Cordilleras or Andes; in Europe they are rare, but in Tartary, Persia, and in central Africa, they occur, forming regions of great extent. In general, the greater part of the mountains of a continent appear to have a connexion more or less obvious; it has even been conceived that they form the skeleton upon which the rest of the land has been deposited, and which has determined the form of the continent. Thus we speak habitually of chains of mountains. Mountains, however, do not always present a continuous ridge, from which the peaks or more elevated summits rise, but occasionally, the groups we call chains, are composed of separate mountains divided by valleys; such are the mountains of Scotland, of Sweden, and Norway; and such is the general structure of the chain of mountains called in the state of New-York the Highlands, of whose connexion and grouping we shall hereafter speak. This being understood, namely, that by a chain or ridge of mountains we do not necessarily intend a continuous elevation, the term may be conveniently used in order to express the configuration of mountains. These chains surround or border upon greater or less basins, which are each distinguished by the name of the principal stream that conveys its surface waters to the ocean, or they may, as has been stated, envelop a table land, whence there is no issue for the waters, or no more than a mere passage sufficient to afford them an outlet. Even if a map contain no expression of the position of mountains, we can, by mere inspection of the courses of rivers, determine the lines in which the chains are directed, and, from the size of the rivers, judge in some measure of the elevation of the district. Thus, on inspection of the map of Europe, we find four of its greatest rivers rising at no great distance from each other, the Rhine, the Rhone, the Danube, and the Po; here, then, we might infer a great elevation, and here we accordingly find its highest mountains, the Alps. In another part of this continent, we see the Dwina, the Nieper, and the Volga, diverge from points not far distant from each other, and here accordingly we find an elevated table land, two hundred miles in length by fifty in breadth, marked however by no mountain summits. In central Asia, we see a vast space inclosed by lines joining the sources of a number of mighty rivers, the Indus, the Ganges, the Barrampooter, the Irrawaddy, the Houng Ha, and Kiang Ku, the Amour, the Lena, the Yermisir, and the Oby; accordingly, here we find the greatest table land surrounded by the highest mountains of the globe. Still, however, the instance we have cited of the rivers of Russia shows, that the land whence great rivers take their rise, is not necessarily mountainous; in this case the ascent is almost imperceptible, and the summit offers the aspect of a level and marshy plain. Such also occurs in the famous boundary be tween the United States and Canada, where the highlands that figured in two successive treaties have disappeared, and in their supposed place has been found a series of swamps. Attempts have been made to arrange the chains of mountains into connected systems. Of these the most successful is that of Malte-Brun. "If we draw a line from the centre of Thibet, across Chinese Mongolia towards Ochotsk, and thence towards Cape Tehutscki, the eastern promontory of Asia, this line will in general coincide with a great chain of mountains which runs from the south-west to the north-east, and which every where descends rapidly towards the Indian and Pacific oceans, while on the contrary, it extends itself towards the Frozen ocean in high plains and secondary hills. It is probable that we may some day refer to the same rule the chain of Lapata, called the backbone of the world, in Africa; at any rate this chain runs from the Cape of Good Hope to that of Gardafui, in a direction south-east and north-west, and therefore in nearly the same direction as the great chain of Asia, but we are ignorant of the disposition of the slopes of these mountains. We may regard the mountains of the Happy Arabia, which are both steep and lofty, as the link that connects the mountains of Lapata with the table lands and mountains of Persia, which proceed from the mountains of Thibet. "If we follow the western coasts of America, from Behring's straits, which hardly form a sensible interruption, to Cape Horn, we find an uninterrupted chain of mountains. From time to time this chain retires a little into the interior, but more frequently it immediately borders upon the great ocean, in immense cliffs, and often by frightful precipices. On the other side of it, the manner in which the lakes discharge themselves, and the direction of the great rivers, show sufficiently, that the surface of America inclines gently towards the Atlantic ocean. "It results from a combination of these observations, that the greatest chains of mountains on our globe, are ranged in an arc of a circle around the great ocean, and the sea of India; that they seem to present rapid descents towards the immense basin they surround, and