PART II.

A more extended Investigation regarding the Earth’s Surface.

It is the province of Hydrography to deal with the oceanic world; Geography proper concerns itself simply with solid forms. The Hydrography of the globe we must pass over, however. Aside from the fact that it would lead us into studies of the most protracted nature, it forms strictly one department of nautical science. Besides, there is the less occasion to speak of it here at length, that works of great excellence have been published, relating to that branch. We turn therefore to the land, and shall study the world of waters only so far as it exerts influence on the land.

By land we mean the islands as well as the continents, for, as remarked before, the difference between them is merely relative. To the land division of the globe, however, belong all rivers and the internal fresh water lakes, however large. The basis of difference does not lie in the fact that one part of the globe is water, the other part land, but in the fact that one is a tract of uniform evenness, the other of constantly varying surface, the internal rivers and lakes only being frills, so to speak, to the elevated region, and not sharing the sea level of the great oceanic mass. Uniformity of surface is then the chief characteristic of the sea; a lack of it, of the land. A mathematical level is a thing unknown on extended districts, and an approximation to it is very rare. Even the basins of former seas do not display a perfectly level bed. The plains of North Germany are characterized by this billowy rolling. The flats along the Danube, in Hungary, and along the Po, in North Italy, have really important deviations from a true level, though the eye is not able to discern them. Milan is four hundred feet above the Adriatic; but the eye does not discern that it is not at the center of a plain as perfect as the surface of the sea itself, and yet that plain does shelve gradually away till the Adriatic checks and defines it. Pesth is two hundred and fifteen feet above the ocean level, yet the gradual decline to the Black Sea is undiscernible to the eye. The immense plains along the Amazon, even the celebrated llanos on the Orinoco, which Alexander von Humboldt likens to inland seas of verdure, have a not insignificant slope from west to east. The middle point of these llanos near the City of Calabozo, about 100 geographical miles from the sea, he found to be 180 feet above the sea level; far lower indeed than Milan or Pesth, relatively, yet at a perceptible elevation. All of these plains were once the bottom of the sea; the Adriatic laved the base of the Apennines and the Cottian Alps, and the Atlantic swept westward over the llanos of the Orinoco and the Essequibo, having the Sierra de Venezuela on the north and the Sierra Parima on the south, till it was checked by the Cordilleras of Merida and Pamplona.

Depression and elevation, then, are the characteristics of the land. They are both measured from the level of the sea; their absolute altitude is reckoned from the imaginary sea level, extended over the whole globe. Their mutual relations to each other are determined from their relative heights. The absolute elevation above the level of the ocean can be determined in a number of ways. If the heights to be measured are in the immediate vicinity of the sea, a simple system of triangulation will effect it. If they are removed from the sea, the difficulties are greater, and increase according to the distance from the sea. The heights of great inland mountains are determined by complicated operations with the spirit-level, protracted trigonometrical calculations, the unwearied and skillful use of the barometer, and constant appeal to the boiling point of water. The description of these methods falls within the province of Physics.

As the determination of the heights of the loftiest mountains could not be made before the appointments of scientific explorers have attained to a certain degree of accuracy and delicacy, the knowledge of them in former times was almost wholly relative. The inquiries of La Condamine, Saussure, and de Luc, in the Andes and the Swiss Alps, are almost the only ones to be trusted among those of the older observers. All unscientific travelers without accurate instruments confounded absolute heights with relative heights, and innumerable errors crept therefore into the earlier text-books. It is only within the most recent times that Hypsometry has attained to the dignity of a science.

To meet and counteract the errors alluded to above, and current in the loose language of popular speech, we shall use a new and indeed arbitrary terminology,—arbitrary because the data which mensuration will sometimes furnish are now, in part, wanting. We will divide the earth not relatively, but absolutely, into highlands and lowlands. The great districts often met, whose elevations are very moderate, we call lowlands. They are, for the most part, immense plains, varied but little above the level of the sea. The great districts which inclose mountain ranges we call highlands, and sometimes plateaus. True highlands can often embrace very extended and elevated plains, and these plains again may include hills and mountains. This does not affect their character as highlands, which lies in the fact of elevation rather than in more or less modified variation of surface. There may be vast variety in the physical manifestations of a great plateau district, entirely independent of the relative effects produced by the distribution of its surface into plains, rolling land, hills, and mountains.

In the lowlands there may exist hills to some extent, and these may even be combined in ranges, provided only that they do not violate the uniform characteristics of the district in which they are found.

The highlands are generally met with in the interior of the continents; the lowlands at the coasts. Yet there are exceptions to this.

In the transitions from lowlands to highlands there is great diversity. We can speak of three distinct bases of discrimination: a sudden and abrupt ascent; a rise in elevation so gradual as scarcely to be perceived; and a terrace formation. Yet in these there is a blending of one variety with another; there is no place sharply marked, where we can say that one form ends and another begins. There are constantly found modifications of these three transitional phases. The plains along the Indus and the Ganges rise sharply to the plateaus of Thibet The flat Pacific coast of South America is exchanged with equal abruptness for the highlands of Peru. The transition is a gradual one from the lowlands of North Germany, along the Baltic and the North Sea, through Saxony and Bohemia to the Bavarian highlands, north of the Alps. The Spanish highlands form a series of terraces, increasing in height from south to north. The immense plateaus of central Asia are also terrace formations, of diminishing elevation, as they advance to Siberia; so, too, are the eastern plateaus of Peru, falling off in altitude toward the plains of the Amazon.

Just as varied are the heights taken from the sea level of the leading plateaus. Yet they never rise to a point of elevation comparable with those of isolated mountain peaks or ranges. These attain, in no insignificant numbers, the height of 24,000 feet, while some ascend thousands of feet beyond that. In Mount Everest, of the Himalaya chain, the loftiest summit yet measured (29,000 feet) is found; although it may be that future investigations more to the south will disclose yet greater heights.

Highlands.

Continuous highlands or plateaus seldom attain an elevation greater than a half or a third of the loftiest mountains; the most elevated range in altitude, from 8000 to 12,000 feet above the sea level. On an average, they lie about 4000 to 5000 feet above the sea. We take the last height as a convenient point of demarkation between the two classes of highlands—those of the first and those of the second magnitude. It is an arbitrary point, of course, and the division there must remain, without a natural base to rest upon, till more results in Hypsometry shall have determined the real point of average between the combined lowlands and the combined highlands of the earth’s surface. Meantime this division will be of great service to us in enabling us to bring into a definite and appreciable classification many facts which would otherwise not be so well understood in their relations.

_Highlands or Plateaus of the First Class._

By plateaus of the first class, we mean those high, continuous plains which lie at the elevation of more than from 4000 to 5000 feet above the sea level. The extreme height to which such plateaus rise is a fact yet to be ascertained. At an elevation of from 4000 to 5000 feet the highlands of the first class merge into those of the second. The point of transition is, of course, very difficult to fix with precision.

The high plateaus of Asia rise more than 14,000 feet. They inclose the head-waters of the Ganges and the Indus. All central Asia is a vast congeries of highlands; but, as a body, they by no means belong to the most elevated of the globe. They are colossal in their length and breadth, but not in their uniform altitude. In the latter respect, they are far more varied than is generally supposed.

The plateau of Thibet attains, in its whole great extent of 1800 miles in length and 500 miles in breadth, an average elevation of 10,800 feet above the sea level. In some cases it rises, of course, much higher, as, near the holy lake Manasarowar, for instance, where it is 14,000 feet above the sea. Others sink, as at Ladakh, in Little Thibet, to an altitude of about 9000 feet; so, too, Gertope, in the region remarkable for its goats and the rich shawls manufactured there, and Shiffke, are about 9804 feet above the sea. The plateau of Great Thibet, east of Lassa, the capital, and north of the Upper Brahmapootra or Yam-Dzangbotscha, is 9000 feet in elevation. There are also districts filled with mountain groups of great heights, but where the depressions sink to the level of the valleys of the Indus, Sutlej, Brahmapootra, as low indeed as 5460 feet, as at Cashmere, so that there is no lack of diversity in the great plateau of Thibet.

The plateau of Mongolia, or more exactly the desert of Gobi, can be ranked only on its lower edges, where it touches the Chinese frontier, as of the first class, although in extent it is twice as large as the great plateau of Thibet. Only near the north bend of the Hoang-Ho and near Peking does it reach an altitude of 8000 feet, and gradually sinks away as it advances toward the northern frontier of the Chinese territory, to 5100 feet, and farther north to 4000 feet; in the middle portions of the great table-land it is depressed to a height of 2400 to 3600 feet; it rises again at the head-waters of the Orkhon and the Toola to an elevation of 4620 feet, and falls off in terraces toward Kiakhta, near the northern boundary, where it is 1330 feet high, Selenghinsk, on the Selenga, where it is 1632 feet high, and Berch-Udaisk, where it is 1458 feet high, till it reaches Lake Baikal, 1332 feet above the sea level according to Humboldt, though Erman makes it greater.

Western Mongolia, (west of the meridian of Lassa, and west of the point where the Tarine flows into Lake Lop,) upper Bokhara, and upper Toorkistan were formerly considered to be a highland district; this is now subject to doubt. We shall discuss this further on.

Africa, too, has highlands of the first class, which, however, do not rise to the extreme height of the plateau of Thibet. As in Asia, so in central Africa, the old supposition of the existence of a plateau of colossal extent has been very much done away with by the more exact and critical modern investigations. The strip of territory lying between 4° and 10° north latitude has been demonstrated by Barth and Vogel to be destitute of highlands. The range of mountains announced as discovered by Mungo Park, and called the Kong Mountains, is proved to have no real existence, and of course his statement fails of verification that that range is the northern limit of an elevated central plateau. The peaks which really do rise in the Kong territory form no continuous ridge; they are mere isolated groups of moderate height. Between these groups the lowlands continue toward the south, in an unbroken level, for an immense distance. How far south of the equator the central African plateau begins, is yet unascertained, for the snow-tipped peaks of Kilimandjaro and Kenia, discovered by Rebmann and Krapf, in the parallel of Mombas, 1° to 3° south latitude, are of immense height, it is true, but they do not demonstrate the existence of a plateau of the first class there. They rise out of table-land about 2000 feet above the sea level, which Krapf explored in the year 1849.

The Abyssinian plateau, on the contrary, takes rank among the most elevated on the globe. At 10° north latitude, south of the sources of the Blue Nile, lies Upper Abyssinia, or the kingdom of Shoa, with its capitals, Ankobar and Angolalla, 10,000 feet above the sea. Still farther to the north, in the ancient kingdom of Gondar, the German naturalist Rüppel ascertained the level of Lake Tzana to be 7000 feet above the ocean; to the southward of that the land rises to a still greater height, and northward of Gondar the plateau ascends to an elevation of 8000 feet, and mountains are met with 14,000 feet high. The terrace of Axaw on the east is 6650 feet above the Red Sea, which lies along its border.

To the south of Shoa lie the highlands of Kaffa and Enarea. All travelers agree in the statement that the inhabitants of that region are light-complexioned; and Johnson draws from this the conclusion that the central plateau must rise to a height of over 10,000 feet to harbor people of a whiter hue than the dwellers of the less elevated localities. He saw a number of men of light complexion who came as far as from the fifth degree south latitude, not from mountain homes, but from high table-lands.

The plateau of South Africa rises at Lattakoo, in the country of the Bechuanas, north of the Orange River, to the height of 6000 feet. To the east, near the Snow Mountains, where the river has its source, it ascends to an altitude of over 10,000 feet. To the north, discovery had made great progress since 1849. There, on a broad plateau, Oswell and Livingstone brought to the knowledge of the world the existence of Lake Ngami, whose surface is 2825 feet above the level of the sea. The plateau which includes this lake at its place of deepest depression cannot be less than 3000 feet high, and at some localities yet higher. Still more to the north, at latitude 14° south, on the water-shed between the Zaire or Congo on the west and the Zambeze in the east, the plateau reaches an elevation of 5000 feet, according to Livingstone. Yet farther to the west, it rises still higher and takes undisputed rank among plateaus of the first class. There, at 18° south latitude, Galtne, on his journey of discovery in 1850, ascended the table-land of Ovompâ, a region of great natural productivity. On the way thither, going from south to north, at 21° south latitude, and therefore in the parallel of Lake Ngami, but about 500 miles westward, he ascended north of the Swakop River, the table-land of Demara, which he found to be 6000 feet high. From that plateau mountains, Koniati and Ometako, for instance, rise to a height of 8800 feet. From the Swakop River to Lake Ngami there is a continuous plateau.

The high table-land of southern central Africa does not then extend, as was once supposed, as far north as 9° north latitude, nor even to the later limit of 4½° north latitude; but at about 4° 10′ the distinction between lowland and highland seems to be sharply drawn, as the cataracts which terminate the navigation of the White Nile indicate. Here Father Knoblecher turned back in 1849, but he ascended the first of the mountains which there began to rise; his eye reached onward to mountains very near or on the equator. He says that those high mountains stand upon an elevated table-land. Thus, here at the source of the White Nile we have a plateau seemingly of the first rank. From such a plateau it is probable that the snow-capped mountains, seen by Rebmann and Krapf in the neighborhood of the equator, rose, which they thought, approaching from the eastern coast, held the source of the Nile.

At the northwest of Africa, too, at 10° north latitude, the territory which feeds the springs of the Senegal and the Niger is supposed to be a plateau of great elevation and of great extent. But at present our lack of knowledge prevents our attaining certainty regarding it. No thorough system of measurement has been yet applied there.

America possesses a number of plateaus of the first class. To the most prominent of these belong the ones which were first thoroughly studied by Alexander von Humboldt. It is to him that we owe our first accurate impressions of table-lands which, before his day, had been indiscriminately confounded with mountains, and had had no place assigned to them in the department of Geography. Doubtless, too, great prominence was given to plateaus at the outset; they were pushed into unseemly proportion to other matters as well worthy of investigation, but they have come into their true place, and now only wait the development of new facts regarding the size and height of some, to be properly understood and appreciated.

The measurements made in North, Central, and South America give the following results; much more complete, it may be remarked, than the results yet gained in Asia and Africa.

To the plateaus of the first class belong in America, at latitude 0°, the plain of Quito, almost 9000 feet above the sea, (Los Pastos in the north being near 11,000 feet,) and to the south, at 17° south latitude, the plateau of Upper Peru. Here the great Lake Yiticaca is found, 12,000 feet above the sea; eastward of the lake, the table-land rises yet higher, and at Alto de Toleda it is 14,000 feet in elevation, as high as the highest part of Thibet. At 20° south latitude, south of Lake Yiticaca, is the City of Potosi, whose streets are 12,822 feet above the Pacific.

In Central America is found, at 20° north latitude, the extended table-land of Mexico, 500 miles wide, rising to a height of 7000 feet, and farther to the north, in New Mexico, the plateau of Santa Fé, 35° north latitude east of the Rocky Mountains, and 7100 feet above the sea. The table-land on the west side of the mountains, and toward the Great Salt Lake, is undoubtedly just as elevated.

Europe and Australia are wanting in plateaus of the first rank, and in general the whole immense flat northern districts of the globe, though we are not yet quite familiar enough with the extreme north of America to speak with entire confidence regarding it.

_Plateaus of the Second Class._

Elevated plains which are at once continuous and bounded by a definite line of demarkation, and which do not attain an altitude of more than 4000 or 5000 feet, are considered plateaus of the second class. They are far more general over the whole earth than plateaus of the first class; in every one of the great divisions of the globe they appear in the utmost possible diversities of elevation, sometimes so gradually ascending that the lowest limit is hardly to be perceived. This makes it not only expedient but necessary to assign to plateaus a fixed though arbitrary system of classification, for without it we could attain to no thorough view of all their relations. This general system must afterward be confirmed and justified by protracted special investigations.

That not all the vast plains of Central Asia, from Thibet to the Altai Mountains, and from the Belur range to the Chinese Gobi, belong to the first class of plateaus, has been demonstrated by the Russian measurements, made by Fuss and Bunge in 1832, between Lake Baikal, Kiakhta, and Peking, and rendered highly probable by the investigations of Klaproth, Humboldt, and Zimmermann. Toward the northwest the plateaus generally sink from the moderate elevation of the Middle Gobi, 4000 feet, to Lake Baikal, 1332 feet above the sea, Lake Zaison, not 1000 feet above the sea, and the border of the plateau at Choimailocha, the Chinese frontier post on the Siberian line, 1000 feet above the sea, then to the lower border of the plateau of Bookhtarminsk (936 feet) and Semipalatinsk on the Irtish, (708 feet,) where the great Siberian plain begins. In the valley of the Tarim and of Lake Lop, pomegranates and grapes thrive, and cotton, which has been raised of an excellent quality in Eelee, is found at a height of from 1200 to 2000 feet. And in contrast with the great arctic plain of Northern Asia, not 500 feet above the level of the sea, this central plateau will take its place as distinctively of the second rank.

The plateau of Persia lies on the border of both classes; for while the central portion touches 4000 feet, some parts rise much higher and some sink much deeper than the normal point. These balance each other, and the average is about the maximum elevation of plateaus of the second degree.

East of the Persian plateau lies the plateau of Cabool, 6000 feet above the sea. On the northern edge of Afghanistan is the plateau of Bamain, 7500 feet in elevation. More to the south is the high plain of Candahar, being 3500 feet, and the City of Candahar, 3264 feet above the sea. The plateau of Kweltah west of the Bolan Pass is 5220 feet. Still farther to the south is the great plain of Beloochistan, 7000 feet, with the City of Kelat, 5418 feet above the sea.

In the central part of the eastern Persian plateau in ancient Gedrosia, Drangiana, and Parthia, and Lake Zareh, the depression is the lowest. At Lake Zareh the elevation is 2100 feet; at Herat, more to the north, 2628 feet. In West Persia, on the meridian of the Caspian Sea, it rises higher; on the northern edge at Teheran it is 3672 feet; at Schabred, southeast of Astrabad, it is 4000 feet; at Kasbin, west of Teheran, it is 4000 feet; and at Samegon, 5700 feet. The lowest depression at Com and Kashan is not 2000 feet above the sea. Toward the northwest Persia thrusts up a short arm into the adjoining territory of Armenia. This is the highland of Ayerbaijan, Zoroaster’s “Land of Fire.” This connecting plateau of 7000 feet elevation belongs to the first class. To the west of this the plateau of Armenia extends in varying range of elevation, from that of Lake Van, 5124 feet, to the plain of the Aras, (the ancient Araxes,) on which the double cone of Ararat rises to a height of 14,656 feet. But the table-land at the northern base of Ararat, the site of Erdschmiazin, is only 2860 feet high, Erivan a little higher, and Erdzeroune, on the plateau of the Taurus, the plain of the Upper Euphrates, 5730 feet.

The plateaus of Asia Minor embrace wide plains extending through the whole of the country, at an elevation toward the east, in ancient Lycaonia and Cappadocia, of 3000 feet, and sinking toward the west to 2000 feet.

To the plateaus of Armenia and Lycaonia, Strabo, whose home was there, and who carefully studied them, gave the expressive name of ὀροπέδια, _i.e._ mountain plains, a term which corresponds remarkably with our word plateau, but which, as Humboldt has remarked, was not of much use among the ancients. Strabo, however, directed attention also to the Oropedia of Sicily and India.

In India, Deccan displays similar formations, which rise gradually from south to north in Mysore, in Poonah of the Mahrattas, and in the table-land of Vindhya and Malwah, to 2000, 3000, and even 4000 feet. Deccan enjoys an admirable climate and the richest abundance of all natural productions. China too must have plateaus, for the Chinese word _youen_ indicates very clearly a large elevated plain.

In Arabia the plateaus of the second class are largely found, and their height ascends from north to south, instead of from south to north as in Deccan. The Syrian Hauran is 2000 feet high, the plateau of Damascus 2200 feet, the plateau of Taif, above Mecca, 3000 feet, the plateau of Sapaa, in Southern Arabia, 4000 feet.

