pen, and no external shell. The body is inclosed in a bag or outer tunic, which is open a little distance back of the eyes, and the animal propels itself backward through the water by taking in and ejecting water from the bag. It has an ink-bag inside, to enable it CLASSIFICATION OF ANIMALS. 131 to becloud the water when pursued. The funnel, through which the Avater and ink are thrown out, is shown at ?', Fig. 120. The Nautilus (Fig. 121) is an example of a Cephalopod having a coiled external shell. FIG. 121. The figure presents a vertical section of the shell, and shows that it is divided by transverse partitions into a series of cham- bers. The animal occupies the outer chamber, but has organic connection with the interior Modem Cephalopod. through a membranous tube Nautilus (x j). called a siphuncle. In these chambers, the shells differ from those of Gastropods. 4. Articulates. These include Worms and Crustaceans, the water species, and Myriapods, Spiders, and Insects, the land species. They are distinguished by having the body and its members made up of joints or segments, articulate meaning jointed. Crustaceans include Crabs, Lobsters, Shrimps, and other spe- cies ; and are so named because they have a crust-like exterior which is sometimes called the shell. 5. Vertebrates. The higher and more typical Vertebrates have internally, along the back, a series of bones making together the vertebral column. In Fig. 122, representing one of the gigantic Mammals of ancient time, the vertebral column 132 HISTORICAL GEOLOGY. is seen extending from the head into the tail. Each separate bone of the column is called (from the Latin) a vertebra. The great nerve of the body, called the spinal cord, lies concealed in a tubular bone-sheathed cavity along the dorsal side of the column ; and on the ventral side of the column there are the ribs and the cavity for the stomach and other viscera. Some of the lower Vertebrates exhibit the characteristic vertebral skeleton only in a rudimentary state of development. Fro. 122. Vertebrate . Tinoceras Ingens. The principal subdivisions of Vertebrates are Fishes, Amphibians, Keptiles, Birds, and Mammals. 1. Fishes. The species breathe by gills. They have gen- erally two pairs of fins on the under surface, the pectoral and the ventral, corresponding to the two pairs of limbs of higher Vertebrates. CLASSIFICATION OF ANIMALS. 133 2. Amphibians, or Frogs and Soiamanden. Amphibians have gills in the young or tadpole state, and lose the same on becoming adult. In the change from the tadpole, or fish-like stage, to that of the Frog, there is a loss also of the tail ; but the Salamander retains the tail through life and thus has the form of a Lizard. All other Vertebrates breathe only by lungs. 3. Reptiles. Eeptiles have the body either naked or covered by scales or bony plates, and are oviparous. 4. Birds. Birds are covered by feathers and are also oviparous. 5. 3fa initials. Mammals suckle their young, as the word from the Latin implies. They are the highest of Vertebrates, and include Man as well 'as the Dog, Cat, Horse, Seal, and Whale. All animals that are not Vertebrates are called Invertebrat.es. In the Cambrian era and part of the Lower Silurian, the animals were all Invertebrates. In the table on page 125 the expressions Reign of Trilobites, Reign of Fishes, Reign of Reptiles, Reign of Mammals, etc., are not to be understood as implying that the several groups of animals mentioned were confined to the era named in connec- tion with them, but only that they were the most character- istic species of the era. Fishes began before the Lower Silurian era was completed, and continued on through geological time ; but until the close of the Devonian they were the highest of living species. Under the Eeign of Reptiles, the class of Reptiles, which 134 HISTORICAL GEOLOGY. began in the preceding era, had larger, more numerous, and higher species than before or afterward ; the era was emi- nently that of the Reign of Reptiles, the type having reached its maximum then ; that is, having culminated. Mammals of a low order called Marsupials existed in the Mesozoic, or during the Reign of Reptiles ; but during the Cenozoic, or the Reign of Mammals, Reptiles were compara- tively few, and ordinary Mammals were the highest and the dominant race. Again, the era of Coal-plants was not the only era in which coal-plants lived and coal was made ; but it was the era which was most remarkable for the making of coal-beds, and especially for coal-making plants of the tribe of Acrogens, the highest of Cryptogams, such as Ferns, Ground Pines or Lycopods, and Horsetails or Equiseta, which then grew to the size of tall shrubbery and forest trees. In later ages also coal- beds were made, but of less extent, and mainly out of other kinds of plants. The Carbonic era is often called the Era of Acrogens, and also the Era of Amphibians. During the progress of an era, changes of level, or catas- trophes of some other kind, have at intervals produced exten- sive disappearances of species over a Continental sea, and also abrupt changes in the kinds of rock-deposits in progress, if not also upturnings of strata. Such events are made the bases of subdivision of eras into periods and epochs. The following table gives a general view of the successive eras, with some of the subdivisions that have been adopted ; the first in time or earliest being at the bottom. TABLE OF GEOLOGICAL ERAS. 135 Eras. Subdivisions. [ 2. Quaternary AMERICAN. {3. Recent. 2. Champlain. ] BRITISH. Kecent. CENOZOIC.. j 1. Tertiary 1. Glacial. J ("3. Pliocene. Pleistocene. Pliocene. MESOZOIC. . . . Reptilian [ 1. Eocene. f 8. Cretaceous. Miocene. Eocene. Cretaceous. (Jurassic including 2 Oolvte [ 1. Triassic. 1. Lias. Triassic. PALEOZOIC. f. Permian. Permian. r 3 Carbonic . . J 2 Carboniferous Carboniferous I? Subcarboniferous. Mountain limestone. Portage and Chemung. ~\ i- 2. Devonian . . . {J r Hamilton. Corniferous. - Old red sandstone. u. Oriskany. J 1. U. Silurian.. ft, a Lower Helderberg. Ludlow group. Onondaga. 1 . > Wenlock group. Niagara. . ' 2. L. Silurian . . it Trenton. Llandeilo and Bala groups. Canadian. Arenig group. jj - ra. Later. 1 1 . Cambrian . . .2. Middle. L Cambrian. i * Early. ARCH^AN. The map on page 136 (Fig. 123) shows the positions of the rocks of the successive ages that are exposed to view over the eastern part of the continent of North America. The markings indicating the age of the rocks of the several areas are explained on the map. The black areas are the great coal areas of the continent. The portions left in white are areas of crystalline rocks which are partly Archaean and partly Lower Silurian. FIG. 123. ARCHAEAN TIME. 137 I. ARCHAEAN TIME. The first condition of the earth about which geology gives us any hint is that of a liquid globe, or a globe liquid at least at the surface, for mere pressure, it is now believed, would have made the interior solid. Evidence is found in the crystalline character of the oldest rocks; in the fact that many spheres in space, like the sun, are still in such a state ; and in the condition of the moon, which is like a globe that has cooled until its surface is all craters and scoria. Admitting that the earth has cooled from fusion, we are warranted in concluding that, whenever the vapors about the globe began to settle over the solidified but still hot crust, there to make oceans, the rocks exposed to the heated and acid waters would have been eroded by the chemical action of those waters, and by this means they would have been covered after a while with new rock deposits. Moreover, wherever rocks were within reach of the waves, whether emerged or submerged, the waves would have aided in making gravel, sand, and mud, and would have distributed the detritus in beds and strata. By such means the original rock of the cooled crust would have become nearly or entirely concealed by new rock for- mations. It is questioned whether any part of the original cooled surface is now exposed to view. The rocks made out of that crust, and not those of the original crust itself, are therefore the Archaean rocks of geology. 138 ARCHAEAN TIME. E.OCKS. The Archsean rocks of North America cover a large sur- face over the northern portion of the continent, and also some narrow areas elsewhere along the courses of existing mountains. In the map on page 139 (Fig. 124) the white areas are the regions of exposed Archaean rocks. The largest of them extends from Lake Superior northwest to the Arctic seas and northeast to Labrador. It has rudely the shape of the letter V, and Hudson Bay is included within the arms of the V. A peninsula stretching down from it into northern New York is the region of the Adiroudacks. An interrupted series of Archaean areas extends along the Green Mountains, the Highlands of New Jersey, the Blue Ridge of Pennsylvania and Virginia, the Black Mountains of North Carolina, and the region farther southwest. Another such series commences in Newfoundland and extends along Nova Scotia, New Brunswick, and near the coast of Maine. The map gives the positions of other areas to the west, the longest of which is that of the summit of the Rocky Mountains, including the Front or Eastern Range in Colorado, and extending north into British America. The arms of the great V, or original nucleus of the conti- nent, are approximately parallel respectively to the Atlantic and Pacific coast lines ; the other narrower areas follow the courses of the great mountain chains, and are parallel to the same lines. Geology thus affords proof that even in ROCKS. 139 Archaean time the great outlines of the continent were denned, and that all future progress was carried forward by working on the plan thus early laid down. The rest of the continent was under water (and perhaps also some FIG. 124. Archaean Map of North America. White Portions Archeean Rocks. of the ridges just referred to), but the rocks probably lay at no great depth. Archaean areas exist also in Scandinavia, Bohemia, Scotland, and some other regions. The facts prove that in Archaean time the ocean and continents were, in the main, already 140 ARCHAEAN TIME. outlined. "The waters" of the world had been "gathered into one place," and "the dry land" had "appeared." The Archaean rocks comprise gneiss and granite; syenyte, syenitic gneiss, and other hornblendic rocks; chlorite schist, mica schist, quartzyte, limestone, and other kinds. They include immense beds of iron ore, some of them 100 to 200 feet in thickness, vastly exceeding any of later time; for the Archaean was the Iron age in the earth's history. These beds of ore occur in northern New York, Canada, southern New York, northern New Jersey, North Carolina; in the Marquette region south of Lake Superior; in Missouri, where there are what are called Iron Moun- tains ; and in many other places. The FIG. 125. beds of ore (i, Fig. 125) lie between beds of quartzyte, gneiss, hornblendic gneiss, and other rocks of the era, Beds of iron Ore (i), Essex as illustrated in the annexed cut rep- County, New York. resenting a section in Essex County, New York. Hornblende contains much iron, and is a com- mon constituent of Archaean rocks. The rocks were for the most part originally sedimentary deposits ; for the gneiss and other schists, and also the quartz- yte, are, as explained 011 page 94, altered or metamorphic sedi- mentary rocks ; they were originally deposits of gravel, sand, and mud made by the ocean. The stratification in the gneiss and other rocks is in general the original stratification of the fraginental beds. The quartzyte differs but little except ROCKS. 141 in hardness from much sandstone. In Wisconsin some of the beds associated with the iron ores are scarcely at all crystalline, the metamorphic change having been slight. Like other sedimentary deposits, the rocks were laid down in horizontal beds. But they are now upturned at all angles, and often folded, showing thereby that, subse- quently to their deposition, they underwent the great dis- turbances that attend mountain-making. Fig. 126 shows the general condition of the rocks in the Archaean regions of FIG. 126. General View of Folds in the Archaean Rocks of Canada. Canada. The Archaean mountains, including the Adiron- dacks, the New Jersey Highlands, the mountains of Scandi- navia, and others, were made at the close of Archaean time, if not in part earlier. The original height of these moun- tains may have been many thousands of feet greater than it is now, for all the earth's agencies of destruction have been engaged in the work of leveling them ever since that first of the geological ages. Many Archaean crystalline rocks much resemble the crys- talline rocks of later time, and as both are without fossils they may be easily confounded. The occurrence of beds of iron ore scores of feet thick is one means of distinguishing areas of Archaean age. 142 AKCH^EAN TIME. Coarse syenitic rocks and labradorite rocks are character- istic of many Archaean regions, although not exclusively Archaean. Sure evidence of Archaean age is obtained when fossilifer- ous beds of the lowest Paleozoic formations are observed overlying unconformably upturned crystalline rocks, as in Fig. 127. Here the nearly horizontal Cambrian beds No. 2, FIG. 127. Section from South Side of the St. Lawrence, Canada, between Cascade Point and St. Louis Rapids. 1, Gneiss ; 2, Cambrian sandstone. with those above, were laid down after the beds below were made, and also after their upturning; and conse- quently the evidence that the latter belong to anterior time is unquestionable. LIFE. The earlier part of Archaean time was necessarily without life; for until the rocks and seas had cooled down to a tem- perature below that of boiling water (212 F.) life was not possible. Plants of the lowest orders can bear a higher temper- ature than the lowest of animals, and therefore were prob- ably the first living species. Some inferior kinds now live LIFE. 143 in waters having a temperature of 150 to 180 F., which is above the temperature that any animal life can bear. Much evidence from fossils as to the life is not to be looked for, because the rocks are so generally metamorphic. A supposed fossil Rhizopod has been called Eozoon, from the Greek for Dawn-life. But many question whether the speci- mens are not of mineral origin, and therefore not fossils. A few other dubious traces of fossils have been reported from some of the less metamorphic Archaean rocks. But probable evidence of plants is believed to be afforded by the great amount of graphite in some beds. Now (1) graphite is nothing but carbon, the essential principle of mineral coal, and (2) mineral coal was formed from plants ; moreover (3) mineral coal has been found in crystalline rocks converted into graphite. Here, then, is probable evidence of the exist- ence of plants. Any plants present were probably Sea- weeds, since the Cambrian has afforded relics of no plants but Seaweeds. Along with the true Seaweeds there were probably Diatoms, as these minute species are among the simplest of water-plants. The occurrence of limestone strata is also thought to favor the idea of the presence of plants or animals, since the limestones of the world are almost all of organic origin. Whenever the earliest plant, however minute, was created, a new principle was introduced, that of life, which is able to subordinate physical and chemical forces to its uses, and hold them at service until death occurs. At death, 144 PALEOZOIC TIME. chemical forces resume their ordinary work in the structure, and, by oxidation and other processes, destroy it. Progress in a system of life becomes from this time the subject of highest interest in the world's history. II. PALEOZOIC TIME. The foundations of the continents and their outlines having been established in Archaean time, work now went forward for their completion through further rock-making. The rock- making, as has been explained, was the work of the waves and marine currents, of the rivers and of the winds, and also of quietly acting chemical and physical agencies, in decomposing and disintegrating the rocks above the water's level, thus facilitating the work of the waves, rivers, and winds. In addition, living species were early in the seas, and contrib- uted, as they died, shells and other calcareous relics for the formation of limestones. During Paleozoic time the greater part of the rocks of the eastern half of North America were completed; and by the close of Mesozoic time, nearly all the rest had been made, and the great Interior seas of the continent had become dry land. Afterward, rock-making was carried on by the sea along the continental borders, and also over the Interior by freshwater agencies; and this work is still going on. The following are the subdivisions of Paleozoic time, begin- ning with the lowest : CAMBRIAN ERA. 145 1. EARLY PALEOZOIC. 1. CAMBRIAN era. (Reign of Trilobites. 2. LATER PALEOZOIC. 1. UPPER SILURIAN era. ") I Reign of Fishes. 2. DEVONIAN era. J 3. CARBONIC era. Reign of Amphibians, and the era of coal-plants or Acrogens. 1. Early or Lower Paleozoic. In the map on page 139 the shaded portion of the continent was probably for the most part covered with water at the close of the Archaean era, and was, therefore, the area over which the earliest Paleozoic beds may have been laid down. These beds were mostly, if not wholly, marine ; for no fresh- water deposits or fossils have yet been described from them. 1. Cambrian Era. The term Cambrian is derived from the old name of Wales. The Cambrian era is divided into three periods : (1) EARLY or LOWER CAMBRIAN ; (2) MIDDLE CAMBRIAN ; and (3) LATER or UPPER CAMBRIAN. ROCKS. The areas over which Cambrian rocks are now exposed to view border, to a large extent, the Archaean lands. The waves worked about these lands and there made the sand, DANA'S GKOL. STORY 10 146 PALEOZOIC TIME. gravel, and finer detritus out of which the rocks were to a large extent formed, part of them as beach deposits; part as beds over the bottom in deeper waters wherever detritus was distributed by the currents; and another part as lime- stones. Many of the sandstones, as the Potsdam sandstone, in northern New York, contain worm borings like those made by sea-worms in modern sandy shores (Fig. 149, page 152). Ripple-marks sometimes cover the layers, and footprints or trails of animals are occasionally met with. These bur- rows and markings are evidence that the rocks were made in shallow water or along beaches; that the work of rock- making was slow and quiet work, just like that along shal- low sea-borders of the present day; and also, that in the Cambrian era the tides and currents of the sea were no more powerful than now. None of the beds, so far as has been found, bear positive evidence of deep-sea origin. The beds occur in northern New York at the east foot of the Adirondack Mountains (which are Archaean) and along the borders of the Canadian Archaean ; along the Taconic range in eastern New York and western New Eng- land; in the Appalachian region at intervals from New York to Alabama; near the Archaean of Wisconsin and Minnesota ; in some parts of the Rocky Mountain region ; and as far west as the Sierra Nevada, in California. Far the larger part of the beds made in Cambrian time are now buried beneath the later formations. CAMBRIAN ERA. 147 Sandstones occur among the deposits of each of the Cam- brian periods, and so do limestones. The Potsdam sand- stone, at the foot of the Adirondacks, belongs to the Upper or Later division. Limestones of the Early Cambrian out- crop in northern Vermont and in many other regions. The great magnesian limestone of Missouri and some Other por- tions of the Mississippi Valley is in part Cambrian. In some regions that are now mountain regions the thickness of the Cambrian rocks is great, exceeding in some places 20,000 feet. In Great Britain Cambrian rocks are found in western Scotland and England, and in Wales and Ireland. LIFE. The seas of the Early Cambrian, although the earliest of Paleozoic time, abounded in life. The plants, as far as shown by fossils, were all Seaweeds. There were perhaps Lichens over the dry rocks of the land, but no traces of them have yet been found. The animals of which remains have been found are all marine. The species include Sponges (Fig. 128) and Corals (Figs. 129-131); and there can be no doubt that the Corals when alive were as beautiful, in their flower-like form (page 43) and color, as those of modern seas. There were also Crinoids, the primitive type of Echinoderms, having stems like plants (page 46). Fig. 129, on page 148, representing one of the Corals, shows the interior partly filled with the 148 PALEOZOIC TIME. rock in which the specimen lay buried. Fig. 130 is a side- view of an imperfect specimen of another Coral, and Fig. 131 a cross-section of the same. FIGS. 128-131. Sponge; Corals. Fig. 128, SPONGE: Leptomitus Zittelli; Figs. 129-131, CORALS: 129, Archwocyathus profundus; 130, 131, Spirocyathus Atlanticus. Other common species were the Molluscoids of the division of Brachiopods (Figs. 132 to 134), the most abundant of all Paleozoic fossils. There were also Mollnsks, of which three grand divisions were represented, that of Lamellibranchs or "Bivalves"; of Gastropods or Univalves (Figs. 136, 137, the former of a kind much like a limpet); and of Pteropods (Fig. 138). CAMBRIAN ERA. 149 FIGS. 132-134. 132 a. Brachiopods. The Lamellibranchs and Gastropods were few in species and very small ; but the Ptero- pods were very abundant and of much larger size than any now existing. More- over, some species had a lid, called an operculum (Fig. 138 a), for closing the open end of the shell; and in this respect were superior to Flg modern kinds (Fig. 119). (Billingsella) festinata. Worms are somewhat doubtfully represented by their tracks and bur- rows. The Crustaceans were represented by Trilobites, the highest life of the Cambrian world. The* name al- ^%^jk" '^Jij^ ludes to the three lon- gitudinal divisions into which the body is ap- parently divided. Fig. 139 represents, natural size, a species of the Early Cambrian. In Figs. 140 and 141 the forms of other Crustaceans are shown, the latter one of the Ostracoid or bivalve kind. Mollusks. Fig. 135, LAMELLIBRANOH : Fordilla Troyensis; Figs. 136, 137, GASTROPODS : 136, Stenotheca rugosa ; 187, Platyceras prima-vum ; Fig. 138, PTEROPOD : Hyolithes Americanus ; 138 a, operculum of 150 PALEOZOIC TIME. The two higher subdivisions of Crustaceans are the 10- footed (or Decapods, as Crabs, Shrimps, etc.) and the 139. FIGS. 139-141. 140. Trilobite. Olenellus Vermontanus. Phyllopod and Ostracoid Crustaceans. Fig. 140, PHYLLOPOD : Protocaris Mar- shi ; Fig. 141, OSTRAOOID : Aris- tozoe rotundata. FIGS. 142, 143. 142 143 Modern Tetradecapod Crustaceans. Fig. 142, Scrolls (x J); 143, Porcellio. 14-footed (or Tetradecapods, as the Sow-bugs and Sand-fleas). The Trilobites are most nearly related to the latter, and to that division of the 14-footed species called Isopods, illus- trated in Figs. 142, 143. CAMBRIAN ERA. 151 In the Middle and Later already mentioned, were con- tinued, and one new class un- der Mollusks was added, tha.t of the Cephalopoda. But the species found as fossils are nearly all different from those of the Early Cambrian. There were other Trilobites of va- rious genera. One of the larger kinds, from Braintree, near Boston, is represented in Fig. 144; it was ten inches long; another, of the same genus, from New Brunswick, had a length of fifteen inches and a breadth of eleven. Thus these Crustaceans were 145 FIGS. 145-148. Cambrian periods the groups FIG. 144. Brachiopods ; Gastropod . Figs. 145-147, BBACHIOPODS: 145, 146, Lin- gulella priuia (x 1) ; 147, Lingulepis anti- qua; Fig. 148, GASTROPOD : Holopea Sweeti. Trilobite. Paradoxides Hurlani (x J). almost as large as the largest of modern species, while the Mollusks that ap- peared in the Early Cambrian were all very small species. Figs. 145-148 represent a few fossils of the Upper Cambrian. Figs. 145, 146, 147 are shells of Brachio- 152 PALEOZOIC TIME. pods called Lingulella and Lingulepis, from the Latin lingua, tongue. The evidences of Worms in the Cambrian, and also through later time, are commonly either borings which are now filled with sandstone (Fig. 149), or the trails or tracks left on mud- beds by the crawling Worm (Fig. 150). FIGS. 149, 150. Worm-borings and Trails. DISAPPEARANCE OF SPECIES. The long Cambrian era closed, in eastern North America, without the intervention of a time of upturning or moun- tain-making to mark the interval between it and the following Lower Silurian era. The transition was gradual, the later beds overlying the earlier without marked unconformability. Still very few of the Cambrian species are known to occur in Lower Silurian beds. Moreover, very few species are known to pass up from the Lower Cambrian to the Middle Cambrian, or from the Middle to the Upper Cambrian. LOWER SILURIAN ERA. 163 2. Lower Silurian Era, The Lower Silurian era is divided into two periods: (1) the CANADIAN and (2) the TRENTON. ROCKS. The rocks of the Lower Silurian era are to a large extent limestones. 