P. MACNAIR ON ROCKS OF HIGHLAND PERTHSHIRE. 173 
The next section in which he traces the relationship of the gneiss 
and quartzites to the mica-schist is that of Glenshee and Braemar, also 
partly in Perthshire. We may here note, however, in passing, that he 
believed the same relationship to exist in the Valley of the Tay and 
its tributaries, though he had not been able to examine them for some 
time. The greater part of Glenshee, he states, lies in the mica-slates, 
these beds showing a general inclination to the north. North of the 
Spittal of Glenshee he indicates a band of black carbonaceous shale 
dipping towards the north-west, and therefore conformable upon the 
mica-schists of the lower part of the valley, and compares it with the 
shales of Easdale and Oban. He also appeals to this bed as indica¬ 
ting the true position of these shales above the mica-schists. Proceed¬ 
ing up Glenbeg to the foot of the Cairnwell he indicates the existence 
of a bed of limestone still dipping to the north-west and overlaid by 
beds of gneiss and quartzite, and in his remarks upon this section 
says:—“There is no doubt that the great formation of gneiss, lime¬ 
stone, and quartzite rests on the mica-slate of the southern Grampians, 
and is thus a newer formation. I have also no doubt that it is a con¬ 
tinuous portion of the same great gneiss and quartzite formation which 
we have seen in the Breadalbane Highlands overlying the mica-slate 
of Loch Tay and Glen Dochart.” 
We need not follow the remaining part of this able paper, relating 
to the sections in the western Highlands. Enough has been given to 
enable us to perceive Nicol’s general views upon the structure of the 
southern Grampians. Firsts that along the margin of the Grampians 
we have a series of grits, greywackes, and clay-slates lying in their 
normal position on the south-western part of the chain, but evidently 
being infraposed by faulting and a reversal of the beds along the 
north-eastern part of the chain; the clay-slates thus appearing to dip 
under the mica-schists as seen along the margin of the Perthshire 
Highlands. And second, that these mica-schists were overlaid by the 
quartzites, limestones and gneisses of the central Highlands. 
Let us now compare the conclusions arrived at by Murchison and 
Geikie with those of Nicol. As we have pointed out, the main 
contention of Murchison and Geikie was that the schistose rocks of 
the southern Grampians were always superinduced upon the limestone, 
quartzite, and gneiss. We have shown that Nicol, in his paper, 
maintained that the quartzites of Ben-y-Ghloe, Glen Lyon, and Blair- 
Atholl actually occupied a higher horizon than the mica-schists. 
We have already noted how thoroughly the structure of the marginal 
parts of the southern Grampians escaped the notice of Murchison 
and Geikie, and in the following part of this paper we propose to show 
how the more recent researches upon the structure and succession of 
the rocks of this region have tended to confirm the views of Nicol. 
