268 TOILERS IN THE SEA. 



length, with "one of its sides covered nearly the 

 whole way with high trees." It is urged that, in an 

 old standing reef, the corals are of different kinds at 

 different parts, and all probably adapted to their 

 positions, where they hold their places, like other 

 organic beings, by a struggle with each other and 

 external nature, and hence their growth would 

 generally be slow, except under peculiarly favour- 

 able circumstances. " Almost the only natural 

 condition, allowing a quick upward growth of the 

 whole surface of a reef, would be a slow subsidence 

 of the area in which it stood." " If it be asked," 

 says Darwin, " at what rate in years I suppose a reef 

 of coral, favourably circumstanced, would grow up 

 from a given depth, I should answer, that we have 

 no precise evidence on this point, and comparatively 

 little concern with it. We see in innumerable points 

 over wide areas, that the rate has been sufficient, 

 either to bring up the reefs from various depths to 

 the surface, or, as is more probable, to keep them at 

 the surface during progressive subsidences ; and this 

 is a much more important standard of comparison 

 than any cycle of years." 



A few facts may be added, and left to carry their 

 own inferences. Dr. Allan experimented in 1830 

 to 1832 on the east coast of Madagascar. "To 

 ascertain the rise and progress of the coral family, 

 twenty species of coral were taken off the reef, and 



