W. M. Hutchings—Altered Igneous Rocks, Tintagel. 107 
whether it is subsequent to foliation, or whether it is only that some 
crystals, for some reason, escaped all sign of stress. 
Some of the rock from the north side of Bossiney Cove differs 
from that just described in the fact that it contains a large amount 
of muscovite, which mineral was absent in the former case. The 
muscovite here exceeds the biotite in quantity and is, indeed, the 
main component of the rock. It occurs mainly in small flakes, lying 
parallel to the plane of foliation, and felted together into compact 
layers. Sections cut parallel to these layers show many patches in 
which the muscovite is almost wholly unmixed with other minerals, 
and which, notwithstanding the presence of many flakes which lie in 
transverse directions, behave between crossed Nicols as if only one 
larger individual were present, giving sharp and distinct optic 
figures in convergent light. In other patches there is more or less 
intermixture of chlorite, or of biotite-flakes, giving a greenish or 
yellowish colour and causing blurred and indistinct optic figures. 
It is in transverse sections that the layers in question are best 
recognized as being built up of countless muscovite flakes compacted 
together. 
Similar occurrences of muscovite take place at several other points 
in the sheet, but it was not seen anywhere else in such large amount. 
The biotite of this occurrence resembles in all respects that of the 
one last described, including the apparent formation of a younger 
lot of it, but the individuals of the latter are fewer, and are larger 
and less sharply defined. Felspar is absent in this case; quartz is 
rather plentiful. There is no rutile in crystals of any size, but 
under high power the entire rock is seen to be full of very minute 
crystals and grains of it. 
Hpidote is almost as plentiful here as in the last instance, and its 
arrangement in the rock is practically the same, but it is not in quite 
such large crystals. 
The sections show that here the epidote has been intensely affected 
by the rock-movements, not only being broken and dragged asunder, 
and curved and twisted in all degrees, but being in some cases 
squeezed into lenticular streaks of crushed material, which is, so 
far as my observation goes, rare in the case of epidote, and tells of 
very great siress indeed. So far as these special sections go, there 
seems no question that all the epidote was formed prior to the 
foliation of the rock. 
Lying in among the micaceous and chloritic material at the south 
side of Bossiney Cove I found an occurrence of rock which deserves 
special mention, because it differs so very much in many respects 
from anything else seen in this sheet. It is dark grey in colour, 
very hard and compact, with quite a splintery fracture. Neither 
macroscopically, nor microscopically, is there the least sign of any 
foliation. The part exposed, or at all events seen at any accessible 
part of the outcrop, was limited to a layer of perhaps a foot anda 
half in thickness and four to six feet in length, forming a projecting 
ledge in among the rest of the rock. It made the impression of 
being part of a thin bed lying more or less parallel with the foliation 
