I02 ROCHESTER ACADEMY OF SCIENCE. [Jail- I I. 



has a thickness of 1030' in the well at Wolcott, Wayne Co., N. Y. 

 (Am. GeoL, Vol. VI, p. 204). Professor Hall stated: "The 

 usual estimates of the thickness of this group [Hudson including 

 Utica shale; see Geol. Surv. N. Y., Palaeontology, Vol. HI, Pt. i, 

 Text, p. 14] in central and northwestern New York are from 800 

 to 1000 feet " {Unci., p. 20, foot note). In the St. Catharines, Onta- 

 rio, well, Ashburner reported the Hudson and Utica as 785' in thick- 

 ness (Trans. Am. Inst. Min. Eng., Vol. XVIII, p. 301). Logan 

 gave the thickness of the Utica shale in Collingwood township, 

 on Nottawasaga bay, at the head of Georgian bay, as "between 

 fifty and a hundred feet" (Geol. Surv. of Canada. Rept. of Prog- 

 to 1863, p. 211); and the Hudson as 770' in thickness at the same 

 locality {Ibid., p. 213). 



m. Sir Wm. Logan estimated the thickness of the Trenton along the 

 Trent river in Ontario, which is nearly north of Rochester, as about 

 750' {Ibid., p. 188). Farther west he gave "about 150 feet for the 

 Birdseye and Black River formation on lake Couchiching, and 

 from 500 to 600 feet for the Trenton formation on lake Simcoe " 

 {Ibid., p. 193). The well at Wolcott passed through 750' of 

 Trenton without reaching its bottom (Prosser, Am. Geol. Vol. 

 VI, p. 204) ; while its thickness in the St. Catharines well was 

 677' (Ashburner, Trans. Am. Inst. Min. Eng., Vol. XVIII, p. 



301)- 

 n. Logan said there was no certain fossil evidence that the 

 Calciferous occurred on the western side of the Laurentian ridge 

 which crosses the St. Lawrence at the Thousand Islands (Geol. 

 Surv. of Canada. Rept. of Prog, to 1863, p. ti8). To the west 

 of this region, Logan wrote : " No indication of the Potsdam 

 formation has been observed in Canada, unless eight feet of red 

 soft calcareous sandstone at Marmora [which is nearly north of 

 Rochester], resting on the gneiss and succeeded by certain beds of 

 limestone without observed fossils for thirty feet upwards, be sup- 

 posed to represent it " {Ibid., p. 100 ; also, see section on pp. 181, 

 182, where the base rests on " contorted Laurentian gneiss "). 

 Ashburner states that the St Catharines well penetrates the Cal- 

 ciferous sandstone to the depth of 18' (Trans. Am. Inst. Min. 

 Eng., Vol. XVIII, p. 301). 



