Classification of RocJcs. 21 



from which city it runs in one direction down the north shore of the St. Law- 

 rence to some distance below Quebec, and in another dhection to Lake 

 Champlain — several bands of it on the south side of the St. Lawrence below 

 Montreal, extend southwardly to the Province line East of Lake Cham- 

 plain. 



Utica Slate. 



The Utica Slate, so called after the city of that name in the State of 

 New York, is a jet black shale resembling a mass of hardened mud. Upon 

 exposure for a few mouths to the air, it turns of a light brown or chocolate 

 colour upon its surface, and finally decomposes into a clay soil of consider- 

 able fertility. The rock at the surface is generally seen in small flat slaty 

 fragments, but on penetrating downwards into the deposit several feet, it is 

 found to be very compact, but crossed by numerous joints or fissures in a 

 direction diagonal to the stratification. In the lower part of the formation 

 it includes several thin beds of limestone, with seams of bituminous shale 

 between them, generally full of fossils. According to Mr. Logan's map, 

 published in the Canadian Journal, vol. 3, the Utica Slate borders Lake 

 Ontario in the irout of the Townships of Hamilton, Hope, Clarke, Darlmg- 

 ton, Whitby, and Pickering. It then leaves the lake and runs in a belt, 

 several miles wide, in the rear of Toronto and north to the Georgian Bay, 

 where it forms the front of the Township of Nottawasaga and part of Col- 

 lingwood. It forms several long parallellbeds in the counties of Carleton, 

 Russell, and Prescott, extending from the city of Ottawa to the neighbour- 

 hood of Hawkesbury. It also occurs in the neghbourhood of Montreal and 

 again near Quebec. Between these two cities, on both sides of the St. Law- 

 rence, it has been found in various irregular patches and bands, marked by 

 its characteristic fossils. 



Hudson River Group. 



This group, which is said to have a thickness of from 1,000 to 1,400 

 feet, is composed of blue, green, or red argillaceous shales, interstratified with 

 thin bands of sandstone, and occasionally some limestones. It forms the 

 shore of Lake Ontario, from the Township of Pickering to the Credit. The 

 city of Toronto stands upon it, or rather above it, for a deep bed of drift 

 covers the formation in this part of the province. From Lake Ontario it 

 extends back to the Georgian Bay, which it reaches in the Townships of 

 Collingwood, St. Vincent, and Sydenham ; further on in this direction it 

 courses along the northern sides of the Manitoulin Islands, where it is accon,- 

 panied by the Utica. slate in a very narrow band. In Lower Canada it con- 

 stitutes much of the country on the south shore of the St. Lawrence, below 

 Montreal, and is largely developed at Quebec, and at several points in the 

 neighbourhood on the north shore. 



The Medina Sandstone. 



The Medina Sandstone is composed of red and green coloured marls and 



slaty sandstones, with a thick bed of grey sandstone at the top, yielding fine 



building stones, for which purpose it is extensively used — the formation is 



said to be 600 feet in thickness. The grey band at the summit constitutes 



