Chapter II: The Topography of the Land (1)

Taking the better known portions of North America as a basis on which to classify the leading geographical features of the continent, it is convenient, and in the main sufficiently accurate, to recognise five primary physiographic provinces. These are, in their general order, from east to west:

1. Coastal plains and plateaus, of which the country between the Atlantic Ocean and the Appalachian Mountains furnishes the most typical examples.

2. A series of mountain ranges embracing all of the more elevated country on the east side of the continent from Georgia northward to the arctic archipelago, and in this book termed the _Atlantic Mountains_.

3. The great system of plains and plateaus extending from the Gulf of Mexico northward to the Arctic Ocean and bordered on the east by the Atlantic Mountains and on the west by a still greater series of mountains, which may be designated with sufficient accuracy as the _Continental Basin_.

4. A group of mountain chains and mountain ranges on the west side of the continent, including the Rocky Mountains, Sierra Nevada, Cascades, etc., and sometimes termed the Cordilleras. Under the scheme of classification here used, this highly complex belt of rugged country extending from south-central Mexico northward to the Arctic Ocean is termed the _Pacific Cordillera_, or, in less technical language, the _Pacific Mountains_.[1]

[1] The propriety of using the names here employed for the larger physiographic provinces of North America has been discussed by several writers in the _Bulletin of the Geographical Society of Philadelphia_, vol. ii, 1899, pp. 55-69.

Each of the four physiographic provinces briefly described above is in a conspicuous manner elongated in a north and south direction. The mountains, valleys, and plateaus, as well as the controlling lines of structure in the rocks below the surface, throughout the main body of the continent coincide in direction more or less nearly with the parallels of longitude. At the south, however, and crossing the trend of each of the provinces named above, is the:

Fifth, or Caribbean province, which includes the West Indies, the southern part of Mexico, and all of Central America. In this province are the _Antillean Mountains_, now mostly submerged, the principal axes of which trend east and west.

With this brief outline of the larger physical divisions of North America in mind, let us endeavour to become acquainted with the leading characteristics of each of the provinces as they exist to-day, and at the same time learn something of their long and varied histories.

COASTAL PLAINS AND PLATEAUS

_The Coastal Plains._--From New York to Key West and thence about the borders of the Gulf of Mexico to the neighbourhood of Vera Cruz, the border of the present land area of the continent is formed by a low plain, from 30 to 50 miles broad in New Jersey, but increasing in width southward to Georgia and Florida, where its somewhat indefinite inland margin is more than 100 miles from the sea, and reaching its greatest development in the delta of the Mississippi. Extending southward about the west coast of the Gulf, it forms the low, featureless eastern border of Texas, about 50 miles broad, and passes into Mexico, but gradually narrows as the Pacific Mountains approach the coast, and ends in the vicinity of Vera Cruz.

The Atlantic and Gulf coastal plain everywhere slopes gently seaward, and on its landward margin has an elevation in general of from 200 to 300 feet. The character of the material of which the coastal plain is composed, the fossils contained in it, as well as its geographical features, show that it is a continuation of the continental shelf, and was formed at a time when the border of the continent was more deeply submerged than at present. Minor oscillations of the earth's crust have time and again allowed the sea to extend inland, only to be forced to recede when the land again rose. Each invasion of the sea left a sheet of soft sediment over the portion of the land that was submerged. These oscillations are still in progress, as is indicated by the fact that along the New Jersey coast a downward movement at the rate of about 2 feet per century is taking place. A similar depression of the land is also thought to be in progress along the south Atlantic coast and in the delta of the Mississippi. The Atlantic coastal plain has its most characteristic development in South Carolina, and is roughly divisible according to its topography and soil into several belts parallel with the shore-line. At the same time it is transversely divided into strips by the several rivers which flow across it and by the many branches of these rivers originating on the plain itself.

The junction of the portion of the gently sloping border of the continent now above sea-level, with the submerged portion, is characterized by the presence of a belt of swamps, in part marine marshes where the salt water ebbs and flows, and in part fresh-water morasses in which the drainage is obstructed largely by decaying vegetation. Inland from the coastal swamps the surface becomes higher, is for the most part well drained, and when not too sandy furnishes rich agricultural lands. The Atlantic plain as a whole thus has three principal divisions: a submerged portion, a marsh portion, and a subaerial portion. During past ages the position of each of these belts migrated, owing to movements in the earth's crust, but their succession in reference to each other has been the same since the Tertiary period.

One of the most typical portions of the fringe of swamps now bordering the land is situated in eastern Virginia and North Carolina, and is known as the Dismal Swamp. In the central portion of this marshy region, embracing some 700 square miles, lies Lake Drummond, an example of a large number of small fresh-water lakes which are retained by rims composed of plant growths and decaying vegetable matter. The mound of vegetable _debris_ in the summit of which Lake Drummond is situated is from 20 to 30 miles broad and rises some 12 feet above tide-level. The lake is nearly circular, from 2 to 21/2 miles in diameter, and from 6 to 10 feet deep. The water is amber-coloured on account of the vegetable matter in solution, but is clear and without sediment in suspension, and is considered as remarkably wholesome. The lake was without definite outlet previous to the cutting of drainage-canals, and is entirely encircled by a dense forest, which has encroached on its border in such a manner as to render its boundaries indefinite. The wall of rank vegetation surrounding the open waters of the lake marks the beginning of the encircling swamp. Standing in the lake and supported by their widely expanded roots are several aged cypress-trees.

