131 
[Upham. 
parallelism with the surface, having thus in the drumlins an incli- 
nation like that of their slopes. This structure is best displayed 
after some exposure of the section to the action of the weather. 
It seems to be an imperfect cleavage resulting from the enormous 
pressure of the overlying ice, and also indicates that the accumu- 
lation of the drumlins took place by gradual addition of till ,over 
their surface. Only a thin layer of englacial till, with its numerous 
large boulders, contained within the ice-sheet and allowed to fall 
loosely from it during its final melting, is observable upon these 
drumlins, its probable thickness in this vicinity being not usually 
more than one or two feet. 
Plentiful fragments of shells, up to one or two inches in length 
and rarely of larger size, are embedded, like the small fragments 
of rock, in the dark lower portion of the till. They were found most 
abundant in Grover’s cliff, Great Head, Peddock’s island, and the 
northern cliff of Hull, one or several shell fragments being usually 
seen on each square yard of the exposed surface, so that hundreds 
may be gathered in an hour. In all the localities a single species, 
the round clam or quohog, Venus mercenaria , L., makes up proba- 
bly ninety-nine per cent of the Specimens found ; but no entire valve 
of this shell was obtained among the thousands of its fragments. 
The species next in numbers is Cyclocardia borealis , Conrad, which, 
like the foregoing, is thicker and stronger than most species and 
therefore better fitted to resist the grinding action of the ice. The 
smaller size of the latter has enabled some of its specimens to es- 
cape almost unbroken and with only slight abrasion of its margin. 
In no instance, however, have the two valves of this or any other 
species been found united. Some of the fragments show little wear- 
ing or none, their broken edges being sharp and the markings of 
their surface perfectly preserved ; but the majority are considera- 
bly worn, and pieces perforated by burrows, like the dead shells 
cast up on a beach, are frequently found. No glacial striation has 
been detected on any of these shell fragments, and indeed it is 
rarely observable on pieces of stone of so small size. 
The cliff at the northeast end of Peddock’s island, though not 
showing more of the large fragments than the other localities spe- 
cially mentioned for their abundance, yet far surpasses these in its 
multitude of very small fragments and even minute particles of 
shells, from a quarter and an eighth of an inch in length down to 
