OCEAVIC CORAiL ISLAND SUBSIDENCE. 319 



in the ocean of nnany granitic mountain chains, they do teach 

 that there are long ranges, or Hnes, of volcanic ridges and 

 peaks, and some of these may be among the discoveries of 

 future dredging expeditions. A range of deep-sea cones, or 

 sunken volcanic islands, would be as interesting a discovery 

 as a deep-sea sponge or coral, even if it should refuse, ex- 

 cepting perhaps a mere fragment, to come to the suface in the 

 dredge. 



We may also accept, with some confidence, the conclusion 

 that atolls and barrier reefs originated in the same great 

 balance-like movement of the earth's cruse that gave elevation 

 and cold, in the Glacial era, to high-latitude lands. If so, the 

 tropics and the colder latitudes were performing their several 

 works simultaneously in preparation for the coming era ; and 

 it is a gain to us in our contemplations, that we hence may 

 balance the beauty and repose of the tropics, through all 

 the progressing changes, against the prolonged scenes of 

 glacial desolation that prevailed over large portions of the 

 continents. 