Along the coast of the Carolinas and Georgia sand-bars thrown up by the sea have formed many lagoons (Fig. 6), which are being filled by the wash of detritus from the land, by sand blown from their confining ridges, and by vegetation and the hard parts of molluscs, crustaceans, etc., living in their waters. In part, these areas have been converted into swamps, and are gradually being transformed into dry land. Farther southward, about the shores of Florida, and thence along the Gulf border, the low, indefinite margin of the coastal plain is fringed in many places by dense thickets of mangrove-trees, which extend their aerial roots into the salt water, and by retaining sediment and dead vegetation as well as by furnishing conditions favourable for animal life, lead to a gradual extension of the land.

The west border of the coastal plain from New York southward to central Georgia is at the junction of the soft, unconsolidated sands and clays of the emerged portion of the continental shelf, with hard and usually crystalline rocks of great geological age forming, an upland known as the Piedmont plateau, which extends westward to the base of the Appalachian Mountains. The sharply defined boundary between the plain and the plateau is termed the _fall line_, for the reason that it is marked by the lowest falls and rapids in the streams flowing eastward from the Appalachian Mountains. Throughout the courses of these streams to the west of the fall line they are shallow and swift and broken by many picturesque rapids, while to the east of the fall line they broaden in the soft sediments of the coastal plain, and are deep, placid streams which widen into estuaries. The influence of the tides is felt in these drowned rivers to the fall line. The most important fact in this connection is that the lower courses of the larger rivers, such as the Delaware, Susquehanna, Potomac, James, etc., are navigable for ocean-going vessels, while their upper courses to the west of the fall line are difficult to traverse even in canoes.

The fall line is thus the head of navigation in a number of rivers, and for this reason it has determined the sites of several important cities. Its course is marked by Trenton, Philadelphia, Baltimore, Washington, Richmond, Weldon, Raleigh, Augusta, and Macon. Farther south, about the landward margin of the portion of the coastal plain bordering the Gulf of Mexico, the fall line is less distinct, largely for the reason that the rocks bordering it on the north and west are less resistant than those forming the plateau at the east base of the Appalachians.

Exceptions to the fact that the coastal plain is composed mostly of soft sediments occur in southern Florida and in Yucatan, where coral rock has been upraised. Southeastward from Yucatan a coastal plain is wanting and rocky bluffs separated by stream-cut valleys come boldly down to the surf line. Partially drowned valleys on each side of Central America bear record of a recent but moderate downward movement of the land.

From New York northward along the border of the continent the coastal plain is mostly lacking, or if recognisable, is greatly modified by glacial deposits, and the Piedmont plateau, as it is known farther south, swings eastward and becomes a coastal plateau with a more or less roughened surface, which extends northward to Labrador and the Arctic Ocean.

The geologically recent oscillations of the continent, as stated in the preceding chapter, have been greatest in high latitudes, where the last movement, as there are reasons for believing, was upward and is still continuing. This rise, although it has not fully counteracted the changes produced by a preceding downward movement, has caused the shore-line to recede and a great area on the arctic border of the continent which was previously submerged has thus become exposed. The coastal plain on the west side of Hudson Bay, as described by T. B. Tyrrell, is about 50 miles wide in the vicinity of Fort Churchill, latitude 55 deg., and broadens rapidly northward of that locality. In latitude 64 deg. the boundary between these new lands and the older plains of the interior is about 300 miles from the present shore; thence northwestward it has not been traced, but may be expected to cross the Mackenzie some 250 miles from its mouth and pass westward into Alaska.

This arctic coastal plain is known in part as the Barren Grounds, but in general may be designated as a _tundra_, as over extensive areas it is similar to the still greater tundras of Siberia. This tundra forms the extreme northern and northwestern border of the continent in arctic Canada and northern and northwestern Alaska, and although but imperfectly explored, has a length of probably 2,000 miles and a width of from 50 to 60, and in places of over 100 miles. On the west coast of Hudson Bay the tundra region slopes gradually from 500 to 600 feet above the sea down to the present coast, and is traversed by sand and gravel terraces and beaches or ridges which mark the former positions of the sea margin. The lower ridges referred to are thickly strewn with shells of molluscs belonging to species still living in the adjacent ocean waters, thus indicating the recency of the emergence of the land. This arctic coastal plain has the same general geographical features as the coast plain on the southern Atlantic and Gulf border of the continent; but, owing mainly to different climatic conditions, differs from its southern representative in nearly every detail.

