14 THE CANADIAN NATURALIST. [Marcll 



five feet of solid gray limestone, holding silicified fossils, and 

 in one instance impregnated with petroleum, characters which, but 

 for the nature of the organic remains, and the underlying marls, 

 would lead to the conclusion that the Lower Devonian had 

 been reached. The thickness of the Hamilton shale varies 

 in diiFerent parts of the region under consideration. From 

 the record of numerous wells in the south-eastern portion, it 

 appears that the entire thickness of soft strata between the 

 Corniferous limestone below and the black shale above, varies 

 from 275 to 230 feet, while along the shore of Lake Erie, it 

 is not more than 200 feet. Further north, in Bosanquet, beneath 

 the black shale, 350 feet of soft gray shale were traversed in 

 boring, without reaching the hard rock beneath, while in the 

 adjacent township of Warwick, in a similar boring, the underlying 

 limestone was attained 396 feet from the base of the black shales. 

 It thus appears that the Hamilton shale (including the 

 insignificant representative of the Marcellus shale at its base) 

 augments in volume, from 200 feet on Lake Erie to about 

 400 feet near to Lake Huron. Such a change in an essentially 

 calcareous formation, is in accordance with the thickening of the 

 Corniferous limestone in the same direction. 



The Lower Devonian in Ontario is represented by the Corni- 

 ferous limestone, for the so-called Onondaga limestone has not 

 been recognized, and the Oriskany sandstone, always thin, is 

 in some places entirely wanting. The thickness of the Corni- 

 ferous in western New York is about ninety feet, and in south- 

 eastern Michigan is said to be not more than sixty, although it 

 increases in going northward, and attains 275 feet at Mackinac. 

 In the townships of Woodhouse and Townsend, about 

 seventy miles west from Buftalo, its thickness has been found to 

 be 160 feet, but, for a great portion of the region in Ontario 

 underlaid by this formation, it is so much concealed that it is not 

 easy to determine its thickness. In the numerous borings which 

 have been sunk through this limestone, there is met with nothing 

 distinctive to mark the separation between it and the limestone 

 beds which form the upper part of the Onondaga Salt-group 

 or Salina formation of Dana, which consists of dolomites, 

 alternating with beds of a pure limestone, like that of the Corni- 

 ferous formation. The saliferous and gypsiferous magnesian marls, 

 which form the lower part of the Salina formation are, however, 

 at once recognized by the borers, and lead to important con- 