In North Africa that portion of the great Sahara which has heretofore been considered a low plain, lying between Tripoli and Lake Tchad, has been ascertained by the German explorers, Overweg and Vogel, to be a table-land of the second class, ranging in elevation from 1000 to 2000 feet. It begins at the Chorean plateau (2000 feet) in the south of Tripoli, and sinks to an elevation of 800 feet in the neighborhood of Lake Tchad. The average altitude is about 1500 feet. This moderate elevation of Sahara corresponds with the equally high plateau of Cyrenaica, 2000 feet.

The Atlas plateau, in the northwest of Africa, rises to a greater height—2000 to 3000 feet; the upper course of the Draa, near the Sahara, being 3000 feet; the high, broad table-land on which Timbuctoo lies, according to Renon’s measurement, is 1500 to 1800 feet above the sea.

In south Africa the low, or rather the moderate plateau, which borders the district of the Bechuanas on the north, rises, as it advances toward the lower rim of Africa, at Cape Colony, to an altitude of 3000 feet.

America has many plateaus of the second range of elevation, but her highlands of the first class are so imposing in extent, as well as in elevation, that they have been more carefully observed than the table-lands of the second class.

Along the eastern slope of the Andes, on the same parallel with the great plains of the Orinoco, the Amazon, and the La Plata, these plateaus extend, touching the base of the mountains, and appearing rather as terraces, or vast plains of transition, from the highlands to the lowlands, than as independent forms. Where Alexander von Humboldt measured them, west of the low plains of the Amazon, he found their height, measured from the sea, to range from 1050 to 1200 feet; he describes them as having the appearance of vast plains, and as differing from the lowlands of the Amazon only in their greater elevation; their slope toward the narrowing of the Pongo de Mauseriche being too slight to be appreciable.

Between the threefold forks of the Northern Andes, Humboldt ascertained the heights of ten plateaus, extending as far as the plains of Orinoco, and called by the various names, according to their elevation—Tierras templadas, or temperate districts, Tierras calientas, or warm districts, and Tierras frias, or cold districts—varying in height from 1800 to 6600 feet, the highest belonging clearly to the first class of plateaus.

The mountains of Brazil are interspersed among plateaus of the second class. The Brazilian mountains are not true ranges, but lie in groups, their height varying from 2700 to 5700 feet, and between them are the vast elevated plains, called Campas, which are true plateaus of the second class.

The southern point of South America, south of the Rio Negro, as far as the Straits of Magellan, known as the plateau of Patagonia, is a true table-land of from 1200 to 1400 feet in height. It is composed of ragged strata of porphyry or of vast lava-masses, and has been explored by Captain Fitz Roy, in 1837, from the mouth of the Santa Cruz River to the snow-capped Andes in the west. The plateau diminishes gradually in elevation from west to east, till it touches the sea line.

In North America the broad plateau extending through Northern Texas and the Indian Territory, and lying on both sides of the Arkansas River, increases in elevation gradually from St. Louis, on the Mississippi, less than 500 feet above the sea, to Santa Fé, on the upper course of the Rio Bravo, 7000 feet above the sea. It ascends so slightly that the rise is imperceptible to the eye, the broad plains there taking the name of prairies. St. Louis is 420 feet in absolute elevation; the eastern Arkansas plateau 1500 to 3000 feet; the high western Arkansas table-land from 3000 to 7000 feet, where, at the point of greatest altitude, lies the City of Santa Fé, in the Territory of New Mexico, 7047 feet above the sea. This broad, sloping tract reaches out to a great extent at the north, crossing the Missouri, and embracing the colossal North American lakes. Lake Huron and Lake Michigan, about 578 feet deep, and Lake Superior, 627 feet deep, lie in vast hollows in that great continuous plateau, which extends into the British Possessions, rises again to 800 or 1000 feet in elevation, and is rocky and craggy, yet not enough so as to take the name of a mountain chain, but simply to form a clearly-marked water-shed, which Fremont and Nicollet have measured.

In Australia and Europe plateaus of the second grade of elevation are not wanting. In Australia, however, they are limited to the triangular district in the southeast, which has become the place of settlement for the chief English colonies, and which, bearing the name of King’s Table-land, rises to a height of 2500 feet, and occupies the largest area of all the Australian table-lands.

In Europe this physical feature is displayed most distinctly in the Spanish plateaus, which occupy by far the largest proportion of the entire peninsula. Madrid lies on one of these plateaus, at a height of 2100 feet, five times as high as Paris, on the Seine, and as high as Innspruck, in the very heart of the Tyrol; Toledo, in the valley of the Tagus, is 1734 feet above the sea. The average elevation of New Castile, the central part of Spain, is 2000 feet. Old Castile, which borders it on the north, separated from it by the Guadarrama ridge, is about a thousand feet higher. Burgos, in the center, is 2700 feet above the sea; Segovia, to the south, 3100 feet. The average elevation of Old Castile is 3000 feet.

Then comes in natural order the Bavarian plateau, in southern Germany, ranging from 1500 to 1600 feet high, a broad table-land, on which lie Munich and Augsburg. It extends along the course of the Danube from west to east, from Lower Switzerland to Ratisbon.

According to the mean measurements of Humboldt, the lower plateau of Auvergne, in southern France, is 1040 feet in elevation; still less in altitude (840 feet) is the plateau of Burgundy and Lothringia, between the Vosges and the Ardennes. Limousin, Aveyron, la Forez, Monts, and Côte d’Or are plateaus.

The plateau of Lothringia, whose mean elevation is 648 feet, lies between the Rhine and the Moselle. The plateau of Luxemburg extends northward to the Eifel, where Prum lies, and to the Ardennes, where Malmedy, Eupen, Namur, Liege, and Aix-la-Chapelle lie.

In Middle Germany, a series of plateaus of the second grade begins in Upper Hesse, and extends eastward, crossed by mountains and valleys, traversing Upper Silesia and Galicia, and running along the northern side of the Carpathian Mountains to Podolia, on the Dnieper, thus embracing a strip extending through the larger part of central Europe.

A line of plateaus begins still farther to the north, at the low hills of Jutland, crossing Holstein, Mecklenberg, the whole southern edge of Pomerania, and extending to Lithuania and the Valdai Hills. It is characterized by a band of inland lakes, whose basins it incloses, and is crossed by the valleys of the Oder, Vistula, Niemen, and Duna. It has been called the Pomerania lake country. In the hollows where the lakes lie, (whose surfaces are, at the highest, not more than 300 feet above the sea,) and yet more in the depressions, where rivers break through, the level descends to as low a point as that of the great plain of Central Europe; but at other places it rises to an elevation as high as 500 feet, and so touches upon the limits of plateaus of the second range. Many parts of this broad upland may possibly be formed of shifting sand dunes which have been gradually piled up along the sea line. The plateau reaches its highest point at the eastern end, in the Valdai Hills, where it averages 1000 feet in elevation. The highest point is 1100 feet. East of the Volga, which rises at the eastern side of these hills, the plateau falls off by imperceptible steps, till it is lost in the great Russian plain.

In the peninsulas of Southern Europe, as in the Morea, (2000 feet,) and in the Crimea, (800 to 1200 feet,) the plateau again appears in not insignificant proportions.

The lower range of plateaus, it will be seen, is far more frequently met with through all parts of the earth than the higher, yet both combined occupy a larger share of the surface of the globe. We can designate them as sharply defined and broadly massive elevations, in contradistinction to the long, narrow, and broken masses which have received the name of mountain chains. The latter have too often been confounded with the former and have received from geographers a treatment disproportionately full in relation to their claims. The plateau has been until recently an almost forgotten geographical element. Humboldt restored it to its rightful place; by many hundreds of measurements he has accurately settled its form, its effect on climate, on isothermal lines, on agriculture, on the physical and moral life of nations, and even on the course of human history.

In closing this attempt at a general consideration of plateaus, I must confirm the reproach which Humboldt has cast upon most geographers of this day for their abuse of the word plateau. And I must at the same time admit that it is justly due to some parts of my own “Erdkunde,” where I have considered the plateau systems of Central Asia and Africa. When I wrote the pages of that work, thirty and more years ago, there were no scientific measurements then made of those regions, and the general ignorance led to a premature generalization, in which I used the ascertained features of the New World as probably in analogy with the unexplored center of the Old World. This use of really untrue analogies was carried by others to great lengths, and choratographers went so far as to depict the country according to the hypothesis of those who had written at first hand, and after using all the lights then existing, but who had never supposed that what they had indicated in general terms, would be afterward made so definite and real to the public eye. Those untrue statements of my own, I must leave however just as they are, and rejoice that the great advance of science has led to the accurate knowledge of the great plateaus of which the civilized world then knew but little. One word more: I set the lower limit of plateaus of the second grade at 500 feet, lower therefore than the great master in Physical Geography set his.

“Elevations of the soil,” says Humboldt, “which do not display a marked difference in climate and vegetation from the country around them, are not rightly called plateaus.” His meaning is, that the name does not relate to absolute height measured from the sea, but harmonious climatic relations existing between contiguous districts, one of which is more elevated than the other. Highland and lowland are therefore to him words of unfixed meaning, if they do not stand in the contrast of height, climate, relief, and rates of temperature. Humboldt therefore did not consider the depression of Central Asia, at the Taringol, as a plateau; and table-lands from 200 to 1200 feet in absolute elevation, _i.e._ from the sea level, are passed over by him as not worthy of the same name which he applied to the plains 6000 to 10,000 feet above the sea.

Dealing as I do with the elementary features and the physical contrasts of countries which for the most part are now thoroughly explored, I prefer, for the purpose of elucidating the subject of Physical Geography, to consider the plateau as beginning at 500 feet above the level of the sea. By comparing the plateaus of both hemispheres it is not difficult to deal with a variety of features, and to make a number of discriminations which, without an absolute standard, it would be impossible to make.

We pass to the consideration of the much more varied and more imposing characteristics of mountains.

Mountains and Mountain Lands.

Mountain lands cannot, in the strict use of language, be compared with plateaus, except in way of contrast, because they are not uniform, broad, and sharply defined tracts, but extend in a linear direction, having as their chief feature the longitudinal axis of the mountain chain. Groups of mountain ridges may be separated from each other, or may be united in any coherent way which does not make them continuous, and yet, despite the want of continuity, form a perfect whole.

Mountains, with their fissures, chasms, abysses, valleys, ravines, clefts, precipices,—in a word, their varied diversities of feature, broken through in every direction, the whole chain rent into fragments by these transverse breaks, are in direct contrast with plateaus. They have quite often a common range of elevation, which, measured from the sea level, is not unfrequently much greater than the districts lying at their base. Yet this relation is only incidental, it is not essential. There is no necessary connection between the height of the outlying plateau and the height of the mountain range. In Switzerland the mountains rise to the altitude of 13,000 or 14,000 feet; the country at the foot of the Alps is but 1000 to 2000 feet above the sea. Here the distance between the summit and the plateau at the base suggests no relation between them.

The distinctive characteristic of a mountain land is the height of isolated groups. Great differences of elevation within small distances characterize mountain regions; small differences within great distances characterize plateaus. The plateau depends upon uniform evenness of surface, or an approximation to it, over a large extent of territory. The mountain range is the exact opposite, the development of all kinds of extremes within a limited space, and the consequent individualization of the locality where it stands. Mountain lands cannot therefore be identified with the type of the highland and the plateau. The mountain chain has a character of its own, whether existing in unbroken unity, or subdivided into subordinate ranges, ridges, and spurs, and whether the summits are conical or sharply pointed,—whether also of moderate, medium, or loftiest elevation.

And high as mountains rise, their height is equivalenced by the depth of the depressions which form their valleys; the higher the mountain, the deeper the abyss which cleaves to the base. The immensely elevated peaks of the loftiest chains find their correspondence in the narrow ravines and the mountain lakes at the foot; the precipitous summits of the great American chain have their barrancos in the Andes and their cañons in the Rocky Mountains. The valleys are in natural contrast with the summits. They have just as little of the uniformity of lowland plains as the mountain tops have of the uniformity of elevated table-lands. They are infinite in variety, highly individualized, and always adapt themselves to the characteristics of the chain which conditions them. The mountain, too, has no uniformity in its character; it embraces within the smallest compass the production of all climes, and unites the characteristics of both highland and lowland. Mountain regions have therefore had a great influence in history and in the development of humanity, even greater than the more monotonous plateaus, which in general harbor nomadic races and give little encouragement to permanently settled people. For this reason the geographer cannot, like the geologist, classify high table-lands and mountains together; he cannot draw the same inferences from the plateau as from the mountain range; to the geographer the plateau is not a lower type of mountain, but the two, in their relations to man and to history, suggest entirely different results and condition entirely different processes.

And yet it must be confessed that mountains do stand in intimate connection with plateaus of both classes, and that the transitions from the one form to the other are well worthy of study. Yet the present lack of correct measurements has made this little understood.

It is not the element of height alone which gives mountains their significance. There are many other features, which are little studied, yet of real import. It is, however, not a matter of indifference whether a chain thrusts up its peaks 1000, 5000, 10,000, or 20,000 feet, and the height has been made and will continue to be made a subject of careful investigation. In reference to height, we distinguish what, in a general sense, we call mountains,[3] into hills, mounts, and mountains of various degrees of magnitude. Yet the height of the highest range, in comparison with the diameter of the earth, is insignificant, only about ¹⁄₁₇₀₀, and the combined mass of mountains are of no more account in comparing them with the entire mass of the globe, than the roughnesses on the rind of an apple, or perhaps more exactly still, than those on the shell of an egg. The combined mountain systems in the world would not suffice, if transferred to the North and South Pole, to fill out the earth to such an extent that the polar and equatorial diameters would be equal.

In following out his profound scientific investigations, Alexander von Humboldt, in order to ascertain the center of the earth’s gravity, taking into account the existing elevations above the ocean level, was led to the conclusion that too great importance was formerly assigned to mountains in their relations not to the course of history, but to the earth as subject to mathematical laws. Very careful observations revealed the fact to him that all the mountains of France, if reduced to a level and spread out, would raise the grade of the whole country to a height not more than 816 feet above the sea line. All the mountains of Europe, distributed in like manner, would raise the level to only about 630 feet. In Asia the same process would make the vast plain only 1080 feet high, in North America 702 feet, in South America only 1062 feet; while the mountains of the entire globe would raise the level to only 947 feet above the level of the sea. So insignificant are the combined mountain systems of the earth in respect to size, in comparison with the immense body on which they stand, though their importance is great when we regard their influence on the localities where they are found. Yet in this last regard, mountains deserve careful study, for they not only exercise and have exercised a great influence over nature and man, but they serve as our best key to open to our view the internal structure of the earth.

Some mountains, though of great height and broad base, like Etna, Vesuvius, Teneriffe, and many volcanoes, belong to no true mountain system; and even when they lie near together, and yet have no inner principle of unity, they are not spoken of as a chain or a range: they make merely a mountainous district. It is the repetition of the common type and the existence of a continuous valley which gives a right to use the names chain and range.

The linear extent and height of mountain ranges vary very much; no definite limits to these can be assigned. Yet there are few chains which are less than 25 miles long and 1500 feet high. Other features are necessary in order to determine the strict application of the word chain or range; one is a ridge-like or comb-like aspect; (that it should be a water-shed is not essential, although very common;) another feature is that the rock composing it should be of the same geological formation. Sand dunes, although occurring in regular and ridge-like uniformity, like those in Holland, and looking from a distance like a mountain chain, are not to be reckoned as mountain chains, though like the tells on the Syrian steppes and dunes in the Netherlands and along the Baltic coast, they sometimes rise to the height of a thousand feet. In South Germany and in the neighborhood of lofty mountains, such elevations are called mere hills; at the north foot of the Alps, yet greater heights are almost always called level land. In judging of the fitness with which the word mountain is used, it must always be remembered whether he who employs it dwells among the Himalayas or on the lowlands of eastern Europe; and in order to give any fixedness to the use of the word, it is necessary to take into account other physical characteristics besides height. By common usage, however, the Alps have become the standard of comparison for all the mountains of the world, mainly because, besides having their imposing height, they are found in the middle of the temperate zone; they are the most convenient to study of any great system on the globe. In respect to height, we divide these into four grades: the lowest from 2000 to 5000 feet above the sea; the next from 5000 to 8000; the next from 8000 to 10,000; and the highest from 10,000 on to the height of Mont Blanc.

Another standard might be found in the colossal Himalaya chain of Asia, and the Cordilleras of both Americas, which could easily be brought into unison with the Alpine chain of Switzerland.

The linear direction of a mountain chain, the axis of elevation as we might say, (so sharply hinted at in the very word mountain-chain,) brings out relations which vary not only according to the longitudinal direction itself, but to the lateral extent, the number of mountains, the situation, and the ramification of the chain. If the direction be a straight one, we can rightly speak of an axis of elevation. According to Humboldt’s measurements, this axis in the Pyrenees is 230 miles in length; in the Alps, from Mont Blanc to the Hungarian frontier, 515 miles; the Ural Mountains, 550 to 2042 miles; the Scandinavian Mountains, 1100 miles; the Altai Mountains, 9900 miles; the Kuenlun, 1600 miles; the Thian-Shan, in Inner China, 1700 to 2150 miles; the Himalayas, 1600 miles; the Yablonoi Chrabet, 550 miles; the Aldan, 400 miles; the Ghauts, 760 miles; the Andes of South America, 4400 miles; and the whole Cordillera of North America, 9200 miles. There is often much doubt about the true beginning and ending of a mountain chain, and judgments differ according as they rest on the fact of elevation or on the geological traces of upheaval where they begin to be manifest. Geographers are not agreed, for example, whether the Ural Mountains continue as far north as Nova Zembla, and whether one or two chains in America are to be spoken of as traversing the plateau of Mexico.

If there are parallel ranges, it is correct to speak of a transverse axis, running at right angles with the main axis. There is, it is apparent, a marked difference between simple chains and the accumulated parallel chains, where breadth is a prominent element, as in the Vosges, the Black Forest Mountains, the Fichtel range, the Hartz, the Ardennes. The parallel rows form a mountain system. Yet all great chains are made up of smaller ones, of groups at least, and so are mountain systems. Often the grouping is seemingly irregular, a lawless aggregation, but only because our knowledge is incomplete, and the law of arrangement concealed from us. This law is traced in the very geological qualities of the chain, not in the later form. The outer form is often very deceptive, the very convulsions which indicate the surer signs having served to obliterate what we should suppose the most prominent marks. The present of mountains must often be studied in the light of their past. Orography must be interpreted by geology. But the geological surveys of the earth are as yet very imperfect; the outer form has often to be accepted as the only guide. Orography and geology are two sciences which now go on hand in hand.

In the simple mountain chain it is easy to discriminate between the parts which make it up; the base is easily ascertainable and the ascent to the comb-like ridge is readily traced; the eye does not fail to see the relation between the special prominent heights and the chain from which they rise, and to trace the manner in which spurs and outlying mountains are connected with the main chain. Small isolated collections of mountains are especially valuable as elementary studies, for they always have a unity of their own. And all the greater and well-known chains are made up of smaller, simple chains, whose connection and mutual relations are, however, sometimes exceedingly difficult to trace. But the character of the whole is not sometimes ascertainable with this preliminary knowledge of the parts.

The true base of a mountain chain, the line of periphery, in consequence of the general unevenness of the adjacent country, must be ascertained by very exact measurements with the level. The geologist does not begin with this step, he strikes deeper, and seeks the place where the structure diverges from that of the more level land lying near; and, in the search after the basis of structure, he discovers the unity of the range from the foot to the summit. The whole geological district which has been upheaved into mountains, Leopold von Buch found to be generally ellipsoidal in form, the longer axis being far more prominent than the shorter one. The axis of most mountain chains is, then, the longer axis of an ellipsoid. The Swiss Alps display about a dozen such ellipsoids, of different characteristics, and arranged according to no perceptible law of harmony. Each is developed from its own base, as the trunk of a tree grows out of its root. These separate bases lie contiguously, but the peaks which shoot up are widely sundered. The forms of the mountain groups resulting from this are, of course, various. Some of them I will briefly characterize.

