CHAPTER XXII. The Quaternary

THE QUATERNARY

The last period of geological history, the Quaternary, may be said to have begun when all, or nearly all, living species of mollusks and most of the existing mammals had appeared.

It is divided into two great epochs. The first, the Pleistocene or Glacial epoch, is marked off from the Tertiary by the occupation of the northern parts of North America and Europe by vast ice sheets; the second, the Recent epoch, began with the disappearance of the ice sheets from these continents, and merges into the present time.

The Pleistocene Epoch

We now come to an episode of unusual interest, so different was it from most of the preceding epochs and from the present, and so largely has it influenced the conditions of man's life.

The records of the Glacial epoch are so plain and full that we are compelled to believe what otherwise would seem almost incredible,--that following the mild climate of the Tertiary came a succession of ages when ice fields, like that of Greenland, shrouded the northern parts of North America and Europe and extended far into temperate latitudes.

=The drift.= Our studies of glaciers have prepared us to decipher and interpret the history of the Glacial epoch, as it is recorded in the surface deposits known as the drift. Over most of Canada and the northern states this familiar formation is exposed to view in nearly all cuttings which pass below the surface soil. The drift includes two distinct classes of deposits,--the unstratified drift laid down by glacier ice, and the stratified drift spread by glacier waters.

The materials of the drift are in any given place in part unlike the rock on which it rests. They cannot be derived from the underlying rock by weathering, but have been brought from elsewhere. Thus where a region is underlain by sedimentary rocks, as is the drift-covered area from the Hudson River to the Missouri, the drift contains not only fragments of limestone, sandstone, and shale of local derivation, but also pebbles of many igneous and metamorphic rocks, such as granites, gneisses, schists, dike rocks, quartzites, and the quartz of mineral veins, whose nearest source is the Archean area of Canada and the states of our northern border. The drift received its name when it was supposed that the formation had been drifted by floods and icebergs from outside sources,--a theory long since abandoned.

The distribution also of the drift points clearly to its peculiar origin. Within the limits of the glaciated area it covers the country without regard to the relief, mantling with its debris not only lowlands and valleys but also highlands and mountain slopes.

The boundary of the drift is equally independent of the relief of the land, crossing hills and plains impartially, unlike water-laid deposits, whose margins, unless subsequently deformed, are horizontal. The boundary of the drift is strikingly lobate also, bending outward in broad, convex curves, where there are no natural barriers in the topography of the country to set it such a limit. Under these conditions such a lobate margin cannot belong to deposits of rivers, lakes, or ocean, but is precisely that which would mark the edge of a continental glacier which deployed in broad tongues of ice.

=The rock surface underlying the drift.= Over much of its area the drift rests on firm, fresh rock, showing that both the preglacial mantle of residual waste and the partially decomposed and broken rock beneath it have been swept away. The underlying rock, especially if massive, hard, and of a fine grain, has often been ground down to a smooth surface and rubbed to a polish as perfect as that seen on the rock beside an Alpine glacier where the ice has recently melted back. Frequently it has been worn to the smooth, rounded hummocks known as roches moutonnées, and even rocky hills have been thus smoothed to flowing outlines like roches moutonnées on a gigantic scale. The rock pavement beneath the drift is also marked by long, straight, parallel scorings, varying in size from deep grooves to fine striae as delicate as the hair lines cut by an engraver's needle. Where the rock is soft or closely jointed it is often shattered to a depth of several feet beneath the drift, while stony clay has been thrust in among the fragments into which the rock is broken.

In the presence of these glaciated surfaces we cannot doubt that the area of the drift has been overridden by vast sheets of ice which, in their steady flow, rasped and scored the rock bed beneath by means of the stones with which their basal layers were inset, and in places plucked and shattered it.

=Till.= The unstratified portion of the drift consists chiefly of sheets of dense, stony clay called till, which clearly are the ground moraines of ancient continental glaciers. Till is an unsorted mixture of materials of all sizes, from fine clay and sand, gravel, pebbles, and cobblestones, to large bowlders. The stones of the till are of many kinds, some having been plucked from the bed rock of the locality where they are found, and others having been brought from outside and often distant places. Land ice is the only agent known which can spread unstratified material in such extensive sheets.

The fine material of the till comes from two different sources. In part it is derived from old residual clays, which in the making had been leached of the lime and other soluble ingredients of the rock from which they weathered. In part it consists of sound rock ground fine; a drop of acid on fresh, clayey till often proves by brisk effervescence that the till contains much undecayed limestone flour. The ice sheet, therefore, both scraped up the mantle of long-weathered waste which covered the country before its coming, and also ground heavily upon the sound rock underneath, and crushed and wore to rock flour the fragments which it carried.

The color of unweathered till depends on that of the materials of which it is composed. Where red sandstones have contributed largely to its making, as over the Triassic sandstones of the eastern states and the Algonkian sandstones about Lake Superior, the drift is reddish. When derived in part from coaly shales, as over many outcrops of the Pennsylvanian, it may when moist be almost black. Fresh till is normally a dull gray or bluish, so largely is it made up of the grindings of unoxidized rocks of these common colors.

Except where composed chiefly of sand or coarser stuff, unweathered till is often exceedingly dense. Can you suggest by what means it has been thus compacted? Did the ice fields of the Glacial epoch bear heavy surface moraines like the medial and lateral moraines of valley glaciers? Where was the greater part of the load of these ice fields carried, judging from what you know of the glaciers of Greenland?

=Bowlders of the drift.= The pebbles and bowlders of the drift are in part stream gravels, bowlders of weathering, and other coarse rock waste picked up from the surface of the country by the advancing ice, and in part are fragments plucked from ledges of sound rock after the mantle of waste had been removed. Many of the stones of the till are dressed as only glacier ice can do; their sharp edges have been blunted and their sides faceted and scored.

We may easily find all stages of this process represented among the pebbles of the till. Some are little worn, even on their edges; some are planed and scored on one side only; while some in their long journey have been ground down to many facets and have lost much of their original bulk. Evidently the ice played fast and loose with a stone carried in its basal layers, now holding it fast and rubbing it against the rock beneath, now loosening its grasp and allowing the stone to turn.

Bowlders of the drift are sometimes found on higher ground than their parent ledges. Thus bowlders have been left on the sides of Mount Katahdin, Maine, which were plucked from limestone ledges twelve miles distant and three thousand feet lower than their resting place. In other cases stones have been carried over mountain ranges, as in Vermont, where pebbles of Burlington red sandstone were dragged over the Green Mountains, three thousand feet in height, and left in the Connecticut valley sixty miles away. No other geological agent than glacier ice could do this work.

The bowlders of the drift are often large. Bowlders ten and twenty feet in diameter are not uncommon, and some are known whose diameter exceeds fifty feet. As a rule the average size of bowlders decreases with increasing distance from their sources. Why?

=Till plains.= The surface of the drift, where left in its initial state, also displays clear proof of its glacial origin. Over large areas it is spread in level plains of till, perhaps bowlder-dotted, similar to the plains of stony clay left in Spitzbergen by the recent retreat of some of the glaciers of that island. In places the unstratified drift is heaped in hills of various kinds, which we will now describe.

=Drumlins.= Drumlins are smooth, rounded hills composed of till, elliptical in base, and having their longer axes parallel to the movement of the ice as shown by glacial scorings. They crowd certain districts in central New York and in southern Wisconsin, where they may be counted by the thousands. Among the numerous drumlins about Boston is historic Bunker Hill.

Drumlins are made of ground moraine. They were accumulated and given shape beneath the overriding ice, much as are sand bars in a river, or in some instances were carved, like roches moutonnées, by an ice sheet out of the till left by an earlier ice invasion.

=Terminal moraines.= The glaciated area is crossed by belts of thickened drift, often a mile or two, and sometimes even ten miles and more, in breadth, which lie transverse to the movement of the ice and clearly are the terminal moraines of ancient ice sheets, marking either the limit of their farthest advance or pauses in their general retreat.

The surface of these moraines is a jumble of elevations and depressions, which vary from low, gentle swells and shallow sags to sharp hills, a hundred feet or so in height, and deep, steep-sided hollows. Such tumultuous hills and hummocks, set with depressions of all shapes, which usually are without outlet and are often occupied by marshes, ponds, and lakes, surely cannot be the work of running water. The hills are heaps of drift, lodged beneath the ice edge or piled along its front. The basins were left among the tangle of morainic knolls and ridges (Fig. 105) as the margin of the ice moved back and forth. Some bowl-shaped basins were made by the melting of a mass of ice left behind by the retreating glacier and buried in its debris.

