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210 THE EARTH'S CENTRAL FLUIDITY QUESTIONED. [Ch. XXXII- 



was moreover, supposed that these primitive formations, as 

 they were called, implied a continual thickening of the crust 

 at the expense of the original fluid nucleus. These notions 

 have been universally abandoned. It is now ascertained 

 that the granites of different regions are by no means all of 

 the same antiquity, and that it is hardly possible to prove any 

 one of them to be as old as the oldest known fossil organic 

 remains. It is likewise now admitted, that gneiss and other 

 stratified crystalline strata are sedimentary deposits which 

 have undergone metamorphic action, and they can almost 

 all be demonstrated to be newer than the lately discovered 

 fossil called Eozoon Canadense. It follows from such views, 

 which are of comparatively modern date, that instead of 

 these crystalline rocks, which are often of enormous volume, 

 implying a constant thickening of the earth's crust from 

 the remotest periods, they most of them bear testimony to 

 aqueous denudation on a vast scale, or, in other words, they 

 bespeak the removal of just as much solid matter from one part 

 of the earth's circumference as has been contemporaneouslj 

 accumulated in the shape of new strata in some other part. 

 It was, moreover, taken for granted by the earlier theorists, 

 without any sufficient geological proof, that the energy of 

 the volcanic force was far more intense in the remoter 

 periods of the earth's history than in the later. No adequate 

 conception had been formed of the great lapse of time occu- 

 pied in the elaboration of each of the principal groups of 

 the primary, secondary, and tertiary fossiliferous rocks, and 

 of the gradual manner in which contemporaneous volcanic 

 products were locally developed during each of those ]3CTiods. 

 The limited areas to Avhich the volcanic outbursts were 

 confined at any one epoch, the Cretaceous for example, is 

 proved by the general absence in strata of the same age of 

 associated igneous formations. It can be demonstrated that 

 the volcanic power was b}^ no means dormant, but it Avas 

 locally developed. There are wide tracts in North America 

 and Russia where very ancient strata, such as the Silurian and 

 Carboniferous, are horizontal and undisturbed, and wholly de- 

 void of contemporaneous igneous products, showing that such 

 areas were not only free from volcanic action in paljrozoic 



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