208 FOUNDERS OF OCEANOGRAPHY 



reef would become first a barrier reef and then an atoll. 

 But in other areas which are stationary, or slowly rising, 

 platforms for coral reefs might be provided, as Murray 

 supposed ; and the coral growth, once formed, would no 

 doubt become converted into the ring-like atoU-shape by 

 natural processes, in accordance with Murray's views. It 

 is probable, however, that Murray attached too much 

 importance to solution, and that the lagoon is formed more 

 by mechanical erosion than by chemical processes. Great 

 destruction of the dead coral in the lagoon is now known 

 to be effected by the scouring action of tidal currents and 

 by boring algae, mollusca, and worms, and by the ravages 

 of fishes and Holothurians, which feed to a great extent 

 upon the broken-up coral on the floor of the lagoon. 



The late Dr. A. G. Mayer, of the Carnegie Institution of 

 Washington, for several years recently made important 

 investigations on the coral reefs both of Florida and Tortugas 

 in the Atlantic, and of Samoa in the Pacific, and found 

 that the rate of growth of reef -building corals in the Pacific 

 was about twice as rapid as that of corresponding genera 

 in the Atlantic, where there is much more precipitated coral 

 mud and the food conditions are less favourable. He 

 estimated that the existing reefs in the Pacific might easily 

 have grown to their present dimensions in 30,000 years — 

 since the last glacial epoch. He found at Samoa that the 

 corals, at their present rate of growth, add annually about 

 840,000 lb. of limestone to the reef ; but that, on the other 

 hand, about four times that quantity (3,000,000 lb.) is 

 being removed annually by the coral-eating Holothurians, 

 aided by currents. Dr. Mayer made a boring through the 

 fringing reef at Pago-Pago, Samoa, in 1918, at 675 feet 

 from the shore, and came upon volcanic rock imderlying 

 the coral at a depth of 121 feet (20 fathoms), just the right 

 depth for a platform suitable for reef-building corals. 



W. M. Davis, of Harvard, from a critical examination 

 of the physical features of islands and their coral reefs, comes 