gentle slopes on their opposite sides; in fine, from the Cape of Good Hope to Behring's straits, and thence to Cape Horn, the eye of the most timid observer cannot fail to see some trace of an arrangement, as surprising from its uniformity, as from the vast extent of ground which it embraces. "Let us pause for an instant to consider this great fact of physical geography. If we conceive ourselves placed in New South Wales, with our face turned towards the north, we have America on our right hand, Africa and Asia on our left. These continents, which we hardly before ventured to approach in our imagination, considered in this point of view, form a consistent system, whose structure, as far as we are acquainted with it, presents in its great features an astonishing symmetry. A chain of enormous mountains surrounds an enormous basin; this basin, divided into two by a vast collection of islands, often bathes with its waves the feet of this great primary chain of the earth.” In this chain lie the greatest mountains of the globe. One peak of the Himmalayah rises nearly five miles above the level of the sea; another has a height of 25,500 feet; and a third of 22,217 feet. In South America are Soratu, in height 25,250 feet. Illimani, 24,000 not to mention Antisana, Mauflos, Chillau, Cotopaxi, all of which exceed in height any mountains that do not lie in this great system. Nay, did not the great Volcano of Owyhee enter into the order with a height of 18,000 feet, the list of those surpass ing the other mountains of the globe, might be very much extended. We shall have occasion hereafter to speak of the volcanic energies still exerted in this vast stony girdle, and shall therefore confine ourselves strictly to mere external form. The arms and branches of mountain chains enclose as has been seen, basins marked by rivers which convey their surface waters to the ocean. The rains which fall on the sides of mountains and hills, unite in torrents and streams, which follow the lines of most rapid slope in their course to the sea. The greater rivers mark the lowest part of a principal basin, on each side of which, at a greater or less distance, are to be found rising grounds, themselves hollowed out into lateral secondary basins, containing courses of water less considerable than the first, into which they cast themselves, and whose branches they are. The borders of these secondary basins are again hollowed out into basins of a third order, whose slopes also contain water courses less considerable than the preceding, into which they in turn discharge themselves. This ramification continues until we reach the smallest ravines of the boundary mountains, and the map appears, as it were, covered with a net work of rivers and lesser streams. The great valley of the Missisippi and Missouri, forms perhaps the most striking instance of this sort, upon the surface of our globe. Rivers and streams are constantly exerting a mechanical action on the surfaces over which they run; abrading and tearing off fragments even of the hardest rocks, they roll them in their course until the velocity becomes insufficient to transport them farther. At diminished velocities they move fragments of less size, down to the smallest pebbles; at still less velocities, they transport sand, and finally earthy matter, in the most minute division. These are deposited in succession in positions corresponding to the rapidity of the stream, and hence the beds of rivers present at each of their different sections, materials of magnitude and quality corresponding to the rate at which the stream usually flows. The increase in the magnitude of streams, due to violent rains and the melting of the snows, changes the position of the substances that compose their bed, and the more easily suspended materials are often held until the stream actually meets the ocean. In such sudden increases, the streams often overflow their usual banks, and make their deposits laterally, until the constant succession of such deposits raises the adjacent ground high enough to set bounds to the further spreading of the stream. This deposit is remarkable for its taking place in greatest quantity close to the usual bed of the stream; and thus it speedily opposes natural dykes to its own redundant waters. This action is most conspicu ous at points where marked changes take place either permanently or periodically in the rapidity of running water: when streams descend from mountains into lines of less descent, a deposit uniformly takes place, forming flats or intervals, as they are styled in the United States, of which we have such beautiful instances in the valleys of the Connecticut and Mohawk, and that part of the Hudson near Albany; again, where rivers meet the sea, they are interrupted in their course by the rise of the tides of the ocean, and here again deposits take place, sometimes forming shoals and banks in the ocean itself; at other times, bars and obstructions at their own mouths; and again, deltas of solid land, constantly encroaching upon the sea. This action, which is continually