Ben Nevis. — Upham. 379 
ice-sheet withdrew until its last stronghold, probably the latest 
in Britain, was this highest mountain of Scotland. 
The difficulty of supposing valley glaciers of later origin 
to have obstructed the Great Glen and Glens Spean and Roy 
is well stated by Jamieson, showing rightly, as I think, that 
the Parallel Roads are a record of the end of the general gla- 
ciation of Scotland, rather than of a later stage or epoch of 
renewed ice accumulation. Similar difficulties seem to me to 
oppose the view of Prof. J. B. Tyrrell, who has supposed an 
ice-sheet first amassed on the Cordilleran area of North Amer- 
ica, then waning,. and succeeded by a chiefly later ice-sheet on 
the Keewatin region of the interior of this continent, which 
in its turn decreased, to be followed in time by the cb.ief ac- 
cumulation of a Laurentide or Labradorean ice-sheet.* On 
the other hand, my interpretation of our glacial striie and drift 
transportation, with frequent changes of the glacial boundar- 
ies and overlapping of the drift deposits, refers the glaciation 
of these three great regions of North America, like that of the 
British Isles and continental Europe, to the same time, with 
confluence during the greater part of the Glacial -period, and 
with later division into separate icefields, corresponding to the 
great areas of glacial radiation, when the previously united 
and continuous North American ice-sheet melted away. 
In connection with the moraines of Glen Roy and the 
lower part of the Spean valley, brief mention ought to be made 
of the three very admirably developed moraines which ex- 
tend eastward from the east end of the Creag Dhubh mount- 
ain mass south of the Glen Glaster col. These moraines, 
formed during the Glaster stage of lake Roy, reach four miles 
or more, athwart the Spean valley six to eight miles east of the 
mouth of Glen Roy. The more southern and western of the 
three moraines curves in a semicircle across the rather level 
moor east of TuUoch station, and its northern part runs along 
the northern foot-slope of the great mountain east of loch 
Treig, there being represented by three or four district mor- 
ainal lines on the steep rock slope. 
Another paper, for which I took plentiful notes, might be 
written on the very interesting kames and kame plateaus 
which are admirably displayed along an extent of nearly two 
*Journal of Geology, IV, 811-815, Oct.-Nov., i8q6; VI, 147-160, with 
maps, Feb. -March, 1898. 