The tundra may be briefly defined as a vast frozen morass. The dense mat-like vegetation consists principally of mosses and lichens (but not noticeably of _Sphagnum_ or peat-moss, as is sometimes stated), and during the short and not infrequently hot summers is beautified by a multitude of low flowering herbaceous plants. Trees are absent, except along the inland border, where the tundra merges with the subarctic forest. To the north, or seaward from the isolated groves of stunted spruce-trees marking the "continental timber-line," the only representative of arboreal vegetation is usually the slim osier-like arctic willow which grows in sheltered localities and attains a height of 3 to 5 feet. Near the streams there are in some localities broad areas covered with dark-green meadow-like growths of rushes (_Equiseta_). The luxuriant flowering plants spring into existence as if by magic as soon as the winter's snow melts, and under the warmth and light of the nightless arctic summer grow with wonderful rapidity. In winter the tundra is snow-covered, but the snow is less deep than in more humid regions, and the cold is intense. The bog becomes deeply frozen, and is not completely thawed during the succeeding summer. Even in midsummer, when the surface is a luxuriant garden of flowers and fresh gray-green moss, ice exists a foot or two beneath the luxuriant carpet and extends to a great but unknown depth. Excavations made in Alaska have shown that the perennial, dirt-stained ice beneath the tundra is at least 25 feet thick, but this is by no means its maximum depth. On the shore of Eschscholtz Bay and along the Kowak River sections of the tundra exposed in cliffs indicate a thickness of 150 to 300 feet of ice, covered by a thin layer of black peaty soil. The similar region in Siberia, as shown by borings, is known to be permanently frozen to a depth of 380 feet deep. The subsoil ice is sheltered by the vegetation and the peaty soil resting on it, from the heat of the short summers, and the part softened by the summer's sun is refrozen during the long intensely cold winters. It is probable that under the present climatic conditions a sheet of perennial ice would be formed beneath the tundra, but the suggestion that the ice now present is in part an inheritance from a former period of greater cold is not without support. The vegetation of the tundra grows each year at the surface, while the partially decayed material below is frozen and preserved. This increase in depth of the vegetable matter is much the same as the growth of peat in temperate latitudes, except that the partially decayed material is preserved in cold storage. It was in the tundra of Siberia that the completely preserved bodies of the mammoth and the woolly rhinoceros have been discovered. Similar finds are to be looked for in the tundra of North America, where the bones of these animals have already been found.

On the Pacific border of the continent the shores are mostly bold, and coastal plains comparable with those on its eastern and northern margins are absent. In southern California, however, in the vicinity of Los Angeles, a modern and apparently local elevation of the land has produced a highly fertile plain, now, owing to the magic touch of irrigation, beautified by gardens and orchards.

_The Piedmont and Coastal Plateaus._--Adjacent to the western margin of the Atlantic coastal plain, and extending from Alabama northward to New England, there is a plateau region about 150 miles broad in its central part, but narrowing towards its extremities so as to be from 40 to 60 miles broad in Maryland and New Jersey, and of about the same width at the south, in Georgia. The slope of the plateau surface is seaward from an elevation of about 1,000 feet along its western margin to 250 or 300 feet at the fall line where it joins the coastal plain.

From its position at the foot of the Appalachian Mountains this moderately elevated plain is termed the Piedmont plateau. The same plateau extends northeastward, however, where it is known as the New England plateau, and is without any definite boundary to separate it from the similar region in the maritime provinces of Canada. While local divisions of this great extent of moderately elevated plateau country are recognised, yet in a general view of the continent it is evident that the Piedmont plateau, the New England plateau, and the similar region, mostly of crystalline and igneous rocks, extending from Maine to Hudson Strait and beyond, in reality forms a single great geographical unit in which the geological structure and geographical features are much the same. The general history of this great Atlantic plateau, as it may, perhaps, be termed, shows that it consists mainly of metamorphic rocks, such as mica schist, gneiss, slates, etc., together with granite and other igneous rocks, and, to a minor extent, of sandstones, shales, and limestones, mostly of Jura-Trias and Carboniferous age. These rocks were upraised probably in part into lofty mountains, and then worn down by erosion nearly to sea-level, thus forming what is termed a _peneplain_, or a plain of subaerial denudation. It is not intended by this statement to imply that all of the Atlantic plateau was ever a single great peneplain, but the same general history seems to apply to the entire region. The upheaval of the plains produced by erosion gave the streams greater energy, and they have begun the task of again reducing the land to sea-level, but have not as yet broadened their valleys so as to greatly modify the general plateau character of the region they traverse. The softer or more easily soluble rocks have been eroded away, leaving broad valleys, as in the several instances where sandstones and shales of what is known as the Newark system (Jura-Trias) occur in detached areas from South Carolina to Nova Scotia. Then, too, from northern New Jersey northward to Labrador and beyond, great glaciers have crossed the plateau or developed upon its broad north portion and have ground down its surface or left widely extended hills and ridges of morainal material upon it.

Where the process, just referred to, of planing down a tract of country nearly to sea-level is incomplete and remnants of former uplands still remain as isolated hills or groups of hills, such inheritances from the pre-peneplain stage may still exist when the region is elevated into a plateau and give diversity to its surface. An example of such a residual hill is furnished by Mount Monadnock, in southern New Hampshire, and, as proposed by W. M. Davis, the name of this old landmark is adopted as a technical term by which to designate all similar remnants of old uplands left standing on a peneplain. On the Atlantic plateau there are many _monadnocks_. They range in size from well-characterized hills to mountain-like forms, and may be isolated or occur in groups. When a monadnock stands alone its history may be easily read, but groups of such eminences, especially when of large size, become ranges of hills or even mountains, and may preserve so much of their former characteristics that they outrank the adjacent peneplain and become the dominant geographic feature of the region to which they give diversity. Such a passage from monadnocks to mountains seems to be furnished by the numerous isolated hills on the Atlantic plateau and the mountains of New England and of eastern Canada.