1. The longer axes of the subordinate chains may run in parallels, as in one portion of the Swiss Alps, the Jura, the Ural Mountains, the Mexican Cordilleras, and the Himalayas.

2. The chains may diverge or converge. The Alps diverge at the east, and the forks run northeast and southeast respectively; the Rocky Mountains, toward the Arctic regions, divide into from five to seven diverging chains. Converging ranges may come together at varying angles, and these can mass themselves into confused mountain knots, the summits of which soar to amazing heights, as the West and Middle Alps do around Mont Blanc. Alexander von Humboldt distinguishes five of these mountain knots in the Andes, Porco, Cuzco, Pasco, Assuay, and Los Pastos, whose construction, carefully studied, he considered, gives the key to the structure of the whole chain. Side chains often display this knotted form, as in Upper Peru around Lake Titicaca, the three branches of the Ural, at the Irmel Tau, the Himalaya, Kuenlun, and Hindoo Koosh chains, in upper Afghanistan, and the ranges of Swiss Alps, which converge around St. Gothard. Yet the convolutions which these mountain chains make at their point of convergence are never regular, never mathematically exact, but to be measured in sections, and the traces of a linear direction to be carefully sought with the compass. The whole has, to the eye, a labyrinthine appearance, and the law of structure is only ascertained, with exactness, by the geological features, the direction of the strata, and the like. The geographer must call in the geologist to help him solve his problems.[4]

3. If from some high central point the mountain ranges radiate in the form of a star, they form a new variety of system called, for convenience, by the name “star-shaped.” In volcanic mountains this configuration is common, as in Mont d’Or and in Auvergne. The southwestern Alps, known sometimes as the Sea Alps, the Ural at the Arctic Ocean, the Quito range of the Andes, are types of this form.

4. The ring-shaped system is in direct contrast with the last. It is found where mountain chains are arranged in a circle, inclosing a plateau of larger or smaller extent. There are two marked examples of this form in Europe: Bohemia and Transylvania. The ring of mountains around the former is made up of a number of ranges, which dovetail together at the ends, making a unit, but only a rude circle, speaking with mathematical exactness. The inclosed basin is only relatively a lowland; it is rigid with hills and low mountains, yet of such little importance, in comparison with the rim of peaks, that the common name, the “Bohemian Kettle,” has begun to have an accredited significance, and is stronger than the more loosely-used word Basin. Transylvania, too, partakes of similar characteristics. Its border consists of a number of minor ranges, of varying heights, up to 1800 feet; and the central hollow, which is much more strongly marked by hilly land than Bohemia, lies 2200 feet above the Adriatic. The ring-shaped system is one of the rarest met of all. They are, however, observed in abundance on the moon.

5. Just as rare is the form where ranges intersect in the form of a cross, those running, for example, from north to south, meeting those running east and west. As an instance of this, Humboldt cites the confluence of the Himalaya, the Kuenlun, the Hindoo Koosh, and the Belor or Belurtagh Mountains. The belt between 35° and 40° N. lat. is remarkable for its gridiron-shaped mountain system, the points of conjunction being marked by knots of peaks of colossal height. The most remarkable one of these is the lofty Pamir Pass, between 37° 30′ and 40° 5′ N. lat., and 18,000 feet high, known, historically, from the sixth century, and described by Marco Polo, as well as by the ancient Greek historians. The Persians dwelling in the neighborhood term it the Roof of the World. Elsewhere the same feature is observable, though on a scale of less magnitude. So in the Altai range at Lake Yetzkoi, in the western Swiss Alps, and in the porphyritic chain of Room-Elee, known to the ancients as Rhodope, and now as the Despoto Dagh. This gridiron-shape of some mountain systems seems to be the result of upheavals at different times, which necessarily occasions the most broken configuration at the point where a chain of more recent formation has been projected through one of older date.

The varying relations of length, breadth, direction, connection, and severance of mountain ranges give great diversity to them, and impart to every system a character of its own. To the features just indicated must be added vertical or precipitous descents, for the influences which they exert upon the possibility of man’s constructing mountain roads, are very great. The extent of these sudden depressions, or, more exactly, the relation which the distance from the base to the pass bears to the distance from the base to the summit, gives a key to the uses of certain mountains as adjuncts of civilization, and shows how some ranges rather than others may become the abode of men, and produce marked effects on human culture and the world’s history.

I have before alluded to the comb-like structure of most mountain chains. The resemblance is more striking than may appear; for not only do the peaks correspond in general uniformity of height with the teeth of the comb, but the equally uniform height of the passes from the base corresponds with the uniform thickness of the solid part of the comb. The relation, however, of the distance from the base to the passes, to the distance from the base to the peaks, is widely various. Humboldt has estimated it in a few leading chains as follows:—

Himalayas. Height of chain, 25,000 ft. ” pass, 15,000 ” ” base, 1000 ” (Delhi.)

Alps. Mont Blanc, 14,500 ft. Height of pass, 7200 ” ” base, 1200 ”

Andes. Chimborazo, 21,000 ft. Height of pass, 10,000 ” ” base, (Sea.)

Pyrenees. Maladetta, 10,722 ft. Height of pass, 8000 ” ” base, (Sea.)

In the Alps and Caucasus the relation of the height of the pass to the height of the chain is as 1 to 2; in the Himalaya, Quito Cordillera, and Alleghany Mountains, as 1 to 1·8; in the Pyrenees and Cordillera of Bolivia, as 1 to 1·5. In the Alps, therefore, where the pass is only half as elevated as the chain, the communication is the most direct, and the least barrier is put to the purposes of man,—a fact of great import in relation to human culture. The Pyrenees are in direct contrast in this respect, the most unapproachable, the most sundering of mountains.

The position of mountain chains is a matter of the first importance in relation to the welfare of man, and the solution of many of the most important problems in history. Whether interior ranges like the Ural and the Atlas, or ranges connecting two seas like the Caucasus, or those like the Mexican Sierras, lying between two oceans, are most open to human approach and use, is a question which we will not here stop to consider; but it may be said that, whether situated in the relations just indicated, or whether they are meridianal ranges like the Ural, the Scandinavian chain, the Alleghanies, or the great Cordillera of both Americas, which extends from the tropical world to both polar zones; or whether they run in the same direction with the parallels of latitude, turning one side to the colder north, and another side to the sunnier south; or whether they assume a diagonal direction like the Swiss Alps, from southwest to northeast, or like the Caucasus, from northwest to southeast, is a matter of the first importance to ascertain. Of not less consequence is it to discover whether the chain is the edge or rim of a plateau, and can have, therefore, only a one-sided development, like the Himalayas toward the south, or the Anti-Taurus toward the north, because the existence of a plateau on the reverse side dwarfs the slant distance, and gives but a fractional part of what, without the plateau, would be open and clear.

As plateaus usually display this edge on both sides, the border has been aptly compared to a double ledge or rim, between the two sides of which the table-land lies, often tolerably high above the sea level. If these rims, like mountains, are not contiguous to the plateau; if they are separated from it by a valley of greater or less width and depth, running parallel with the edge, they form what Humboldt has called natural circumvallations. Of such the Altai range, on the north side of the Asiatic central plateau, is an example. The hollow between the range and the plateau just mentioned is partly filled with inland seas. The Caucasus may, in like manner, be regarded as the circumvallation of the American plateau, separate from it by the Koor and the Aras (ancient Araxes) rims. Yet in the Caucasus another modification occurs—a partial linking of the plateau with the range at the west extremity, by the connecting chain of the Moschic Mountains. In like manner the Pyrenees, in their eastern half, form a circumvallation around the north side of the Castilian plateau, separated from it by the basin of the Ebro, and forming a perfect ring around Upper Castile and the elevated province of Biscay.

In cases where a mountain chain rests upon a plateau, rising up in the very heart of it, its summits seem to be not high, although the basis, the true foot of the chain, may not be at the level of the plateau, but far lower, and such mountains may, therefore, be of great absolute height. The name superimposed mountains has been given to them. Such are the Kuenlun and the Thian-Shan ranges of Central Asia, the Guadarrama chain between Old and New Castile, and the Rocky Mountains in North America. These superimposed ranges often run near to and parallel with the rim or edge of the plateau, and seem to give it more completeness and breadth.

The geologist employs the word “sutures” to designate such forms, because they serve to unite those parts of a plateau which are at different heights above the sea level. He regards the mountains as rising to fill enormous clefts which great convulsions have rent in the earth, and as passing up, while in their fluid state, to a height above the level of the plateau, and bridging over the abyss. In this way our mountains which rest on plateaus seem to have been formed, as indeed is indicated by their geological structure.

The smaller plateaus display analogies kindred to those seen in the larger superimposed mountain ranges. The extinguished volcanic group of Auvergne rests upon the central plateau of southern France, which, according to Remond, has an average elevation of 1000 feet. The now silent volcanic group of the northern Rhine broke through the moderately elevated gray-wacke formation of that locality, and is, therefore, a superimposed range.

Mountain chains which diverge from plateaus and their serrated rims seem, nevertheless, to have some relation to them, even though they cannot be considered continuations of them. The Lebanon chain, for instance, which turns away at a right angle from the Taurus range, and runs southward through Syria and Palestine; the Lutznetskia and the Alatau Mountains, mineral ranges running from the Altai northward to Tomsk; the Yablonoi and the Stanovoi Chrabet ranges running to the northeast; the still unknown or little known range of Farther India, traversing the whole peninsula of Malacca, come under this head.

Completely unlike the groups thus far considered, are the isolated mountain systems, with uniform slopes on all sides, and with a roof-like form, distinguishable to the base. The mountains of Europe are mostly of this class—the Ural, Carpathian, Scandinavian ranges, the Alps, Apennines, and, in part, the Pyrenees. They give rise to rivers, not on one side alone, as do the Himalayas and the Andes; they are rich in resources of all kinds for the student and the economist, and thus make up in part for their comparatively unimportant dimensions. Their double-sidedness gives them a large influence on civilization, since rivers flow from them in all directions; while from the Himalayas they only flow to the south, and from the Andes to the east.

Plateaus and mountains, different as they are in appearance and characteristics, yet constitute, in their mutual action and reaction, and in their forms of transition from the one to the other, the highland system of the globe. Their relations are inexhaustible as Nature herself. We cannot study them without profit; but we can never come to a perfect knowledge of them all.

The Relations of Plateau Systems.

Like mountain systems, plateaus are not to be estimated in respect to elevated and superficial area alone, but in respect to form and position as well.

The American plateaus are elongated from north to south, but are of disproportionate breadth from east to west. The Asiatic plateaus, on the contrary, are not only of great length, but also of great breadth. The Spanish plateau, that of the Atlas system, and that of Asia Minor have their length and breadth nearly equal.

The surface of plateaus is exceedingly varied. It sometimes assumes the aspect of elevated plains, sometimes of rolling land, sometimes of horizontal strata of naked rock, as in Patagonia and the western Sahara. In one place it displays sand-hills, as in parts of the Gobi Desert; in others barren steppes, as in portions of Persia. Sometimes we find a gradual ascent of minor plateaus or terraces; sometimes single mountains rising out of the plateaus, as does Demavend; sometimes we find a chain of colossal peaks emerging from the heart of a plateau, like Thian-Shan and Bogdo-Oola. Sometimes there are plateaus broken up into crags and patches of level ground, like Persia; sometimes plateaus with deep valleys or river basins, like the plateau of Yoorkistan and Gobi, including the River Tarim, and reaching its greatest depression at Lake Lop, or, like the plateau of Afghanistan, including the River Hirmend and Lake Zareh; again, we have plateaus traversed by water-courses which forced their way in times of flood, and leave in the rainless seasons the traces of the former violence. Such are some of the less elevated plateaus of France and Bavaria.

Especially important are the combinations and groupings of plateaus, as well as their relation to adjacent lowlands.

In Africa the plateau form embraces the larger southern half of the continent. Low plains are, on the contrary, the prevailing form in the north, broken, however, by the Sahara, and the high coast plateaus of the Atlas range, and of Barca.

In Asia there is a vast central plateau with gradual declivities toward the east, toward Yoorkistan and Persia on the west, and toward Lakes Baikal and Zaisan on the north. On the south the descent is abrupt to the Indian lowlands.

In Europe there are, for the most part, scattered and disconnected plateaus of small size and little elevation, often passing by an imperceptible gradation to the other forms. The Spanish plateau is, however, a marked exception, and has the sharply-defined character of the northern African plateaus. In eastern Europe the central situation of the isolated Valdai plateau, whose elevation is very moderate, but 840 to 1080 feet, is remarkable, and is of very great influence in determining the hydrographical character of the great Russian lowlands. And in fact, the hydrographical influence of both mountains and plateaus is so great, that it is worthy of careful and special study.

The combinating and grouping of plateaus in different continents give rise to great contrasts, observable most distinctly in Asia and America.

Asia, with all its great internal depression from Cashgar to Lake Lop, yet displays such immense districts of plateaus, all ranges of elevation, low, moderate, and very great, that the very grandeur and extent of its colossal mountain chains are subordinate in comparison. Asia is the land pre-eminently of plateaus.

America displays, not in its central but on its western coast, the greatest chain of mountains on the globe, flanked by plateaus of great elevation, but of superficial area quite out of proportion to the length of the mountain chain, and to the extent of the lowlands of both the northern and the southern divisions. And while in Africa the regions of depression are in the north, and in Asia around the great central plateau system, in the Americas, both North and South, they are thrown into the eastern portion.

Australia, in perfect contrast again, is, with the exception of its southeastern corner, a vast tract of unbroken lowland. No diversity is possible there, no change in the condition of life, but a ceaseless uniformity of monotonous but prodigal gifts.

Is not the imposing grandeur of these harmonious, provisional arrangements for the use of man calculated to fill the soul with admiring wonder, and to lead us to suspect, above all this display of cause and effect, above all this working out of a manifestly preconceived plan, the existence of a great and active Being, who has planned and executed it all with higher ends and a loftier purpose than to satisfy the mere earthly life of man?

Primeval Formation of Plateaus and Mountains.

To enter upon a discussion of the manner in which plateaus and mountains were formed, would make it necessary to resort to such judgments as we could draw from their external appearance and their internal structure. The rapid progress of geology does indeed afford us many probabilities thoroughly grounded. A few of these may have been briefly indicated in connection with some elevated regions, where the massiveness is striking, and where the axis of elevation is prolonged to a considerable extent. In such cases the influence exerted on the world is more evident than it could be elsewhere.

_Origin of Plateaus._

Alexander von Humboldt has employed the term Intumescence, to indicate the manner in which plateaus have been upheaved. Plateaus appear as long, often wide, mostly level, sometimes rolling, sometimes hilly elevations, presenting an appearance as if the earth had swelled with confined gases, and with depressions here and there as if, in the casting of the molten mass within, a natural external subsidence had followed. They have, therefore, viewed in their internal structure, an unbroken wholeness, and are free from those vast fissures which characterize mountains, rending the earth for hundreds of feet down. The utmost want of uniformity is seen in the gradual depressions which often harbor the large internal lakes found in great plateaus. Varied as they are in configuration, they always retain marks enough to indicate that they owe their upheaval to steady, gentle, and not tumultuous forces within, exerted at the time of the primeval cooling of the earth’s crust; in contrast, therefore, with mountains, which were thrust up from beneath, through huge seams made by the bursting through of pent-up vapor and gases. These elevations of the earth’s crust, whether in the form of mountain or plateau, must correspond, in order that the symmetry of the globe may be preserved, to the depressions found in lowlands and beneath the water of oceans and seas.

It is observable that the great plateau upheaval of the Old World has taken the shape of a belt, which runs in a northeasterly direction along its whole southeastern shore, crossing the equator at an angle of 45°, broken, however, at some places, but never so much as to destroy the coherence of the belt. The diagonal of the rhomboidal plateau of eastern Asia, passing due northeast through the table-land of Thibet, indicates the direction of the whole band of highlands. This band drops toward the south in uniformly steep declivities; while toward the north it falls away with gradual steps of transition, reaching at length the regions of the greatest depression—Libya, northern Arabia, the Caspian, Siberia, and, at last, the low regions around the north pole.

In this belt or chaplet of plateaus lie the high table-lands of South and Northeast Africa, Abyssinia, South Arabia, Persia, Beloochistan, North Deccan, Afghanistan, Thibet, East Tangut, and eastern Gobi, in Mantchooria.

Correspondent with this immense plateau belt, in the New World, is the great American chain, once a wholly volcanic, and though differing so much in structure, direction, and hydrographical influence, yet giving the globe a wholeness, a unity in diversity, which is strikingly apparent.

_The Origin of Mountains._

The linear regions of elevations of the earth’s surface, as we may term them, in contradistinction to the plateaus which are characterized by breadth rather than by length, have been projected in the form of mountain chains, as has been already hinted, through huge fissures made by the rending of the earth’s crust. The upheaval to fill the seam has, in some cases, been all made at once; in others, in a succession of periods. The uniform agreement of all the geological strata or their diversity decides this point. Sometimes the rocky strata are laid bare and easily investigated. Often, however, the observer is obliged to draw conclusions from a part to the whole. Yet in all cases the mountain, in contradistinction to the adjacent plateau, is the tract which has been thrust through the crust. The frequent steep and lofty precipices show the immensity of the internal force required to lift the mountains from their places, while the lines of stratification indicate the direction of upheaval. The rifting of a seam in the earth’s crust was the first step in the formation of mountains; the filling up of the seam by liquid matter, the second step. The upheaval of Asia, from the Persian plateau to Gobi, in a line 60° N. E., seems to be connected with the most ancient revolution which the earth’s crust ever experienced. The mountains there are, therefore, more modern in origin than the plateau on which they stand. The direction of the chain, in all cases, seems to have been dependent on the direction of the fissure in the earth’s crust, which the mountain range afterward fills. The breaking through the crust necessarily occurred when the pressure beneath the surface was very great, or when a moderate pressure was exerted beneath a thin crust, where the resistance was slight.

The latter case seems to have been prevalent in most plateau regions. Their own gradual upheaval probably thinned the surface, and made it more liable to fracture. This accounts for the fact that the greatest mountains of the globe are found contiguous to plateaus. And the broader the original seam in the crust was, the broader the mountain range which rose to fill it, either at a single upheaval, or in a series of convulsive throes projecting successive masses of molten matter from below. In the latter cases the strata thus formed lie on each other like the leaves of a book, their constitution changing according as the more advanced stages of melting in the vast internal caldron throw out more metamorphosed rocks. These later layers rose to a greater or less height on the sides of the partially-formed mountain, according to their specific gravity, their more or less fluid state, and their rapidity of cooling, as we can now see by examining the layers in their present permanent condition.

Thus far we can conjecture, with great security, taught by the manifestly wild and fierce convulsions which once threw up the mountains, since in them distortion is the rule and regularity of structure the exception, and also by the equally manifest quiet and sustained process of upheaval, when the plateaus were formed; their strata being in a state of regularity and unbroken repose.

When the great vents produced by the outward pressure of internal volcanic forces occurred beneath the sea, they were filled up in the same manner as on the dry land, excepting that the summits of the mountains emerge above the surface in the form of isolated islands, or when there was a chain or group of mountains upheaved, as an archipelago. When there was no rifting of the surface, and no forcing up of whole chains of peaks through a thinned crust, the fierce action of the internal heat appears to have necessitated the upheaval of solitary volcanoes here and there, in some cases even rows of them, to give vent to the pent-up steam and gases, and to convey away the molten tide within. When such volcanic series rose in parallel ranges, they lifted, or may have lifted up the whole district between them, as if upon their shoulders, and so formed the American type of plateaus, of less breadth and greater length than the Asiatic, and in height corresponding with the volcanic peaks which form their rim, and to which they are probably indebted for the form of their structure.

