W. M. Hutchings—Altered Igneous Rocks, Tintagel. 105 
From the microscopic evidence of great stress in some of the 
minerals of both layers, it seems safe to conclude that both have 
been alike subjected to the pressure and movements which caused 
the foliation of the entire sheet, and that their separation is thus not 
due to any subsequent causes. And if, as seems reasonable, the 
passage of these sharply-separated layers into quite close inter- 
foliation negatives the idea of any prior bedding, it would appear 
probable that this curious structure was developed concurrently with 
the ordinary foliation, when the earth-movements took place which 
have so much affected all the rocks of this district. 
As before stated, much of the entire sheet of rock consists of the 
materials of these layers just described, variously intermixed, 
together with one or two other minerals. At some parts chlorite 
and calcite increase almost to the exclusion of felspar, at others 
felspar again plays a more prominent part. Biotite and muscovite 
vary from total absence to great predominance, and epidote again, 
which at some parts is very abundant, disappears entirely at others. 
Large bits of felspar are the exception, most of it being in smaller 
grains and fine mosaic, and with one exception, nothing at all 
approaching to original felspar is seen. 
Specimens from one point along Trebarwith Strand show the 
presence of a large amount of actinolitic hornblende. It is very 
pale green, almost colourless, and very slightly dichroic. It occurs 
with chlorite, into which much of it is in course of alteration. 
Felspar is in rather largish bits in these sections. A large amount 
of epidote is present, of yellow colour and rather strong dichroism. 
It is all in broken crystals and large, detached, irregular fragments, 
which frequently, at some distance apart, show their former unity. 
Sections cut across the schistosity of the rock show very plainly that 
the movements which caused foliation broke and dragged asunder 
fine large crystals of epidote, and gave an approximately parallel 
arrangement to a portion of the fragments. This question as to the 
age of epidote and other minerals, relatively to the foliation of the 
rock, will be referred to again. In the present instance there is no 
doubt that epidote crystals were formed in great plenty before the 
movements took place, and there is no sign of any having been 
developed since. 
Hornblende was not seen in any other sections, but would doubt- 
less prove to be present at other parts of the sheet if more specimens 
were taken. At a point only a few yards away it had totally 
disappeared, and epidote was present only in very small amount. 
Specimens from both sides of Bossiney Cove are interesting 
owing to the very large development of mica and of epidote. 
Some of the rock from the south side is made up mostly of biotite, 
with chlorite and numerous large crystals of epidote. Much of the 
biotite has a greenish tinge, and is at many points more or less altered 
to chlorite, much of which appears to have originated in this manner. 
Most of the biotite is in large irregular flakes, which lie with their 
flat sides parallel to the schistosity and are drawn out with the 
chlorite into long, slightly curving lines, But there is also a good 
