Presidential Range of the White Mountains. 459 



time at least by the great ice sheet. The bowlder clay is much 

 looser and much more largely composed of fragments of the 

 local rock than that at lower altitudes, suggesting that the sum- 

 mit of this highest mountain of New England was not very 

 long nor very deeply covered by the ice sheet. 



Mounts Jefferson and Adams, whose altitudes are approxi- 

 mately 5800 feet, represent a rather different type of cone. 

 Their summits are not rounded like the dome of Washington, 

 but distinctly angular ; and their eastern sides are much more 

 precipitous than their western ones. On Mount Jefferson this 

 asymmetry is very pronounced, as those have noticed who have 

 approached the mountain from the northeast by way of the 

 Gulfside or Randolph Trails. It seems at first sight as if the 

 lack of symmetry were due primarily to the regional glacia- 

 tion, which was here in a southeastward direction. The detach- 

 ment of loosened blocks and talus on the lee side of these high 

 cones would have left cliffs where ledges do occur, while the 

 removal of talus and newly quarried blocks from ascending 

 slopes on the northwest sides would naturally be slow and im- 

 perfect. It is not clear, however, how the ice sheet, passing 

 over these cones from northwest to southeast, could steepen 

 their southeast sides so much and at the same time fail to wear 

 down to rounded outlines their summits. The form of the 

 mountains differs from that of typical roches moutonnees 

 chiefly in this angularity of their summits. The argument 

 against regional glaciation as the controlling factor in the form 

 of the cones finds further support in the symmetry of the 

 sharpest and steepest of the peaks, Mount Madison, which, let it 

 be noticed, is also the lowest, and hence the one which must 

 have been most deeply covered by ice. Inasmuch as this peak 

 is 900 feet lower than the top of Mount Washington, it ca'n 

 hardly have been buried by less than 1000 feet of ice, yet its 

 symmetry is nearly perfect and its sharpness highly con- 

 spicuous. "We must conclude, therefore, that the ice sheet has 

 had little influence on the shape of these cones. They may be 

 regarded rather as products of subaerial wasting. 



The Cols. — In the cols between the peaks the evidences of 

 severe glaciation are clear. Ledges at the " parapet " south- 

 west of Mt. Madison, and others just north of the Gulfside 

 shelter east of Mt. Jefferson, particularly, exhibit beautifully 

 rounded northwest sides and ragged southeast faces. Among 

 them are quartz veins whose polished surfaces bear distinct 

 hair-like striae of the southeastward ice flow. Since these points 

 are only a little below the 5000-foot contour, it is clear that the 

 more severe scrubbing of the ledges in them than of those on 

 the summits of cones like Madison is due not so much to a 

 greater thickness of ice as it is to the concentration of flow 