=The stratified drift.= Like modern glaciers the ice sheets of the Pleistocene were ever being converted into water about their margins. Their limits on the land were the lines where their onward flow was just balanced by melting and evaporation. On the surface of the ice along the marginal zone, rivulets no doubt flowed in summer, and found their way through crevasses to the interior of the glacier or to the ground. Subglacial streams, like those of the Malaspina glacier, issued from tunnels in the ice, and water ran along the melting ice front as it is seen to do about the glacier tongues of Greenland. All these glacier waters flowed away down the chief drainage channels in swollen rivers loaded with glacial waste.

It is not unexpected therefore that there are found, over all the country where the melting ice retreated, deposits made of the same materials as the till, but sorted and stratified by running water. Some of these were deposited behind the ice front in ice-walled channels, some at the edge of the glaciers by issuing streams, and others were spread to long distances in front of the ice edge by glacial waters as they flowed away.

Eskers are narrow, winding ridges of stratified sand and gravel whose general course lies parallel with the movement of the glacier. These ridges, though evidently laid by running water, do not follow lines of continuous descent, but may be found to cross river valleys and ascend their sides. Hence the streams by which eskers were laid did not flow unconfined upon the surface of the ground. We may infer that eskers were deposited in the tunnels and ice-walled gorges of glacial streams before they issued from the ice front.

Kames are sand and gravel knolls, associated for the most part with terminal moraines, and heaped by glacial waters along the margin of the ice.

i, glacier ice; t, t, terraces]

Kame terraces are hummocky embankments of stratified drift sometimes found in rugged regions along the sides of valleys. In these valleys long tongues of glacier ice lay slowly melting. Glacial waters took their way between the edges of the glaciers and the hillside, and here deposited sand and gravel in rude terraces.

Outwash plains are plains of sand and gravel which frequently border terminal moraines on their outward face, and were spread evidently by outwash from the melting ice. Outwash plains are sometimes pitted by bowl-shaped basins where ice blocks were left buried in the sand by the retreating glacier.

Valley trains are deposits of stratified drift with which river valleys have been aggraded. Valleys leading outward from the ice front were flooded by glacial waters and were filled often to great depths with trains of stream-swept drift. Since the disappearance of the ice these glacial flood plains have been dissected by the shrunken rivers of recent times and left on either side the valley in high terraces. Valley trains head in morainic plains, and their material grows finer down valley and coarser toward their sources. Their gradient is commonly greater than that of the present rivers.

=The extent of the drift.= The extent of the drift of North America and its southern limits are best seen in Figure 359. Its area is reckoned at about four million square miles. The ice fields which once covered so much of our continent were all together ten times as large as the inland ice of Greenland, and about equal to the enormous ice cap which now covers the antartic regions.

The ice field of Europe was much smaller, measuring about seven hundred and seventy thousand square miles.

=Centers of dispersion.= The direction of the movement of the ice is recorded plainly in the scorings of the rock surface, in the shapes of glaciated hills, in the axes of drumlins and eskers, and in trains of bowlders, when the ledges from which they were plucked can be discovered. In these ways it has been proved that in North America there were three centers where ice gathered to the greatest depth, and from which it flowed in all directions outward. There were thus three vast ice fields,--one the Cordilleran, which lay upon the Cordilleras of British America; one the Keewatin, which flowed out from the province of Keewatin, west of Hudson Bay; and one the Labrador ice field, whose center of dispersion was on the highlands of the peninsula of Labrador. As shown in Figure 359, the western ice field extended but a short way beyond the eastern foothills of the Rocky Mountains, where perhaps it met the far-traveled ice from the great central field. The Keewatin and the Labrador ice fields flowed farthest toward the south, and in the Mississippi valley the one reached the mouth of the Missouri and the other nearly to the mouth of the Ohio. In Minnesota and Wisconsin and northward they merged in one vast field.

From Salisbury's Glacial Geology of New Jersey]

The thickness of the ice was so great that it buried the highest mountains of eastern North America, as is proved by the transported bowlders which have been found upon their summits. If the land then stood at its present height above sea level, and if the average slope of the ice were no more than ten feet to the mile,--a slope so gentle that the eye could not detect it and less than half the slope of the interior of the inland ice of Greenland,--the ice plateaus about Hudson Bay must have reached a thickness of at least ten thousand feet.

In Europe the Scandinavian plateau was the chief center of dispersion. At the time of greatest glaciation a continuous field of ice extended from the Ural Mountains to the Atlantic, where, off the coasts of Norway and the British Isles, it met the sea in an unbroken ice wall. On the south it reached to southern England, Belgium, and central Germany, and deployed on the eastern plains in wide lobes over Poland and central Russia (Fig. 360).

At the same time the Alps supported giant glaciers many times the size of the surviving glaciers of to-day, and a piedmont glacier covered the plains of northern Switzerland.

=The thickness of the drift.= The drift is far from uniform in thickness. It is comparatively thin and scanty over the Laurentian highlands and the rugged regions of New England, while from southern New York and Ontario westward over the Mississippi valley, and on the great western plains of Canada, it exceeds an average of one hundred feet over wide areas, and in places has five and six times that thickness. It was to this marginal belt that the ice sheets brought their loads, while northwards, nearer the centers of dispersion, erosion was excessive and deposition slight.

=Successive ice invasions and their drift sheets.= Recent studies of the drift prove that it does not consist of one indivisible formation, but includes a number of distinct drift sheets, each with its own peculiar features. The Pleistocene epoch consisted, therefore, of several glacial stages,--during each of which the ice advanced far southward,--together with the intervening interglacial stages when, under a milder climate, the ice melted back toward its sources or wholly disappeared.

The evidences of such interglacial stages, and the means by which the different drift sheets are told apart, are illustrated in Figure 361. Here the country from N to S is wholly covered by drift, but the drift from N to m is so unlike that from m to S that we may believe it the product of a distinct ice invasion and deposited during another and far later glacial stage. The former drift is very young, for its drainage is as yet immature, and there are many lakes and marshes upon its surface; the latter is far older, for its surface has been thoroughly dissected by its streams. The former is but slightly weathered, while the latter is so old that it is deeply reddened by oxidation and is leached of its soluble ingredients such as lime. The younger drift is bordered by a distinct terminal moraine, while the margin of the older drift is not thus marked. Moreover, the two drift sheets are somewhat unlike in composition, and the different proportion of pebbles of the various kinds of rocks which they contain shows that their respective glaciers followed different tracks and gathered their loads from different regions. Again, in places beneath the younger drift there is found the buried land surface of an older drift with old soils, forest grounds, and vegetable deposits, containing the remains of animals and plants, which tell of the climate of the interglacial stage in which they lived.

By such differences as these the following drift sheets have been made out in America, and similar subdivisions have been recognized in Europe.

5 The Wisconsin formation 4 The Iowan formation 3 The Illinoian formation 2 The Kansan formation 1 The pre-Kansan or Jerseyan formation

In New Jersey and Pennsylvania the edge of a deeply weathered and eroded drift sheet, the Jerseyan, extends beyond the limits of a much younger overlying drift. It may be the equivalent of a deep-buried basal drift sheet found in the Mississippi valley beneath the Kansan and parted from it by peat, old soil, and gravel beds.

The two succeeding stages mark the greatest snowfall of the Glacial epoch. In Kansan times the Keewatin ice field slowly grew southward until it reached fifteen hundred miles from its center of dispersion and extended from the Arctic Ocean to northeastern Kansas. In the Illinoian stage the Labrador ice field stretched from Hudson Straits nearly to the Ohio River in Illinois. In the Iowan and the Wisconsin, the closing stages of the Glacial epoch, the readvancing ice fields fell far short of their former limits in the Mississippi valley, but in the eastern states the Labrador ice field during Wisconsin times overrode for the most part all earlier deposits, and, covering New England, probably met the ocean in a continuous wall of ice which set its bergs afloat from Massachusetts to northern Labrador.

We select for detailed description the Kansan and the Wisconsin formations as representatives, the one of the older and the other of the younger drift sheets.

