Spencer.] ^^^ [March 18, 



phia ; Gov. Hoyt ; U. S. :N". Observatory ; U. S. C. and a. 

 Survey ; Mr. Jed. Hotchkiss, Stauuton, Va. ; San Franc. 

 Mer. Association; Min. de Fom. and M. M. Barcena, 

 Mexico. 



The death of Dr. John J. Bigsby was announced by the 

 Secretary, with remarks on his early connection with geo- 

 logical exploration in America. 



The death of Prof. John Johnston, at Middlebury, Con- 

 necticut, in 1879, was reported. 



A memoir On the Preglacial drainage of Lake Erie and 

 the other great lakes, by Dr. J. W. Spencer, was read and 

 illustrated by the Secretary. 



A paper on " A Geological Section at St. Mary's, in Elk 

 County, Pa.," was read by Mr. Ashburner. 



Pending nominations, Nos. 927 to 932, and new nomina- 

 tion, No. 933, were read. 



And the meeting was adjourned. 



Discovery of the Preglacial Outlet of the Basin of Lake Erie into that of 

 Lake Ontario; with Notes on the Origin of our Lower Or eat Lakes. By 

 J. W. Spencer, B. A. Sc, Bh.D., F.G.S., King's College, Windsor, N. 8. 



(Bead hefoi^e the American Philosophical Society, March 18, 1881.) 



Summary. 



The object of this paper is to bring before the scientific world the follow- 

 ing observations, bearing on the Preglacial Drainage and origin of our 

 Great Lake Basins : 



1. The Niagara escarpment, after skirting the southern shores of Lake 

 Ontario, bends at nearly right angles in the neighborliood of Hamilton, at 

 the western end of the lake ; thence the trend is northward to Lake Huron. 

 At the extreme western end of the lake this escarpment (at a height of 

 about 500 feet) encloses a valley gradually narrowing to four miles, at the 

 meridian of the western part of the city of Hamilton, where it suddenly 

 closes to a width of a little more than two miles, to form the eastern end 

 of the Dundas valley (proper). This valley has its two sides nearly paral- 

 lel, and is bounded by vertical escarpments, which are capped with a great 

 thickness of Niagara limestone, but having the lower beds of the slopes 

 composed of Medina shales. On its northern side the escarpment extends 

 for six miles to Copetown ; but westward of this village it is covered with 



