1869.] HUNT — GEOLOGY OP SOUTH-WESTERN ONTAKIO. 13 



ceous shales, holding Calamites, are met with. They strata 

 also were recognized by Mr. Hall, who examined them, as 

 belonging to the Portage formation ; and abound in the large 

 spherical calcareous concretions which occur at the same horizon 

 in New York. The entire thickness of the black shales at 

 this point has not been determined, but in numei'ous borings 

 throughout the region under notice, they are easily distinguished 

 both by color and hardness, from the soft gray Hamilton 

 shales which underlie them. At Corunna, near Sarnia, a thick- 

 ness of not less than 213 feet of hard black shales, interstratified 

 towards the top with greenish sandstone, were met with. In the 

 northern part of Enniskillen, near Wyoming, they are about fifty 

 feet in thickness ; at Alvinstone, eighty feet ; in Sombra, on the 

 Sydenham river, 100 feet, and in two borings in Camden, 146 and 

 200 feet. A little to the north of Bothwell, on the Thames, 

 their thickness was found to be seventy-seven feet, while south- 

 ward, along the shore of Lake Erie, about sixty feet of the hard 

 black slate overlie the soft gray Hamilton shales. 



From these, and a great many similar observations, which are 

 detailed at length in the Report of the Geological Survey of 

 Canada, published in 1866, it has been possible to determine with 

 considerable accuracy the distribution of these black strata 

 beneath the thick covering of clay which conceals them through the 

 greater part of the region. It being impossible, under the 

 circumstances, to distinguish between that lower portion of the 

 black strata which belongs to the Hamilton group or Middle 

 Devonian, and the overlying Portage formation, the whole of these 

 strata, down to the summit of the soft gray shales, are included 

 with the Portage. In Michigan, according to Prof Winchell, the 

 whole thickness of the Portage (Huron) group, as just defined, 

 including twenty feet of black shale at its base, is only ii24 feet, 

 which are represented in Ontario by 200 feet on the Sydenham 

 river, and by 213 feet at Corunna on the St. Clair. Yet, Prof. 

 Winchell, for some reason, doubts the existence of the Portage 

 formation in Ontario. 



The Hamilton shale, 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, consists in Ontario chiefly of soft gray 

 marls, called soapstone by the well-borers, but includes 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 



