When I had just finished my Theory of the Earth, which I composed in 1744, I received from Mons. Barrere, his dissertation on the origin of figured stones, and I was pleased to find myself of the same opinion with this able naturalist, on the subject of the formation of downs, and the time the water remained on the earth which we inhabit; he recounts many alterations which have happened to the sea coasts: "_Aiguis-mortes_, which is now more than a league and a half from the sea, was a port in the time of St. Louis: Psalmodi was an island in 815, and at present it is inland two leagues from the sea. It is the same with respect to Maguelone. The greatest part of the vineyards of Agde, was forty years ago covered by the sea: and in Spain the sea has considerably retreated within a short space of time from Blancs, Badalona, the mouth of the river Vobregat, Cape Tortosa, along the coasts of Valentia, &c. "The sea may form hills and mountains in many different manners; first, by the transportations of earth, sand, and shells, from one place to another; secondly, by depositing sediments, consisting of small particles detached from the coasts and bottom, and which it might have transported from a considerable distance; and lastly, by sand, mud, and other articles, which the sea winds often drive against coasts, downs and hills may be produced, which the water forsaking, by degrees, become parts of the continent." The downs of Flanders and Holland are of this kind, being only hills composed of sand and shells, which the sea winds have driven towards the land. Mons. Barrere quotes another example which merits a place in this work. "The sea, by its motion, detaches from its bottom an infinity of plants, shells, slime, and sand, which the waves and winds continually drive towards the shore. Now, all these different operations must continually form new strata, elevate the beds of earth, gradually raising downs and hills, retrenching the bounds of the ocean, and by that means extending the lands on the continents."