GLACIATION OF THE SHETLAND ISLES. 793 
tract between Dourye and Vidlon Voes; and the same features are 
apparent on the rocky promontory north of the latter sea-loch. 
Indeed, so perfect and so abundant are the roches moutonnées that 
it may be correctly described as by far the finest district on the 
Mainland for studying the effects of the primary glaciation. 
The average trend of the ice-markings in the districts now 
referred to is W.35°S., though they vary from W. to 8.W. The 
position of the roches moutonnées leaves no room for doubt as to the 
direction of the ice-movement. In Swining Voe, which lies to the 
west of Vidlon Voe, there is a gentle Boulder-clay slope on 
the east bank, and a steep rock-face on the west bank, rising to a 
height of from 400 to 500 feet. Notwithstanding this steep slope, 
the whole rock-face is splendidly glaciated ; and, strange to say, the 
striz do not run parallel with the coast-line but obliquely across it, 
the direction being nearly south-west. In one remarkable instance, 
about halfway down the voe, on a glaciated surface, which slopes 
downwards into the sea-loch at an angle of 65°, striz were observed 
which could be traced from the water-level up the rock-face at an 
angle of 25° with the surface-plane of the sea-loch. We shall point 
out presently how the dispersal of the stones in the Boulder-clay 
completely substantiates this south-westerly movement of the ice. 
The tract of country which stretches from Weesdale westwards 
to Melby and Walls presents the same glaciated aspect, though in 
many places the roches moutonnées have been much broken up by 
atmospheric waste. Nevertheless the rounded outline of the hills 
testifies to the moulding of the whole tract by ice, while the striz 
have a marked north-westerly trend, quite in keeping with the 
northing already referred to on the western shores of Northmavine. 
Not only so, but the highest ground in the centre of the Mainland 
is likewise ground down and striated. The ridge which extends 
from Weesdale hill (842 feet) to Scallafield (916 feet) reveals the 
finer lines as well as the flutings of the ice-chisel wherever the peat 
is worn away, the direction varying from W. 28°-40° N. Near the 
gap in the ridge overlooking the head of Weesdale Voe, the polished 
surfaces and striations are as fresh as if the ice had but recently 
passed away. Further, the same north-westerly trend is met with 
on the banks of Olna Voe, east of Meikle Rooe, and in the numerous 
sea-lochs opposite the isles of Papa Little and Vementry. 
In the districts of Lerwick and Quarff, on the eastern seaboard, 
there is conclusive evidence of the existence of two systems of ice- 
markings, the one set belonging to the general glaciation trending in 
a south-westerly direction, and the other set belonging to a later 
period, indicating a movement in asouth-easterly direction, produced 
by local glaciers. Indeed, so severe must have been the later gla- 
ciation in the neighbourhood of Lerwick, that most of the instances 
belonging to the primary system were well-nigh effaced by it. Both 
the abundance and the freshness of the strive belonging to the later 
system plainly indicate the power of the local glaciers in this neigh- 
bourhood; but we shall see presently that at no time were they 
large enough to override the island of Bressay. Several interesting 
