SUPPLEMENTAKY KEMAEKS ON GLEIT EOY. 7 



the Great Glen of the Caledonian Canal where Ben N'evis is situated. 

 Here then would be the heaviest falls of snow, and as snow is the 

 mother of glaciers here also would be the heaviest ice. Accordingly, 

 we find ample evidence that all along the West coast from Argyll 

 to Cape Wrath the accumulation was enormous. A line drawn 

 from Een ISTevis past the Moor of Eannoch to the head of Loch 

 Lomond marks the centre of what seems to have been the greatest 

 ice-field in Scotland. Another line drawn from the top of Glen 

 Arkaig northward to Loch Shin indicates the middle of the ice- 

 field which was probably next in importance. The outward move- 

 ment of the ice, as deduced from the glaciation of the rocks and 

 transport of boulders, seems to have proceeded from these two 

 lines ; we may therefore conclude with considerable confidence 

 that the greatest precipitation of snow took place there, and it is 

 interesting to note that this coincides very well with what is now 

 the region of greatest rain. Seeing that these two ice-fields met 

 and coalesced at the western entrance of the Caledonian Canal, it 

 is evident there must have been a great congestion in that quarter, 

 for here was a narrow passage with heavy streams of ice coming 

 into it from the glens on both sides all the way down to the head 

 of Loch Linnhe. The quantity of ice that filled the Great Glen 

 and the mouth of Glen Spean was so gr-eat that it eventually over- 

 flowed the passes leading eastward into the valleys of the Nairn 

 and the Spey, notwithstanding that many of these passes are 

 actually higher than those to the westward which lead out to the 

 Atlantic. This western ice broke over Strath Errick in great 

 force ; it filled Glen Gluoy and flowed out at the top of it ; it like- 

 wise occupied Glen Eoy, and went out to the eastward over the 

 pass at the head of that glen. It also did the same at Makoul 

 in Glen Spean, so that before the era of the lakes the western ice 

 discharged itself over the very same cols over which the water 

 flowed at an after period. Some evidence of this was given in my 

 paper on the glaciation of Scotland, to which I would here refer. 



It is necessary to have a clear perception of this important 

 feature in the glaciation of Scotland, namely the much deeper 

 accumulation of ice on the West, otherwise it is quite impossible 

 to understand many of the results to which it gave rise. For 

 example, it has often been asked, with some degree of perplexity, 

 how it could be that Glen Roy and other glens to the eastward 

 were empty of ice while glaciers of such magnitude occupied Glen 

 Treig and the valley of the Caledonian Canal. " Is it likely," asks 

 Mr. Milne-Home, " that in this Lochaber district some glens should 

 have been filled with solid ice and others with water ? " " Why," 

 says Prestwich, " should the Arkaig hills have their huge glacier 

 and the neighbouring range north of the Spean, at the same time, 

 none?"' 



Looking merely at the comparative height of the hills, these 

 objections seem perfectly reasonable, but the paradox is solved 

 when we consider the comparative rainfall and reflect what would 

 1 Phil. Trans. Eoy. Soc. for 1879, vol. clxx. p. 676. 



