132 T. TT. Vaughan — Origin* of Barrier Coral Reefs. 



were Sir John Murray. Admiral Sir W. J. L. Wharton, Alex- 

 ander Agassiz, and Stanley Gardiner. 



Murray introduced the idea of banks being built upward by 

 showers of the remains of pelagic organisms until the bathy- 

 metric zone of reef-forming organisms is reached, and he called 

 attention to the cutting of volcanic islands down to wave base. 

 According to his hypothesis as summarized by himself, u when 

 coral plantations grow up from submarine banks they assume 

 an atoll form owing to the more abundant supply of food to 

 the outer margin and by the removal of dead coral from the 

 interior portion by currents and by the action of carboiiic acid 

 gas dissolved in sea water"* and " that the barrier reefs have 

 been built out from the shore on a foundation of volcanic 

 debris or on a talus of coral blocks, coral sediment, and pelagic 

 shells, and that the lagoon channel is formed in the same way 

 as a lagoon." In Wharton's opinion the uniform depth of the 

 atoll lagoons in the Pacific is to be explained by corals grow- 

 ing upon the bases of volcanic islands which have been 

 reduced by wave action to wave base. Agassiz, besides accept- 

 ing in principle the views of Semper, Murray, and Wharton, 

 ascribed the formation of the platforms of barrier reefs to 

 marine erosion without change of sea level. Stanley Gardiner, 

 whose opinions are closely in accord with those of the investi- 

 gators mentioned, believes submarine planation effective to a 

 depth as great as 200 fathoms. 



Other investigators were obtaining results which, although 

 partly accordant with it, were really leading to an important 

 modification of the Darwin-Dana hypothesis. Andrews 

 pointed out that the platform of the Great Barrier Reef of 

 Australia has been depressed in Recent geologic time, that it 

 continues southward of the reef, and that only a minor part of 

 it is formed of coral growth. Hedley and Griffith Taylor, 

 who also studied the Great Barrier Reef, accepted the essen- 

 tials of the interpretation of Andrews and showed that coral 

 reefs of either atoll or linear form, which rise above shallow 

 platforms, owe their shapes to prevailing winds and currents. 

 Daly noted the accordance in the depths of drowned valleys 

 around the islands within barrier reefs, in the barrier reef 

 lagoon channels, and in the atoll lagoons of the Pacific, and 

 attributed this accordance to Recent rise of sea level subsequent 

 to deglaciation whereby the depth of water in the tropics was 

 increased some 20 to 30 fathoms, thereby submerging antece- 

 dent platforms of marine planation. 



This brief review of the leading coral reef theories leads to 

 the formulation of the questions : (1) (Jan a lagoon be formed 

 through submarine solution by sea water ; (2) what is the rela- 

 * Not italicized in the original. 



