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 barriers 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 valley, 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.