By the courtesy of E. E. Howell, Washington, D.C.]

=The Kansan formation.= The Kansan drift consists for the most part of a sheet of clayey till carrying smaller bowlders than the later drift. Few traces of drumlins, kames, or terminal moraines are found upon the Kansan drift, and where thick enough to mask the preexisting surface, it seems to have been spread originally in level plains of till.

The initial Kansan plain has been worn by running water until there are now left only isolated patches and the narrow strips and crests of the divides, which still rise to the ancient level. The valleys of the larger streams have been opened wide. Their well-developed tributaries have carved nearly the entire plain to valley slopes (Figs. 50 B, and 59). The lakes and marshes which once marked the infancy of the region have long since been effaced. The drift is also deeply weathered. The till, originally blue in color, has been yellowed by oxidation to a depth of ten and twenty feet and even more, and its surface is sometimes rusted to terra-cotta red. To a somewhat less depth it has been leached of its lime and other soluble ingredients. In the weathered zone its pebbles, especially where the till is loose in texture, are sometimes so rotted that granites may be crumbled with the fingers. The Kansan drift is therefore old.

=The Wisconsin formation.= The Wisconsin drift sheet is but little weathered and eroded, and therefore is extremely young. Oxidation has effected it but slightly, and lime and other soluble plant foods remain undissolved even at the grass roots. Its river systems are still in their infancy (Fig. 50, A). Swamps and peat bogs are abundant on its undrained surface, and to this drift sheet belong the lake lands of our northern states and of the Laurentian peneplain of Canada.

The lake basins of the Wisconsin drift are of several different classes. Many are shallow sags in the ground moraine. Still more numerous are the lakes set in hollows among the hills of the terminal moraines; such as the thousands of lakelets of eastern Massachusetts. Indeed, the terminal moraines of the Wisconsin drift may often be roughly traced on maps by means of belts of lakes and ponds. Some lakes are due to the blockade of ancient valleys by morainic débris, and this class includes many of the lakes of the Adirondacks, the mountain regions of New England, and the Laurentian area. Still other lakes rest in rock basins scooped out by glaciers. In many cases lakes are due to more than one cause, as where preglacial valleys have both been basined by the ice and blockaded by its moraines. The Finger lakes of New York, for example, occupy such glacial troughs.

Massive terminal moraines, which mark the farthest limits to which the Wisconsin ice advanced, have been traced from Cape Cod and the islands south of New England, across the Appalachians and the Mississippi valley, through the Dakotas, and far to the north over the plains of British America. Where the ice halted for a time in its general retreat, it left recessional moraines, as this variety of the terminal moraine is called. The moraines of the Wisconsin drift lie upon the country like great festoons, each series of concentric loops marking the utmost advance of broad lobes of the ice margin and the various pauses in their recession.

Behind the terminal moraines lie wide till plains, in places studded thickly with drumlins, or ridged with an occasional esker. Great outwash plains of sand and gravel lie in front of the moraine belts, and long valley trains of coarse gravels tell of the swift and powerful rivers of the time.

=The loess of the Mississippi valley.= A yellow earth, quite like the loess of China, is laid broadly as a surface deposit over the Mississippi valley from eastern Nebraska to Ohio outside the boundaries of the Iowan and the Wisconsin drift. Much of the loess was deposited in Iowan times. It is younger than the earlier drift sheets, for it overlies their weathered and eroded surfaces. It thickens to the Iowan drift border, but is not found upon that drift. It is older than the Wisconsin, for in many places it passes underneath the Wisconsin terminal moraines. In part the loess seems to have been washed from glacial waste and spread in sluggish glacial waters, and in part to have been distributed by the wind from plains of aggrading glacial streams.

=The effects of the ice invasions on rivers.= The repeated ice invasions of the Pleistocene profoundly disarranged the drainage systems of our northern states. In some regions the ancient valleys were completely filled with drift. On the withdrawal of the ice the streams were compelled to find their way, as best they could, over a fresh land surface, where we now find them flowing on the drift in young, narrow channels. But hundreds of feet below the ground the well driller and the prospector for coal and oil discover deep, wide, buried valleys cut in rock,--the channels of preglacial and interglacial streams. In places the ancient valleys were filled with drift to a depth of a hundred feet, and sometimes even to a depth of four hundred and five hundred feet. In such valleys, rivers now flow high above their ancient beds of rock on floors of valley drift. Many of the valleys of our present rivers are but patchworks of preglacial, interglacial, and postglacial courses (Fig. 366). Here the river winds along an ancient valley with gently sloping sides and a wide alluvial floor perhaps a mile or so in width, and there it enters a young, rock-walled gorge, whose rocky bed may be crossed by ledges over which the river plunges in waterfalls and rapids.

After Chamberlain and Leverett]

a and a´, ancient courses still occupied by the river; b, postglacial gorge; c, ancient course now filled with drift]

In such cases it is possible that the river was pushed to one side of its former valley by a lobe of ice, and compelled to cut a new channel in the adjacent uplands. A section of the valley may have been blockaded with morainic waste, and the lake formed behind the barrier may have found outlet over the country to one side of the ancient drift-filled valley. In some instances it would seem that during the waning of the ice sheets, glacial streams, while confined within walls of stagnant ice, cut down through the ice and incised their channels on the underlying country, in some cases being let down on old river courses, and in other cases excavating gorges in adjacent uplands.

=Pleistocene lakes.= Temporary lakes were formed wherever the ice front dammed the natural drainage of the region. Some, held in the minor valleys crossed by ice lobes, were small, and no doubt many were too short-lived to leave lasting records. Others, long held against the northward sloping country by the retreating ice edge, left in their beaches their clayey beds, and their outlet channels permanent evidences of their area and depth. Some of these glacial lakes are thus known to have been larger than any present lake.

Lake Agassiz, named in honor of the author of the theory of continental glaciation, is supposed to have been held by the united front of the Keewatin and the Labrador ice fields as they finally retreated down the valley of the Red River of the North and the drainage basin of Lake Winnipeg. From first to last Lake Agassiz covered a hundred and ten thousand square miles in Manitoba and the adjacent parts of Minnesota and North Dakota,--an area larger than all the Great Lakes combined. It discharged its waters across the divide which held it on the south, and thus excavated the valley of the Minnesota River. The lake bed--a plain of till--was spread smooth and level as a floor with lacustrine silts. Since Lake Agassiz vanished with the melting back of the ice beyond the outlet by the Nelson River into Hudson Bay, there has gathered on its floor a deep humus, rich in the nitrogenous elements so needful for the growth of plants, and it is to this soil that the region owes its well-known fertility.

=The Great Lakes.= The basins of the Great Lakes are broad preglacial river valleys, warped by movements of the crust still in progress, enlarged by the erosive action of lobes of the continental ice sheets, and blockaded by their drift. The complicated glacial and postglacial history of the lakes is recorded in old strand lines which have been traced at various heights about them, showing their areas and the levels at which their waters stood at different times.

With the retreat of the lobate Wisconsin ice sheet toward the north and east, the southern and western ends of the basins of the Great Lakes were uncovered first; and here, between the receding ice front and the slopes of land which faced it, lakes gathered which increased constantly in size.

The lake which thus came to occupy the western end of the Lake Superior basin discharged over the divide at Duluth down the St. Croix River, as an old outlet channel proves; that which held the southern end of the basin of Lake Michigan sent its overflow across the divide at Chicago via the Illinois River to the Mississippi; the lake which covered the lowlands about the western end of Lake Erie discharged its waters at Fort Wayne into the Wabash River.

The ice still blocked the Mohawk and St. Lawrence valleys on the east, while on the west it had retreated far to the north. The lakes become confluent in wide expanses of water, whose depths and margins, as shown by their old lake beaches, varied at different times with the position of the confining ice and with warpings of the land. These vast water bodies, which at one or more periods were greater than all the Great Lakes combined, discharged at various times across the divide at Chicago, near Syracuse, New York, down the Mohawk valley, and by a channel from Georgian Bay into the Ottawa River. Last of all the present outlet by the St. Lawrence was established.

The beaches of the glacial lakes just mentioned are now far from horizontal. That of the lake which occupied the Ontario basin has an elevation of three hundred and sixty-two feet above tide at the west and of six hundred and seventy-five feet at the northeast, proving here a differential movement of the land since glacial times amounting to more than three hundred feet. The beaches which mark the successive heights of these glacial lakes are not parallel; hence the warping began before the Glacial epoch closed. We have already seen that the canting of the region is still in progress.

