THE GEOLOGY OF THE ENGLISH CHANNEL, 137 



between crossed nicols. The mosaic in places is of larger and irregular 

 granules, in places of small granules of lenticular form the longer axes 

 of which lie parallel to each other and form lines flowing round the 

 crystals of the first order. The mica conforms in general direction to 

 these same lines, it shows moderately strong pleochroism, and its face 

 colours range from rich cinnamon-brown in basal planes to a rather 

 pale olive-brown in sections perpendicular to these planes. A very 

 little apatite is present. 



M. 16a. S. 2r W. Edd., 20 9 miles. 



Schistose rock. Dark grey and pale brown, lamination very clearly 

 defined ; fissile. Much dark grey mica on joint faces. 



Structure schistose. Irregularly bounded felspar areas occasionally 

 associated with quartz form " eyes," around which the other minerals 

 are bent. These felspars are all mvich clouded ; some are thickly set 

 with microlites, but polysynthetic structure is clearly discernible in 

 many instances. Most of the felspars are curiously isolated from their 

 surroundings and have a rounded form, as though due to friction. 

 White mica is abundantly developed, forming streams in which the 

 felspars appear as islands. Mingling with the mica is dull green horn- 

 blende in short blades and in grains. There are numerous long 

 patches and irregular areas of quartz mosaic, the quartz containing 

 some apparently fluid inclusions, prismatic microlites, the larger of 

 which are seen to be hornblende, and rather frequent blades of the 

 latter mineral. The mica does not appear to invade the quartz areas. 

 Apatite is fairly plentiful. There is occasional staining by iron oxide, 

 especially between the quartz grains and the blades of mica. 



This rock is a gneiss, and has evidently been subjected to extreme 

 pressure. 



M. 9k. S. 31= W. Edd., 217 miles. 



A grey gneiss. 



Schistose structure well marked. Somewhat clouded felspars appear 

 to form the only remaining original mineral. These show plagioclase 

 twinning; some have been broken across with the development of a 

 felspar mosaic along the line of fracture. There are two orders of 

 mosaic structure, the one coarser and composed of a very clear mineral, 

 the other much finer and containing minute hornblende and apparently 

 zoisite. For the more part the large felspars are surrounded by this 

 finer material, into which they have the appearance of having been 

 driven. Ilmenite, hornblende, and zoisite mark out the planes of 

 schistosity. The hornblende is almost entirely in minute blades and 

 needles of a bright l)lue-green. Prisms of apatite are frequent in the 



