near Mount Washington. 13 



As is well known, glaciers of the Alpine type widen the val- 

 leys which they occupy, converting them from winding Y-shaped 

 gorges into broad, straight, U-shaped troughs ; by a quarrying 

 process along the semicircular head crevasse or " bergschrund," 

 they cut steep headwalls which grow back farther and farther 

 into the mountain side. In their broader elements of form, 

 King, Huntington, Tuckerman, and the other ravines already 

 spoken of answer the description of true glacial cirques. In 

 one other respect they seem to be characteristic. Although 

 they are excavated in rocks of nearly uniform strength, their 

 floors do not descend steadily, but by steps. In Tuckerman 

 Eavine this is particularly noticeable about half a mile down 

 from the headwall, where the pocket-like recess of the upper 

 end opens into the wider, lower basin over a cliff which is fully 

 fifty feet high. The presence of glacial cirques on all sides 

 of the range is not surprising ; indeed it is quite to be expected, 

 although, as seems to be the case, there should be a greater 

 development of them on the east side than on the west because 

 of the lodgment of drifted snow on the leeward side. If 

 these are stream valleys which have been deepened and 

 widened by Alpine glaciers, it is not at all surprising that 

 among them are a few normal Y-shaped valleys like that of 

 Snyder Brook, which, owing to their situation with reference 

 to the drifting snows and protecting peaks, escaped the local 

 glaciation which the others suffered. 



The sculpture b} 7 these Mount Washington glaciers, although 

 not extensive enough to develop perfect examples of lateral 

 " hanging valleys," nevertheless approached that point. The 

 glacier which widened the Great Gulf cut off the lower ends 

 of several spurs of Mounts Clay and Jefferson, forming the 

 great triangular " knees." Between the two knees of Jeffer- 

 son is a hanging valley from which a stream cascades abruptly 

 into the Great Gulf. 



Age and extent of the valley glaciers. 



Those writers who have presented evidence in favor of the 

 existence of local glaciers among the New England mountains 

 have invariably drawn the conclusions that these glaciers made 

 their appearance after the withdrawal of the ice sheet, when 

 local snow fields still occupied the higher summits. Most of 

 the evidence which they offered is indeed capable of no other 

 interpretation. Freshly formed terminal moraines such as 

 Agassiz professed to find at Bethlehem,* northwestward stria- 

 ation reported by Professor Hitchcock, and similar surface 

 markings could hardly have been made before the ice sheet 



* Louis Agassiz : On the former existence of local glaciers in the White 

 Mountains, Proc. A.mer. Assoc. Adv. Sci., vol. xix, pp. 161-167, 1870. 