=The Champlain subsidence.= As the Glacial epoch approached its end, and the Labrador ice field melted back for the last time to near its source, the land on which the ice had lain in eastern North America was so depressed that the sea now spread far and wide up the St. Lawrence valley. It joined with Lake Ontario, and extending down the Champlain and Hudson valleys, made an island of New England and the maritime provinces of Canada.

The proofs of this subsidence are found in old sea beaches and sea-laid clays resting on Wisconsin till. At Montreal such terraces are found six hundred and twenty feet above sea level, and along Lake Champlain--where the skeleton of a whale was once found among them--at from five hundred to four hundred feet. The heavy delta which the Mohawk River built at its mouth in this arm of the sea now stands something more than three hundred feet above sea level. The clays of the Champlain subsidence pass under water near the mouth of the Hudson, and in northern New Jersey they occur two hundred feet below tide. In these elevations we have measures of the warping of the region since glacial times.

=The western United States in glacial times.= The western United States was not covered during the Pleistocene by any general ice sheet, but all the high ranges were capped with permanent snow and nourished valley glaciers, often many times the size of the existing glaciers of the Alps. In almost every valley of the Sierras and the Rockies the records of these vanished ice streams may be found in cirques, glacial troughs, roches moutonnées, and morainic deposits.

It was during the Glacial epoch that Lakes Bonneville and Lahontan were established in the Great Basin, whose climate must then have been much more moist than now.

=The driftless area.= In the upper Mississippi valley there is an area of about ten thousand square miles in southwestern Wisconsin and the adjacent parts of Iowa and Minnesota, which escaped the ice invasions. The rocks are covered with residual clays, the product of long preglacial weathering. The region is an ancient peneplain, uplifted and dissected in late Tertiary times, with mature valleys whose gentle gradients are unbroken by waterfalls and rapids. Thus the driftless area is in strong contrast with the immature drift topography about it, where lakes and waterfalls are common. It is a bit of preglacial landscape, showing the condition of the entire region before the Glacial epoch.

The driftless area lay to one side of the main track of both the Keewatin and the Labrador ice fields, and at the north it was protected by the upland south of Lake Superior, which weakened and retarded the movement of the ice.

South of the driftless area the Mississippi valley was invaded at different times by ice sheets from the west,--the Kansan and the Iowan,--and again by the Illinoian ice sheet from the east. Again and again the Mississippi River was pushed to one side or the other of its path. The ancient channel which it held along the Illinoian ice front has been traced through southeastern Iowa for many miles.

a, country rock; b, Kansan till; c, loess; t, terrace of reddish sands and decayed pebbles above reach of present stream; s, stream; fp, flood plain of s. What is the age of rock-cut valley and of the alluvium which partially fills it, compared with that of the Kansan till? with that of the loess? Give the complete history recorded in the section.]

=Benefits of glaciation.= Like the driftless area, the preglacial surface over which the ice advanced seems to have been well dissected after the late Tertiary uplifts, and to have been carved in many places to steep valley slopes and rugged hills. The retreating ice sheets, which left smooth plains and gently rolling country over the wide belt where glacial deposition exceeded glacial erosion, have made travel and transportation easier than they otherwise would have been.

The preglacial subsoils were residual clays and sands, composed of the insoluble elements of the country rock of the locality, with some minglings of its soluble parts still undissolved. The glacial subsoils are made of rocks of many kinds, still undecayed and largely ground to powder. They thus contain an inexhaustible store of the mineral foods of plants, and in a form made easily ready for plant use.

On the preglacial hillsides the humus layer must have been comparatively thin, while the broad glacial plains have gathered deep black soils, rich in carbon and nitrogen taken from the atmosphere. To these soils and subsoils a large part of the wealth and prosperity of the glaciated regions of our country must be attributed.

The ice invasions have also added very largely to the water power of the country. The rivers which in preglacial times were flowing over graded courses for the most part, were pushed from their old valleys and set to flow on higher levels, where they have developed waterfalls and rapids. This power will probably be fully utilized long before the coal beds of the country are exhausted, and will become one of the chief sources of the national wealth.

=The Recent epoch.= The deposits laid since glacial times graduate into those now forming along the ocean shores, on lake beds, and in river valleys. Slow and comparatively slight changes, such as the warpings of the region of the Great Lakes, have brought about the geographical conditions of the present. The physical history of the Recent epoch needs here no special mention.

The Life of the Quaternary

During the entire Quaternary, invertebrates and plants suffered little change in species,--so slowly are these ancient and comparatively simple organisms modified. The Mammalia, on the other hand, have changed much since the beginning of Quaternary time: the various species of the present have been evolved, and some lines have become extinct. These highly organized vertebrates are evidently less stable than are lower types of animals, and respond more rapidly to changes in the environment.

=Pleistocene mammals.= In the Pleistocene the Mammalia reached their culmination both in size and in variety of forms, and were superior in both these respects to the mammals of to-day. In Pleistocene times in North America there were several species of bison,--one whose widespreading horns were ten feet from tip to tip,--a gigantic moose elk, a giant rodent (Castoroides) five feet long, several species of musk oxen, several species of horses,--more akin, however, to zebras than to the modern horse,--a huge lion, several saber-tooth tigers, immense edentates of several genera, and largest of all the mastodon and mammoth.

The largest of the edentates was the Megatherium, a. clumsy ground sloth bigger than a rhinoceros. The bones of the Megatherium are extraordinarily massive,--the thigh bone being thrice as thick as that of an elephant,--and the animal seems to have been well able to get its living by overthrowing trees and stripping off their leaves. The Glyptodon was a mailed edentate, eight feet long, resembling the little armadillo. These edentates survived from Tertiary times, and in the warmer stages of the Pleistocene ranged north as far as Ohio and Oregon.

The great proboscidians of the Glacial epoch were about the size of modern elephants, and somewhat smaller than their ancestral species in the Pliocene. The Mastodon ranged over all North America south of Hudson Bay, but had become extinct in the Old World at the end of the Tertiary. The elephants were represented by the Mammoth, which roamed in immense herds from our middle states to Alaska, and from Arctic Asia to the Mediterranean and Atlantic.

It is an oft-told story how about a century ago, near the Lena River in Siberia, there was found the body of a mammoth which had been safely preserved in ice for thousands of years, how the flesh was eaten by dogs and bears, and how the eyes and hoofs and portions of the hide were taken with the skeleton to St. Petersburg. Since then several other carcasses of the mammoth, similarly preserved in ice, have been found in the same region,--one as recently as 1901. We know from these remains that the animal was clothed in a coat of long, coarse hair, with thick brown fur beneath.

=The distribution of animals and plants.= The distribution of species in the Glacial epoch was far different from that of the present. In the glacial stages arctic species ranged south into what are now temperate latitudes. The walrus throve along the shores of Virginia and the musk ox grazed in Iowa and Kentucky. In Europe the reindeer and arctic fox reached the Pyrenees. During the Champlain depression arctic shells lived along the shore of the arm of the sea which covered the St. Lawrence valley. In interglacial times of milder climate the arctic fauna-flora retreated, and their places were taken by plants and animals from the south. Peccaries, now found in Texas, ranged into Michigan and New York, while great sloths from South America reached the middle states. Interglacial beds at Toronto, Canada, contain remains of forests of maple, elm, and papaw, with mollusks now living in the Mississippi basin.

What changes in the forests of your region would be brought about, and in what way, if the climate should very gradually grow colder? What changes if it should grow warmer?

On the Alps and the highest summits of the White Mountains of New England are found colonies of arctic species of plants and insects. How did they come to be thus separated from their home beyond the arctic circle by a thousand miles and more of temperate climate impossible to cross?

=Man.= Along with the remains of the characteristic animals of the time which are now extinct there have been found in deposits of the Glacial epoch in the Old World relics of Pleistocene Man, his bones, and articles of his manufacture. In Europe, where they have best been studied, human relics occur chiefly in peat bogs, in loess, in caverns where man made his home, and in high river terraces sometimes eighty and a hundred feet above the present flood plains of the streams.

