HISTORICAL GEOLOGY 91 



proves that the coal was formed in the neighborhood of 

 lands already emerged, and placed in similar physical 

 conditions. " 



An analysis of the Paleozoic fossils of Europe and 

 America leads De Verneuil to "the conviction that identi- 

 cal species have lived at the same epoch in America and 

 in Europe, that they have had nearly the same duration, 

 and that they succeeded each other in the same order. " 

 This he states is independent of the depth of the seas, 

 and of "the upheavings which have affected the surface 

 of the globe." The species of a period begin and drop 

 out at different levels, and toward the top of a system 

 the whole takes on the character of the next one. "If it 

 happens that in the two countries a certain number of 

 systems, characterized by the same fossils, are superim- 

 posed in the same order, whatever may be, otherwise, 

 their thickness and the number of physical groups of 

 which they are composed, it is philosophical to consider 

 these systems as parallel and synchronous." 



Because of the dominance of the sandstones and shales 

 in eastern New York, De Verneuil holds that a land lay 

 to the east. The many fucoids and ripple-marks from 

 the Potsdam to the Portage indicated to him shallow 

 water and nearness to a shore. 



The Oldest Geologic Eras. We have seen in previous 

 pages how the Primitive rocks of Arduino and of Werner 

 had been resolved, at least in part, into the systems of 

 the Paleozoic, but there still remained many areas of 

 ancient rocks that could not be adjusted into the accepted 

 scheme. One of the most extensive of these is in Canada, 

 where the really Primitive formations, of granites, 

 gneisses, schists, and even undetermined sediments, 

 abound and are developed on a grander scale than else- 

 where, covering more than two million square miles and 

 overlain unconf ormably by the Paleozoic and later rocks. 

 The first to call attention to them was J. I. Bigsby, a 

 medical staff officer of the British Army, in 1821 (3, 

 254). It was, however, William E. Logan (1798-1875), 

 the "father of Canadian geology," who first unravelled 

 their historical sequence. At first he also called them 

 Primary, but after much work he perceived in them par- 

 allel structures and metamorphosed sediments, under- 



