The form of mountains is also very different: some form chains whose height is nearly equal in a long extent of soil, others are divided by deep vallies; some are regular, and others as irregular as possible; and sometimes in the middle of a valley or plain, we find a little mountain. There are also two sorts of plains, the one in the low lands, the other in mountains. The first are generally divided by some large river: the others, though of a very considerable extent, are dry, and at farthest have only a small rivulet. These plains on mountains are often very high, and difficult of access; they form countries above other countries, as in Auvergne, Savoy, and many other high places: the soil is firm, and produces much grass, and odoriferous plants, which render these plains the best pasture in the world. The summits of high mountains are composed of rocks of different heights, which resemble from a distance the waves of the sea. It is not on this observation alone we can rely that the mountains have been formed by the waves, I only relate it because it accords with the rest: but that which evidently proves that the sea once covered and formed mountains, are the shells and other marine productions found throughout in such great quantities, that it is not possible for them to have been transported by the sea into such remote continents, and deposited to such considerable depths; to this may be added, the horizontal and parallel strata every where met with, and which can only have been formed by the waters. The composition even of the hardest matters, as stone and marble, prove they had been reduced into fine powder before their formation, and precipitated to the bottom of the water in form of a sediment: it is also proved by the exactness with which fossil-shells are moulded in those matters in which they are found; the inside of these shells are absolutely filled with the same matters as that in which they are enclosed; the corresponding angles of mountains and hills, which no other cause than the currents of the sea could have been able to form; the equality in the height of opposite hills, and beds of different matters, formed at the same levels, and, in short, the direction of mountains, whose chains extend in length in the same direction as the waves of the sea extend, incontestibly demonstrate the fact.