276 Report of the State Gfeologist. 



a total thickness in Onondaga county of about sixty feet at the eastern 

 boundary, increasing to seventy feet at the western. At the Tully wells they 

 are seventy-five feet thick, according to Mr. Graham who superintended the 

 drilling. The Corniferous limestone is the surface rock over a narrow belt 

 at the top <>f the Helderberg escarpment, rarely showing more than a few- 

 feet in the face of the cliffs, though at the w est end of the great chasm of 

 the Green lakes, two miles north of Jamesville, the upper twenty-five feet 

 of the vertical w all is of Onondaga limestone. At Dry hill in Manlius, 

 along both sides of Onondaga valley, at Split Rock, and in fact at almost 

 every exposure it has been worn away, almost or quite, to a thin edge, evi- 



Solmo Rad Shol. - — _ _ — _- 



F5st- =-M Miles = " West 



FlGURK 8. East and west section across Onondaga county, showing the position of the lime- 

 stones in the Helderberg escarpment. 



dently by glacial action, as glacial ponshings and grovings are abundant. By 

 reason of its elevated position it was subject to the full power of the denud- 

 ing forces, and huge 1 docks were torn loose, tossed about and scattered in the 

 wildest and most fantastic manner. On the hillsides along the north and 

 south valleys, immense limestone boulders abound for many miles, and some 

 were carried to the tops of the highest hills. The window and door sills of 

 the stone store at Ponipey hill were cut from a huge block of Onondaga 

 linn-stone found a short distance away, on the very summit of the hill, six 

 miles south and at least one hundred feet above the bed from which it was 

 torn. The Line of outcrop extends for the entire width of the county, with 

 elongations toward the south along the sides of the valleys. East of Manlius, 