In order to understand the development of early man, we should know that prehistoric peoples are ranked according to the materials of which their tools were made and the skill shown in their manufacture. There are thus four well-marked stages of human culture preceding the written annals of history:

4 The Iron stage. 3 The Bronze stage. 2 The Neolithic (recent stone) stage. 1 The Paleolithic (ancient stone) stage.

In the Neolithic stage the use of the metals had not yet been learned, but tools of stone were carefully shaped and polished. To this stage the North American Indian belonged at the time of the discovery of the continent. In the Paleolithic stage, stone implements were chipped to rude shapes and left unpolished. This, the lowest state of human culture, has been outgrown by nearly every savage tribe now on earth. A still earlier stage may once have existed, when man had not learned so much as to shape his weapons to his needs, but used chance pebbles and rock splinters in their natural forms; of such a stage, however, we have no evidence.

=Paleolithic man in Europe.= It was to the Paleolithic stage that the earliest men belonged whose relics are found in Europe. They had learned to knock off two-edged flakes from flint pebbles, and to work them into simple weapons. The great discovery had been made that fire could be kindled and made use of, as the charcoal and the stones discolored by heat of their ancient hearths attest. Caves and shelters beneath overhanging cliffs were their homes or camping places. Paleolithic man was a savage of the lowest type, who lived by hunting the wild beasts of the time.

Skeletons found in certain caves in Belgium and France represent perhaps the earliest race yet found in Europe. These short, broad-shouldered men, muscular, with bent knees and stooping gait, low-browed and small of brain, were of little intelligence and yet truly human.

The remains of Pleistocene man are naturally found either in caverns, where they escaped destruction by the ice sheets, or in deposits outside the glaciated area. In both cases it is extremely difficult, or quite impossible, to assign the remains to definite glacial or interglacial times. Their relative age is best told by the fauna with which they are associated. Thus the oldest relics of man are found with the animals of the late Tertiary or early Quaternary, such as a species of hippopotamus and an elephant more ancient than the mammoth. Later in age are the remains found along with the mammoth, cave bear and cave hyena, and other animals of glacial time which are now extinct; while more recent still are those associated with the reindeer, which in the last ice invasion roamed widely with the mammoth over central Europe.

=The caves of southern France.= These contain the fullest records of the race, much like the Eskimos in bodily frame, which lived in western Europe at the time of the mammoth and the reindeer. The floors of these caves are covered with a layer of bone fragments, the remains of many meals, and here are found also various articles of handicraft. In this way we know that the savages who made these caves their homes fished with harpoons of bone, and hunted with spears and darts tipped with flint and horn. The larger bones are split for the extraction of the marrow. Among such fragments no split human bones are found; this people, therefore, were not cannibals. Bone needles imply the art of sewing, and therefore the use of clothing, made no doubt of skins; while various ornaments, such as necklaces of shells, show how ancient is the love of personal adornment. Pottery was not yet invented. There is no sign of agriculture. No animals had yet been domesticated; not even man's earliest friend, the dog. Certain implements, perhaps used as the insignia of office, suggest a rude tribal organization and the beginnings of the state. The remains of funeral feasts in front of caverns used as tombs point to a religion and the belief in a life beyond the grave. In the caverns of southern France are found also the beginnings of the arts of painting and of sculpture. With surprising skill these Paleolithic men sketched on bits of ivory the mammoth with his long hair and huge curved tusks, frescoed their cavern walls with pictures of the bison and other animals, and carved reindeer on their dagger heads.

=Early man on other continents.= Paleolithic flints curiously like those of western Europe are found also in many regions of the Old World,--in India, Egypt, and Asia Minor,--beneath the earliest vestiges of the civilization of those ancient seats, and sometimes associated with the fauna of the Glacial epoch.

In Java there were found in 1891, in strata early Quaternary or late Pliocene in age, parts of a skeleton of lower grade, if not of greater antiquity, than any human remains now known. Pithecanthropus erectus, as the creature has been named, walked erect, as its thigh bone shows, but the skull and teeth indicate a close affinity with the ape.

In North America there have been reported many finds of human relics in valley trains, loess, old river gravels buried beneath lava flows, and other deposits of supposed glacial age; but in the opinion of some geologists sufficient proof of the existence of man in America in glacial times has not as yet been found.

These finds in North America have been discredited for various reasons. Some were not made by scientific men accustomed to the closest scrutiny of every detail. Some were reported after a number of years, when the circumstances might not be accurately remembered; while in a number of instances it seems possible that the relics might have been worked into glacial deposits by natural causes from the surface.

Man, we may believe, witnessed the great ice fields of Europe, if not of America, and perhaps appeared on earth under the genial climate of preglacial times. Nothing has yet been found of the line of man's supposed descent from the primates of the early Tertiary, with the possible exception of the Java remains just mentioned. The structures of man's body show that he is not descended from any of the existing genera of apes. And although he may not have been exempt from the law of evolution,--that method of creation which has made all life on earth akin,--yet his appearance was an event which in importance ranks with the advent of life upon the planet, and marks a new manifestation of creative energy upon a higher plane. There now appeared intelligence, reason, a moral nature, and a capacity for self-directed progress such as had never been before on earth.

=The Recent epoch.= The Glacial epoch ends with the melting of the ice sheets of North America and Europe, and the replacement of the Pleistocene mammalian fauna by present species. How gradually the one epoch shades into the other is seen in the fact that the glaciers which still linger in Norway and Alaska are the lineal descendants or the renewed appearances of the ice fields of glacial times.

Our science cannot foretell whether all traces of the Great Ice Age are to disappear, and the earth is to enjoy again the genial climate of the Tertiary, or whether the present is an interglacial epoch and the northern lands are comparatively soon again to be wrapped in ice.

=Neolithic man.= The wild Paleolithic men vanished from Europe with the wild beasts which they hunted, and their place was taken by tribes, perhaps from Asia, of a higher culture. The remains of Neolithic man are found, much as are those of the North American Indians, upon or near the surface, in burial mounds, in shell heaps (the refuse heaps of their settlements), in peat bogs, caves, recent flood-plain deposits, and in the beds of lakes near shore where they sometimes built their dwellings upon piles.

The successive stages in European culture are well displayed in the peat bogs of Denmark. The lowest layers contain the polished stone implements of Neolithic man, along with remains of the Scotch fir. Above are oak trunks with implements of bronze, while the higher layers hold iron weapons and the remains of a beech forest.

Neolithic man in Europe had learned to make pottery, to spin and weave linen, to hew timbers and build boats, and to grow wheat and barley. The dog, horse, ox, sheep, goat, and hog had been domesticated, and, as these species are not known to have existed before in Europe, it is a fair inference that they were brought by man from another continent of the Old World. Neolithic man knew nothing of the art of extracting the metals from their ores, nor had he a written language.

The Neolithic stage of culture passes by insensible gradations into that of the age of bronze, and thus into the Recent epoch.

In the Recent epoch the progress of man in language, in social organization, in the arts of life, in morals and religion, has left ample records which are for other sciences than ours to read; here, therefore, geology gives place to archæology and history.

Our brief study of the outlines of geology has given us, it is hoped, some great and lasting good. To conceive a past so different from the present has stimulated the imagination, and to follow the inferences by which the conclusions of our science have been reached has exercised one of the noblest faculties of the mind,--the reason. We have learned to look on nature in new ways: every landscape, every pebble now has a meaning and tells something of its origin and history, while plants and animals have a closer interest since we have traced the long lines of their descent. The narrow horizons of human life have been broken through, and we have caught glimpses of that immeasurable reach of time in which nebulae and suns and planets run their courses. Moreover, we have learned something of that orderly and world-embracing progress by which the once uninhabitable globe has come to be man's well-appointed home, and life appearing in the lowliest forms has steadily developed higher and still higher types. Seeing this process enter human history and lift our race continually to loftier levels, we find reason to believe that the onward, upward movement of the geological past is the manifestation of the same wise Power which makes for righteousness and good and that this unceasing purpose will still lead on to nobler ends.

