186 DREDGINGS OF THE MARINE BIOLOGICAL ASSOCIATION : 



The microscope shows that none of the olivine is left unchanged in the 

 meshes; in the serpentine are abundance of scattered haematite blotches. 

 Veins of chrysolite, or steatite, have a central line of black iron oxide bordered 

 often with red. Some of the enstatite is left unchanged, but only in 

 fragments in the middle of bundles of talcose crystals and steatite, to which 

 it seems to give rise by decomposition. — E. B. T. 



One Trachyte. No. 29, 



H. 29. Trawled 18 miles S.W. by S. of Start Point. Weight 3 or 4 cwt. 



Under the microscope this rock exhibits a glassy base, in part but probably 

 not wholly devitrilied, with a fairly well-marked fluidal structure. It has 

 undergone a certain amount of secondary change in the development of various 

 microlithic minerals, showing bright colours between crossed nicols, and of 

 specks of viridite. In this ground-mass occur numerous crystals of felspar, 

 sometimes rather rounded or broken-looking, which contain microliths or glass 

 inclusions, more or less altered. Some are plagioclase, probably oligoclase, 

 others appear to be orthoclase. There is a filmy green mineral associated with 

 streaks of opacite, which very probably replaces a mica, and there are some 

 grains of iron peroxide. No quartz grains are to be seen in the slide ; there 

 may be some apatite. — T. G. B. 



NON-CRYSTALLINE ROCKS. 



Two Conglomeratic-grit. Nos. 5, 26. 



H 5. Trawled 20 miles S.W. of Start Point. Weight 10 cwt. 



A coarse grit containing a few pebbles of rolled vein quartz, flesh-coloured 

 felspar, and fragments of fine-grained felsite-like rock. The rock has much 

 the appearance of an arkose. — E. B. T. 



H. 26. Trawled 15 or 20 miles W.S.W. of Eddystone. Weight 3 or 4 

 cwt. 



A moderately coarse grit composed wholly or almost wholly of rounded 

 grains of whitish quartz, cemented by pyrite. — T. G. B. 



One Killas. Attached to No. 15. 



H. 15. Trawled 16 miles S. of Start Point. 



One Triassic Sandstone. No. 10. 



H. 10. Trawled 20 miles S. of Eddystone. 



An unrolled fragment of a reddish-brown sandstone, similar in appearance 

 to the Triassic sandstones abundant either in mass or as outliers on the coast 

 of South Devon. 



One Neocomian Sandstone. No. 23. 



H. 23. Trawled 15 miles S.E. of Start Point. Weight 9 to 10 cwt. 



A sandstone with green grains; it has all the appearance of Neocomian 

 sandstone, as in Kent. — E. B. T. 



