720 



MISS C. A. EAISIN ON THE 



planes in some examples, the species would seem to be a chlorite of 

 uniaxial character, possibly, in part at least, prochlorite of Dana. 

 The more transparent layers in the chlorite-schist slide are consti- 

 tuted chiefly of grains not usually elongated in form, in some cases- 

 adjoining in the manner of quartzite- or schist-grains, but often 

 separated by a pale greenish or dark deposit, composed partly of 

 not clear chlorite, partly of more opaque substance, this intermediate 

 material being often in more or less continuity with the mass of the 

 green chloritic layers. The grains thus defined have an appearance 

 as if they had been forced apart, possibly by local crushing of the 

 rock ; and this apj)earance occurs most markedly in slides from 

 districts where the rocks in the field had a disturbed aspect. 

 Professor Bonney calls attention to a somewhat " clastic look " in 

 specimens examined by him, and suggests its being due to the action 

 of " unequal pressure." The transparent grains themselves are 

 many of them un cleaved and fairly clear, except for minute enclo- 

 sures, small flakes of chlorite or other belonites ; and these grains I 

 suppose to be chiefly quartz. Of others, which show more or less 

 distinct cleavage, some at least, after hesitation, I identified as 

 possibly kyanite, the presence of this mineral being suggested by 

 Professor Bonney in some of the chlorite-schists. In some cases my 

 specimens show, as Bosenbusch describes, an extremely clear appear- 

 ance, with the occurrence of infiltration-products settled along the 

 very distinct cleavage-planes *. As is stated by Fouque and Levy to 

 be the character of thin slices, the grains are colourless and not 

 dichroic f . Pelspar seems to be present in certain slides as an occa- 

 sional grain, and it may occur more markedly in other specimens ; 

 but in many cases its appearance is not quite normal, and Professor 

 Bonney has suggested to me the possibility of the crystal consisting 

 of a secondary mineral replacing the original felspar. Such typical 

 characters of chlorite-schist I have noted in slides from rock obtained 

 along the coast northward of Prawle Point, from the cliff near 

 North Sands, and in others to be mentioned immediately. 



In a slide cut from the chlorite-schist which is quarried near 

 North Sands, I was interested to find hornblende occurring in 

 portions larger than the belonites described by Professor Bonney. 

 There are in the slide a fair number of specimens varying in size, 

 but all very characteristic ; they are green in colour, exhibit 

 dichroism, and have the cleavages parallel to a P well marked. 

 Host of the grains also are partially bounded by prismatic faces. 

 They occur, some of them intercrystallized in nests of quartzose 

 material, others in the greener bands of the rock, where, at parts, 

 they seem to merge into the chlorite, at parts seem as if eaten into 

 by the bordering epidote-grains. In chlorite-schist near Rickham 

 Signal the clastic aspect, previously described, is noticeable, and is 

 emphasized (even more markedly than in my specimen from North- 

 Sands quarry) by the deposition of calcite along cracks in some of the 

 clear mineral. Among the grains may be noted one of a twinned 



* Mikr. Phys. der petr. Min. p. 345. 

 t Min. Micr. p. 460. 



