MEETINGS. 255 



5. — Creve Coeur {the eastern horn of the Mont diet promontory). 



This spot has been already reported on, but a few 

 peculiarities seem worth mentioning. The rock is a reddish 

 granite containing a few inclusions of diorite and many dark 

 spots, which though of undefined contour, probably indicate 

 other inclusions of the same rock blended and dissolved in 

 the granitic magma. No intrusive dykes were noticed in the 

 granite. In this respect it contrasts with the diorite which in 

 Guernsey is always intersected by numerous dykes of various 

 kinds. This difference probably indicates that the granite 

 is of a more recent age than the diorite. A remarkable 

 feature is a dislocation or crushing plane running east and 

 west. Small veins of quartz felspar and chlorite accompany 

 it. These are probably metamorphic products derived from 

 the granite which near the dislocation is everywhere consider- 

 ably altered, being in places converted to a quartz felsite 

 resembling hornstone, whilst in others it passes into a purple 

 porphyry with orthoclase crystals. Pebbles resembling this 

 porphyry occurring in the beaches on the north side of the 

 Island have long since attracted the attention of the Geological 

 Section, but no similar rock had yet been found in situ. 



e.—Sark. 



This island was visited on the 7th July, 1898. A descent 

 was made to the Grande Greve at the western foot of the 

 Coupee. The country rock here is the banded gneiss or 

 hornblende schist containing numerous inclusions of diorite. 

 These inclusions are surrounded by the deflected laminae and 

 bands of the schist which has behaved as a plastic material 

 would do under pressure in the presence of lumps of harder 

 matter ; the inclusions themselves in many cases also appearing 

 to have yielded in a lesser degree to the pressure. The 

 schist is intersected by numerous small granite veins, and also 

 by very large dykes of a disintegrated granitic rock, the 

 latter running vertically from top to bottom of the cliff and 

 decomposed in places to china clay. Whether these two 

 classes of granite veins are related was not determined. 

 Another large vein, perhaps 20 feet wide, runs up the cliff in 

 a direction somewhat parallel to the larger granitic veins, 

 but is of quite a different nature, being a mica syenite, and 

 though not containing much mica is doubtless of the same 

 age as our mica traps. It cuts the smaller granite veins, but 

 though close to the larger granite dykes does not meet them. 

 Numerous arches and tunnels, due to erosion, occur in 



