WoKTii. — I'etroloffical Notes on South Victoria Land Rocks. 487 



Turtle Island, 3. — Granular, soinowliat triable, black and very light 

 grey; in a fresher piece the light crystals are more amber-coloured. One 

 specimen shows that this rock occurs as nodules in a black basalt of vesi- 

 cular character. In some pieces the olivine and augite are clearly recog- 

 nizable as such in the hand-specimens. There are small specimens in 

 which olivine is present to the practical exclusion of all other minerals. 

 Nodules fro 711 basalt. 



Turtle Island, 5. — A very heavy black friable granular rock with irides- 

 cent play of colour on the grains represents apparently a nodu'e from basalt 

 in which the augite is present to the practical exclusion of all other minerals. 

 Kich-brown augite (pseudo-hypersthene) in large ophitic plates. No recog- 

 nizable pleochroism. The cracks stained a very dark brown, almost black. 

 Numerous inclusions, very dark brown, lying along two directions coin- 

 cident with the cleavage. Many of these inclusions are mere rods, others 

 are lath-shaped, some few are broader plates. They exhibit no pleochroism, 

 and appear to be isotropic. 



Turtle Island, 6. — A small weathered stone, grey aiul buff. Base appa- 

 rently feldspar, colourless, giving aggregate polarization in low tints, and 

 showing an occasional rod form. Granular magnetite scattered uniformly 

 throughout the slide. There is much of a golden-brown mineral in platy 

 and sometimes rough prismatic form, which is bright orange-yellow by 

 reflected light, shows no pleochroism, fairly high double refraction, and 

 straight extinction in sections approaching the rectangular : this occurs 

 in very minute forms. 



Inaccessible Island. 



The outermost of the Dellbridge Islands, so called because it was diffi- 

 cult to make the ascent. The northern side consisted largely of black basalt, 

 weathered to simulate stratification up to a height of nearly 20 ft. Near 

 the western end was a large scree of very fine rubble. The rocks were much 

 confused at the eastern end, where all the specimens were obtained, and 

 apparently dipped to the south. 



Inaccessible Island, 1.— Medium grey, trachytic texture. A very few 

 visible augites. White spots of intersecting feldspar crystals, in many 

 cases in small druses. Groundmass pale grey, consists of a felted mass of 

 minute fibres, with some magnetite, largely in very minute forms, and 

 numerous rather irregular prisms of very pale-green augite. Very numerous 

 feldspar laths, rather stout in section, for the more part simply twinned. 

 The symmetrical extinctions are + 20°, which suggest andesine. The 

 sUde also shows glomero-porphyritic structure, with aggregates of twinned 

 feldspar free from interstitial matter ; in one of these aggregates occurs a 

 crystal with very closely repeated twinning, but elsewhere all are simple 

 twins. One larger porphyritic feldspar occurs, with numerous inclusions 

 of augite and magnetite. An occasional pale-green porphyritic augite. 

 some with good crystal form, some much rounded, yet others entirely 

 clouded with magnetite. Augite-andesite. 



Inaccessible Island, 2. — Yellowish-grey trachyte, minutely open-textured. 

 A pale yellow-brown ground of varying depth of tint, of very feeble double 

 refraction, and containing both magnetite and sphene in minute forms, 

 with rarely a small grey-green prism microlite which is apparently augite. 

 Numerous well-terminated feldspar laths, and some few rather larger and 

 stouter forms. Around the larger of these the lath feldspars show flow 



