18 J. W. Goldthwait — Glacial Cirques 



the same rate, it must be borne in mind that the disappearance of 

 the ice sheet from New England was due to the re-establishment 

 of a climate unfavorable to glaciation, and that by the time the 

 outer margin of the ice sheet had melted back from Long Island, 

 200 miles to the White Mountains, the climate may have be- 

 come nearly the same as the climate of to-day. In that case, 

 local glaciers of recent date would be absent. On the other 

 hand, while the establishment of a severe climate with heavy 

 snowfall was causing the ice sheet to spread southward from 

 Labrador towards New England, there must have been plenty 

 of time for local glaciers to grow up on the White Mountains. 

 The extent of these local glaciers cannot at present be 

 stated. Field investigations on other ranges of the White 

 MountainSj which are contemplated, should throw light on the 

 question. A mass of evidence adduced by Agassiz and Hitch- 

 cock to demonstrate local glaciation, particularly in the upper 

 Ammonoosuc valley, must be studied again before their conclu- 

 sions and those drawn in the present paper are reconciled or 

 proved faulty. The northwestward movement of pebbles 

 and bowlders, reported by Professor Hitchcock,* deserves 

 special scrutiny since upon it rests the main burden of proof 

 that local glaciers extended far and wide through the White 

 Mountains. What little was seen last summer of mountains 

 near the Presidential Range does not encourage the hope that 

 cirques like those near Mount Washington will be found on the 

 other ranges. With this idea the form of the Mount Washing- 

 ton ravines is in full accord. They seem to terminate rather 

 abruptly near the base of the range, instead of finding con- 

 tinuation down the Randolph valley and the Glen. They 

 appear, in short, to represent so many separate cirque glaciers 

 rather than the united tributaries of extensive glacier systems. 

 It is not altogether clear, however, but that the smoother and 

 milder form of these lower trunk valleys may be due to heavy 

 glaciation by the continental ice sheet, which has removed the 

 sharp angles and shoulders from those slopes which were most 

 deeply buried by ice. 



Summary. 



The peculiar cirque form of certain "ravines" or "gulfs" on 

 the Presidential Range seems accountable only through the for- 

 mer existence in them of local glaciers of the Alpine type. 

 These glaciers, however, appear to have been very short, termi- 

 nating at or above the foot of the range,within a mile or two 

 of the snowh'elds, instead of uniting and stretching far down 

 the Ammonoosuc, Connecticut, and other valleys, as earlier 

 investigators have held. The cutting of these cirques must 

 *In the Geology of New Hampshire, vol. iii, pp. 239-243, 1878. 



