CHAPTER XIX 



THE THEORIES OF ATOLL AND REEF FORMATION PUT 



FORWARD SINCE THE PUBLICATION OF DARWIN'S 



THEORY— THE THEORY OF "SOLUTION" 



The voyage of the Beagle had given Darwin the information 

 necessary for completing the development of his theory of 

 atoll formation. The voyage of the Challenger furnished the 

 material for the origin of the rival attempt at the solution of 

 the problem, and the formation of a definite new theory to 

 replace that of Darwin. 



On April 5, 1880, Dr. John (now Sir John) Murray 

 published, in the Froceedings of the Royal Society of Edinhurgh, 

 a paper on " The Structure and Origin of Coral Reefs and 

 Islands." 



The new theory thus brought forward differed essentially 

 from the theory of " Subsidence " in practically every detail, 

 for Murray started with the knowledge — which Avas not avail- 

 able for Darwin — that submarine banks did exist in the 

 ocean. In this new theory, the basis of the islands or reefs 

 was not a sinking one, and in the place of the sinking peak of 

 land, Murray pictured a volcanic elevation of the floor of the 

 ocean. This elevation reaches to the depth limit of coral 

 growth by one of two processes : if it were originally pro- 

 jecting above the water it becomes worn down by the action 

 of the waves, and if it is too far below the surface, it becomes 

 raised by the deposit upon it of Glohigerina and Pte7vpod ooze. 



" The soundings of the Tuscorora and Challenger have made 

 known numerous submarine elevations ; mountains rising 

 from the general level of the ocean bed, at a depth of 2500 

 or 3000 fathoms, up to within a few hundred fathoms of the 

 surface. Although now capped and flanked by deposits of 



221 



