80 ME. It. H. WORTH OX THE [vol. lxXV, 



prisms ; an olive chlorite and a quartz-mosaic together make up 

 much of the ground-mass, in which the other minerals are evenly 

 distributed. 



In 34 b, a very pale brown mica is the dominant mineral. Patches 

 of quartz-mosaic are scattered about the slide, tourmaline is rather 

 rare, but rutile is abundant. 



Farther from the granite the red coloration is replaced by grey, 

 the rocks become harder and more compact. LXXVI, S.E. 40, 

 from the bed of the western tributary of the Redaven, is a compact 

 grey rock, finely banded and looking much like a very fine grit. 

 The section shows a quartz-mosaic, varying in texture and markedly 

 coarser and freer from other minerals along irregular bands. 

 Interstitially there is much minute, very pale, green mica, which 

 also shows a tendency to banded segregation. There are mode- 

 rately large (0*24 mm.) irregular grains of an opaque mineral, 

 apparently a titaniferous iron-ore. On using higher powers, some 

 small rutiles and a very few small brown tourmalines are seen. 



LXXYI, S.E. 53, is a grey, hard, minutely-banded and irregu- 

 larly-spotted rock from the bed of the eastern tributary of the 

 Redaven. The general mass is a quartz-mosaic with very pale 

 green mica interstitially developed. The spots are due to net- 

 works of a black opaque mineral, probably magnetite, developed 

 between the quartz-grains. Higher magnifications show irregular 

 grains of rutile and a very few small brown tourmalines. 



LXXYI, S.E. 62 b, from the bed of the Flushcombe Water 

 above Forest Mine, is a pale-buff, very compact rock, which in the 

 field looks somewhat as though it may be a felsite, but faint grey 

 parallel bands can be seen with a lens. The section shows a 

 fine-grained mosaic of irregular interlocked granules, apparently 

 quartz, with interstitial mica in thin and irregular flakes. There 

 is a very little, extremely pale, brown tourmaline, and rutile is 

 scattered through the slide. 



In some of these shales, where oxidation has taken place, the 

 banding is well marked by thin layers of brown and grey : for 

 instance, in LXXYI, S.E. 9 c & d, quarry by the Yellake. 



These examples will serve to indicate the general structure of 

 the aluminous shales ; but, beyond the effect of the regional nieta- 

 morphism induced by the granite mass, there is also the local 

 influence of the intrusive aplite- and granite-veins. This is usually 

 confined to the immediate contact. 



At LXXYI, S.E. 29 b, on the Redaven, a little above the infall 

 of the eastern tributary, the effect of the intrusion of a narrow 

 •dyke of Meldon aplite has been to develop much pale red-brown 

 mica and much brown tourmaline in the shale at the actual contact. 



At LXXYI, S.E. 52, on the eastern tributary, a similar dyke, 

 possibly an extension of the same, has only developed pale red- 

 brown mica in the shale, and that for a distance of but 1 mm. or 

 thereabouts from the junction. 



At LXXYI, S.E. 30 a, where an aplite-vein crosses the Redaven 