The most characteristic portions of what has just been termed provisionally the Atlantic plateau are the Piedmont plateau, which skirts the east base of the Appalachian Mountains from New York to central Alabama and the Labrador plateau. The eastern border of the Piedmont plateau is determined by the fall line described above, where the hard crystalline rocks of the Piedmont region meet the softer rocks of the Atlantic coastal plain. The rivers flowing eastward from the Appalachian, such as the Delaware, Susquehanna, Potomac, and the James, cross the Piedmont plateau in well-defined but narrow channels, usually from 100 to 200 feet deep, leaving the interstream spaces with generally level surfaces, although etched as it were by the lateral tributaries of the master streams. These rivers are shallow and rapid in their courses across the plateau, or in somewhat technical geographical language are not as yet graded, but on crossing the fall line become sluggish tide-water streams which widen into estuaries, as already described. Owing to the warm humid climate of this region, the rocks in the interstream spaces are usually deeply decayed and furnish clay soils which have characteristic red and yellow colours. Much of the cotton and tobacco of the South Atlantic States is grown on these residual soils which were left as the more soluble portions of the rocks were removed in solution.

Labrador, although in great part unexplored, is known to present the characteristic features of an irregular plateau, with a general elevation of 1,500 to 2,000 feet above the sea. The surface is undulating and has hills and hollows, the latter frequently holding lakes and swamps, but the inequalities seldom exceed 500 feet in vertical range. Although the western boundary of the Labrador plateau is indefinite, its area may be taken at about 500,000 square miles. In its western part, and apparently rising from the plateau as a group of residual hills left by erosion, are the so-called Laurentian or Laurentide Mountains. The eastern border of the plateau forms the bold and excessively rugged Atlantic coast-line of Labrador, characterized by steep cliff with a fringe of small rocky islands. The adjacent sea is deep and the continental shelf narrow. On the south the plateau is bordered by a series of terraces which lead down to the St. Lawrence River and on the west it merges indefinitely with the plains of the continental basin.

The rocks of Labrador are largely metamorphic, but include ancient igneous intrusions, and are hard and resistant. The present surface is the result of deep erosion which has removed a great but unknown thickness of material and left exposed what was once the deeply buried basal portion of a mountainous region. This is a part of the oldest known land of the continent, and, so far as can be learned, has never been covered by the sea since a very ancient geological period. In addition to the long eras of erosion, during which the _debris_ removed was deposited in part farther south, and contributed to the formation of the stratified rocks of the Appalachian region and interior continental basin, there was a comparatively recent extension of great glaciers over the plateau which removed the previously disintegrated and decayed rocks and left the present bare, rounded, and generally subdued hills with intervening basins. The soils are thin, for the reason that under the present climatic conditions rock decay is retarded, and are confined principally to the depression where peaty material has accumulated. Owing to the lack of soil on the uplands, the excess of water in the hollows, and to the severity of the climate, the forest is not continuous, the trees are small, and the vegetation generally of a subarctic character. This vast region is without agricultural possibilities, and thus far has been of value to man almost solely on account of its fur-bearing animals and the fisheries of its coast.

The northern border of the Atlantic plateau cannot at present be accurately defined. Seemingly it should include the Arctic archipelago, which provisionally may be considered as a deeply dissected plateau region, at present less elevated than formerly, thus allowing the sea to enter the valleys and to transform old uplands into islands. The bold and highly instructive explorations conducted in recent years by Robert Bell, for the Canadian Geological Survey, have shown that in the region adjacent to Hudson Strait the plateau features characteristic of the greater part of the Labrador peninsula are absent and mountains occur which rank as the highest on the eastern border of the continent.

On the Pacific coast plateaus corresponding closely with those adjacent to or bordering the Atlantic are wanting. What geographers recognise as deeply dissected plateaus, so extremely rough that they pass for mountain ranges, do occur on the western border of the continent, however, and will be described later.

THE ATLANTIC MOUNTAINS

This title will no doubt appear novel to many persons, and is, perhaps, open to adverse criticism, but it serves to unite in one group all of the mountains in the eastern half of North America. A cordillera, as usually defined, consists of two or more mountain chains associated geographically, but not necessarily of the same age. On the Atlantic border of the continent we have an example of such a family of mountains. The Atlantic mountains, although comprising ranges, systems, etc., of widely different ages, are all geologically old, and have resulted from upheavals along two generally parallel and slightly overlapping northeast and southwest belts adjacent to the Atlantic Ocean. The growth of this group of mountains is believed to have been from the north southward, and several periods of upheaval have been recognised.

The two main divisions or chains referred to are separated by the valley of the St. Lawrence. The mountains at the north are known as the Laurentides or Laurentian Highlands, and those at the south comprise the mountains of New Brunswick and Maine, the White Mountains of New Hampshire, the Green Mountains of Vermont, the Adirondack Mountains of northeastern New York, and the Appalachians. The most convenient method of reviewing the characteristics and histories of these several uplifts is to begin with the Appalachians, which are at the same time the most important and best known, and consider them in their order from south to north.

