I have no doubt that when Mr. Campbell visited Labrador he expected to
find the sea-coast under the water-line striated by means of icebergs,
and was probably not a little surprised to find that it actually was
not. And I have no doubt that were the sea-bottom in the tracks of the
large icebergs elevated into view, he would find to his surprise that
it was free from striations also.
So far as observation is concerned, we have no grounds from what Mr.
Campbell witnessed to conclude that icebergs striate the sea-bottom.
The testimony of Dr. Sutherland, who has had opportunities of seeing
the effects of icebergs in arctic regions, leads us to the same
conclusion. “Except,” he says, “from the evidence afforded by plants
and animals at the bottom, we have _no means whatever_ to ascertain
the effect produced by icebergs upon the rocks.[142] In the Malegat
and Waigat I have seen whole clusters of these floating islands,
drawing from 100 to 250 fathoms, moving to and fro with every return
and recession of the tides. I looked very earnestly for grooves and
scratches left by icebergs and glaciers in the rocks, but always failed
to discover any.”[143]
We shall now see whether river-ice actually produces striations or not.
If floating ice under any form can striate rocks, one would expect that
it ought to be done by river-ice, seeing that such ice is obliged to
follow one narrow definite track.
St. John’s River, New Brunswick:—“This river,” says Mr. Campbell,
“is obstructed by ice during five months of the year. When the ice
goes, there is wild work on the bank. Arrived at St. John, drove
to the suspension-bridge.... At this spot, if _anywhere in the
world_, river-ice ought to produce striation. The whole drainage of
a wide basin and one of the strongest tides in the world, here work
continually in one rock-groove; and in winter this water-power is armed
with heavy ice. _There are no striæ_ about the water-line.”[144]
River St. Lawrence:—“In winter the power of ice-floats driven by
water-power is tremendous. The river freezes and packs ice till the
flow of water is obstructed. The rock-pass at Quebec is like the
Narrows at St. John’s, Newfoundland. The whole pass, about a mile
wide, was paved with great broken slabs and round boulders of worn ice
as big as small shacks, piled and tossed, and heaped and scattered
upon the level water below and frozen solid.... This kind of ice does
NOT _produce striation_ at the water-margin at Quebec. At Montreal,
when the river ‘goes,’ the ice goes with it with a vengeance.... The
_piers are not yet striated_ by river-ice at Montreal.... The rocks
at the high-water level have _no trace_ of glacial striæ.... The rock
at Ottawa is rubbed by river-ice every spring, and _always in one
direction, but it is not striated_.... The surfaces are all rubbed
smooth, and the edges of broken beds are rounded where exposed to the
ice; _but there are no striæ_.”[145]
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