1. Canadian Period. During the earlier of the two periods, the "calciferous sandstone" was formed along the borders of the Archaean lands in northern New York a rock mostly without fossils. This was followed by the " Chazy limestone," which occurs at Chazy, on the west side of Lake Champlain and in western Vermont, and is in some places abundantly fossilif- erous. The St. Peter's sandstone of Iowa has been supposed to be of the age of the Chazy limestone ; but this is doubtful. 2. Trenton Period. The Trenton period is represented by the Trenton limestone, a great limestone formation which occurs widely over North America, both along the Appalachian border of the continent and throughout its interior. The Trenton period is the most extensive limestone-making period in the world's history. The limestone indicates that the waters over the Continental area were generally free from sediment, but not that they were deep waters, for modern coral reefs are formed of corals and shells within 100 yards of the surface. The Trenton limestone was named from Trenton Falls, on West Canada Creek, near Utica, New York, where the 154 PALEOZOIC TIME. gorge is cut through it. The Galena or lead-bearing lime- stone of Illinois and Wisconsin is Upper Trenton. Finally, in the later part of the Trenton period, lime- stone-making was confined almost wholly to the interior region ; for the Appalachian area, including New York, was receiving fragmental deposits as shales, sandstones, and conglomerates; and out of the niud-beds the Utica shales and Hudson shales were made at this time. They indi- cate some shallowing of the waters so that muddy sedi- ments were taken up and widely distributed. In Great Britain, the Lower Silurian has at base slates and sandstones of the Arenig series. Above them are the Llandeilo flags and the Bala group, corresponding nearly to the Trenton period. The thickness in Wales is stated to be 25,000 feet. LIFE. The seas abounded in life. The plants thus far found in North America are all Seaweeds ; but remains supposed to be those of land plants occur in Great Britain, which show that the hills and plains were already green. One of the Seaweeds is represented in Fig. 151 ; and in Fig. 152, a supposed land plant, near the modern Horsetail or Equisetum in its character. Nodules of coal occur in one of the forma- tions, which are supposed to have come from buried Sea- weeds, or else from animal material, or from mineral oil that has been derived from the decomposition of plants or animals. LOWER SILURIAN ERA. 155 The animals are chiefly marine Invertebrates, as in the Cam- brian. But before the close of the Trenton period there were FIGS. 151, 152. 152 Seaweed; Land -plant (supposed). Fig. 151, SEAWEED. Buthotrophis gracilis ; Fig. 152, LAND PLANT (supposed): Protannularia Harknessi. also Fishes, marine Vertebrates, and the earliest known of Insects. Among Protozoans there were Rhizopods and Sponges. FIGS. 153, 151. Polyp Corals. Fig. 158, Streptelasma corniculum ; 154, Columnaria alveolate ; 154 a, top view of same. The Radiates included Corals, Crinoids, and Starfishes. Fig. 153 is a side-view of one of the conical Corals of the Trenton limestone; the top has a cup-like cavity radiated 156 PALEOZOIC TIME. with calcareous plates, somewhat like Fig. 15, page 45; and the living polyp must have much resembled that of Fig. 16, except that it was circular. Another Coral, honeycomb-like in its columnar structure, and hence named Columnaria, is represented in Fig. 154. The cells are radiated, as shown in the figure, but in a vertical sec- FHJS. 155-158. Crinoids; Ophiuroid; Asterioid. Figs. 166, 166, CRINOIDS : 155, Pleurocystites fllitextus ; 156, Taxoerinus elegans ; Fig. 157, ASTERIOID : Palseaster matutinus ; Fig. 158, OPHIUROID : Ta-niaster spinosus. tion (as seen in such a section of one of the cells in Fig. 154) the cells are crossed by horizontal partitions. The cora) has been found in masses several feet in diameter. It had flower- like animals similar to those of Fig. 14, but smaller. Figs. 155-158 represent some of the Crinoids and Star- fishes. Fig. 156 is a Crinoid from the Trenton limestone, though not a perfect one, as the arms are broken off at the tips, and the stem below (by which it was attached to the rock LOWER SILURIAN ERA. 157 of the sea-bottom, and which may have been several inches long) is mostly wanting. Fig. 155 shows the form of another kind of Crinoid, one of very irregular shape, called a Cystid, from the Greek for hladdn: Its stem, when it was living, was run down into the inud of the sea-bottom, instead of being attached to a rock. The arrangement of plates on the body is irregular, and it has only two arms. Figs. 157, 158 are two of the Starfishes of the ancient seas. ico Brachiopods. Fig. 159, Leptona sericea ; 160, Orthis occidental ; 161, O. biforata ; 162, O. testudinaria. Brachiopods were very numerous. Some of them from the Trenton limestone are represented in Figs. 159 to 162. Bry- ozoans also were abundant. The earliest species of Cephalopods had straight shells, like that of a Nautilus (page 131) straightened out, whence the name Orthocems, meaning a straight horn. One, from the Trenton limestone, is represented in Fig. 163 ; it has partitions like those in the shell of the Nautilus. In the Orthoceras, as in the Nautilus, a tube called the siphunde, meaning little siphon, passes from the outer chamber through the partitions and all the chambers ; and the hole in 158 PALEOZOIC TIME. one of the partitions is shown in Fig. lfi.3 a. There were also coiled species of the group, in the Trenton formation. Cephalopod . Orthoceras junceum. The Articulates included Worms and Crustaceans, as in Cambrian time. One of the large Trilobites, an AsapJms, is represented in Fig. 164; its length was abouj 8 inches. FIGS. 164-166. 165 1U 165 a Trilobites. Fig. 164, Asaphus platycephalus ; 165 a, Calymene callicepbala ; 166, Triarthnis Beckil, the specimen showing the legs. Another common species, a Calymene, is shown, reduced to half the natural size, in Fig. 165. It is often found rolled into a ball (Fig. 165 a). Another species from the Utica slate, OBSERVATIONS ON THE EARLY PALEOZOIC. 159 a Triartlirm, is represented in Fig. 166; it shows that Trilobites had legs, although the specimens from most local- ities show none. There were also many species of Ostracoids, or Bivalve Crustaceans. The Insects of the Trenton period are known thus far only from two specimens, one found in Sweden, and one in France. As both are well authenticated, it is safe to con- clude that Insects were in great numbers over the land of all the continents. It is probable also that the land had its Myriapods, although the first specimen has not yet been found. Insects are little likely to become buried in marine deposits. Coming within reach of the seashore waves, they would at once be ground \ip. The earliest remains of Vertebrates have been found in Trenton rocks of Colorado. They are chiefly bony scales from the covering of Fishes. They are related to those found in rocks of the Upper Silurian and Devonian eras. (See pages 169, 179.) Observations on the Early Paleozoic. 1. Life. The life of the Early Paleozoic, as the preced- ing review shows, was almost all marine. It was made up largely of the best of limestone-makers, that is, species which secrete a large amount of lime carbonate, as the Crinoids, species consisting chiefly of calcareous disks ; Bryo- zoans, which are as much stone as the Crinoids; Brachio- pods, which have thick calcareous shells ; and Corals. These 160 PALEOZOIC TIME. kinds owe their fine preservation as fossils to their calca- reous skeletons. Other kinds, like Worms, and shell-less Mollusks and K-adiates, of which there were doubtless great numbers, left no record of themselves. The early species were largely stationary life, that is, were attached to the sea-bottom or some support. Such were all the Crinoids, Bryozoans, and Corals, and most of the Brachiopods. Moreover, some Mollusks, as the Mussels, live attached to rocks through life by a byssus of horny threads. The locomotive species were the Trilobites, Gas- tropods, Orthocerata and related Cephalopods, and the Fishes. The Cephalopods may have added much to the activity of the seas; for the species are not snail-like in pace, like Gastropods, but are fleet movers, like Fishes. Yet these ancient species, with their unwieldy shells, must have been slow compared with the naked Cephalopods of later time, and therefore easy game for the Fishes. 2. Mineral Oil and Gas. A large amount of mineral oil and gas is afforded in some regions by the Trenton formation and chiefly the limestone. At Findlay, and some other places in Ohio, borings are made to a depth of several hundred feet, through the overlying rocks, and then for 10 to 50 feet into the limestone; the gas comes up with a rush and continues to escape for years. From one boring over a million cubic feet of gas have been obtained per day. The gas is used both for lighting houses and for fuel. In other cases oil is obtained, which when purified becomes OBSERVATIONS ON THE EARLY PALEOZOIC. 161 kerosene. The oil and gas have nearly the same composi- tion, differing little from that of common burning gas. They were produced by the decomposition of the animal or vegetable substances in the rock, afforded by the dead plant or animal life of the seas. MOUNTAIN-MAKING. The close of the Early Paleozoic, that is, of the Trenton Period, was a time of upturning and mountain-making in North America, Great Britain, and Europe. The Taconic Mountains were then made, a range 500 miles long, extending along the western and northwestern border of New Eng- land, from Canada to northwestern Connecticut and Put- nam County in eastern New York. The rocks which originally included much limestone, and also various fragmental rocks, shales, sandstones, and con- glomerates overlying and underlying the limestone were pressed up into folds; and at the same time they were crys- tallized by the heat produced by the upturning, and thus changed to metamorphic rocks. The fossiliferous limestone was altered to white and clouded crystalline or archi- tectural marble, (of which Canaan in Connecticut, Lee in Massachusetts, and Rutland in Vermont afford noted exam- ples) ; the quartzose sand-beds, to quartzyte ; the mud-beds and shales to gneiss, mica schist, and other crystalline rocks. The upturned beds that were then made into a mountain range include all of the Early Paleozoic formations from DANA'S GEOL. STORY 11 162 PALEOZOIC TIME. the bottom of the Cambrian to the top of the Lower Silurian, and probably had a thickness in some parts exceeding 20,000 feet. As described for the Appalachian range on pages 114, 203, these beds were laid down over a gradually subsiding area, and the syncline or trough had a depth equal to the thick- ness of 20,000 feet. Thus the material for the mountain range was first deposited; and then the range was made out of this prepared material. In the West, where there was no mountain-making at this era, in Illinois the thickness of the Cambrian and Lower Silurian rocks is only 800 feet, and in Missouri only 2200 feet. It is probable, also, that another Taconic mountain range was formed at the same time, commencing in the eastern part of Canaan, Connecticut, and continuing southward through Westchester County, New York, to Manhattan Island; and still another, if not a continuation of the last, from the vicinity of Philadelphia to Buckingham County, Virginia (where the crystalline rocks have afforded fossils), and beyond this southwestward. The Taconic revolution, in this view, left its marks in mountains and in crystalline rocks along the whole Atlantic border, and the two or three Taconic moun- tain ranges constitute together a long Taconic mountain system. Moreover, a large part of this Atlantic border was simul- taneously lifted above the sea level. This is proved by the fact that along this border south of New York no marine deposits are known, either of the Upper Silurian, or of LATER PALEOZOIC. 163 any following formation earlier than the Cretaceous, the last period of the Mesozoic. In Great Britain the Lower Silurian formations, which are throughout conformable, are upturned so as to lie uncon- formably beneath the beds of the next era the Upper Silurian. The elevation of the AVestmoreland Hills, of the moun- tains in North Wales, and of the range of Southern Scotland from St. Abb's Head, on the east coast, to the Mull of Galloway, has been referred to this era. The max- imum thickness of the Lower Silurian rocks of Britain has been stated to be over 40,000 feet. 2. Later Paleozoic. It is stated above that a large part of the Atlantic border of North America was raised above the sea level at the time of the Taconic revolution. The ocean's waves and currents had had full sweep over this border in the Early Paleo- zoic, and had aided much in rock-making. Till now, the whole continent had been one great Continental sea, with a few islands over its surface. But the uplift placed a barrier to the Atlantic Ocean on the east, which extended south nearly to the Florida boundary; and after this epoch, in Later Paleozoic time, the waters of the Continental In- terior behind this barrier had to do their geological work without Atlantic aid. To the westward, these waters ex- 164 PALEOZOIC TIME. tended to the Pacific. To the southward there was complete connection, as before, between the Atlantic and Pacific. This eastern barrier of the continent is shoAvn on the map, Fig. 167. The Gulf of St. Lawrence was still outside the barrier, and marine channels or bays extended down from it over New England; but dry land made the barrier complete between New York and Canada. FI.I. 107. North America at the Opening of the Later Paleozoic. 1. Upper Silurian Era. The era of the Upper Silurian is divided into three periods. Beginning with the earliest, they are: (1) the NIAGARA, (2) the (KnNDAiiA, and (3) the LOWER HELDKBBEI;*;. UPPER SILURIAN ERA. 165 ROCKS. 1. Niagara Period. This period is especially noted for its great fossilii'erous limestone formation. It was named from its occurrence at Niagara Falls. The Niagara formation at Niagara River and elsewhere in western New York, and also along the region of the Appalachians, includes, Jirat, a thin laminated sandstone stratum, called the Medina sandstone; second, other sandstones associated with shales and limestones, the Clinton group, in which occurs, in many localities, a bed of red iron ore ; third, the Niagara shale and limestone, the strata at Niagara Falls, where the upper 80 feet are limestone and the lower 80 feet shale. Niagara shale has little extent to the west of New York, while the limestone spreads very widely, reaching into Iowa and Tennessee. The layers of the Medina sandstone often have ripple- marks, mud-cracks, wave-marks, and other evidences of mud- flat or sand-flat origin, showing that central and western New York, with the region to the southwest, was then an area of great mud and sand flats; but later these interior waters were more open and clearer; so that there was less sediment, and the life required for making limestone flourished. In Great Britain the Wenlock shale and limestone are of the age of the Niagara shale and limestone. They are in view between Aymestry and Ludlow, near Dudley, and else- where. The limestone, like the Niagara, is fidl of fossils. 166 PALEOZOIC TIME. 2. Onondaga Period. This period is noted for its salt de- posits. Its clayey rocks, without fossils, and its salt show that central New York, and the borders of Canada to the west, with part of Ohio, were then the site of great salt basins, where sea-water evaporated, impregnating the mud of the shallow sea with salt, or making deposits of rock salt. The brines of Salina and that vicinity in New York are salt- water wells, obtained by boring down to this saliferous rock. But farther south and west in New York and at Goderich in Canada, and also near Cleveland, in Ohio, there are beds of rock salt, some of them 40 to 80 feet thick. In the Ouondaga formation, and in the overlying Lower Helderberg, there occur occasionally large local beds of gyp- sum, or calcium sulphate. Part of these beds, if not all, were made by the action, on beds of limestone, of waters holding sulphuric acid. Some of them may be, like the salt-beds, the direct result of the evaporation of sea-water. There are many sulphur springs in the western part of New York, whose waters give out sulphuretted hydrogen (or hydrogen sulphide) which were produced by the decom- position of minerals containing sulphur in the rocks below; and not unfrequently sulphuric acid has resulted from the oxidation of the sulphuretted hydrogen, making acid springs. 3. Lower Helderberg Period. This period, which followed the Onondaga, was noted for a return of the conditions required for making fossiliferous limestone, showing that the waters had deepened over New York, especially to the eastward, that the UPPER SILURIAN ERA. 167 salt-making basins had consequently disappeared, and that once more there were clearer waters and abundant life. The name, Loiver Helderberg, is from the Helderberg Mountains, southwest of Albany, where the beds occur. The formation thins out to the westward in New York, being thickest in the vicinity of the Hudson Eiver valley. Moreover, it appears east of the river in Becrafts Moun- tain near Hudson, and probably extended northward to the St. Lawrence; for rocks of the period are found near Montreal. They appear to be evidence, therefore, that although the Avaters of the St. Lawrence Bay were cut off from those of New York during the Niagara and Onon- daga periods, the two were connected temporarily during this last period of the Upper Silurian. The beds also extend southwestward along the Appalachians. Following the Wenlock group in Great Britain there is the Ludlow group, consisting of sandstones, shales, and the Aymestry limestone, corresponding in age with the later part of the American Upper Silurian. LIFE. 1. Plants. The first American species of land plants have been obtained from beds of the Upper Silurian. The species were not Mosses, nor Grasses, but species of the Ground Pine tribe or Lycopods, the hiyJiest division of Crypto- gams. They are described beyond, in the account of the Devonian plants. 168 PALEOZOIC TIME. 2. Animals. Among the animals of the era there was the same preponderance of Corals and Crinoids among Radiates, of Brachiopods and Bryozoans, and of Trilobites among Crns- FIGS. 1CS-170. 170 169 Corals; Crinoid. Figs. 168, 169, CORALS: 168, Zaphrentis bilateralis ; 169, Halysites catennlatus ; Fig. 1TO, Cr.iNDiD : Iclitliyocrinus loevis. taceans, as in the Lower Silurian. There were also Fishes in the seas; and Scorpions, as well as Insects, over the hmd. A few figures of Invertebrates are here given. Figs. FIOB. 171-178. 173 Brachiopods. Fig. 171, Leptaena rhomboidalis ; 172, side view of Spirifer Niagarensis ; 173, Orthis biloba; 173 a, enlarged view of same. 168, 109, represent two of the Corals of the Niagara period ; Fig. 168, related to the Coral of the Lower Silurian, shown in Fig. 153; Fig. 169, a Coral imbedded in limestone, which UPPER SILURIAN ERA. 169 looks, in a section of the limestone, a little like a chain, or a string of links, and has hence been called Chain-coral. Fig. 170 represents one of the Niagara Crinoids. Some of the common Brachiopods of the Niagara group are represented in Figs. 171-173. The following are figures of two of the larger Trilobites. Both figures are reduced views, Fig. 174 being but one third the natural length, and Fig. 175 one fourth. FIGS. 174, 175. Trilobites. Fig. 174, Lichas Boltoni (xj); 175, Homalonotus delphinocephalua (x J). Of Insects only Cockroaches have yet been found. But these species had a better chance of preservation than most others because they frequent damp places; and this is a good reason for the survival of their remains. Eemains of Fishes have been found in the Onondaga beds. They are of the kind called Placoderms, having the anterior part of the body covered with bony plates, as illus- 170 PALEOZOIC TIME. trated in Fig. 176. Placoderms were common also in the Devonian. Remains supposed to be those of Fishes have also been found in the Clinton division of the Niagara. In England, Upper Silurian beds contain remains of Fishes related to the Sharks, and to the Ganoids. Ganoids differ from most modern Fishes in having bony scales or plates (Figs. 191-193). A few species are now living in Ameri- can rivers and lakes. The living species of the seas, as the transitions in the fossils of the successive beds show, con- tinued to change through the Upper Silurian era as well as through the Lower Silurian; that is, the species of the early part had nearly all disappeared and new species had be- come substituted before the later part of the era began; FIG. 1T6. Placoderm Fish. Restoration of Pala-aspis Americana. and each of the successive subdivisions in the rocks indi- cates some old feature lost during its progress or in the transition, and some new feature gained. The transition from the Upper Silurian to the Devonian era was gradual. 2. Devonian Era. The term Devonian was first applied to the rocks of the era in Great Britain by Sedgwick and Murchison, and al- DEVONIAN BRA. 171 lucles to the region of South Devon, where the rocks occur and abound in fossils. The era is divided into: (1) the EARLY or LOWER DEVONIAN, (2) the MIDDLE DEVONIAN, and (3) the LATER or UPPER DEVONIAN. The Devonian areas are those vertically lined on the North American map, page 136. ROCKS. 1. Early or Lower Devonian. The Lower Devonian forma- tion has, at its base, first, the Oriskany sandstone, which has most thickness in eastern New York, like the beds of the Lower Helderberg. Next follows the Corniferous limestone, which is the great limestone of the Devonian, just as the Niagara was of the Upper Silurian, and the Trenton limestone was of the Lower Silurian. It spreads through New York from the Helder- berg Mountains south of Albany, where it has been called the Upper Helderberg limestone, and stretches on westward to the Mississippi, and beyond into Iowa and Missouri. In New York and along the Appalachian region, it is under- laid by a sandstone or grit rock. The Corniferous limestone is in some places a coral-reef rock, as plainly as any coral-reef limestone in modern tropical seas. At the Falls of the Ohio, near Louisville, Kentucky, it consists of an aggregation of Corals, many of large size, and some are standing in the position of growth. The limestone often contains a kind of flint called horn- stone; and, as the Latin for horn is cornu, the limestone was thence named the Corniferous limestone. The Devonian de- 172 PALEOZOIC TIME. posits above this limestone are mostly sandstones and shales. 2. Middle Devonian. The Middle Devonian includes the Hamilton beds. They are mainly fragmented deposits in southern New York and along the Appalachian region to the southwest; but in parts of the Interior region they include limestones. The flagging stone so much used in New York and the adjoining states is an evenly laminated argillaceous sandstone, from the Hamilton beds at Kingston and other places on the Hudson River. 