The sea by its general motion from east to west must convey the productions of our coast to those of America; and it is by some irregular motions that the productions of the East and West Indies, as well as the northern climates, are brought upon our shores. There is a great appearance that the winds cause those effects; large spots have often been observed in the high seas, far from shore, covered with pumice-stones; they could only come from the volcanoes in islands or on the continent, and which the current had transported to the middle of the seas. Before the southern part of America was known, and in the time when the India Sea was thought to have no communication with our ocean, appearances of this kind afforded the first supposition of it. The alternative motion of the flux and reflux, and the constant motion of the sea from cast to west, presents different phenomena in different climates, according to the bearing of the land and the height of the coasts. There are parts where the general motion from east to west is not perceptible; there are others where the sea has even a contrary motion, as on the coast of Guinea. But these contrary motions are occasioned by the winds, by the position of the lands, by the waters of large rivers, and by the disposition of the bottom of the sea; all these causes produce currents which alter, and often change the general motion in many parts of the sea; but as the motion from east to west is the greatest, most general and constant, it must also produce the greatest effects, and all taken together, the sea must gain ground towards the west, and lose it towards the east; although it may happen that on those coasts where the west winds blow during the greatest part of the year, as in France and England, the sea may gain on the east, yet these particular exceptions do not destroy the effect of the general cause. ARTICLE XIII. OF THE INEQUALITIES AT THE BOTTOM OF THE SEA, AND OF CURRENTS. The coasts of the sea may be distinguished into three kinds, 1st, the elevated coasts, which are rocks and hard stones, generally divided perpendicularly, and which rise sometimes to the height of 7 or 800 feet. 2d, The low coasts, some of which are almost level with the surface of the water, and others rising with a moderate elevation, often bounded by rocks at the water's edge, forming shelves and breakers, which render the approach to shore very difficult and dangerous. 3dly, Downs, which are coasts formed by sand which the sea accumulates, or brought or deposited by rivers; these downs form hills more or less elevated, according to the accumulated sand.