GLACIATION OF THE SHETLAND ISLES. 799 
In the district which stretches from Weesdale westwards to Walls, 
and thence to Melby, the Boulder-clay sections furnish corroborative 
evidence of the north-westerly movement of the ice in that region. 
In the vales of Tingwall and Weesdale there is no trace of the 
altered Old-Red-Sandstone rocks which occupy the peninsular tract 
of country to the west. But as soon as the line of the great fault is 
crossed, which bounds these strata between Aith Ness and Selie 
Voe, abundant fragments of the gneissose rocks of Weesdale and 
adjoining tracts, as well as blocks of the porphyritic granite, are 
found in the Boulder-clay resting on the altered Old-Red rocks. 
Again, in the sections round the coast-line in the neighbourhood 
of Melby, the fragments in the subglacial deposit entirely consist of 
the underlying sandstones and the red quartzites and shales of 
Sandness Hill, along with some pink quartz-felsites ; but none of 
the purplish porphyrites which occur in Papa Stour are represented 
in these sections. Had the movement been from the north-west, 
then assuredly some fragments of the porphyrites would have been 
met with round Melby. Instead of this being the case, however, 
the Boulder-clay of Papa Stour contains numerous fragments of the 
altered Old-Red-Sandstone rocks from the Mainland. 
Another traverse across the island, from Gulberwick to West 
Quarff, reveals phenomena no less remarkable. On the slopes of the 
hills above Gulberwick, fragments of the red flags of Brenista and 
grits are met with; and they also occur in some patches of Boulder- 
clay near the head of the burn draining into the bay at Kast Quarff. 
On the west side of the watershed the Sandybanks burn is reached, 
which flows into Cliff Sound about a mile and a half to the north of 
West Quarff. In this hollow there is a deep covering of Boulder- 
clay, attaining a thickness near the farmhouse of 20 feet. Following 
this burn to its source, the deposit is found to consist of tough 
tenacious clay, with well-scratched stones, many of which consist of 
grit, red sandy flags, and shales of Old-Red-Sandstone age, associated 
with grey schists derived from the underlying rock. But further 
along the western seaboard, between the mouths of Sandybanks burn 
and West Quarff, similar phenomena are observable. Where this 
stream enters the sea, large blocks of the Lerwick sandstones and 
well-rounded conglomerates, measuring 2 feet across, were met 
with both in the Boulder-clay and on the surface. A hundred 
yards to the south of this locality fragments of the Brenista flags 
appeared, and became more numerous as we followed the coast-line 
southwards. Not far from West Quarff blocks of the basement 
breccia were met with, associated with fragments of the Brenista 
Flags and Rovey-Head conglomerates, in the thin coating of 
Boulder-clay on the slope and on the shore, 
We have already indicated the relative areas occupied by these 
subdivisions of the Old-Red-Sandstone rocks between Rovey Head 
and East Quarff, for the special purpose of showing the analogous 
distribution of the stones in the Boulder-clay on the western 
seaboard. ; 
On referring to the map it will be seen that the members of the 
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