iv Transactions of the South African Philosophical Society. 



Island is a gigantic agglomerate neck like those that the author 

 has described from Griqualand East, on the flanks of the Drakens- 

 berg Mountains. Two rocks of a type unusual to volcanic islands 

 were brought back by the expedition, and these call for a review 

 of the facts already known about Oceanic Islands. Of the two 

 rocks in question one was a white mica and biotite gneiss, from 

 Tristan d'Acunha, the other a lava containing foreign fragments 

 from Nightingale Island. In the Falkland Islands a number of 

 rocks are found which are not only similar to the South African 

 Bokkeveld Beds, but the fossils contained in them are the same. 

 An identical fauna is found in Devonian rocks in South and North 

 America, and it appears certain that the land from which the 

 sediment was derived, which now contains these fossils, was 

 continous through a great arc, from Cape Town to South and 

 North America. The European Devonian fossils are quite different. 

 The land connection between Africa and South America is confirmed 

 by the evidence of the Jurassic Beds, and by the distribution of 

 living animals. It is from a base made up of rocks which went 

 to form this old continent that the volcanic cones of Tristan 

 d'Acunha and Inaccessible Island rise, and through which the 

 rocks burst that now go to form the agglomerate plug of 

 Nightingale Island. St. Paul's Eocks, in mid-Atlantic, the Island 

 of Eockall, of Mayo, in the Cape Verde Islands, the Canary 

 Islands, Ascension, South Georgia, and Gaussberg, in the Antarctic, 

 all contain rocks of a distinctly continental type, as well as the 

 more conspicuous volcanic ones. In the West Indies there is also 

 evidence that the volcanic islands rise from a submerged continental 

 ridge. There are a number of legendary islands — Atlantis, Antilla, 

 Brasil, and the famous Island of St. Brandan — which are supposed 

 to have sunk beneath the water in comparatively recent years, 

 but it is certain that these must owe their origin to pure invention. 

 In the Pacific, New Caledonia is entirely of a continental type, but 

 recently the truly volcanic islands of Fiji, which have been thought 

 to be purely volcanic, have been shown to be built on a platform of 

 old sedimentary beds. The Solomon Islands and the New Hebrides 

 have likewise yielded, on close examination, extensive areas of old 

 sedimentary rocks. The Tonga Islands, though no old sedimentaries 

 show above sea-level, nevertheless the fine ash thrown out from the 

 volcanoes shows that beneath the cones there are the same types 

 of rocks as in Fiji and New Caledonia. Non- volcanic material 

 brought up in the pipes of volcanoes is known from Italy, Germany, 

 Scotland, and South Africa, and these afford evidence of the 

 remarkably cool nature of some volcanic outbursts. In South 



