BERMUDA ISLANDS. 265 



breadth, which surmount the annular reefs of almost all the 

 atolls in the Indian and Pacific Oceans. Moreover, there are 

 evident proofs (Nelson, ibid. p. 118) that islands similar to 

 the existing ones formerly extended over other parts of the 

 reef. It would, I believe, be difficult to find a true atoll with 

 land exceeding 30 feet in height ; whereas.. Mr. Nelson esti- 

 mates the highest point of the Bermuda Islands at 260 feet ; 

 if, however, Mr. Nelson's view, that the whole land consists of 

 sand drifted by the winds and agglutinated together, is correct, 

 this difference would be immaterial ; but, from his own ac- 

 count (p. 118), there occur in one place, five or six layers of 

 red earth, interstratified with the ordinary calcareous rock, 

 and including stones too heavy for the wind to have moved, 

 without having at the same time utterly dispersed every grain 

 of the accompanying drifted matter. Mr. Nelson attributes 

 the origin of these several layers, with their embedded stones, 

 to violent catastrophes ; but further investigation has generally 

 succeeded in explaining such phenomena by simpler means. 

 Finally, I may remark that these islands bear a considerable 

 resemblance in shape to Barbuda in the West Indies, and to 

 Pemba on the eastern coast of Africa, which latter island is 

 about 200 feet in height, and consists of coral-rock. I believe 

 that the Bermuda Islands, from being fringed by living reefs, 

 ought to have been coloured red : but I have left them un- 

 coloured, on account of their general resemblance in external 

 form to a lagoon-island or atoll. Professor Dana (Corals and 

 Coral Islands, pp. 218, 269) ranks them in this class. 



Supplement on a remarkable Bar of Sandstone off Pernambuco, 

 on the Coast of Brazil. (Originally published in the 

 Philosophical Magazine, October 1841, p. 257.) 



In entering the harbour of Pernambuco, a vessel passes 

 close round the point of a long reef, which, viewed at high 

 water when the waves break heavily over it, would naturally 



