436. NEW YORK STATE MUSEUM 



of the typical cirque shape, and always strongly "suggestive of 

 glacial action [pi. 17]. Precipitous rock clllfs are always a 

 feature on this side, while wholly absent on the gentle north 

 slopes,, on which rock outcrops of any sort are infrequent. The 

 .writer has often searched the north slope of such a ridge without 

 finding a single satisfactory outcrop, while they are certain to be 

 abundantly found when the summit and back slope are reached. 



In the high Adirondacks, in the anorthosdte region, these 

 features are not found, the cirques excepted, and these are found 

 along the flanks of the ridges as well as at the back. Stony 

 Creek mountain [pi. 17] is an anorthosite mountain and on the 

 edge of the high peak district, but it exhibits the general 

 features just noted very imperfectly. They are better shown in 

 many of the syenite peaks and in the main iseem confined to the 

 ridges of foliated rocks. The syenites always show more folia- 

 tion than the anorthosites'. Yet the writer has been unable to 

 discover any connection between the strike and pitch of the 

 foliation and the trend and pitch of the ridges; and, if any such 

 does exist, it is obscure, though the facts noted above suggest 

 some relationship. 



That much of the shaping of the ridges has been done by 

 glacial action seemis clear. The northern hills are the ones 

 mainly concerned, those so situated that they would feel the full 

 force of the onset- of the south west war dly moving ice, after its 

 advance, unimpeded by any obstacles, over the plain to the 

 north. It must have impinged heaviily on the north slopes of 

 the hills, and the basal currents moving up the intervening 

 valleys must have closely hugged the ridge sides. There would 

 be at first a tendency to wear down all projections, and later to 

 fill up depressions and blanket the slopes with till and moraine 

 stuff. The lee isdde of the ridge, however, would not be closely 

 enfolded by the ice, so that little smoothing would be done 

 thefre. In the waning stages of the ice sheet a 'bergschrund, or 

 crevasse between the ice and the back slope of the mountain, 

 would be formed, in which a daily variation of the temperature 

 from thawing to freezing would take place during a large part 

 of the year, which would cause a rapid scaling off of the rock 

 along the joints, producing rough, steep cliffs. During the wan- 



