GEOGRAPHICAL DISTRIBUTION. 99 



exemplifies well the general fact. The island consists of two 

 peninsulas: one, the eastern, recent volcanic, with a large crater 

 at summit, and the other, the western, presenting every evidence 

 in its gorges and peaks and absence of volcanic cones, of having 

 become extinct ages since. In conformity with the view ex- 

 pressed, the coral reefs are confined almost exclusively to the 

 latter peninsula. Other examples are afforded by the Samoan 

 Islands. Savaii abounds in extinct craters and lava streams, and 

 much resembles Hawaii in character: it bears proof in every part 

 of being the last seat of the volcanic fires of Samoa. Its reefs 

 are consequently few and small : there is but a narrow line on 

 part of the northern shores, although on the other islands they 

 are very extensive. The absence of corals results obviously 

 from the destruction of zoophytes by heat, consequent on vol- 

 canic action. Submarine eruptions, which are frequent as long 

 as a volcano near the sea is in action, heat the waters, and de- 

 stroy whatever of life they may contain: after the eruption of 

 Kilanea, in 1840, there were numerous dead fish thrown on the 

 beach ; and many such instances in different regions are on 

 record. Other facts, illustrating the effects of volcanic heat in 

 preventing the growth of reefs, will be brought forward in the 

 following pages. 



The agencies affecting the growth of coral reefs being before 

 the mind, we may proceed to notice the actual distribution of 

 reefs through the coral seas. The review given is a rapid one, 

 as our present object is simply to explain the absence or presence 

 of reefs within the coral reef limits, by reference to the above 

 facts.* 



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 north- 

 ward deflection of the coral boundary line, as shown, accounts 

 for their absence. In the harbor of Callao (the seaport of Lima), 

 the temperature is sometimes down to 59° or 60 D F , and at the 

 Galapagos, Captain Fttzroy found the waters in September to fall 

 often to 62° P., and once to 5SJ F. This month, it should be 

 observed, cannot be the coldest of the year. In the bay of Pan- 

 ama, coral is reported to occur, but there are no reefs.f 



* In the valuable work by Mr. Darwin, the geographical distribution of reefs is 

 treated of at length in the Appendix, pp. 151-205. Hie facts here detailed have 

 been obtained from independent sources, except where otherwise acknowledged. In 

 accounting for the character and distribution of rttfs Mr. Darwin has erred in at- 

 tributing too much weight to a supposed difference in the amount of subsidence in 

 different regions, neglecting to allow the requisite limiting influence to volcanic 

 agency, and to the other causes mentioned. 



f Jour. Hoy. Geog. feoc, i, 09, on the Isthmus of Panama, by J. A. Lloyd. 



