D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 645 
had formed an angle or projecting point when the lake existed. The old beach, 
viz., Shelf 4, goes round the rock. 
JAMIESON, in like manner as Professor NIcoL, maintains that whilst the 
“drift beds” repose on the scored and polished rocks, the rocks were scored 
and polished while the land was covered with ice, the drift beds being deposited 
during the subsequent submergence of the land. (Vol. xviii, p.164.) 
The question is, whether the ice-sheet alone could have polished and scored 
the rocks in the peculiar positions in which they are sometimes found. Had 
these smoothed and scored rocks been generally on the tops or ridges of hills, 
there would have been less difficulty in ascribing these effects to a general ice- 
sheet. But instead of being in these exposed positions, the smoothed and 
striated rocks are most frequently in valleys :—and the narrower the valley, the 



~s 
wn SPRAY 
“SESSA 

Fig. 17. 
1. Gneiss Boulder, 8 feet high, 48 feet round, on Shelf 4, above Inverlair House ; shelf here 
about 60 feet wide. 2. A rock smoothed by some agent. 38. Gravel stratified, on which the shelf 
was formed, forming a steep scaur about 50 feet high. 
more remarkable is the smoothing and polishing. This is undoubtedly the case 
in Glen Spean, at its narrowest parts between the Roman Catholic Chapel and 
Inverlair. 
It appears also that the heavy body which effected the striations was, when 
obstructed in its passage by a solid rock, capable of rising over it. 
Now what would happen, when a body of land ice was so obstructed? Ifthe 
rock did not break, the under part of the ice would probably be arrested, and 
the upper part would, under the influence of the propelling force, move on. 
On the other hand, in the case of a body of ice floating, the buoyancy 
of the ice, when obstructed, would enable it to rise up and over the obstruction. 