3. Upper Devonian. The Upper Devonian comprises the Portage and Chemung formations, which were thus named from localities in New York. They consist chiefly of sandstones with some shale in New York and Pennsylvania ; but in the Interior region the rock is mainly a black shale of little thickness. The Catskill red sandstone of eastern New York and Pennsylvania is a coarse sea-border formation, made dur- ing the Portage and Chemung epochs. In Great Britain the Devonian formation includes a great thickness of red sandstone in Scotland, Wales, and England, which was formerly distinguished as the "Old Red Sandstone." In South Devon there are lime- stone and shales in place of red sandstone, and hence a greater abundance of fossils. In the Eifel, Germany, the Eifel limestone is a Devonian coral-reef rock of the age of the Corniferous. Devonian sandstones cover a large area in Russia. DEVONIAN ERA. 173 LIFE. 1. Plants. The plants included, besides Seaweeds, various terrestrial kinds; and among them, in the middle and later Devonian, large forest trees. These early species were mostly the higher Cryptogams or FIGS. 177, 178. Ferns. Fig. 177, Neuropteris polymorpha; 178, Tree-fern, Caulopteris antiqua. Flowerless plants, but included also some Flowering plants. Of the former there were the following kinds : 1. Ferns. Some of them were Tree-ferns. A portion of one of the Ferns is shown in Fig. 177, and part of the stem of a Tree-fern in Fig. 178. 2. Eqiriffeta. The modern Equiseta, or Horsetails (the latter term a translation of the former) have striated jointed stems, which may be pulled or broken apart easily at the 174 PALEOZOIC TIME. articulations. The ancient species had a similar character. A portion of one of these rush-like Devonian plants is rep- resented in Fig. 179. One of the articulations of the stem is shown at ab. In allusion to its reed-like character it is called a Catamites, from the Latin calamus, a reed. The plant represented in Fig. 180 belongs to the Equisetum tribe; the word Asteropliyllites means star-leaf. FIGS. 179, 180. Equiseta. Fig. 179, Calamites (Archoeocalainites) radiatus ; 180, Asterophyllites latifolius. 3. Lycopods. The land plants most characteristic of the world in ancient time, were the Lycopods. The little trail- ing Ground Pines of our modern woods, so much used for decorating churches at Christmas time, are examples of Lycopods ; the close resemblance to miniature Pine trees gave origin to the name. The earliest of the ancient Lycopods were of small size, but some of those of the Middle Devonian were large forest trees. Fig. 181 repre- sents a part of the exterior of one of the Devonian Lyco- DEVONIAN ERA. 175 pods. The plants are called L<'/n'iiilc/nlri(Js (from the Greek for scale and tree), in allusion to a resemblance between the scarred surface and the scaly exterior of a reptile. The scars are the bases of the fallen leaves, and resemble the same on a dried branch from a Spruce tree. In the true Lepidoden- drids the scars are in alternate order, as illustrated in Fig. 181. In another group, called Sigillarids, the scars are in vertical series, as in Fig. 182. 4. Phcenogams, or Flowering Plants. Among the Flower- FIGS. 181-188. t I Si Lycopods; Gymnosperm. Figs. 181, 182, LYCOPODS; 181, Lei>idodendron primvum ; 182, Sigillaria Hallii; Fig. 183, GYMNOSPEBM : Cordaites Robbii. ing plants there were trees allied to the Yew, Spruce, and Pine, kinds having the simplest of flowers, and the seed naked instead of in pods. In allusion to the latter charac- ter they are called Gymnosperms, meaning having naked seeds. The flowers and fruit are usually in cone-like groups, and in allusion to the cones a large part of Gymnosperms are 176 PALEOZOIC TIME. called Conifers. Fig. 183 is a leaf of a Cycad, a subdivision of the group of Gynmosperins which includes the modern Cycas and Zamia. 2. Animals. Corals, Crinoids, Brachiopods, and Trilobites, were represented by numerous species, as in the preceding era. FIGS. 1S4-1S6. Polyp-Corals. Fig. 184, Zaphrentis gigantea ; 185, Phillipsastrsea Vcrneuili ; 186, Favosites Goldfussi. Three of the Corals of the coral-reef limestone (Corniferous limestone) from the Falls of the Ohio, near Louisville, are represented in Figs. 184-186. Fig. 184 represents a specimen of one of the large simple Corals, broken at both extremities, and showing above the radiating plates of the interior. The DEVONIAN ERA. 177 top, when perfect, had a depression Avhich was radiated with such plates, and to this the name of this ancient group of Corals, Cyathophylloids, alludes; it comes from the Greek for cup and leaf. Some specimens of the species are nearly three inches in diameter at top and a foot long; and, when living, the polyp or flower-animal when expanded was as large as a small-sized sunflower, and probably as brilliant in color. Fig. 185 shows the surface of a massive Coral whose polyps covered the surface like those of Fig. 14, on page 45. The other kind, Fig. 186, is one of the most common ; the struc- ture is columnar, suggesting that of a honeycomb, and hence its name, Favosites, from the Latin favus, a honeycomb. Among Cephalopods, besides species related to the Nautilus, or Nautiloids, there were other kinds of the tribe of Ammo- FK,. Cephalopod. Fig. 1ST, Goniatites luithrax. nites, or Ammonoids, a group which commenced just before the close of the Upper Silurian, and which is represented by very numerous species in Mesozoic time. The form of one of the Devonian species is shown in Fig. 187. It has the partitions or septa of the shell flexed, and hence the name Goniatites, from the Greek for angle. Besides the flexures on the sides shown in the figure, there is always one along the DANA'S GEOL. STORY 12 178 PALEOZOIC TIME. back of the shell. Moreover, the siphuncle, instead of being central, or nearly so, as in the Nautiloids, is close to the back of the shell. Among Crustaceans there were Barnacles and Shrimps. FIG. 188. Fio. ISfl. Crustacean. Palseopala'inon Newberryi. Fig. 188 represents the Shrimps from the Portage beds of the Upper Devonian. Besides marine species there were also Insects among ter- restrial Articulates. Fig. 189 represents a wing of one of the May-flies of the Devonian world; a gigantic species much exceed- ing any now known. It meas- ured five inches in spread of piatephemera antiqua. wings. The May-flies or Ephem- erae are species that live in the water during the young or larval state, and, when mature, fly in clouds over moist places. One of the Devonian species could make the shrill sound of a Locust. < DEVONIAN ERA. 179 The Vertebrates included, as far as now known, only Fishes. The remains of the Fishes are teeth; large spines that formed the front margin of the fins; scales; plates covering the head or the whole body of armor-clad species or Placo- derms, but never the entire backbone (vertebral column), as FIG. 190. Fin-spine of a Shark. this was mainly or wholly cartilaginous and not bony, and hence decayed on burial. The species included are (1) Sharks; (2) Gars, or Lepido- ganoids; (3) Placoderms; and (4) Dipnoans. The Gars and Placoderms are both included under the name Ganoids. 1. Sharks. The remains of the Sharks are either the teeth, che shagreen, or hard, rough-pointed covering of the body, or the large spines with which the front margin of the fins is sometimes armed. Fig. 190 represents one of the tin-spines of a Shark of the Corniferous period, two thirds the full length. The Shark was one of great size, as the length of the spine indicates. Some of the Sharks had rather blunt cutting teeth; but the most common kind, related to the living Cestracion of Australian seas, had a pavement of bony pieces over the inner surface FIGS. 191-193. 192 193 Scales of Ganoids. 180 PALEOZOIC TIME. of the lower jaw, making the mouth a formidable grinding apparatus, fit for cracking Brachiopods and the like. 2. Gars, or Lepidoganoids. The Gar-pikes of the Mississippi and the Great Lakes, now a rare kind of Fish in the world, are examples of the type of Fishes that was exceedingly abundant FIGS. 194-196. 194 Dipnoan; Ganoids. Fig. 194, DIPNOAN : Dipterus macrolepidotus (x J) ; Figs. 195, 196, GAXOIDS : 195, Holop- tychius; 195 a, scale of same ; 196, tail of a modern (homocercal) Ganoid. in species in the Devonian Age. The scales of Gars are bony and shining, unlike those of ordinary modern Fishes, and to this, Agassiz's name, Ganoid (from the Greek for shining), refers. In many species the scales are set side by side with DEVONIAN ERA. 181 FIG. 197. a special arrangement for interlocking at one margin after the fashion of the tiles on a roof; while in others they are put on more like shingles, or in the way common in ordinary fishes. Figs. 191, 192 represent two kinds of tile-like scales ; and 193, the under surface of two of the latter, showing how they are secured to one another. Fig. 195 represents a speci- men of the Ganoid fishes of the Devonian. Some of the Ganoids of the Middle Devonian whose remains have been found in Indiana and Ohio were of great size. One of them had jaws a foot to a foot and a half long, with teeth in the lower jaw (Fig. 197) two inches or more long. The teeth of Ganoids are usually very sharp. Sometimes they are small and fine, and grouped so as to make a brush-like surface ; but often they are very large and stout. The material of On >- chod 8 - the interior of the teeth, called dentine, is often intricately folded, and, in allusion to the passages of a labyrinth, such teeth are said to have within a labyrinthine structure. A simple form of this labyrinthine structure is represented in Fig. 198. 3. Placoderms. One of the Placo- Section of Tooth of Lepidosteus osseus - derms, a Cephalaspis, is represented in Fig. 199. Other species are shown in Figs. 200, 201. The body in Fig. 200 is incased in bony pieces, and the pectoral fins of the fish were like arms; but they made FIG. 198. 182 PALEOZOIC TIME. very poor limbs for a fish, as they were unfit for swimming, and could be used only for crawling over the bottom. FIG. 199. Cephalaspis Lyellii. 4. Dipnoans. These Fishes resemble the Ganoids in many respects, but differ in having the air-bladder devel- FIGS. 200, 201. 200 Placoderms. Fig. 200, Pterichthys Milled (x j) ; 201, Coccosteus decipiens (x \). oped as a lung, and the auricle of the heart divided into two. Fig. 194 represents a Devonian Dipnoan. The tail in DEVONIAN ERA. 183 Fig. 194 has a peculiarity that belonged to all of the ancient Fishes ; that is, the vertebral column extends to its extremity. In Mesozoic and Cenozoic species and modern Gars the ver- tebral column stops at or near the commencement of the tail-fin, as in Fig. 196. The facts reviewed with reference to the life of the Devonian teach that during the progress of the age the marshes and dry land were covered with jungles and forests ; that the trees were without conspicuous flowers, and the most of them with no true flowers at all; that the seas were brilliant with living Corals, as well as Crinoids, and abounded in Brachiopods and Trilobites; that they also had their great fishes, Sharks, Gars, and Placoderms. The land, too, had its swarms of Insects, and its Scor- pions and Myriapods, and perhaps also its Spiders to spread their webs for the May-flies, although no relics of them have yet been found. MOUNTAIN-MAKING. The Devonian age passed quietly for the larger part of the North American continent, without any tilting of the rocks; yet not Avithout wide, though small, changes of level, varying the limits and depth of the Interior sea, such changes of level and of limits being indicated by the varying limits of the rocks, all of which are of marine origin. This quiet was not interrupted between the Devo- nian and Carboniferous eras, so far as yet discovered, ex- 184 PALEOZOIC TIME. cept to the northeast in the region of New Brunswick, Nova Scotia, and northeastern Maine. There an upturning and flexing of the beds occurred, and, as a result, some moun- tain-making. The southward extension or growth of the dry land of the continent continued; and, by the close of the Devonian, the shore line probably crossed the southern portion of what is now New York State, where is the southern limit of the outcropping Devonian, so that all of Canada except the south- west extension north of Lake Erie, nearly all of New York, and much the larger part of New England, were above the sea level, together with Wisconsin and the borders of the ad- joining states. There was probably also a peninsula extending from northern Illinois to the Cincinnati region, and an island about an Archaean area in Missouri. See map, page !.'!<>. 3. Carbonic Era, or Era of Amphibians. The Carbonic era was the time when the most extensive coal-beds of America and Europe were made. The name Carbonic is from the Latin carbo, coal. ROCKS. 1. Subcarboniferous Period. The era commenced with a marine period, the Subcarboniferous, in which a large part of the North American continent was under the sea, though not at great depths, and Great Britain and Europe also were to a large extent submerged. During it, limestone strata, with some intervening sand-beds, were in progress in portions CAEBONIC ERA. 185 of Great Britain and Europe, and over much of the Mississippi basin or the Interior region of North America; and, at the same time, great fragmental deposits, making sandstones, shales, and conglomerates, were laid down along the Appa- lachian region from the borders of New York southwestward, the thickness of which was five times as great as that af the limestone strata. 909 FIGS. 202-204. Crinoids; Coral. Figs. 202, 203, CRINOIDS : 202, Woodocrinus elegans ; 203, Pentremites pyriformis ; Fig. 204, CORAL : surface of Lithostrotion Canadense. The map of North America 011 page 164, Fig. 167, gives a general idea of the Continental land and its great waters. The chief change that had taken place during the Upper Silurian and Devonian was a spreading of the northern shore line in New York far southward to, or nearly to, its southern boundary ; in Ohio, to and beyond the Cincinnati island (C, Fig. 167) ; and in Wisconsin to northern Illinois and Iowa. Farther south and west there was an open sea. 186 PALEOZOIC TIME. The limestone was formed to a great extent of Crinoids, and though Corals, Brachiopods, and other species contributed to its material, it has been called Crinoiilal limestone. The Crinoids were of numerous species and very various forms. One of the most perfect specimens is represented in Fig. 202, only the stem below being wanting. The figure shows the numberless stony pieces really blocks of limestone material of which it consists, and which ordinarily fell to pieces when the ani- mal died, as there was little animal membrane to hold them together. The animal opened out its arms at will, and when F:GS. 205, 206. 205 Brachiopods. Fig. 205, Splrifer increbescens ; 206, Productus punctatus. expanded, the breadth of the flower-like summit in this species was about three inches. The stem below, when entire, was probably a foot or more long. The little disks of which the stem of the Crinoid consists, looking like button-molds, are common fossils in the limestones. On page 50, Fig. 34, a piece of Crinoidal limestone is represented which consists almost solely of the broken stems of Crinoids. Some of CARBONIC ERA. 187 the stems are an inch in diameter. Pig. 203 represents a Crinoid without arms, called Pentremites. There were also Corals ; and a top view of the most com- mon of these is represented in Fig. 204. Brachiopods also were abundant ; figures of two of them are given in Figs. 205, 206. 2. Carboniferous Period. After the Subcarboniferous pe- riod began the true Coal period, or that of the coal-measures. The rocks of the coal-measures, which alternate with the coal-beds, are sandstones, shales, conglomerates, and occasion- ally, especially in the Interior region of the continent, lime- stones. At base, there is generally a conglomerate called the millstone-grit. The coal-beds are evidence of long periods of emerged land, free from briny waters, where marshy lands were densely covered with vegetation ; and the intervening fragmental and limestone strata prove a new submergence either beneath fresh waters or salt, and generally for the region west of Pennsylvania, the latter, as the fossils show. The geography of the continent during times of emergence and wide-spread foliage may be learned approximately from the map on page 136 (since at those times the Archaean and Paleozoic areas must have been mainly dry land) ; and the positions of the great coal-marshes, though narrowed by erosion and a covering of later strata, from the black areas on the map. The easternmost is in New Brunswick, Nova Scotia, and western Newfoundland; the westernmost, just west of the Mississippi, from Iowa to Texas ; the region 188 PALEOZOIC TIME. farther west continued to be an area of salt water, producing only marine Carboniferous rocks. The most northern area, the Acadian, covers part of New- foundland, Nova Scotia, and New Brunswick ; a second, of very small extent, is in Rhode Island ; a third, the Alleyliany, reaches from near the southern boundary of New York over part of Pennsylvania, Ohio, Kentucky, and Tennessee to Alabama ; a fourth is in central Michigan ; a fifth, the Eastern Interior, covers parts of Illinois, Indiana, and west Kentucky ; a sixth, the Western Interior, parts of Iowa, Missouri, Kansas, Arkansas, and Texas. The last two were originally one, but the Mississippi Valley now separates them. It has been estimated that the area of the workable coal-beds of the United States is at least 120,000 square miles. The coal area of Nova Scotia and New Brunswick is 18,000 square miles. The principal coal areas of England are those of South Wales ; the great Lancashire region east of Liverpool (B, Fig. 230, p. 212) and Manchester (C) ; the Derbyshire coal region farther east ; and on the northeastern coast, the Newcastle coal-field (D). There are also coal-fields in Scot- land between the Grampian range on the north and the Lam- mermoor Hills on the south ; and others, in Ulster, Connaught, Leinster (Kilkenny), and Minister, in Ireland. There are valuable coal-fields of smaller extent in Belgium, France, and Spain, and others in Germany and southern Eussia. The greatest thickness of the coal-measures in Pennsyl- vania is 4000 feet 5 in Illinois, 1200 feet; in Nova Scotia, CARBONIC ERA. 189 about 15,000 feet. In Great Britain it is 7000 to 12,000 feet in South Wales, and contains 100 beds of coal; 7000 to 8000 feet in Lancashire, with 40 beds of coal over one foot in thickness ; 2000 feet at Newcastle, with about 60 beds of coal. The aggregate thickness of the coal-beds of a region is not over one fiftieth of that of the coal-measures. The coal-beds vary in thickness from less than an inch to 30 or 40 feet. The "mammoth vein" of the anthracite region in Pennsylvania is 29 feet thick at Wilkesbarre; but there are some layers of shale in the course of it, a common, fact in all coal-beds. Some coal-beds contain too much earthy matter to be of any value. The mineral coal is of different kinds. That of eastern Pennsylvania and of Khode Island is anthracite, while that of the rest of the country is almost wholly bituminous coal. Anthracite is a firm, lustrous coal, burning with but little flame, while the bituminous coal, as that from Pittsburg and the states west, is less firm and usually of less luster, and burns with much yellow flame. The flame is due mainly to the fact that part of the carbon is combined with hydrogen (or with hydrogen and oxygen) into a compound that, when heat is applied, becomes a combustible gas. Some bituminous coals especially those compact coals, scarcely shining, called cannel coal afford 50 per cent or more of volatile matter; while anthracite yields very little, and this is mostly the vapor of water. Coals always contain some impurity, which is the "ash" 190 PALEOZOIC TIME. and " clinkers " of a coal-fire. This ash or earthy material was largely derived from the plants themselves, and for the best coals wholly so; but in other cases it is part of the detritus that was from time to time drifted over the beds of vegetable debris by the winds, or washed over by the waters. The coal-beds always contain a little sulphur, enough to give a sulphur smell to the gases from the burn- ing coal; and the most of it exists in the state of pyrite, a compound of iron and sulphur. The layer of rock under a coal-bed is often a clayey layer, called the underclay, and it is frequently full of the underground stems or roots of plants. The trunks sometimes project from the top of a bed of coal, as shown in Fig. 86, page 109. Many logs or great trunks lie in the strata that intervene between the coal-beds, which were once floating logs; and multitudes of ferns and flattened stems or trunks of these and other plants are often spread out in the shales, and especially in the bed of rock directly over a coal-bed. Moreover, the coal itself, even the hardest anthracite, has sometimes impressions of plants in it, and, more than this, contains throughout its mass vegetable fibers in a coaly state which the microscope can detect. Coal was made from plants, and each coal-bed was origi- nally a bed of vegetable material, accumulated in nearly the same way as the peat-beds of the present time. (See, on this point, page 57.) The plant-bed having increased until several times thicker than the coal-bed to be made out of CARBONIC ERA. 191 it, was finally covered with beds of clay or sand; and while thus buried it gradually changed to coal. Plants when dried are one half carbon the chief ma- terial of charcoal the rest being mostly the two gases, oxygen and hydrogen; after the change to coal, seven tenths to nine tenths or more of the whole is carbon. 3. Permian Period. The coal-measures are followed . in Europe by a series of red sandstones and clayey rocks or marlytes, with a magnesiaii limestone, constituting the Per- mian group so called from the district of Perm, in Russia. In North America the Permian rdcks include the sandstones and shales at the top of the coal-measures in Kansas, Penn- sylvania, and Texas. LIFE. 1. Plants. The plants were similar in general character to their predecessors in the Devonian age, though mostly different in species and partly in genera. Of the higher Cryptogams, called Acrogens (or upward growers, as the word from the Greek signifies), because they can grow into trees, there were, as in the Devonian, (1) Ferns, (2) Equiseta, (3) Lycopods; and of the Phsenogams, or flowering plants, Gymnosperms, or trees of the Pine and Cycad tribes. The trees and shrubs grew luxuriantly over the almost endless marshes of the continent, and spread beyond them, also, over the higher lands. The features of the vegetation and of the ordinary land- scape are shown in the following ideal sketch, Fig. 207. 192 PALEOZOIC TIME. The tree at the center is a Tree-fern, and there are smaller Ferns below. The tree near the left side is a Lycopod of the ancient tribe of Lepidodendrids ; in the left corner there PIG. 207. Carboniferous Vegetation. are Equiseta. The region is represented as a great marshy plain with lakes. The lakes of the Carboniferous era probably had their many floating islands of vegetation, carrying large groves like the floating islands of some lakes iu India. CARBONIC EKA. 193 A portion of one of the Ferns is shown in Fig. 208, and of another in Fig. 209. Fig. 210 represents one of the Equiseta, a species of Calamites (page 174); plants with jointed stems that grew often to a height of 20 feet, and Fiu. 208. w* Fern. Sphcnopteris Gravcnhorstii. sometimes were a foot in diameter, very unlike the little Horsetails of modern time. Fir;. 