108 Messrs. Hicks 8 Davies—Pre-Cambrian Rocks of Ross-shire. 
magnetite and a few minute garnets are scattered through the rock, 
the sphene being more frequent in the mica bands.—T.D. | 
In the district to the S.E., and along the road extending from 
Slattadale, on the shore of Loch Maree, to Lake Padnaseally, nearly 
all the varieties of the gneiss and schistose rocks already mentioned 
are met with. The abundance, however, of black mica found in 
‘some of the beds along this line is remarkable. In some places it 
forms a dense black rock, containing occasional nests of felspar and. 
very thin lines of quartz, but otherwise consisting almost entirely of 
this mineral. These rocks and the gneisses described in Notes 4 and 5 
oceur about Slattadale and along the south-west shore of Loch Maree. 
[Nore 4.—This rock presents the aspect of a fairly typical 
gneiss. It is composed of a mixture of two felspars with quartz, 
and numerous alternating bands of black mica containing much 
sphene in pale yellow grains and crystals. In thin section it much 
resembles the rock No. 8, the intimate intergrowth of the quartz 
with the felspar being strikingly similar, the main differences consist- 
ing in the more numerous and often closely-packed mica bands and. 
the greater abundance of the felspars. The quartz here is sometimes 
developed in continuous bands, which resemble lengthened-out 
crystals, and it is only by the use of polarized light that these are 
shown to consist of numerous closely-developed crystals. They lie 
more or less parallel with those of the micas. The individual 
rounded crystals inclosed in the felspars are not so frequent here. 
The minute empty cavities are also abundant, while small plates of 
mica are frequently also included. Orthoclase is in crystalline 
masses, somewhat altered, with a little plagioclase. They are 
intimately crystalline with each other and with the quartz, this 
latter constituent is in about equal proportion to that of the felspars 
combined. The mica is of the same species as in the preceding rock. 
Sphene is abundant, and more so in the biotite bands.—T. D.] 
[Nore 5.—This rock both macroscopically and microscopically 
strikingly resembles the last described. The quartz and the felspars 
bear the same crystalline relation to each other, and the latter con- 
stituent is in much the same degree of alteration. The main differ- 
ence consists in the abundance of the mica (which is also characterized 
by a greater opacity and stronger dichroism), and the sphene crystals, 
which are so thickly aggregated in some places as to crowd out the 
ordinary constituents. Garnet is also present, but is not frequent. 
Here and there is a little green hornblende.—T. D.] 
Between Lake Padnascally and Gaerloch, along the line of the 
Kerrie River, hornblende rock's prevail, usually as hornblende slates 
and schists. At and about the falls of Kerrie these slates dip so 
evenly and regularly that_at a distance one can hardly realize that 
they are not ordinary Silurian slates. They are, however, on closer 
examination found to be highly crystalline rocks, the whole surface 
being covered with fine needle-like crystals of hornblende. Some 
are more coarsely crystalline, but the majority here are fine-grained. 
The beds dip at a high angle, to the N.E., and usually are not at all 
contorted. The specimen described, Note 6, is from near this spot. 
