CORAL REEFS. APPENDIX. 203 



the paper of Capt. Wharton, noticed above, relative to the 

 formation of deep lagoons through solution. No facts bearing 

 on the subject are given. 



G. C. Bourne. " Coral Formations." Nature, Moh. 1, 1888. 



The author coincides with the views of Capt. Wharton as to 

 tlie inefficacy of solution in producing deep lagoons. "It has 

 seemed to me, as it has to him, that the solution of dead coral 

 rock in the interior of a reef does not sufficiently account for 

 the formation of lagoons, and that the true cause of the atoll 

 and barrier lagoons surrounded either by a reef which is 

 awash, or by a strip of low land, lies in the peculiarly favor- 

 able conditions for coral growth present on the steep external 

 slopes of the reef" The favorable conditions are supposed to 

 be due to the action ,of currents on coral growths [not a better 

 food-supply], currents of moderate strength " not so strong as 

 to dash them [the corals] to pieces, but strong enough to ])re- 

 vent deposition of sand. Such conditions are found everj'- 

 where on the external slopes," where tlie "main part of the 

 current flows tangentially around the obstruction," adds to 

 " greatest advantage around the periphery of a reef," and forms 

 a ring-shaped reef; " no theory of solution is required to exfjlain 

 the central depression." 



Mr. Bourne, as a non-believer in the tiieories of solution and 

 subsidence, fails, however, to explain liow the ring-form was 

 constructed below the zone of coral-growth ; the extension of 

 the lagoon far below this line remains unaccounted for. 



B. Irvine. " Coral Formations." Nature, Moh. 15, 1888. 



An attempt to determine the rate of solution of lime-car- 

 bonate in the sea. From experiments made on the genus 

 Porites (coral), using sea-water with a specific gravity of 1.0265, 

 and a tum[)erature of from 70° F. to 80° F., the author arrives 

 at the conclusion that "dead or rotten coral exposed to sea- 

 water under these circumstances is soluble to tlie extent of 5 to 

 20 ounces per ton." For further computation tlie autlior as- 

 sumes a reef with, a lagoon already formed, half a mile in 



