mous 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 extinct 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 greywacke 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 Khrebet ranges, running to the north-east-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, and 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 civilisation, since rivers flow from them in all directions; while from the Himalayas they flow only 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.

It

The surface of plateaus is exceedingly varied. 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 Turkestan and Gobi, including the river Tarim, and reaching its greatest depression at Lake Lop, or, like the plateau of Afghanistan, including the river Helmund and Lake Seistan; again, we have plateaus traversed by watercourses which force their way in times of flood, and leave in the rainless season the traces of their 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 Turkestan and Persia on the west, and toward Lakes Baikal and Zaizan 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 1100 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 combination 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 Kashgar to Lake Lop, yet displays such immense districts of plateaus of 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 mountainchain, 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 south-eastern 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 pro

visional 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 swollen with confined gases, and with depressions here and there as if, in the casting out of the molten mass within,