


PARALLEL ROADS OF LOCHABER. 113 
IX. Dr Tyndall's Glacier Views. 
Dr TyNDALL’s main position is that “ Glen Spean was at one time filled by a 
great glacier. To the disciplined eye (he says) the aspect of the mountains is 
perfectly conclusive on this point ” (p. 10). 
How was Glen Spean so filled? He gives this answer,—“ It is not difficult 
to restore in idea the process by which the glaciers of Lochaber were 
produced, and the glens dammed by ice. The great collecting ground of the 
glaciers which dammed the glens, and produced the ‘Parallel Roads,’ 
were the mountains south and west of Glen Spean. When the cold of the 
glacial epoch began to invade the Scottish hills, the sun at the same time act- 
ing with sufficient power upon the tropical ocean, the vapours raised and 
drifted on those northern mountains were more and more converted into snow. 
This slid down the slopes, and from every valley, strath, and corry south of Glen 
Spean, glaciers were poured into that glen” (p. 11). | 
Here we are presented with what must be admitted to be a very remarkable 
theory. ‘The valleys, straths, and corries entering Glen Spean from the south 
were filled with zce; whilst the valleys on the north side of this same Glen 
were filled with water. Such a state of things implies an enormous differ- 
ence of temperature in these respective valleys, though all are in one dis- 
trict of inconsiderable area. Yet Dr TynDALL suggests nothing to show that 
such a difference of temperature between the two sides of Glen Spean must, 
or could have existed. The ice valleys are at about the same altititude above 
the sea as the Jake valleys, and within a few miles of one another. That surely 
is a difficulty which deserved explanation. It is true that on the south side of 
the Glen, there is, as Dr TYNDALL observes, Ben Nevis, which is higher than 
any of the hills on the north side of the Glen. But how Ben Nevis, because 
higher, should have produced the wonderful effects of filling the valleys on 
one side with ice and those on the other side with water, and keeping them in 
that exact state for hundreds of years, so as to give time for the Parallel Roads 
to be formed, it is very difficult to understand. 
And a more serious difficulty remains—Glen Spean is said to have been filled 
by a great glacier, which, crossing the mouth of Glen Roy, is supposed to have 
dammed the lakes in Glen Roy. But Glen Spean, at the very time that a lake 
filled Glen Roy, as previously shown, was itself occupied by a lake. One of the 
- Parallel Roads is visible on both sides of Glen Spean,—as Dr Tynpatu himself 
allows, and represents on his map of the district. For this reason, the very possi- 
bility of a glacier in it, at the time when the Glen Roy Lake existed, is excluded. 
And where did this supposed Glen Spean glacier come from? Dr TYNDALL 
says, “that glaciers were poured into it from every valley, strath, and corry, 
opening into that glen from the south.” No one who has examined the locality, 
VOL. XXVIII. PART I. 2F 
