676 
PROFESSOR PRESTWICH ON THE ORIGIN 
of Cronach Beag 4,060 feet high, there is no very material difference in the altitude 
of the hills north and south of Glen Spean. The other mountains of the Ben Nevis 
range on the south side of the Spean Valley are respectively 3547, 3217, 3658, 3433, 
3569, and 3443 feet in height ; while the range on the opposite north side of the Spean 
Valley, including the Glen Roy area, measure 2736, 3422, 3700, 3441, and 3298 feet. 
Those again which encircle Loch Arkaig are on the north side 2398, 2636, 1802, and 
2680 feet; and on the south side 2613, 2373, 3224, and 3164 feet in height, or of less 
elevation than those between Glen Roy and Loch LagganA 
Surely under such nearly similar conditions, “is it,” as Mr. Milne Home observes, 
“ likely that in this Lochaber district some glens should have been filled with solid ice 
and others with water ? ” Why should the Arkaig hills have their huge glacier, and 
the neighbouring range north of the Spean, at the same time, none % 
For the reasons assigned to have any force, it should be shown that in the district 
still further east, where the rainfall is under 50 or even under 40 inches, and there are 
mountains of the equal height, there was, at the same period, a similar absence of 
glaciers; but the observations of Mr. Jamieson himself in Aberdeenshire, as well as 
those elsewhere of other Scotch geologists, show that during the second glacial period 
there were local glaciers amongst hills of the same height as those of Glen Roy, and 
where the rainfall is no greater, but even less than in that district. Chambers, 
speaking of the local systems of the later or second period of glaciation, remarks that, 
“ wherever there are mountains in Scotland approaching or exceeding 3,000 feet 
in height, there have glaciers existed,” and mentions many in the valley of the Dee,f 
where according to Symonds’s hyetographical map the annual rainfall is only between 
30 and 40 inches.:[ 
Although the presence of the Merjelen See, at a height of 7,700 feet, shows how an 
open lake may co-exist by the side of a large glacier, the conditions are entirely different 
to those which obtained in Lochaber. This small lake is some 1,200 to 1,500 feet 
below the snow-line, but the Aletsch glacier, by which it is dammed up, has its origin 
in mountains from 12,000 to 14,000 feet high, and both lake and glacier belong to the 
same mountain range. The lakes of similar character in the Himalayas are also con¬ 
siderably below the level of the snow-line, and are fed by small tributaries, whereas 
most of the feeders of the Lochaber lakes, being in main valleys, have their rise among 
the higher summits at heights which must have been above the snow-line, and should 
have furnished glaciers rather than streams of water. Either the snow-line, if higher, 
* An ordnance map of Mr. J. E. Campbell’s, in which he has coloured the surfaces above the 3,000 
feet contour line, shows that the area above that level on the north of the Spean valley is very little 
less than that on the south. 
f Edin. New Phil. Joum., vol. liv., p. 254, 1853. 
+ The great ice-sheet of Greenland seems to be maintained without any heavy- rainfall. Dr. Rise 
(‘ Danish Greenland,’ 1877, p. 377) found the annual fall of snow and rain at Julianehaab, in South Green¬ 
land, during his few years’ residence, to average 37 inches, and says that the fall of snow in North is less 
than in South Greenland; but the gauges yet are few, and nothing is known of the fall on the east coast. 