It needs hardly to be added to what has been said above, that the general direction of existing mountain chains depends upon the direction of the primitive seams made in the earth’s surface by internal forces. The Ural Mountains, the Scandinavian chain, the Alleghanies, the Ghauts, run on meridian lines; others more or less transversely.

The various kinds of rock which have been thrown up in mountains enlighten us as to the process and results of the internal heat of the earth; the successive formations display not only the various eruptions of molten matter, and its discharge in new layers above what had been thrown out before, but reveal the relative age of the various formations. We have in a single chain sometimes a whole volume of history, marking off the epochs of upheaval with the most perfect legibility and exactness. Many crystallised rocks result evidently from the gradual process of cooling after the ancient exposure to the intense heat of the inner portions of the earth—granite, porphyry, gneiss, slates, and the so-called metamorphosed rocks. These used to be considered the oldest formations, but the upheaval theory treats them as the latest formed.

Most mountain chains have been uplifted to their present height by a succession of upheavals. To accomplish this has been labor of uncounted thousands of years. Only a very few—the main Carpathian range, for instance—seem to have been upheaved at a single convulsion, and to have assumed their present appearance at once. Where there were incessant eruptions accompanied with flames, and masses of molten matter (lava) have been ejected from the crest or from single summits, these volcanoes and volcanic ranges have been the result. Elsewhere no such phenomena have been visible. Possibly, in such cases, the masses cooled so rapidly as to extinguish or fill up what may have been embryo craters, and the plutonic acclivities may have been repressed, leaving us the traces of primeval eruptions, but no vestiges of any dangerous forces remaining till now. Of mountains formed in this manner, may be mentioned the Puys de Dome, the Bohemian basaltic peaks, trachyte Transylvania Alps, the Katak Kaumene, (“Burnt Tract,”) of Asia Minor, and Hauran, Iceland, parts of the great American chain, parts of the Sunda chain, the South Sea Islands, and Bagdoola, and its range of extinct volcanoes in the Thian-Shan chain.

But other forces besides fire were competent to form mountains and plateaus, to spread layers of clay and sand and various deposits at the bottom of the sea, afterward to harden into strata of rock. In contradistinction to plutonic formations, these have been called neptunic, because formed at the bottom of the sea. The oldest of the neptunic or stratified rocks have been upheaved by the subterranean forces, and now are found in the elevated plateaus or mountain ranges, still having, however, their unbroken irregularity of structure. Also, after the stratification has been complete, and plutonic acclivities have opened the seams in the earth of which I have already spoken, and molten masses have rushed up to fill them, fragments of the primitive stratified rocks have been caught up and raised, together with the molten masses, to the very summits of lofty mountains; so that the geologist finds fossils there more or less perfectly preserved, the stratified rocks which contain them surrounded by the plutonic rock upheaved from below the surface. Chalk layers full of mollusca and infusoria have been found by Humboldt and von Buch on the very summits of the Andes, and corresponding with those which have been discovered by Ehrenburg in the deposits at the bottom of the sea.

Other older and more recent oceanic deposits are found in their primitive condition at the bottom of the sea, or in very low places on the land. In such localities the surface of the earth is composed of horizontal or slightly inclined layers or strata, of secondary formation, and whose origin in deposits from water cannot be denied. These are the beds of chalk, clay, sand, marl, gypsum, and other common substances; and these strata again have been overlaid with more recent accumulations, the result of diluvium or alluvium, continuing even up to the present time.[5]

Lowlands.

This variety of the earth’s surface stands in the strongest contrast with mountain regions, or, in one word, with the highland form in all its modifications. The name lowland we apply to all those broad tracts which do not rise more than four hundred feet above the level of the sea. The absolute elevation is determined from a section drawn vertically from the superior surface to the plane of the sea. Every comparison by numbers of one lowland plain with its more elevated surroundings gives only a relative result, as for instance, in comparing the valleys of one chain of mountains with those of a more lofty chain. Such relative lowlands may lie at a great elevation above the sea, as the vale of Chamouni, for example, at the north foot of Mont Blanc, is 3000 feet above the ocean level. Both conceptions of the word lowland, which is common to elevated plains as well as those at the sea’s margin, are entirely different, and should be kept distinct, although they are very often confounded.

We are to deal here only with the absolute, great, and generally diffused lowlands, in contrast with which the elevated valleys and plains just referred to may be considered as mountain table-lands and the rims of plateaus.

We assume, as we did in judging of the two grades of plateaus, an arbitrary standard of measurement, and limit the rise of real lowlands to an altitude of 500 feet above the level of the sea. Great tracts of running plain, rising by so slight a grade as to be almost imperceptible, can be regarded only relatively as lowland, and, in a strict sense, belong to those regions of transition which fall more truly within the domain of highland or plateau. The word plain indicates the opposite of hill or mountain, but has nothing to do with the greater or less degree of absolute elevation, although it is often used as if it had.

The lower limits of lowlands are sharply defined enough. They are the margin of the sea, toward which the slope usually becomes almost imperceptibly small. Often the expression is used, yet not quite fitly, that the lowland extends into the sea for some distance, and is found beneath the surface. Strictly this is the bottom of the sea, and does not fall under consideration in this connection.

Many lowland plains rise so slightly above the sea level, that they are not unfrequently submerged, and, in many cases, owe their existence to repeated overflows. They are the basins of old gulfs, as in the very slightly elevated plains of Caracas, whose whole shore is open to the influences of the great Atlantic current flowing from east to west; or, as in the great Lombardy plain, which slopes at the same almost imperceptible degree toward the Adriatic. There are also some lowlands found in the interior of continents, and these, too, sinking below the level of the sea; but they are altogether exceptional, and only met with in two or three instances. They are called, by an accommodation of an algebraic term, _negative_ lowlands. To them belong the region around the Caspian and the Aral Seas, and the much smaller tract comprising the Dead Sea, and forming the Jordan valley; besides, there is the Suez steppe, inclosing the bitter lakes between Asia and Africa; and possibly the Beled-el-Jereed, in the western part of the Sahara and the central part of Australia.

To these it might not be incorrect to join those partial lowlands which have been rescued by human efforts from the sea; the marshes, for instance, behind the dikes of Holland, Sleswick, East Friesland, and at the mouths of the Vistula, the Weser, the Nile, the Ganges, and other rivers.

The most extensive lowlands in the world are probably those which embrace Siberia, in Asia, and the Canadian and polar region of North America. Many great tracts, entirely inland, are in those flat districts covered by sea-water which was once driven in by great storms, and now lies stagnant, resulting in inapproachable swamps and morasses. Yet, under the equator, there are immense lowlands, as, for instance, in the eastern Sahara, although this region is broken by strips of plateau, and is by no means that uniform lowland plain which it used to be regarded. Northern Australia belongs to the same category, and also those immense plains which reach from the Atlantic so far into the interior of Brazil, along the lower Amazon. By the time, however, that they reach the middle course of that river, they have acquired, though in such imperceptible steps, a considerable degree of elevation, according to Humboldt’s barometrical observations, and not reckoning certain limestone hills found there, from 1050 to 1200 feet. The plains of the middle Marañon are, therefore, true plains, but not absolute lowlands, and not to be identified with the great flat region at the mouth of the river, and in comparison with the real lowlands of Venezuela, which do not rise over 200 feet above the sea, and genuine plateau, which, level as it is and broad as it is, is far more elevated than the Valdai plateau, in Russia.

Almost all great river mouths are true lowlands—the Egyptian delta, the delta of the Ganges and the Indus, for instance, (the two latter being separated by the very moderate plateau (100 feet) between Delhi and Mooltan;) to these we may add the delta of the Euphrates, the east shore of China, between the Blue and the Yellow Rivers, and Senegambia, between the Senegal and the Gambia. And in America, the same thing occurs in the Mississippi, Orinoco, Amazon, and La Plata, where the immense mass of water which they send to the sea passes through lowlands of very great extent. In the Mississippi they extend from the mouth as far north as the confluence of the Missouri and the Mississippi, where stands St. Louis, not 500 feet above the level of the sea. The prairies west of the lower course of the river rise rapidly, though imperceptibly to the eye, to the high terraces of Kansas, at Council Grove, varying from 1500 to 2000 feet absolute elevation, and then more rapidly toward the west, to mountain plains or plateaus, from 3000 to 6000 feet high. These, of course, lose the distinctive character of lowland.

The mouth of the St. Lawrence is, in some respects, analogous. Lowlands accompany it for a great distance from the sea; at Lake Ontario the elevation is only 232 feet, at Lake Erie only 565 feet. Yet the level tract is narrowed down to a mere border, and does not widen into great lowland plains. The contracted region of low country along the St. Lawrence is broken up, too, by rocky heights and rib-like ledges, whose absolute height, however, is not to be confounded with the elevation of the plain which they traverse.

In entire contrast are the broad plains of South America, which lie along the course of the Orinoco, La Plata, and Amazon, the so-called pampas and savannas, which extend a great distance into the interior, farther, indeed, than investigators have yet thoroughly prosecuted their researches. In no continent are the distinctions between highland and lowland so sharply drawn as in America. The lowland plains occupy four-fifths of all the country east of the Andes, in South America: only one-fifth is highland; for, notwithstanding the extent of low plateaus and diminutive mountains scattered through these great plains, yet their entire amount is inconsiderable, compared with the immense lowland tracts of that continent. America has fitly been called the region of the greatest depression on the globe, because this is the prevailing characteristic of its whole eastern side, lowlands forming two-thirds of all America, and highlands only one-third.

In Asia, the later hypsometrical observations have shown that the lowlands are by no means so extensive as they were formerly supposed. The highland extends, according to von Middendorf, much farther northeast of the Yenisei, toward the northern limit of Siberia and Tschatschi, than was formerly supposed; and the Siberian plain extending westward to the Ural Mountains is narrowed down from 4,079,970 to 2,233,800 square miles. Yet this lowland comprises, including central Bokhara or Toorkistan, 1,051,200 square miles, and other low Asiatic plains 1,314,000, the enormous area of 4,599,000, or more than twice the extent of Europe, leaving 9,636,000 square miles for the highlands.

In Africa there are almost no lowlands to speak of, excepting the districts around the mouths of the great rivers indicated a few pages back. To all equatorial Africa this physical feature is entirely wanting. In the north, where the whole Sahara was formerly thought to be one vast low plain, there are now known to be the moderate plateaus already indicated. The area of true lowland is, therefore, sensibly diminished. Vogel’s barometrical observations have already shown us that the country around Lake Tchad is about 1200 feet above the sea; the surface of Lake Tchad is 850 feet above the ocean level, and the lower limit of that region does not, therefore, come within the range already set as the point where lowlands become highlands.

In Australia the lowland seems to be the prevailing physical form, although here and there exceptions to it occur.

In Europe there are three great lowland plains to be specially mentioned. The greatest, that of middle Europe, embraces the shores of the North Sea and the Baltic far inland, and extend the farthest to the southeast. A second, hardly of less extensive proportions, comprises all northern Russia as far as the White Sea and the Arctic. It embraces but one-third of the great polar plain, and is really one with the region beyond the Ural chain. The third is the region around the Black and Caspian Seas.

The Middle European Lowlands.

The Germanic-Sarmatia-Russian plain extends, without a break, from the mouths of the Rhine, through all central Europe, to the middle Volga and the Ural. It is pre-eminently a region of lowlands, without any elevations of importance, and having no change of level, except very gently undulating swells, and on the north and south margin plateaus which very seldom rise over 500 feet. It begins with the deltas of the Rhine and the Scheldt, in Holland, passes through Lower Westphalia, Lower Saxony, the Marks, Lower Silesia, Lower Gallicia, and Poland, as far as the upper Dnieper and the middle Volga. It extends up the Rhine as far as Strasbourg, 474 feet above the sea, up the Weser as far as Cassel, 486 feet, and up the Elbe as far as Dresden, 280 feet.

The true Rhine delta may be defined as lying between Amsterdam, on the sea, and Dusseldorf, 107 feet above the sea level. Then passing by the broken and romantic tract lying between Dusseldorf or Cologne and Mayence, we come to the true Rhenish lowland, 240 feet above the sea. Munster is 400 feet above the ocean level. East of the Weser is the Lüneburg Heath, which advances in elevation, as we go toward the Elbe and the Havel, to 300 or 400 feet. Brunswick lies at an altitude of 200 feet; Magdeburg, of 128 feet. The height gradually increases; at Wittenburg it reaches 204 feet; at Dresden 280 feet, where the Elbe issues from the highlands; and in Lower Silesia we find Breslau, 375 feet above the sea, and its observatory, standing on the hills around the city, at a height of 453 feet, which seems to be the highest point in the whole vast tract.

Between the Rhine delta and the now dry basin of Paderborn, from the Ems to the Weser, Aller, and middle Elbe, is the mountain tract of the Hartz, (with the Brocken at the north, 3500 feet high,) running up as far as 52½° N. lat. By this natural feature the breadth of the great plain is considerably curtailed. As it is also more to the east of the Leipsic basin, from which the Mulde, Elbe, and Elster flow, by the hill country of Lausatia and North Silesia, with the Riesengeberge, (Giant Mountains,) 5000 feet high, which extends northward as far as 51° N. lat.

A third basin is in the Silesian, from which the Oder flows toward the northwest, and enters the southern limits of the great plain near Oppeln and Brieg. A third tract of hill country lies on the east bank of the Oder, and extends to the middle Vistula, the Tarnowitz Heights, in Upper Silesia, about 1000 feet in altitude. The plateau north of the Carpathian range, on which Cracow lies, is 669 feet above the sea; and the most northern hill group of Kielce, between the Pilica and the Vistula, rises in the Kreutzberg to a height of 1920 feet, and in St. Catherine to 2000 feet.

The great lowland advances eastward, with always diminishing breadth from north to south, over the extensive plains of the middle Vistula, at Warsaw, 330 feet above the sea; over the Lithuanian morasses of the Bug; over the Sarmatian district of Minsk and Pinsk as far as Kiev, on the middle Dnieper, at the southeast, and as far as Orsha and Smolensk, at the northeast. Pinsk, in the middle of this tract, lies about 400 feet above the sea. The north side of the plain is bounded by the very moderate plateau south of the Valdai hills, at Smolensk, 792 feet high; at Osmana, southeast of Minsk, 882 feet. On the south side it is bounded by the equally moderate plateau of Wolhynia and Podolia, whose absolute altitude is yet undetermined, but which, at the source of the Bug, is about 1000 feet.

This is the great Lithuan-Sarmatian plain, which, east of the Dnieper, is transformed into the central Russian lowland, at whose middle point is Moscow, whose exact elevation above the sea is between 300 and 400 feet; at Kazan, on the Volga, the height above the ocean level is but 270 feet, measuring from the highest point on the banks. Southward, the plain reaches to Simbeersk, 181 feet in altitude. The maximum breadth of this whole vast lowland tract is about 500 miles; the distance between Smolensk and Kiev, and the distance from the central point of the great Russian section to any sea, is between 500 and 600 miles.

The Origin of the Great Central European Plain.

The slight elevation of the lowland just described, rising but very little above the sea level, bears, throughout the most of its extent between the dunes of the north and the hill chains of the south, the character of a formation rescued from the domain of the sea within the very latest geological periods. The almost unbroken uniformity of the surface from the Scheldt to the Volga, about 2500 miles, confirms the character which its geological structure indicates. The deposition of disconnected, superimposed layers, running to a great depth, is exactly similar to that which we know results from the action now going on at the bottom of shallow seas. And in the great central European plain there is no sharply-defined geological limit met at the border of the North and the Baltic Seas. The same features extend beneath the surface of both of those seas. This whole lowland is, therefore, to be regarded as an immense basin, now dry, but once the bottom of a great sea,—an extension of the seas which now form a part of its northern border. The old coasts are now seen far inland. Wherever this coast-line changed its course, the whole landscape now alters its appearance; and yet more striking than the external view is the internal constitution of the soil. Masses of stone, standing out in full view, reveal the inner structure of what lies concealed. And these rocky projections are precisely analogous to the jagged outlines of our present bold sea-shores. The land is not cut up by inlets hollowed out by the action of waves and currents to a considerable depth, yet traces of such movements, and of the physical formations effected by them, are found. Promontories and islands are now found in plateaus, and hills encompassing dry basins. To the latter belong the intervale of the Rhine, and the basins of Paderborn, Leipsic, and Silesia. To the former belong the hills and plateaus of Middle Germany; of the Westphalian Mark, from Elberfeld to Dortmund, or, as might be said, from the Ruhr to the Lippe; the Yeutoburg Forest to the Weser; then the Weser Mountains, and the Hartz to the middle Elbe; the Thuringian Forest and the Ertz Mountains around the Leipsic basin to the upper Elbe; the Lausatian Mountains and the Riesengeberge to the Glatz Mountains, on the upper Oder; the Trebnitz Heights of Silesia, and the lower plateaus of the Fore Carpathian range, embracing Cracow as far as the hills of Kielce and the confluence of the Sau with the Vistula. Along the southern border of the ever-broadening plain are the plateaus of Gallicia, about 1000 feet in height, of Wolhynia and Podolia, and then less elevated plateaus, till we reach the Dnieper.

The geological character of the border of the sea which once covered what is now central Europe, is full of interest, because from it can be deduced all that we can know of the history of those great changes.[6] But we must pass over this, and only indicate the geographical configuration of the dry basin as it exists now, and forms the great Germanic-Sarmatia-Russian plain.

In the course of previous remarks on the lowest range of plateaus, I have remarked, that along the south coast of the Baltic the moderately elevated hill chains of Pomerania and of Old Prussia separated the true coast with its lowland from the great interior plain, forming a barrier, averaging about 300 feet in height, with here and there a form which runs hard upon the lower limit of plateaus of the second class; at any rate, a transition from between the lowland and the plateau.

It may here be remarked that the long, low chains, made up mainly of loose sand and other mixed and uncombined materials, and running along the southern border of that long, low band which skirts the Baltic, seem to be dunes once running along the shore of a sea which has now receded many miles to the north. In the deep channels and old inlets now dry, as for instance in the great break through which the Vistula passes below Thorn, only loose breccia, and no united layers of stone, appear. Yet this does not seem to be the case everywhere, although in the Cis-Ural and Baltic depressions dune-like ridges are to be found, some of them rising to a height much greater than was formerly suspected. These, it is true, are scattered, and only partially prevalent, but here and there they ascend to an altitude of nearly 1000 feet. At the eastern end of the great Pomeranian sea-plain west of Dantzic, and between that city and Bütow, where the sand ridge, which formed the ancient shore-line, runs very far to the north, there are a number of villages 400 feet above the sea. The Lower Mountain, (Thurmberg,) 54° 13′ 29″ N. lat., rises to a height of 1024 feet; the hill near Upper Buschkau, east of the Thurmberg, is 814 feet high; the hill near Hulterfeld, 846 feet; and the Höckerberg, near Schönberg, 902 feet.

Of the Thurmberg, Humboldt remarks that it is the most remarkable elevation between the Hartz and the Ural Mountains, and that but a few points in the Valdai range can be brought into comparison with it. Its position close by the sea is especially noteworthy. It is very probable, according to Humboldt’s opinion, that those inequalities of surface, formed of sand once partly or wholly submerged,—found in Mecklenberg, Pomerania, East Prussia Proper,—and now divided into flats and hill ranges, do not belong to the dune system of the ancient shore-line, but have the reason of their existence in ordinary upheaval; in the formation of limestone, and of the usual Jurassic rocks, which, afterward, have been covered with sand and other loose materials. The peculiar accumulation of genuine marine fossils indicates the existence of upheaved rocks below the upper layer of sand.

It is these elevations which in the constantly advancing ridge or ridges run northeasterly, and take the form of plateaus, increasing in breadth from the water-shed north of Smolensk, and the source of the Dnieper, in the Valdai Forest, and the western Uwalli, and which are found between the Volga and the Dwiner, and thence run eastward as far as Perm, on the Kama. They form the line of demarkation between the great Central European plain and the North Russian lowland, which extends as far up as the Arctic. This easterly chain, so far as it has been measured, seems to be less in altitude than the Valdai hills, which are about 1000 feet high. In East Prussia Proper and Livonia there are elevations of more than 600 feet; about 55 miles south of Dorpat Munnamäggi, the point of culmination, according to Struve, is 996 feet above the sea; south of Vilna the heights of Puzewitch reach an elevation of 990 feet.

