GLACIAL DRIFT. 203 



where the course of the valley corresponds with that of the neighboring 

 striae. 



The south-east courses commonly occur upon the most elevated moun- 

 tains, both in New Hampshire and Vermont. The whole Green Moun- 

 tain range, and the loftier Presidential line of White Mountain summits, 

 show this direction of marking. Scarcely any other course is known in 

 Coos county, and it is common all through the Lake and Coast districts, 

 including Essex county, Mass., and all the mountains of the Monadnock 

 type. On comparing these courses over so much of New England with 

 the customary south-east course of the valley of the St. Lawrence, one 

 perceives a very striking contrast, and has the difficult problem of the 

 course of the south-east current set sharply before him. How could the 

 ice-sheet climb the highest New England mountains from the low St. 

 Lawrence valley, and then press onward to the sea ? I will not attempt 

 the answer at present, but offer, in the first place, our reasons in full for 

 believing the ice current passed over the summit of Mt. Washington. 



Evidences of Glacial Action upon Mt. Washington. 



As this is the highest summit in the whole glaciated area of North 

 America, geologists have been greatly interested in examining its sides, 

 to note how far the ice-marks could be found. The most important visit 

 in that regard was that of my father in 1841, and the observations then 

 made universally accepted. Most other geologists have visited the moun- 

 tain, but have had no occasion to publish anything about the phenomena. 

 My father, in 1841, became greatly interested in drift phenomena, and 

 visited the White Mountains for the purpose of determining the limits of 

 the ice-action. He came from Conway through the Notch, passing up 

 the Crawford bridle-path. "Along the whole course of the valley," he 

 says, "I noticed rather fewer of the phenomena of drift than in most of 

 the mountain valleys of New England." After describing the route of 

 the path, he says, — 



All the peaks which I ascended are made up of broken fragments of this slate, which 

 have been entirely removed from their original position by frost, and form sometimes 

 a coating of loose angular blocks several feet thick. This is particularly the case upon 

 the summit of Mt. Washington, and downward about 1,000 feet [see frontispiece, vol. 

 i] ; but in all the valleys between these peaks more or less of the rocks appear in place, 