209. Wwlm^ Fern. Neuropteris hirsuta. The Lycopods, of the tribe of Lepidodendrids, had the aspect of Pines and Spruces, and were 40 to 80 feet or more in height. On some, the slender pine-like leaves were DANA'S GEOL. STORY 13 194 PALEOZOIC TIME. a foot or more long. Figs. 211, 212 show the scars of the outer surface of two of the Lepidodendrids arranged, as FIG. 210. Equisetum. Calamites canna'formis. usual, in alternate order ; and Fig. 213, those of a Sigillaria in vertical series. The resemblance of the scars in the latter FIGS. 211-213. 212 213 W it 3 V. W / 9 L Lycopods. Fig. 211, Lepidodendron clypeatum ; 212, Halonia imlchella; 213, Sijrillnria Sillimani. to an impression of a seal suggested the name SigiUarin, from the Latin sigillum, seal. The cones of the Lepidodendrids and the nuts of the CARBONIC ERA. 195 FIGS. 214, 215. 214 215 Gymnosperms also occur in the beds. Two of these nuts are represented in Figs. 214, 215. They are supposed to have belonged to trees related to the modern Yew tree. Many of the North American species of plants have been found also in Europe. There are also coal regions in the Arctic islands which have afforded some of the same species of plants that were growing in Europe and America, showing great uniformity in the climate of the era; a fact sus- tained also by the occurrence in the Arctic deposits of many fos- sil shells and corals identical with some then living in the seas of Europe and America. 2. Animals. The seas of the Carboniferous age abounded in Crinoids, Corals, and Brachiopods ; but in the group of Articulates, while there were many kinds of Worms and Crustaceans, Trilobites were few. Trilobites had been re- placed by other Crustaceans. Examples of the Crinoids, Corals, and Brachiopods of the earlier part of the era are figured on pages 185, 186. The land had its Insects, true Spiders, Scorpions, and Myr- iapods, and also its land Snails ; and among the Insects there were May-flies, Cockroaches, Crickets, and Beetles. A view of one of the May-flies, of natural size, is shown in Fig. 216 ; of Nuts of Gymnospenns. Fig. 214, Trigonocarpus tricuspida- tus; 215, T. ornatus ; 215 a, view of lower end of same. 196 PALEOZOIC TIME. the wing of a Cockroach, in Fig. 217 ; of a Spider, from Morris, Illinois, in Fig. 218 ; and of a Myriapod, from Nova Scotia, in Fig. 219. Fishes were in great numbers and of large size, and they belonged mostly to the two grand divisions that were espe- Fios. 216-219. Terrestrial Articulates. Figs. 216,217, INSECTS: 216, Miamia Bronsoni (x 1); 217, Eoblattina venusta, wing of a Cockroach ; Fig. 218, SPIDER : Arthrolycosa antiqua ; Fig. 219, CENTIPEDE : Xylobius sigillariae. cially characteristic of the Devonian, the /Sharks (called also Selachians, from the Greek for cartilage, the Sharks being fishes with a cartilaginous skeleton) and the Ganoiila. Some of the Sharks were larger than any modern species. One of the Ganoids of the coal-measures is represented in CARBONIC ERA. 197 Fig. 220. It has the vertebrated tail, characteristic of all Paleozoic fishes. Fig. 221 shows the form and size of the teeth of one of the Sharks of the Subcarboniforous beds of Illinois. Besides Fishes there were the first of terrestrial Vertebrates, Amphibians; and, before the close of the Permian, Reptiles. Footprints of an Amphibian have been described from the FIGS. 220, 221. 220 Fishes. Fig. 220, GANOID: Eurylepis tuberculatus, from the coal-formation in Ohio; Fig. 221, SELACHIAN : tooth of Carcharopsis Wortheni ; a, profile section of same. Subcarboniferons beds of Pennsylvania, indicating a large animal having a tail, the tail having made its mark on the mud-flat over which the animal marched. In the Carbonif- erous beds of Illinois, Ohio, and Nova Scotia, skeletons have been found. One of them, from Ohio, is represented in Fig. 222. It has the broad cranium that is found in the Frog and Salamander ; but while modern species have a naked skin, the Carboniferous kinds were furnished with scales and bony plates. They had also sharp teeth very much like those of Ganoid fishes. Fig. 223 represents the skull of one of the true Reptiles from the Middle Permian of Saxony. 198 PALEOZOIC TIME. No remains of Birds or of Mammals have yet been found in any Paleozoic rocks. CHANGES OF LEVEL DURING THE PROGRESS OF THE CAR- BONIC ERA. Changes of level were going on over the North American FIG. 222. continent throughout the era ; but they were alter- nating oscillations above and below the sea level and of the gentlest and slowest kind possible, not upliftings into mountains. Just such alternations of level had been in progress through all the preceding ages ; but the Carbonifer- ous movements were pe- culiar in this, that the continent over its broad surface was just balancing itself near the water's sur- face, part of the time bathing in it, and then out in the free air, and so on, alternately ; while in for- mer times, the oscillations seldom carried the Interior Continental region out of the water, or if they did, only portions at a time. It was peculiar also in the fact that , Amphibian . Pelion Lyellii. CARBONIC ERA. 199 the wide continent lay quiet above the sea level, with a nearly even surface, for very great periods of time, suf- ficiently long to make beds of vegetable debris thick enough for coal-beds. Many of the coal-beds are six feet thick, and some twenty or more ; and even six feet would require, accord- ing to an estimate that has been made, a bed of vegetable debris thirty feet thick for bituminous coal, and a much thicker one for anthracite. FIG. 223. Reptile. Skull of Pala'ohatteria longicaudata. The Interior of the continent from eastern Pennsylvania to central Kansas was a region of vast jungles, lakes with floating grove-islands, and some dry-land forests, and the debris of the luxuriant vegetation produced the accumulating plant-beds. A Cincinnati area of emerged land then divided the continental marsh from northern Illinois southeastward 200 PALEOZOIC TIME. through Kentucky ; but farther south the eastern and western portions were probably united. The Michigan coal area was an independent marsh region. The Green Mountains separated the Pennsylvania area from those of Rhode Island and Nova Scotia. The two latter were probably connected along the region of the Bay of Fundy and Massachusetts Bay and also with the coal area of western Newfoundland. The changes of level could hardly have carried up evenly all parts of the Interior marsh region from Penn- sylvania to beyond the Mississippi ; and it is evident that they did not, since it is difficult to make out the parallel- ism between the beds of the eastern, central, and western portions. The era of verdure during which a plant-bed was in progress finally came to its end by a return of the water over the Continental Interior destroying the terrestrial life ; and then began the deposition of sediment (covering up the plant-beds and making sandstones or shales or conglom- erates), or the forming of limestones. Over Illinois and to the south and west, the encroaching waters were salt; for the beds contain marine fossils. But over Pennsylvania they were most of the time fresh. Finally, the continental surface, or wide portions of it, again emerged slowly, putting an end to aquatic life, and opening a new era of verdure. Such alternations continued until all the successive coal-beds were made, some of them affecting per- haps the whole breadth of the Interior coal area, others GEOGRAPHICAL PROGRESS. 201 more local. Thus the era was one of constant change ; yet change so gradual that only a being whose years were thousands or tens of thousands of our years would have been able to discover that any change was in progress. In Nova Scotia the oscillations went on until nearly 15,000 feet of deposits were formed ; and in that space there are 76 coal-seams and dirt-beds ; and therefore 76 levels of marshes and verdant fields, between others when the waters covered the land. But over that region the waters sub- merging the region were mainly fresh or brackish waters, since no marine shells exist in the beds, while there are land and fresh-water shells and bones of amphibians. The area in the Carboniferous period was an immense delta at the mouth of the St. Lawrence, then the only great river of the continent, and the submergences were connected with the floods of the stream as well as with changes of level in the earth's crust. The Permian period, or the closing part of the Carbonifer- ous age, was an era of general submergence, without long eras of verdure or the formation of plant-beds. GEOGRAPHICAL PROGRESS DURING PALEOZOIC TIME. In the history of Archaean time the fact is brought out that the North American continent was largely outlined and the courses of its mountain chains determined before Paleo- zoic time began. Later history has shown that the continent- 202 PALEOZOIC TIME. making which followed was not a building up from deep-sea foundations, but a building outward over shallow Continental seas from the borders of the emerged Archaean lands, and largely within waters that had Archaean ridges as confines. Through the Early Paleozoic, rock-making reached to the borders of the Continental areas. But at the time of the Medio-Paleozoic upturning, when the Taconic Mountain sys- tem was made (see map, page 164), a broad sea-border bar- rier was produced by *an emergence which shut off the Atlantic. Consequently, no rock deposits were made during the Later Paleozoic along this border north of Florida, except in local gulfs over New England and Canada. Eock- making in eastern North America was largely Interior Conti- nental work. It produced a gradual extension of the founda- tion rocks westward, and finally their partial emergence. Over the Eocky Mountain slopes also there was rock-making ; but the larger part of western North America, even to the Pacific, continued to the end of Paleozoic time a wide sea. The Post-Paleozoic Revolution. From the beginning of Paleozoic time to its close all changes over the Appalachian region west of the Archaean ridges, southwest of New England, and over the great Inte- rior region of the continent, had gone on quietly. There were gentle oscillations of the surface and slight displace- ments, but nowhere a general upturning. These ages of quiet and regular work in rock-making POST-PALEOZOIC REVOLUTION. 203 were very long, for Paleozoic time includes at least three fourths of all time after the beginning of the Cambrian era. Over the Appalachian region from New York southward, the Cambrian, Silurian, Devonian, and Carboniferous deposits have great thickness. The maximum amount in Pennsylvania has been, estimated at 40,000 feet, or over seven miles. But over the Interior region, where limestones were the most of the time forming, the thickness is from 3000 to 4000 feet. These Appalachian deposits, ten times thicker than those of the Interior, were accumulating there for the making of a range of mountains; and at the close of the Paleozoic all was ready and the mountains were made. An account of the making of the Appalachian range has been given on pages 114, 115. It is there stated that the 40,000 feet of deposits were accumulated in a gradually forming trough made by the slow sinking of the earth's crust, the several rocks of the series bearing evidence that they were made in shallow waters. The last in the series, the Carboniferous and Permian beds, were spread out horizontally just above or just below the surface ; the coal-measures proving that there were wide emer- gences during their progress. The amount of subsidence, there- fore, was in some places 40,000 feet. The breadth of the trough was nearly 100 miles and its length about 900. The catastrophe consisted in (1) the folding, (2) the fractur- ing, (3) the solidifying, and in part (4) the crystallizing of the beds; and also (5) the change, in eastern Pennsylvania, of bituminous coal to anthracite. 204 PALEOZOIC TIME. The folds were numerous, and involved the whole breadth of the region; and if their tops had not since been worn off by the action of water, some of the folds would now rise over 10,000 feet above the sea level. Their characters are shown in Fig. 224, of a section from Virginia, extending FIG. 224. VI A/VIYIV HI IT" Section from the Great North, to,the Little North, Mountain, through Bore Springs, Virginia. from the southeast on the right to the northwest on the left, over a distance of six miles. It presents an example, FIGS. 225, 226. ..''"" "'-',"'' 225 Sections of the Coal-measures. Fig. 225, on the Schuylkill, Pa. ; P, Pottsville on the Coal-measures ; 14, the Coal-measures ; 13, Subcarboniferous ; 12-8, Devonian formations ; 7, 5, Upper Silurian ; 4, 3, Lower Silurian ; 2, Cambrian. Fig. 226, Anthracite region, near Nesquehoning, Pa. ; the black lines coal-beds. as explained on page 110, of the denudation the country has undergone, as well as of the folding. The coal-formation was involved in the folds, a fact which proves that the folding began after the coal-beds were formed. Fig. 225 is a section of the vicinity of Potts- POST-PALEOZOIC REVOLUTION. 205 ville, Pennsylvania, P being the position of Pottsville on the coal-measures. Fig. 226 represents another from near Nesquelioning, Pennsylvania, showing the anthracite beds doubled up, and in part vertical. The folds are steepest and most numerous to the south- eastward, or toward the ocean, and diminish to the north- westward (see Fig. 224). The folds generally have the western slope steepest, as if pressure from the direction of "the ocean had pushed them westward ; and sometimes the tops have thus been made to overhang the western base (Fig. 225). Section of the Paleozoic Formations of the Appalachians, in Southern Virginia, between Walkers Mountain and the Peak Hills (near Peak Creek Valley.) F, fault ; n, Lower Silurian limestone ; b, Upper Silurian ; c, Devonian ; d, Subcarbon- iferous, with coal-beds. The rocks were also fractured on a grand scale, and those of the eastern side of the fracture shoved up so as to make faults in some cases of more than 10,000 feet. Fig. 227 represents one of these great faults. The fault is at F; to the right of F, at d, is the Subcarboiiiferous, and to the left, a bent-up Lower Silurian limestone; so that a Lower Silurian rock is brought up to a level with the Subcarbon- iferous, a lift, according to Lesley, of 20,000 feet. 206 PALEOZOIC TIME. The rocks were solidified through the aid of the heat caused by the movement of the rocks; and by the same means the change of the coal to anthracite was caused. This change to anthracite took place where the rocks are xip- turned or disturbed, and therefore where more or less heat had been produced by the movements. While there was so much folding and fracturing, there was no chaotic confusion of the rocks produced, the stratifi- cation being perfectly retained. It follows from the facts (1) that the force acted quietly, or with extreme slowness, for otherwise confusion would have been produced ; and (2) that the pressure acted from the direction of the ocean, the forms of the folds, and their great numbers and steepness in that direction, proving this. On page 115 all this folding, faulting, and uplifting is at- tributed to lateral pressure caused by the earth's slow con- traction from cooling. Owing to this pressure, and the weakening of the bottom of the great trough or syncline by the high heat of the earth's interior, there was a yielding below and a collapse, and thereby a pressing together of the thick deposits, folding and breaking them; and also a raising of the upper surface above its previous level, because the width of the base on which they rested was narrowed by the collapse. Besides an Appalachian range, there was made at this time in eastern North America a Nova Scotia range from Newfoundland to Rhode Island, since largely denuded; and POST-PALEOZOIC REVOLUTION. 207 in Arkansas a Ouacliita range. The three constitute the Appalachian Mountain system. The end of Paleozoic time was thus marked by the making of great mountain ranges. Beyond this there was the emer- gence of the eastern half of North America, leaving the western half under water for completion and emergence at the close FIG. 228. Map of North America after the Post-Paleozoic Revolution. of Mesozoic time, as exhibited on the accompanying map, Fig. 228. Mountains were made in Europe and Great Britain at the same time with those of the Appalachian Mountain system, so that the close of Paleozoic time has its mountain boundary elsewhere besides in America. 208 PALEOZOIC TIME. CHANGES IN PALEOZOIC LIFE AT THE CLOSE OF THE ERA. In Paleozoic time Crinoicls, Brachiopods, Cyathophylloid Corals, Orthocerata, Trilobites, vertebrate-tailed Ganoid Fishes, among animals, and Lepidodendrids, Sigillarids, and Calamites, among plants, were characteristic species in each of the classes to which they belong. With the close of it, Trilobites, Lepi- dodendrids, and Sigillarids became extinct ; Cyathophylloid Corals, Orthocerata, and vertebrate-tailed Ganoids nearly so; and, afterward, Brachiopods among Molluscoids, and Crinoids among Radiates, were greatly inferior in numbers and impor- tance to other types of more modern character. It is thus that the Paleozoic features of the world passed by. The characteristics of the following age, the Mesozoic, had in part appeared before the Paleozoic ended ; for Shrimps and perhaps Crabs, the highest of Crustaceans, had appeared, and Ammonoids among Mollusks; and Spiders and Insects, some of the latter even emulating large Birds in size, they having a spread of wing of two or three feet. There were also, along the water margins, Amphibians and the earliest of Reptiles, as precursors of Mesozoic life. Moreover, among plants, Cycads, which had their maximum display in Mesozoic time, were well represented by their earliest species in the later Paleozoic. The extinction of species at the close of the Paleozoic was so nearly universal that, thus far, no species of the Permian period have been found in rocks of later date. But the rocks REPTILIAN ERA. 209 now in view were those that were made over the Continental seas, and, more correctly, over only portions of those seas ; and hence they give no facts as to the species of the ocean, but an imperfect record of those of the Continental seas. III. MESOZOIC TIME. MESOZOIC TIME, or the Keptilian era, is divided into three periods: (1) the TRIASSIC, named from the Latin tria, three, in allusion to the fact that the rocks in Germany have three subdivisions; (2) the JURASSIC, named after the Jura Moun- tains between France and Switzerland, (3) the CRETACEOUS, named from the Latin creta. chalk, the formation including the chalk-beds of England and Europe. The Mesozoic areas, on the map, page 136, are lined obliquely from the left above to the right below. 1. Triaash' . tive tracks of the hind feet of one of these bipeds wen- laid open in 1874 at the Portland juarries, Connecticut. The feet, as is shown in the figure, were 4-toed. Other species made 3-toed tracks with their hind feet, bird-like, as represented in Fig. 249. The tracks of Amphibians also occur in the same region, and the hind and fore feet of some of them are represented in Figs. 246, 246 a, and 247, 247 a. All the Amphibians, there is reason to believe, had large teeth and scale-covered bodies, like the Amphibians of the Carboniferous age. A tooth of a related four-footed species from Europe is shown two thirds the natural size in Fig. 250. The head of the Amphibian that was thus armed was over two feet long, and three fourths as broad. Skeletons also have been found of the Triassic and Jurassic Reptiles. In view of the large size of many of the species one division has received the name of Dinosaurs, from the Greek for terrible and lizard. The tracks of Figs. 248, 248 a, and 2-4 <). 249o, were probably made by Dinosaurs. The spe- cies had long legs, not the creeping legs of Lizards and Crocodiles; and part of them, as the tracks sho\v, walked in biped fashion, like Birds. Moreover, many of the bird-like kinds have the hind feet 3-toed, and so precisely like those of Birds that they were at first called bird-tracks. The restored skeleton of one of the Reptiles of the C'on- Amphibians. Tooth of Mastodon- saurus. (x J). REPTILIAN ERA. 221 necticut Valley, having hind feet with three well-developed toes, the innermost toe being small, and the outermost rudi- mentary, from a quarry not far from Hartford, is represented one twelfth the natural size in Fig. 251 ; and in Fig. 252, one FIG. 251. Dinosaur. f Anchisaurus colnrns Marsh (x ,'5). of the 5-toed Reptiles, quadruped-like in locomotion, and 30 feet long, from the Jurassic beds of the Rocky Mountains. The Megcdo9Ofjer was a related huge carnivorous species 25 222 MESOZOIC TIME. to 30 feet long ; and the Iguanodons and Hadrosaurs, equally large, were vegetable eaters. The resemblance of the bipedal Dinosaiirs to Birds was not merely in attitude and external form, but extended to a number of anatomical details in the pelvis and the hind limb. FIG. 252. Dinosaur. Restoration of Brontosaurus excelaus (x 5*5). Other Reptiles of the time were Crocodilians, Lizards (Lacertilians), and Turtles (Chelonians). Besides these, large Sea-saurians, whale-like, lived in the Fit;. 253. Ichthyosaurus tenuirostris. waters, and flying kinds shared the air with the Birds. The Sea-saurians had paddles like Whales and were 12 to 50 feet long. The Ichthyosaurs, or, as the name (from the REPTILIAN ERA. 223 Greek) signifies, Fish-lizards (Fig. 253), had a short neck, very large eyes, and thin vertebrse that were concave on both sides, resembling those of Fishes. Recently discov- ered specimens have shown that they possessed a large caudal fin, and smaller tins along the back, giving the body an aspect even more fish-like than that of the Whales. FIG. 254. Sea-saurian, Plesiosaurus dolichodeirus (X B \J). a, one of the vertebrae ; b, profile of same. Another kind, the Plesiosaur (meaning, somewhat like a lizard), had a long snake-like neck as represented in Fig. 254, with a short body, and vertebrae as long as broad (Fig. 254 a, 6). The long neck made it good at catching fish for food. The flying Reptiles were called Pterosaurs (from the Greek for wimjed saurian). One of them is represented in Fig. 255, somewhat less than the natural size. The wing, as the figure illustrates, is made by the elongation of one of the fingers and the expansion of the skin from the side of the body. 224 MESOZOIC TIME. Another species, from Solenhofen, Bavaria, had a long tail, with a bladed extremity, for use as a rudder ; it is represented on the wing, in Fig. 256, from a restoration by Professor Marsh. FIG. 255. Pterosaur. Pterodactylus spectabili.s. Of Triassic and Jurassic Birds, all that is known conies from two imperfect feathered skeletons found in the Oolyte REPTILIAN ERA. 225 of Solenhofen, and a fragment of a skull from Wyoming. Yet, as the remains of Birds are the rarest of fossils because they are fragile terrestrial species, and good food for all carnivorous life these few specimens are good evidence that not only Europe, but also the other con- tinents, abounded in Birds during the Jurassic period, if not earlier. These early Birds were reptile-like in having teeth, and a long vertebrated tail; but the tail was feath- ered, it having a row of large feathers along either side; FK;. 256. Rhamphorhynchus phyllurus (x J). they also had the metacarpal bones free, as in Reptiles, not grown together, as in modern Birds. Remains of Mesozoic Mammals have been found in the Triassic beds of Germany and North Carolina, and in the Jurassic of England and Wyoming. Fig. 257 represents a jaw-bone from Xorth Carolina, twice the natural size. The species are of the lower divisions of Mammals, the Monotremes and Marsupials, and they are all small, like Rats and Mice. Examples of modern Marsupials are the Kangaroo of Australia DANA'S OEUL. STORY 15 226 MESOZOIC TIME. and the Opossum of America. They are f'itii-(n-ijHii'ons species, that is, kinds whose young are in an immature state when born, approximating in this respect to the egg-stage, an egg being an example of extreme immaturity. They are Fl( . . i: - peculiar in having a pouch (marsupium, in Latin), on the under side of the body, for receiving the immature Dromatherium sylvestre. yOUllg. Ill addition to Mar- supials, there were the still lower Mammals, the Mouotremes, related to the modern Duck-bill, or Ornithorhynchus, of Australia, which is actually oviparous, and lays its eggs in holes along the banks of streams. The Oniitliorhynchus has the bill and aquatic habits of a Duck. Thus, before the close of the Jurassic period, the world had its Birds and Mammals; yet Reptiles still had su- premacy in magnitude, numbers, and diversity of kinds. 