REPORT OF THE DIRECTOR, 1922 175 
as a criterion of the absence of glacial movement. The same argu- 
ment applies to all the deposits examined in this area from the High- 
lands to the Hoosick river. Everywhere is the evidence of stagnant 
ice melting im situ, and nowhere was the suggestion of a receding ice 
front rendered probable. 
Areas of dead ice do not seem to have been much noticed and in 
consequence comparatively little attention has been given to the 
evidences which they have left or the character of the deposits which 
are associated with their ablation. The work of Salisbury, already 
referred to, contains a good general description of the phenomena 
in English. Of the German Geologists, Schneider’® has given an 
account of the melting off of such a mass in Hinterpommerania, and 
Gagel*® has described high level lake waters over the Masurian 
Plateau in East Prussia which could have been confined only behind 
the stagnant margin of the last ice sheet. The available literature 
does not appear to be voluminous and yet the subject is of sufficient 
importance to merit the attention of geologists working at the inter- 
pretation of the Pleistocene deposits, for the more general problems 
of the contemporaneous diastrophic movements depend for their 
solution largely upon the evidence furnished by warped and tilted 
water planes. And if open waters are not distinguished from areas 
partly occupied by stagnant ice, the value of the criteria will be 
greatly lessened. 
Conclusion and Summary 
In reviewing the literature in the light of the conclusions here set 
forth two points have impressed the writer as deserving of mention. 
The a priori assumptions of different investigators as to just what 
kind of effects can be produced by flowing water under varying 
circumstances of load, grade and volume differ greatly. Also the 
a priort assumptions made concerning the degree of plasticity 
exhibited by the marginal zone of an ice sheet in retreat grade from 
a conception of ice so rigid that only the major features of the land 
topography can affect its course, to a willingness to believe it capable 
of turning aside and thrusting long shoestring shaped tongues up 
side valleys. With regard to the stream action it need only be 
said that the laws governing the development of a new valley over a 
*% Bericht tiber die Aufnahme der Blatter Boissin und Bulgrin in Hinter- 
pomern. Jahrbuch der Kel. preuss. geolog. Landesanstalt, xxvi (1905), 
S. 705-10. 
™ Tie letzte, grosse Phase der diluvialen Vergletscherung Nord-deutsch- 
- lands. Geologische Rundschau (Leipzig), Band vi, Heft 1 & 2, 1915, S. 
86-87. 
