FEATURES OF THE HAMMONDSPOKT LAKE. 365 



The stream channel, which is fairly distinct, has an altitude, using the 

 Bath and Haniniondsport railroad levels as data, of about 1,125 feet. 



DEL TA S A ND WA TER-LE VELS. 



The levels are marked clearly in the terraces of the two stream deltas 

 at the head of the lake and in others along the sides of the lake. On 

 the conspicuous deltas at Hammondsport only two terraces are seen. 

 Taking Keuka lake as 718 feet, the broad plateaus of the deltas are 1,158 

 feet above sealevel, and the lower terrace, seen as a conspicuous but not 

 large shelf on the Laughlins Glen delta, is 911 feet. 



On the west side of the lake, one and a half miles from Hammonds- 

 port, is a high delta at the mouth of Snows glen ; at two and a half miles 

 is another at the mouth of Adsit Baileys gully (Malvareau point), and a 

 fine delta exists at Urbana. Others are said to occur at several stream 

 outlets farther down the lake. These deltas have not been measured, 

 but a careful estimate of the broad lower terrace of the Urbana delta was 

 made, with the conclusion that it was not far from 200 feet above the 

 water. 



Evidences of lake-action are not seen upon the steep slopes near the 

 head of the lake. The friable character of the shales is unfavorable to 

 the preservation of shorelines. The slopes are ravined at frequent inter- 

 vals, and the vineyards which make the locality famous are seamed with 

 many small gullies of recent origin. 



LAKE HISTORY. 



It is a simple story. While the ice-lobe was retreating the whole length 

 of the valley the water was held up to the top of the moraine divide, 440 

 feet above the present water-level. Toward the close of this stage the 

 lake was 24 miles long, 2 miles wide and 600 feet deep. When the low 

 ground at the north end of the valley was uncovered, the glacial lake fell 

 to the level of the Watkins (Seneca glacial) lake, which had an altitude 

 something over 900 feet. 



The W ATKINS Lake. 



SENECA VALLEY. 



This valley is of simple character, a single north-and-south depression, 

 with no branches or side cuts, and in general proportions it resembles 

 the Cayuga valley. The present Seneca lake is 88 miles long, from one 

 to three miles wide, and the southern half averages 500 feet deep. At 

 the south end of the lake and at the head of the valley the land on either 

 side rises steeply from the water for 500 feet, and then in more gentle 



