﻿Pennsylvania during the Glacial Epoch. 363 



have examined are destitute of drift deposits." Professor H. 

 C. Lewis also refers* to these peaks as having stood up as 

 islands in the sea of ice. He refers f to the evidence of ice 

 action on the summit of Penobscot Knob, in Luzern County, 

 at an elevation of 2,220 feet above tide, only twenty feet higher 

 than the limit mentioned by Professor White. These, then, 

 are the highest points in the State of Pennsylvania at which 

 unquestionable evidences of ice action have been observed and 

 recorded, namely : at 2,200 feet by Professor White upon the 

 sides of the high peaks, and at 2,220 by Professor Lewis upon 

 Penobscot Knob. 



Having given attention to the glaciation of the region under 

 consideration,^: I was deeply interested, upon visiting this part 

 of the State in July of the present year, to see and examine for 

 myself the evidences of the thickness of the ice upon the sides 

 of Elk Mountain, said to be the highest point in northern 

 Pennsylvania. 



Ascending this mountain by the path leading to the south 

 knob, I found upon the ledge of rocks forming the principal 

 outlook over the surrounding country, well denned glacial 

 strias. Those upon the east side of the ledge bear S. 60°-65° 

 W., while those upon the west side bear S. 70°-72° W., mag- 

 netic. Professor White makes the elevation of this point 2,400 

 feet above tide. This observation alone therefore indicates 

 that the ice was thicker than Professor White supposed. 



Ascending to the summit of the south knob, I found nothing 

 along the brushy sides of the peak to indicate ice action. On 

 the summit itself, now covered with woods, the decay of the 

 rocks has left nothing, as far as I could see by hastily made 

 observations, to show whether or not the peak was ever covered 

 by the ice. In the hope of finding a more resisting rock, and 

 consequently something more conclusive, upon the higher 

 north knob, in company with Professor Dudley, of Cornell 

 University, Mr. D. N. Green, of Scranton, and with several of 

 the younger members of my class in geology, I visited that 

 part of the mountain which lies a mile farther to the north. 



As the whole of the upper part of these peaks is covered 

 with a thick undergrowth of bushes and briars, it is not possi- 

 ble, while the plants are in full foliage at least, to get any idea 

 of the arrangement of loose material about the sides or summit, 

 or of the best places to see the rocks in position. My observa- 

 tions, therefore, were confined to such fragments and outcrops 

 as we happened upon in passing from one peak to the other. 



* Report Z of the Second Geol. Survey of Penn., pp. 14, 15. 



f Report Z, p. 106. 



% " Glaciation of trie Wyoming and Lackawanna Valleys," in Proc. American 

 Philosophical Society, 1886, No. 123, pp. 337-357; and Glaciation of the Lacka- 

 wanna Valley, in Proc. A. A. A. S., vol. xxxiv, p. 212. 



