64 NEW YORK STATE MUSEUM 



lake, and also some 6 or 8 miles southward covering all the lowland 

 around Chestertown and an arm extending over the area of the 

 present Brant lake. Piseco lake was at one time 20 feet higher, 

 when it reached several miles farther northward. Both of these 

 lakes lie in valleys which are largely due to faulting as explained 

 above. The waters of both are now held up by dams of loose 

 glacial debris across the south ends. 



Lake George is justly famous because, from the standpoint of 

 length and depth in proportion to width, no other lake in the State 

 occupies such a remarkable valley. This depression has been pro- 

 duced by a combination of faulting and erosion. There was a pre- 

 Glacial divide at the present location of the " Narrows." This 

 divide may have been considerably lowered by ice erosion when the 

 deep, narrow body of ice plowed its way through the valley.- The 

 waters are now held up by glacial deposits at each end. 



Lake Placid occupies the bottom of an irregular preglacial valley. 

 The lake has been formed by heavy glacial deposits across the valley 

 on the south. The very low neck of land separating it from Mirror 

 lake is also glacial material. 



The Saranac lakes. Big Tupper lake and Cranberry lake are large 

 bodies of water of very irregular shape in shallow basins resulting 

 from .the accumulation of glacial debris across broad, preglacial 

 valleys. 



Raquette lake, with its exceedingly irregular shore line, lies in 

 the bottom of a broad, shallow preglacial valley or rather portions 

 of several adjacent valleys. Heavy glacial deposits on the south 

 act as a dam. 



Both Long lake and Indian lake, two fine examples of the linear 

 type of lake, lie in the bottoms of very straight valleys which have 

 been carved out by erosion along fault zones of weak rock. Much 

 of the present extent of Indian lake is due to an artificial dam across 

 the northern end. 



The Fulton chain of lakes are the result of irregular damming of 

 prominent preglacial stream valleys by glacial debris. 



Blue Mountain lake, Lake Pleasant and Sacandaga lake all lie in 

 the bottoms of valleys which appear to have been carved out of 

 relatively weak Grenville strata, the waters being held up by glacial 

 debris dams. A low, narrow neck of glacial material serves to 

 separate Lake Pleasant and Sacandaga lake. 



Extinct lakes. Hundreds of extinct glacial lakes are known to 

 be scattered throughout the Adirondacks. Some of these existed 

 only during the time of the ice retreat where the ice acted as dams 

 across valleys, while others existed for a greater or lesser time after 



