On the Altered Rocks of the Western and Central Highlands. 307 
of Scotland coloured according to the new classification, and by 
numerous sections. Everywhere throughout this tract it could be 
proved that an older gneiss, which the authors called ‘‘ Laurentian,” 
was overlain unconformably by red Cambrian sandstones ; these again 
unconformably by quartz-rocks, limestones, and a gneissose and 
schistose series of strata, as previously shown in the typical district of 
Assynt. From the base of these quartz-rocks a perfect conformable 
sequence was shown to exist upward into the gneissose rocks, which 
is not obliterated by granite or any similar rock. 
The tract between the Atlantic and the Great Glen consists, 
according to the authors, of a series of convoluted folds of the upper 
gneissose rocks, until, along the line of the Great Glen, the under- 
lying quartzose series is brought up on an anticlinal axis. A pro- 
longation of this axis probably exists along part of the west coast of 
Islay and Jura, two islands which exhibit a grand development of 
the lower or quartzose portion of the altered Silurian rocks of the 
Highlands. 
From the line of the Great Glen north-eastward to the Highland 
border, the country was explained as consisting of a great series of 
anticlinal and synclinal curves, whereby the same series of altered 
rocks which occurs on the north-west is repeated upon itself. One 
synclinal runs in a N.E. and S.W. direction across Loch Leven. 
The anticlinal of quartzose rocks that rises from under it to the S.E. 
spreads over the Breadalbane Forest to the Glen Lyon Mountains, 
where it sinks below the upper gneissose strata with their associated 
limestones. Ben Lawers occupies the synclinal formed by these 
upper strata; and the limestones and quartz-rock come up again in 
another anticlinal axis corresponding with the direction of Loch 
Tay. The continuity of these lines of axis was traced both to the 
N.E. and $.W. 
It thus appeared that the crystalline rocks of the Highlands are 
capable of reduction to order; that the same curves and folds could 
be traced in them asin their less altered equivalents of the South of 
Scotland; and that in what had hitherto appeared as little else than 
a hopeless chaos, there yet reigned a regular and beautiful simplicity. 
In conclusion, Sir Roderick Murchison vindicated the accuracy 
of his published sections in the N.W. of Sutherland, which had 
been approved after personal inspection by Professors Ramsay and 
Harkness ; and he gave detailed reasons for disbelieving the accu- 
racy of the sections recently put forth by Prof. Nicol, which were 
intended as corrections of his own. He concluded by affirming 
that, through the aid of Mr. Geikie, the proofs of the truthful- 
ness of his own sections, showing a conformable ascending order 
from the quartz-rocks and limestones into crystalline and micaceous 
rocks, had now been extended over such large areas that there could 
no longer be any misgivings on the subject. 
F ebruary 20, 1861.—L. Horner, Esq., President, in the Chair, 
The following communications were read :— 
1. ‘* On the Coincidence between Stratification and Foliation in 
X 2 
