THE GEOLOGY OF THE ENGLISH CHANNEL. 181 



few prismatic microlites, and enclosure of minute cavities. Apatite is well 

 developed also. — E. B. T. 



H. 24. Trawled 14 or 20 miles 8.S.E. of Start Point. Weiglit about 

 4 cwt. 



A rather coarse-grained hornlilendic granite, of darkish tint ; the felspars of 

 slightly pinkish hue. Both hornblende and dark mica are present in abund- 

 ance. The felspar is much decomposed, and is chiefly orthoclase. Aj^atite 

 present — E. B. T. 



H. 21. Trawled 16 or 17 miles S. of Eddystone. Weight about 5 cwt, 

 A granite of medium grain, with faint pink-tinted felspars, and in which 



hornblende is abundantly visible ; of biotite there is much less. Though the 



felspars are much decomposed, pl.agioclase can be detected in some quantity. 



Apatite seems nearly absent. Quartzes are clear, but moving bubbles are 



frequent in the liquid inclusions. — E. B. T. 



H. 28. Trawled 15 miles S. of Start Point. Weight 3 to 4 cwt. 

 To the eye much like No. 24, but differs a little in shade. Biotite more 

 abundant than hornblende ; apatite very abundant. — E. B. T. 



One Gneiss. No. 36. 



H. 36. Trawled about 21 miles S.W. of Start Point. Weight 8 or 9 cwt. 



Quartz, felspar (plagioclase predominating), brown mica and some white 

 mica, apatite. Prof. Benney adds : " The rock, I think, is undoubtedly a 

 gneiss, and it is of an Archsean type." — T. G. B. 



Three Granitoid Gneiss. Kos. 3, 28, 61. 



H. 3. Salcombe Block, buried at Brixham Orphanage. 



A rather fine-grained granite-looking rock, in which a certain streaky 

 arrangement of the mica is apparent, the felspars fresh and translucent. 



The thin slice shows the micas distinctly set in one direction mainly ; they 

 wrap around the felspars or larger quartzes. The felspars show little or no 

 kaolinisation ; orthoclase more abundant than plagioclase. Both biotite and 

 muscovite are present. The quartz contains numerous delicate, long capillary 

 crystals, and cavities with bubbles. Apatite is present. — E. B. T. 



No. 28. Trawled 15 miles S. S.W. of Start Point. Weight 12 cwt. 



A very coarse gneiss rather than a granite. The quartz occurs both in 

 larger grains, rather full of cavities, and in aggregates of small granules. The 

 felspar is in parts more decomposed, and replaced by aggregates of secondary 

 products (micaceous and other microliths), or by a dull greenish granular 

 mineral, perhaps an impure epidote, but in parts is fairly well preserved, 

 microcline being common. There are also flakes of an olive-brown older mica, 

 and a few granules of iron peroxide. "This rock has the aspect of a very 

 ancient Archsean gneiss." — T. G. B. 



H. 61. Erratic on shore, S.E. of East Prawle. 



A light grey rock with the appearance of a fine-grained granite or granitic 

 gneiss. The foliation seen in the slice is not evident in the hand-specimen. 



