PERMANENCE OF OCEAN BASINS 277 



of oceans and continents is the supposed absence of abysmal 

 deposits on any existing land surface. The discovery, how- 

 ever, of true deep-sea ooze in Barbados and Cuba shows that 

 this argument is no longer valid.* There only remains one 

 other argument in favour of this theory, and that is the 

 structure of the oceanic islands. With two exceptions, re- 

 marks Dr. Wallace, they do not contain any Mesozoic or 

 Palaeozoic rocks, being mostly volcanic. Hence he concludes 

 that these islands must be of modern origin. How illusive 

 this conception is may be gathered from Dr. Blanford's f re- 

 marks on this subject: " If Africa, south of the Atlas, sub- 

 sided 2,000 fathoms, what would remain above water? So 

 far as ,our present knowledge goes, the remaining islands 

 would consist of four volcanic peaks, the Camaroons, Mount 

 Kenia, Kilimanjaro, and Stanley's last discovery, Ruwenzori, 

 together with an island, or more than one, containing part of 

 the Abyssinian tableland, which, like the others, would be 

 composed of volcanic rocks, but, unlike them, would consist of 

 horizontal or nearly horizontal lava flows, probably of 

 of Mesozoic age. In southern Africa, too, the peaks of the 

 Stormberg and Drakensberg, though not rising, or scarcely 

 rising above 10,000 feet, are the highest in the country and 

 consist of volcanic rocks. The same is the case with the 

 highest peaks in Madagascar, in Mexico, in the Caucasus, in 

 the Elbruz chain south of the Caspian, and in many other 

 parts of the world ; though the case of Africa is perhaps 

 the most rgimarkable." 



The question whether all the numerous oceanic islands that 

 are scattered about the Pacific and Atlantic Oceans are really 

 roMern volcanic products or of recent organic origin, has 

 also received some attention recently. According to- Dr. 

 Arldt,t Archaean rocks have been noticed on the Solomon 

 islands, gneiss and allied rocks occur on the New Hebrides 

 and New Caledonia, while even from the Marquesas have 

 been recorded ancient rocks. 



So far I have discussed only a very small portion of the 

 purely zoological aspect of the trans-Atlantic land connection 



* Gregory, J. W., " Geology of the West Indies," p. 307. 

 t Blanford, W. T., " Anniversary Address," pp. 34—35. 

 X Arldt, Th., " Entwicklung der Kontinente," pp. 457— 458. 