_The Appalachian Mountains._--This beautiful and frequently exceedingly picturesque series of long, narrow ridges separated one from another by trough-like valleys, constitutes a mountain system some 900 miles long and 50 to 130 or more miles wide (Fig. 15). The truly mountainous portion in its widest part, in western North Carolina and eastern Tennessee, is about 70 miles across, but a portion of the adjacent plateau on the west partakes of the same structural features and is a part of the Appalachian uplift. The system is considered as extending from the Hudson southward to central Alabama and central Georgia. At the north its terminus is indefinite, as it merges with the highlands to the east of the Hudson and with the Berkshire Hills of Massachusetts, which in turn are not strictly separable from the Green Mountains of Vermont. At the south, the system ends somewhat abruptly where the crystalline rocks comprising its southern terminus pass beneath the soft sediments of the coastal plain. The eastern border of the system is well defined by its junction with the Piedmont plateau, but on the west it merges through a series of lessening folds with the plateaus and plains of the eastern border of the interior continental basin. The Alleghany plateau, which skirts the western border of what is usually recognised as the Appalachian Mountains, but which is really its moderately disturbed border, extends from the Hudson to Alabama, and in its various portions is known by distinct names. Its northern extension overlooking the Hudson forms the Catskill Mountains; farther south it becomes locally the Alleghany plateau, and still farther south the Cumberland plateau. Separating the bold eastern escarpment of this series of plateaus from the generally higher mountains to the eastward lies the great Appalachian Valley, which under various names extends from the Hudson to central Alabama. This important and highly fruitful valley is underlaid to a great extent by thick bedded limestones and soft shales, and owes its existence to erosion and largely to the removal of limestone in solution.

The Appalachians are nowhere lofty, and only approach the characteristics of great mountains in their southern portion. The culminating summit is Mount Mitchell, in western North Carolina, which has an elevation of 6,711 feet. Roan Mountain, 27 miles to the northward of Mount Mitchell, rises 6,287 feet above the sea. In the neighbouring Unaka and Great Smoky Mountains, to the southwest and west of Mount Mitchell, there are many boldly rounded domes ranging in height from 5,000 to over 6,000 feet Northward of the highly picturesque southern Appalachians, the system decreases in height and is really a deeply dissected plateau, as will be shown later, in which the long, even-crested ridges have a general elevation of 4,000 feet in Virginia and about 2,000 feet in Pennsylvania and New Jersey. At its northern extension in New York it decreases still more in height, and is surpassed in elevation by the plateau on the west, there represented by the Catskill Mountains, the highest portion of which is 3,660 feet above the sea.

The characteristic structural feature of the Appalachians is the presence of a great series of up and down folds, or anticlinals and synclinals as geologists term them, which run in a nearly parallel northeast and southwest direction, but in Pennsylvania especially exhibit many broad curves in their general course. These folds are similar to the waves that may be produced in a heavy rug or carpet by pressing against one of its margins. The rocks have been thrown into a series of great wrinkles which are not continuous throughout the length of the system, but as one dies out another takes its place. The folds overlap at the ends or are arranged _en echelon_. The longer axes of the folds are seldom horizontal, but have usually a gentle pitch; for this reason one end of a fold frequently passes beneath the surface, while the other end is exposed to erosion. Another characteristic is that the anticlinals, as a rule, are steep on their western margins, and slope more gently on their eastern flanks, or are unsymmetrical. The overturning of the folds where most pronounced has led to the breaking of the rocks on the west side of an upward wrinkle where the descending limb of an anticlinal is sharply bent in order to pass into the ascending limb of the adjacent synclinal. These breaks or faults in certain instances form thrust planes along which one portion of a series of beds has been carried westward, sometimes for several miles, over another portion of the same series. This highly characteristic system of unsymmetrical folds, passing at times, and especially in Tennessee and Alabama, into great thrust planes, is accounted for on the general theory that there has been lateral pressure or a tangential thrust, which has forced the strata into a series of elongated arches, in much the same manner as in the case of a rug, as above suggested, one margin of which has been forced by lateral pressure towards its central part.

The rocks composing the greater portion of the Appalachians are stratified marine sediment such as sandstone, shale, limestone, etc., which were laid down one on another until a great depth was attained, corresponding, as we may fancy, to a pile of rugs, the original thickness in Pennsylvania being about 40,000 feet. Lateral pressure resulting, as it is believed, from the cooling and consequent contraction of the earth's highly heated interior, and the movement of the cool and rigid crust in order to keep in contact with the shrinking mass beneath, has led to the folding and occasional breaking of the rocks, which at the same time were elevated above the sea. A crushing together or folding of the rocks similar to that which has taken place along the central part of the Atlantic border of North America, as is well known, has occurred also in many other regions, and the Appalachians may be taken as the type of a class of mountains, sometimes termed corrugated mountains, which includes the Alps and Pyrenees, the Coast Range of California, etc. For convenience we may speak of such mountains as being of the Appalachian type.

Had the folding in the Appalachian region gone on without erosion, the surface would to-day be a series of great, elongated arches or upward folds, rising in many instances 5,000 or more feet above the intervening valleys, and where breaks or faults occur their upraised borders would stand as mighty cliffs, in some localities a mile or more high. The central part of the region with this strange topography had there been no erosion would, perhaps, be fully as prominent as the Himalayan Mountains are at present. No sooner, however, were the Appalachian Mountains upraised above the sea than the destructive agencies of the atmosphere began their attacks upon them. The rocks were shattered by changes of temperature, and at times at least crumbled by the freezing of absorbed water and also underwent chemical changes which softened and disintegrated them. The rains beat upon them, and streams flowing to the sea cut channels and carried away the material forming the land. These processes of disintegration and erosion have been in progress since islands and continents first appeared on the earth, and every mountain range now giving diversity to the surface of the land represents the net result of elevation over denudation. The Appalachians are not an exception, but a typical illustration of this general law. The great folds of which they are composed have been truncated by erosion and the surfaces thus produced, etched, as it were, by the action of the air, rain, and by streams, so as to leave the edges of the more resistant layers in relief.

