126 CORAL-REEFS. 



believed by the residents to have been washed by the rain 

 through the broken masses of underlying rock ; the island 

 was thus rendered unproductive. Chamisso 1 states, that 

 earthquakes are felt in the Marshall atolls, which are far 

 from any high land, and likewise in the islands of the 

 Caroline Archipelago. On one of the latter, namely 

 Oulleay atoll, Admiral Lutke, as he had the kindness to 

 inform me, observed several straight fissures about a foot in 

 width, running for some hundred yards obliquely across the 

 whole width of the reef. Fissures indicate a stretching of 

 the earth's crust, and, therefore, probably changes in its 

 level ; but these coral-islands, which have been shaken and 

 fissured, certainly have not been elevated, and, therefore, 

 probably they have subsided. In the chapter on Keeling 

 atoll, I attempted to show by direct evidence, that the 

 island underwent a movement of subsidence, during the 

 earthquakes lately felt there. 



The facts stand thus; — there are many large tracts of 

 ocean, without any high land, interspersed with reefs and 

 islets, formed by the growth of those kinds of corals, which 

 cannot live at great depths ; and the existence of these 

 reefs and low islets, in such numbers and at such distant 

 points, is quite inexplicable, excepting on the theory, that 

 the bases on which the reefs first became attached, slowly 

 and successively sank beneath the level of the sea, whilst 

 the corals continued to grow upwards. No positive facts 

 are opposed to this view, and some general considerations 

 render it probable. There is evidence of change in form, 

 whether or not from subsidence, or some of these coral- 

 islands ; and there is evidence of subterranean disturbances 

 beneath them. Will then the theory, to which we have 



1 See Chamisso, in Kotzebue's First Voyage, vol. iii. pp. 182 and 



