It may be proper to give a view of the operations of nature upon the Apennines. It is from an account of a journey into the province of Abruzzo, by Sir William Hamilton. Phil. Trans. 1786.
The road follows the windings of the Garigliano, which is here a beautiful clear trout stream, with a great variety of cascades and water-falls, particularly a double one at Isola, near which place CICERO had a villa; and there are still some remains of it, though converted into a chapel. The valley is extensive, and rich with fruit trees, corn, vines, and olives. Large tracts of land are here and there covered with woods of oak and chestnut, all timber trees of the largest size. The mountains nearest the valley rise gently, and are adorned with either modern castles towns, and villages, or the ruins of ancient ones. The next range of mountains, rising behind these, are covered with pines, larches, and such trees and shrubs as usually abound in a like situation; and above them a third range of mountains and rocks, being the most elevated part of the Apennine, rise much higher, and, being covered with eternal snow, make a beautiful contrast with the rich valley above mentioned; and the snow is at so great a distance as not to give that uncomfortable chill to the air which I have always found in the narrow valleys of the Alps and the Tyrol.
Having thus examined the alpine countries both of the Old World and the New, it remains to observe some river in a more low or level country emptying itself into a sea that does not communicate with the ocean. The Wolga will now serve for this purpose; and we shall take our facts from the observations of those men of science who were employed by their enlightened Sovereign to give the natural as well as the economical history of her dominions.
Russia may be considered as a square plain, containing about 40 degrees of longitude, and 20 of latitude, that is, between the 47° and 67° degrees. The east side is bounded by the Oural mountains, running in a straight line from north to south. The west is bounded by Poland. The south reaches to the Caspian and Black Seas, as does the north to the Polar Ocean.
The greatest part of the water which falls upon this extensive country is delivered into the Caspian by the river Wolga; and this water runs from the east and west sides, gathered in two great rivers, the Kama and the Oka. The water thus gathered from the two opposite extremities of this great kingdom meet in the middle with the Wolga, which receives its water from the north side. We thus find the water of this great plain running in all directions to its centre. Had this been the lowest place, here would have been formed a sea or lake. But this water found a lower place in the bed of the Caspian; and into this bason it has made its way, in forming to itself a channel in the great plain of the Wolga.
Our present purpose is to show that this channel, which the Wolga has cut for itself, had been once a continued mass of solid rock and horizontal strata, which in the course of time has been hollowed out to form a channel for those waters. These waters have been traversing all that plain, and have left protuberances as so many testimonies of what had before existed; for, we here find the horizontal strata cut down and worn away by the rivers.
M. Pallas gives us very good reason to believe that the Caspian Sea had formerly occupied a much greater extent than at present; there are the marks of its ancient banks; and the shells peculiar to the Caspian Sea are found in the soil of that part of its ancient bottom which it has now deserted, and which forms the low saline Steppe. He also makes it extremely probable that the Caspian then communicated with the Euxine or Black Sea, and that the breaking through of the channel from the Euxine into the Mediterranean had occasioned the disjunction of those seas which had been before united, as the surface of the Caspian is lowered by the great evaporation from that sea surrounded with dry deserts.
However that may he, it is plain, that throughout all this great flat inland country of Russia, the solid rocks are decaying and wearing away by the operation of water, as certainly, though perhaps not so rapidly, as in the more mountainous regions of the earth.
If there is so much of the solid parts worn and washed away upon the surface of this earth, as represented in our Theory; and if the rivers have run so long in their present courses, it may perhaps be demanded, Why are not all the lakes filled up with soil; and why have not the Black and Caspian Seas become land or marshy ground, with rivers passing through them to the ocean? Here is a question that may be considered either as being general to all the lakes upon the earth, or as particular to every lake which should thus find a proper explanation in the Theory. With regard to the last of these, the question has already been considered in this view, when the particular case of the Rhône was taken as an example; and now we are only to consider the question as general to the globe, or so far as belonging to the Theory, without particularising any one case.
It must be evident, that the objection to the Theory, here supposed to be made, is founded necessarily upon this, that the solid basis of our continent, on whose surface are found the lakes in question, is preserved without change, because, otherwise, the smallest variation in the basis may produce the most sensible effects upon the surface; and in this manner might be produced dry land where there had been a lake, or a lake where none had been before. But, as the present Theory is founded upon no such principle of stability in the basis of our land, no objection, to the wasting operations of the surface of the earth, can be formed against our Theory, from the consideration of those lakes, when the immediate cause of them should not appear.