292 - Proceedings of Metropolitan Societies. | April, 
subject, appears scarcely assailable by arguments drawn from strati- 
graphical details, but must be decided by means of the fossils. 
- 4. The next paper especially worthy of notice, is that by Mr. 
Jamieson, on the “Origin of the Parallel Roads of Glen Roy,” a ques- 
tion which, as everybody knows, has hitherto bafiled, more or less, 
every attempt at its solution. 
The view advocated by Mr. Jamieson was suggestively propounded 
by Agassiz many years ago, but has been until now almost ignored. 
According to this theory, the “parallel roads,” or terraces, are the 
beaches of glacier-lakes; and Mr. Jamieson finds that it is the only 
one which will account for all the facts, and which is not inconsistent 
with collateral phenomena. He also brings forward some new facts in 
corroboration of Agassiz’s theory, especially the coincidence between 
the heights of the lines and those of certain “ cols ” (the latter being, 
strictly speaking, a few feet the lower), and the evidences of glaciers 
having formerly blocked up the mouth of Glen Roy. 
Now, the existence of a glacier-lake depends, firstly, upon that of a 
glacier damming up the mouth of the valley; and, secondly, upon 
there being no other outlet for the water. 
The following may, therefore, be considered the sequence of events 
described by Mr. Jamieson :— 
Glaciers from the Great Glen, Corry N’Eoin, Glen Treig, &c., 
blocked up the mouths of Glen Roy and Glen Spean, the last-mentioned 
glacier projecting into Glen Roy, and thus cutting off the connection of 
that valley with the “cols” just noticed ; accordingly a glacier-lake was 
formed in Glen Roy, and the beach forming the uppermost line was 
deposited ; the Glen Treig glacier then shrank so as to open out the 
higher col—that of Glen Glaster— thus causing the lowering of the 
level of the water in Glen Roy ; and then the middle terrace, or road, 
was deposited; the Glen Treig glacier then shrank again, until it 
withdrew out of Glen Spean, and that valley being now clear, the water 
escaped at Makoul; then, at about the level of that outlet, the lowest 
terrace was deposited. 
In a similar manner Mr. Jamieson accounts for the “roads” in 
certain smaller glens; and he also shows why some of them stop or 
are indistinct at certain points ; and, altogether, his explanations are 
so simple and so natural that the inducement is very great to believe 
tuat this much-debated question is at last settled. 
5. River-action is illustrated in a most mteresting paper, by Mr. 
Fergusson, on “ Recent Changes in the Delta of the Ganges,” and also 
in another on the Nile, by Dr. Leith Adams. Mr. Fergusson begins 
by enunciating certain principles of river-action, the first of which is, 
‘all rivers oscillate in curves, whose extent is directly proportionate to 
the quantity of water flowing through the rivers ;” but a certain loose- 
ness in the author’s mode of expression renders it necessary to be care- 
ful not to give a too literal interpretation to some of his sentences ; 
for instance, in this particular case, he evidently means to say that 
this principle is true when all other conditions are equal, for shortly 
afterwards he observes, that the extent or radius of the curves (ceteris 
paribus, understood, as before) is “ directly proportioned to the slope of 
