PERMIAN AGE AND CLOSE OP THE lALiEOZOIC. 177 



sivience and by a sea area tenanted by corals and 

 shell-fishes. In each case this was followed by a 

 re-eleration, leading to a second but slow and partial 

 subsidence, to be followed by the great re-elevation 

 preparatory to the next period. Thus we have 

 throughout the Palaeozoic a series of cycles of 

 physical change which we may liken to gigantic 

 pulsations of the thick hide of mother earth. The 

 final catastrophe of the Permian collapse was quite 

 different in kind from these pulsations as well as 

 much greater in degree. The Cambrian or Prim- 

 ordial does not apparently present a perfect cycle 

 of this kind, perhaps because in that early period 

 the continental plateaus were not yet definitely 

 formed, and thus its beds are rather portions of the 

 general oceanic deposit. In this respect it is analo- 

 gous in geological relations to the chalk formation 

 of a later age, thoiigh very difi'erent in materia]. 

 The Cambrian may, however, yet vindicate its claim 

 to be regarded as a definite cycle ; and the recent 

 discoveries of Hicks in North Wales, have proved 

 the existence of a rich marine fauna far down in the 

 lower part of this system. It is also to be observed 

 that the peculiar character of the Cambrian, as an 

 oceanic bottom rather than a continental plateau, 

 has formed an important element in the difficulties 

 in establishing it as a distinct group; just as a 

 similar difficulty in the case of the chalk has led 

 to a recent controversy about the continuance of the 

 conditions of that period into modern times. 



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