76 THE CANADIAN NATURALIST. [Yol. vi. 



den, 146 and 200 ; in Sombra, 100; in Alvinstone, eighty feet; 

 in Warwick, and near Wyoming station, about fifty ; a little 

 north of Bothwell, about eighty ; and further south, towards the 

 shore of Lake Erie, about sixty feet in thickness. It will be un- 

 derstood that this varying thickness is due to the erosion along 

 the anticlinals, before the deposition of the clays, so that in many 

 parts of the region only the lower portions of the black slates 

 remain, while in other places they are entirely wanting. 



The hard strata just described are conformably underlaid by 

 those of the Hamilton formation, which in some parts of New 

 York attains a thickness of 1,000 feet, but is reduced to 200 feet 

 in the western part of the State. It consists, in Ontario, chiefly 

 of soft grey marls, called soapstone by the well-borers, but in- 

 cludes at its base a few feet of black beds, probably representing 

 the Marcellus shale. It contains, moreover, in some parts, beds 

 of from two to five feet of solid gray limestone, holding silicified 

 fossils, and in one instance impregnated with petroleum ; charac- 

 ters which, but for the nature of the organic remains, and for the 

 associated marls, would lead to the conclusion that the underlying 

 Corniferous limestone had been reached. The thickness of the 

 Hamilton formation varies in different parts of the region under 

 consideration. From the record of numerous wells in the south- 

 western portion it appears that the entire thickness of soft strata 

 between the Corniferous limestone below and the black shale 

 above, varies from 215 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 gray shale were traversed in 

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

 adjacent township of Warwick, in a similar boring, the underly- 

 ing; limestone was reached 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) 

 auGrments in volume from 200 feet on Lake Erie to about 400 

 feet near to Lake Huron. 



The Hamilton formation, as just defined, rests directly upon 

 the solid non-magnesian limestones of the Corniferous formation. 

 The thickness of this formation in western New York is about 

 ninety feet, and in southern 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 Towns- 

 end its thickness has been found to be 160 feet; but for a great 