going forward, is called alluvial. The delta of greatest fame, and from which the others have derived their generic name, is that of the Nile; this we have evidence, almost historic, to prove to be wholly the gift of the river. And if it no longer increase as rapidly as in former ages, the cause is obvious, for the alluvion has been pushed so far forward as to meet a strong current that sweeps along the African coast, and must carry off much of the earth the Nile discharges into the Mediterranean. The great rivers of Asia and of America carry still greater quantities of solid matter, but we have not the same distant traditions to refer to for the amount of the increase they have caused; still, however, we know that the mouth of the Mississippi has been advanced into the Gulf of Mexico several leagues since the settlement of Louisiana; and that islands of great extent are frequently formed, in the course of a single year, by the deposits of the Ganges. We however find traces of aqueous action far more extensive and powerful than those which are now taking place under our eyes by fluviatile action. There is no part of the globe that has been examined, which does not show that it has been subjected to the action of water, in floods far more powerful than any we now are in the habit of seeing. Every where, except in the case of rocky cliffs, and steep mountains, or where we see obvious evidence of a recent elevation, we find the surface strewn with the deposits of water: boulders of greater or less size, beds of gravel, sand, and clay, form the present outer coating of the greatest part of the land. These deposits were long confounded with the alluvial, but have at length been proved, by incontrovertible evidence, to be the results of an action, which if not contemporaneous, must have been universal. We have seen an able attempt to show that this species of deposit did not take place at one and the same period, but was merely the general consequence of similar causes acting at different epochs. Our impression, we must however confess to be, that the action was not only co-extenve with the globe, but contemporaneous. It at any rate exhibits proofs the most satisfactory, that the last great and extensive change which our earth has undergone, was effected by the agency of water, in a state of rapid and violent motion. Ascribing this deposit to a single flood, it has been styled diluvial. There are cases where alluvial deposits rest upon the diluvium, and from the depth of these it has been attempted to calculate the time that has elapsed since the former of these actions was resumed. The diluvium has also been found in caverns lying upon an ancient stalagmite, and covered again with a new formation of that modification of carbonate of lime. The thickness of the latter deposit has also been made the basis of a calculation, and although neither of these methods is to be considered as approaching to an accuracy more perfect than some hundreds of years, the two methods confirm each other in the general result, which is, that, at a date not more remote than fifty or sixty centuries, there must have taken place a total submersion of all the land, except, perhaps, the tops of high mountains, did they then exist. We have in the sacred volume, a record of such a catastrophe, the flood of Noah, and from that time to the present, no convulsion, equally extensive in its influence, has devastated the globe. Have not then the geologists who have seen in these indications the convincing evidence of that occurrence, been warranted in their inference, of the identity of an event pointed out by undeniable physical evidence, with one recorded in a history to which one of the most confirmed sceptics has recently admitted the merit of truth? The diluvial deposits are found not only in the lower grounds, but on the tops and sides of lofty mountains; we have ourselves noted them distinctly characterized at high elevations upon the Kaatskills; they are found among the Alps at Valorsine, 6000 feet above the level of the sea, and in another place at more than 7000 feet. The excavations made in the extension of the city of New-York at Corlaer's Hook, have laid open a vast mass of diluvium, and afforded means for studying it with great facility. It in fact presented the appearance of a great cabinet of specimens of primitive and transition rocks, and it was possible in many cases to determine the very mountain whence the fragments had been torn. The most remarkable boulder, for instance, of a weight of at least an hundred tons, was distinctly recognisable as identical in every respect with the granitic syenite of Schooley's mountain, distant at least forty miles. Others had no known type nearer than Connecticut, in the opposite direction, while the gneiss and mica slate of the island of New-York, with their various embedded minerals, the serpentine and many of the magnesian minerals of Hoboken, with sandstone and trap of the Pallisadoe range, were distinctly recognisable. In this great excavation, where a region of a mile square was wholly |