2. Cretaceous Period, or Later Mesozoic. ROCKS. At the opening of the Cretaceous Period a subsidence of the Atlantic borders south of New York, and of the bor- ders of the Gulf of Mexico was begun. At first, fresh- water deposits, called the Potomac formation, were made along the coast. But afterward, during the Middle and Later Cretaceous, as the subsidence increased, the waters of REPTILIAN ERA. 227 the Atlantic spread over the border, and beds with marine fossils were made. This reappearance of marine conditions along the old coast was a great event in geological history ; for the last pre- ceding marine beds over the coast region were those of the Lower Silurian. North America in the Cretaceous Period. Vertical lining indicates submergence during the Lower Cretaceous ; horizontal lining, sub- mergence during the Upper Cretaceous ; cross-lining, submergence throughout the ( 'retaceous. The marine beds, moreover, spread widely over the north- ern and western border of the Gulf of Mexico ; up the Mississippi Valley, to the mouth of the Ohio; from Texas 228 MESOZOIC TIME. northward over Kansas and a large part of the eastern slope and summit region of the Rocky Mountains, and prob- ably to the Arctic Ocean. They extended also over the Pacific border west of the Sierra Nevada. The outline of the continent at the time these marine beds were in progress is shown on the map on page 227, Fig. 258, the shaded portion being the part of the land that was then under sea-water, receiving Cretaceous deposits. The Cretaceous beds comprise gray and green sandstones; compact shell-beds and " rotten " limestone ; hard compact limestone and chalk in Texas and western Kansas; coarse sandstones and conglomerates ; large beds of clay ; and ex- tensive coal-beds. The clays in New Jersey, called Amboy or Earitan clays, are partly pure white clays, and are used for making pot- tery and tiles, as well as fire-bricks. Other kinds burn red because they contain iron, and these are used for common bricks. The greensand of the Cretaceous is valuable as a fertilizer. Another common material of the beds, and espe- cially of the chalk, is flint, as already explained. The coal-beds occur in the Upper Cretaceous. The coal is good bituminous coal, much like that of the Carboniferous period, and is mined at many places in Colorado, Utah, Montana; and also to the north in British America and to the west on Vancouver's Island, in British Columbia. REPTILIAN EKA. 229 LIFE. The Cretaceous period, the last of the Mesozoic, was a time of transition in the world's life, the Vegetation, the Fishes, and the Birds coming out under more modern forms, and Dino- saurs, Pterosaurs, and Ammonoids ending with it their career. FIGS. 259-262. Angiosperms (or Dicotyledons^. Fig. 259, Liriodendron primcevum ; 2GO, Sassafras crotaceum ; 261, Liiiodendron Meekil; 262, Sallx Meekii. 1. Plants. The great changes in the vegetation consisted in the introduction (1) of Palms and other related species, and (2) of plants of the tribe of Angiosperms. 230 MESOZO1C TIME. The Angiosperms include the Willow, Elm, Maple, Currant, Rose, and thousands of species that are especially character- istic of the forests and prairies of the present day. They are called Angiosperms from the Greek for vessel and seed, the seeds being covered, as that of the Pea or Bean in its pod, of the Walnut in its husk, and so on. Leaves of some of the species are represented in Figs. 259- 262. The leaves of Angiosperms are distinguished from those of Cycads, Conifers, and Palms by their network of 263 264 FIGS. 263-266. a 265 L Rhizopods. Fig. 263, Lituola nautlloides ; 264, a, Flabellina rugosa ; 265, Chrysalidina gradata ; 265, a, Cuneolina pavonia. veins. In the early Cretaceous, Cycads and Conifers were far the most abundant species ; but subsequently Angiosperms became the common kind and especially those of the genera Liriodendron, Magnolia, Sassafras, Myrtle, Plane tree (Platanus), with later the Maple, Elm, Oak, Beech, Pop- lar, and other kinds. At this time appeared also the first of Palms. The change was great in the foliage of the forests, and the world was also adorned for the first time with beautiful flowers, and enriched with edible fruits, a promise of the REPTILIAN ERA. 231 better time when Birds and Mammals should be at the head. 2. Animals. Among Protozoans, Rhizopods were very effi- cient species in rock-making, the chalk consisting chiefly of their minute shells. A few of the species are represented, much enlarged, in Figs. 263-266. FIGS. 267, 268. Cephalopoda. Fig. 26T, Scaphites Conradi ; Fig. 263, series of pockets in Ammonites (Placenticeras) placenta. Mollnsks continued to include great numbers of Ammonoids, and Belemnites. One of the former is shown in Fig. 267, and the pockets in the partitions of the shell of another common species in the dark parts of Fig. 268. 232 MESOZOIC TIME. Fig. 269 shows the form and size of a very common Belem- FIG. 269. nite from the Cretaceous beds of New Jersey. Fishes were represented still by Sharks and Gan- oids. But with these existed the earliest unques- tionable examples of the modern type of Fishes called Teleosts, so named from the Greek for com- plete and bone, the skeleton being bony throughout, instead of partly or wholly cartilaginous. Salmon, Perch, Herring, Mackerel, were among these earli- est of Teleosts. The tribe includes nearly all the Fishes in modern waters excepting the Sharks and related kinds. Reptiles were represented by various Dinosaurs, Crocodilians, Turtles, Sea-saurians, and Flying Saurians. Among the Dinosaurs there were the Horned Dinosaurs, having horns like those of Cat- tle (Fig. 270) ; for the horns represented in the figure are the cores of the actual horns. The species here figured was 15 feet long. There were also Sea-ser- 1 opo ' pents, called Mosasaurs, which swam by means of Belemnitella Americana, paddles and were 15 to 50 feet long. The Flying Saurians, or Pterosaurs, resembled much those of the Jurassic ; but some of them were without teeth, like Birds. The largest had a spread of wing of 25 feet. Birds were advanced in structure through the loss of the low-grade member, a long tail, and in acquiring the modern REPTILIAN ERA. 233 structure of the hand. But some of them still had teeth along the jaws, much like those of a Reptile (Fig. 271), and FIG. 270. Dinosaur. Restoration of Triceratops (x 3*5 X some had biconcave vertebrae like a Fish. Among the tooth- less Birds were Cormorants and Waders. FIG. 271. Bird. Jaw of Hesperornis regalis, showing the teeth. Mammals continued to include, as far as discovery has gone, only the feeble Marsupials and Mouotrem.es, and the fossils are mostly jaws, much like that figured on page 226. PROGRESS ix LIFE DURIXG THE MESOZOIC. Thus all the classes of Vertebrates had, in Mesozoic time, their species. In the Triassic, its first period, the Amphibians passed their climax in mnnbers, size, and grade, little being 234 MESOZOTC TIME. afterward known of the huge, scale-covered tribe. But during the following periods Eeptiles had their time of greatest ex- pansion, the earth, air, and waters being in their possession. The Birds and Mammals which appeared in this age were only the commencement of tribes that were to reach their fullest display in later time. Cattle and all other Placental Mam- mals that is, all ordinary Mammals were still in the future. The old law of change characterized the life throughout Mesozoic time. New fossils are found in every successive rock-stratum, and also older kinds are missed. The system of life was in course of expansion by the introduction of new species and a casting off of the old. MOUNTAIN-MAKING IN MESOZOIC TIME. The Sierra Nevada and some ranges to the north in British America were made at the close of the Jurassic. The strata of the mountain region to the top of the Jurassic were folded up in the making of the mountains. But the height then attained, instead of being, as now, 14,000 feet or more, was probably less than 5000 feet. At the same time, or earlier, the Triassic rocks of the Atlantic border in the Connecticut River Valley and elsewhere were slowly upturned; and as the up- turning made progress, great fissures, parallel in course nearly to the longer axis of the areas, were opened and the liquid trap rock came up. During the formation of the sand- POST-MESOZOIC REVOLUTION". 235 stone a slow subsidence was in progress, as is proved by the footprints on the surfaces of layers and other markings, these showing that the layers originally mud-flats and sand-flats were successively at the water level. The Post-Mesozoic Revolution. The close of the Mesozoic time was followed by mountain- making on a grander scale even than that with which Paleo- zoic time was closed and by equally extensive disappearance of species over the world. The mountains which were made at this epoch extend along the whole line of the summit region of the Rocky Mountains from near the Arctic Ocean to Central Mexico a distance exceeding 4000 miles. They constitute the Laramide Mountain system, and include the Wasatch range of western Utah ; other ranges to the north of Mon- tana in British America ; and others to the southward over a Avide reach of country, through New Mexico and Mexico beyond. It is also probable that in South America at this same time, another system of ranges of as great a length was made along the Andes, and that consequently the mountain-making move- ments of America at the close of the Cretaceous extended through nearly one third of the earth's circumference. Until the beginning of these movements the Rocky Moun- tain region was mostly beneath the salt water ; for the upper Cretaceous beds contain marine fossils. Further, during its later part, there were alternate emergences and submergences of the land which favored the making of the many great coal-beds. 23(3 I'OST-MESOZOIC REVOLUTION. With the completion of the mountains, the region of the great Interior Continental sea of Cretaceous time made its final emergence from the salt water, excepting perhaps the area of the Great Salt Lake of Utah and some other similar patches. Emergence of the eastern half of North America was one of the great events at the close of Paleozoic time; and so the emergence of the western half marked the close of Mesozoic time. Moreover, the Mesozoic, like the Paleozoic, finished its rock-making work with the accumulation of great coal-beds the western, like the eastern, of incalculable value to the country. The disappearance of the life of the world at this crisis was so extensive that no marine species of the Cretaceous period have yet been certainly found in any rock of the following period. This is another great feature in which the Post-Meso- zoic revolution was like the Post-Paleozoic. Here ended the Reign of Reptiles, all the characteristic Mesozoic kinds, the Dinosaurs, Sea-saurians, Pterosaurs or flying species, and others becoming extinct. The Am monoids also, and the Belemnites, with many of the genera of other tribes of Mollusks, dis- appeared. Among plants, the Cycads, which were a prominent feature of the Mesozoic forests in the early Cretaceous, even on Arctic lands, later retreated southward and became confined to the warm temperate and tropical zones, where the few now existing are still to be found. As in other such exterminations, the extinction of life was not universal. Large regions suffered little from the exter- TERTIARY ERA. 237 ruinating cause, as the survival of the genera and families prove. All that can be affirmed is, that the fossils of the Ter- tiary era, the next after the Cretaceous, contain, so far as yet discovered, no marine Cretaceous species. IV. CENOZOIC TIME. CENOZOIC TIME comprises two eras : 1. The TERTIARY ERA OR THE REIGN OF MAMMALS. 2. The QUATERNARY ERA OR THE REIGN OF MAN. 1. Tertiary Era. The Tertiary era is divided into three periods : (1) the EOCENE ; (2) the MIOCENE ; (3) the PLIOCENE. These terms, which are derived from the Greek, signify, severally, (1) the dawn of recent time; (2) the less recent; (3) the more recent. The areas over which the marine Tertiary rocks of North America and England occur are shown on the maps, pages 136 and 212. ROCKS. As the salt waters had left the Continental Interior at the close of the Cretaceous, the marine rocks of the Tertiary were confined to the borders of the continent. But the Interior was still a region of extensive rock-making through the agency of vast freshivater lakes. The map on page 238, Fig. 272, shows the position of the sea-border Tertiary, and also of the great lakes and litnixfrine beds of the Interior. 238 CENOZOIC TIME. Iii the early Tertiary, the rivers of the eastern part of the continent, or those contributing waters and sediment to the Atlantic, may have had half or two thirds of their present FIG. 2T2. Map of North America in the Tertiary Period. Vertical lining shows submergence in the Eocene ; horizontal lining, submergence in later Tertiary ; cross-lining, submergence throughout the Tertiary. extent; but the Ohio and Mississippi were still independent streams, emptying together into an arm of the Mexican Gulf. The Missouri and other western streams were just beginning to be. During the Eocene, or early Tertiary, the Rocky Mountains were but little elevated; for great lakes then occupied TERTIARY ERA. 239 much of the summit region, in Utah, Colorado, Wyoming, and New Mexico. Later, as the land rose, these summit lakes dis- appeared, and there were great Miocene lakes over what is now the eastern slope of the mountains, from northern Ne- braska to Mexico. On the map the Eocene lakes are marked by vertical, the Miocene by horizontal, lines. The North American Tertiary consequently comprises vast freshwater formations as well as marine. Marine beds of the Eocene period were formed on the At- lantic border south of New York, and on the borders of the Mexican Gulf ; but marine Miocene and Pliocene only on the Atlantic border, from New York to Florida, some change of level having excluded them from the Gulf border west of Flor- ida. On the Pacific border also there are areas of marine Ter- tiary. At the base of the marine Eocene beds of the Lower Mississippi there are Lignitic beds, that is, beds containing lig- nite (a kind of mineral coal retaining usually something of the structure of the original wood) alternating with beds that are partly marine, the whole indicating that freshwater marshes there alternated with freshwater lakes and salt seas ; for the Lignitic beds were once beds of vegetable debris such as are formed in marshes. The freshwater Tertiary beds are the lacustrine formations of the great lakes of the Rocky Mountain region already men- tioned. The most western are situated in Oregon. Immense numbers of bones of Mammals and many entire skeletons have been obtained from these beds, showing that the shores of the 240 CENOZOiC TIME. lakes were the resort of wild beasts, some of them of elephan- tine size. In Great Britain marine Eocene Tertiary beds occur in the London and Hampshire basins, and on eastern seashores a thin Pliocene stratum, but no marine Miocene is found. Over Europe and Asia the Eocene formation was widely distributed, showing that these continents, even as late as the early Tertiary, were largely under the sea. The Pyre- nees, Alps, Apennines, Carpathians, and the highest moun- tains of Asia were partly made of them. The beds in many places contain or consist largely of coin-shaped Fora- minifers, or Rhizopod shells, called Nummulites, varying from half an inch to one inch or more in diameter. The beds are often called Niimmulitic limestones. The limestone ^ wn i cn some of the Egyptian pyramids are built is made up chiefly of Nummulites. One of them is represented in Fig. 273; the ex- terior is partly removed to show the cells of Nummuiite. the interior, that were once occupied by the minute Khizopods. Some species of a related genus occur in modern coral seas. They must have been exceed- ingly abundant over the great Continental seas of the Tertiary. Miocene beds have a thickness of several thousand feet in Switzerland (constituting the Bigi and some other sum- mits), and occur in many other parts of Europe; but they are limited in area compared with the Eocene. Marine TERTIARY ERA. 241 Pliocene beds are of still less extent, yet have a thickness in Sicily of 3000 feet. The rocks of the marine Tertiary are very various in kind. The larger part are soft sand-beds, clay-beds, and shell deposits, the shells often looking nearly as fresh as those of a modern beach. Other beds consist of moder- ately firm sandstone. There are also loose and firm lime- stones. The greensand called "marl," used as a fertilizer, which is so characteristic of the Cretaceous, also constitutes beds in the Tertiary of New Jersey. The freshwater beds are like the softer marine beds, but contain, of course, no marine shells. Part of them are quite firm ; but others are easily worn by the rains. Some great areas in the Rocky Mountain region, both over the sum- mit and the eastern slope, have been reduced by denuding waters to areas of isolated ridges, towers, pinnacles, and table-topped hills, that are mostly barren, owing to the dry climate, and which are therefore called "Bad Lands," or in French (in which language the expression was first applied), "Mauvaises Terres." LIFE. The life of the Tertiary shows in all its tribes an ap- proximation to that of the present time. The Mammals, and probably the Birds, are all of extinct species. But among the plants and the lower orders of animals there were many species that still exist : in the Eocene, a small DANA'S GEOL. STORY 16 242 CENOZOIC TIME. percentage; in the Miocene, 25 to 40 per cent; and in the Pliocene, a much larger proportion. The common Oyster was living in the Pliocene, and the Clam as far back as the Miocene period, along with a large number of species of shells that are now extinct. Progress through the Tertiary era was gradual in all departments. FIGS. 274-2T8. 278 Eocene of Alabama. Fig. 274, Ostrea sella'formis ; 275, Oassatella alta ; 276, Pteropsis Couradi ; 277, Venericar- dia planicosta ; 278, Turritella carinata. The forests of North America and Europe were much like the modern, but with a larger proportion of warm-climate forms, especially in the Early Tertiary. Through the Eocene, Palms nourished over Europe and England. In the Miocene the European species were still those of a warmer climate than the present, and included some Aus- tralian species. Even in the Arctic zone there were in the Miocene great forests of Beech, Oak, Poplar, Walnut, and TERTIARY ERA. 243 Redwood (or Sequoia, the genus to which the " great trees " of California belong), with Magnolias, Alders, and others. FK.S. -279-2S1. FIG. 282. Miocene of Virginia. Figs. 279, 280, Oepidula costata ; 281, Cypriea Carolinensis. The modern aspect of the marine shells is shown in the accompanying figures: Figs. 274- 278 represent American Eocene species, and 279-281, Miocene from the Atlantic border. The Tertiary Vertebrates were less like the modern than the Inver- tebrates. Among Fishes, Sharks were exceedingly abundant, and their teeth, the most enduring part of the skeleton, are very common in some of the beds. Those of one kind, pointed, triangular in form, were nearly as large as a man's hand. One of the smaller of these teeth is represented in Fig. 282. Shark's Tooth. Carcharodon angustidens. 244 CENOZOIC TIME. The true Reptiles were Crocodiles, Lizards, Turtles, some of gigantic size, and Snakes. Among the Birds there were Owls, Woodpeckers, Cormo- rants, Eagles ; and those of France included Parrots, Trogons, Flamingoes, Cranes, Pelicans, Ibises, and other kinds related to those of warm climates. The common Mammals were the ordinary non-Marsupial kinds. The Eocene beds about Paris, France, afforded to FIG. 283. Tapirus Indicus, the Modern Tapir of India. Cuvier the first specimens described; and now they are known from all parts of the world, and from none in greater variety than from the freshwater Tertiary region west of the Mississippi. Some of the Eocene kinds were related to the modern Tapir (Fig. 283), Hog, Rhinoceros, and Hippopotamus. The earliest species appear to have had the full number of toes, Jive, to both the fore and hind feet, typical of Mammals, TERTIARY ERA. 245 and also the full number of teeth, forty-four ; while most of the later species have a less number of teeth, and most of the hoofed, or ungulate, species, and some of the clawed, or un- guiculate, species, have a less number of toes. The Tapir, here figured, has three toes behind and four in front; and the Hog and Hippopotamus, each four to all the feet; Cam- els, Cattle, and Sheep, two to each foot; and the modern Horse, but one. FIG. 2<4. Tinoceras ingens. One of the strange beasts of the Eocene is represented in Fig. 284. It had three pairs of horns, feet somewhat like those of an Elephant, and a length, exclusive of the tail, of 12 feet. The Miocene beds of North America have afforded remains of 3-toed Horses, of extinct species related to the Tiger, Wolf, Rhinoceros, Camel or Llama (Fig. 285), Deer, Masto- don, Squirrel and Beaver. 246 CENOZOIC TIME. In the Pliocene beds of North America occur remains of true one-toed Horses, Camels, Mastodons, and various other species all of them extinct, like those of the Miocene and Eocene. In the Pliocene of other lands occur species of Elephant, Bear, Horse/ Antelope, Stag, Sheep, Ox, etc. Cat- tle related to the Ox do not occur earlier than the Pliocene. The Mammalian type was at last very fully displayed, its FIG. 285. Poebrotherium labiatum. grand divisions and most of the modern genera being well represented. But the maximum display of the brute races took place stitt later, in the early or middle Quaternary, after Man had appeared. MOUNTAIN-MAKING DURING THE TERTIAKY. During the later part of the Tertiary, the loftiest moun- tains of the world received the greater part of their present elevation. TERTIARY ERA. 247 Iii North America, the amount of actual upturning was small compared with that at the close of the Cretaceous period. There were low mountains made after the Miocene on the coast region of the Pacific ; and some of the Mio- cene lacustrine areas were upturned. But besides these local events, a lifting of the Rocky Mountains as a whole from the far North to Central America was begun, which continued on through the Tertiary and ended in raising the great area from near the sea level where it was, as fossils prove, at the close of the Cretaceous period to a height of 10,000 feet above it in Mexico, 16,000 feet in Colorado (nearly 2000 feet of this height since lost by de- nudation), and 10,000 to 4000 feet in British Columbia. The existence of vast freshwater lakes over the Rocky Mountain region proves that the rising went forward with extreme slowness, and probably with long intervals of delay; that little progress was made in the Eocene period, when the lakes covered the summit region; and that the final height was not attained before the close of the Pliocene, the last period of the Tertiary. During the same time the Andes received an addition to their height of 20,000 feet in Ecuador and of many thousands in less elevated portions. In Europe the Pyrenees experienced extensive upturnings near the close of the Eocene, and the Alps and Juras after the Miocene ; and now the rocks before submerged are 10,000 and 12,000 feet above sea level. In Asia, upturning began 248 CENOZOIC TIME. in the Himalayas, after the Miocene, and a rise followed of 20,000 feet. During Tertiary time, moreover, and especially in the Miocene period, great eruptions of igneous rocks took place over the western slope of the Rocky Mountains, covering thousands of square miles. The deep fractures were prob- ably then opened which gave origin to the volcanoes Mount Shasta, Mount Hood, and other summits in the Cascade range. So also along the coast of Ireland and of Scotland, and the Inner Hebrides to the Faroe Islands, the eruptions were of great extent. Fingal's Cave and the Giant's Cause- way date from this period. This epoch of great eruptions in the Rocky Mountains ap- pears to have begun before the close of the Cretaceous period, and to have had a climax during the making of the Laramide Mountain system. At this time also the rich silver and lead veins of the Rocky Mountains, from Wyoming to central Mexico, were probably made ; and probably also those of like character and richness along the Andes. The eruptions of the Miocene period, however, seem to have been on a still larger scale. The great Continental uplifting of the closing Tertiary was a prelude to the grand events of the opening Quaternary. CLIMATE. During Mesozoic time the Arctic zone was warm enough for great Reptiles, warm-climate species ; and the British seas, for coral-reefs. QUATERNARY ERA. 249 The Eocene era also was one of warm climate over Great Britain, for England was then a land of Palms ; and Palms continued to flourish over middle and southern Europe during the Miocene. Through both the Eocene and Miocene the Arctic lands were covered with forests, and hence the Arctic climate must have been comparatively warm, not colder at least than the present climate of the middle United States and northern Prussia. There was a cooling off with the progress -of the Miocene, and by the close of the Tertiary the earth had probably its frigid, temperate, and torrid zones, nearly as now. 2. Qimt<'i-ni>cr surface, in spite of the slope of the surface beneath it. It is like thick pitch, as well as water, in this respect. If pitch were dropped indefinitely over a spot in a plain, it would spread away indefinitely; and if the surface around the spot even had a rising slope, it would fill up the basin and then take a course outward. 