In the same direction, still northeast, runs the Valdai, forming the source of a number of large streams and the great water-shed of eastern Europe. On the road from St. Petersburg to Moscow, Humboldt found the altitude at Norwaja Ijetza 660 feet, and the highest point at Popowa Gora 792 feet, (according to Pausner, 876 feet.) One point going south from the Valdai, at Mosti Derewna, the latter naturalist has ascertained to be 1032 feet above the sea; and the highest point in the range is, according to Helmersen, 1098 feet. Still further eastward, between the Valdai hills and the lake region between Lake Seligher and Bielo Ozero, the range of uplands, known as Uwalli, running northwesterly, intersected by numerous canals, and forming the water-shed of a number of rivers, gradually diminishes in height, but, still advancing eastward, it rises again, in the neighborhood of Perm and the Kama, to 1014 feet,—about the elevation of the Valdai range. Uwalli is only the Sclavic name of such hills as those whose absolute height is insignificant, but which, crossing as they do the great plains of Poland, Lithuania, and Russia, were formerly confounded with mountain ranges, and were so represented on the maps. They have, of course, great hydrographical value, and play a leading part as the water-shed of eastern Europe.

The Ponto-Caspian Plain, the Great Depression of the Old World.

This second vast lowland is the direct continuation of the central European lowland, with a decided sinking toward the Black and the Caspian Seas, indicated by the course of the rivers of that region. It extends from the month of the Danube over the lower Dniester, Bog, Dnieper, Don, and Volga, as far eastward as the Sea of Aral. To the last named the Siberian plain gradually declines. The southern plain of Europe stands in unbroken connection, so far as its formation is concerned, with the West Siberian plain, (2,213,400 square miles in extent,) and is, therefore, one of the most extensive lowlands on the globe. The Baltic-Sarmatian plain is separated from the West Siberian merely by the long Ural chain, (from 50° to 67° N. lat.,) whose elevation is only from 4000 to 5000 feet, and whose breadth is unimportant. Take away the Ural, and a continuous line could be drawn from Breda, near the confluence of the Meuse, Rhine, and Scheldt, across Europe and Asia, following the line of 50° N. lat as far as the Chinese frontier, passing over a continuous series of low, insignificant hills, heathlands, and steppes, and traversing a space estimated by Humboldt to be three times the length of the Amazon!

Toward the south, the Cis-Ural, European side of the Ponto-Caspian lowland, is separated from the Black Sea by a ridge of granite knolls, which passes from Volhynia and Podolia eastward as far as the cataracts of the Dnieper, and thence southeast, with diminished breadth, reaching its limit at Taganrog, on the lower Don, and the Sea of Azof. This ridge separates the narrow steppes of the northern shore of the Black Sea from the lowland of South Russia, the fruitful district of Ukraine. The height of these hills in the west, where they appear to have the greatest elevation, has been estimated to be about 1000 feet above the sea. Toward the Dnieper they have not yet been carefully measured; but probably there they do not rise above 700 feet.

The small sand steppe south of these granite hills runs from the Crimea eastward as far as the North Caucasian steppe, between the Don, Volga, and the Caspian, and indeed may be traced to the northeast as far as the Bashkiric-Ural chain. Lakes of marked saltness are found there: Elton, for instance, which lies 24 feet above the sea; while farther eastward they are found, as for example on the Kamysh and at Samara at a depression of—138 feet, 60 feet below the level of the Caspian Sea. Yet this lacks confirmation.

From this lowland, only a few elevations arise, and these of insignificant absolute height; yet, on account of the extreme uniformity of the whole country, they are objects of amazement to the whole steppe world. The Little Bogdo, south of Lake Elton, and yet farther south, Great Bogdo, 504 feet above the sea, according to Humboldt, and Mount Arsargar, 331 feet in absolute height, according to Murchison, are the only important hills. The Great Bogdo is composed of calcareous limestone and of sandstone, with rich deposits of salt.

The Kirgheez steppe separates, by a plain of very moderate elevation, the north Siberian lowland from the Caspian-Ural depression. It was formerly supposed, and indeed represented on the map, that a mountain range passes through this district from the Ural chain to the Altai. The Kirgheez steppe appears to range from 780 to 960 feet in elevation; while the Siberian plain is but 280 feet above the sea at Omsk, 192 feet at Tora, and 108 feet at Tobolsk. It has been considered by some that the Kirgheez steppe, as well as the granite hills of southern Russia, belong to an undeveloped system of mountains, an early cooling having solidified them before reaching the elevation which they would have attained; and that they partake of the direction which analogy would teach us such a chain would have, from northeast to southwest, parallel with the Carpathian and the Caucasus ranges.

The great depression of the Old World begins with the deepening of the Volga basin below Simbeersk; and at the place (51¾° N. lat., near Orenboorg and Saratov) where it breaks through the last row of hills in the Obstshei-Syrtis, it commences a rapid descent toward the Caspian and the Aral Seas. This great concavity, on the confines of Europe and Asia, at the center of the greatest land-mass, and far removed from any ocean, is remarkable as having no parallel on the globe. Humboldt remarks that perhaps a similar phenomenon would be repeated at the interior of other continents, if the tertiary formation and the parts found by marine deposit did not exist. It would be profitable to follow out so weighty a thought, with the surface as it now is.

The Obstshei-Syrtis is the moderate range of hills which runs westward in two branches from the Bashkiric-Ural, at Orenboorg, the northern spur running by Uralsk and the Ural River; the southern by Samara, rising on the east shore of the Volga to a height of 600 feet, and ending at Sarepta.

Orenboorg, on the Obstshei-Syrtis, where it leaves the Ural chain, is 255 feet above the sea. Uralsk lies somewhat lower, being 234 feet above the sea. The surface of the Volga, where it breaks through the high banks of Saratov, is only 36 feet above the ocean level; while the western shore, above Saratov, is 562 feet in height. Farther down the river, Sarepta lies 30 feet below the sea level; and there is, therefore, between Saratov and Sarepta, a distance of about 180 miles, a fall of 66 feet. West of the Volga, and following the river, is the continuation of the Obstshei-Syrtis, ranging in elevation from 562 feet down to 168 feet. At Sarepta, the low hills which thus far have skirted the Volga turn to the southwest, to the Manitsh steppe, sinking to an elevation of but 75 feet, and extending as far as the Sea of Azof. At Sarepta, too, the Volga turns from its normal southerly course, and strikes southeasterly across the Astracan steppe, entering the Caspian at the City of Astracan, 72 feet below the level of the sea. The level of the sea is 4 feet below the shore on which Astracan is built.

The old statements that the level of the Caspian is 300 feet below the ocean, rested solely on conjectures made by the naturalist Pallas. The influence of this great depression on the warmer climate of that region, the peculiar vegetation of the salt steppes, and the salt morasses which exist where the land is perfectly level, as well as the great beds of oyster-shells and other crustaceous remains, led him to the hypothesis that the whole neighboring district is the dry and deserted bed of a former sea, now shrunk to the comparatively insignificant dimensions of the Caspian. The broken line of bold bluffs which bounds the Obstshei-Syrtis on the south seemed to him to be the northern boundary of this inland sea, into which the Volga entered below the pass of Kamyschin and Saratov. Parrot and Engelhardt supposed that their barometrical elevations in 1811 confirmed Pallas’ theory, that the Caspian lies 300 feet below the ocean. Many hypotheses were based upon their observations; but the whole were at length brought into discredit by Humboldt, who distrusted the accuracy of instruments made at that time. Nothing but a trigonometrical survey from Taganrog to Astracan could give conclusive results, and this was accomplished in 1837, under the auspices of the Russian government. The result proved that, so far from being 300 or 350 feet below the ocean, the Caspian is not 100 feet. Its depression, as already stated, is about 76 feet.

The level of the Aral Sea, which is evidently closely linked to the Caspian, has not yet been determined with absolute certainty. Barometrical observations were instituted for this end by the expedition under General Berg, which explored that region in the winter of 1826, but the cold was severe, and the results are questionable. The result of their investigations was, however, that the surface of the Aral lies 110 feet higher than that of the Caspian. This would make the Aral to be 34 feet above the sea level. More careful inquiries may, however, determine the level of the two seas to be the same; but at present we have to be content with the results of the expedition referred to, and accept its elevation as 34 feet above the level of the ocean.

Without, however, going into details respecting the Aral, the region around the Caspian and directly connected with it, which is below the ocean level, embraces an area of not less than 131,400 square miles. This survey extends from the Volga to the Ural River, thence to the Emba and the northernmost point of the Sea of Aral, and thence to the salt lakes of Aksakal-Barbi, lying to the northeast of this sea. The tracing of this line from the higher to the lower stages of depression gives clear indications, in the nature of the soil, of the existence of a great sea once occupying that whole tract.

Thus much for the configuration of the Caspian lowland. If to these 131,400 square miles be added the 153,000, or, according to Humboldt, 164,000 square miles of the Caspian itself, the entire depression embraces almost 318,000 square miles, and is greater than France, greater than Germany, and only to be compared with the whole Austrian empire! If to this great region be added the district around the Aral, which sea alone covers nearly 25,000 square miles, and then to this the yet unmeasured surface covered by seas yet to the eastward, the entire region of depression is immensely increased. And then if to this be added the great Siberian plain, whose level is not greatly above the sea, the combined district would be at least once and a half as great as all Europe.

The Origin of the Ponto-Caspian Depression.

Thinking of the immense extent of this depressed region, whose entire surface occupies no inconsiderable fraction of the interior of the Old World, and whose greatest depth at the bottom of the Caspian is from 500 to 600 feet below the level of the ocean, and looking at it as a phenomenon wholly unique, the question arises: How would such a condition be possible, contradicting, as it seems, all analogies? The answer, could we reach it, would not fail to illustrate many recondite geological questions, and to be full of instruction.

Yet the time has not come when a full answer can be given to this inquiry. We have not yet learned the elementary conditions of this remarkable fact; there are innumerable investigations yet to be made, before we can feel perfectly certain that its reason is understood. Still, there have been some preparatory inquiries entered upon, and some preliminary steps taken toward reaching a conclusion, or, at least, toward assuming a reasonable hypothesis. We have already indicated our belief that this depression is connected with a ring of plateaus which have been upheaved around it, and which now inclose it and isolate it from the ocean.

The hollow has its greatest depth near the southern extremity of the Caspian, where it rises abruptly to the Persian plateau. There pass, in the form of a half circle, the loftiest mountains and plateaus of central Asia. On the west side the Caucasus rises, with its giant peaks of Kasbek and Elbrooz, 15,000 to 17,000 feet high, bearing all the marks of volcanic origin,—avalanches of solidified lava on the sides, a lake lying in the abyss of an extinct crater, and the like.

At the southwest, the Armenian plateau follows the course of the Aras from its mouth back to the huge dome of Ararat, 14,656 feet high. The entire geological appearance of that region—the old lava streams, the trachyte rocks—indicate with equal clearness, as in the Caucasus, the agency of volcanic forces in the upheaval of that district. Traces of this great power are also seen in the caldron-shaped hollows, and in the narrow and deep defiles, which are abundant in that region.

South of the Caspian, which in its southern part reaches a depth ranging as low as 420, 480, and 600 feet, and, according to Hanway, even 2700 feet, rise sharply from the sea the Persian Coast Mountains. The plateau of Teheran, 3400 feet in elevation, is directly beyond, from which rise the volcanic peaks of Demavend, 20,000 feet, and Euczan, 6600 feet high. The Coast chain embraces the Elboorz Mountains, uniformly more than 5000 feet high, but which, at Schemrum, northwest of Teheran, rise to a height of 8560 feet; at Churchurah, southwest of Demavend, to 7650 feet; at Nevo, southeast of Demavend, to 8540 feet; at Nejoster, in the Seriakush, east of Demavend, to 7200 feet; and which, above Asterabad, rise in the Shahkush and the Sundukkush to a height of 7270 feet, and almost everywhere display in their trachyte rocks the traces of ancient volcanic activity. Still farther to the east, the chain which has girdled the Caspian sinks from the lofty height of the Northern Taurus to 1872 feet; in Meshed, 2628 feet; in Herat, an average elevation of 3400 to 4000 feet. But east of Herat it rises abruptly to the lofty plateaus of Bamian and Cabool, 7000 and 8000 feet high, and in the peaks of Colubeba 16,800 feet. The Hindoo Koosh, at Dsellalabad, rises to a height of 18,984 feet; the table-lands of the Bolor, at the Issikul, are at an elevation of 14,664 feet; while the gigantic Pameer is not yet measured, though its noted Pass is estimated at 18,000 feet above the sea.

At this point we reach almost the 40th degree of N. lat., whence northward the mountain ranges gradually decline in height, after throwing off eastward the great chain of Thian-Shan. From the sharp angle formed by the Hindoo Koosh and the Bolor, where the head-waters of the Gihon rise, that large but commercially unimportant river takes its way westward through the Bokharan table-land, falling so rapidly in its course to Bokhara that at the city its surface is but 1116 feet above the sea, then striking northwesterly to the Aral and Caspian. The course of that stream indicates, therefore, the direction and degree of the mountain slope toward the great depression east of the Caucasus and Armenia, north of the Persian highland, and west of the Hindoo Koosh and the Bolor systems.

The lower course of the Gihon, from Bokhara downward, is through masses of mud, sand, and gravel, and can very easily be conceived to have changed its course in the lapse of centuries, from the Caspian to the Aral, as the course of the Sihon seems also to have changed. The great Bokharan plain is covered in this part with a deposit of dried mud; it is a steppe formed evidently from a now dry sea-basin, which, no less than the northern shores of the Caspian and the Aral, displays the traces of the oceanic character of entire regions.

Halley, the astronomer, made an attempt to solve the mysterious origin of this great sunken basin, and attributed it to the stroke of a first-class comet! Arago, instead of calling into the scene meteorological forces little known, contented himself, in his theory of its origin, with the forces which we know are active even now on the earth, the plutonic powers which are only half confined by the surface of the globe. No one, he says, will hesitate now to accept the upheaval theory, through which geology is able so clearly to indicate the forces and progress of structure of the soil and rocks. The upheaval of great masses in one place predisposes the depression of districts in their neighborhood, to make good the true relation of highland to lowland. And in this case a compensation may be found, according to Arago, for the great semicircle of mountains which passes around the southern margin of the Caspian basin, in the depression caused by the natural falling in of the adjacent region when the great mountains of western Asia were upheaved.

In longitudinal mountain chains the parallel ranges of valleys have a similar origin; in volcanic chains, which have been thrown up in a circular form, similar depressions have been found in the middle, although, it must be confessed, on a much smaller scale of dimensions than in the Caspian hollow. The same feature is observable in the upheavals, by Von Buch, as observed in the Island of Palma, one of the Canaries, or in the Val di Bove, near Etna. Such depressions would at once fill with water, if connected with the sea, as in the cup-shaped island Santorini, or remain land-locked, if they occur in the interior, as in the case of Lake Laach, as the half-ring of mountains girding the lower portion of the Caspian seems to consist mainly of trachyte thrown up by volcanic agency: the analogy just drawn does not seem too remote. Yet the process of structure must have had other concomitant conditions to account for the vast reach northward of the Caspian depression. It is clear that any such volcanic convulsion as would throw up those vast mountain ranges at the south, must have affected largely the geological condition of all the adjacent region; the extent vertically of this effect would be best ascertained perhaps by deep boring. Unquestionably there was many a revolution in the upper portions of the earth’s crust during the formation of the great Caspian hollow, before it assumed its present condition. From the agencies at work in connection with a great internal ocean, the upper soil, as we have it to-day, was formed.

The Aral and the Caspian Seas remain as the lowest places of that great depression, water being found in them, while elsewhere it has entirely disappeared by evaporation: leaving us broad, low plains, instead of that great ocean which once extended from Persia over all Siberia, and west of the Caspian to the Sea of Azof. A more thorough account, geographical as well as geological, cannot be given till after much more extended investigations have been made into the physical characteristics of this region than as yet have been prosecuted. It may be remarked here, that the waters of the Aral and Caspian are bitter and salt, but not so much as those of the ocean; the bottom is covered with slime and sand. The Aral has a depth ranging from 90 to 222 feet; the Caspian, beginning with its extensive, shallows at the north, deepens toward the south, till, reaching the lower third, its depth is over 600 feet; and thence southward it is no less deep, till it reaches the bold shore of Eusellis. From this lowest point the upheaval begins, which culminates in the great mountains on its southern border.

According to Humboldt’s view, the great Caspian hollow embraces not only the basin of the sea, but a vast dry plain, extending northward as far as Saratov and the Obstshei-Syrtis; even Uralsk lies lower than the level of the Black Sea. The same physical feature, though on a less extended scale than here, is found in Holland, China, Lower Egypt, and Palestine. Subsequently to the emergence of the continents, long before the filling in of huge fissures by mountain chains, and during the continuance of those great convulsions which reach back into the remotest geological periods, the surface of the continents must have been subjected to frequent partial changes of level. The surface undulated probably in that same wave movement which is now observable, though in much less degree, in those earthquakes and upheavals which the whole western part of South America is experiencing even now.

The depressions which have assumed a permanent form since the convulsions which formed them, have gradually filled with deposited soil, and, were the naturalist able to lay bare the primitive rock, he would discover that it exists in the shape of great concavities, without a trace of that evenness which now characterizes the surface. Eichwald has made it probable, by his personal observations, that the upheaval of Ararat and of the Armenian plateau on which this trachyte mountain rests, has driven the Caspian Sea back east of the flat steppe of Karabagh and Mogan, on the lower Aras, to the neighborhood of Bakoo. The water of that sea formerly extended to the confluence of the Bargashad, (called also Bergershat and Bergernet,) with the Aras, below Ireben. The traces of volcanic action there are decisively evident: the Caspian reached, before that action occurred, up what is now the valley of the Aras, as far as Ararat; and in many places south of Erivan—at Saliyan, in Shirwan, and elsewhere—salt beds of the most crystalline quality, forming whole mountains and whole belts of salt lakes at the confluence of the Aras and the Koor, demonstrate their formation in a former sea which once covered that region. The very recent upheaval of the Ural chain cannot fail also to have had an influence in contracting the dimensions of the Caspian hollow.

Only two kindred depressions to this remain to be spoken of, which, though of not so great superficial dimensions, are of yet greater depth—the depression of the Jordan Valley and the bitter salt lakes on the Isthmus of Suez. These we must consider before we pass from the contrasts between highlands and lowlands to the transitions between them.

The Depression of the Jordan Valley and of the Dead Sea.

The nearest relationship to the Caspian hollow, displayed by any similar feature, is found near the heart of the Old World, in the comparatively diminutive and isolated valley of the Jordan, including the Dead Sea, whose absolute depth below the level of the ocean has been determined only within the most recent period. Many former travelers had noticed, in the deep gulf which holds the Dead Sea, and especially at its north end, near Jericho, a much greater degree of heat than elsewhere in Palestine, and the existence of many plants and fruits which they had met in the hotter climates of Arabia and India. The tree which yields the Mecca balsam flourishes in the oasis of Jericho; the product of the balsam of Palestine supplied the pin-money of Cleopatra. A number of German and English observers endeavored to solve the question of the depth of the Jordan basin—von Schubert, Russeger, von Wildenbruch, Moore, and Bake, later Symonds, and Lynch; de Berton and Russeger made the first barometrical observations at the Dead Sea, but they did not attempt to give more definite limits to their results than to assert that its surface is somewhere between 500 and 1100 feet beneath the ocean level.

