Accamalatlon of DruiiiJrns. — I ^phoin . 349 
bor. For example, it is tinely developed in the clitt' forming the 
northeast end of Peddock's island, where live or six such bands 
are separated l)y intervals that vary from three to six feet; at the 
southwest end of Long island, where a single dark l)and about 
half way up the cliff, or 30 to 40 feet aljove the sea, extends 
fully 400 feet; and at the south end of Spectacle island, where 
two dark bands six or eight feet apart are distinctly seen along a 
distance of at least 150 feet at a similar elevation above the sea 
and below the top of the cliff' as on Long island. In all these 
sections, as in Third Cliff, the dark l)ands have anticlinal dips, 
which are somewhat more inclined thnn the overlying arched 
surface. 
Very rapid accumulation of ground moraine is shown b}' Fourth 
Cliff, for that drumlin, soon after the lieginning of its formation, 
received a wedge-shaped deposit of true subglacial till, increasing 
from nothing to six feet in thickness along its exposed extent of 
about 100 feet, laid down on the southern slope during a small 
part of the time, probably only one summer, if so long, in which 
the central portion of this hill was being formed by the subglacial 
deposition of 10 to 20 or 2") feet of stratified sand and gravel, 
which in their continiuition southward enclose the wedge of till. 
Under all this modified drift, the base of the section at its center 
is a low dome-shaped deposit of till, which, like the thick arch 
of till forming the upper and outer part of the drumlin, is 
divided from the modified drift by a well defined line with which 
the obscure lamination of the till and the bedding of the sand 
and gravel are parallel. No evidence of erosion, nor of tumul- 
tuous pushing forward, was anywhere seen ; but instead the whole 
section appears to represent continuous deposition. The very 
hard and compact condition of the till, and its characteristic 
flakiness, which T have spoken of as lamination, lioth l)olow and 
al)Ove the modified drift and in the enclosed Avedge, indicate that 
it was deposited as a ground moraine beneath the i)ressure of the 
ice-sheet, instead of as englacial till falling loosely from the ice 
Avhen it melted. The conditions leading to the accumulation of 
the basal till weri' followed ])y such as caused the modified drift to 
l)e spread over it, the latter api)!irently recpiiring no longer time 
than a single summer or the portion of the year attended by 
abundant ice-nu'lting; but on the southern sh)pe the de))osition of 
ihis sand antl gnivel was for a short time interrupted while the- 
