BY T STEPHENS, M.A., F.G.S. 93' 



reefs existed on land slopes at various heights above the sea 

 level, which proved that there had been no subsidence at 

 those particular points. But there was also in evidence the 

 fact that countless numbers of coral reefs and islands rising 

 from great depths, and with no land near them, were scattered 

 over vast areas in the Indian and Pacific Oceans. The 

 obvious conclusion was, that these must either have been 

 built up on a corresponding number of submarine peaks 

 and ridges conveniently situated at just the right depth 

 below the sea level, or that the coral polyps had begun their 

 work, ages ago, around and among the peaks and ridges of a 

 slowly subsiding continent, building ever upwards as the land 

 went down, until it was entirely submerged, and he unhesi-^ 

 tatingly adopted the latter hypothesis. 



(Reference to diagram.) 



The Darwinian theory was first published in 1842. It was 

 received with acclamation by scientific authorities in all parts 

 of the world, and quite twenty years passed before any 

 serious objections to its general acceptance began to be formu- 

 lated. With the indomitable energy, quick perception, and 

 freedom from prejudice, which were his chief charanteristics, 

 Darwin studied all the results of fresh explorations made 

 by contemporary workers that could throw light upon the 

 subject, but could find no ground for any material modifica- 

 tion of his original theory. With the improvements that 

 were made, especially in England and America, in the 

 mechanical appliances of surveying ships, the exploration of 

 the great depths of the ocean was greatly facilitated, and, 

 after the famous voyage of H.M.S. Challenger, Dr. John 

 Murray, one of the naturalists of the expedition, propounded 

 a new theory which was supported by several leading 

 scientists. 



Before giving an account of this theory, it is necessary to 

 briefly mention some of the additions to our knowledge of 

 marine natural history since the date of the voyage of 

 H.M.S. Beagle. The results of the Ghalle^iger Expedition, 

 and of other previous explorations of the depths of the 

 ocean, have shown that the floor of every sea, outside the 

 range within which it, is affected i)y deposits of river sediment, 

 or by the wearing away of the coast line, is covered down to 

 considerable depths with the shells and skeletons of myriads 

 of marine organisms, which have lived either on the sea 

 bottom or floating near the surface. The latter, especially in 

 the warmer seas, are present in such vast numbers, that, 

 though the individutls themselves are mostly very minute,, 

 their remains, accumulated during the course of long ages, 

 form a very large proportion of the materials which have 

 been gradually built up on the original foundation. 



