I spent some time cruising up and down the Sound of Harris, and found
that all the islets there had been ground and scraped by ice flowing
in the normal north-west direction, and sub-glacial débris occurs on
at least one of the little islands--Harmetrey. But all the phenomena
of glaciation are met with in most abundance in the dreary island of
North Uist. The ridge of mountains that guards its east coast has been
battered, and ground down, and scraped bare in the most wonderful
manner, while the melancholy moorlands are everywhere sprinkled with
till, full of glaciated stones, many of which have travelled west
from the coast range. Benbecula shows in like manner a considerable
sprinkling of till, and the trend of the glacial striæ is the same
there as in North Uist, namely, a little north of west. There are no
hills of any consequence in Benbecula, but the highly-abraded and
barren-looking mountains that fringe the eastern margin of North Uist
are continued south in the islands of Roney and Fuiey, either of which
it would be hard to surpass as examples of the prodigious effect of
land-ice in scouring, scraping, and grinding the surface over which it
moves.
South Uist presents the same general configuration as North Uist,
its east coast being formed of a long range of intensely glaciated
mountains, in the rear of which ragged sheets and heaps of sub-glacial
débris are thrown and scattered over the low, undulating tract that
borders the Atlantic. No part of either Benbecula or North Uist has
escaped the action of ice, but in South Uist that knot of high-ground
which is dominated by the fine mountains of Beinn Mhor and Hecla
towered above the level of the glacier-mass, and have thus been the
cause of considerable deflection of the ice-flow. The ice-stream
divided, as it were, part flowing round the north flank of Hecla,
and part streaming past the southern slopes of Beinn Mhor. But the
ice-flow thus divided speedily reunited in the rear of the mountains,
the southern stream creeping in from the south-east, and the northern
stream stealing round Hecla towards the south-west. The track of this
remarkable deflection and reunion is clearly marked out by numerous
striæ all over the low-grounds that slope outwards to the Atlantic
coast. The till, it need hardly be added, affords the same kind of
evidence as the sub-glacial deposits of the other islands, and points
unmistakably to a general ice-movement across South Uist from the Minch
to the Atlantic.
Public-domain text, read in full here on John Shaqi.
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