THE GEOLOGY OF THE ENGLISH CHANNEL. 135 



than do others. Small cubic crystals are not infrequent in these 

 inclusions. 



Schorl rock also occurs at 36a, S. 54" W. Edd., 17-5 miles ; 72, S. 23° W. 

 Edd., 19 miles ; 14f, S. 41° W. Edd., 20 miles. 



ANDESITES. 



354/4b. 6| miles W. from Rame Head. 



Strictly speaking a felsite. Eed- brown felsitic ground- mass, with 

 porphyritic orthoclase, quartz, and dark mica. One of several pieces 

 here dredged, with every indication of being practically in situ. Is 

 much like the andesitic felsite of Withnoe, but lacks the flow structure 

 sometimes present in the latter. The similarity of the specimens to 

 many, however, which have been collected at Withnoe practically 

 amounts to identity. Thus to the Cawsand mass and the two near 

 Withnoe we have to add another, and a submarine, patch of igneous 

 rock of the New Red Sandstone period. Apparently this exposure 

 is of some considerable area. A conglomerate containins; large frag- 

 ments of this rock was taken in the same dredging. 



M. 15a. S. 27° W. Edd., 20-3 miles. 



Brownish-grey trachytic rock. 



Well-marked flow structure. Ground-mass a devitrified glass (pala- 

 gonite). Some augite developed in rare crystals and crystalline areas. 

 Flakes of very dark brown mica rather frequent. Lines and micro- 

 dendritic growths of iron ore (?) hematite. Occasional patches of calcite. 



M. 15. Also yielded a more red variety of the above. 



GNEISS, 



Some latitude must be allowed in any classification which attempts 

 to discriminate Gneiss from Schist in this area. If anything, the writer 

 leans toward identification as the former in doubtful cases. 



354/1. N.W. by N. Edd., \ mile. 



A large stone or small boulder, angular with freshly fractured 

 surface. A grey-green foliated rock with plates of brown mica and 

 numerous garnets up to 1"75 mm. in diameter. Quartz fills thin joints 

 at right angles to the planes of foliation. The mica is so developed as 

 to give to the rock an easy cleavage. 



The pale-pink garnets are a characteristic feature ; these are much 

 cracked, and around them bend the less resisting minerals. There is 

 much blue-green actinolitic hornblende, the blades of which all 

 approximately conform to one direction. Mica is in much less 

 quantity than would appear from the hand specimen ; it is intensely 

 pleochroic, from pale straw-colour to dark cinnamon-brown ; its 

 occurrence is practically limited to the neighbourhood of the garnets. 



NEW SERIES. — VOL. VIII. NO. 2. K 



