176 NEW YORK STATE MUSEUM 
consequent course determined by glaciation and sedimentation have 
been worked out by the physiographers with sufficient accuracy to 
enable one to distinguish normal effects from those produced by the 
combined action of a stream and a stream bed or banks which are 
liquifying. With regard to the ice, in lieu of opportunities for 
direct study, what it actually did at the terminal position is prob- 
ably the best obtainable guide to what it was capable of doing, and 
it does not seem likely that a few miles of recession would enable it 
to develop a flexibility which it did not possess at its maximum 
extension. Many of the protrusions from the general line of front 
which have been noted by investigators. undoubtedly existed, but 
the idea that they represent minature lobes of active ice, rather than 
stagnant shreds, is merely a part of the general preconception that 
the receding and melting ice continued to move southward to the 
very last. 
It will be understood that in the ,ablation of even a motionless 
glacier, a kind of recession can be made out; and that here and, there 
very striking proof of the former presence of abrupt distal margins 
may be found, like the contact mentioned above which turns Esopus 
creek northward. Like the valley-head deposits of the Finger Lakes 
region this contact descends northward some 150 feet in about one- 
half mile. There can be, then, no objection to the use of the 
terms “ retreat ” and “ice front” so long as the implication of glacial 
motion is avoided. Such a recession is complicated (1) by the per- 
sistence, mostly at low elevations, of masses of ice which have been 
covered by superglacial drift, and (2) by the early breaking up of 
parts of the ice field far back from its edge, by the hydrostatic pres- 
sure exerted by waters accumulated about elevations protruding 
above the thinning glacier. But for the most part, the ragged margin 
of the main body of the ice was melted off progressively from south 
to north. It would not seem, therefore, that the possible contempo- 
raneity of laminated clays as far separated as, for example the 
southern foothills of the Adirondacks (Little Falls quadrangle) and 
the northern end of Shawangunk mountain (noted above), would, 
of necessity, vitiate the value of the chronology worked out by 
Antevs'® on a basis of such clay laminae. 
1% The Recession of the last Ice Sheet in New England. Amer. Geog. 
Soc. Research Series No. 11, New York City, 1922. 
