804 B. N. PEACH AND J. HORNE ON THE 
roches moutonnées, or on the drift-slopes, all of which were distri- 
buted by the later glaciers. 
Again, boulders of the Northmavine diorite are scattered over the 
low ground between Hillswick and the Grind of the Navir, while 
blocks of metamorphic rocks were carried by the great mer de glace 
and the later glaciers from the Leas of Deal and the surrounding 
heights onto the diorite area of Busta Voe. ‘The peculiar band of 
nodular gneiss on the promontory of Lunna has supplied boulders 
which can be followed westwards towards the head of Swining Voe, 
and the ridge overlooking Dourye Voe, in harmony with the pri- 
mary ice-movement. 
West of Weesdale, blocks of the porphyritic granite in Bixetter 
Voe, as well as boulders of gneissose rocks from the Weesdale hills, 
are strewn over the area occupied by the altered Old-Red-Sandstone 
rocks; while boulders of the Sandness-hill quartzites have been 
borne seawards to Melby. 
Perhaps the most interesting series of erratics occurs on the ridge 
of high ground which extends from Scalloway to the Wart of 
Skewsburgh, where small blocks of the Brenista Flags and the Ler- 
wick Sandstones, varying from a few inches to a foot across, are 
exposed in places where the peat has been worn away. ‘These have 
been carried from lower to higher levels ; indeed they have been 
carried to the tops of the highest hills along this tract. We have 
already incidentally referred to this remarkable fact, and to the 
occurrence of similar blocks in the Boulder-clay on the west coast, 
and as erratics on the slopes of the hills. Those which are found 
on the western sea-board are much larger than those on the hill- 
tops, as they sometimes measure 3 feet across ; many of them still 
show ice-markings. We believe that their occurrence in the drifts 
on the west coast and as erratics on the hill-tops is due to the same 
cause, viz. to the westerly movement of the great mer de glace, which 
was powerful enough to override the watershed. 
VII. Fresawater Locus anp Vors. 
The freshwater lochs abound chiefly in the Mainland; and in 
certain districts they occur in great numbers. They are due either 
to the irregular deposition of the Boulder-clay or moraine-matter, to 
hollows in the peat, or to rock-basins which have been eroded by the 
ice. Indeed they are so abundant in some of the rocky districts 
as to recall portions of the north-west of Sutherlandshire. At 
present we are only concerned with those which occupy rock-bound 
hollows, and which are the result of glacial erosion. 
These occur most abundantly on the rocky plateau of Roeness, in 
the diorite-area of Northmayine, on the rocky headlands north and 
south of Vidlon Voe, and in the district of Walls. In each of these 
localities the sheets of water, with certain exceptions, fill eroded 
hollows in the rocks; and, from the manner in which their rocky 
margins are grooved and polished, from the freshness of the roches 
moutonnées which encircle them, there can be little doubt they haye 
been eroded by the ice during the general glaciation. From one of 
