108 Mb. Betce 0}i ilie Parallel Roads ofLochaber. 



shelf; that, on the final retiring of the glacier, this old moraine served as 

 a barrier to dam up the water to the level of the lower shelf, and that it 

 has been subsequently washed away by the river flowing over it." He 

 then suggests that the space between the terminations of the upper and 

 lower shelves should be examined, to ascertain if the remains of such a 

 moraine exist. I made this examination with considerable care, but 

 could find no such remnants. There is some detritus in the main glen 

 opposite the mouth of Glen Fintec ; but it has obvious reference to the 

 present drainage, and is in no way remarkable. The whole of Glen 

 Gluoy is indeed singularly free from detritus ; — a peculiarity which I con- 

 sider due to its form. It is narrow, and the hiUs rise steep and high from 

 the very margin of the river, so that there is no space where detritus 

 could rest; and it is thus swept away as soon as it is brought down. 

 This circumstance is also favourable to the rapid and complete removal 

 of such a moraine, or barrier, as Mr. Thomson supposes may have once 

 existed. The mouth of the glen is equally free from detritus, or other 

 indications of the existence of earthy barriers in a former condition of 

 things. 



" A glacier occupying the present site of Loch Lochy, and receiving 

 supplies from the neighbouring mountains, would appear," JVIr. Thomson 

 says, " to afibrd a sufficient explanation of the phenomena observed in 

 this glen." This was no doubt written under the impression that Glen 

 Fintec communicated with Loch Lochy, and that the mouth of Glen 

 Gluoy was in the way of a glacier advancing from that lake. But this is 

 not the case. A glacier having its origin among the high mountains to 

 the N.W. of Loch Lochy — the only hiUs high enough to produce one — 

 and advandng from Loch Lochy, must make its way past Maucomer and 

 Brecklech up the valley of the Spean, for so only will the levels permit. 

 This direction is about perpendicular to that of Glen Gluoy ; and it would 

 be only a lateral branch or arm, parting from the main body, that could 

 penetrate that glen. The mouth of the glen is narrow, and the hill sides 

 rise steep and high ; a little way up there is a considerable bend before 

 we reach, at a mile's distance, the bosom or sinus in the hill side, where 

 the moraine is conceived to have existed in connexion with the lower 

 shelf. All this shows the improbability of a moraine being deposited at 

 this place by such a glacier ; and that recourse may as well be had to the 

 masses of ice with which Glen Spean has been supposed to be filled, from 

 its chief source in the Ben Nevis group. But it seems impossible that 

 such masses of ice could deposit a moraine in the situation requu-ed ; and 

 it even appears doubtftd whether sheets of ice would deposit moraines at 

 all. On these grounds I do not see how we can admit Mr. Thomson's 

 theory in its present form, 



VI. — CoKCLUSION. 



I do not feel myself competent to express a decided opinion upon this 

 " vexed question ;" but regarding the lake theory as the true one, I think 



