640 CHARLES EMERSON PEET 



Evidence from, the altitude of Lake Iroquois. — Since this lake 

 drained into the Hudson water body, it follows that the Hudson water 

 body was lower than Lake Iroquois. The level of the latter has been 

 calculated at about 200 feet.^ It follows then that the Hudson water 

 body was less than 200 feet above sea-level, by the amount of fall of 

 the outlet stream from Lake Iroquois to the Hudson water body. 

 If the lower delta of the Mohawk described by Professor A. P. 

 Brigham at Schenectady (340 feet A. T.) was deposited by the 

 Mohawk and not by streams of ice- water from the ice-front,^ it would 

 require an average slope of this outlet stream of less than 2^ feet per 

 mile to permit the Hudson water body to be above sea-level. 



Amount of uplift of harrier south of Fort Edward since inaugura- 

 tion of Higher Glacial Lake Champlain. — Since the barrier is now 

 no more than 260 and no less than 220 feet A. T. it follows either 

 that the Hudson water body was above sea-level when the barrier 

 emerged from it, or, if it was at sea-level, there has been an uplift 

 of 220-260 feet since the inauguration of Higher Glacial Lake Cham- 

 plain. Since changes in the gradient of the outlet valley require 

 an uphft of 60 feet or so, since the close of Higher Glacial Lake 

 Champlain history,^ it leaves an uplift of 160-200 feet to take 

 place during the history of this lake. If there was this amount of 

 uphft during this time, then the Hudson water body was at sea-level 

 when the barrier which produced Higher Glacial Lake Champlain 

 emerged from its waters. 



ORIGIN OF HUDSON WATER BODY. 



There are two hypotheses to explain this water body. 



1. (a) The water body was a lake made by a barrier at the south. 

 (b) There was a succession of lakes made by a succession of barriers, 

 or by a migrating barrier. 



2. The water body was an arm of the sea. 



Aside from the deposits made in its waters there are four series 



1 Monograph 41, U. S. Geological Survey, p- 775- 



2 Bulletin of the Geological Society of America, Vol. IX (1898), p. 205. 



3 This is based on the assumption that the valley at Whitehall has not changed in 

 level and was 120 feet above sea-level when Higher Glacial Lake Champlain fell 120 

 feet to " Marine" Champlain level, and on a reasonable assumption as to the slope of 

 this outlet valley. 