One conspicuous result in this general process of erosion is due to the fact that the folded strata consist in many instances of alternating hard, or insoluble and soft, or readily soluble layers. Where resistant layers underlaid by soft, or readily soluble strata formed the summits of arches they have in many instances been broken in the process of folding or cut through by streams flowing down their flanks and the weak beds beneath exposed. After this stage was reached the erosion of the upward folds went on more rapidly than the removal of rock from the compressed downward folds, so that what is structurally a ridge became a valley: while the bordering troughs or synclinals floored with hard layers were left in relief as ridges or table-lands. The anticlinal ridges have thus been transformed into topographic valleys and the original synclinal troughs left in relief as plateaus and ridges.

This reversion of what would have been ridges and troughs had there been no erosion, is illustrated by the following cross-section through Lookout Mountain in Alabama, which is an example of what is known as a synclinal mountain. Many such synclinal mountains or plateaus, separated by narrower anticlinal valleys, occur throughout the Appalachians.

The characteristics in the present topography of the Appalachians just considered are but a minor portion of the great changes that have resulted from erosion. The history of the system has not been the same in this connection throughout, but retains evidences of successive upward movements with long periods of erosion intervening which have produced certain striking differences in its northern and southern portions. These differences are so well marked that it is convenient to divide the system into two portions, termed the northern Appalachians and southern Appalachians. The most conspicuous difference between the two is shown by the direction of flow of the larger rivers. At the north, the principal rivers--the Delaware, Susquehanna, Potomac, and James--rise well to the west of the mountains and flow southeast athwart the numerous folds, and after crossing the Piedmont plateau and coastal plain discharge into the Atlantic. At the south, however, the rivers, particularly New River and the Tennessee, rise on the eastern border of the Appalachians and flow westward, cutting through the Alleghany plateau, and are tributary to the Mississippi and the Gulf of Mexico. The somewhat arbitrary dividing line between these two provinces follows the divide to the north of New River, or in a general way, as has been stated by C. W. Hayes, is marked by a line drawn from the most easterly point of Kentucky southeastward to Cape Fear, on the Atlantic coast.

The fact that several large rivers rising to the northwest of the northern Appalachians flow directly across or through the numerous ridges composing the system in deep, narrow valleys, and the similar behaviour of the streams rising on the eastern border of the southern Appalachians, but flowing westward, are among the most interesting features of the entire region. Why is it that the mountains have not formed a divide or water-parting so as to force all of the streams having their sources on its west side to take what would seem the easier course, and to flow to the Gulf of Mexico, and cause the waters falling on its eastern slopes to flow to the Atlantic? The answer to this apparently puzzling question has been furnished by Davis, Willis, Hayes, Campbell, and others, who have shown that the mountains were not raised all at once, but experienced upward movements at widely separated intervals, with intervening periods of rest during which the elevations previously produced were more or less completely planed away by erosion. During one of these intervals the north Appalachians more especially were worn down to approximately sea-level and a gently sloping plain produced across which the larger rivers flowed to the Atlantic. This peneplain was later upraised into a plateau and its downward inclination towards the east increased. The streams were thus given greater energy and began again to deepen their channels. They held their right of way acquired on the featureless erosion plain and cut deep trenches through the edges of the hard layers which crossed their courses. At the same time lateral branches were developed which followed the outcrops of the less resistant beds and eroded them away so as to leave the hard beds in bold relief. As the edges of the more resistant beds became more and more prominent the eastward-flowing streams cut deeper and deeper into them. The even summits of the ridges, one of the most striking features in the beautiful scenery of the Appalachians, still mark the position of the elevated erosion plain.

In the southern Appalachian the old erosion plain formed nearly at sea-level was tilted gently westward, and the streams flowing over its surface given initial courses in that direction, which were maintained as they deepened their channels, and on account of increased energy originating from the upraising of the region drained by them, developed lateral branches, as is the case of the more northern streams just referred to, and the process of carving away the land to sea-level was again renewed.

Portions of the original upland or mountain mass left unconsumed during the long period of planation, which reduced most of the region nearly to sea-level, still remain in eastern Tennessee, western North Carolina, and northern Georgia, and form the highest and most picturesque portion of the Appalachians.

After the upraised peneplain from which the long, even-crested ridges of the Appalachians were produced by the excavation of the bordering valleys had been deeply dissected and the valleys broadened, another upward movement took place and the streams again deepened their valleys. This is the stage in which we now find the mountains. The crests of the ridges, characteristically displayed in eastern Pennsylvania, are portions of the first peneplain of which a definite record is preserved, while the broad valleys with sharply cut channels in their bottoms represent the much less complete second stage of planation.