INDEX

Aa, lava, 241 Acadian coal field, 354 Accretion hypothesis, 304 Acidic rocks, 249 Adelsberg grotto, 47 Adirondacks, 309, 316 Africa, 357 Agassiz, Lake, 67, 111, 435 Agates, 251 Alabama, 317, 360 Alaska, 85, 138, 140, 378 Aletsch glacier, 121 Algæ, 51, 52 Algonkian era, 306, 310 Allegheny Mountains, 90, 224, 326, 403 Alluvial cones, 98 Alluvium, 62 Alps, 118, 121, 141, 210, 211, 212, 223, 229, 349, 427, 443 Amazon River, 175 Ammonites, 294, 367, 380, 382 Amphibians, 364, 383 Amphicyon, 413 Amygdules, 250 Andes, 236, 279 Angle of repose, 25 Antarctic continent, 294 Antecedent streams, 209 Antelope, 413 Anthracite, 281 Anticlinal folds, 203, 209 Ants, 20 Apennine Mountains, 399 Appalachia, 317, 351, 358 Appalachian coal field, 356 Appalachian deformation, 358 Appalachian Mountains, 211, 214, 218, 292 Aquifer, 44 Aragonite, 296 Archæopteryx, 393 Archean era, 305 Arenaceous rocks, 9 Argillaceous rocks, 9 Arizona, 32, 76, 140, 151, 164, 220, 229, 249, 257, 371, 390 Arkansas, 337, 356, 373 Arkose, 186, 282, 370 Artesian wells, 44 Arthropods, 322 Artiodactyls, 411 Assiniboine, Mount, 34 Atlas Mountains, 399 Atmosphere, 304, 305 Atolls, 191, 193 Augite, 274 Austin, Tex., 71 Australia, 190, 357 Avalanches, 26

Bad Lands, 397, 398 Baltic Sea, 170, 171, 199 Barite, 287 Barrier Reefs, 191, 192 Basal conglomerate, 173, 184 Basalt, 249 Baselevel, 80, 83 Basic rocks, 249 Basin deposits, 103 Bay bars, 164 Beaches, 162, 164 Bears, 413 Bedding planes, 5 Belemnites, 382 Belt Mountains, 309 Bergschrund, 121, 135, 137 Bermudas, 148 Birds, 392 Bison, 413 Bitter Root Mountains, 272 Black Hills, 309, 371 Blastoids, 339 Blastosphere, 311 Block mountains, 222, 226 Blowholes, 159 Blue Ridge, 309, 316 Bomb, volcanic, 256 Bonneville, Lake, 107, 488 Bosses, 270 Bowlders, erratic, 420 of weathering, 28 Brachiopods, 328, 383, 343, 364, 380 Brazil, 18, 286 Breccia, 218, 255, 264 British Columbia, 373, 378 Bronze stage, 443, 448 Bryozoans, 333 Bunker Hill, 422

Calamites, 361, 367 Calcareous rocks, 9 Calciferous series, 327 Calcite, 290 Caldera, 239 California, 24, 99, 186, 152, 158, 169, 170, 197, 224, 256, 262, 287, 357, 360, 371, 400 Great Valley of, 101, 199, 372, 396 Cambrian period, 315 glaciation in, 358 life of, 319 Camels, 412 Canada, 28, 86, 67, 69, 90, 182, 198, 200, 218, 218, 267, 307, 309, 316, 336, 364, 367, 482, 487 Cape Breton Island, 198 Cape Cod, 162 Carbonated springs, 261 Carbonates, formation of, 12 Carboniferous period, 350 life of, 301 Carnivores, 418 Cascade Mountains, 00, 400 Cats, 418 Catskill Mountains, 342 Caucasus Mountains, 399 Caverns, 46, 241 Cenozoic era, 394 Centipedes, 388 Cephalopods, 324, 388, 389, 344, 367, 380 Ceratites, 380 Ceratosaurus, 385 Chain coral, 389, 843 Chalcopyrite, 287 Chalk, 9, 374, 375 Chalybeate springs, 62 Champlain subsidence, 487 Charleston earthquake, 288 Chazy series, 327 Chelan, Lake, 141 Chemung series, 341, 342 Chesapeake Bay, 169, 170, 197 Chicago, 146, 198, 486 Chile, 286 China, 28, 161 Christmas Island, 194, 248 Cincinnati anticline, 329, 366 Cirques, 136 Clinton series, 336 Coal, 362, 370, 375 Coal Measures, 351 Coast Range, 101, 372, 399 Coastal plain, Atlantic, 188 Coelenterates, 320 Coke, 271 Colorado, 18, 29, 88, 87, 158, 288, 266, 271, 334 Colorado plateaus, 357, 403 Colorado River, 80, 76, 140, 154, 228, 307, 318, 317 Columbia lavas, 400 Columnar structure, 268 Concretions, 49 Cones, alluvial, 98 volcanic, 267 Conglomerate, 9, 178 Congo River, 175 Conifers, 377 Connecticut, 370 valley, 408 Contemporaneous lava sheets, 248, 268 Continental delta, 176, 183 Continental shelf, 183 Continents, 188 Contours, 60 Copper, 287, 310 Coquina, 177 Coral reefs, 188 Corals, ancient, 321, 332, 338, 379 Cordaites, 363 Cordilleran ice field, 426 Corniferous series, 341 Coves, 161 Crabs, 379 Crandall volcano, 268, 400 Crater Lake, 259 Creodonts, 418 Cretaceous period, 372 Crinoids, 382, 303, 379 Crocodiles, 384 Cross bedding, 65, 182 Crustacea, 322, 382, 368, 379 Crustal movements, 195 Cumberland plateau, 90 Cup corals, 388 Cycads, 377, 378 Cycle of erosion, 84, 185, 292 Cystoids, 321, 382, 367

Dalmatia, 170 Darwin's theory of coral reefs, 191 Dead Sea, 221, 279 Death Gulch, 264 Deep-sea deposits, 187 Deer, 413 Deflation, 152 Deformation, 279 Delaware River, 197, 403 Deltas, 108, 111, 197 of Ganges, 109 of Indus, 110 of Mississippi, 109, 197 Denudation, 57 Denver, 398 Desert, 15, 55 Devitrification, 257 Devonian period, 316, 341 Dicotyls, 377, 404 Digitigrade, 406 Dikes, 244, 265 Dinosaurs, 385 Dinothere, 410 Diorite, 274 Dip, 202 Dip fault, 225 Diplodocus, 286 Dipnoans, 346 Discina, 324 Dismal Swamp, 106 Dogs, 413 Dragon flies, 364 Drift, 18, 113, 416 bowlders of, 420 englacial, 125 extent of, 425 pebbles of, 114, 420 stratified, 423 thickness of, 429 Driftless area, 438 Drowned valleys, 197 Drumlins, 421 Duluth, 436 Dunes, 147 Dust falls, 145

Earth, age of, 292, 298, 302 interior of, 276 Earthquakes, 224, 233 causes of, 233, 237 Charleston, 233 distribution of, 236 geological effects of, 234 India, 236 Japan, 237 New Madrid, 236 Earthworms, 20, 21 Echinoderms, 321, 332, 333, 343, 363 Edentates, 441 Egypt, 98 Electric Peak, 269 Elephants, 410 Elevation, effects of, 85 movements of, 197 Eocene epoch, 395 Epicontinental seas, 318 Erratics, 133, 420 Eskers, 424 Etna, 248, 402 Europe, Pleistocene ice sheet of, 427 Eurypterids, 333, 339, 363, 367 Evolution, 300, 447

Faceted pebbles, 113, 114, 420 Falls of the Ohio, 343 Fan folds, 205 Fault scarps, 219 Faults, 217 Faunas, 299 Feldspar, 9, 10, 42 Ferns, 361 Finger lakes, 432 Fire clay, 353 Fishes, 334, 339, 345, 364, 405 Fissure eruptions, 242 Fissure springs, 44 Fjords, 139, 142 Flint, 18, 375 Flood plains, 85, 93 Floods, 54 Floras, 299 Florida, 46, 163, 177, 178, 188, 396 Flow lines, 252 Fluorite, 287 Folded mountains, 210 Folds, 201, 208 Foliation, 283 Foraminifera, 187, 374: Forests, Carboniferous, 354, 361 Cretaceous, 377, 378 Devonian, 343 Tertiary, 404 Fort Wayne, 436 Fossils, 177, 296 Fractures, 215 Fragmental rocks, 8 France, 167, 171 cave men of, 445 Fringing reefs, 190 Frogs, 383 Frost, 15 Fundy, Bay of, 182

