l8o rochester academy of science. l^^^y 27, 



May 27, 1895. 



Vice-President J. M. Davison in the chair. Sixty persons 

 present. 



Mr. H. K. Phinney exhibited fragments of charred wood found 

 beneath four and one-half feet of drift in a sewer excavation in 

 Dartmouth street. 



The fifth and last lecture of the Popular Lecture Course, illustrated 

 by charts and lantern \iews, was delivered by the President, as 

 follows : 



GLACIAL LAKES OF WESTERN NEW YORK. 



By Professor Herman LeRoy Fairchild. 



[abstract.]* 



This paper was a description of the waters held at high level in 

 the north and south valleys between the receding front of the great ice 

 sheet and the north-sloping land surface. The plateau of central and 

 southwestern New York is deeply trenched by ancient stream erosion, 

 some of these valleys now holding the so-called "Finger" lakes. Each 

 of the trenches, whether now impounding water or not, was, during 

 the ice retreat, the site of a lake having as its northern barrier the ice 

 front and with its outlet southward across the divide into southern 

 drainage. The height of these ancient glacial lakes was that of the 

 lowest col or pass at the head of the valley, usually some hundreds of 

 feet above the present valley bottom. The channel cut by the drain- 

 ing stream appears on the southern side of each col and at correspond- 

 ing heights along the valley slopes are found the deltas built in the 

 lakes by the inflowing streams. 



To distinguish the ancient ice-dammed lakes from the existing 

 lakes in the same valleys the former are named after the chief towns 

 in the basins, or by prefixing the term "glacial." For example, the 

 glacial water in the head of the Seneca valley is called Watkins lake, 

 and it had its outlet through the site of Horseheads to the Chemung 

 river, with an altitude of 900 feet, or toward 500 feet above the present 

 Seneca lake. The ancient lake in the Canandaigua valley is Naples 

 lake ; in Keuka valley, Hammondsport lake ; in Cayuga valley, Ithaca 

 lake ; in Skaneateles valley, glacial Skaneateles lake. 



•The substance of this address is published in the Bulletin of the Geological Soci«ty of 

 America, Vol.6, pages 353-374. April. 1895, with six plates. 



