312 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. e 
N. Y. This smaller lake has been called Lake Vermont, or Glacial 
Lake Champlain, for from this beginning it continued to extend 
northward across Vermont in the Champlain valley as the ice-front 
retreated. The highest level of this lake was determined by an 
outlet just east of Quaker Springs, N. Y. This stage of Lake Ver- 
mont, Woodworth (according to a verbal statement to the writer) 
would now call the Upper Coveville stage. A rather gradual lowering 
of this lake took place until an outlet near Coveville, N. Y., at a level 
100 feet lower, inaugurated a period of nearly constant level, known 
as the Coveville stage. The ice-front now stood somewhere between 
Port Kent and Street Road, N. Y.* (opposite the southern third of 
the Vermont area which is under consideration). 
After the lake stood for some time at this level, during which time 
the ice-front was continuing to retreat, another outlet, through the 
valley of Wood Creek, took the drainage of the lake and lowered 
the lake-level another 100 feet. This is the lowest outlet which has 
been discovered for Lake Vermont. The probabilities are that the 
subsequent lowering of the lake-level was caused by the leaking out 
of water toward the north, around or beneath the ice. When the ice 
no longer formed a barrier across the northern end of the Champlain 
valley the sea had free access to the present site of Lake Champlain, 
owing to the fact that the land was depressed at the north. The 
amount of depression at the site of the present foot of Lake Cham- 
plain was about 450 feet. This depression was of the nature of a 
tilting, for the head of Lake Champlain was not then below sea-level. 
Since the sea first came into the valley there has been uplifting at the 
north so that the shore-lines developed at that marine stage are now 
inclined toward the south at the rate of about 3.65 feet per mile.” 
This tilted plane is the upper marine limit. 
All the shore-lines made at the different stages of Lake Vermont 
participated in this upwarping, so they also slope southward. 
PRELIMINARY Dara.-— Determination of Altitudes. Altitudes were 
determined by means of the aneroid barometer and hand level, using 
such reference points as could be found in Gannett’s (1906), Dictionary 
of altitudes, and on the Burlington and Middlebury topographic sheets- 
Glacial Striae. Some idea of the final movements of the glacial 
ice in the valleys, as a clue to the position of possible ice barriers as 
parts of shore-lines, seemed highly desirable. For this reason glacial 
striae were mapped whenever encountered. 
1 Woodworth, 1905, p. 196. 
2 This figure was obtained from calculation based on the profile, Plate 28, of Wood- 
worth’s report (1905, p. 226). 
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