Gabbro, 274 Ganges, 58, 109, 197 Ganoids, 347 Garnet, 281 Gases, volcanic, 244 Gastropods, 324 Gastrula, 311 Geneva, Lake, 71 Geodes, 49 Geological time, divisions of, 295 Geology, definition of, 1, 3 departments of, 4 Georgia, 18, 373 Geysers, 52, 260 Glacial epoch, 142, 416 Glaciers, 113 abrasion by, 133 Alpine, 118 compared with rivers, 137, 142 crevasses of, 123 deposition by, 138 Greenland, 116 lower limit of, 129 melting of, 126 mode of formation, 118 moraines, 124 motion of, 120, 122, 134 piedmont, 131, 141 plucking by, 133 tables, 130 transportation by, 132 troughs, 137 wells, 129 young and mature, 129 Glauconite, 176 Globigerina ooze, 187 Glyptodon, 441 Gneiss, 283 Goats, 413 Gold, 287, 372 Goniatite, 344, 367 Graded slopes, 25 Granite, 9, 274 Graphite, 312 Graptolites, 320, 339 Gravitation, 22 Great Basin, 357, 360, 374, 376 Great Lakes, 198, 436 Great Plains, 82 Great Salt Lake, 107 Greenland, 115, 126, 378 Green Mountains, 309, 316, 420 Green sand, 176 Ground water, 39 Ground water surface, 40 Gryphæa, 379 Gymnosperms, 363, 377 Gypsum, 12, 335, 357, 371

Hade, 217 Hamilton series, 341 Hanging valley, 1389 Hanging wall, 217 Hartz Mountains, 214 Hawaiian volcanoes, 238, 248, 258, 279 Heat and cold, 13 Helderberg series, 341 Hematite, 310 Henry Mountains, 271, 376 High Plains, 100, 398 Hillers Mountain, 271 Himalaya Mountains, 122, 209, 210, 399 Historical geology, 4, 291 Honeycomb corals, 339 Hood, Mount, 260, 262 Hooks, 165 Hornblende, 274 Hornblende schist, 284 Hudson Bay, 90, 170 Hudson River, 197, 417 Hudson series, 327, 329 Humus acids, 10 Humus layer, 19 Huronian systems, 308 Hwang-ho River, 151 Hydrosphere, 22 Hydrozoa, 320

Icebergs, 116, 148 Iceland, 242, 258 Ichthyosaurus, 389 Idaho, 34, 400 Igneous rocks, 9, 249, 250, 251, 273 Illinoian formation, 429 Illinois, 54, 146, 356, 374 India, 28, 102, 147, 235, 357, 402 Indian Territory, 356 Indiana, 48, 104 Indo-Gangetic plain, 101 Indus River, 101, 110 Insects, 333, 364, 380 Interior of earth, 276 Internal geological agencies, 195 Intrusive masses, 270 Intrusive rocks, 273 Intrusive sheets, 268 Inverness earthquake, 236 Iowa, 29, 69, 73, 80, 86, 336, 356, 374, 431, 433, 439, 442 Iowan formation, 429 Iron ores, 13, 53, 279, 310 Islands, coral, 188 wave cut, 159, 161

Japan, 223, 224, 237 Joints, 5, 31, 216 Jordan valley, 279 Jura Mountains, 141, 212 Jurassic period, 369

Kame terraces, 424 Kames, 424 Kansan formation, 429 Kansas, 41, 50, 100, 336, 357, 373, 374, 429 Kaolin, 12 Karst, 47 Katahdin, Mount, 420 Keewatin ice field, 425 Kentucky, 45, 46, 343, 442 Keweenawan system, 308, 310 Kilauea, 239 Kings River Canyon, 403 Krakatoa, 245

Labrador, 198 Labrador ice field, 426 Laccolith, 271 Lagoon, 165, 167 Lahontan, Lake, 107, 438 Lake Chelan, 141 Lake dwellings, 448 Lake Geneva, 71 Lake Superior region, 284, 308, 310 Lakes, 70, 222, 432 basins, 97, 110, 127, 139, 141, 164, 165, 167, 191, 221, 222, 235, 259, 423, 432, 435 deposits, 104 glacial, 127, 139, 141, 423, 432, 435 Pleistocene, 435 salt, 106 Laminæ, 5 Landslides, 26, 234 Lapilli, 255 Laramie series, 375 Laurentian peneplain, 84, 308, 432 Lava, 238, 241 Lava domes, 243, 400 Lepidodendron, 362, 367 Lichens, 16 Lignite, 271 Limestone, 7, 177, 178, 190 Limonite, 13 Lingulella, 324 Lithosphere, 21 Lizards, 384 Llamas, 412 Loess, 150, 433 Long Island, 373 Louisiana, 336, 396 Lower Silurian period, 327 Luray Cavern, 48 Lycopods, 362

Magnetite, 279, 310 Maine, 169, 420 Malaspina glacier, 181 Maldive Archipelago, 198 Mammals, 393, 406, 440 Mammoth, 442 Mammoth Cave, 46 Mammoth Hot Springs, 52 Man, 414, 443 Mantle of waste, 17 Marble, 284, 329 Marengo Cavern, 48 Marl, 104 Marsupials, 393, 406 Martha's Vineyard, 161, 373, 395 Maryland, 56, 270 Massachusetts, 106, 162, 257, 309, 408, 417, 429 Mastodon, 410, 441, 442 Matterhorn, 34 Maturity of land forms, 80 Mauna Loa, 239 Meanders, 96 Medina series, 335, 403 Megatherium, 441 Mendota, Lake, 71 Mesa, 31, 32, 153 Mesozoic era, 369 Mesozoic peneplain, 376, 403 Metamorphism, 281 Mexico, 373, 375 Mica, 9 Mica schist, 284 Michigan, 104, 356, 443 Michigan, Lake, 149, 198 Mineral veins, 49, 286 Minnesota, 97, 426 Miocene series, 395 Mississippi, 337 Mississippi embayment, 373, 374, 395 Mississippi River, 56, 57, 82, 94, 96, 109 Mississippian series, 350 Missouri, 18, 236 Missouri River, 55, 97 Mobile Bay, 197 Mohawk valley, 436, 437 Molluscous shell deposits, 177 Mollusks, 324 Monadnock,83 Monkeys, 414 Monoclinal fold, 204 Monocotyls, 377, 404 Monotremes, 393, 406 Montana, 71, 309, 313, 373 Montreal, 268, 437 Monuments, 33 Moraines, 124 Mosasaurs, 390 Mountain sheep, 413 Mountains, age of, 229 life history of, 212, 215 origin of, 90, 210, 222 sculpture of, 33, 137 Movements of crust, 195 Muir glacier, 122, 129

Nantucket, 373 Naples, 201 Narragansett Bay, 197 Natural bridges, 46 Natural gas, 330 Natural levees, 93 Nautilus, 334 Nebraska, 50, 82, 100, 255, 356 Nebular hypothesis, 304 Neolithic man, 443, 448 Nevada, 104, 107, 222, 288, 289, 360, 400 Névé, 120 New Brunswick, 198 New England, 88, 373, 376, 378, 395, 403, 429, 432, 437 Newfoundland, 198 New Jersey, 148, 166, 168, 176, 196, 268, 269, 309, 310, 373, 437 New Madrid earthquake, 236 New Mexico, 31, 371, 399 New York, 60, 90, 309, 327, 329, 335, 336, 360, 421, 422, 423, 424, 432, 448 Niagara Falls, 60, 199 Niagara series, 335 Nile, 93, 109, 197 Normal fault, 217 North Carolina, 106 North Dakota, 67 North Sea, 170 Notochord, 347 Nova Scotia, 198 Nunatak, 116, 132

Ohio, 82, 198, 329, 335, 441 Ohio River, 55, 82 Oil, 330 Olenellus zone, 328 Olivine, 274 Oolitic limestone, 178 Ooze, deep-sea, 131 Ordovician period, 316, 327 life of, 331 Oregon, 222, 262, 400 Oreodon, 412 Ores, 287, 290 Organisms, work of, 16 Oriskany series, 341 Ornithostoma, 392 Orthoceras, 325, 367, 380 Oscillations, 196 a cause of, 273 effect on drainage, 85 Ostracoderms, 344 Ottawa River, 90 Outcrop, 2 Outliers, 31 Outwash plains, 425 Oxidation, 13 Oyster, 379, 380

