"This distinction is very important to make, because the consideration of fossils is, as we have already said, one of the principal means of knowing well the revolutions which have taken place on the surface of our globe. This subject is of great importance, and under this point of view it should lead naturalists to study fossil shells, in order to compare them with their analogues which we can discover in the sea; finally, to carefully seek the places where each species lives, the banks which are formed of them, the different beds which these banks may present, etc., etc., so that we do not believe it out of place to insert here the principal considerations which have already resulted from that which is known in this respect. "_The fossils which are found in the dry parts of the surface of the globe are evident indications of a long sojourn of the sea in the very places where we observe them._" Under this heading, after repeating the statement previously made that fossils occur in all parts of the dry land, in the midst of the continents and on high mountains, he inquires _by what cause_ so many marine shells could be found in the explored parts of the world. Discarding the old idea that they are monuments of the deluge, transformed into fossils, he denies that there was such a general catastrophe as a universal deluge, and goes on to say in his assured, but calm and philosophic way: "On the globe which we inhabit, everything is submitted to continual and inevitable changes, which result from the essential order of things: they take place, in truth, with more or less promptitude or slowness, according to the nature, the condition, or the situation of the objects; nevertheless they are wrought in some time or other. "To nature, time is nothing, and it never presents a difficulty; she always has it at her disposal, and it is for her a means without limit, with which she has made the greatest as well as the least things. "The changes to which everything in this world is subjected are changes not only of form and of nature, but they are changes also of bulk, and even of situation. "All the considerations stated in the preceding chapters should convince us that nothing on the surface of the terrestrial globe is immutable. They teach us that the vast ocean which occupies so great a part of the surface of our globe cannot have its bed constantly fixed in the same place; that the dry or exposed parts of this surface themselves undergo perpetual changes in their condition, and that they are in turn successively invaded and abandoned by the sea. "There is, indeed, every evidence that these enormous masses of water continually displace themselves, both their bed and their limits.