80 it is with the ice of a glacier. In order to have a southeastward course, a glacier must have its surface highest to the northwestward, with slope southeastward; and if the snows were more abundant to the north in the Glacial era, and the melting less abun- dant there than to the south, an accumulation to the north might have gone on that would have produced movement southward. If the plane beneath the pitch had deep chan- nels obliquely crossing it, the pitch in these channels would follow their direction, while the overlying pitch kept on its main course. So with the glacier, its lower part within the large valleys followed the directions of the valleys, as the scratches and bowlders show ; while the upper portion had its iisual course, the course which is indicated by the scratches elsewhere over the higher parts of the country. The cold of the era may have been mainly due to an eleva- tion and extension of Arctic lands, increasing the area of QUATEKNAUY ERA. 257 Arctic land-ice ; and to a partial closing, through this eleva- tion, of the Arctic region against the warm current of the Atlantic Ocean, the Gulf Stream which is now a source of warmth to all of northeastern Europe, and even Iceland, Nova Zembla, and the polar seas and lands. But it is prob- able that the land of the higher latitudes of America and Europe was higher than now ; and that the Antarctic region was an area of high land; and that this was a prominent cause of the cold. Other reasons for cold have been suggested, references to which will be found in large works on the subject. South America has in its southern portion a great glacial region, bearing evidences of transportation toward the equa- tor; and farther north there were glaciers about the higher summits of the Andes. The phenomena described were there- fore not confined to one hemisphere. Some writers suppose them to have occurred alternately in the northern and the southern hemisphere. But no direct evidence of this has been obtained. The moving glacier of New England appears to have had its head in the height of land between the St. Lawrence Valley and the Great Lakes on the south, and Hudson Bay; for the scratches diverge from this region over eastern Maine, New Hampshire, Vermont, and New York, being in western New York and Pennsylvania southwest in direction. Over this region the ice appears to have reached its highest elevation. This ice-plateau, called the Laurentide plateau, extended west- ward, and also northward by the west side of Hudson Bay, and DANA'S GEOL. STORY 17 258 CENOZOIC TIME. from it the ice descended with its freight of stones and gravel southwestward over Michigan, Wisconsin, Illinois, and Iowa, reaching even into Kansas and Missouri ; and westward cross- ing the Winnipeg region to where the ice met that of the View on Roche-Moutonnee Creek, Colorado. summit of the Rocky Mountains. North of Hudson Bay and of 60 to 65 in western North America, the flow was north- ward. Local glaciers of great magnitude existed about the higher parts of the Rocky Mountains, within the United States, and also on the Sierra Nevada. Moraines, scratches, roches mou- tonnees, on a grand scale occur in many valleys of the QUATERNARY ERA '259 higher ridges of both the Rocky Mountains and the Sierra Ne- vada, as mementos of their former Glacial history. The sketch (Fig. 288, page 258) of roches moutonnees in one of the higher valleys of Colorado is repeated here from page 82, because the events indicated belong to the Glacial period. The roches moutonnees extend along the valley through an ascent of nearly 2000 feet. At present there are no glaciers within 500 miles of the place. In the same era a glacier in the Alps buried all Switzerland, 2000 to 4000 feet deep in ice, and left immense blocks of Alpine rocks on the Jura Mountains. Depositions of earth and stones from the glacier must have been going on to some extent through the whole Glacial era. Moreover, the perpetual grinding of stones against stones under a glacier often made a very fine clayey earth; and consequently the drift is often called bowlder-clay. 3. Retreat of the Ice. The southern ice-limit, when the ice was of maximum extent, reached, on the east, to southern Long Island; thence it continued westward, by Perth Am- boy, New Jersey; crossed Pennsylvania obliquely; and fol- lowed nearly the course of the Ohio River from Ohio to and across the Mississippi. West of the Missouri it bent north- ward and westward to North Dakota, and then westward to Montana, where it reached the ice of the Rocky Moun- tains, about 4000 feet below the summit. The position of this southern limit of the ice is shown by the line AA on the maps on pages 251 and 200. For explanation of the map see pace 251. QUATERNARY ERA. 261 At the melting, the retreat first showed progress in the Continental Interior, over Illinois, Kansas, and Iowa, where the land was laid bare by the melting, in Illinois and Iowa, for 250 miles northward from the southern limit, before there was much appreciable change in Pennsylvania and to the eastward. This difference in rate of melting was owing to the fact that the east was a region of great pre- cipitation, where, therefore, snows were freely supplied to keep the ice up to its limit; while the Interior was dry, a] id the small amount of snow of the year was easily melted. From Kansas over eastern Nebraska, in or near the Mis- souri Valley, the first retreat extended northward for 1000 miles or more, reaching far into British America. As a consequence of the melting along this 1000 miles, the Mis- souri was at this epoch the great river of the continent, with the lower Mississippi as its seaward continuation. After a long halt, the melting again became so great that the retreat began anew. Over the northern part of the Continental Interior, the margin was moved eastward to and across Lake Winnipeg; and from Minnesota, Wisconsin, and Michigan, it was moved northward into British America. Then the Mississippi became the greatest of rivers; for the elevation of the land to the north was such that the Win- nipeg waters poured down the Red River of the North and the Minnesota River in great volumes to fill up and flood the Mississippi. 262 CENOZOIC TIME. Finally, Neiv York and New England lost their ice, ex- cepting what lingered about the higher mountains. The melting is evidence of a slow change of climate. It may have begun in consequence of changes outside of the continent. But before it was completed there was a sub- sidence of the land over the higher latitudes, which made the climate still warmer, and so hastened the disappearance of the ice. With this subsidence a new period opens in the earth's history characterized by a mild climate, even milder than that now existing; and by a reforesting and repopulating of the previously glaciated regions. 2. Champlain Period. The warm Champlain period, in strong contrast with the period of slow-moving ice, was the time of great floods along the river valleys, as a conse- quence (1) of the waters let loose by the lingering ice of the hills, and also (2) of excessive rains from the continued moist climate. In further contrast with the Glacial period, it was, as has been stated, a time of lower level than now over the higher latitudes ; and hence the action of the rivers became changed to a large extent from excavating streams, deepening thereby their channels, to streams that deposited sediment along their banks, and thereby made great fluvial formations. As a consequence, moreover, of the genial climate, the banished forests and animal life rapidly regained possession of the plains and hills. QUATERNARY ERA. 263 The fact that the land of the more northern latitudes was at a lower level than now is proved by the existence of many Cliamplain sea-beaches or marine beds at high levels, in the form of terraces, along the existing borders of the ocean, lakes, and rivers. The beds have a height of 80 feet on Nan- tucket ; 150 to 300 along the coast of Maine ; 300 to 600 along the St. Lawrence Valley, the greatest height up-stream, namely, 200 feet at its mouth, 520 feet at Montreal, and 600 not far from Lake Ontario, so that the St. Lawrence River was then a vast St. Lawrence Gulf, 500 to 600 feet deep. Even Lake Champlain was an arm of this St. Lawrence Gulf, for beaches containing sea shells occur on its borders to a height of 450 feet, and at a little lower level remains of a whale have been found. It had the great depth of from 700 to 900 feet. Moreover, Labrador has similar beaches at a height of 500 to 800 feet, and some Arctic land at 1000 feet. Similar facts are reported from the Pacific coast. The subsidence was greatest to the north, it having been probably not over twenty feet on Long Island Sound, and seventy at New York Bay, while it was 500 feet at Montreal and 335 feet at Albany, New York. This increase to the north- ward was the cause of the diminished pitch in most of the rivers ; for it affected directly all southward-flowing streams. The deposits from the flooded waters along the valleys and about the lakes became hundreds of feet thick in many places. The upper flat surface,' now the "upper terrace " of the valley, is a mark approximately of flood 264 CENOZOIC TIME. height. The valleys of the Hudson and the Connecticut are examples. The waters gathered their detritus from the drift-covered hills through their numerous tributaries ; for the amount of sand, gravel, and clay which had been dropped by the ice was immense, and it lay loose, easy to be taken up by streams the rains might make. The Mississippi Valley was the outlet for the waters of the great region it now drains ; and its floods during the whole Glacial period must have been great, and floating ice laden with northern stones must have often been hurried off down stream to the Gulf. During the melting it made thick deposits on the way to the Gulf, as observed by Hilgard, and in Mis- sissippi, bowlders as large as a bushel basket are found in the beds. In Europe and Great Britain the Champlain period was one of subsidence over the higher latitudes, as in America, and the subsidence was greatest to the north. In France and Bel- gium the depression below the present level was ~>0 to 100 feet ; in southern England 100 to 200 feet. In Sweden it was 200 at the south to 400 or 500 to the northeast, so great that an ocean channel then connected the Baltic with the White Sea. Between the Champlain and Recent periods, Europe passed through a second, but less severe Glacial epoch. Marks of it have been pointed out in glacial deposits in the Alps and other places, but especially in southern France, through the occur- QUATERNARY ERA. 265 rence in great quantities of remains of the Reindeer, a cold- latitude animal. With the bones of the Reindeer there are also those of other cold-climate species. This epoch is called the J'dndccr epoch. After it conies the Recent period in geological history. LIFE OF THE PLEISTOCENE, OR THE GLACIAL AND CHAMPLAIX PERIODS. 1. General Observations. The plants and the lower tribes of the Animal kingdom in the early part of the Quaternary were essentially the same as now. The species of Corals making coral-reefs in the tropics were probably in exist- ence and at work before the close of the Tertiary age; and the same is true of most of the Invertebrates of the modern world, and also of the plants. There must have been some exterminations as a conse- cpiience of the cold of the Glacial period, and of the ice of high-latitude regions. Many plants were driven south by the coming on of the cold, and thus escaped destruc- tion; and some of these now live on Mount Washington and other high summits of temperate North America. Birds must have shortened their migrations northward and length- ened them southward, and for the most part they may have escaped catastrophe. The beasts of prey, cattle, and other large Mammals of Drift latitudes must i also to a great extent have moved toward the tropics as the rigors of the approaching ice-period began to be felt. Certain it is, that 266 CENOZ01C TIME. after the ice had gone, a large population of brute Mam- mals moved in from the warm southern latitudes over Europe and the other continents; and facts seem to prove that they hung about the southern limit of the ice, and often moved northward with the lulls in the intensity of the climate or the shortening in at intervals of the ice-field. 2. Brute Mammals. The brute Mammals appear to have reached their maximum in numbers and size during the Avarm Champlain period. Those of Europe, Great Britain, and America were largely warm-climate species, such as now are confined to warm-temperate and tropical regions. Only in a warm period like the Champlain could they have there thrived and attained their gigantic size. The great; abun- dance of the remains and their condition show that the cli- mate and food were all the animals could have desired. They were masters of their own wanderings and had their choice of the best. But the colder conditions of the Kecent period which followed were less favorable, and many <>f the species are now extinct. Remains of these Mammals have been found in deposits along the margins of rivers and lakes; in marshes, \vhere they became mired; in caves, buried in the stalagmite (page 40) that was deposited over their deserted skeletons. In Great Britain and Europe the caves were the ha i mis of Hears, Hyenas, and Lions, much larger than any of the kinds no\v living; these beasts of prey dragged into their caves the bodies of the animals they fed upon. The Cave Bear resembled QUATERNARY ERA. 267 much the Grizzly Bear of western North America; and the ('a vi- Hyena and Cave Lion are regarded as the same in spe- cies with the African Hyena and Lion, although these modern kinds are dwarfs in comparison. \Yith these there were in Great Britain and Europe species of FIG. 290. Skeleton of Mastodon Americanus. Ehinoceros, a Hippopotamus, the Siberian Elephant or Mam- moth, the Brown Bear, Wolf, Wild Cat, Lynx, Leopard, Fox, Elk, Deer, and others. The modern species of Horse was among them. The Irish Deer (Cervus megaceros), skele- tons of which have been found in Irish bogs, had a height 268 CENOZOIC TIME. to the tip of the antlers of 10 to 11 feet, and the span of the antlers was sometimes 12 feet. The Elephant (Elu- phas primiyenius) and the most common Rhinoceros (R. {/- rinus) had a hairy covering, which fitted them to roam over regions in the far north. The remains, especially those of the Elephant, show that they lived in great herds over northern Siberia, where now the mean temperature of the FIGS. 291, 292. 291 Teeth of Mastodon and Elephant. Fig. 291, Mastodon Americamis ex. J) ; 292, Elephas priiiiigviiius. year is 5 to 10 F. The Rhinoceros had a length of 11| feet, and the Elephant was nearly a third taller than the largest of modern Elephants. In North America also there were large Lions and Bears, but none of them, so far as known, made caves their dens. The largest of the species was the Mastodon (Fig. 290), an animal with tusks and trunk like an Elephant. When full grown it was 12 to 13 feet in height, and to the extremi- ties of the tusks 25 feet long. The teeth had a crown as large in area as this page, and of the form shown in Fig. (.U-ATKUNAKV ERA. 269 L'lll. Skeletons have been found in marshes where the heavy beasts were mired; and portions of their undigested food the small branches of spruces and other trees have been taken from between their ribs, where the stomach was once trying to digest them. There were also American Elephants of great size, of the same species as the Siberian. Fig. 292 represents a tooth FIG. it3. Megatherium Cuvieri ( x of one found in Ohio; it is a little larger than that of the Mastodon. There were also Horses of large size, Tapirs, Oxen, Beavers, and various gigantic species of the tribe of Sloths. The Sloth tribe was especially characteristic of South America. The modern Sloth is as large as a dog of me- dium size. The species of the Champlain period included a J/^/^///^/-/"//rf (Fig. 293), which was larger than the 'largest of existing Rhinoceroses. As the figure shows, it was a lazy 270 CENOZOIC TIME. beast ; the bones of the hind legs are much like logs, and those of the fore feet are furnished with hands a yard long for pull- ing down trees after the animal raised itself erect for the pur- pose on its hind legs and enormous tail, a third support. This is one of many kinds of gigantic Sloth-like animals that lived in South America during the era. Other related species had a shell somewhat like the modern Armadillo ; and these also were gigantic, one of them (Fig. 294) measuring 5 feet across its shell, and having a length of at least 9 feet. FIG. 294. Glyptodon clavipes ( x In Australia the Mammals are now, with few excep- tions, Marsupials, the Kangaroo being one of them. They were also Marsupials then; but the ancient kinds partook of the peculiar feature of the era, great magnitude, some of the species being as large as a Hippopotamus, one having a skull a yard long, and many of them being far larger than any modern Marsupial. Thus the brute races of the Middle Quaternary on all the continents greatly exceeded the modern races in magni- QUATERNARY ERA. 271 tude. Why they did so, no one has explained, beyond saying that the climate was favorable to great size. The genial climate of the Champlaiii period was abruptly terminated ; for carcasses of the Siberian Elephants were frozen so suddenly and so completely at the change, that the flesh has remained till these modern times untainted. Xear the close of the last century, one huge carcass dropped out of the ice-cliff at the mouth of the Lena, and for a while made food for dogs. The existence of a hairy cover- ing was then first ascertained. A hairy Rhinoceros has also been found in the ice. This change of climate was probably connected with the commencing of the Reindeer epoch, closing the Champlain period; it was then that the Reindeer and some other species migrated to southern France, to live there until the cold epoch had passed. The remains of the Reindeer are accompanied by those of the Cave Bear, Cave Hyena, Rhinoceros, Elephant, and other Champlain spe- cies, showing that ail lived together there at that time. 3. Man. Man was in existence during the Champlain period; and probably in its earlier part before the ice had disappeared. Relics, indicating that he was a contemporary of the gigantic Champlain Mammals, occur in various cav- erns and in river and lacustrine deposits, in Great Britain, Europe, Syria, and in other regions. The relics of Man are stone implements, such as arrow- heads, hatchets, pestles, and stone chips made in the manufac- ture of the implements; beads, shells, and other materials 272 CENOZOIC TIME. having upon them his markings and carvings; his pottery; the charcoal left from his tires; the Lones of animals broken lengthwise to get out the marrow; his own bones, skulls, and skeletons. In Europe and western Asia the stone implements of the earlier part of what is sometimes called the Stone age are of rude make and unpolished. This part of the age has been called the Paleolithic epoch in human history, or that of the oldest stone implements, the word, from the Greek, signifying old and stone. The stone implements occur along with bones of the Cave Bear, Cave Hyena, Mammoth, lihi- noceros, and several other Champlain species, and also with the bones of Man ; and these human relics are so associated with those of extinct Mammals that there is no reason to doubt that they were contemporaries. Next came the Reindeer epoch. Its stone implements are unpolished, but better made than those of the preceding era. Besides these there are examples of bones, shells, horn, and stone engraved with the forms of animals; others that are variously carved, or made into spear-heads and other forms; and also perfect human skeletons. Fig. 295 represents a drawing, on ivory, of the hairy Elephant; it was found in the cave of La Madelaine, in Perigord, south- ern France, and shows that the Elephant was well known to the men of the period. These human relics are asso- ciated with remains of the same Champlain Mammals that occur in the earlier deposits, and also with great numbers QUATERNARY ERA. 273 of the bones of the Keindeer, and many of the Aurochs, Elk, Deer, and other species of later time. The bones and skeletons of Man of the Stone age, thus far found, in no case indicate a race much inferior to the lowest of Elephas primigenius; engraved on ivory (x g). existing races, or intermediate between Man and the Man Apes, the species among the brutes which approach him most nearly. But still they are those of uncivilized Man, and in part of Man of a low order of faculties. The skull of Neanderthal (a part of the valley of the Diissel, near Diisseldorf) is the worst, but it is probably not older than others having better skulls and higher foreheads. The capacity of the cranium was 75 cubic inches, which is greater than in some existing men. A jaw-bone of low type, found in the oldest Belgian deposits, had little height and great thickness, as if for powerful use, and the posterior of the molar teeth was the largest, a brutal feature. DANA'S GEOT,. STORY 18 274 CENOZOIC TIME. The human skeletons of the Reindeer era in southern France are in part those of men of unusual height, 5 feet 9 inches to over 6 feet ; and the skulls are large and well shaped, with the foreheads high and capacious. They are of better size and shape than many of the Reindeer era in Belgium, which are small and after the Laplander type. One of the most perfect was found in the stalagmite that formed the floor of the cave of Mentone, near the borders of France and Italy, on the Mediterranean. Eight feet above it in the stalagmite there were remains of the extinct Rhinoceros and other Champlain species. The man