THE CRUST OF THE EARTH. 



of these living instruments. Ehrenberg, the celebrated Prussian 



microscopist and naturalist, mentions a stratum in Germany, not 

 less than 14 feet in thickness, com- 

 posed exclusively of the shells of 

 animalcules, so minute that forty 

 thousand millions of them would 

 not fill a space greater than a cubic 

 inch. Mountains, hundreds and 

 even thousands of feet in height, are 

 found to be composed exclusively of 

 organic matter. The strata of ve- 

 getable origin are not less exten- 

 sive, consisting of forests engulfed 

 by the subsidence of vast tracts of 

 land, or embedded in the mud of 

 rivers and estuaries, of lignite 

 and brown coal in the tertiary de- 

 posits, of coals and shales in the 



carboniferous strata, and of silicified and calcified trunks of 



trees in the tertiary and secondary formations. 



75. But the strata which consist wholly or principally of 



animal remains are so numerous, and of such vast extent, that, 



as Dr. Mantell observed, the exclamation of the poet may be 



reiterated by the philosopher, 



"Where is the dust that has not been alive ?" 



for there is not an atom in the superior strata of the crust of the 

 globe that has not probably passed through the complex and mar- 

 vellous laboratory of vitality. 



The various families of animals from the infusoria and 

 zoophytes, up to man himself, have then contributed more or less, 

 by their organic remains, to form the solid crust of the globe. 

 The following table, taken from the work of Dr. Mantell, pre- 

 sents a concise view of some of the most obvious examples of 

 these remarkable deposits. 



Fig. 24. Ceratites Nodosus. 



