120 LAMARCK, HIS LIFE AND WORK 



actual maximum of this process of perfecting, the 

 limit {terme) of which, if it exists, cannot be known." 



In the fourth chapter of the book there is less to 

 interest the reader, since the author mainly devotes 

 it to a reiteration of the ideas of his earlier works on 

 physics and chemistry. He claims that the minerals 

 and rocks composing the earth's crust are all of 

 organic origin, including even granite. The thick- 

 ness of this crust he thinks, in the absence of positive 

 knowledge, to be from three to four leagues, or from 

 nine to twelve miles. 



After describing the mode of formation of minerals, 

 including agates, flint, geodes, etc., he discusses the 

 process of fossilization by molecular changes, silicious 

 particles replacing the vegetable or animal matter, as 

 in the case of fossil wood. 



While, then, the products of animals such as corals 

 and molluscs are limestones, those of vegetables are 

 humus and clay ; and all of these deposits losing their 

 less fixed principles pass into a silicious condition, and 

 end by being reduced to quartz, which is the earthy 

 element in its purest form. The salts, pyrites, and 

 metals only differ from other minerals by the different 

 circumstances under which they were accumulated, in 

 their different proportions, and in their much greater 

 amount of carbonic or acidific fire. 



Regarding granite, which, he says, naturalists very 

 erroneously consider as primitive, he begins by ob- 

 serving that it is only by conjecture that we should 

 designate as primitive any matter whatever. He 

 recognizes the fact that granite forms the highest 



