GHOGRAPHICAL DISTRIBUTION. 339 
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 ; but the seas of the Galapagos grow some corals. 
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 no reefs, and this is attributed by Verrill to the 
rough tides of ten to twelve feet. Corals are living at La 
Paz, on 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 latitude 
18°, and Clipperton Rock is described as an elevated coral 
island. 
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. 
