For supposing, as it is easy to prove by the marine productions we find there, that the chain of the Alps was formerly covered by the sea, and that above this chain there was a great thickness of vitrifiable sand, which rendered the whole mountains a flat and level country. In this depth of sand, there would necessarily be formed granite, free-stone, flint, and all matters which take their origin and figure in sand, nearly in a similar manner to that of the crystallisation of salts. These blocks once formed would support their original positions, after the rains and torrents had carried away the sand which surrounded them, and being left bare formed all those peaks or pointed eminences we see in so many places. This is also the origin of those high and detached rocks found in China and other countries, as in Ireland, where they are called the Devil's stones, and whose formation as well as that of the peaks of mountains, had hitherto appeared so difficult to explain; nevertheless the explanation which I have given is so natural, that it directly presents itself to the mind of those who examine these objects, and I must here quote what Father Tatre says, "From Yanchu-in-yen, we came to Hoytcheou, and on the road met with something particular, rocks of an extraordinary height, of the shape of a large square tower, and situate in the midst of vast plains: I cannot account for it, unless by supposing they were formerly mountains, from which the rain having washed away the earth that surrounded them, thus left the rocks entirely bare. What strengthens this conjecture is, that we saw some which, towards the base, are still covered with earth to a considerable height." The summits of the highest mountains are composed of rocks, of granite, free-stone, and other hard and vitrifiable matters, and this often as deep as two or three hundred fathoms; below which we often meet with quarries of marble, or hard stone, filled with fossil-shells, and whose matter is calcinable; as may be remarked at Great Chartreuse, in Dauphiny, and on Mount Cenis, where the stone and marble, which contains shells, are some hundred fathoms below the summits, points and peaks of high mountains; although these stones are more than a thousand fathom above the level of the sea. Thus mountains, whereon we see points or peaks, are generally vitrifiable rock, and those whose summits are flat, mostly contain marble and hard stones filled with marine productions. It is the same with respect to hills, for those containing granite, or free-stone, are mostly intersected with points, eminences, cavities, depths, and small intermediate valleys; on the contrary, those which are composed of calcinable stone are nearly equal in height, and are only interrupted by greater and more regular vallies, whose angles are correspondent; and they are crowned with rocks whose position is regular and level.