304 



PKOE. T. Gr. BONNET ON THE 



all probability produced the foliation of the rock, for the crystals 

 exhibit no sign of strain or fracture, but that the garnets existed 

 anterior to the crushing. These are of a brown-red colour, of 

 variable size, but seldom, if ever, more than 0"*4 diameter, com- 

 monly less, often about 0"'l. 



The genesis of these glaucophane-amphibolites is a question of 

 great interest, to which I directed special attention. The rock cer- 

 tainly appears interstratified with the other schists ; it is distinctly 

 foliated, sometimes banded, and simulates stratification. But I 

 agree with Dr. Barrois that we cannot, therefore, claim for it a 

 sedimentary origin*. There appears to.be little indication of a 

 graduated passage from the one rock to the other. As a rule the 

 divisional lines are rather sharp. Once or twice I noticed thin 

 bands of mica-schist in the amphibolite, which were difficult to 

 explain on the theory that the latter was intrusive. Still, as both 

 rocks have evidently been subjected to earth-movements of great 

 intensity, which have given rise to the structures now dominant, it 

 is possible that the ordinary minor indications of intrusion may have 

 been effaced, and small included masses of the schist may have been 

 flattened out by the same cause which has produced the simulated 

 stratification of the amphibolite. So that while I will not speak 

 positively on a question in regard to which Dr. Barrois, with his 

 much greater experience, fears to commit himself, I must say that 

 I incline to regard these amphibolites as rocks of igneous origin 

 and intrusive, but converted into schists by pressure and recrystalliza- 

 tion. The occasional " puckering " of the foliation looks as if some 

 movements had occurred after the present crystallization had taken 

 place. As to the condition of the schist when the amphibolite was 

 intruded I found no evidence, except that I noticed here and there 

 near the junction some rather lenticular bands which contained 

 some large, but ill-preserved, crystals, apparently of staurolite or 

 andalusite. 



(2) The District around Quimperle. 



In this district I examined a part of the sea-coast near the 

 embouchure of the river Pouldu, a spot about seven and a half 

 miles to the south of Quimperle, and carried on my work from that 

 town in a north-westerly direction for about three miles along the 

 Bannalec roadf. 



The town of Quimperle is built on the rough slopes of two glens, 



* Dr. Barrois suggests a similar explanation for the banded structure of the 

 hornblende-schists at the Lizard. It is possible that he may be right. That 

 foliated schists can be so formed has been shown by Mr. Teall, and is proved 

 elsewhere in Brittany, as will be seen. At the same time I did not myself see 

 in the He de Groix nearly such good imitations (if I may use the phrase) of the 

 phenomena of bedding as there are at the Lizard. Moreover, the amphibolites 

 are comparatively thin bands, often only a few yards thick, and this structure 

 is most conspicuous in their outer part, while the hornblende-schists of the 

 Lizard are very thick. 



t It would be difficult to find a more picturesque place than Quimperle, or 

 a hotel more pleasantly situated or more comfortable than the Hotel de France 

 et d'Angleterre, where I spent five days. 



