208 THE CAMBRIAN. [bull. 81. 



it may be in the lower beds of the Calciferous. 1 In a later report he 

 noted the presence of the Potsdam sandstone on the north shore of the 

 St. Lawrence at Murray's Bay, 90 miles below Montreal, describing it 

 as a formation consisting of white, translucent, slaty quartz-rock hav- 

 ing an exposed tuickness of 45 feet and conformably subjacent to the 

 Calciferous sandrock. 2 



A brief summary of the lithologic and paleontologic characters of the 

 Potsdam sandstones in Canada was read by Dr. T. S. Hunt before the 

 American Association for the Advancement of Science in 1851. 3 





In an extended paper on the foot-prints occurring in the Potsdam 

 sandstone of Canada, Sir W. E. Logan describes the Potsdam sandstone 

 as it occurs in Canada in the St. Lawrence Valley. He states that — 



The sandstone in Beauhamois County and the neighboring part of the State of 

 New York is from 300 to 700 feet thick. Jn the lower part it contains many beds of 

 conglomerate, with quartz pebbles, and it has some red layers ; but towards the top 

 it becomes a fine-grained, bard, white sandstone, aud at the summit it is iuterstrati- 

 fied with calcareous layers, forming a passage to the rock which overlies it. 4 



The description of the extention of the Potsdam sandstone between 

 the River of the North and Beauharnois was continued by Sir W. E. 

 Logan in the report for 185L-52. 5 In the same volume Dr. Alexander 

 Murray describes the sandstone along the shores of the St. Lawrence 

 in the vicinity of Brockville, and also in the outcrops exposed between 

 the rivers Ottawa and St. Lawrence. 6 



This was followed in 1854 by the account of Dr. Murray's exploration 

 between Kingston and Lake Simcoe. In this region the Potsdam is 

 not largely developed, the greatest thickness of it observed in any one 

 place being certainly not over 40 or 50 feet, while west of Knowlton 

 Lake, in Loughborough, it appears gradually to decrease in thickness, 

 and eventually to die out altogether. 7 



In the summary of the work of the Geological Survey of Canada from 

 its commencement to 1863, there is given a very complete description 

 of the stratigraphic, lithologic, and paleontologic characters of the Pots- 

 dam sandstone as known in Canada. 8 Since that time very little has 

 been published upon the formation. 



1 Report on sequence and distribution of the formations (on the Ottawa). Geol. Surv. Canada: 

 Report of progress for 1845-'46, Montreal, 1847, p. 51. 



2 Report on Bay St. Paul and Murray Bay. Geol. Surv. Canada: Report of progress for 1848-'49. 

 Toronto, 1850, pp. 10, 11. 



3 Remarks on the lithological and paleontological characters of the Potsdam sandstone. Am. Assoc. 

 Proc, vol. 6, 1852, pp. 271-273. 



4 On the foot-prints accurring in the Potsdam sandstone of Canada. Quart. Jour. Geol. Soc, Lond., 

 vol. 8, 1852, p. 200. 



5 Report [on country between Riviere du Nord and Beauharnois] Geol. Surv. Canada, 1851-'52. 1852. 

 pp. 8-14. 



6 Report r of country lying between rivers Ottawa and St. Lawrence] Geol. Survey of Canada for 

 l85t-'52. 1852, pp. 64-67. 



7 [Exploration between Kingston and Lake Simcoe.] Geol. Surv. Canada: Report of progress for 

 1852-'53, 1854, p. 109. 



8 Geological Survey of Canada: Report of progress from its commencement to 1863. Montreal, 18(53, 

 pp. 87-109. 



