1892.] PROSSER THE GENESEE SECTION. 



99 



belonging to the " Calcareous shales of the Mountain limestone ;" 

 but judging from the accompanying section along the Genesee 

 river this division did not extend to the base of the Hamilton 

 (2d An. Rept. Fourth Geol. Dist. N. Y.). In the final report the 

 Professor gave its thickness on Lake Erie as less than 500' and 

 not less than 1000' on the eastern limit of the fourth district, 

 along Cayuga lake (Geol. N. Y., Pt. IV, p. 194), Dr. Clarke 

 makes the thickness of the Hamilton in Ontario Co. probably 

 greater than 400' (Rept. State Geol. [N. Y.] for 1884, pp. 12-17). 

 The Jamestown well has about 395' of Hamilton (Harris, Am. 

 Geol., Vol. VII, pi, 4, see pp. 169, 170). 



f. Prof. Hall wrote : " The greatest thickness of this rock [Marcellus], 

 where it can be measured accurately, does not amount to more 

 than fifty feet " (Geol. N. Y., Pt. IV, p. 179). Dr. Clarke assigns 

 it "a thickness of about 100 feet" in Ontario Co. (Rept. State 

 Geol. [N. Y.] for 1884, p. 11). Mr. Harris calls it about 50' thick 

 in the Jamestown well (Am. Geol., Vol. VII, pi. 4, p. 170). 



g. Hall's "vertical section" of 1838 gave a thickness of 350' to 

 what he then called the " Carboniferous or Mountain limestone " 

 (2d An. Rept. Fourth Geol. Dist. N. Y., and see p. 307) ; but this 

 apparently included the Marcellus and the base of the Hamilton. 

 In 1843 the Professor considered "The point of greatest thick- 

 ness [of the Corniferous limestone] actually measured is on 

 Allen's creek [at Le Roy (?)], where it is seventy-one and a half 

 feet" (Geol. N. Y., Pt. IV, p. 168). While the Onondaga lime- 

 stone at Le Roy is possibly 20' in thickness {Ibid., p. 157). Prof. 

 G. F. Wright gave the thickness of the Corniferous lime rock as 

 148' in the shaft of the salt mine at Piffard Station, Livingston 

 Co. (Science, A^ol. VIII, p. 52). Dr. Clarke called the Upper 

 Helderberg of Ontario Co. about 70' in thickness (Rept. State 

 Geol. [N. Y.] for 1884, p. 10). Mr. Harrig reported about 150' of 

 Upper Helderberg in the Jamestown well (Am. Geol., Vol. VII, 

 pi. 4, p. 170). 



h. The Oriskany sandstone is scarcely represented in this section. 

 Prof. Hall said : " In Monroe county, its only representative is a 

 layer of greenish conglomerate about four inches thick. * * * 

 The last place in the district where it has been noticed is in the 

 bed of Black creek at Morganville in Genesee county" (Geol. 

 N. Y., Pt. IV, p. 146). Dr. Clarke wrote : " it [Oriskany] is not 



