DALY: GEOLOGY OF THE NORTHEAST COAST OF LABRADOR. 255 
headlands and hills where the surf from the open ocean can be felt on a 
glaciated shore during submergence, the present lower limit of undis- 
turbed glacial erratics marks with but subordinate error the highest 
shore-line of postglacial submergence. 
For the first time during the cruise, conclusive evidence of the value 
of the criterion on the Labrador shore was obtained at Ice Tickle Harbor. 
It is of importance to review the conditions under which it was there 
employed. These conditions are essentially the same as those found at 
the numerous other stations occupied up and down the coast. 
The situation, topography, and bed-rock geology of the islands on 
either side of the tickle have already been described (p. 213). The dark- 
hued trap-ridges are dotted over with light gray gneissic boulders offering 
strong contrast in color and composition with the ledges beneath. These 
boulders are subangular, not water-worn, often greatly decomposed, and 
have evidently lain long in their present positions. They are associated 
with a small proportion of boulder-clay which is, in places, actively 
creeping down the slopes. Occasionally the boulders are perched and 
may be easily rocked with the hand. All these boulder-covered ridges 
are over 265 feet high. Those of less height are devoid of boulders ; 
those of greater height may be divided into a boulder-covered and a 
boulderless zone separated from each other by the 265-foot contour. 
(Plate 8.) — 
That the boulders are truly glacial erratics, reposing practically where 
the great Labrador ice-sheet left them, can hardly be doubted. The 
only alternative origins which have suggested themselves are two in 
number. Lither the boulders, originally deposited elsewhere by the 
land-ice, were thrown up by strong storm-waves, or they were brought 
thither by floe- or shore-ice. In spite of the unlikelihood of these 
hypotheses, it was held that evidence should be obtained that would 
thoronghly test them. The long ridge on the southern shore of Ice 
Tickle Island threw ample light on the question, and serves as an 
extremely good type locality for demonstrating the criterion. 
This ridge, over a mile in length, and generally about three hundred 
feet in height (325 feet, measured barometrically at the highest point) 
is a residual hill situated where a thick trap dike projects above the 
softer gneisses. Its axial trend is roughly east and west. Its sides are 
very steep, running together at a sharp edge, whence one looks directly 
out over Hamilton Inlet on the south and over a deep valley and beyond 
over the open sea north of the island. There seemed to be no possibility 
that waves breaking on the ridge, submerged to the 300-foot, or any higher 
