Glaclation of Mountains^ etc. — W. Upham. 211 
its striie have been obliterated by weathering.'' Professor 
Fay also informs me that the top of this mountain and of 
several other prominent peaks visited by him in the Adiron- 
dacks are all similar in aspect to Monadnock, none belonging 
to the type of Katahdin and Washington. The contoured 
map of Mt. Marcy, drafted by Mr. Colvin shows that it is much 
steeper on the east and south than on the north and west, as 
would be its form under glaciation from the northwest, like 
the mountains of New Hampshire and Vermont. 
This summit lies about one hundred and twenty-five miles 
west, and a few miles south, of .Mt. Washington ; and its dis- 
tance north from the terminal moraine on Long and Staten 
islands is about two hundred and thirty-five miles. The 
average slope of the surface of the ice-sheet from its termina- 
tion to the Adirondack mountains, was, therefore, not less 
than twenty-three feet per mile ; and from the Catskills, where 
the upper limit of glaciation is known, it was not less than 
seventeen feet per mile. How much it may have exceeded 
these figures cannot be determined, but what we know of 
Katahdin and Washington shows that the peak of Marcy 
doubtless lacked only a little of rising above the ice-sheet at 
its time of maximum thickness. In this connection it is to be 
remarked that the change from a northward ascent of about 
thirty feet per mile south of the Catskills, to an average of 
seventeen feet per mile, or slightly more, for the next hundred 
and thirty miles to the Adirondacks agrees well with the 
slopes of the Greenland ice-sheet observed by Nordenskiold, 
and with the northward ascent of the ice surface assumed by 
Dana in the computation above mentioned, namely, an 
average of ten feet per mile for the distance from the inter- 
national boundary to the watershed north of the St. Law- 
rence. 
Dr. R. P. Stevens states that along the valley of lake Cham- 
plain the general direction of the stria3 is in parellelism with 
the valley from north to south, but with local deflections to 
the amount of 20°. On the higher hills and mountains near 
the west side of this lake, including some of the eastern Adi- 
rondacks, he finds the striation to be more commonly from 
northwest to southeast, which is also its direction in the 
* Seventh Annual Report of the Topographical Survey of the Adiron- 
dack Region, to the year 1879. 
