80 ME. E. E. WALKER ON. THE GARNET-BEARING- [Feb. I904, 



felspar-laths, biotite-flakes, iron-ore, and quartz. The felspar and 

 biotite may sometimes be seen in ophitic relation, giving to the 

 groundmass the appearance of a quartz-diabase. Aggregates of 

 uralite occur, in addition to hornblende, and these seem to show 

 a change into biotite. Biotite-flakes are developed at the margin 

 of these aggregates, and the pleochroic colours of the mica may be 

 seen in scattered areas within the mass of uralite-fibres. 



The next type (3857) is a similar rock, but the felspars are of 

 a pinkish colour. Microscopically, it differs only in the fact that 

 quartz is most abundant, and the groundmass becomes more grano- 

 phyric in character. Aggregates of mica-flakes occur instead of the 

 uralite, and this probably indicates complete transformation of 

 uralite into biotite. There is a good deal of evidence for this change ; 

 but occasionally the appearance of the section suggests the opposite 

 conclusion, that is, the conversion of biotite into uralite. Apatite 

 is abundant in this last type, and is usually concentrated in the 

 more acid porphyrites. Garnet also is present in rounded crystals. 

 Corrosion has occurred, with the production of brown mica in 

 minute flakes (3833); plagioclase-laths are set at right angles to 

 the surface of the garnet, and give the appearance of a spherulitic 

 growth round the garnet. Apatite also occurs, and again seems to 

 be a product of corrosion. Biotite and plagioclase too have been 

 formed within the garnet. 



The most acid rock, and that which occupies the centre of the dyke, 

 is a pinkish granophyre. Idiomorphic felspars, either albite 

 or oligoclase-andesine with albite, Carlsbad, and Baveno-twinning, 

 occur in a confused intergrowth of quartz and felspar. Bounded 

 quartz-grains are set in the centre of rudely-spherulitic growths. 

 Chlorite with strings of epidote developed along the cleavage 

 represents original mica. 



The silica-percentages of these rocks show an interesting 

 gradation. 



Silica-percentages. Specific gravities. 



Diabase 47*76 2*872 at 15-5° C. 



Mica-porphyrite 54-*04 2-836 at 155° C. 



Mica-porphyrite (3856) 55*75 2*822 at 126° 0. 



Mica-porphyrite with granophyric 



groundmass (3857) 62*38 



Granophyre (3858) 68*66 2*753 at 12-1° C. 



The broad dykes which traverse Kirkfell, and are well seen in 

 the gullies of Kirkfell Crags, are quartz -porphyries (3901) 

 with a beautiful granopbyric groundmass. They are of a purplish 

 colour, due to aggregations of mica-flakes. The felspar is probably 

 very close to oligoclase. Xenoliths of a basic mica-rock are also 

 common (3898). A little to the west of Kirkfell summit a red 

 quartz-porphyry occurs (3899), containing quartz and plagioclase, 

 with phenocrysts of micropegmatite in a granular groundmass 

 of quartz and orthoclase. Exactly the same features are exhibited 

 by the Fence- Wood dyke on the opposite side of the valley. 



The larger apophyses of the "Wastdale-Head Granite occur in 

 rounded patches on the summit of Lingmell, at Bursting Knott, and 



