The motions of the sea are therefore the principal causes of the alterations which have happened, and which daily happen on the surface of the globe. But there are many, other causes, which, though less considerable, contribute to those changes. Running waters, rivers, streams, the melting of snow, torrents, frosts, &c. have occasioned many changes; the rains have diminished the height of mountains; rivers and rivulets have raised plains, and stopped up the sea at their mouths; the melting of snow, and torrents, have dug hollows in vallies; and the frosts have split rocks and separated them from their former stations. We might quote an infinity of examples on the alterations these causes have occasioned. Varenius says, that rivers convey into the sea great quantities of earth, which they deposit at a greater or less distance from the coasts, according to the rapidity of their currents; these earths fall to the bottom of the sea, and, at first, form those small banks which daily encrease, become shoals, and, at last, form islands, which are fertile and inhabitable. This is the manner in which the islands of the Nile are formed, as well as those of St. Laurence, the Isle of Landa, situate on the coast of Africa, near the mouth of the river Coanza, the island of Norway, &c.[AZ] To these may be added the island of Trong Ming, at China, which has been gradually formed by the earth that the river Nankin has brought and deposited it at its mouth. This island is more than 20 leagues long by five or six broad.[BA]
[AZ] See Varenni Geograph. page 214.
[BA] See Letters Edifiantes, Recueil xi. page 234.
The Po, Trento, Athesis, and other rivers of Italy, bring with them great quantities of earths into the lakes of Venice, especially during the time of inundations, which, in course of time, must fill them up. In many places they are now dry at low water, and, excepting the canals, which are kept up at a great expence, have no depth of water.
At the mouths of the Nile, the Ganges, the Indus, the Plata, the Nankin, and of many other rivers, the earth and sand deposited form considerable banks. Loubere, in his Voyage to Siam, says, that the banks of sand and earth daily increase at the mouths of the great rivers of Asia, insomuch that the navigation of them becomes every day more difficult, and will one day be impassable. The same remark may be made of the large rivers of Europe, and particularly of the Wolga, which has more than 70 mouths in the Caspian sea, and of the Danube, which has seven in the Black sea, &c.
As it seldom rains in Egypt the regular inundations of the Nile proceed from the torrents which fall therein from Ethiopa. These annually bring with them great quantities of mud, which they not only deposit on the land of Egypt but even throw to a considerable distance in the sea, and thus lay the foundation of a new land, which, in the course of time, arises therefrom; for, by sounding with the lead, we find, at more than 20 leagues distance from the coast, the mud of the Nile at the bottom of the sea, and which is every year increasing. Lower Egypt, where[BB] Dela at present stands, was formerly a gulph of the sea. Homer tells us that the island of Pharos was 24 hours voyage from Egypt, and at present it is almost contiguous to it. The soil of Egypt has not the same depth of good ground throughout its extent, it lessens as we approach the sea. Near the borders of the Nile there is sometimes near thirty feet depth of good earth, whereas at the extremity of the inundation there is scarcely more than seven inches.[BC] The town of Damietta, at present more than 10 miles from the sea, in 1243 was a sea-port. The town of Fooah, which, 300 years ago, was situate at the mouth of the Canopic, a branch of the Nile, is now more than seven leagues from it. Within 40 years the sea has retreated half a league from before Rosetta and Idern.
[BB] See Diodorus de Suc, lib. 3. Aristotle, lib. 1. of Meteors, h. xiv. Herodotus, f. 4, 5, &c.
[BC] See Shaw's Travels, vol. II. page 185, and 186.
The great rivers of America, and even those which have been but lately discovered, have suffered great alterations at their mouths. Charlevoix, speaking of the river Mississipi, says, that at its mouth, below New Orleans, the country forms a point of land which does not appear to be very ancient, for by digging but a little into the earth water is met with; besides, the quantity of small islands which have recently been formed at all the mouths of this river, leaves no doubt of this neck of land being formed after the same manner. It appears certain, says he, that when M. de la Salle went down the Mississipi, to the sea, the mouth of this river was not as it is at this present time.
"The nearer we approach towards the sea, adds he, the more it becomes perceptible, the bar has scarcely any water in most of the small outlets which the river has opened, and which have multiplied so greatly from the trees that are carried along with the currents, one of which stopt in a part where it is shallow, will entangle hundreds. I have seen, continues he, 200 leagues from New Orleans, collections of trees, one of which would have filled all the timber-yards of Paris. Nothing can set them free; the mud which the river brings down serves to cement, and, by degrees, covers them. Each inundation leaves a new stratum, and, after 10 years, shrubs and vegetables grow thereon: after this manner most points and islands are formed, which so often change the course of rivers."[BD]