Detrital Theory of Geology. 321 



joint labours of Carpenter, Jones, and Parker. Therefore, in 

 determining their presence or absence as identical species, 

 between one stratum and another, or in past strata and the 

 existing fauna, much care is required, and, as determining 

 agents for particular strata, are, for the most part, not to be 

 depended upon. 



From this rapid review of organic conditions, from' the 

 lowest of the protozoa to the higher mammalia, let the 

 attention next be directed in reviewing the forces of nature 

 which tended to establish that order of stratification now 

 found in the geological chart of rocks. 



The attention is first arrested by the fact that different 

 epochs or intervals of stratification are marked by more 

 violent forces of elevation acting powerfully and somewhat 

 abruptly at one period, and more gradually and continuously 

 during the intermediate periods, as at the present time in 

 Scandinavia, along the coast of the Mediterranean ; and in 

 the Pacific along the coast of South America, where 

 elevations or depressions are going on slowly but constantly, 

 and in many other parts. 



After the formation of the metamorphic rocks, the 

 elevating forces first appear to have broken forth through 

 the Silurian and Devonian systems in great violence, and to 

 have considerably elevated the submerged rocks, fracturing 

 and dislocating them in bold and unequal proportions ; 

 whilst from thence till the Permian system was formed, the 

 same work of increasing elevation of the land was going on, 

 but in a more gradual and regular manner. After the Permian 

 system was finished, nature roused up her semi-quiescent 

 forces into more powerful operation, and the Triassic system 

 abounds in bold and rugged mountain scenery, with abrupt 

 fractures and mountain elevations, the evident result of 

 internal forces expanding and raising the crust of the globe 

 above its former level most extensively and violently. 



21 



