256 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
contour, could under normal conditions, transport large boulders from 
the adjacent depths and lodge them, delicately poised, on the summit of 
the ridge. The explanation by floating ice would leave out of account 
the great rarity of trap boulders, though these should be the commonest, 
since, during submergence, the only shoals for many miles around 
whence floating ice might derive rock-fragments other than glacial 
erratics, would be underlain by the trap of the present hills. Still less 
would the sudden cessation of this sort of deposition at the 265-foot 
level as the land arose, be explained. Finally, both hypotheses suffer 
from the diffivulty that boulders, perched on the ridge-summit as we now 
see them, could not be left im setu if the rate of uplift were anything 
else than catastrophic. A single heavy storm from the southward would 
doubtless suffice to sweep all loose material from their precarious posi- 
tion. The conclusion that the boulder-covered zone has never been 
submerged since the general ice-sheet retreated from the country, can- 
not be escaped. On the other hand, the boulderless zone is a wave- 
swept zone. 
Other evidences for former submergence of the lower zone are clear 
and gonvincing. The smooth, unbroken surfaces of the roehes mouton- 
nées above 265 feet contrast strongly with the jagged and riven ledges 
below that level. At the upper limit of the boulderless zone, low, but 
steep and rugged cliffs look northward over frequent pockets and 
graded slopes of well-rounded pebbles. Similar deposits were observed 
at 145, 155, and 175 feet, while an unusually fine boulder-beach fifty 
yards long and twenty in width occurs at 205 feet. The boulders, 
averaging six inches in diameter, are not covered with vegetation, and 
bear remarkable resemblance to the raised beaches of Hogland in the 
Gulf of Finland. Such beaches are rare on both Ice Tickle Island and 
on Rodney Mundy Island. That they were here not discovered more 
plentifully is due to the general steepness of the ridges and the conse- 
quent lack of places of lodgment for loose material; to the hardness of 
the rocks hereabouts, coupled with the shortness of the time allowed for 
beach-building; aud to the abundance of moss and other peat-formers 
that develop thick vegetable mantles over most graded slopes. An indi- 
cation of the great variety of form assumed by elevated sea-chasms, 
benches, and boulder-deposits in the wave-swept zone at other localities, 
will appear in the following pages. 
Occasionally it was found that single boulders in exposed situations 
occurred below the accepted level of the highest shore-line. These were 
either too large to be moved by the waves, or had rolled down from the 