Von Shubert’s barometer did not suffice to determine this point, but he ascertained the surface of Lake Tiberias to be 535 feet below the surface of the Mediterranean. All barometrical measurements were unreliable at that depth; yet it could not be denied that the depression could not be an insignificant one. A measurement with the level made by Symonds, an Englishman, from Jaffa to the Dead Sea, in 1843, gave us our first sure results. The surface of the lake lies 1231 feet beneath the level of the Mediterranean at Jaffa. The subsequent expedition of the Americans—Lynch, Dale, and Anderson, in 1848—has given the following additional results:—

The surface of Lake Tiberias lies beneath the ocean level, 612 ft. ” ” the Dead Sea ” ” ” 1235 ”

Soundings of the Dead Sea, made with the greatest care, determined the depth to be, according to Lynch, 1227 feet; according to Symonds, 1970 feet. The entire depression below the ocean level would be, then, by Lynch’s measurement, 1235 + 1227 = 2462 feet; according to Symonds’, 1235 + 1970 = 3205 feet. This is the greatest known depression on the globe. Jerusalem lies 2449 feet above the ocean level. From the roofs of the city to the surface of the Dead Sea is, therefore, 2449 + 1235 = 3684 feet; and the entire descent from the capital to the bottom of the Dead Sea is 4911 feet, if we adopt Lynch’s measurement, and 5654, if we follow Symonds’.

The basin of the Dead Sea consists of two very different parts—the larger and deeper northern one, the smaller and shallow southern one; the two being separated by a sandy peninsula—el Mesraa—and connected by a narrow channel of insignificant depth. The northern basin seems to owe its present form to the unchanged primitive depression; the southern one to a partial upheaval at some later epoch. But in breadth they do not vary much one from the other; both have their larger axis coincident with the Jordan valley, which here widens a little, but which is still hemmed in here, as farther north, by the parallel ranges of mountains. The chain east of the sea appears to rise a thousand feet higher than the one west of it. The depths of the two basins are entirely unlike. The southern is nowhere more than 12 feet deep, and diminishes to 5 feet and less than this near the shores, so that the southern half of it is entirely unnavigable by craft of any size; and those who wish to land have to wade for a long distance through mud as deep as their ankles. The northern part, on the contrary, attains a uniform depth of more than 1000 feet, from the north to the south; in the northern third it is even 1227 feet; toward the west coast it shoals to between 600 and 800 feet, but is 500 feet deep hard-by the coast. There is but a very narrow rim of shallow water on the western side, and the navigation is, therefore, tolerably safe. On the eastern shore the coast is even bolder, and the descent to deep water immediate. Close by the romantic mouth of the Arnon, embouching through rocks, the depth of the sea is about 1052 feet. So great a difference in the depth of the two basins seems to indicate a considerable diversity in the manner of their formation.

Volcanic activities have been felt in the Jordan valley up to the present time. They manifest themselves in various forms—deposits of salt, hot springs and naphtha springs, asphaltum beds, sulphur fumes, currents of heated air, clouds of smoke, and rumblings beneath the surface. The Jordan valley remained, from Lake Tiberias down, unfilled, as we should infer from analogy that it would be by the upheaval of a chain of volcanic mountains; or by the expansion of an internal lake or sea, the waters accumulating till at last they should acquire such volume as to break away and form new channels. In case the obstructions were too great, they would remain inland lakes. And such is the Dead Sea, its southern border being too high to allow it a free exit into the Red Sea.

Many other fissures or hollows on the surface of the continents would be regarded as lowlands, were they not filled with water. The bottoms of such lakes often sink suddenly to a great depth, while others are lagoon-like, or shallow seas of an entirely different hydrographical character. Internal lakes, regarded as isolated lowlands, merely filled with water, are an especially interesting theme of study; yet much remains to be investigated regarding their structure and historical formation. The Dead Sea has been regarded, up to this time, as the deepest of all such lakes. The greatest depth of the Caspian has not yet been fully ascertained; but if Hanway’s soundings, 2700 feet, are to be relied on, it is very great. Lake Baikal, in its deepest part, between the two steep walls of rock which rise high above the surface, has not yet been carefully sounded; but as its surface is 1500 feet above the sea, its bottom does not probably fall below the ocean level. The great chain of North American lakes, whose area embraces about 109,500 square miles, are surrounded by level country from 500 to 600 feet above the sea—a region which, in part, falls under the designation of plateaus of the lowest class, and which, in part, comes under the name of lowland; the surface of Lake Superior being 627 feet above the sea, Lakes Michigan and Huron 578 feet each, Lake Erie 565 feet, and Lake Ontario 232 feet. The three first named, having a depth of about 900 feet, have their beds about 300 feet below the surface of the ocean; Lake Ontario, with a depth of 500 feet, reaches a point 268 feet below the sea level. The depth of the St. Lawrence river bed, as related to the sea, is not ascertained. The most of the Swiss lakes, too, having a depth often of more than 1000 feet, come under the same category with the lakes under consideration above, waters from the mountains having gradually filled up chasms made at the time of the upheaval of the adjacent region. Some of these lake basins may be deep enough to lie below the level of the ocean.

The Bitter Lakes of the Suez Isthmus.

Some bitter salt lakes on the Isthmus of Suez, forming a chain from the Red Sea to the southeast corner of the Mediterranean, long claimed attention from their supposed singularity. During the occupation of Egypt by the French in 1799, a survey of the district was made with the level, in view of a prospective canal across the isthmus, connecting the Nile with the Red Sea. An account of that survey was published by Le Père, in his great Description de l’Egypte. The result of the survey was very surprising; it assigned to the Gulf of Suez a height of 25 feet at ebb tide and 30½ feet at flood tide, above the level of the Mediterranean, a result which seemed to agree with Pliny’s account (vi. 23) of the elevation of the Red Sea above the level of lower Egypt. The salt swamps lying between the two seas, and known even to the ancients, lie, according to the same authority, 20 feet below the surface of the Mediterranean, and 50 feet below that of the Red Sea. These singular statements were not received without considerable doubt as to their correctness; but during the military disturbances in that region, no revision of the investigations could be made. Certain circumstances connected with an unusual inundation of the Nile in 1800, when its waters flowed as far as the transverse valley called the Wady Tumilet, in which the salt lakes lie, and where traces of the ancient canal, built by the Egyptians between the seas, could be seen, seemed to confirm the result of the survey of 1799. The inference was a natural one—that the sandy Isthmus of Suez was an accumulation of dunes, and of the deposits of inundations of both the Mediterranean and Red Seas, and that the salt morasses in the middle are but a trace of the primitive bottom. There were not wanting defenders of the old measurement, Favier being the most prominent. Since 1845 five surveys have been made, in reference to the projected canal. These all contradict the results of 1799, and show that there is but the difference of four-sevenths of a foot between the level of the two seas, and that there is the same agreement there as in all other parts of the earth. Many hypotheses, built on the old measurement, have accordingly fallen to the ground.

The Regions of Transition between Highlands and Lowlands; the River Systems of the Globe.

Between the two great and most sharply-marked physical features—the high plateaus and mountains and the lands of very little elevation—there are regions of transition very numerous and exceedingly varied.

The conception of highlands and of lowlands having a certain, constant, and absolute value, and it being immaterial whether the elevation be specially marked or not, provided it be uniform, the regions of transition find their most marked characteristics in their want of constancy, in their very change, and the rate at which the grade ascends from a low to a high elevation, or falls from a high to a low one. Their real value lies in the mutual compensation of highlands and lowlands, which is effected through the mediation of a third physical feature or system, which has received the name Lands of Gradation, or Terrace Lands, and which, by their gradual rise from the sea level, serve as the means of transition from the lowest lowlands to the loftiest plateaus and mountains.

Terrace Lands and Rivers in their General Character.

Districts sloping to the sea, or lands of gradation, as we have called them, varying as they do in elevation and in relative situation to each other, are the true mediators between the districts but little above the level of the sea and others much more lofty. At the sources and the mouths of rivers they partake, more or less fully, in the characteristics of both highland and lowland. The manner of their mediation, as determined by the rate of the fall of water and by their direction, gives to every one of these regions of transition its peculiar character, determines its conformation and its relation to the globe. And yet, no more than in lowlands and highlands, can we rid ourselves of some arbitrary data relating to the size of rivers, when we discriminate between those which we call large and those which we call small. As in all other geographical distinctions, we must here be content with arbitrary approximation, and with the ordinary usages of speech. The comparison of streams, in regard to their breadth and fullness, determines their volume; the comparison, in respect of length and tributary waters, determines the compass of the river system. The entire characteristics, breadth, depth of channel, length and extent of drainage, determine the status of the river, whether first, second, or third class, in relation first to those of the same continent, and then to those of the world. The Volga, for instance, is, in relation to Europe, a first-class river, but, like the Danube, in relation to the entire globe, is merely in the second or third rank. Not the length alone determines the importance of rivers. The Thames, one of the smallest streams in Europe, is one of the most important. And aside from commercial considerations, a river of insignificant size can have great influence in consequence of its relation to the entire adjacent region. The little Bavarian Isar, a river which, so far as the great world is concerned, seems to have no importance, receives on the left side the water of 860 tributary brooks, among which are 44 rivulets; on the right bank the water of 433: these 1293 brooks and rivulets pour themselves into the Isar through 103 direct tributaries, and not these alone, but the waters of 136 lakes are embraced within the Isar system! Yet the Isar is only one of 34 branches of the Danube, and of the fourth rank even among them, and the Danube is by no means one of the great rivers of the globe. A short but navigable stream can have great influence over a territory limited in extent, and may make a long but shallow stream sink into insignificance in respect of comparative importance to the world. There are some great streams which are of first magnitude in all their characteristics—rivers which drain millions of square miles in their course to the sea. The number of such is small, however; there are scarcely fifty on the whole globe. Besides these, there is a large number of rivers much shorter, and of much less volume, but not deficient in the attributes which give a stream value to man, and which serve to mediate between highlands and lowlands, to fulfill the needs of navigation and to drain regions of more or less magnitude. These can be classed in four ranks: in the first place absolutely, and in the second place in relation to each continent. Yet, in classing them, it is necessary always to keep in mind that it is not size alone which gives a river its value, but a combination of all its characteristics, and its relative influence on the country through which it runs.

Looking at the direction of streams, we observe that there are some which flow northerly, as for instance those of Siberia, the Nile, the Rhine, the Elbe, and the Weser; there are those which flow southward—the Indus, Ganges, Euphrates, La Plata, Mississippi, and Volga, for example; there are those flowing eastward—Hoang-ho and Yang-tse-Kiang, the Amazon, the Orinoco, and the Danube, for instance; and some westward, instances of which may be found in the Gihon and Sihon, the Senegal, Gambia, Niger, the Colorado, the Seine, Loire, Garonne, and the Spanish rivers which enter the sea in Portugal.

And this characteristic, trite and unmeaning as it may at first seem, establishes, for the area which these rivers water, very diverse conditions. In like manner, too, their position, in relation to the oceans into which they flow, is very influential, in consequence of the action of the tide upon the lower course. The emergence of their head-waters at various altitudes, whether on plateaus of the first or second class, or on mountain tops covered with perpetual snow, gives rise to a great diversity of relations, that makes no one stream on the earth twin brother to any other. Rivers have an individuality which claims recognition, although they are usually summed up in one category.

This diversity in rivers becomes more apparent from a study of the diversified form of the terraces, or grades of transition, through which they pass on their way to the sea.

The great basin of the Nile is divided into three distinct parts or grades—Abyssinia, Nubia, and Egypt; and each of them has long been studied historically and physically. The great basin of the Rhine is also naturally divided into three grades—the Swiss highlands, the German moderate plateau, and the lowlands of Holland. In a similar manner there may almost always be traced in rivers three natural grades, and where they do not have, as in the cases just cited they do have, a historical significance, their physical influence is not hard to trace and to follow into all its analogies.

The word water-shed, now a familiar one, is applied to that point of division where contiguous springs pour their water in different directions. It is not even in a mountainous country necessarily coincident with the highest points of the chain, though it may be; the valleys may slope in such a way as to have more influence in determining the direction of running water than the mountains hard by. Every stream has its own water-shed system, and this system is the real boundary of its basin. If we trace this basin to its very limits on the highlands, we may find, not a mile away, the beginnings of another river, which shall flow in just the contrary direction, as for example in the case of the Rhine and Rhone, the Volga and the Dwina. The sources of the Missouri and of the Columbia lie close together, not a quarter of an hour’s walk apart; yet the waters of one flow into the Atlantic, of the other into the Pacific, and their mouths are almost 2500 miles apart. The Mongolians hold the water-shed in such estimation that they throw up a heap of stones wherever one occurs, establish it a shrine for prayer; and the Toongooses of Siberia never pass by one without casting a cedar branch upon the stone heap, that, to use their expression, “the holy mountain that parts the waters may not lessen, but increase.”

The main channel is the stream proper; the others are tributaries. The longest tributaries coming in from the region where the river proper rises, can be grouped intimately with the source of the main current, hardly distinguished from it in relative importance—the two, for instance, in the Nile, the five in the Indus, two in the Ganges, three in the Amazon, etc. All form in their confluence the real channel of the river. And the entire body of tributaries, taken in conjunction with the river proper, forms the river system, and the district which they all drain is their true reciprocal. The two, in their mutual action and reaction, form a whole, and are always thought of together. The source and the mouth are the beginning and the end of the whole system; the main channel and the circuit of water-shed, the center and the circumference of it. All the tributaries in their union constitute what may be called the arterial system of the river basin; the form of each and the characteristics of each are analogous to those of the whole, only in reduced pattern. The network which all the tributaries make is often surprisingly intricate. The symmetry with which the main characteristics of a river system are carried into the details, even of its smallest accessories, can only be compared to that observable in the architectural regularity of a tree, as it expands from the main trunk into the countless symmetrical branches.

There are some rivers which are entirely independent of tributaries—which pursue their way to the sea entirely alone. Such rivers, however, never belong to the first class; they are always of subordinate magnitude, and the humblest of them are mere coast torrents, like those west of the Andes. Others find their way to no ocean, but lose themselves in an inland sea or lake, as the Volga does in the Caspian; as the Gihon and the Sihon do in the Aral; as the Jordan does in the Dead Sea. Others disappear in sand wastes or in morasses; such are the rivers of the African steppes. Others are blocked up, as it were, by the tidal wave of the ocean, and are thus converted into estuary lakes.

There are some rivers, also, which remain equally or nearly equally full the whole year through; there are others which have their seasons of overflow: the Nile, for instance, and many rivers whose basin lies within the region of tropical rains; there are temporary rivers, now full, now empty, which, if they do not leave, like the torrents of Arabia, a perfectly dry bed, are traced in the dry season by a row of stagnant lakes, such, for example, as are found in the swampy lands of Australia.

Rivers more closely considered.

What is peculiar to every river is determined by the abundance of its sources, the forking of its tributaries, the rate of its descent, the distance from its most remote springs to its mouth, the main direction of its course, and the greater or less sinuosities of its channel, as occasioned by the structure of the country which it traverses.

The abundance of its waters is conditioned by the greater or less amount of snow which finds the highest springs, the heavy rains which it receives in tropical countries, and the exceedingly varied influences which temperate climates may exert upon it. The fall softens from the rush and plunge of the mountain district, first to an arrowy swiftness, then to a moderate course, then to a beautiful gliding motion, to end with an almost imperceptible flow just before entering the sea.

The direction of rivers is determined:—

1. By the structure of the region which they traverse, the layers being in some places horizontal, and in others tilted to a vertical position; here grouped, as in the granite Carpathian chain, in such a way that the river courses which begin there run in parallel lines, radiating like the rays of a star from a central point; then grouped in such a manner that a stream may receive tributaries from two nearly contiguous ranges, as among the spurs of the Ural Mountains, the Rhone in Valais, receiving waters from the Bernese Alps at the north, and Pennine Alps at the south; the Isère, in like manner, the Upper Rhine in Grisons, the whole Upper Inn in Tyrol.

2. The direction is also determined by the mutual action of tributaries and the main stream at the point of confluence. Very often the union of two powerful currents gives rise to a third direction, according to the law known as the parallelogram of the forces. This generally occurs when no obstacle stands in the way of their taking a normal course, and is exemplified in the cases of the Kama and Volga, the Theiss and Danube, the Rhine and Main, the Saone and Rhone. Where an obstacle stands in the way, their abnormal direction is manifested in the abrupt bendings of the river bed. An instance is found in the bending of the Rhone northward as it emerges from Valais. Its lower course, from Lake Geneva to Lyons, betrays the same angularities, resulting from the obstacles which it meets and cannot remove. The Rhine, breaking through the Jura at Basel, is another instance; the Rhine, between Bingen and Caub, and the Dal-Elf, in Sweden, also exemplify the same.

In case that rivers meet in their course large masses of stratified rocks, they force their way through them in a zigzag direction, making sharp angles always, and not unfrequently right angles, even. Instances of this are found in the Rhine, between Mayence and Coblentz, and in the Moselle, between Treves and Coblentz. When the river passes beyond these rocky barriers, and meets with obstructions of a more movable character, it crowds them more gently and gracefully aside, and leaves a path more sinuous and wave-like; and yet more gentle are its curves, as it opens a way through the plains where nothing obstructs its course. The last is strikingly exemplified in the rivers of eastern Europe, especially in all those of middle and southern Russia. The practised eye can determine the structure of the soil with considerable certainty, by merely tracing the course of rivers when represented on a faithful map. For, unless there be other reasons to prevent, rivers always force their way where there is the least resistance to overcome. In stratified rocks, where the tilt is so great as to make the strata vertical, the river beds usually run parallel with the lines of stratification. Instances are found among the Alpine rocks, in Valais along the Rhone, in Tyrol along the Inn and Adige, in Grisons, and among the Jura along the Rhine. Where the lines of stratification are horizontal, rivers usually take their course through the most marked ravines and fissures.

In most mountains, however, the lines of stratification are neither vertical nor horizontal, but intermediate between them, more or less sloping, as in most marked ranges of central Germany, for example. In such cases, the process of excavating river beds has been determined by various circumstances and conditions, and the direction of their channels does not alone depend upon the extent and tilt of the strata, but also on other forces which have exercised a favoring or a retarding influence on their direct course. The stratification has its influence, indeed, but it is general rather than specific. Still, it is very largely felt when it happens to coincide in its main lines with the direction of the mountain range, but is comparatively insignificant when it does not. We have instances in the Alps where the axis of stratification coincides with that of the main chain, from south-southwest to north-northeast; in the Jura, from southwest to northeast; and in the Scandinavian range, from south to north.

The different geological formations found in mountain districts have a very important influence in determining the direction of rivers. Mountains do not generally consist of rocks of one kind of structure, but of several. What stratification is to mountains whose geological formation is the same throughout, the superposition of different kinds of rocks is to those of composite materials. The layers may be divided into superior, inferior, and adjacent. These usually vary in respect to age, and may be traced in a regular geological seniority, as for example sandstone, gypsum, limestone, gray-wacke, and granite. These formations are either closely contiguous, or are separated merely by valleys, as for instance in the Carpathian chain, where the central granite knot is separated by valley plains from the more southern limestone chain; an example of contiguity is found on the west spur of the same Carpathian range. Wherever mountain systems of varied geological structure approach each other very closely, rivers seldom break their way through either one, but find their way along the roots of the mountains, till at last they come to a less confined place. Such river courses are often very large and deep; for the mountain streams which meet and are hemmed in by the narrow pass between the two contiguous ranges sweep all loose obstructions before them, and not only leave their path clear, but continually deepen it. We find this in the Ural, the Isère, the Rhone, Aar, Inn, in all the long and winding Alpine valleys, and in the Ebro, fed by the parallel ridges of the Pyrenees. The circle of rivers which girds the central Carpathian knot is an illustration of what was said a moment since. The Poprad, Dunayic, Arva, and Waag are found where the true Carpathian chain, which is granitic, is closely contiguous to subordinate ranges of limestone and gray-wacke. In any accurate map, the long, winding course between these two chains may be easily traced. Looking at the point where the Hartz Mountains and the Thuringian ridge touch at their roots, the groups are seen to be insulated, as it were, by the rivers which gird their bases. In the great streams of southern and southwestern Asia, too, the line of the water-courses can be traced along the narrow valleys which separate main from subordinate mountain chains; the Terek, Kooban, Koor, Aras, Euphrates, Tigris, Indus, Ganges, and probably the Chinese rivers, are all examples of this.

