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V.—Additional Memoir on the Parallel Roads of Lochaber. By Davip 
Mine Home, LL.D. (Plates XIII, XIV.) 
(Read 29th January 1877). 
Towards the end of last winter session, a Memoir by me, on the “ Parallel 
Roads of Lochaber,” was read to this Society, and it has since been pub- 
lished in our Transactions. The subject was far from being exhausted. 
Nevertheless, I had no intention of continuing the inquiry, venturing to 
think, that enough had been adduced by me to support the conclusions at 
which I had arrived. But during the course of last summer, Dr TynpDALL of 
London visited Lochaber. He went for the special purpose of studying the 
“Roads,” and of enabling him to give a public lecture regarding them in the 
Royal Institution, Albemarle Street, on 9th June. 
In the course of his lecture, Dr TynDALL alluded to my recent Memoir, and 
also to researches described in a previous Memoir. But he dissented from 
my solution of the problem, and told his hearers (I quote his words) that 
they might “with safety dismiss it (the detrital barrier theory) as incompetent 
to account for the phenomena. The theory which ascribes the Parallel Roads 
to lakes dammed by barriers of ice, has, in my opinion, an amount of probability 
on its side, which amounts to a practical demonstration of its truth.” 
These views having been rested on observations made in the district by Dr 
TYNDALL himself, I felt that it was only due to a person of his scientific reputation, 
to reconsider my own opinions, and to weigh well his reasons for coming to a 
different conclusion. 
Accordingly, with Dr TyNDALL’s printed lecture in my hand, I revisited 
Lochaber during last autumn, and I now propose to state the results of my 
farther researches. : 
I reserve for the close of this Memoir, a more special notice of Dr Ty NDALL’s 
lecture. 
Before describing my most recent researches on the Glen Roy problem, let 
me very briefly notice the heads of the theory which I suggested as a solution 
of it in my last Memoir. 
1st, I adduced cases of lakes in the Highlands, and some in the Lochaber 
district, now kept up in the valleys by blockages of detritus, and at levels 
above the sea, quite as high as the lakes which formerly filled the valleys of 
Gluoy, Roy, and Spean. In each of these cases, there were beach-marks on 
VOL. XXVIII. PART I, Dee 
