1 8() W. J. MILLER PREGLACIAL COURSE OF UPPER HUDSON RIVER 



water conditions here. The line of contact of this lake at its height with 

 the surrounding land is pretty accurately shown by the 760-foot contour 

 line, but because of post-Glacial changes of level in this region the writer 

 can not state the elevation of the lake surface above sealevel. The lake 

 deposit has been deeply trenched by both the Hudson and Schroon rivers, 

 and as a result of the cutting down process many fine terraces have been 

 formed. The main body of water showed its greatest . width of about 3 

 miles on a line passing east and west through Warrensburg. However, 

 clearly defined sand terraces, the highest of which always rise close to the 

 760-foot contour line, prove that important arms of this lake extended 

 nearly 8 miles above Warrensburg along the Schroon Eiver, nearly 4 

 miles up the Hudson above the mouth of the Schroon, li/^ miles up Pat- 

 terson Brook, and at least 2 miles down the Hudson from the mouth of 

 the Schroon. 



In the vicinity of Warrensburg, and especially up the Schroon Eiver, 

 the lake deposits, though deeply trenched, have seldom been cut through 

 to the underlying rock. In the Stony Creek gorge there are good sand 

 terraces considerably lower than 760 feet, and these are probably con- 

 nected with the deposits of a Glacial lake (not studied by the writer), 

 which extended down the Hudson and over the region around Corinth. 

 The channel throughout the Stony Creek gorge is mostly, if not entirely, 

 filled with sand and gravel deposits. Where the Sacandaga crosses the 

 pre-Glacial divide at Conklingville the channel is filled with loose sedi- 

 ment, borings by the New York Water Supply Commission showing a 

 depth of over 200 feet before striking rock. 



The writer believes that these examples of channels filled with loose 

 sediment afford a strong argument in favor of more than one advance 

 and retreat of the ice in this part of the State. On the basis of a single 

 advance and retreat of the ice, it seems necessary to assume that the deep 

 narrow gorges at Stony Creek and Conklingville were produced entirely 

 by ice erosion, and this seems highly improbable, especially in the case of 

 Conklingville, where the direction of ice-flow was decidedly unfavorable 

 for any considerable ice-cutting. A far more reasonable explanation 

 allows for a large amount of stream erosion in the production of the 

 gorges. Thus the gorges most likely attained much of their depth by 

 stream erosion during inter-Glacial time, and during the final retreat of 

 the ice these channels were more or less choked with loose sediments, 

 which the streams have been unable to completely remove during the 

 short post-Glacial time. Such inter-Glacial stream erosion, combined 

 with ice erosion, as above explained, also satisfactorily explains why the 

 Hudson and Schroon Eiver channels at Warrensburg are so much lower 

 than the pre-Glacial Hudson channel between Warrensburg and Caldwell, 



