22 Classification of RocTcs, 



the upper surface of the lower Silurian rocks in Upper Canada. The for- 

 mation skirts the south shore of Lake Ontario, from the Niagara river to 

 Hamilton, and thence continues down the Lake to Oakville ; it thence runs 

 north to Owen Sound and fringes the western coast of the Georgian Bay for 

 several leagues further, it also crosses the Manitoulin Islands in a narrow 

 belt. In Lower Canada it does not appear to have been very decidedly 

 recognized. 



Clintok and Niagara Groups. 

 These are generally considered by the American Geologist to be sepa- 

 rate formations distinguished from each other by characteristic suites of 

 fossils. A series of green shales and impure limestones, with a partial bed 

 of fossiliferous iron ore of variable thickness, are the materials of which the 

 first is formed ; and a mass of shale 80 feet thick, overlaid by 160 feet of 

 limestone, constitutes the latter. The Clinton group is estimated by Pro- 

 fessor Hall, of the New York Geological Survey, at about 60 feet in thick- 

 ness. Mr. Murray, of the Provincial Survey, ascertained the thickness of 

 the two groups to be 560 feet on the Manitoulin Islands. These formations 

 have yielded a rich harvest of fossils of the upper Silurian age. They cross 

 the Niagara river between Queenstown and the Falls, in a belt here about 7 

 miles wide ; they then run westerly, and turning round to the north in the 

 rear of Hamilton, stretch nearly across the counties of Wellington, Went- 

 worth, Bruce and Grey, to Lake Hm-on. They constitute the long irregular 

 tongue of land which separates this lake from the Georgian Bay, and also 

 all the southern portions of the Manitoulin Islands. They have also been 

 detected by Mr. Logan in the Eastern Townships of Lower Canada. 



Onondaga Salt Group. 

 This formation is a very important oiie for the agriculturist. It is des- 

 cribed as consisting of grey or drab coloured limestones, ai*gillaceous sliales, 

 marls and shaly limestones, with deposits of gypsum — thickness probably 

 350 feet. The gypsum is found in detached masses, often in great quantities, 

 but never in regular strata. It is largely quarried in certain of the western 

 Townships near Lake Erie, where the formation is extensively developed. — 

 The formation enters the upper province in a narrow band between the 

 Niagara Falls and Lake Erie, and proceeds westerly through the counties of 

 Welland, Haldimaud, Brant, Waterloo, Wellington, Bruce and Grey, to 

 Lake Huron, at the Townships of Bruce and Saugeen. It has not been 

 distinctly recognized in Lower Canada. 



CORNIFEROUS LiMESTONE. ' 



The Corniferous Limestone consists of a fine grained, compact, calca- 

 rous rock, generally bluesh or gi-eyish, and containing great numbers of 

 hornstone nodules. It may be estimated at the thickness of 100 feet, and it 

 probably includes in its lower portion in Canada a thin formation, called the 

 Onondago Limestone by the New York Geologists. It crosses the western 

 peninsula from Lake Erie to Lake Huron, and probably underlies the 

 greater portion of that tract of country occupied by the counties of Norfolk, 



