458 NEW YORK STATE MUSEUM 



westward, faults are not so prominent as to the east, and the general 

 altitude diminishes in that direction. 



There was a minor period of igneous activity, in all probability 

 of this date, which affected the country east and north from the 

 Champlain valley, but not greatly to the west, and no rocks of this 

 date are known in the area of the quadrangle. The general result 

 of this period of disturbance was to considerably increase the 

 altitude of the interior region. 



A long period of comparative stability of level seems to have 

 followed, sufficiently long to have permitted of the wearing down 

 of the whole region to a rather uniform, low altitude,. broad valleys 

 with rather low, insignificant divides constituting most of the 

 surface. Numerous hills were however left, with altitudes often 

 several hundred feet above the general level. Following this a 

 general increase in altitude occurred, greatest along the present 

 main axis of elevation, and with likely renewed slipping along the 

 faults on the Champlain side of the axis. The uplift renewed the 

 cutting power of the streams and they excavated the present valleys 

 of the region, the hills representing remaining portions of the pre- 

 vious surface. No doubt many minor changes occurred during 

 this long period, but as mere episodes in comparison with the two 

 greater movements. 



Then followed the recent period of cold, and of ice advance over 

 the region. How many advances and retreats of the ice sheet 

 occurred across the Adirondacks can not be told, since the last 

 advance obliterated all traces of its predecessors, at least no traces 

 of them have yet been discerned. The ice plainly covered the 

 region to a depth sufficient to submerge even the highest hill tops, 

 and persisted for a considerable time. It did a respectable amount 

 of erosion, and, when retreating, covered the country unevenly 

 with glacial deposits. On its final disappearance it left the topogra- 

 phy modified somewhat, owing both to wear and to deposit, but 

 with its larger topographic features little changed. Ridge slopes 

 were smoothed, summits rounded, valleys clogged with deposit, 

 lakes produced either by inequality of deposit or by local excessive 

 downward erosion, stream courses more or less modified, a host of 

 minor changes in detail, much altering the general appearance of 

 the region. 



At the time of final disappearance of the ice the region had an 

 altitude somewhat lower than at present, the amount in the quad- 



