OF ORGANIC NATURE. 51 



meet with yet older rocks, containing numbers of 

 strange shells and fishes; and in thus passing from 

 the surface to the lowest depths of the earth's crust,' 

 the forms of animal life and vegetable life which I 

 should meet with in the successive beds would, looking 

 at them broadly, be the more different the further 

 that I went down. Or, in other words, inasmuch 

 as we started with the clear principle, that in a series 

 of naturally-disposed mud beds the lowest are the 

 oldest, we should come to this result, that the further 

 we go back in time the more difference exists between 

 the animal and vegetable life of an epoch and that 

 which now exists. That was the conclusion to which 

 I wished to bring you at the end of this Lecture. 



d 2 



