266 Miss C. A. Raisin—Greenstones & Schists of S. Devon. 
series, the chlorite schists consist of clear and definite crystalline 
grains, among which I find felspar to be rare and have not yet 
certainly identified augite—while these northern greenstones are full 
of broken crystals of both minerals, together with viridite, dust 
resulting from the crushing, and a small amount of minute secondary 
hornblende and sericite (?), chlorite being generally rare, and often 
absent. The one rock is a true schist, the other nothing more than 
a schalstein. If Mr. Somervail ascribes the marked difference in 
character to more intense pressure, a very obvious difficulty would 
have to be met. As pointed out by Prof. Bonney, the chlorite schist 
exhibits at places not only a well-defined mineral banding, but also 
a cleavage cutting transversely across it, which appears to be in 
close relation with the general cleavage of Devonshire.! If, therefore, 
pressure metamorphism be invoked to account for the origin of the 
chlorite schist and its banding, the force must be relegated to an 
earlier period, and thus the rocks affected by it, even if originally 
igneous, cannot be of Devonian age. : 
Of themselves, however, these schistose rocks afford interesting 
study, as in the case of other west-country greenstones.? One type*® 
(from the coast near Redlap, and also from a quarry for road metal 
N.W. of Stoke Fleming), is clearly an ophitic dolerite,‘ but exhibits 
changes which have resulted from the crushing of the rock. Much 
of the augite is still very fresh and clear, but it seems to have been 
brittle, and to have broken along cleavage planes, forming fragments 
with sharp straight boundaries. Often there is a border of a horn- 
blendic mineral, partly an alteration product, although some is not 
unlike the serrate fringe of ‘secondary enlargement’ described by 
Van Hise,® having cleavage planes continuous with those of the 
original crystal. A fibrous hornblende, which is probably asbesti- 
form, also seems to have formed at places, where a fragment of 
augite has been drawn out in the shearing of the rock. Elsewhere, 
as Professor Bonney suggested to me, strands of a very pale viridite 
seem to be connected with remnants of augite crystals,’ and, in some 
cases, the viridite encloses small pieces, fragmental in outline, now con- 
verted into fibrous actinolite, which very probably have resulted from 
the crushing of a crystal of the pyroxene. Professor Bonney sug- 
1 Q.J.G.S. 1884, vol. xl. p. 8, fig. 4, p. 22. ‘ 
2 Q.J.G.S. 1876, vol. xxxii. p. 407, S. Allport. Q.J.G.S. 1876, vol. xxxii. p. 155, 
and 1878, vol. xxiv. p. 471, J. A. Phillips. Q.J.G.S. 1880, vol. xxxvi. p. 285, and 
1886, vol. xlii. p. 392, F. Rutley. Brit. Petroer. J. J. H. Teall, p. 228. 
* Somewhat like the Carlion rock (No. 7) of Mr. Rutley, Q.J.G.S. 1886, p. 397. 
The augite resembles that of fig. 2, p. 898. 
+ Cf. Mr. Allport, Q.J.G.S. 1876, p. 419. 
° As, for example, in the Lizard gabbro and basalt. Q.J.G.S. 1877, vol. xxxiii. 
pp- 904, 907, Prof. Bonney, “On the Serpentine and Associated Rocks of the 
lizard.’ See also Q.J.G.S. 1885, vol. xi. p- 520, ‘On the so-called Diorite of 
Little Knott,’’? and Q.J.G.S. 1888, vol. xxxix. p. 256, ‘‘On Hornblende Picrite 
from Anglesey,”” Prof. Bonney. Also Q.J.G.S. 1878, p. 493, J. A. Phillips. 
‘* Perimorphic’’ hornblende of Mr. Harker, Q.J.G.S. 1888, vol. xliy. p. 452. 
° Amer. Journ. Science, 1887, vol. xxiii. p. 388, fig. 8; also U.S. Geol. Survey, 
5th Rep. 1883-4. 
1 Cf. Brit. Petrogr. J. J. H. Teall, pp. 216, 230. 
