OF THE SOUTH DEVON COAST. Ay 
that the chloritic schist exhibits less marked crumpling than the 
mica-schist. The more granular and uniform character of its con- 
stituents probably allowed of their being compressed into a smaller 
space, while the platy lamine of the mica were necessarily folded 
by a transverse pressure. It is rather difficult to obtain thin slices 
of this chloritic schist. Seven slides have been prepared, one from 
the rock by the signal-house on Prawle Point, another from the 
cliffs on the west side, and a third from the beds associated with 
mica-schist on the east (p. 6, in fig. 2). There is nothing in 
these calling for special remark, except that the belonitic character 
of some of the microliths is very conspicuous; they pierce the 
grains of quartz (and of felspar ?) like pins in a cushion ; there are 
also bands of secondary quartz, probably filling interstices produced 
by crumpling. A slide from the quarry near North Sands (p. 10) 
shows, more than any other, quartz grains like original clastic con- 
stituents, and contains some calcite ; but, as already stated, I believe 
the structure to be due to unequal pressure. One from the other side 
of North Sands, and one from near the Signal on the Bolt Tail, call for 
no special remark ; that from the headland south of Hope, has the 
felspar-like mineral in greater quantity and in larger grains than 
is usual. 
B. The Slaty Series. 
Of this group I have examined, microscopically, eight specimens, 
the majority being selected from critical positions. As an example 
of one of the normal rocks of the district, I take the silky slate from 
the quarry on the south side of the Toreross headland. This, cut 
perpendicular to the cleavage-planes, exhibits a moderately clear, 
finely granulated ground-mass, divided into minute lenticular 
streaks by dark lines of variable thickness—the usual aspect, in short, 
of a fine-grained blackish slate; the dark lines which are parallel 
with the cleavage-planes are due to the presence of carbonaceous 
matter, perhaps graphite, with probably some iron oxide. The 
clearer interspaces (not seldom minutely granulated with similar 
minerals), when magnified 300 or 400 diameters, appear to be com- 
posed largely of very minute scales, rather irregular in form, of a 
filmy mineral, which on applying the nicols gives pale colour tints ; 
these are probably one of the hydrous micas which seem to be com- 
mon to many slates, especially the more ‘ satiny ’ varieties, and to the 
phyllites; with them are associated extremely minute granules of 
(apparently) quartz. The slide, as a whole, is darkest when the 
cleavage-lines are parallel with the vibration-planes of one of the 
crossed nicols. 
A specimen of a slaty rock collected a little to the north of the 
marshy valley at Hall Sands (just to the north of a stone building), and 
so one of the nearest to the metamorphic rocks south of the valley, 
exhibits a structure generally similar to the above, except that the 
rock has evidently been much crumpled. A sharp zigzag fold tra- 
verses the slide, and some of the bands have been broken across, 
and one part of the fold thrust over the broken ends of the other, 
Q.J.G.8. No. 157. c 
