58 SKETCHES OF CREATION. 



minerals as the rocks they rest upon. For instance, granite 

 is very commonly the foundation rock; but immediately 

 upon this repose thick beds of gneissoid rocks. Now 

 gneiss, like granite, is composed of quartz, feldspar, and 

 mica, and differs only in this — that the constituents have 

 been broken up, assorted by water, and redeposited in reg- 

 ular layers. As we have different varieties of granitoid 

 rocks, so we have corresponding varieties of gneissoid 

 rocks, differing from the former only in being stratified. 

 So general and so well recognized is this phenomenon, that 

 Sir Roderick I. Murchison, an eminent geological author- 

 ity, designates these lower strata beds of " fundamental 

 gneiss." This occurrence of gneiss, every where repos- 

 ing upon granite, is a most interesting and instructive 

 fact, and confirms all that I have said of the denudation 

 of the primitive islands, and the universality of the primi- 

 tive sea. 



But, though gneiss is generally the foundation stratum, 

 we find abundance of other rocks either reposing upon the 

 gneiss, or interstratified with it in the lower portions of the 

 sedimentary series. Undoubtedly some of these have re- 

 sulted from the impalpable powder to which long-contin- 

 ued attrition reduced some portions of the primitive gran- 

 ite, transported to the remotest and quietest portions of 

 the ocean, and there allowed to subside. But we know 

 also that others of the oldest strata associated with the 

 gneisses have been the results of chemical agencies. This 

 is one of the revelations of modern chemical geology, which 

 no name has more adorned than that of Dr. T. Sterry Hunt, 

 of the Geological Commission of the Dominion of Canada. 

 According to Hunt and Logan, the limestones of this early 

 period could have had no other than a chemical origin. 

 Common limestone is composed, as every one knows, of 

 carbonic acid and lime. Heat, as the manufacturer of lime 



