FEATURES OP THE DANSVILLE LAKE. 359 



on old profiles as 1,203 feet. This is not at the head of the Canaseraga 

 creek, which has its source some miles further northwest beyond the vil- 

 lage of that name. 



The ground at and beyond the cols has not been studied by the writer 

 with reference to this subject, and the stream channels of the lake outlets 

 cannot be here described. 



DELTAS AND WATER-LEVELS. 



The successive levels held by the Dansville lake may be determined 

 not only by the remnants of delta terraces at the head of the main valley, 

 but by those made by numerous brooks pourmg down the steep sides of 

 the valley all the way to Mount Morris. The slopes are too steep to pre- 

 serve any beaches. 



The principal level is found at about 1,250 feet. This forms a gravel 

 plateau either side of Stony Brook glen, and the railroad station of that 

 name on the Central New York and Western railroad is located on it. 

 This level is prominent at Conesus village, on the east side of the Conesus 

 basin, and may be seen all about the valle3^ 



The Canaseragft-Stony Brook delta has been cut by both streams to a 

 depth of 200 feet and has been almost destroyed. Between the two 

 streams, however, is left a strip, which toward the delta front is a quarter 

 of a mile wide and a mile long, and gives good lower terraces. The 

 higher levels are too much eroded to be clear, and at one point the strip 

 is only a " hog-back." At 915 feet it is a broad, cultivated plateau, and 

 the terminus is similar, with an altitude of 894 feet (Clark terrace). The 

 altitudes were taken by spirit-level, using as datum-points the railroad 

 levels, which are subject to some revision. 



The 894-foot level is found in a well marked terrace on the east side of 

 Stony brook, and can be located at other points. In the side of the strip 

 of delta which is on the property of Anson Whiting, on the west side of 

 Stony brook, is a shelf about 300 feet wide, a quarter of a mile long and 

 at an altitude of 849 feet. A delta-point at Culbertson glen, on the Dela- . 

 ware. Lackawanna and Western railroad, midway between Dansville and 

 Groveland stations, is at 853 feet, and other terraces visible along the steej^ 

 slopes of the valley seem to be at about this level, which is the lowest 

 well marked lakelevel observed. Lower levels are seen as stream flood- 

 plains. The two conspicuous levels in and about the valley are, one at 

 about 1,250 feet, tlie other ranging above and l)eloAV 900 feet. 



LAKE fUSTORY. 



Perkinsrille Lake. — For a brief time a smaller lake must have occu- 

 pied some part of the southeast branch, with outlet near Wayland into 

 tlio Cohocton over the col 1,304 feet higli. As it covered the site of 



