46 VESTIGES OF THE 



series, is not less than a hundred miles in direct thick- 

 ness. We have also evidence that the earliest strata 

 were formed in the presence of a stronger degree of heat 

 than what operated in subsequent stages of the world, 

 for the lamino3 of the gneiss and of the mica and chlorite 

 schists are contorted in a way which could only be the 

 result of a very high temperatui'e. It appears as if the 

 seas in which these deposits were formed, had been in 

 the troubled state of a caldron of water nearly at boiling 

 heat. Such a condition would probably add not a little 

 to the disintegrating power of the ocean. 



The earliest stratified rocks contain no matters which 

 are not to be found in the primitive granite. They are 

 the same in material, but only changed into new forms 

 and combinations ; hence they have been called by Mr. 

 Lyell, metamorphic rocks. But how comes it that some 

 of them are composed almost exclusively of one of the 

 materials of granite ; the mica schists, for example, of 

 mica — the quartz rocks, of quartz, etc. % For this there 

 are both chemical and mechanical causes. Suppose that 

 a river has a certain quantity of material to carry down, 

 it is evident that it will soonest droj:) the larger particles, 

 and carry the lightest farthest on. To such a cause is it 

 owing that some of the mn.terials of the worn-down 

 granite have settled in one place and some in another.* 

 Again, some of these materials must be presumed to 

 have been in a state of chemical solution in the primeval 

 seas. It would be, of course, in conformity with chemi- 

 cal laws, that certain of these materials would be pre- 

 cipitated singly, or in modified combinations, to the 

 bottom, so as to form rocks by themselves. 



The rocks hitherto spoken of contain none of those 

 remains of vegetables and animals which nboniid so 

 * Do la Decile's " Gcolocrical ll-iscavclics."' 



