. Discovery. Science. 92 DISCOVERY Garnet albite schist. Garnet albite schist with mica and banded with a sandy limestone. hornblende Tristan da Cunha Group This group, consisting of the five islands, Tristan, Nightijigale, Middle, Stoltcnhoff, and Inaccessible, lie in lat. 37° S., long. 12° \V., which is about 1,500 miles west of Cape Towii. It was discovered by Tristan da Cunha about 1508, but only became inhabited about the beginning of the nineteenth century \\hen Napoleon went to St. Helena. Point and westwards to just bej-ond the Hardy Rocks. That a more complex state exists in the neigh
. Discovery. Science. 92 DISCOVERY Garnet albite schist. Garnet albite schist with mica and banded with a sandy limestone. hornblende Tristan da Cunha Group This group, consisting of the five islands, Tristan, Nightijigale, Middle, Stoltcnhoff, and Inaccessible, lie in lat. 37° S., long. 12° \V., which is about 1,500 miles west of Cape Towii. It was discovered by Tristan da Cunha about 1508, but only became inhabited about the beginning of the nineteenth century \\hen Napoleon went to St. Helena. Point and westwards to just bej-ond the Hardy Rocks. That a more complex state exists in the neighbourhood of Swain Bay is evidenced by the specimens given by the islanders to the writer. These might almost be said to be plutonic, but it is thought ^ that they are of the nature of bombs. To the west and about twent\"-two mUes from Tristan there are the four islands mentioned above. Nightingale, the southernmost of the four, is rectangular in shape, and in size one mile by three- quarters. High cliffs bound the south, east, and west sides. The northern slopes descend gradually to the. -TYPICAL SEDIinSNTARY ROCK SCENERY, PRINCE OI,.\V HARBOUR, SOUTH GE0RGI.\. The island of Tristan is a volcanic cone rising to 6,400 ft. In shape it is an octagon about eight miles across. The first 2,000 ft. are very steep, but after this the slope ° or less. At 3,200 ft. the slopes become deeply indented with drainage ravines. These continue for about 500 ft., when the slopes become verj- rugged with minor rocky knobs. This rough surface continues up to 5,700 ft., where the final cinder cone' begins. The old crater at 6,300 ft. now forms a snow-water lake. The vegeta- tion line is about 3,800 ft. above sea level. The mountain is built of successive flows of lava mainly basaltic in character. Many vapour vents occur, and the rock varies from compact to very vesicular in texture. The lowest lava forms a lava plain at the north side of the island, and this plain has a number of small
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