4. What influence have living bodies exerted on the substances found on the surface of the earth and which compose the crust which invests it, and what are the general results of this influence? Lamarck then disclaims any intentions of framing brilliant hypotheses based on supposititious principles, but nevertheless, as we shall see, he falls into this same error, and like others of his period makes some preposterous hypotheses, though these are far less so than those of Cuvier's _Discours_. He distinguishes between the action of rivers or of fresh-water currents, torrents, storms, the melting of snow, and the work of the ocean. The rivers wear away and bear materials from the highlands to the lowlands, so that the plains are gradually elevated; ravines form and become immense valleys, and their sides form elevated crests and pass into mountain ranges. He brings out and emphasizes the fact, now so well known, that the erosive action of rain and rivers has formed mountains of a certain class. "It is then evident to me, that every mountain which is not the result of a _volcanic irruption_ or of some local catastrophe, has been carved out from a plain, where its mass is gradually formed, and was a part of it; hence what in this case are the summits of the mountains are only the remains of the former level of the plain unless the process of washing away and other means of degradation have not since reduced its height." Now this will apply perfectly well to our table-lands, mesas, the mountains of our bad-lands, even to our Catskills and to many elevations of this nature in France and in northern Africa. But Lamarck unfortunately does not stop here, but with the zeal of an innovator, by no means confined to his time alone, claims that the mountain masses of the Alps and the Andes were carved out of plains which had been raised above the sea-level to the present heights of those mountains. Two causes, he says, have concurred in forming these elevated plains. "One consists in the continual accumulation of material filling the portion of the ocean-basin from which the same seas slowly retreat; for it does not abandon those parts of the ocean-basin which are situated nearer and nearer to the shores that it tends to leave, until after having filled its bottom and having gradually raised it. It follows that the coasts which the sea is abandoning are never made by a very deep-lying formation, however often it appears to be such, for they are continually elevated as the result of the perpetual balancing of the sea, which casts off from its shores all the sediments brought down by the rivers; in such a way that the great depths of the ocean are not near the shore from which the sea retreats, but out in the middle of the ocean and near the opposite shores which the sea tends to invade.