118 C. S. PROSSER DEVONIAN AND SILURIAN ROCKS. 



at Fort Plain " (Vanuxem : Geol. N. Y., pt. iii, p. 40). The Birdseye 

 limestone " is about 30 feet [thick], but, like other limestones in this 

 group, it thins out remarkably toward the south " (Emmons : Geol. N. 

 Y., pt. ii. p. 110; also, see p. 385). 



Q. — Mr Walcott reported surface outcrops of Calciferous 350 feet in 

 thickness for comparison with the Campbell well west of Utica, in which 

 it possibly lias a thickness of 360 feet (Proc. Am. Assoc. Adv. Sci., vol. 

 xxxvi, p. 212). Emmons wrote : " The entire thickness of the Calciferous 

 sandrock is between 250 and 300 feet " (Geol. N. Y., pt. ii, p. 106). 



R. — Mr Walcott reported Potsdam (?) sandstone 410 feet in thickness 

 in the Campbell well west of Utica (Proc. Am. Assoc. Adv. Sci., vol. 

 xxxvi, p. 212). Emmons stated that on the northern or Canadian slope 

 it " is about 300 feet thick " (Geol. N. Y., pt. ii, p. 103). Mr T. B. Brooks 

 reported in St. Lawrence county Potsdam and pre-Potsdam at the maxi- 

 mum 700 feet thick, part of which must be before the typical Potsdam 

 (Am. Jour. Sci., 3d ser., vol. iv, p. 22). 



Vanuxem in 1839 stated that the thickness of the whole series, from 

 the gneiss at Little Falls to the top of the Corniferous, " taking the 

 measure of each rock and group where its thickness is greatest, exceeds 

 2,000 feet" (Third Ann. Rept. Third Geol. Dist, N. Y., pp. 276). The 

 estimated thickness of this same series as compiled from various author- 

 ities is 3,530 feet, while the actual- thickness as obtained from the well 

 sections is 4.760 feet. In addition, Vanuxem stated : " There [then] re- 

 mains from 12 to 1,500 feet before completing the whole of the series of 

 the third district; all which are anterior in origin to the coal " (ibid., p. 

 276). This would make a total thickness of only 3,500 feet for the entire 

 series, while our compiled section gives 6,775 feet from the top of the 

 Chemung to the Archean, and the actual thickness of the rocks from the 

 Chemung, at Binghamton, which is something like 1,500 feet below the 

 top of Vanuxem's series* to the Archean is approximately 8,895 feet. 



Comparative Sections of eastern, central and western New York. 



For the purpose of comparison it has been thought advisable to prepare 

 a chart (page 116) giving the thickness of the different geological for- 

 mations for four sections, crossing New York in a line from north to south. 



The author is responsible for the sections denominated *' western," 

 "western-central" and "central New York," but the section for "eastern 

 New York " was measured and prepared by Charles A. Ashburner. 



*Compare the Chenango section (ix) in Professor Williams' "Meridional Sections of the Upper 

 Devonian Deposits of New York, Pennsylvania and Ohio" (Proc. Am. Assoc. Adv. Sci., vol. xxxiv). 



Topeka, Kansas, December, 1892. 