Some streams seem to be entirely independent of all these laws in forming their channels, and to have their direction assigned to them by the freaks of nature, such, for instance, as fissures in mountain chains and clefts, which remain to indicate ancient convulsions.

The entire course of a river is divided into three distinct and subordinate courses—the upper, middle, and lower. To these and their respective tributaries correspond the three grades of transition found on the banks, and which have already been alluded to. Not only the total amount of fall in the river bed, but also the angle of inclination, and the whole complex of phenomena in the basin, are reciprocal to the threefold character of transition in almost every hydrographical system in the world. Still, the variety of relations which arise from the combination of different elements is so variable, that an almost infinite diversity arises in the characteristics of rivers, and these characteristics always vary, too, according as found in the upper, middle, or lower course.

Upper Course of Rivers.

This begins at the ridge of the water-shed, and extends to the limits where the river emerges from the most rocky highlands. It depends for its existence upon the greater fall in the river bed there than lower down. At the upper course, therefore, rivers which may flow in exactly opposite directions are brought into direct neighborhood. The farther they advance from the water-shed the more they recede from each other. In the High Forest south of the Carpathian chain, and in the Bory Morass north of it, the waters which flow into the Baltic and into the Black Seas spring from the ground side by side. The name given to the districts where the head-waters of large and navigable rivers part is usually the French word portages, the English word transports being little used in that connection, although all, the German Trageplatze and the Russian Wolok, involve the idea of _carrying_, of porterage, from the head-waters of one stream to those of another. The lowest parts of a water-shed, the passes of a high mountain range, for example, the intermediate vales of lower ones, and the most elevated plains in flat districts, are the most suitable for the purpose of canal building, to serve as a connecting link between the sources of divergent streams; as, for instance, the canal which is proposed to connect the Baltic and the Black Seas by uniting the Vistula and Danube, the tributaries, the Poprad, Hernad, and Theiss being the channel of communication up to the mountains where a canal is to pass over the water-shed formed by the valleys of the Carpathian chain. Such a communication is the most available which can be made between the opposite sides of a mountain range. The practicability of constructing such canals depends very largely upon the degree of fall in the upper course of the connected rivers, as determined by the slope of the bed toward the horizon. The grade of most mountains’ sides, which stand back to back, is unlike on the two sides: steep on the one, slight on the other. Upon this depends the greater or less wildness of the streams flowing through their upper course. In the Ural chain the slope is steep on the eastern side, gradual on the western; in the Caucasus, steep on the north, gradual on the south; in the Carpathian and the Alps, just the reverse—steep on the south, gradual on the north. The rate of fall varies; but, in general, it lies between an angle of 2° and an angle of 6°, taking the entire upper course into account. On the very steep north side of the Pyrenees, the fall is between 3° and 4°; on the south side of the Alps, from the summits of Mont Rosa and Mont Blanc to the plains of Piedmont, it is 3¾°. It is far less in more unimportant ranges. And this angle, it should be remarked, is an average; it is the resultant of a great number of special, short slopes, which vary from the perpendicularity of an occasional waterfall to the equally occasional tranquillity of a meadow-like flow. The incidental slopes are, of course, much greater than the average of all. A grade of 15° is very steep; it is the maximum that can be ascended by a beast of burden. A grade of 8° is the maximum for wheeled vehicles; all roads must be less sloping than this. To accomplish the ascent of 35°, a man on foot must have some assistance. A grade of 44° in the high peaks of Mexico and Peru, Humboldt found inaccessible; only where the growth of trees and shrubs gave him an opportunity of planting his feet, could he climb where it was a little steeper than 44°. The Carpathians and the Pyrenees, on account of their steepness and their scanty verdure, are very difficult to ascend. The Alps are much more easily climbed than the mountains just mentioned, in consequence of their abundant growth of turf and undergrowth. The richest Alpine meadows of Switzerland have an inclination not exceeding 20°; at a greater slope the vegetation becomes more sparse. The grade on which it is possible for earth to cling, Lehman fixes at 45°, and considers that the normal slope, because at a greater angle, rain glances or ricochets. But Lehman is not right in assigning this as the normal slope possible for earth to cling and vegetation to grow, for on the Alps soil adheres and plants get a footing at a much steeper angle than 45°; in fact, the modifications in the appearance of the Alps, by the growth of trees clinging to steeper slopes than this, are very marked. From the highest possible grade where vegetation can get a footing, we advance to the sheer perpendicular.

The upper course of rivers is characterized rather by plunges than by equable flowing, and determines its way by a series of leaps through zigzag cuts and various ravines. It traverses bowl-shaped hollows and narrow defiles, and makes its way even through mountain lakes, depositing in them its residuum of sand and gravel which it has caught up and swept along. In its wild plunges it draws into its body considerable air, which appears as bubbles, and makes it a white mass of foam. By-and-by it reaches more level ground, becomes clear as crystal, and assumes a rich emerald green, or a deep blue. It is unnavigable, wild, romantic, and is always found in mountain districts.

The brawling brooks of Salzburg, of the Pyrenees, and of Sweden and Norway, all partake of this character. Those of the Pyrenees have a fall of an inch in every foot, and in some places cataracts of two or three feet. The same is observable in the Alps, where the continual stir of the water mixes in air enough to turn all into a mass of silvery-white foam. The Carpathian waters are the same before they reach the high plateaus lying at their feet. The Alpine lakes, too, which lie within the upper course of the rivers which feed them, have a considerable fall; Lago Maggiore, for instance, has a descent of 52 feet between Magadino and Arona.

In all the most marked mountain systems of Europe, the upper course of the rivers is especially prominent. Northern Europe is characterized by the fact that its streams have, throughout the most of their length, the peculiarities of the upper course—whether observed in northern Russia, in all Sweden, Norway, and Scotland.

With the exit of the river from the mountain district, all these relations are changed, and a new character begins.

The Middle Course.

Far more moderate is the descent after the river emerges from the mountain region, or where it has never experienced the wild turbulence of the upper course, as is the case in most of the rivers of eastern Europe. In the middle course the angle of inclination is much modified. The upper Main has a fall of 342 feet within three miles after leaving Fichtel Mountains. The descent of most of the rivers of central Germany is much less than this. The Neckar, whose sources lie 2084 feet above the sea, in passing to Heilbronn, which is 450 feet above the sea, falls at the rate of about an inch to every 32 feet. The fall of the Saale, after leaving the Fichtel range, is about 20 feet to the mile; that of Naab, about 14; that of the Eger, less; and that of the upper Oder, in Silesia, still less. More gradual yet is the slope of the Volga bed, which falls but 1400 in about 2050 miles, considerably less than a foot to a mile; and in its lower course its inclination must be still less.

The effects of the current must necessarily be very different from those observable under the influence of the dashing and wayward upper course.

The name River Bed is given to the entire breadth of the hollow which holds the river, and which varies in width according to the stage of the water, especially in large streams like the great rivers of America. The Mississippi is a mile wide at Natchez at low water, at high water almost thirty. The Orinoco, at St. Thomas, is three miles wide at low water, at high water it is over seventy. In the Volga and the Danube the stage of water makes great differences in the width of the river bed. In summer the depth and breadth are, as a rule, less than in winter.

The Channel differs from the river bed; it is the part of the river bed which gives life and motion to the whole current. In the upper course the channel and the river bed generally coincide; in the middle and lower courses, on the contrary, the channel occupies but a very small share of the whole bed, but yet it determines the direction, amount of fall, and the rapidity of the stream. It lies usually not in the middle of the river bed, but on one side; it passes, however, from bank to bank; it is indicated by the movement of ships, which always follow it, and it lies uniformly adjacent to the boldest shore. It widens the whole river bed toward one side, and not toward both; and so streams which traverse great plains, like the great Hungarian one, for instance, do not now run through the middle, but course along at the base of the marginal bluffs. In all such cases, it will be found that the channel hugs the boldest side of the bed. All the four Carpathian rivers, as they wind out between the main range and the subordinate ranges, have their steepest shore, not on the side of the loftiest, but on the side of the boldest mountains, and these are the ones of the subordinate range. So, in the plains which lie between the Swiss Alps and the Jura, the bold sides of the river bed lie on the side of the bolder though less important chain, and not on the side of the Alpine meadows. The bold banks of the Ebro are not on the side of the Pyrenees and their plains, but on the south side. All the streams of South and Middle Russia have, therefore, on the east side, their low banks, on the west the bold ones; and this, because the most extensive plains lie on the eastern side.

In the more level tracts the windings of rivers are very much increased in magnitude. These windings check the current. The serpentine course is characteristic of rivers in their middle course, and it is repeated, though on a small scale, in every meadow brook. The serpentine course of rivers gives rise to countless islands and intervals: as, for example, between Bâle and the Rhinegau, but, with very few exceptions, no lakes, the characteristic feature of the upper course of rivers. But the broad meadow lands of the middle course very often indicate in the clearest manner that they were once lakes of considerable magnitude, which have subsided and left their basin a dry plain. An example may be found in the meadow land of the Rhine, from Bâle to Bastberg, below Strasbourg, and again from Ladenburg, in the Palatinate, to Bingen. So on the Danube, from Ulm to Passau, Lintz, and Kloster Newburg, and again from Pesth to Beloro Semlin, as far, in fact, as the narrows at Orsova. The same feature is met in the middle course of the Volga, from Tver eastward to the west Ural, and southward to Saratov and Kamishin, where it breaks through the Obstshei-Syrtis, which was, doubtless, once the barrier of a great inland lake. In these basins, now dry, there is a surprising uniformity of characteristics wherever on the globe they occur. They differ but little, whether found in the middle course of the Ganges, the Indus, the Euphrates, or the American rivers. The still, incomplete stream of the St. Lawrence shows us, even in the present, what the ancient conditions were before they solved the problem of their complete development. There, a row of such lakes as formerly existed in the now fruitful plains of the middle Rhine, the middle Danube, and central Russia, are the five great Canadian lakes. They still constitute the middle course of the river, and one pours itself directly into another, either over a gentle slope of land, or in a great cataract and rapids, such as we do not observe in the middle course of other streams, which are not, like the St. Lawrence, incomplete. Only when waterfalls disappear can the inclination of rivers become a gradual one. The uniformity of the grade of their channel is, therefore, a sign that they have attained to a complete development. In such, slight rapids remain, instead of the ancient cataracts. The existence of those primeval falls we find in all rivers, even in the Rhine and Danube. The rounded faces of the rocks which once were the barriers to the rivers’ course, and the debris once swept down from the mountains and deposited over the bottom of the ancient lakes, show this.

The strongest instance of cataracts, resembling the ancient ones which connected the lakes of nearly all the great rivers of the globe, is seen in the fall of Niagara. That cataract is an epitome of the falls of all other streams. The Niagara River conducts the water of Lake Erie, by a channel 33 miles long, to Lake Ontario, 300 feet below it. At the Great Fall the river plunges about 150 feet into a chasm which it has hollowed out from the soft stone between the two lakes. The cataract was formerly seven miles below its present location, and has been observed to be steadily working backward since its discovery. In the distant future it will, doubtless, wholly disappear, as all others have done. For the Niagara is merely a striking instance of a principle once universal, but which merely worked itself out on a smaller scale. The more fragments of rock and mountain debris were swept along, the sooner were the primitive falls rent away by the wash and the percussion, and the development of the middle course completed.

The places of transition which lie between the higher dry basins and the lower ones are still to be traced in almost all rivers; not by great waterfalls, which belong only to the upper course, but by simple rapids. They are more or less characterized by narrows, with steep, rocky banks, where, doubtless, cataracts existed in the primitive times. They are recognizable by this feature, that they are uniformly alike, and distribute their force equally on both sides of the river. Examples may be found on both sides of the Rhine, in the narrows between Bingen and Bacharach; on the Elbe, from Tetshen to Shandau, Dresden, and Meissen. In these places the rivers have a very tortuous course, and there are whirls and rapids (rapides, sauts, of the French; saltos, randales, of the Spanish; schewerin of the Russians) which impede navigation. In these localities the entire aspect of nature is changed, and the landscape becomes exceedingly beautiful. Here we find ancient narrow roadways; here are places of great historic interest, and of great interest to the naturalist, assuredly not of accidental origin, but in close connection with the development of the river bed, and in close analogy with all places of transition from highland to lowland.

We may, perhaps, mark these features in all the rivers of the earth. A knowledge of them is essential to understand thoroughly the natural development of a river system in its true parts; unfortunately, they have as yet been too little observed and described. Among European rivers they are found in the Guadiana, at the Saltos de Lobo; in the Douro, at the rapids below Torre de Moncorvo; in the Ebro, at Sastago, below Saragossa; in the Rhone, the rapids below Lyons, between the granite banks of Pierre Encise; in Loire, by Iguerando, below Roanne; in the Rhine, below Strasbourg, and at the narrows at Bingen, near St. Goar and Andernach; in the Weser, at the Porta Westphalica; in the Danube, at Grein, at Kloster Newburg, and at Yachtali, Drenir Kapi, (Iron Gate,) and Orsova; and in the Dnieper, the thirteen waterfalls below Yekaterinslav. The same features are repeated in all the other streams of Europe and the remaining continents. More close investigation of them will lead to important results, concerning the structure of the earth in the regions intermediate between plateaus and lowlands.

As a high grade, great cataracts, sharp and bold cliffs, and mountain lakes characterize the upper course of streams, so rapids, dry lake basins, and a meandering channel characterize their middle course. Below the lowest rapids are found the level plains or lowlands which give rivers their third characteristic.

Lower Course.

As soon as the rivers break through the lowest range of hills which once beset their course, they deposit the debris which they bear with them, and begin the formation of diluvial plains. We find in the soil of all level places along the middle, as well as the lower course of rivers, traces of the same kinds of rock and minerals, which characterize the mountains where they rise. The rate of fall in the lower course of rivers is so slight as to be almost imperceptible. Relatively, it is the greatest in the Volga; from Kamishin to the Caspian the descent is more than 150 feet, although the distance is less than 500 miles. The Senegal, from Podor to the sea, a distance of about 200 miles, falls only about 2½ feet; the Amazon, within about the same distance, falls only 10½ feet, or about an inch to the mile. In such rivers, therefore, the tide can flow a very long way inland.

This gives rise to a great conflict of forces—the pressure of the stream in its natural flow, heightened at the appropriate season by the annual inundation, and the backward pressure of the tidal wave. Before these forces come into equilibrium, the river bed is constantly changing. The river proper seeks this equilibrium by a parting of its channel, dividing into two mouths, as in the Nile, or into more than one, as in the Rhine and Danube, or several (about 65) in the Volga. The momentum of the stream, the resistance of the tide, and the consequent slow speed of the current promote the fall of deposits along the lower course of rivers. Below the surface the result of these deposits is found in sand banks or bars; above the surface, as low, marshy land, the deltas, subject to frequent inundation. We see this in the Rhine, the Nile, the Euphrates, the Indus, the Ganges, the Mississippi—in all, about fourteen of the first-class rivers of the globe. The contrary feature, single, broad mouths not yet filled up by alluvial deposits, negative deltas, or deep ocean inlets, can be observed in nine others of the largest rivers—the Obi, Yenisei, St. Lawrence, Columbia, La Plata—mostly found, however, in the north of the earth, where there is very little of the more loose and fruitful soil which more southern rivers bear onward from the mountains where they rise.

Another peculiarity of the lower course is seen in the extraordinary changes in the river bed—the shifting of the channel from one side to the other. This is the natural result of the very light and movable character of the deposits brought down from above, and the strong pressure of the current, which, though slow, has great momentum. In the lower course of the Ganges, Indus, Euphrates, Nile, Rhine, and Po, these changes can be traced as a matter of history, and, in the lapse of centuries, have had great influence on the formation of the great plains of those rivers’ mouths and on the people living there. With the lower course begins the regular yearly inundations, which cover vast districts in tropical countries; and to these inundations may be attributed the gradual raising of the level of the plains covered by them. Hence arose Herodotus’ descriptive phrase ποταμοὶ ἐργατιχοί, (prolific rivers.) The great fruitfulness of these lowlands is well known. The rich alluvial deposits have made Bengal, Babylonia, Egypt, Lombardy, Holland, and the Netherlands the granaries of all neighboring countries.

In proportion as the mouth of great rivers resembles an inland sea, having a strongly marked tidal flow in sympathy with the ocean, does the whole nature of the lower course vary. The rivers whose mouths are turned to the east and south are those which are exposed to the strongest and the highest ocean waves. Such are Chinese, Indian, and South American rivers, which sometimes show the result of this, 500 miles inland. The tide extending so far into the interior facilitates navigation very much, and transforms the lowlands along their margin into districts, which seem transitional between true continent and oceanic islands. All the mouths of first-class rivers which open toward the north and west are less deeply affected by the entrance of the sea waves. To these belong most of the European streams. Exceptional to both of these classes are the three rivers, the Nile, Danube, and Volga, whose direction is not toward the ocean, but toward the center of the Old World. They form a triad, not of oceanic, but of continental streams; in them there is no ebb and flood. Their lower course and mouths must, therefore, display different relations from those of any other of the great rivers of the globe.

It was early remarked that not all streams, when they reach the sea, flow at once into it, but come to a standstill. It is so with the Thames, and with most of the North American rivers. The ocean sometimes throws a tidal wave twenty to thirty feet high up their channel, and dams their flow. Rivers vary exceedingly in their relations to this high barrier. The Chinese streams are sometimes raised forty feet by it above their normal level. This gives rise to a salt oceanic river, so to speak. It is the same with the Thames at London. At high tide the surface is salt, while the water at the bottom is fresh. The struggle with the downward current and the upward current is very often visible. It is so in the Orinoco, the Ganges, in the Chinese rivers; most of all, in the St. Lawrence.

In all the continents there are many small rivers and rivulets which have no normal mouths; which lose themselves in the earth before they reach the sea. Sometimes they pursue a subterranean course, and emerge again, though usually with a changed name. Among the best-known of such instances is the Perte du Rhone, below Geneva, where the river flows for a little way directly beneath a spur of the Jura Mountains. In like manner, the Meuse, which loses itself in the earth at Bazoilles, in the Vosges Mountains, west of Nancy, flows in a subterranean bed as far as Noncourt, nine miles distant, and then emerges. The phenomenon is common among the Jura, and in the limestone cliffs which feed the Drave and Save. The tourist meets almost hourly there some brook or little river disappearing beneath the ground. On the high Asiatic plateau of Gobi, 68 rivers are known, which disappear in a similar manner; in the north of Thibet there are 115 such. They are common, also, in the Chinese province of Yun-nan, on the Persian highland, and on the plateau of the Bechuanas, in South Africa. In South America, between the Andes and the La Plata, there are twelve lakes without effluents, the greatest being Lake Titicaca. In Central America, there is the Lake of Mexico.

The division of the whole length of a river into the three courses—the upper, middle, and lower—and the proportionate share which each of these bears to the whole, depends upon the height at which the source stands above the mouth. The greater or less extent of the transition grades, and the greater or less extent of navigable waters, also depend on the same. The upper course has, as a general rule, too many hinderances to be very valuable for navigation; it is, at best, adapted only to boats. The more united and deeper middle course offers facilities for vessels of considerable draught; yet the frequent sunken rocks and eddies and rapids are a great impediment to navigation. We find it so in the Rhine, below the Falls of Schaffhausen, as far as Bâle; and in its middle course, at Bingen and St. Goar; in the Danube, also, at Grein and Orsova.

The lower course, on the other hand, opens like a broad fresh-water sea, that sometimes allows large ships to sail 50, 200, and even 500 miles inland. These maritime streams ought to be discriminated from others; the Chinese call them “sons of the ocean.”

