116 THE CAMBRIAN. [bull. 81. 



Dr. J. J. Bigsby, 1 in describing the geology of Quebec and its en- 

 virons, states that the Potsdam sandstone only occurs distinctly, as far 

 as yet known in the neighborhood, at the Falls of Montmorenci ; but 

 at Jeune Lorette there are traces of it. He says that — 



The sandstone of Montmorenci has been unhesitatingly declared to represent the 

 Potsdam rock by the New York State geologists, as well as by Sir Charles Lyell and 

 Mr. Logan. With these high authorities I have only to concur. Its geological posi- 

 tion is that of the Potsdam sandstone ; but its aspect and mineral condition are very 

 different from that of Lake Superior and of the Thousand Islands, near Kingston, 

 Upper Canada. 2 



In describing the geology of the Falls of Montmorenci, he says : 



The sandstone is plentiful on the east bank of the river above the bridge, and is a 

 yard or more thick, as well as on the west bank both above and below the bridge ; 

 the plane of contact with the enclosing rock being clean and abrupt. It is white, 

 brownish red or bright green, in well defined layers. Bowlders of the gneiss occur 

 in it. 3 



A section is introduced in which the Potsdam sandstone is repre- 

 sented as beneath the Trenton limestone, and with the latter resting 

 unconformably against the gneiss. It is stated that the Potsdam sand- 

 stone at this place has not yet been found to contain organic remains. 



Dr. Bigsby described the north shore of the St. Lawrence, from Quebec 

 to Cap Kouge, as consisting of frequent alternations of gritty gray 

 sandstone, and red, brown, and black clay shale. On the south side of 

 the St. Lawrence, near Point Levis, the rocks are stated to be formed of 

 minute alternations of clay-slate, coarse sandstone, calcareous and other 

 conglomerates that were met with on the north side of the river. 4 



In the report of progress for 1852-'53, published in 1854, Sir W. E. 

 Logan 5 describes the red and green shales and green sandstones from 

 Cap Rouge to Quebec, considering them to belong to the Hudson River 

 group of the New York section. 



In a description of the Silurian rocks of the environs of Quebec, the 

 same writer 6 states that the only exposure of the Potsdam formation in 

 the vicinity of Quebec is at Lorette, where the sandstone is 7 metres in 

 thickness and without the fossils which characterize the formation in 

 other parts of Canada. The shales and saudstone of the Sillery forma- 

 tion are stated to correspond to the conglomerates of the Oneida for- 

 mation of the New York geologists. This same view was expressed in 

 the geological essay prepared for the Paris Exposition of 1855 by 

 Messrs. Logan and Hunt. 



From the collections of fossils made by the Geological Survey of Ca- 

 nada at Point Levis during the years 1856-'57, Mr. E. Billings, paleon- 



*On the geology of Quebec and its environs. Quart. Jour. Geol. Soc, vol. 9, 1853, pp. 82-101. 



2 Op. cit., p. 84. s Op. cit., p. 88. 4 0p. cit., pp. 94, 95. 



'(Exploiation on the north side of the St. Lawrence, between Montreal and Cape Tourmente.) 

 Geol. Hurv. Canada, report progress for 1852-'53, 1854, pp. 33, 34. 



6 (Sur la formation silurique des environs de Quebec.) Soc. geol. France, Bull., 2 e ser., vol. 12, 1855, 

 p. 505. 



