in the Pacific, S^c. 75 



Fahr. Throughout the coral archipelago to the eastward of 

 Tahiti, the surface temperature ranges from 78 to 81°. The 

 same may be said of that in the neighborhood of the detached 

 islets, between Tahiti and Samoa to the west. Throughout 

 this region, I observed all kinds of coral flourishing in perfec- 

 tion on the outer plateau of the reefs, at a depth of seven, 

 eight, and in some cases, as that just cited, twelve or thirteen 

 fathoms. 



In our own hemisphere, in the vicinity of Eleuthera and 

 Abaco, and also of the Stirrup Keys on the N. E. edge of the 

 great Bahama Bank ; I have dredged up considerable masses 

 of Meandrina from a depth of sixteen fathoms, and in sailing 

 over Salt Key Bank, have seen them, on a calm day, in twenty 

 fathoms. This is probably attributable to the increased tem- 

 perature caused by the proximity of the Gulf Stream which 

 has here a heat of 85° Fahr. The most compact and vigor- 

 ous growth, may, I think, however, be considered as prevail- 

 ing, in general, at a depth of from three to eight fathoms. 



To assume, therefore, that the lagoon islands are based upon 

 extinct submarine volcanoes, we must also suppose that these 

 all had their summits raised to nearly an uniform level, and 

 that, the one best adapted to the habits and development of 

 the coral animal, an arrangement scarcely within the bounds 

 of probability. It is difficult to believe that some two hun- 

 drea or more craters, if they ever existed in so narrow a space 

 as that occupied by some groups containing that number of 

 lagcon islands, nowhere presented more than one hundred or 

 one hundred and twenty feet difierence of level. 



But granting that all these requisites for the establishment 

 of this theory existed ; it ofiers no explanation of the circum- 

 stance that some of the reefs have, as ascertained by sound- 

 ing, a thickness of several hundred feet, and of their fossil 

 representatives in the chalk and marine limestone being found 

 in sTata of still greater density. Neither does it in any way 

 account for the existence of extensive shore reefs like those of 

 Samoa, Hawaii and Tahiti ; or of encircling reefs with la- 

 goo IS between them and the shore, as at Vanikoro and several 

 of the New Hebrides and Friendly Islands ;^ or for the im- 