The two ancient peneplains referred to above, the histories of which are recorded in the topography, have received definite names in order that they may be readily designated. The older and higher one is termed the Schooley peneplain[2] on account of the preservation of a typical portion at Schooley Mountain in New Jersey, while the lower one, represented by the broad valley through which flows the Shenandoah River, Virginia, is known as the Shenandoah peneplain. A generalized profile in a northwest and southeast direction through a portion of the Appalachians is shown in the following diagram, which will serve to make more definite the description just given. The highest summits in the diagram represent portions of the Schooley peneplain; if the depressions could be refilled the surface of the great plateau formed by the elevation of this plain would be restored. The bottoms of the broad depressions represent the Shenandoah peneplain, which is sharply trenched by the modern river channels.

[2] Also known as the "Kittatinny peneplain," but the name used above has priority.

The Appalachians thus furnish not only a typical example of a mountain system produced by the folding and upheaval of the rocks of the earth's crust, accompanied in many localities by breaks or faults and overthrusts, but also preserve the records of two well-characterized peneplains. The long and varied history of the range has been in part interpreted by geologists from the character of the rocks, the fossils they contain, and the structure that has been impressed upon them; but some of the most instructive chapters are recorded in the topography, and their study has led to a highly creditable advance in methods of geographical research.

The Appalachian Mountains when first seen by Europeans were clothed throughout with a varied and beautiful forest consisting largely of hardwood trees. Nowhere do they invade the region of perpetual snow, and glaciers are absent. These statements are true also for all of the mountains on the eastern side of the continent to the south of Hudson Strait.

The Appalachians abound in beautiful scenery, but, except about a few of the very highest domes and ridges, have little of the stern ruggedness which is typical of truly great mountains. Their countless valleys are now mostly cleared of their primitive forests and under cultivation. To a large extent also even the steep hillsides are tilled. The larger trees which formerly grew on the mountains have nearly all been felled, and where the land is not suitable for cultivation their place is taken by a dense second growth. Under the mild, humid climate that prevails, more especially from the vicinity of the Susquehanna River southward, the rocks are deeply disintegrated and decayed, and even steep mountainsides are mantled with soil and rock _debris_. It is the excess of disintegration and decay over erosion which gives to the mountains their usually flowing outlines and pleasingly picturesque rather than rugged scenery. The valleys still retain much of the material washed from the uplands, and are deeply floored with rich soil. The characteristic colours of this decayed rock-waste are many shades of red and yellow, which harmonize in a most artistic manner with the prevailing green of the plant-covered uplands and abandoned fields. These red and yellow soils, particularly about the bases of the higher summits of the southern Appalachians, afford abundant crops of cotton, corn (maize), and tobacco.

_The Mountains of New England, New York, New Brunswick, etc._--The picturesque Berkshire Hills, in the western portion of Massachusetts, have rounded and flowing outlines and a generally subdued relief. The more prominent of these greatly eroded remnants of what was once a mountain range rise but 2,000 to 3,500 feet above the sea. No satisfactory boundary between these hills of gneiss, schist, and allied metamorphic rocks, and the others of the same general character in the neighbouring portions of New York and New Jersey, has been determined. So far as the relief is concerned, and so far also as the complex geological history has been deciphered, there seems no good reason for separating the Berkshire Hills from the Appalachian Mountains. It is convenient, however, to consider the Appalachians as terminating at the Hudson. The Berkshire Hills when traced northward merge with a region of similar topography which unites them with the Green Mountains of Vermont, the highest summit of which, Mount Mansfield, attains an elevation of 4,364 feet above the sea. To the east of the Green Mountains are situated the still higher and more rugged White Mountains of New Hampshire, which culminate in Mount Washington. This widely known and greatly admired peak has an elevation of 6,293 feet, and, next to Mount Mitchell in the southern Appalachians, is the highest mountain on the eastern side of the continent to the south of the newly discovered group of peaks near Hudson Strait. Associated with Mount Washington are at least 15 peaks, each of which is over 5,000 feet high, and a still larger number of lesser summits which exceed 4,000 feet in elevation above the sea. The remarkable natural beauties of the Green and White Mountains, the ease with which they can be reached by means of railroads, and the numerous summer hotels, and hospitable farmhouses interspersed among them, make this, the most mountainous portion of New England, a favourite region for summer rest and recreation. The Green and White Mountains are nearly parallel north and south ranges, from 30 to 60 miles apart, and separated by a tract of lower but hilly country with a generally southern slope, where many streams unite to form the southward-flowing Connecticut River.

The Adirondack Mountains, in northeastern New York, are situated some 25 miles to the west of the Green Mountains, and separated from them by another tract of hilly country similar to the one dividing the mountains of Vermont from those of New Hampshire. In this space lies the irregular sheet of water over 100 miles long known as Lake Champlain. This beautiful lake discharges northward through Richelieu River to the St. Lawrence. In the same tract of hills, but to the southward of Lake Champlain and tributary to it, lies the smaller but still more charming Lake George.

The Adirondacks are rudely circular in ground plan, and measure from 60 to 70 miles from east to west, and about 100 miles from north to south. The entire area, known to the early settlers of New York State as the North Woods, is rugged and most pleasingly diversified. Its leading charms are the large number of dark, densely forested summits, the many beautiful lakes and clear, sparkling streams. The highest of the numerous steep-sided peaks is Mount Marcy, 5,344 feet, and second in rank is the equally beautiful eminence known as Whiteface, which rises 4,872 feet above the sea and about 3,000 feet above the adjacent valleys. Over 20 neighbouring forest-covered summits have elevations in excess of 4,000 feet.

