524 ON THE GEOLOGY OF THE ISLAND OF AQUIDNECK. 
ment which suggest themselves ; none of them, however, seem quite . 
to satisfy the facts. The most natural conjecture seems to be that 
the irregularity was made at the time of deposition of the materi- 
al. Had it taken this shape afterwards the only possible suppo- 
sition would be that marine currents had produced the excavation — 
during a period of depression. This, however, is distinctly negi- 
tived by the fact that the coarse as well as the fine material has 
disappeared, there being no such mass of boulders on the bottom 
of the depression as would exist on this supposition; moreover, — 
it is really impossible to account for the existence of such 
great eddies in the positions where these great excavations — 
occur, at points remote from large obstacles such as could set great 
tidal currents whirling. Limiting ourselves to the conditions : 
which could cause irregularities in the deposition of the drift, we 
still find the matter beset with difficulties. In the first place, itis > 
difficult to see what could have ċaused such lacunes in the diate . 
bution of drift matter, within or on the surface of a glaci ; : 
The most satisfactory explanation seems to be that the greater 
part of the drift which lies here was borne on the surface of the 
glacier and that these openings in the moraine matter answer 
gaps in the ice on the surface of the glacier, caused perhaps by 
action of streams such as are often seen to originate on the oe 
of a glacier and then to find their way in straight shafts . 
base. Such cavities would remain even after they becam pe 
or disused, being covered with drift or quite bare, and at ae 
of melting their place would be marked by just such va l 
these. A fe 
Other depressions exist on a larger scale at the points ae 
by the several ponds of the island ; none of these ponds seem x 
complete rock basins all having, or having had, deep channels ¢ 
necting them with the sea. Blue Bill Cove seems ote 
formed by the drift masses which surround it, oxee Te 
syenite rock makes a part of its northeast border. oob 
Pond, near Newport, is the next depression to the aed 
We have one of the valleys of the island cut down by i 
stream until its mouth lay beneath the level of the 
the ice disappeared the valley constituted a fiord-like i 
action of the sea seems to have made two successive. Ta 
‘the valley, one about one-half the distance from p per 
to the head of the pond, the other forming the Pr? 
1E 
