HYPOTHETICAL STAGES LEADING UP TO THE KNOWN ERAS. 85 



seems to be a necessary attribute of a rock formed from a molten globe, 

 except at the very surface, for the process of cooling must have been, 

 very slow, and the conditions for the growth of the crystals most pro- 

 pitious. The primitive formation should hence be of the most mas- 

 sive and declared noncrystalline type. Its distinctive character 

 could scarcely be disguised beyond recognition by any probable kata- 

 morphism at a later date. 



The limitations of pyroclastic concealment of the crust. — No very 

 large amount of scoriaceous and fragmental material can be assumed 

 to have been heaped upon the original crust consistently with the 

 hypothesis in the form above stated; for the assumption that the primi- 

 tive atmosphere contained all the future water of the hydrosphere 

 leaves no appreciable explosive agency in the molten globe to pro- 

 duce such material. The atmospheric and hydrospheric constituents, 

 by the terms of the hypothesis, had either never condensed, or had 

 been thoroughly boiled out of the white-hot mass. This is not an 

 undue forcing of the mere phrasing of the hypothesis, for not a few 

 familiar doctrines and working conceptions have been built upon the 

 assumed exclusion of the hydrospheric and atmospheric constituents 

 from the primitive rocks. The permanent concealment of the orig- 

 inal crust under pyroclastic material cannot, therefore, consistently 

 be assumed without modifying the hypothesis, for many thousand 

 feet have been eroded from the surface of the oldest known areas. - 



The adverse bearing of recent discoveries. — Until recently, the 

 great granitoid areas of the Archean series were thought to meet 

 very fairly the theoretical requirements of the case; but it has been 

 discovered in no less than five of the regions most critically studied, 

 that many of these great granitoid masses are intrusive, and that they 

 have been forced into rocks that were formed on the surface by lava 

 outflows, volcanic fragmentation, or surface sedimentation. This sig- 

 nificant discovery was made almost contemporaneously by geologists 

 of Canada, the United States, Great Britain, Scandinavia, and Finland. 

 While such an intrusive nature has not yet been proved for all the great 

 granitoid masses of all Archean areas, the presumption now lies in 

 that direction. The new interpretation thus reduces to an unknown, 

 if not a vanishing quantity, the area of massive crystalline rock that 

 can, with plausibility, be referred to the supposed original crust. But 

 the theoretical necessity for a large area of such rocks, if the molten 



