2.] PROSSER THE GENESEE SECTION. lOI 



" My estimate of the prevailing thickness of the Salina form- 

 ation on the west of the Genesee river is about 800 feet." But 

 the Professor in the above estimate assigned too great a thick- 

 ness to the red shale at the base of the group, which he says " may 

 be 300 feet or more thick " (Trans. Am. Inst. Min. Eng., Vol. 

 XVII, p. 400). 



Prof. Hall, 1838, gave 150' of "geodiferous and bituminous lime- 

 stone" at Rochester and no' of ''Calcareous shales" below (2d 

 An. Rept. Fourth Geol. Dist. N. Y., vertical section and descrip- 

 tion of rocks on pp. 300-303). But the lower 18' of the "cal- 

 careous shales" is the "upper limestone" of the Clinton, and 

 it is not clear but that some of the Onondaga Salt group was 

 included in the upper division. In 1843 the thickness of the 

 Niagara shale at Rochester is given as about 100' and the lime- 

 stone as "about seventy or eighty feet at Rochester" (Geol. 

 N. v., Pt. IV., p. 97). Logan said : " At Rochester it [the Niag- 

 ara] attains a thickness of about 180 feet " (Geol. Surv. of Can- 

 ada. Rept. of Prog, from its commencement to 1863, p. 321). 

 The section of 1838 gave 61' of "argillaceous shales, limestone, 

 iron ore and green shale" to which 18' of the overlying "cal- 

 careous shales" should be added, making 79' of what was later 

 named the Clinton (2d An. Rept. Fourth Geol. Dist. N. Y., ver- 

 tical section ; and see pp. 297-300 for a description of the rocks). 

 In the final report the thickness of the Clinton on the Genesee 

 river is stated to be 80' 6" (Geol. N. Y., Pt. IV, pp. 66, 67). 

 Hall's " vertical section " of 1838 gave a thickness of 300' of 

 " red marl and sandstone " along the Genesee river from Car- 

 thage to lake Ontario (2d An. Rept. Fourth Geol. Dist. N. Y., see 

 pp. 294-297 for a description of the rocks). In 1843 the Pro- 

 fessor reported its thickness along the Niagara river as about 

 350', which he considered as probably less than half its thickness, 

 and stated that it thinned to the eastward (Geol. N. Y., Pt. IV, p. 

 43). Logan thought that, apparently near Rochester, the entire 

 thickness " of the formation [Medina] may be somewhat under 

 600 feet " (Geol. Surv. of Canada. Rept. of Prog, to 1863, p. 310). 

 Mr. Walcott reported 880' of Lorraine sandstone and shales and 

 120' of Utica shale in a well at Fulton, Oswego Co., N. Y., which 

 he says " indicates a thickness of 1000 feet for the rocks of the 

 Hudson period in northwestern New York " (Bull. Geol. Soc. 

 Am., Vol. I, p. 349). Prosser found that the Hudson period 