Pahoehoe lava,241 Palæospondylus, 344 Paleolithic man, 444 Paleozoic era, 315 Palisades of Hudson, 268 Palms, 377 Pamir, 15 Peat, 94, 104 Peccaries, 412 Pelecypods, 324 Pelée, Mt., 246 Peneplain, 83 dissected, 86 Laurentian, 89, 308, 402 Mesozoic, 376, 403 Pennsylvania, 35, 211, 257, 357, 359, 403 Pennsylvanian series, 350, 351 Perissodactyl, 408 Perlitic structure, 252 Permian series, 350, 357, 360, 366 Petrifaction, 296 Petroleum, 330, 343 Phenacodus, 406 Phyllite, 283 Phyllopod, 323 Piedmont Belt, 87, 214, 309, 374 Piedmont plains, 99 Pikes Peak, 18 Pithecanthropus erectus, 446 Placers, 287 Plains of marine abrasion, 172 Planation, 81 Plantigrade, 406 Platte River, 82 Playa, 103 Playa lakes, 104 Pleistocene epoch, 416 Plesiosaurus, 389, 390 Pliocene epoch, 395 Plucking, 133 Po River, 58, 197 Pocono sandstone, 350, 404 Porosity of rocks, 40 Porphyritic structure, 252 Potholes, 59 Potomac River, 58, 66, 403 Predentata, 386 Pre-Kansan formation, 429 Primates, 414 Prince Edward Island, 198 Proboscidians, 410, 441, 442 Pteropods, 325 Pterosaurs, 391 Puget Sound, 396 Pumice, 250 Pyrite, 13

Quarry water, 15 Quartz, 6, 9 Quartz schist, 284 Quaternary period, 395, 416 Quebec, 28

Rain, erosion, 23 Rain prints, 181 Recent epoch, 416, 440, 447 Reconcentration of ores, 289 Record, the geological, 291 Red clay, 187 Red River of the North, 67 Red Sea, 221 Red snow, 115 Reefs, coral, 188 Regional intrusions, 272 Reptiles, 367, 383 Rhinoceros, 408 Rhizocarp, 343 Rhode Island, 356 Rhone glacier, 123 Rhyolite, 240 Richmond, Va., 370 Rift valleys, 221 Ripple marks, 180 Rivers, 54 bars, 65 braided channels, 94 deltas, 108 deposition, 62 discharge, 55 erosion, 59 estuaries, 85 flood plains, 93 floods, 54 graded, 74 gradients, 82 load of, 56 mature, 72, 80, 97, 98 meanders, 96 plains, 99 profile of, 73 revived, 85 run-off, 54 structure of deposits, 102 terraces, 96 transportation, 56, 64 waterfalls, 78 young, 67 Roches moutonnées, 134, 418 Rock bench, 156 Hock salt, 12, 357, 371 Rocky Mountains, 375, 399, 437 Ruminants, 412

Saber-tooth tiger, 413 Saguenay River, 90, 201 Sahara, 15, 146, 150 St. Elias Range, 399 St. Peter sandstone, 150 Salamanders, 383 Salina series, 335 Salt, common, 106, 335 Salt lakes, 106 San Francisco Bay, 197 Sand, beach, 163 of deserts, 149 reefs, 165, 167 storms, 145 Sandstone, 6, 7, 186 Sarcoui, 258 Sauropoda, 386 Schist, 283 Schladebach, 277 Scoria, 250, 255 Scorpions, 339, 340, 363 Scotland, 170, 220, 402 Sea, 155 erosion, 156 deposition, 174 transportation, 162 Sea arch, 159 Sea cave, 158 Sea cliff, 156, 157 Sea cucumber, 363 Seals, 414 Sea stacks, 169 Sea urchin, 332, 379 Seaweed, 176 Sedimentary rocks, 8, 9 Selkirk Mountains, 218 Septa, 338 Sequoia, 378 Shale, 8, 9 Sharks, 345, 405 Shasta, Mount, 262, 400 Sheep, 413 Shenandoah valley, 403 Shores of elevation, 167 Shores of depression, 169 Siderite, 63 Sierra Nevada Mountains, 24, 90, 99, 224, 229, 272, 287, 318, 357, 371, 372, 396, 398, 390, 402, 437 Sigillaria, 362, 367 Silica, 6, 178 Silurian period, 316, 334 life of, 338 Sink hole, 46 Slate, 207, 282 Slaty cleavage, 207 Slickensides, 217 Snake River lavas, 400, 401 Snakes, 384, 405 Soil, 19 Solfatara, 260 Solution, 11 Soufriére, 246 South America, 357 South Carolina, 233 South Dakota, 276, 374, 397 Spanish Peaks, 271, 376 Spherulites, 252 Spiders, 363 Spitzbergen, 378 Sponges, 320, 379 Springs, 41 thermal, 50 Stalactite, 48 Stalagmite, 48 Starfishes, 332 Staubbach, 140 Stegosaurus, 387 Stoss side, 134 Stratification, 5, 64, 180 Striæ, glacial, 114, 133, 418 Strike, 203 Strike fault, 225 Stromatopora, 331, 379 Stromboli, 244 Subsidence, 85, 183, 197 Sun cracks, 180 Superior, Lake, 257 Superposition, law of, 293 Susquehanna River, 403 Sutlej River, 209 Sweden, 199 Swine, 412 Switzerland, 28, 427 Syenite, 274 Synclinal fold, 204 Syracuse, N.Y., 436 Syringopora, 339

Tabulæ, 339 Taconic deformation, 329 Taconic Mountains, 376 Talc, 284 Talc schist, 284 Talus, 23 Tapir, 409 Teleost fishes, 349, 382, 405 Tennessee, 90, 373 Terminal moraines, 126, 422, 432 Terraces, 86, 96 Tertiary period, 395 Texas, 15, 69, 71, 166, 336, 356, 357, 371, 373, 374, 378 Theromorphs, 383 Throw, 217 Thrust faults, 217 Till, 418 Till plains, 420 Toronto, 443 Trachyte, 249, 258 Travertine, 52 Trenton series, 327 Triassic period, 369 Triceratops, 387 Trilobites, 322, 332, 339, 363, 367 Tuff, 255 Turkestan, 103 Turtles, 384

Unconformity, 227 Undertow, 174 Utah, 107, 271, 360, 371, 396, 399 Utica series, 327

V-Valleys, 74 Valley drift, 128 Valley trains, 425 Valleys, 66 Vermont, 309, 329, 420 Vernagt glacier, 129 Vertebrates, 334, 349 Vesuvius, 247, 259, 402 Virginia, 48, 84, 106, 370, 403, 442 Volcanic ashes, 244, 255 cones, 257 necks, 267 rocks, 249 Volcanoes, 238 causes of, 278 decadent, 260 submarine, 248 tertiary, 399

Walrus, 414 Warped valleys, 101 Warping, 198 Wasatch Mountains, 375 Washington, 18, 91, 150, 400 Waterfalls, 59, 78 Waves, 156 Weathering, 5 chemical, 10 differential, 29 mechanical, 13 Wells, 41 artesian, 44 West Virginia, 79, 357, 359 White Mountains, 443 Wind, 144 deposition, 147 erosion, 151 pebbles carved by, 152 transportation, 145 Wisconsin, 15, 18, 70, 71, 90, 94, 422, 426 Wisconsin formation, 429, 431 Wyoming, 50, 98, 371

Yahtse River, 131 Yellow Sea, 151, 170 Yellowstone canyon, 74 Yellowstone National Park, 50, 51, 52, 260, 261, 263, 269, 400 Yosemite, 403

Zeuglodon, 414 Zone of cementation, 49, 180 Zone of solution, 45 Zones of flow and of fracture, 207

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Transcriber's Notes

This transcription was derived from the 1905 publication obtained from The Internet Archive. As the Index of the original 1905 book is missing entries for U and V, the Index from the 1921 version was used to add the missing sections.

One error was noted in preparing this revision (page 493 under Hudson River should have been 417). Several hyphenated vs. unhyphenated forms were standardized to the most prevalent. Minor corrections were made where periods, commas, etc. were missing. A number of paragraphs which were split by images were rejoined. In some cases, the text was moved to the preceding or following page. As ALL CAPS was employed for the Chapter Titles in the original book, the small caps subchapter headings and Figure captions were not converted to all caps. The oe ligature in Coelenterates was converted to "oe".