484 pkof. w. s. boulto^t on the [Nov. 1904, 



Plate XL. 



Fig. 1. Northern Rhyolite (15), showing part of a nodule with mushroom- 

 growths and fibrous matter traversing small spherulitic spaces. The 

 matrix exhibits a perlitic structure with ' micro-lithophyses.' X 17. 

 (See pp. 457-58.) 

 2. Northern Ehyolite, showing part of the fibrous wall of a nodule 

 (in the upper part of the figure), enclosing felspar-phenocrysts, with 

 angular portions of the wall in the quartz-amygdaloid (to the right 

 of the figure). Bands of chalcedony and spherulitic felsitic matter 

 surround the fibrous wall and detached angular portions, the rest of 

 the amygdaloid consisting of quartz and brown spherulites. X 17. 

 (See pp" 459-60.) 



Plate XLI. 



Fig. 1. Northern Rhyolite, showing part of the double wall of a nodule, in 

 which felspar-phenocrysts and radiating tufted growths are visible. 

 The light space between the brown fibrous walls is filled with a quartz- 

 mosaic, enclosing small brown spherulites. X 17. (See p. 459.) 

 2. South-Eastern Ehyolite. Definite spherulitic growths are seen, but the 

 radial structure is only faintly visible in polarized light. Secondary 

 quartz has largely replaced the substance in the spaces between the 

 spherulites. X 17. (See p. 477.) 



Plate XLII. 



Fig. 1. Andesitic gritty tuff (205), with lapilli of andesite-glass filled with 

 felspar-microlites, vesicles, etc. x 25. (See p. 467.) 



2. Palagonite-tuff (Agg. Crag, b). At the top of the figure is a frag- 



ment of palagonite of a bright orange-yellow colour, enclosing felspar- 

 microlites and vesicles with well-marked zouary banding. The dark 

 border round this glass-fragment is made up of a mass of small frag- 

 ments of the same palagonite. The rest of the field consists of small 

 fragments of palagonite, in a light-grey matrix of secondary zeolitic 

 matter, x 25. (See p. 467.) 



3. Palagonite-tuff (308), showing abundant, green, vesicular palagonite- 



fragments, in which decomposed felspars are embedded ; zeolites fill the 

 vesicles, and make up the bulk of the groundmass. X 25. (See p. 469.) 



4. Coarsely-laminated halleflinta (574), showing finer bands of glassy dust 



and coarser bands of yellowish-green palagonite-tuff. (x 25.) 



Plate XLIII. 



Fig. 1. Palagonite-tuff (518), with characteristically-shaped glassy fragments 

 turned into green palagonite and filled with microlites of felspar and 

 round vesicles, showing zonary banding, and now filled with zeolites. 

 (X24.) 



2. The same, showing in the lower half of the figure a portion of a large 



lapillus of very vesicular light-brown glass. (X 25.) 



3. Finely-laminated halleflinta, with grey (coarser) and yellow (finer) 



bands of fine-grained glassy and crystal-dust. The glassy particles 

 are all converted into palagonite. x 25. (See pp. 467-68.) 



4. Red-and-green grit. (539), associated with the South- Eastern Fvhyolite, 



showing cloudy felspars, rounded grains of quartz, and dark curvi- 

 linear splinters of altered glass, which are yellow, green, or red in 

 colour. X 23.|. (See pp. 458, 475.) 



5. Andesite-lava (516 c) showing a mesh of felspar-laths in a matrix which 



is now largely converted into orange-yellow palagonite (the nearly- 

 black portions in the figure). In the centre is a group of pale-yellow 

 augite-crystals. x 24. (See p. 471.) 



6. Granulitic olivine-dolerite (28). There is a cluster of labradorite- and 



olivine-crystals, the latter converted into pale-green serpentine, with 

 haematite-rods and fibres along the cracks and borders. The matrix 

 consists of a 'granulitic' aggregate of felspar and augite. x 23^. 

 (See p. 480.) 