would compare well, if we may judge from the skeleton, with the best among civilized races, his forehead broad and high, and rising with a facial angle of 85, his height 6 feet; and yet he was a European savage of the Reindeer epoch; for about him lay liis flint implements and weapons, his chaplet of stag's canines, and shells that he had gathered for food or ornament from the shores near by. The tibia or shin-bone was somewhat flat- tened, a peculiarity often observed in the skeleton of the American Indian. The brain-cavity of a skull found in the cave of Cro- Magnon, in southern France, had a capacity of 97 cubic inches, which is very much above that of ordinary Man, and nearly three times that of the highest Man Ape. In North America cases of the occurrence of ancient human bones or skeletons in Quaternary deposits are not so well authenticated as those in Europe. Admitting the facts that QUATERNARY ERA. 275 have been published, they do not give Man greater antiquity than those above mentioned. No case of the presence of human relics in deposits of the Tertiary age on any continent is yet well established. Mr. W. P>oyd Dawkins, an excellent British geologist and original observer in this department of the science, states, in his recent work on Cave Hunting (1874), that the evidence obtained proves that "Man lived in Germany and Britain after the maximum Glacial cold had passed away," and that no human remains " have been discovered up to the present time in any part of Europe which can be referred to a higher antiquity than the Pleistocene (Quaternary) age." The second Glacial or Reindeer epoch in Europe (which there is reason to believe produced effects also in North America) appears to have finally brought to a close the era of giant beasts, leaving the world for Man. 3. Recent Period. The Champlain period was brought to a close by a moderate elevation of the land over the higher latitudes, bringing the continent up to its present level. This elevation placed the old sea-beaches of the Champlain period at their present level high above the sea, that is, over 500 feet near Montreal, over 200 feet on the coast of Maine, and so on, the height of the shell beaches being a measure of the amount of elevation. River-valleys, after the rise, had a steeper slope than in the Champlain period, and hence their flow was increased in rate. They consequently went on cutting down their beds through the Champlain deposits 276 TIME. of the valley to a lower level ; and at the time of their annual floods they wore away the deposits on either side of the channel, making thereby an alluvial flat or flood-ground ; for every river has a flood-ground which it covers in its times of flood, as well as a channel for dry times. This sinking of the river-beds left the old flood-grounds as a high terrace far above the level of the stream ; and the great FIG. 296. Terraces on the Connecticut River, south of Hanover, N. H. elevated plains still remain to attest the vastness of the floods from the melting glacier. In the course of the elevation a series of terraces was often ma.dc 1 along the valleys, as illustrated in Fig. 296. A section of a valley thus terraced is represented in Fig. 297. The formation terraced is. as is shown, the Champlain; in the (Jhaniplain period it tilled, QUATKUNAUY ERA. 277 * in general, the valley across (from /to/'), excepting a narrow channel for the stream, the whole breadth having been the flood-ground of the Chaniplain River. But after the elevation of the land that closed the Chaniplain period began, the river commenced to cut down through the formation, making one or more terraces in it, on either side of the stream. In Fig. 297, R is the position of the river-channel after the terracing ; Section of a Valley with its Terraces Completed. and on either side of it there are terraces at the levels//', dd', bb'j and also another on the right side, at cV. These terrace- plains are usually the sites of villages. They add greatly to the beauty of the scenery along water coiu-ses. The terraces usually fail where the valley is narrow and rocky. Hock-making has not yet ceased, for the old agencies the waters, the winds, and life are still at work with unimpaired energies. Sand-beds, pebble-beds, and mud-beds are accu- mulating along seashores and in shallow waters, precisely like those that were hardened into ancient sandstones, con- glomerates, and shales; and limestones are forming from shells and corals similar to ancient limestones. Further changes of level are still going on. A large part of Sweden is rising at the slow rate of four feet or so a century, 278 CENOZOIC TIME. and as slowly a portion of Greenland is subsiding. The Atlantic coast from New Jersey to Labrador is supposed to be sinking, and, along New Jersey, at the rate of two feet a century. Man, in the Recent period, passed the last part of his Stone age, styled the Neolithic epoch. In Europe, the stone implements of the epoch include polished implements, as well as those which are merely chipped ; and the animal remains found in the same beds are portions of skeletons of the domes- tic Dog and other existing quadrupeds, with much broken pottery. The epoch is called the Neolithic, from the Greek for new and stone. The shell-heaps or Kitchenmiddens, of the Danish Isles in the Baltic, are part of the Neolithic localities. Among the North American Indians, the Stone age was con- tinued to within a century or two. Besides human remains, modern fossils include corals, shells, and relics of all the various tribes of the passing period. Moreover, species are becoming extinct ; at least through Man, if not in other ways. The Dodo, an extinct bird of 50 pounds' weight (Fig. 298), was living on Mauritius in the seventeenth century. The Moa, larger than an Ostrich, and other birds with it, have recently disappeared from New Zealand. The Aurochs (Bison priscus) of Europe is nearly extinct. Thus wild animals have begun to disappear before advancing Man. The same is true of plants. The age of Man now has as its fossils, not only flint imple- ments and human bones, but also buried cities, temples, statues, and manuscripts. QUATERNARY ERA. 279 FIG. 298. Extinct Species. Dodo, with the Solitaire and an Extinct Species of Night Heron in Outline. From -A painting, at Vienna, iiiruli- by Kohiml Savery, in 1628, 280 GEOLOGICAL HISTORY. The system of life, long in progress, finally reached its com- pletion in a being that could search into the earth's history, study Nature's laws and investigate the system of the universe ; and who has thus the highest credentials of kinship Avith the Infinite Author of physical and moral law. The progress now of chief interest is no longer the development of animal races and characters, but the exaltation of Man in the direction of his higher nature. V. OBSERVATIONS OX GEOLOGICAL HISTORY. 1. Length of Geological Time. To the question, " what is the length of geological time ? " geology gives no definite reply. It establishes only the gen- eral proposition that time in lomj. The Canon of the Colorado (page 103) is a gorge -00 miles long, bounded the most of the way by steep walls of rock 3000 to 5000 feet in height, cut through sandstones, limestones, and other rocks ; and at bottom over parts of it, for several hundred feet, into granite ; and above the lofty walls a few miles back from the stream the pile of nearly hori- zontal strata is continued in mountains of nearly horizontal strata to a height of 7000 to 8500 feet above the bed of the river. All the facts, as its describers testify, point to running water as the agent that made the great channel. The region was imder the sea until the close of the Cretaceous period, for LENGTH OF GEOLOGICAL TIME. 281 marine Cretaceous strata are the uppermost rocks. It follows, then, that all this extensive excavation was accomplished by slow-acting water during Cenozoic time. Surely Cenozoic time was very long. The gorge of the Niagara River below the Falls has a length of seven miles. It is the work of the waters since the latter part of the Glacial period; for during this period the older channel was filled up by deposits of drift from the ice. The water has consequently made this excavation, seven miles long, since the ice left the region. From estimates of the present rate of erosion, the length of the time of erosion is between 6000 and 7000 years. The thickness of a sedimentary deposit is no satisfactory basis for determining the length of time it took to form. In a sea 100 feet deep, 100 feet of sediment may accumulate ; and the thickness could not exceed this (except a little through wave-action and the winds) if a million of years were given to the work. Let the same region be undergoing a subsidence of an inch a century, and the thickness might increase at that rate ; and much faster, if a yard a century ; and with either rate, giving time enough, any thickness might be attained. Hence a stra- tum of sandstone 100 feet thick may have been formed in a thousandth part of the time of a thin intervening bed of shale. Neverthefess, the aggregate maximum thickness which the strata attained during the several ages may be vised for an approximate estimate of the comparative lengths of those ages. 282 GEOLOGICAL HISTORY. On such data, it is deduced that the time ratio for Paleozoic, Mesozoic, and Cenozoic time was not far from 12 : 3 : 1. Con- sequently, if we suppose the length of time since the Paleozoic began to be 16 millions of years, Paleozoic time will include 12 millions, Mesozoic 3 millions, and Cenozoic 1 million. Most geol- ogists Avould make the whole interval several times 16 millions. 2. Progress in Development of the Earth's Features. The earth through the ages made progress : 1. In its Surface Features : from the condition of a melted sphere as featureless as a germ, to that of an almost univer- sal ocean with small lands, enough of land to mark out the feature-lines of the future continents; and at last after slow expansion southward, a lifting of mountain ranges at long intervals, and a retreating of the waters to the existence of great continents having high mountain bor- ders and well-watered interior plains. 2. In its River-systems : from the existence of only little streamlets draining small lands in the Archaean and Silurian eras, and making no permanent geological record beyond a rain-drop impression, to a condition of vast freshwater lakes and marshes when beds of vegetable material accu- mulated for the making of coal-beds ; and finally to that of the completed continent, when a single river (with its tributaries) drains, waters, and contributes ferity to hun- dreds of thousands of square miles of surface, and the work of fresh waters in rock-making exceeds that of the ocean. BEGINNING AND END OF THE EARTH. 283 3. In its Climate: from a condition of general uniformity of temperature, to, at last (though with interrupted prog- ress) that of the present diversity, when the polar regions have a permanent capping of ice, and only the equatorial regions perpetual verdure. 4. In its Living Adornments: from an era when the small rocky lands were bare, or gray and drear with lichens, and all other life was of the simplest kind and below the water level, to a time of flowerless forests and jungles over immense plains, yet with no sound from living Nature more musical than the Amphibian's croak; and on- ward to the better time when the earth abounds in flowers and fruits and birds, and is covered with the homes of Man. 3. The System of Nature of the Earth had a Beginning and will have an End. A system of progress or development in the earth as much implies that it had a beginning, as that in any plant or ani- mal. Man, Mammals, Fishes, Mollusks, Khizopods, Plants, all had, according to geological history, their beginning; so also mountains, valleys, rivers, continents, rocks; and so also the earth; and therefore the system of nature, whose development went forward in and through it, had its begin- ning. If this is^rue of one sphere in space, we may rightly take another step and assert that the universe had its beginning. It also admits of demonstration that the earth will have 284 GEOLOGICAL HISTORY. its end. A finished state is always the state before decline and death. The earth is dependent for all the beauty in its living adornments, and even for the existence of its life, on the heat and light of the sun. The sun is annually losing its heat; and however infinitesimal the amount of loss, it is sure to end in a cooled and dark sun; and hence, even long before the sun is cold, the earth, supposing it to have met with no earlier catastrophe, will have become dark and life less, literally a dead earth. 4. Progress in Life. 1. From the Simple to the Complex. The progress in life was in general from the simpler forms to the more complex, or from the low to the high. This truth has been illustrated in each chapter of the preceding geological history. 2. By Gradual Steps. Species appeared and disappeared, not only at the beginning of ages, or of the subdivisions of ages called periods, but also during the progress of periods, each of the successive strata containing some fossils not found below, and failing of others that are abundant in underlying beds. There were at times epochs of wide-spread catastrophe, ending periods ; and two of them, those closing Paleozoic and Mesozoic time, were nearly or quite universal for the Continental seas. But these must have left iin- harmed the life of the deep ocean; and they could not have exterminated all the life of the emerged land, or even of the whole area of Continental seas. PROGRESS IN LIFE. 285 3. According to System. The first animal life was prob- ably the Protozoan, or Rhizopods, Radiolarians, and the like, -kinds that are minute and destitute of members. But later, the grander divisions of animals were defined; and the species which appeared afterward in the long succession were constructed according to one or another of the systems of structure thus estab- lished. Each division became displayed in higher and more diversified forms by the new species that came into exist- ence as time moved on. The first of the Vertebrates were the Fishes, the simplest of the principal Vertebrate classes. Even in these aquatic species the arms and legs of the higher Vertebrates were present, though only in the state of fins ; and the lung, though only as a cellular air-bladder; and the ear, though only as a closed cavity containing a loose bone; and so with other parts. Thus the earliest of Vertebrates possessed in an incipient stage many of the organs that became fully developed in the later and higher Verte- brates. And in the succession of species that existed, all were made on the fish-structure as its basis, even the spe- cies of the highest class, those of Mammals and Man. A zoologist, in order to understand the fundamental elements in the human structure, goes to the fish and the frog for instruction; and Nature is so true to her fundamental prin- ciples, that he finds there what he looks for. 4. A System of Development or Evolution. With every step there was an unfolding of a plan, and not merely an 286 GEOLOGICAL HISTORY. adaptation to external conditions. There was a working forward according to preestablished methods and lines up to the final species, Man, and according to an order so perfect and so harmonious in its parts, that the progress is rightly pronounced a development or evolution. Creation by a divine method, that is, by the creative acts of a Being of infinite wisdom, whether through one fiat or many, could be no other than perfect in system, and exact in its relations to all external conditions, no other, indeed, than the very system of evolution that geological history makes known. 5. Culmination and Decline of Tribes. As has been brought out in the history, Trilobites, Brachiopods, and Crinoids, besides other groups of Animals, reached their maximum, or culminated, in Paleozoic time; Amphibians, in the first period of the Mesozoic era; Reptiles among Vertebrates, and Cephalopods, the highest of Mollusks, in the later Mesozoic; brute Mammals, in the Cham plain period of Cenozoic time. So, again, in the kingdom of plants, the highest Cryptogams the Acrogens culminated in the Carboniferous period; Cycads, in the middle Mesozoic; while Palms and Angiosperms have the present era as their time of greatest display and perfection. These are a few exam- ples, showing that progress did not go on regularly upward; but that the old, not only in species, but also in tribes and orders, were culminating and then passing away, as new and higher tribes were introduced, in the progressing evolution of the kingdoms of life. PROGRESS IN LIFE. 287 6. Parallelism between the Progress of the System of Life and the Progress of Individual Life. An animal, in its growth from the germ or, as it is called, its embryonic development passes through a succession of forms before reaching the adult state. In Mammals the changes after birth are small, the larger part of them having taken place before birth. But in the lower animals the successive forms a?e often widely di- verse, and they frequently mark successive stages in the life of the animal. Thus, in Insects, there is the caterpillar or grub stage before the adult ; and in many Crustaceans, Mol- lusks, Worms, and Radiates there are several such stages. Now species have existed, and many now exist, which have the general characters of the forms in these lower stages j and, in accordance with the above proposition, the order of their appearance in the geological series is, in general, as an- nounced by Agassiz, that of their development in the embry- onic series. Thus, as the worm-like grub precedes the adult Insect, so Worms, in geological history, preceded Insects. As a fish-like condition of an Amphibian precedes the adult form in which the fish-like features are lost, so Fishes preceded Am- phibians. The examples of the principle are numerous. Some authors have so great faith in it, that they are ready to decide as to the form of the earliest species of a tribe from the earlier stages in individual development. But this is unsafe, since such forms may have come late into the system of life as well as early; inasmuch as progress was not in all cases upward progress. 288 GEOLOGICAL HISTORY. \Yhere the parallelism above mentioned is not apparent in the general form or structure, it is still manifested in certain comprehensive laws common to both kinds of progress, the geo- logical and embryonic. The following are some of these laws : 1. The low before the relatively hiijh. 2. * Tlie simple before the complex. A germ has little dis- tinction of parts ; the animal it is to evolve is there in a very general condition; that is, without any special organs. As de- velopment of a Mammal goes on, the defining of the head be- gins, and this is one of the first steps in the evolving of special parts, or in the specialization of the structure. Protuberances also form and commence the defining of the limbs ; and then finally, the parts of the limb become distinct, or are specialized. Thus it is throughout the structure, until the specialization of the parts peculiar to the particular animal is completed. This law of the general before the sjieo'ul is a law also in the geological progress of the system of life. In a Fish, the earliest of Vertebrates, the vertebrate structure is exhibited in a very generalized condition. The vertebral column consists of one single uniform range of vertebrae without a neck portion, and without a pelvis to divide the body from a tail and afford support to hind limbs ; the limbs are fins, and hence only rudi- ments of limbs; the vertebrae have great simplicity of form; the teeth are all of the simplest kind ; the lung is merely an air-bladder, and so on. Thus, all through the structure, a Fish is an exhibition of the vertebrate type in a generalized state. The Vertebrates which succeeded to Fishes the Amphibians PROGRESS IN LIFE. 289 have the grand divisions of the body well brought out, and are specialized also as to limbs even to the toes, and in other ways. Passing onward in time, the new Vertebrates appearing exhib- ited successively a more and more complete specialization of organs and functions up to Man. This law of progress from simple to complex has its excep- tions; for Snakes, which are limbless, succeeded to higher Keptiles which had limbs. But such cases only exemplify another fact, already illustrated, that, while upward progress was the rule, there was also progress downward, and especially after the time of culmination of a tribe had passed. 3. Stationary forms sometimes before the locomotive. Thus, Crinoids, part of the earliest life of the globe, were sta- tionary species living attached by a stem; and, after these, there were free Asterioids. So the young of the modern Cri- noid has a stem- for attachment, and loses it, in many species, as it becomes an adult (a Comatulid). 7. Origin of Man. The interval between the Monkey and Man is one of the greatest. The capacity of the brain in the lowest of men is 68 cubic inches, while that in the highest Man Ape is but 34. Man is erect in posture, and has this erectness marked in the form and position of all his bones, while the Man Ape has his inclined posture forced on him by every bone of his skeleton. The highest of Man Apes cannot walk, except for a few steps, without holding on by his fore limbs ; and, instead of having a double curvature in his back like Man, which well-balanced erectness requires, he DANA'S GEOL. STORY 19 290 GEOLOGICAL HISTORY. has but one. The connecting links between Man and any Man Ape of past geological time have not been found, although earnestly looked for. No specimen of the Stone age that has yet been discovered is inferior, as already remarked, to the lowest of existing men; and none is intermediate in essential characters between Man and the Man Ape. The present teaching of geology very strongly confirms the belief that Man is not of Nature's making. Independently of such evidence, Man's high reason, his unsatisfied aspira- tions, his free will, all afford the fullest assurance that he owes his existence to the special act of the Infinite Being whose image he bears. 