166 FRAGMENTS OF SCIENCE. 
pilgrimage to the place, and explored pretty thoroughly 
the roads of the principal glen. I traced the highest road 
to the col dividing Glen Roy from Glen Spey, and, thanks 
to the civility of an ordnance surveyor, I was enabled to 
inspect some of the roads with 4 theodolite, and to satisfy 
myself regarding the common level of the shelves at op- 
posite sides of the valley. As stated by Pennant, the 
width of the roads amounts sometimes to more than twenty 
yards; but near the head of Grlen Roy the highest road 
ceases to have any width, for it runs along the face of a 
rock, the effect of the lapping of the water on the more 
friable portions of the rock being perfectly distinct to this 
hour. My knowledge of the region was, however, far from 
complete, and nine years had dimmed the memory even of 
the portion which had been thoroughly examined. Hence 
my desire to see the roads once more before venturing to 
talk to you about them. The Easter holidays of 1876 were 
to be devoted to this purpose; but at the last moment a 
telegram from Roy Bridge informed me that the roads 
were snowed up. Finding books and memories poor sub- 
stitutes for the flavor of facts, I resolved subsequently 
to make another effort to see the roads. Accordingly last 
Thursday fortnight, after lecturing here, I packed up, 
and started (not this time alone) for the North. Next 
day at noon my wife and I found ourselves at Dalwhinnie, 
whence a drive of some five-and-thirty miles brought us 
to the excellent hostelry of Mr. Macintosh, at the mouth 
of Glen Roy. 
We might have found the hills covered with mist, 
which would have wholly defeated us; but Nature was 
good-natured, and we had two successful working days 
among the hills. Guided by the excellent ordnance map 
of the region, on the Saturday morning we went up the 
glen, and on reaching the stream called Allt Bhreac 
Achaidh faced the hills to the west. At the watershed be- 
tween Glen Roy and Glen Fintaig we bore northward, 
struck the ridge above Glen Gluoy, came in view of its 
road, which we persistently followed as long as it continued 
visible. It is a feature of all the roads that they vanish 
before reaching the cols over which fell the waters of the 
lakes which formed them. One reason doubtless is that 
at their upper ends the lakes were shallow, and incompe- 
tent on this account to raise wavelets of any strength to 