The proportions in the length of the upper, middle, and lower course of rivers are exceedingly variable; and equally variable of course are the transition lands apportioned to each, and forming its natural supplement. The upper course of the Volga is very short, the middle very long, and the lower very short. The same relative proportions, though with very different dimensions, are found in the Vistula, the Ganges, the Euphrates, and the Mississippi. The upper course of the Rhine, on the contrary, is very long, through all Switzerland to Bâle; the middle also very long, to Cologne; the lower, very short, to Rotterdam and the sea. It is the same with the Nile, the Danube, and the Indus. In the Marañon or Amazon the upper course is very short, the middle and lower very long. In the Chinese rivers Hoang-ho and Yang-tse-Kiang all the three courses are relatively long.

The length of the middle and lower courses, although important conditions of navigation, are not the only ones. Others are not to be overlooked,—the amount of water, depth of channel, and the like. These, however, are not capable of being generalized under any law, but depend upon the individual characteristics of each stream. Every river needs, for an exhaustive account of its features, its own monograph.

There remains but one important point to be considered—one which has exerted a very great influence on the diversity of structure in all river systems, controlling the area of their drainage, their volume of water, their effect on human culture, and on the ethnographic character of the people dwelling on their banks. It is the distance from the source to the mouth in direct distance compared with that following the tortuous course of the stream. The two lines almost never coincide; they generally lie far apart. And the less they approach to coincidence, the greater becomes the area of the river basin; the more numerous and valuable the tributaries to the main course, the greater the volume of the stream and the more varied and extensive its influence.

One or two examples drawn from European rivers will more fully explain this point, to which Buache has already called attention in his “Parallèle des fleuves.”

The mouth of the Volga is 982 miles distant from the source, in an air-line. The distance, including all the curves of the stream, is 2012 miles, the bendings adding 1028 miles to the direct course. By this doubling of the shortest possible distance, the area drained by it is swollen to the enormous size of 657,000 square miles. The direct course lies in a diagonal direction from northwest to southeast; but the real direction is a changing one. First, it flows a short distance from north to south, then in its middle course it has a double direction; first eastward, toward the Ural chain, then to the south, and lastly, in its lower course, to the southeast. Through this varied course it receives tributaries from very remote sources, and waters a country altogether greater than would be possible if the Volga’s course were direct from the source to the mouth. Its basin becomes so large as to embrace a fifth of Europe, and the stream becomes one of the longest and most available for navigation in the continent. The vastness of the volume of water and the wandering course have both contributed to the value of the Volga lowlands.

The exact contrast to the Volga is found in the Dniester. In the Volga there is a maximum of windings; in the Dniester there is a minimum. The air-line distance of the mouth of the Dniester from the source is 408 miles; the distance, including all the bends, is 450 miles; the loss in winding is, therefore, but about 42 miles. The theoretical course of the Dniester, _i.e._ measured by an air-line, would coincide very nearly with its actual course. There cannot be, therefore, any distant springs whose waters flow into its channel; its basin is one of the most contracted in the world in consequence of its directness; and a small belt, embracing but 32,850 square miles, comprehends the entire district that it drains, freed from all those tributaries which make the Volga basin so important.

The Dnieper, its eastern neighbor, is 630 miles in direct distance from the source to the mouth, but 1000 with all its windings; leaving 370 miles as the extraneous shore, which adds to the value of the basin, and contributes to the 219,000 square miles which it drains.

The same contrast is seen elsewhere, though not on so extended a scale. It is to be found in the Vistula, Oder, Elbe, Weser, Rhine, and Danube. These rivers give shape to the transition terraces between broad eastern Europe and the more contracted western portions of the continent; their dimensions are, therefore, on a less extensive scale than in the great Russian streams. Still, the differences in them are worthy of notice.

In the Vistula, the direct distance from the source to the mouth is 329 miles, and the real distance is 611 miles; the windings comprise, therefore, 280 miles, or about two-thirds of the air-line from extreme to extreme. It becomes able to receive a large number of tributaries, and its basin is enlarged to an area of 78,402 square miles, becoming one of the best-watered and most fruitful on the globe.

In the Oder, the direct distance from the source to the mouth is about the same as in the Vistula. But while the latter frequently changes its course, running first northward, then eastward to the Sau, then northward again to the Bug, then westward to the Drewenz, and lastly northward, and so gains a very large basin of drainage, the former is unvarying in its course from southeast to northwest; so that the direct line drawn from extreme to extreme, as the bird flies, is nearly coincident with the actual course of the river. The windings do not, at most, comprise one-third of the whole length of the stream, and the basin drained by its tributaries is at least a third less than that of the Vistula, and is proportionately less valuable to the interests of the world.

In the Elbe the air-line length is 394 miles, greater therefore, than that of the Vistula or the Oder; its length, including its windings, is about the same as that of the Vistula. The area of its basin lies therefore between the two, 61,320 square miles; it is more valuable, therefore, than that of the Oder, and less valuable than that of the Vistula.

Still less striking in this respect are the Weser and the Ems; but the Rhine assumes a prominence, in relation to the value of its basin, greater than even the Vistula. The direct distance from the source of the Rhine to its mouth is 423 miles, the actual distance 705 miles; the windings comprise, therefore, more than two-thirds of the entire length of the stream. The number of tributaries is uncommonly large, the area drained is increased about 9855 miles beyond that of the Vistula; and the entire basin (88,257 square miles) is one which has been of the greatest import in the history of all central Europe.

All the rivers and all the terrace lands of the globe exhibit the same relation which we have been briefly indicating in a few European ones; in some of the great rivers of the world they are to be traced on a scale of grandeur of which in those which have been touched upon scarcely a suggestion is given.

But not in this feature, added to what has been already said, do we exhaust the fruitful subject of Rivers, and the terrace systems which accompany them from their source to the sea. The diversity of phenomena traceable in them had hid their unity from geographers, and prevented their tracing general principles in so manifold details. The dry, linear representations on most of our maps have blinded the eye to the living and organic relations which river systems enter into, and through which they exert a great influence. They must be examined singly; they must be studied in their real character and individuality, and each must have its own monograph, before we can fully know the value of river systems to the world.

We have now to touch upon one or two points omitted, thus far, in our discussion of the hydrography of the continents.

The stream is a unit; most streams have a single channel as the last goal of their descent. Others may have double channels, which contend with each other for the superiority. If they are double only for a part of the whole length of the river, and in the upper or middle course flow together, and form one main channel, they can be called twin head-streams. We have an example in the Danube and Inn, which are equally long and equally large. Other instances are the Rhone and the Saone, the Volga and Kama, the Missouri and Mississippi, the Blue and White Nile, the Ganga and Jumna. Others have triple head-streams; as, for example, the Hither, Middle, and Farther Rhine; the Ucayale, Huallaga, and Marañon, which combine in the middle course to form the Amazon. There may be even five head-streams, as in the Indus. Often it is only through the usage of speech, often through ancient and exploded errors, that the name of one of the head-streams is given to the whole river.

If the double channels continue through the whole length of the river system, they belong to a different category; they become true double systems, and have a double influence on the development of the whole range of terraces from source to base. From their meeting in a common bay or gulf at the mouth, they may be called sister-streams; and, from the territory which they inclose between them, the Mesopotamia, they may be called Mesopotamic streams. Between such double streams some of the greatest States of Asia lie. Universally known, on account of their influence on Asiatic culture, are the Euphrates and Tigris uniting in the Persian Gulf, Ganges and Brahmapootra uniting in the Bay of Bengal, Gihon and Sihon in the Sea of Aral, Hoang-ho and Yang-tse-Kiang encompassing the Central Flowery Country of the Chinese Empire, and meeting in a common delta. These double streams are mostly met in Asia, and they have exercised a great influence on the whole growth of oriental civilization.

In South America there is yet another and more complex form yet of river system. The Amazon is connected with the Orinoco by means of the little cross-river Cassiquiare. By this connection the middle course of both rivers is made more available to navigation than it would otherwise have been. Such cross-streams may be found, though on a smaller scale, in other continents; in Africa, for example, between the Senegal and the Rio Grande. There a network is made between the parallel rivers, but it is available for navigation only in the wet seasons. In Central Africa there seems to be a similar phenomenon between the eastern tributaries of Lake Tchad and the western tributaries of the Bahr el Abiad or White Nile, though this rests on the authority of the Arabs. In India there appears to be a similar connection between the middle course of the Indus and the Jumna, and so the Ganges, by the mediation of the Sarasvati or Histara and the Gharghara. There may have been the same in Central China, between the Hoang-ho and the Kiang, where the Imperial Canal now runs; and a similar feature may be found in the Lithuanian marshes, connecting the Vistula and Dnieper river systems, through the mediation of the Bug and the Przypec. The skill of man has, in many places, accomplished the same end by the construction of canals.

Although all rivers, in the course of their development, follow the universal law which leads them from their source, however high, to the sea, yet there is, even in their descent, scope for exceedingly varied phenomena. It is not necessary that everywhere a strongly-marked line of water-shed should exist, but often, as in all the more level plateaus, there are broad, neutral plains which perform the function of water-sheds, though possessing no decisive character. It is so through a great part of Central Asia, in the low plains of Australia, probably in a large part of Africa, and so markedly in America, that all lines of water-shed wholly disappear, and the rivers flow confusedly together, without any system, and in obedience to no law.

Some rivers come down the sides of high mountains in torrents, then course around in a long, winding course, turning out for all obstacles, and at last find the sea. Others are entirely unlike them. The Ganges flows from the south side of the Himalaya Mountains, and courses along their base, following the direction of the chain in a southeasterly direction, till it reaches the Bay of Bengal. The Indus springs from the north side of the Himalaya, flows northwest over the plateau of Little Thibet as far as Iskardo, then breaks through the whole chain to pour itself out upon the lowlands of India, the Punjaub, and Mooltan. Dashing its way through the most formidable barriers, it is entirely unlike the gentle Ganges, which pursues its tranquil course through the plains, meeting no barrier in its entire length. The Indus, so long as it remains north of the Himalaya, traverses a plateau 10,000 feet above the sea; while the Ganges, even at Delhi, is but 1000 feet above the sea. Both rivers, although represented in precisely the same way upon the maps, have an entirely different physical character.

The same difference in structure occurs in the streams of other continents, and even in those of Central Europe, though on a less colossal scale. There are, therefore, classes of rivers, and they ought to be just as sharply discriminated as the classes in botany and zoology.

Plateau streams, such as the Danube, as far as the Lower Austrian and Hungarian plains, and the Saone, down to its confluence with the Rhone, pass through high, uniform plains with little fall. They are genuine mountain followers, springing from the verge of the chain and crossing along its base, the Saone taking the west side of the Alps, as the Danube does the northern, and the Po the southern.

The rivers which force their way through mountain ranges form a second class. The Rhine, a free child of the Alps, from its source to the sea, breaks through all the ranges up to the Jura; then it forces a path through all the mountains of Central Germany, till it comes to its lower course. It may, therefore, be classified with the Indus. It leaves the Alps suddenly at Bâle, and opens a new and romantic way through no insignificant obstacle, and is everywhere a conqueror. That is the peculiarity of the Rhine.

Two streams of analogous nature, though less marked in their characteristics, are the Elbe and the Weser. But these both rise, not among the Alps, but amid the German mountains. They lack, therefore, the exceedingly romantic character of Alpine rivers; but they do not lack in picturesque scenery, and this they owe to the obstacles which they pass. The Elbe has broken its way from the Bohemian ridge through the so-called Saxon-Switzerland, as far as Meissen, and the Weser from the fissures of the Werra and the Fulda to the Porta Westphalica. The Elbe and the Weser make, with the Rhine, the triad of Central European rivers, which have broken a pathway for themselves through mountains which impeded their course.

A third class of rivers are those which encounter no obstacles, and flow in a placid stream from the source to the mouth. They extend in Europe from the Vistula to the Ems, including the Oder and excluding the Weser and Elbe, and from the Rhine along the whole Atlantic coast of France, embracing the Seine, Loire, Garonne, and the Adour—all of these having, in greater or less degree, the same hydrographical character.

From these can be still further discriminated the subordinate coast rivers.

To a fourth class belong all those tributary streams, of whatever size or length, which agree in possessing no independent character, and do not pour their waters into the sea through their own mouths.

The application of this system of classification can be applied to the streams and their accompanying terrace lands in the other continents. But these observations may suffice to indicate the general principles which we would apply to the study of rivers, and leave to the student their further application.

Review.

The great typical forms already considered, highland, plateau, mountain, lowland, terrace, and river, which all claim so large a share of attention in studying their physical characteristics, are no less worthy of careful attention, in consequence of their influence on human culture. Our account would not be complete without devoting a few pages to the consideration of the manner in which nature and history have reacted on each other.

The most elevated highlands, the loftiest plateaus, uniform in their aspect, immense in their extent, isolated, without trees, having the thin soil characteristic of steppes, and useful only for grazing, are the home of the primitive nomadic races. Without forests and without shelter, without valleys and without water-courses, with sandy and rocky soil, covered with a scanty vegetation, they serve only to supply food for the gregarious animals which follow man, and to furnish a home to wandering tribes of herdsmen. Instances are found in Central Asia, in Toorkistan and Persia, in Central Africa, including the Galla tribes and the Abyssinians. So, too, among the high plateaus of America, the home of the primitive Aztecs. From such places came the first movements of emigration; from the high plateaus of Central Asia came the wandering Persians, Huns, Mongolians, and Turks; and the same course of emigration was witnessed among the negro tribes of Central Africa, proceeding from the Galla tribes. The lower highlands, less colossal in size, of more moderate height, and of more genial temperature, have at all times reached a certain low stage of culture, after giving a home to the nomads from the higher plateau; but have never developed that culture to any considerable extent. We find examples of this in the high terraces of Bootan, the Deccan, and Persia; in Africa, among the Atlas mountains; in Abyssinia, in the ancient Greek Arcadia, in Castile, in Arvernia, (Auvergne,) in Gallia, in Hesse, in the Eifel, and on the Valdai hills.

In the exceedingly complex, subdivided, and romantic mountain districts of the globe, the races have attained, by virtue of the variety of their resources and the energy of their stock, to the highest results of civilization, and have manifested the most independent and progressive spirit. In such regions, hunting, working in wood, the settled life of shepherds, working in metals, agriculture on such terrace lands as those of Nepaul, Cashmere, Palestine, the Lebanon, Apennine, and other ranges, fruit culture, tilling vineyards, the cultivation of all kinds of industry, as in Central Germany and in most regions of the temperate zone, develop most thoroughly and speedily the culture of a people. In such occupations men learn to lean more on each other, and grow into that diversity of occupation and division of labor, which are the latest results of civilization. The Zend, the Sanscrit, and the Persian nations which people the fertile tracts at the base of the Himalaya Mountains, from Maghada, Lahore, Nepaul, and Cashmere, as far as Persepolis and Hamadan, Susa and Shiraz, the inhabitants of the hill country of Palestine and Syria, those of the Tehama range of mountains in Arabia, those in the moderately elevated meadows of Gondar, as well as those in all the European Alpine lands, Switzerland, Tyrol, Styria, as well as the inhabitants of the mountain region of Peru and Mexico, all attain to an early and considerably advanced state of civilization. Other nations have found in mountains asylums in time of danger—the Tsherkeses and Ossetes among the Caucasus, for instance, the Basques among the Pyrenees, and the Gorals among the Carpathians.

The lowlands, as soon as the water had left them enough to make them habitable, have become, from the first, the abodes of a teeming population; and there has been the same blending of races in the most ancient as in the most recently settled, in China as in Texas, and, in truth, all North America. Often these inroads of population have been a source of injury, as has been the case in the northern Siberian plains, where the Finnish tribes have made their homes, and in the waste of Sahara, where the Barbary tribes, the Bedouins, the Tibboos, and the Tuaricks have made their retreat.

On the fruitful terraces, along the middle course of rivers, the earliest fixed habitations and ripened culture have been attained. Through the traditional handing down of past results, and by the habits of peace, their inhabitants have more thoroughly subjected nature and advanced to a higher state of civilization than the dwellers in the interior, away from the rivers. It has been the same, in a great measure, with the lower course, as, for instance, in Egypt, Mesopotamia, China, and Bengal; and in Europe, in Lombardy, Holland, and the Netherlands, where, to the efforts to recover land from the sea, have been added fishing and commerce. On such fruitful tracts as the mouths and middle courses of rivers water, nations could find a permanent home, and pass quickly to all liberal and refining arts and occupations. This is clear, from the instances of the eminent monarchies of the East, Meroe, Thebes, Memphis, Babylon, Nineveh, Bagdad, and Mosul. So, too, on the Indus and Ganges, in the domains of Taxila, Maghada, Benares; and later in the great empire, whose centers were Agra and Delhi. China has arrived at its highest civilization in the fertile district between its two greatest rivers. Greece and Rome are marked exceptions. Their progress they owe, not to great river basins, but to their peninsular form in the middle of the coast of a delightful sea, full of islands and surrounded by lands in a greater or less advanced state of civilization. England’s peculiar maritime position has given it its wonderful vantage-ground for progress in all human culture.

In the east of Europe, the basins of rivers have exercised the same influence, to a certain extent, that has been hinted at above; and Moscow, Kiev, Cracow, and Warsaw remain the seats of a civilization which, rude as it was, owed its existence to the physical conditions of the great Sarmatian river systems. In western Europe, the less marked features of the country have contributed to the peculiar historical development of the continent. The rich deltas have become the granaries for a large part of the population, allowing industry to flow into other channels besides agriculture. The sea-faring habits of the people along the coast have broken up and done away with what is special and provincial, and have conferred a cosmopolitan manner of living upon the entire population. It was the same with the Phenicians in ancient times, with the Portuguese in the middle ages, as it has been with the English, Spanish, and Dutch in modern days. Fishing, navigation, and trade have become permanent necessities of civilization. In the heart of continental Europe, the rivers have had a great influence on the progress of nations; the North German streams have extended their effect from the abode of the ancient Saxons along the Baltic as far as the home of the Salic Franks on the Scheldt, Seine, and Loire; the Danube, with its complex and important system of terraces and lowlands, has opened communication between South Germany and Hungary, Wallachia, and the East. The Vistula, Oder, Elbe, and Weser have connected the homes of the old Sclavic population with the Scandinavian coasts and the land of the Angles and Saxons at the neck of Denmark, to the equal advantage of both. The great terrace system of the Rhine, embracing the Odenwald, Hardt, Spessart, Taunus, Hundsrück, Eifel, and the Siebengebirg, has thrown into the most active industrial and commercial relations the whole district which it waters. It opened a way to the Romans in their conquering advances before it did to the tribes of Helvetia, Gallia, Germania, or the Lowlands: it sundered those tribes, and kept them from preying upon each other; but, in the advance of civilization, it has become one of the strongest bands to knit together the central countries of Europe.

The Danube, with its extensive terrace lands, faces the east, and has, therefore, very different relations to European history from the Rhine. It is a double-headed river, and one of its head-streams, the one which bears the name of the river proper, extends almost to the Rhine basin; while the other, the Jura, has its source in Grisons, and hard by the head-waters of the Rhine. As the Danube connects the Caspian and Black Sea basin with western Europe, and the largest part of the Asiatic immigrations have followed its course, the Danube has become the great avenue between Europe and Asia. Celts, Teutons, and Romans were mingled even before Christ, in Noricum, Vindelecia, Bavaria, and Suabia. How many tribes may have been crowded westward by these, is unknown to us. The same fate has happened to the people who settled there before Christ, and the inroads of the Huns, Goths, and other tribes of similar origin, scattered the older inhabitants over all Central Germany. We know, too, that Sclavic, Hungarian, and Turkish incursions followed, each one dispossessing wholly or in part the one which preceded it.

All great rivers and river systems have had a similar influence on the course of civilization. There is not a single type feature in the world which has not contributed its part to the advance of the human race; no one is without its place and its function.