144 PROCP^EDINGS OF 'rilE ALBANY MEETING 



In the Yellowstone Park only relatively fresh drift, of Wisconsin or post- 

 Wisconsin age, was noted along the stage route. It is doubtful, however, if 

 the entire park area was glaciated at the Wisconsin stage. The Madison 

 plateau may have escaped this glaciation, but have been reached by an earlier 

 one. Investigations were not carried into that part of the park. 



In North Dakota the pre- Wisconsin drift in the vicinity of the Missouri 

 River has well preserved moraines and the drift forms a veneer on rather steep 

 slopes as well as on hilltops and valley bottoms. The preservation of the.^e 

 morainic features and of the deposits on the hillsides seems to indicate an 

 Illiiioiaii or lowan age rather than Kansan, 



Pi'eseiited in abstract extemporaneously. 



Discussion 



Prof. G. F. Wright : The glacial accumulations near Spokane, so far from 

 the recognized glacial area, are certainly of great significance. A similar 

 isolated accumulation of glacial material has just been reported to me 40 or 50 

 miles south of generally recognized limits of Kansas drift. All this indicates 

 that the "attenuated border" is much more attenuated than we have been ac- 

 customed to suppose. It is, however, well known that this attenuated border 

 occasionally has large areas where glacial material is absent. 



Further remarks were made by Prof. W. W. Atwood. 



SNOW ARCH IN TUCKERMANS RAVINE ON MOUNT WASHINGTON 

 BY JAMES WALTER GOLDTHWAIT 



(Al)stract) 



The famous snow bank at the head of Tuckermans Ravine, which usually 

 lingers into mid-summer, vanishing late in August, probably comes nearest to 

 being a local glacier of all the snow banks of the eastern United States. Its 

 bulk, its compactness, and its situation in the shadow of the headwall of a 

 cirque have suggested that although it is feeble and not usually perennial this 

 snowdrift is glacier-like in its movement. This idea seemed to be confirmed 

 by an experiment made in 1879 by William H. Pickering, who reported that 

 stones placed in line on the top of the snow bank shifted position at a rapid 

 rate, and drew the conclusion that in early summer the snow mass does moA e 

 like a valley glacier. If this conclusion is correct, it raises the question whether 

 Tuckerman's Ravine and other cirques on Mount Washington have been carved 

 out by typical valley glaciers, as the author has supposed, or by a process of 

 nivation, augmented by landslides and torrent work, as others have thought. 



A repetition of Pickering's exi)eriment, last July, on the snow bank, checked 

 by other observations, seems to prove that this drift has no movement of its 

 own, but that the phenomena attributed to a movement of the whole mass are 

 due, instead, to surface ablation and consequent sliding of objects down the 

 inclined surface of the drift. The snow arch is therefore to be regarded not 

 as a miniature glacier, annually recurring on the site of the old, but as the 

 lifeless ghost of that glacier. 



Presented in abstract extemporaneously. 