8. Man the Highest Species. It is sometimes queried whether the future may not have its various new species of life, and, among them, some higher than existing Man ; whether the era now passing is not to be followed, as was true of the Carbonic, or the Reptilian, by another still more glorious in its living species ; whether, if one of the great Dinosaurs of the Mesozoic age could have thought about his own and other times, he would not have imagined his era the last and the best possible ; and whether Man is not playing as foolish a part in styling himself the " lord of creation." Against the introduction of new species in coming time science has little to urge. But there is strong reason for hold- ing that, whatever the changes in the lower tribes, existing Man will always remain the highest in the series. (1) Science has made known that the highest of species PROGRESS IN LIFE. 291 next to Man, that is, the brute Mammals, have already passed their maximum (page 266) ; hence, the rest of time remains for the culmination of the only higher type, that of Man. And, as this type includes now but one species, we have rea- son for expecting no new species in the future. (2) From geological history we learn also that the type of Vertebrates commenced in kinds that were horizontal in attitude, the Fishes; and that from the horizontal there was, in the Reptiles and Mammals, a raising of the head above the line of the body, up to the Ape, in which the attitude is nearly vertical; and, finally, to perfect verticality in Man, a being having the head placed directly over the body and hind limbs. Thus, as Agassiz observed, the last term in the series of Mammals has been reached; there can be nothing beyond. This is true as to the general type of structure ; but it leaves it an open question whether there may not be another species of Man, or erect beings, of still higher grade. (3) But a different species of Man higher than existing Man is not a possibility. We can conceive of other species of Man distinguished by having some of the external fea- tures of the Man Apes. But these are marks of inferiority, and, if possible in a type of so high grade, could belong only to inferior species. The increasing erectness and breadth of forehead in Man, and the shortening of the jaws, giving a nearly vertical line to the front, which are a known result of culture, indi- 292 GEOLOGICAL HISTORY. cate the course which upward progress must take. And in these points and some others closely related, the limits of perfection have been nearly reached by some among the present race. Further improvement can give physically only larger capacity to the brain and greater beauty of form to the whole structure, and make these qualities more general. No wide divergence from existing Man can be conceived of. When all possible change in these directions has been accomplished, Man will still be Man, and no more the head of the system of life than he is at present. (4) Beyond all this we may say, that since no other species but Man has ever been capable of reviewing the past or contemplating the future; and since Man not only has all time and all Nature within the range of his thoiight and study, but can even yoke Nature for service, and in fact has her already at work for him in numberless ways, the system with such a head must be complete. Nature, through Man, has attained to the possession of a living soul capable of putting her once wasted energies into strong and combined movement for social, intellectual, and moral purposes, and this is the consummation that the past has ever had in prospect. The Man of the future is Man triumphant over dying Nature, exulting in the freedom and privileges of spiritual life. INDEX. ACONCAGUA, 87. Acrogens, Carboniferous, 191. Devonian, 173. era of. 134, 145, 184. Lower Silurian, 154. Upper Silurian, 167. Acrotreta, 149. Actinocyclus, 52. Actinolite, 21. Actinoptychus, 51, 52. Adirondacks, 138. Agate, 18. Albite, 20. Algie. See SEAWEEDS. Alleghany Mountains, making of, 114, 208. Alluvial deposits, 67. Alps, elevation of, 247. Glacial period in, 259. glaciers in, 79. Alumina, 19. Aluminum, 14. Amethyst, 17. Ammonites, 217, 231. Ammonoids, 177, 216, 229, 281. Amphibians, 133. Carbonic, 197. era of, 125, 134, 145, 184. Triassic and Jurassic, 218, 220. Amygdaloid, 34. Anchisaurus, 221. Andes, elevation of, 235. Angiosperms, Cretaceous, 229. Tertiary, 242. Animal kingdom, classification of, 125. Anisopus, 219. Anomospus, 219. Anthracite, 189. Anticline, 110. Appalachian Mountain chain, 118. Appalachian Mountain system, 207. Appalachian region, folded rocks of, 110, 204. thickness of formations in, 208. Appalachians, making of, 114, 203. Archaean time, 125, 187. Archseocalamites, 174. Archaeocyathus, 148. Arenig series, 154. Arequipa, 86. Argillaceous sandstone, 31. Argillyte, 81. Aristozoe, 150. Armadillos, Quaternary, 270. Arsenic, 14. Arthrolycosa, 196. Articulates, 131. Cambrian, 149, 151. Carboniferous, 195. Devonian, 176, 178. Lower Silurian, 158. Upper Silurian, 168. Asaphus, 158. Asterophyllites, 174. Astraea, 44, 45. Athyris, 127. Atmosphere, agency of, 58. Atolls, 78. Atrypa, 127. Augite, 21, 22. Aurochs, 278. Avicula, 129. Aymestry limestone, 167. Azoic. See ARCHAEAN. Azurite, 29. BACILLARIA, 51. Bala beds, 154. Barite, 25. Barium sulphate, 25. Barrier reefs, 74. Basalt, 33. Basaltic columns, 37. Base-level, 68. Bear, cave, 266. Beetles, Carboniferous, 195. Belemnitella, 232. Belemnites, 218, 231. Billingsella, 149. Biotite, 21. Birds, 133. Cretaceous, 232. Jurassic, 218, 224. Tertiary, 244, 293 294 INDEX. Bison prisons, 278. Bituminous coal, 189. Black lead. See GRAPHITE. Blue Eidge, 188. Bog iron ore, 27. Bowlder clay, 259. Bowlders, 250. Brachiopods, 127. Cambrian, 148, 151. Carbonic, 187, 195. Devonian, 176. Lower Silurian, 157. Upper Silurian, 168, 169. Brines of Salina, 166. Bryozoans, 127, 128. Lower Silurian, 157. Tipper Silurian, 168. Buthotrephis, 155. CAIRNGORM stone, 17. Calamary, 130. Calamites, 174, 194. Calcareous, rocks, 29, 48. skeletons of animals and plants, 43. tufa, 40. Calciferous sandstone, 153. Calcite, 28. Calcium, 14. Calcium carbonate, 23. action of, in solidification of rocks, 92. Calcium sulphate, 25. Calymene, 158. Cambrian era, 125, 145. Camels, Tertiary, 245, 246. Canadian period, 153. Cannel coal, 189. Carbon, 14. dioxide, 23. Carbonates, 28. Carbonic acid. See CARBON DIOXIDE. Carbonic era, 125, 145, 184. changes of level during, 198. Carboniferous period, 187. Carcharodon, 243. Carcharopsis, 197. Catskill Mountains, 106. Catskill sandstone, 172. Caulopteris, 178. Cave animals of Quaternary, 266. Cenozoic time, 125, 287. Centipedes. See MYRIAPODS. Cephalaspis, 182. Cephalopods, 180. Cambrian, 151. Cretaceous, 281. Devonian, 177. Lower Silurian, 157. Triassic and Jurassic, 215. Cervus megaceros, 267. Cestracion, 179. Chain coral, 169. Chalcopyrite, 28. Chalk, 29, 50, 228. Champlain, Lake, in the Quaternary, 263. Champlain period, 250, 262. subsidence in, 263. Chazy limestone, 153, Chelonians. See TURTLES. Chemical work of air and moisture, 58. Chemung beds, 172. Chlorite, 23. Chrysalidina, 48, 230. Chrysolite. 23. Circumdenudation, 106. Clam, 242. Clay, 30. slate, 31. Cleavage, 15. Climate, in Carbonic era, 195. in Champlain period, 262. in Glacial period, 256. in Tertiary era, 242. progress of, in geological time, 283. sudden change of, at close of Champlain period, 271. Clinometer, 7. Clinton group, 165. Coal, impurities of, 189. kinds of, 189. origin of, 190. sulphur in, 190. Coal-areas in eastern North America, 188. in Europe, 188. in Eocky Mountain region, 228. Coal-beds in Carboniferous, 189. in Cretaceous, 228. in Triassic, 210. thickness of, 189. Coal-measures, 187. thickness of, 188. Coccoliths, 50. Coccosteus, 182. Cockroaches, 169, 195. Colorado, canon of, 86, 102, 280. Columnar structure, 87. Columnaria, 155, 156. Conformable strata, 118. Conglomerate, 80. Conifers, Carboniferous, 191, 195. Cretaceous, 280. Devonian, 175. Triassic and Jurassic, 214. Connecticut River, terraces of, 276. Connecticut Valley, footprints in, 219. sandstones, 209. INDEX. 295 trap ridges, 119. trap rocks, 211. Continents, bordered by mountain ranges, 116. defined in Archaean time, 138. origin of, 120. Contraction of earth, a cause of change of level, 116. Contraction of rocks, effect of, 84. Cooling of globe, effects of, 116, 120. Copper ores, 28, 29. Coral reefs and islands, 73. Corallines, 50. Corals, 43. 126. Cambrian, 147. Carbonic, 187, 195. Devonian, 176. Lower Silurian, 155. Triassic and Jurassic, 214. Upper Silurian, 168. Cordaites, 175. Corniferous limestone, 171. Coscinodiscus, 52. Cotopaxi, 86. Crassatella, 242. Crepidula, 243. Cretaceous period, 209, 226. map of North America in, 227. Crevasses, 81. Crickets, Carboniferous, 195. Crinoidal limestone, 50, 186. Crinoids, 46, 127. Cambrian, 147. Carbonic, 186, 195. Devonian, 176. Lower Silurian, 155, 156. Triassic and Jurassic, 214. Tipper Silurian, 168. Crocodiles, 222, 232, 244. Cro-Magnon skull, 274. Crustaceans, 131. Cambrian, 149, 151. Carboniferous, 195. Devonian, 176, 178. Lower Silurian, 158. Upper Silurian, 168, 169. Cryptogams, Cambrian, 147. Carboniferous, 191. Devonian, 178. Lower Silurian, 154. Triassic and Jurassic, 214. Upper Silurian, 167. Crystalline rocks, 31, 93. structure, 14. Culmination of types, 286. Cuneolina, 48, 230. Currents, oceanic, 74. wind-made, 72. Cyanite, 23. Cyathophylloid corals, 155, 168, 176, 185. Cycads, 176, 214, 230. Cycas, 213. Cypraaa, 248. DAPEDIUS, 219. Da\vkins, W. B., on human relics, 275. Decapods, 150. Decay of rocks, 58. Deep-sea life, 56. Deer, Irish, 267. Delta of Mississippi, 66. Denudation, 66. Devonian era, 125, 145, 170. hornstone, 171. Diamond, 14. Diatoms, 51. Diceras, 215, 216. Dictyocha, 52. Dikes, 85. Dinosaurs, 220, 229, 232. Dip, 108. Dipnoans, 179, 182. Dipterus, 180. Dismal Swamp, 58. Dodo, 278. Doleryte. See TRAP. Dolomite, 24, 29. Drift, 250. sands, 61. scratches, 253. Dromatherium, 226. Dunes, 61. Dynamical geology, 39. EARLY Paleozoic, 145. Earth, earliest condition of, 137. progress in features, 282. Earthquakes, 114. Eifel limestone, 172. Elephant, picture of, engraved on ivory, 273. Elephants, Quaternary, 268, 269, 271. Tertiary, 246. Embryology and paleontology, parallelism of, 287. Emery, 19. Enaliosaurs, 222, 232. England, geological map of, 212. Eoblattina, 196. Eocene period, 237. Eozoon, 143. Ephemera', 178. Epidote, 23. Equiseta, Carboniferous, 191, 193. Devonian, 173. Eras, geological, table of, 135. Erosion, 64, 70. 296 INDEX. Eschara, 128. Euplectella, 55. Eurylepis, 197. Evolution, 285. Exogyra, 215, 216. Expansion of rocks, effect of, 84. FALSE Topaz, 17. Faults, 112, 205. Favosites, 176. Features of earth, development of, 282. Feldspar, 20. Ferns, Carboniferous, 191. Devonian, 173. Triassic and Jurassic, 214. Fingal's Cave, 248. Fishes, 132, 133. Carbonic, 196. Cretaceous, 232. Devonian, 179. Lower Silurian, 159 reign of, 125, 145. Tertiary. 243. Triassic and Jurassic, 218. Upper Silurian, 168, 169. Fish-spines, 179. Flabellina, 48, 230. Flabellum, 46. Flags, 31, 172. Flexures of strata, 109. Flint, 17, 54. arrow-heads, 271. Folded rocks, 109. Footprints. See TRACKS. Foraminifers, 48. Fordilla, 149. Fossils, criterion of age of strata, 123. Fractures of rocks, 112. Fragmental rocks, 41. Freezing, expansion in, 78. Fresh waters, action of, 63. Fringing reefs, 74. Frondicularia, 48. Fruits, fossil, 195. Fusion, rocks formed from, 89. Fusulina, 48. GALENA, 28. limestone, 154. Galenlte, 28. Ganoids, Carboniferous, 196. Cretaceous, 232. Devonian, 179, 180. Lower Silurian, 159. Triassic and Jurassic, 218. Upper Silurian, 170. Garnet, 22. Gars. See GANOIDS. Gas, natural, 160. Gastropods, 129. Cambrian, 148, 151. Geological time, length of, 280. Geology, definition of, 11. Geysers, 90. Giant's Causeway, 34, 248. Glacial period, 250. cause of climate, 256. limit of ice-sheet in North America, 259. phenomena due to glaciers, 254. second, of Europe, 264, 275. thickness of ice in North America, 255. Glaciers, 79. movement of, 80, 256. scratches made by, 81, 82, 253. Globigerina, 48. Glyptodon, 270. Gneiss, 32. Goniatites, 177, 217. Corner Glacier, 80. Grammatophora, 51, 52. Grammostomuiu, 48. Granite, 31. Graphite, 14, 143. Gravel, 31. Green Mountains, scratches and bowlders on, 253. Greenland, changes of level in, 278. Greensand, 228, 241. Ground pines. See LYCOPODS. Gryphsea, 214, 216. Gulf Stream, 74. Gymnosperms, Carboniferous, 191, 195. Cretaceous, 230. Devonian, 175. Triassic and Jurassic, 214. Gypsiferous formation, Triassic, 211. Gypsum, 25, 166. HADROSAURUS, 222. Halonia, 194. Halysites, 168. Hamilton group, 172. Hammer, geological, 6. Hawaii, volcanoes of, 88. Heat, effects of, 84. Height of volcanic peaks, 86. Helderberg. See LOWER HELDERBBHG, UP- PER HELDERBERG. Hematite, 27, Hesperornis, 233. Highlands of New York and New Jersey. 138. Himalayas, elevation of, 248. Hippopotamus, 244, 245. Historical geology, 122. Holopea, 151. INDEX. 297 Holoptychius, 180. Homalonotus, 169. Hood, Mount, 248. Hornblende, 21, 22. schist, 33. Hornstone, 17, 54, 171. Horses, Quaternary, 267, 269. Tertiary, 246, 246. Hot springs, 90. Hudson Kiver shales, 154. Human skeletons, fossil, 274. Hyaena, cave, 267. Hydrogen, 14. Hydromica schist, 32. Hyolithes, 149. ICE, geological work of, 78. of glaciers, 81, 256. of rivers and lakes, 78. Icebergs, 83. Ichthyocrinus, 168. Ichthyosaurus, 222. Igneous rocks, 39. Tertiary, 248. Triassic, 211. Iguaiiodon, 222. Infusorial earth, 51. Insects, 181. Carboniferous, 195. Devonian, 178. Lower Silurian, 159. Upper Silurian, 168, 169. Invertebrates, 133. Irish deer, 267. Iron Mountains of Missouri, 140. Iron ores, 25, 140. Isopods, 150. JOINTS in rocks, 113. Jorullo, 87. Jurassic period, 209. KILAUEA, 88. Kitchen middens, 278. LABRADOKITE, 20. Lacertilians. See LIZARDS. Lakes of Rocky Mountain region in the Tertiary, 238. Lainellibranchs, 129. Cambrian, 148. Tertiary, 242. Triassic and Jurassic, 214. Laramide Mountain system, 235. Later Paleozoic, 145, 163. Lateral pressure in earth's crust, 115. Laurentide Plateau, center of glaciation for North America, 257. Lava, 33. Layer, 36. Lead ore, 28. Lepidodendron, 175, 194. Lepidoganoids, 179, 180. Lepidosteus, 181. Leptaena, 157, 168. Leptomitus, 148. Level, Quaternary changes of, 256, 262, 275. Kecent changes of, in Sweden, Green- land, and United States, 277. Lias, 213. Lichas, 169. Life, agency of, in rock-making, 43. Archffian, 142. Cambrian, 147. Carbonic, 191. changes of, at close of Paleozoic, 208. Cretaceous, 229. Early Paleozoic, 159. Lower Silurian, 154. Pleistocene, 265. progress of, in geological time, 284. progress of, in Mesozoic, 233. Tertiary, 241. Triassic and Jurassic, 214. Upper Silurian, 167. Lignite, 239. Lignitic beds, Tertiary, 239. Lime, 19. Limestone, 24, 29. formation of, 40, 43. Limonite, 27. Lingulella, 151. Lingulepis, 151. Lion, cave, 267. Liriodendron, 229. Lithostrotion, 185. Lituola, 48, 280. Lizards, 222, 244. Llandeilo flags, 154. Loa, Mauna, 87, 88. Loligo, 130. Lower Helderberg period, 164, 166. Lower Silurian era, 125, 145, 153. Ludlow group, 167. Lycopods. Carboniferous, 191, 193. Devonian, 174. Upper Silurian, 167. MADREPOBA, 44. Madrepores, 44. Magnesia, 19. Magnesian limestone, 24, 29. Magnesium, 14. Magnetic iron ore, 26. Magnetite, 26. 298 INDEX. Magnolia, 248. Malachite, 29. Mammals, 138, 184. Cretaceous, 288. era of, 125, 287. Quaternary, 266. Tertiary, 244. Triassic and Jurassic, 218, 225. Man, era of, 125, 287, 249. fossil skeletons of, 274. head of the system of life, 290. origin of, 289. relics of, 271. Mansfield, Mount, glacial scratches on, 253. Map of England, 212. Map of North America, Archsean, 189. Cretaceous, 227. Paleozoic, 164. post-Paleozoic, 207. Quaternary, 251, 260. Tertiary, 238. Map of United States. 136. Marble, 29. Marsupials, Cretaceous, 238. Quaternary, 270. Triassic and Jurassic, 225. Mastodon, Quaternary, 268. Tertiary, 245, 246. Mauna Loa, 87, 88. May-flies, Carboniferous, 195. Devonian, 178. Medina sandstone, 165. Megalosaur, 221. Megatherium, 269. Melosira, 51, 52. Mentone skeleton, 274. Mesas, 107. Mesozoic time, 125, 209. progress of life in, 233. Metamorphic rocks, 42, 95. Metamorphism, 93, 114. Methods of study in geology, 3. Miamia, 196. Mica, 21. schist, 82. Millstone grit, 187. Mineral coal. See COAL. Mineral oil. See OIL. Miocene period, 237. Mississippi River, delta of, 66. sediment of, 66. Mississippi Valley in Quaternary, 264. Missouri iron ores, 140. Moa, 278. Molluscoids, 127. Cambrian, 148, 151. Carboniferous, 195. Devonian, 176. Lower Silurian, 157. Subcarboniferous, 186. Upper Silurian, 168. Mollusks, 128. Cambrian, 148, 151. Carboniferous, 195. Cretaceous, 231. Devonian, 177. Lower Silurian, 157. Tertiary, 242. Triassic and Jurassic, 214. Monocline, 112. Monotremes, 225, 226, 288. Monument Park, 107. Moraine, 82. Mosasaur, 232. Mountain chains, 118. Mountain ranges, making of material for, 114. Mountain-making, cause of, 115. Cenozoic, 246. Mesozoic, 234. Paleozoic, 161, 183. post-Mesozoic, 235. post-Paleozoic, 202. Mountains made by erosion, 106. by flexures of crust, 108. by igneous ejections, 105. Mud, 30. Mud-cracks, 76. Murchisonia, 129. Muscovite, 21. Myriapods, 131, 195. NATUKE, system of, has beginning and end, 283. Nautilus, 131. Navicula, 52. Neanderthal skull, 273. Neolithic epoch, 278. Neuropteris, 173, 193. New Jersey coast, subsidence of, 278. Niagara period, 164, 165. Niagara River, gorge of, 281. Niagara shale and limestone, 165. Night heron, extinct, 279. Nodosaria, 48. Non-articulates, 127. North America, map of, Archiwin, 139. Cretaceous, 227. Paleozoic, 104. post-Paleozoic, 207. Quaternary, 251, 26(1. Tertiary, 238. North America, Recent changes of level in, 278. Nova Scotia coal measures, 188, 201. Nova Scotia range, 206. INDEX. 299 Nullipores, 50. Nummulites, 48, 49, 240. Nummulltic limestone, 240. Nuts, fossil, 195. OCEAN, geological work of, 69, 104. life in depths of, 56. Oceanic basin, origin of, 120. Odontidium, 52. Oil, mineral, 160. Old red sandstone, 172. Olenellus, 150. Olivine, 23. Onondaga period, 164, 166. Onychadus, 181. Oolyte, 213. Opal, 18. Orbulina, 48. Ores, 25. Organic remains, rocks made of, 41. Oriskany sandstone, 171. Orthis, 149, 157, 168. Orthisina, 149. Orthoceras, 157, 158. Orthoclase, 20. Ostracoids, 149, 159. Ostrea, 216, 242. Otozoum, 219. Ouachita range, 207. Oxen, first of, 246. Oxygen, 13. Oyster, Tertiary, 242. PAL.SASPIS, 170. Palseaster, 156. Palseohatteria, 199. Palieopalsemon, 178. Paleolithic epoch, 272. Paleozoic time, 125, 144. change in life at close of, 208. geographical progress during, 201. Palisades, 209, 211. Palms, Cretaceous, 229. Tertiary, 242. Paradoxides, 151. Peat beds, 57. Pelion, 198. Pentacrinus, 47, 214, 215. Pentremites, 185. Permian period, 191. Phsenogams, Carboniferous, 191, 195. Cretaceous, 229. Devonian, 175. Triassic and Jurassic, 214. Phillipsastrwa, 176. Pinnularia, 51, 52. Placenticeras, 231. Placoderms, 169, 179, 181. Platephemera, 178. Platyceras, 149. Pleistocene, 250. Plesiosaurus, 223. Pleurocystites, 156. Pleurosigma, 51. Pleurotomaria, 129. Pliocene period, 237. Plumbago. See GRAPHITE. Poebrotherium, 246. Polycystines. See RADIOLARIANS. Polyps, 43, 126. Polythalamia. See FORAMINIFERS. Porcellio, 150. Porphyry, 85, Portage group, 172. Portland dirt bed, 218. Post-Mesozoic revolution, 235. Post-Paleozoic revolution, 202. Post-Tertiary. See QUATERNARY. Potash, 19. Potassium, 14. Potsdam sandstone, 146, 147. Primordial. See CAMBRIAN. Productus, 186. Progress of life, 284. Protannularia, 155. Protocaris, 150. Protozoans, 126. Archaean, 148. Cambrian, 147. Cretaceous, 231. Lower Silurian, 155. Tertiary, 240. Pterichthys, 182. Pterodactylus, 224. Pteropods, 129, 130, 148. Pteropsis, 242. Pterosaurs, 223, 229, 232. Ptilodictya, 128. Pudding-stone, 30. Pyrenees, 247. Pyrite, 25. Pyroxene, 21. QUARTZ, 16. Quartz-syenyte, 33. Quaternary era, 125, 237, 249. Quicklime, 19. RADIATES, 126. Cambrian, 147. Carbonic, 186, 195. Devonian, 176. Lower Silurian, 155. Triassic and Jurassic, 214. Upper Silurian, 168. Radiolarians, 53, 126. 300 INDEX. Rain-prints, 77. Raritan clays, 228. Recent period, 250, 275. Reefs, coral, 73. Regional metamorphism, 94. Reindeer epoch, 265, 272, 275. Reptiles, 133. Cretaceous, 232. Permian, 197. reign of, 125, 209. Tertiary, 244. Trias&ic and Jurassic, 218, 220. Reptilian era, 209. Revolution, post-Mesozoic, 235. post-Paleozoic, 202. Rhamphorhynchus, 225. Rhinoceroses, Quaternary, 268, 271. Tertiary, 244, 245. Rhizopods, 48, 126. Archsean, 143. Cretaceous, 231. Lower Silurian, 155. Rhynchonella, 128. Ripple-marks, 75. River systems, development of, 282. River terraces, 276. Rivers, action of, 64. Roches moutonnees, 82, 259. Rocks, Archsean, 138. calcareous, 29, 43. Cambrian, 145. Carboniferous, 187. Cretaceous, 226. crystalline, 81, 93. Devonian, 171. fragrnental, 29, 41. igneous, 39. kinds of, 29. Lower Silurian, 158. making of, 39. metamorphic, 42, 95. Permian, 191. schistose, 82. sedimentary, 29, 41. solidification of, 92. stratified, 85. structure of, 35. Subcarboniferous, 184, 186. Tertiary, 287. thickness of Paleozoic, 161, 203. Triassic and Jurassic, 209. unstratified, 87. Upper Silurian, 165. Rocky Mountain coal-areas, 228. Rocky Mountains, elevation of, 235, 247. glaciation of, 258. igneous rocks in, 248. Rotalia, 48, 49. ST. LAWRENCE RIVER in the Quaternary, 263. St. Peter's sandstone, 153. Saliferous group in Europe, 211. Saliferous rocks in New York, 166. Salina rocks, 166. Salix, 229. Salt of New York and Canada. 166. of Onondaga period, 166. of Triassic period, 211. Sand, 30. scratches, 63. Sand-fleas, 150. Sandstone, 29. Sapphire, 19. Sassafras, 229. Scaphites, 231. Schist, schistose rocks, 32. Scoria, 34. Scorpions, Carboniferous, 195. Upper Silurian, 168. Scratches, glacial, 81, 82, 253. Sea-beaches, elevated, 263. Sea-saurians, 222, 232. Seaweeds, 143, 147, 154, 173. Sedimentary rocks, great extent of, 77. Selachians. See SHARKS. Sequoia, 243. Serolis, 150. Serpentine, 23. Shale, 30. Sharks, Carbonic, 196. Cretaceous, 232. Devonian, 179. Tertiary, 243. Upper Silurian, 170. Shasta, Mount, 86, 248. Shells, rocks made of, 43. Siderite, 28. Sierra Nevada, elevation of, 234. glaciation of, 258. Sigillaria, 175, 194. Silex, 52. Silica, 16. action of, in solidification of rocks, 92. Silicates, 19. Siliceous skeletons of animals and plants, 51. Silicon, 18. Silurian. See LOWER SILURIAN, UPPER 81- HTBIAN. Skeletons of man, fossil, 274. Slate, 31. Sloths, gigantic, of Quaternary, 269. Snails, Carboniferous, 195. Snakes, 244. Soapstone, 22. Soda, 20. Sodium, 14. Solfataras, 90. INDEX. 301 Solidification of rocks, 92. Solitaire, 279. Solution, rocks fanned from, 40. Sow-bugs, 150. Spathic iron ore, 28. Specimens required for study, 5. Specular iron ore, 27. Sphagnum, 57. Sphenopteris, 193. Spicules of sponges, 53, 54. Spiders, 131, 195. Spirifer, 127, 168, 186. Spirocyathus, 148. Sponges, 126. Cambrian, 147. Lower Silurian, 155. Spongiolithis, 52. Springs, hot, 90. Squid, 130. Stalactite, 40. Stalagmite, 40. containing bones of cave animals, 266. Star-fishes 155, 156. Staurolite, 23. Stenotheca, 149. Stone age, 272, 278. Strata, age of, how determined, 123. flexures of, 109. Stratified drift, 254. Stratified rocks, 35. Stratum, defined, 86. Streptelasma, 155. Strike, 108. Styliola, 129. Subcarboniferous period, 184. Sulphates, 25. Sulphur, 14. Sweden, Recent changes of level in, 277. Syenyte, 33. Syenyte-gneiss, 33. Syncline, 110. TABLE of geological eras, 135. Taconic Mountains, 161. Tseniaster, 156. Tails of fishes, 182. Talc, 22. Tapir, 244. Taxocrinus, 156. Teleost fishes, 232. Temperature, expansion and contraction of rocks by changes of, 34. Terebratula, 127. Terebratulina, 127. Terrace period. See RECENT PERIOD. Terraces along rivers, '276. Tertiary era, 125, 237. Tetradecapods, 150. Textularia, 48. Thecocyathus, 45. Tides, geological i-UVct of, 69. Till, 254. Tina', peologic.il, length of, 280. Tinoceras, 245. Tourmaline, 23. Trachyte, 35. Tracks of reptiles and amphibians, 218. Trap, 33. columnar, 37. of Connecticut Valley, 211. Travertine, 40. Tree-ferns, 173, 192. Tremolite, 21. Trenton limestone, 153. Trenton period, 153. Triarthrus, 158. Triassic period, 209. Triceratiutn, 52. Triceratops, 233. Trigonia, 215, 216. Trigonocarpus, 195. Trilobites, Cambrian, 149, 151. Carbonic, 195. Devonian, 176. Lower Silurian, 158. reign of, 125, 145. Upper Silurian, 168, 169. Triloculina, 48. Tufa, 85. calcareous, 40. Turritella, 242. Turtles, 222, 282, 244. UNOONFORMABLE strata, 113. Underclay, 190. United States, geological map of, 136. Unstratified drift, 254. Un stratified rocks, 37. Upper Helderberg limestone, 171. Upper Silurian era, 125, 145, 164. Utica shales, 154. VALLEYS made by erosion, 101. by fractures of crust, 104. by upheaval of mountains, 104. Vapor, agency of, in volcanoes, 88. Veins, 96. Vein-stones, 98. Venericardia, 242. Vertebrates, 181. Carbonic, 196. Cretaceous, 232. Devonian, 179. Lower Silurian, 159. Quaternary. 'JCC. Tertiary, 243. 302 INDEX. Triassic and Jurassic, 218. Upper Silurian, 168, 169. Vesuvius, 88. Volcanic cones, slopes of, 87. Volcanic rocks, 33. Volcanoes, 85. WALDHEIMIA, 127. Wasatch range, 235. Washington, Mount, bowlders on, 253. Water, action of fresh, 63. action of oceanic, 69. freezing and frozen, 78. Waterfalls, 65. Waves, action of, 70. Wealden, 212. Weathering, 58. Wenlock limestone, 165. West Rock, 210. White Mountains, alpine plants on, 265. Wind-drift structure, 61. Winds, effects of, 61. Woodocrinus, 185. Worms, 131, 149, 152, 158. XYLOBIUS, 196. YELLOWSTONE PARK, 90. ZAPHRENTIS, 168, 176. University of California SOUTHERN REGIONAL LIBRARY FACILITY 305 De Neve Drive - Parking Lot 17 Box 951388 LOS ANGELES, CALIFORNIA 90095-1388 Return this material to the library from which it was borrowed. Phys.Sci. A 000 642" 783" 5 QE28 Dana, James D. 2 Phys.Sci. QE28 Dana, James D. D22 The geological story briefly told. >ATE LOANEDJ ISSUED TO DATE DUE Physical Sciences Library University of California Riverside