220 THE BERMUDA ISLANDS. 



have been very thick. In his review of the question of great 

 elevation Mr. Guppy thus expresses himself: "So great has 

 been the sub-aerial denudation of these islands, that, although 

 the elevatory movements have brought up to our view deep-sea 

 deposits which have been formed in depths probably of from 

 1000 to 2000 fathoms, yet, notwithstanding this great upheaval, 

 the calcareous envelopes, or ancient reef-formations, usually 

 disappear from the slopes of the large islands at heights of 500 

 or 600 feet above the sea, and never came under my observa- 

 tion at elevations much over 900 feet 



" Besides the testimony afforded by the stripping off of the cal- 

 careous envelopes from the higher levels, abundant evidence 

 of the great degradation which these islands have experienced 

 is to be found in the exposure at the surface in various 

 islands of highly crystalline and other much altered igneous 

 masses (such as quartz-diorites, quartz-porphyries, gabbros, 

 felspar-rocks, altered dolerites, and serpentines), which, accord- 

 ing to Professor Judd and Mr. Davies, were formed and also 

 altered at great depths, and could only have been exposed by 

 extensive denudation. Of the rapid degradation of the surface 

 which the calcareous districts undergo in this region of heavy 

 rainfall, there can be no doubt. It should therefore be re- 

 membered, when examining this region, that although in post- 

 Tertiary times it has been an area of great upheaval, which a 

 moderate computation would place at not less than 12,000 feet, 

 it has also been an area of most rapid denudation" (" Solomon 

 Islands," pp. 125-26). After this admission of enormous waste, 

 the argument from the thinness of the coral-limestone loses all 

 force ; nor can it be reasonably claimed that the waste extended 

 only over a thin and upwardly-extended capping of rock, since 

 Mr. Guppy assumes for one of his important conclusions that 

 barrier and other reefs grow out on their own talus. With origi- 

 nation in a great depth there would be ample opportunity for 

 such outward growth, and the accumulation of vast thicknesses 

 of rock. And how would rock accumulated in this way differ 

 from rock accumulated through subsidence? And if great 



