THE CKUST OF THE EARTH. 



who desire to obtain even the most superficial acquaintance 

 with it, are therefore compelled to familiarise themselves with a 

 mass of most repulsive technicalities, in which the same thing is 

 called by many different names, according to the varying views, 

 tastes, and even personal caprices of the geological investigators 

 who have devoted their labours to the researches in which it finds 

 a place. 



Names have been given to strata or groups of strata in some 

 cases from the localities in which they are found at the surface, 

 as for example the Jurassic, the Silurian, the Cambrian, and the 

 Devonian groups. In other cases, names are derived from the 

 prevalent materials constituting them, as the cretaceous, oolitic, 

 and carboniferous groups. Other names have been adopted from 

 the order of the deposits, as for example eocene, miocene, 

 pleiocene, and pleistocene, from Greek words signifying the first 

 dawn, or the earliest, less recent, more recent, and most recent, 



Another set of names has been taken from the presence, 

 absence, or dates of the forms of life exhibited by the organic 

 remains found in the strata. Thus the strata, which are destitute 

 of all such remains, are called AZOIC, from a Greek compound 

 implying the absence of life. The term cainozoic is applied to the 

 most recent strata, including organic remains, mesozoic to the 

 middle strata, paloeozoic to the ancient strata, protozoic to the 

 first in which life appears, and hypozoic to those strata which 

 lie below the range of all organic remains. 



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