158 
FRAGMENTS OF SCIENCE. 
reached a col, or watershed, looking into Glen Spey, and 
of precisely the same elevation as the highest road of 
Glen Roy. 
He then dropped down to the lowest of these roads, and 
. " followed it toward the mouth of the glen. Its elevation 
above the bottom of the valley gradually increased; not be- 
cause the shelf rose, but because it remained level while 
the valley sloped downward. He found this lowest road 
doubling round the hills at the mouth of Glen Roy, and 
PARALLEL ROADS OF GLEN ROY. 
After a Sketch by SIR THOMAS DICK-LAUDER. 
running along the sides of the mountains which flank 
Glen Spean. He followed it eastward. The bottom of 
the Spean Valley, like the others, gradually rose, and 
therefore gradually approached the road on the adjacent 
mountain-side. He came to Loch Laggan, the surface of 
which rose almost to the level of the 'road, and beyond the 
head of this lake he found, as in the other two cases, a 
col, or watershed, at Makul, of exactly the same level as 
the single road in Glen Spean, which, it will be remembered, 
is a continuation of the lowest road in Glen Roy. 
