PHYSIOGRAPHY OF THE ADIRONDACKS. 



207 



of east and west and north and south valleys and by the rearrangements 

 of the older drainage by the glacial drift. When the streams sought 

 to occupy their old north and south channels on the retreat of the 

 ice they seem to have been forced in instances by newly acquired bar- 

 riers to run in an easterly direction across old but low divides and then 

 to utilize parallel north and south lines of drainage. 



Lakes. — The Adirondack region, like all the recently glaciated 

 country, teems with lakes which can he observed in all stages from 

 those of large size like Champlain, George and Schroon, through 

 smaller ones, to those little more than a morass, and finally to cultivated 

 meadow land upon the abandoned bottoms of departed ones whose 

 deltas and terraces stand out clearly. Lake Champlain is the largest 

 and has a total length of 150 miles. It has been recently studied in 

 detail by Professor J. B. Woodworth. It is obviously an old river val- 

 ley, probably modified somewhat by recent faulting and ponded by some 

 barrier of recent formation at the north. Lake George is next in 

 size and is apparently compounded of two earlier valleys, whose divide 



Fig. 12. Ausable Chasm, whose zig-zags are due to faults and joints. The walls are hard 



Potsdam quartzite. 