The rugged region in northeastern New York and the adjacent portion of New England is in general without well-marked boundaries. On the north it extends into Canada, and is margined by the great valley through which flows the St. Lawrence. In the province of Ottawa, to the south of the St. Lawrence, there is a group of bold hills similar in many ways to the Green Mountains, known as the Notre Dame Mountains, which decreases in height when traced northward and merge with a roughened plateau which extends far to the northeast and embraces the Gaspe Peninsula and the table-land and hills of New Brunswick. Much of the country adjacent to the St. Lawrence on the south is rolling and hilly and contains large tracts of rich agricultural land which is highly favourable for dairying and sheep-raising. Mount Sutton, the highest elevation in the Notre Dame Mountains, is 4,000 feet high, and several other forest-covered mountain-like hills range in elevation from 1,000 to 3,000 feet. In the irregular valleys of this region there are a large number of lakes, situated in general from 700 to 1,000 feet above the sea. The Gaspe Peninsula to the north of New Brunswick, bordered on the north by the valley of the St. Lawrence, and on the east by the Gulf of St. Lawrence, has a rough relief and dense forests and is still a wilderness. The general elevation of the uplands in this little known region is about 1,500 feet. The surface is in reality a broad plateau in which numerous valleys have been excavated and from which rises a range of hills termed the Shikshock Mountains, some 65 miles long and 4 or 5 miles wide, with peaks ranging from 3,000 to 4,000 feet in height.

Much of Maine and New Brunswick is similar to the region just referred to, and, in a generalized geographical view, may be considered as a part of the great coastal plateau of the northeastern portion of the continent, roughened by erosion so as to appear to one travelling through its valleys as an endless succession of rugged hills. The highest of the numerous prominences in Maine is Mount Katahdin, 5,200 feet, and in New Brunswick the culminating summit is Bald Mountain, 2,470 feet.

The rugged region embracing the Adirondacks, together with the more elevated portions of New England and of the adjacent provinces of Canada, has many geographical features that are similar to those of the southern Appalachians, but at the same time this, the central portion, differs in a marked way from the southern extension of the Atlantic mountains. The higher mountains in each of these picturesque regions are at least in a general way to be considered as the unconsumed remnants of ancient uplands, the greater part of which have been eroded away. The most marked contrast in the scenery of these two regions of similar elevation is due to the presence of a great number of lakes at the north, many of them of large size, and the total absence of such beautifying elements in the landscapes at the south. The streams at the north are frequently impetuous and broken by many cataracts and rapids, thus furnishing abundant water-power; while at the south the streams flow through more evenly graded channels and are without cascades except near their sources in the mountains. These contrasts are such as are to be found the world over between regions of young and old topography. The differences in the degree of development reached by the streams of the New England region as contrasted with those of the southern Appalachians, finds an explanation in the fact that New England, Canada, etc., was formerly covered with glacial ice, and on the retreat of the glaciers the surface of the land was left with an essentially new relief, while the southern Appalachians were well to the south of the great ice invasion, and the streams of that region have reached a mature development, except near the sources of their head-water branches, which, like the topmost twigs of a tree, are always young.

The central, like the southern portion of the Atlantic mountains, is forest-clothed. All but a few of the highest summits in the Adirondack and White Mountains are concealed beneath a dense and varied growth of trees and shrubs. The summits, which are nearly bare of vegetation, like the upper 800 or 1,000 feet of Mount Washington, owe this condition to lack of soil rather than to elevation. Nowhere in the Atlantic mountains to the south of the but little known peaks near Hudson Strait, is the elevation sufficient to reach above what would be the timber-line under favourable soil conditions. The trees of the White and neighbouring mountains are principally various species of conifers, such as the pine, spruce, hemlock, larch, etc., which grow thickly on all but the most precipitous slopes. Before man disfigured the beauties of the land the lower hills, the river-valleys, and the borders of the numerous lakes and tarns were clothed with a more varied flora than the uplands. In these valley forests the dark foliage of evergreens is in summer mingled with the lighter green of maples, beeches, birches, oaks, locusts, and other broad-leaf trees. The forests are thus highly diversified and partake of the characteristics of both the northern and southern floras. It is in these northern woods that the glorious autumnal colouring for which North America is justly famous is to be seen in its greatest splendour. October is here truly the golden month of the year. At that season the bold hills, with their sombre robes of coniferous trees, rise like dark rugged islands above an undulating sea from which the most gorgeous sunset colours seem to be reflected. The brilliant colouring of the ripe foliage beautifies the land as with a cloth of gold. It is at this season also, during the tranquil days of what is known as Indian Summer, that a purple haze is thrown like a veil over the harlequin landscape, as if to subdue its glories and bring them within the range of man's appreciation.

Only a few of the higher summits in the New England region approach the scenic conditions usually associated with truly lofty mountains. In fact, the general lack of rugged escarpments as well as of great elevation leads the geographer to rank even the highest of these rounded summits as hills of large size rather than attempt to burden them with the dignity that the term mountain carries with it. They are beautiful hills, separated one from another by lovely valleys, which draw the beholder to them and fill his memory with tender longings and vague dreamy fancies such as the sterner grandeurs of great mountains fail to awaken.