Gneiss, he thinks, resulted from the detritus of granitic rocks, by means of an inappreciable cement, and formed in a way analogous to that of the porphyries.
Then he attacks the notion of Leibnitz of a liquid globe, in which all mineral substances were precipitated tumultuously, replacing this idea by his chemical notion of the origin of the crystalline and volcanic rocks.
He is on firmer ground in explaining the origin of chalk and clay, for the rocks of the region about Paris, with which he was familiar, are sedimentary and largely of organic origin.
In the "Addition" (pp.

173-188) following the fourth chapter Lamarck states that, allowing for the variations in the intensity of the cause of elevation of the land as the result of the accumulations of organic matter, he thinks he can, without great error, consider the mean rate as 324 mm.

(1 foot) a century.

As a concrete example it has been observed, he says, that one river valley has risen a foot higher in the space of eleven years.
Passing by his speculations on the displacement of the poles of the earth, and on the elevations of the equatorial regions, which will dispense with the necessity of considering the earth as originally in a liquid condition, he allows that "the terrestrial globe is not at all a body entirely and truly solid, but that it is a combination (_reunion_) of bodies more or less solid, displaceable in their mass or in their separate parts, and among which there is a great number which undergo continual changes in condition." It was, of course, too early in the history of geology for Lamarck to seize hold of the fact, now so well known, that the highest mountain ranges, as the Alps, Pyrenees, the Caucasus, Atlas ranges, and the Mountains of the Moon (he does not mention the Himalayas) are the youngest, and that the lowest mountains, especially those in the more northern parts of the continents, are but the roots or remains of what were originally lofty mountain ranges.

His idea, on the contrary, was, that the high mountain chains above mentioned were the remains of ancient equatorial elevations, which the fresh waters, for an enormous multitude of ages, were in the process of progressively eroding and wearing down.
What he says of the formation of coal is noteworthy: "Wherever there are masses of fossil wood buried in the earth, the enormous subterranean beds of coal that are met with in different countries, these are the witnesses of ancient encroachments of the sea, over a country covered with forests; it has overturned them, buried them in deposits of clay, and then after a time has withdrawn." In the appendix he briefly rehearses the laws of evolution as stated in his opening lecture of his course given in the year IX.