294 THE CANADIAN NATURALIST. [Aug. 



Paleozoic Formations. 



15. Hamilton, — shales. 



14. Corniferous, — limestone. 



13. Oriskany, — sandstone. 



12. Onondaga or Gypsiferous, — dolomite. 



11, Guelph, — dolomite. 



10. Niagara, — dolomite. 



9. Clinton, — limestone and shale. 



8. Medina, — sandstone. 



6. Hudson River, — shales. 



5. Utica, — shales. 



4. Trenton, — limestone. 



3. Chazy, — limestone. 



2. Calciferous, — dolomite. 



1. Potsdam, — sandstone. 



§ 73. Of the above series the Trenton group includes the Birds- 

 eye and Black Biver limestone, as well as the Trenton limestone 

 of the New York geologists, and is non-magnesian, enclosing beds 

 of chert, silicified fossils, and petroleum ; in all of which characters it 

 resembles the Corniferous limestone above. In like manner the 

 Potsdam is represented by the Hudson-Biver and Medina forma- 

 tions, while the gypsiferous dolomite of the so-called Calciferous sand*- 

 rock corresponds to the great mass of dolomite which constitutes 

 Nos. 10, 11, and 12, and includes the gypsum and the salt-bearing 

 strata of the Onondaga formation. These repetitions of similar 

 strata, marking successive recurrences of similar geological and geo- 

 graphical conditions, which form great cycles in the history of the 

 continent, have been already considered in a paper by me on Bitu- 

 mens, etc., in Silliman's Journal [2], xxxv, 166. 



§ 74. In the eastern basin, which includes not only south-eastern 

 Canada, but the whole of New England, the strata are in an alter- 

 ed and crystalline condition, if we except a narrow belt along the 

 north-west border of the basin. These unaltered strata present a 

 great series of shales, conglomerates, and limestones, pure andmag- 

 nesian, succeeded by 2000 feet or more of sandstones, with shales ; 

 the whole forming what the Canadian Geological Survey has 

 named the Quebec group, whose aggregate thickness in the 

 vicinity of Quebec is about 7000 feet. The geological horizon 

 of this group of strata corresponds to that of the Chazy, the 

 Calciferous, and perhaps of the Potsdam. It was in great part 

 a deep-sea deposit, of which the formations just named are but 

 incomplete and littoral representatives. Of the waters described 



