790 B. N. PEACH AND J. HORNE ON THE 
the agglomerate which now fills these necks, seems to support this 
view. 
Tid. Gractarton. 
From Sumburgh Head northwards to Hermaness in Unst, we find 
everywhere the clearest evidence that Shetland must have been at 
one time smothered in ice. The ice-worn islets along the shore- 
line, the polished and striated surfaces on the low grounds, the 
abraded and fluted appearance of the highest hills on the Mainland, 
alike point to the action of a thick mass of ice, which must have 
enveloped the isles. It is quite true that over considerable areas 
much of the evidence is obscured by a thick covering of peat; but 
wherever the peaty covering has been worn away, there are con- 
vincing proofs of that intense abrasion which we are accustomed to 
meet with in highly glaciated regions. 
Before describing the proofs of glaciation in the different islands, 
it may be well to state, as the result of our observations, that most 
of the roches moutonnées and striations indicate the movement of an 
ice-sheet across the islands from the North Sea to the Atlantic; but, 
in addition to this, there is satisfactory evidence for maintaining 
that, as the climatic conditions gradually ameliorated, the primary 
ice-movement gave place to that of local glaciers, which moved off 
the high grounds in the ordinary way, depositing their terminal and 
lateral moraines as they shrank back into the hills. 
Along the eastern seaboard of Unst the direction of the ice- 
markings varies from W. to W. 20°S. From Norwick to Harolds- 
wick numerous striz occur on the cliff-heads running W. to W.20°S., 
some of which were found on the top of a cliff 500 feet high; while 
in the southern parts of the island the average trend is W.30°S. In 
Fetlar the general direction of the striz along the northern coast, 
from Gruting Bay to the promontory of Urie, is W. 30°S., though 
they vary from W. to W.30°S. Two exceptions to the foregoing 
examples were found on the west side of the island—one on a gla- 
ciated surface of serpentine west of the promontory at Urie, running 
north and south, and the other on gneiss at the north-west corner 
of the island, pointing N.10° W. ‘These instances, however, have 
no connexion with the main set indicating the general glaciation of 
the island. 
Again, on the north-east coast of Yell the stric point W. 25°S., 
harmonizing with the direction of those found on the south side of 
the island of Unst; but on the western seaboard from Sandwick to 
the Noup of the Graveland the trend varies from W.30°-39° N. In 
spite of this variation we are convinced, from evidence obtained in 
the Mainland, that these instances belong equally to the period 
of primary glaciation. It would seem that the ice-sheet abutted on 
the eastern seaboard of Shetland with a 8.8.W. and 8.W. trend, and 
after reaching the crest of the Mainland it swung round to the 
N.N.W. and N.W. 
Along the north-west coast of Whalsey, between Skaw Taing and 
Symbister, the average direction of twenty-one instances is 8. 28° W., 
