l6 NEW YORK STATE MUSEUM 



this southern extension is drained by Quacken kill which joins 

 Poesten kill, the latter stream discharging into the Hudson river 

 at Troy. It is inferred that in preglacial times a stream heading 

 near Raymertown flowed southward, developing the valley which 

 now forms the intervale area and that at the close of the Ice Age 

 a barrier of glacial deposits was left across this valley at the place 

 where the divide now occurs, about 1^2 miles from the edge of the 

 sheet. Waters were ponded north of this barrier and this glacial 

 lake had its outlet in a stream that flowed past Raymertown and 

 emptied into Lake Tomhannock. This outlet ^stream had a fall of 

 100 feet and, through downcutting, the lake was finally drained off. 

 The axis of drainage of the two glacial lakes thus led to the exten- 

 sion of Tomhannock creek southward to its present source. 



A chain of small glacial lakes occupying depressions in the gen- 

 eral surface of the country developed in the region southwest of 

 Rice mountain beginning south of Haynersville. These were 

 eventually drained away by Deep kill, which has cut a deep gorge 

 on the eastern flank of the mountain. On the map two of these 

 areas have been designated as extinct lakes and the others as 

 swamps, the latter being partially covered with standing water. 



Lake Hoosic. There is quite good evidence that a temporary 

 glacial lake existed in that portion of the Hoosic valley crossed by 

 the eastern margin of the sheet. North of the river there is a 

 plain, traversed by Whiteside brook, the materials of which are 

 sand and fine gravel. They are distinctly stratified in arrange- 

 ment as shown in cuts along the Greenwich and Johnsonville Rail- 

 road. The general elevation of this plain is 420 feet. South of the 

 river in the neighborhood of Johnsonville the surface materials are 

 of sand and gravel character and in places rise to about the same 

 level as the plain opposite. 



It is believed that these deposits represent a glacial lake, the 

 waters of which gathered behind a dam across the preglacial Hoosic 

 valley made by drift, or deposits from the ice sheet. About a mile 

 below Johnsonville till rises from the left bank of the river to the 

 440-foot level and on the opposite side there is a hill of till 420 feet 

 in elevation. The latter hill slopes toward the river, the stream 

 curving at its base. It is inferred that a mass of till of which these 

 hills are remnants originally extended across the valley forming a 

 dam behind which the waters were held in check, converting this 

 portion of the valley into a temporary lake. 



