GEOGRAPHICAL DISTRIBUTION. 303 



detailed have been obtained from independent sources, except 

 where otherwise acknowledged. In accounting for the char- 

 acter and distribution of reefs, Mr. Darwin appears to attrib- 

 ute too much weight to a supposed difference in the change 

 of level in different regions, neglecting to allow the requis- 

 ite limiting influence to volcanic agency, and to the other 

 causes mentioned. His conclusion that the areas of active 

 volcanos in general, are areas of elevation, and not of subsi- 

 dence, and the inference that reefs are absent from the shores 

 of islands of recent volcanic action on this account, do not 

 accord with the facts above stated : for example, the condition 

 of Maui, that it has no reefs on the larger half, that of the 

 volcanic cone of recent action, but has them on the other 

 half whose fires were long since extinct ; for it is not prob- 

 able that one end has been undergoing elevation, and the 

 other subsidence. 



Pacific Ocean. — The west coast of South America is- 

 known to be without coral reefs even immediately beneath 

 the equator ; and the seas of the Galapagos also grow no 

 coral. The northward deflection of the coral boundary line 

 accounts, as has been shown, for their absence. In the Bay 

 of Panama, and elsewhere on the coast, north and south, 

 corals occur in patches, but there are no reefs. There are 

 corals also at La Paz, near the extremity of the Peninsula of 

 California (p. 112). 



In Captain Colnett's voyage, allusion is made to a beach 

 of coral sand on one of the Revillagigedo Islands, in lati- 

 tude 18° ; besides this statement we have met with no allu- 

 sion to corals on any of the islands off the Mexican coast. 



Between the South American coast and the Paumotus are 

 two rocky islands, Easter or Waihu and Sala-y-Gomez, both 

 of which are stated to be without reefs. 



