VALLEYS 453 



Canandaigua and Canaseraga valleys and opens broadly into the Cohoc- 

 ton- Way land valley at right angles, with a step up of 500 feet. A val- 

 ley which extends 4 or 5 miles south from Wayland may have once 

 been the head of Hemlock. The boundary walls of Hemlock valley 

 rise very steeply 500-900 feet, with slopes but slightly roughened by 

 more than 200 post-Glacial "gulls" or ravines. Its northern half is 

 occupied by a lake which presents within a space which can be em- 

 braced in one view the characters of a finger lake in an exaggerated 

 degree (figure 2, plate 38). It is 35,000 feet long, its width varies from 

 1,975 to 2,650 feet, its area is 1,828 acres, and its surface is 896 feet above 

 tide. It forms the public water supply of the city of Rochester, and by 

 the courtesy of the superintendent of the Rochester water works I was 

 enabled to make about 200 soundings and to determine with sufficient 

 .accuracy the bottom contours. The basin proved to be a simple boat- 

 shaped depression with very steep side slopes and nearly level bottom 

 rising gently toward each end. The maximum depth at a point south 

 of the middle is 90 feet. 



The lake fills the valley so completely as to leave no room for a coastal 

 plain or shelf. Except at numerous small points or deltas, the shores 

 rise from the water's edge at an angle of about 30 degrees, sometimes a 

 little more or a little less, and near the head of the lake reach an altitude 

 on either side of 1,000 feet above its surface within a distance of 1 mile. 

 On the west side the slope of 30 degrees continues to a height which varies 

 between 310 and 490 feet, where the angle changes abruptly to about 15 

 degrees. On the east side the slope is less steep, but the shoulder or 

 abrupt change of slope appears between 210 and 350 feet. This level is 

 conspicuous from the fact that the lower and steeper slopes are generally 

 forested, their upper edge being the limit of cleared land, and there most 

 of the smaller ravines begin (figure 1, plate 39). 



Hemlock outlet flows through a drift gorge with a fall of 120 feet in 5 

 miles to the north end of the Honeoye valley. 



Canadice Valley 



Canadice valley lies parallel with Hemlock on the east, being separated 

 from it by the drumlin-shaped ridge of Bald hill. It is 8 miles long, 

 three-eighths of a mile wide, and 850 feet deep. Its middle third is occu- 

 pied by Canadice lake, 3 miles long, one-fourth to three-eighths of a mile 

 wide, and having an area of 648 acres. The lake surface is 1,092 feet 

 above tide. Its basin is the counterpart of that of Hemlock, with a max- 

 imum depth of 84 feet. The general slope on the west side is nearly as 

 steep as that of Hemlock, but on the east side about one-half as steep. 

 Neither slope presents any oversteepening in the lower portion (figure 2, 



