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i§79-J 
PROCEEDINGS OF SOCIETIES. 
Royal Society, May i. — “ On the Origin of the Parallel Roads 
of Lochaber, and their bearing on other Phenomena of the 
Glacial Period,” by Joseph Prestwich, M.A., F.R.S., F.G.S., &c., 
Professor of Geology in the University of Oxford. Of the 
various hypotheses that have been brought forward since the 
time of Macculloch and Dick- Lauder to account for the origin 
of the parallel roads of Glen Roy, the one so ably propounded 
by Mr. Jamieson, in 1863, has been most generally received and 
adopted. It is a modification of the views originally expressed 
by Agassiz, to the effeCt that the barriers of the lakes — to the 
shore aCtion of which both the above named geologists attributed 
the “ roads,” but were at a loss to account both for the forma- 
tion and removal of barriers — had been formed during the Glacial 
period by glaciers issued from Glen Treig and Glen Arkaig, sup- 
plemented by others from Ben Nevis. The subsequent deter- 
mination, by the Scotch geologists, of an intermediate milder 
period succeeded by a second cold period, led Mr. Jamieson to 
conclude that the extension of these two glaciers took place 
during the second cold period, which he thinks was of little less 
intensity than the first, and that, while the glacier from Glen 
Arkaig blocked up Glen Gluoy, the glacier Irom Glen Teig 
formed a barrier to Glen Roy. This and other objections are 
considered by the author to be fatal to the hypothesis advanced 
by Mr. Jamieson ; but while objecting to this exposition of the 
Glacial theory, he considers that that theory affords the most 
satisfactory solution of the problem, only that he would suggest 
a different interpretation in explanation of the phenomena. 
Dismissing the hypothesis of local glaciers of the second period 
of glaciation, the author falls back upon the original idea of 
Agassiz with the development acquired by more recent research, 
and assigns the Lochaber lakes to the close of the first period 
of great glaciation. The general conclusions drawn by the 
author from the phenomena in Lochaber and surrounding dis- 
trict are — 
1st. That at the period of the first great glaciation of Scotland 
the ice-sheet in Lochaber attained a thickness of not less than 
2000 to 2500 feet, but that in consequence of the peculiar physio- 
graphical conditions of the district the large ice-currents from 
Ben Nevis so clashed with others in the Spean and Lochy Valleys 
that a block ensued which led to an exceptional heaping up and 
accumulation of the ice in front of Glen Roy and Glen Gluoy. 
