254 THE POPULAR SCIENCE MONTHLY. 



islands. This may or may not have been often the case in the Pacific. 

 lUit it does not affect the question, except in so far as it may justify 

 Darwin's conception that reef corals can not grow on "loose deposits." 

 They may have ceased to be so soft and loose as they are when resting 

 in the quiet depths of the thousand-fathoms sea. This induration 

 may be part or an accompaniment of the process of elevation, but 

 whether it he so or not the process is equally one of elevation and not 

 of subsidence. In the island described by Dr. Guppy, the foundations 

 of the reef-building corals are seen resting directly on the remains of 

 the pelagic fauna, and both theories equally assume and assert the 

 uncontested fact that these foundations when the coral wall began to 

 grow must have been previously elevated to the requisite level, that, 

 namely, of from one hundred and eighty to one hundred and twenty 

 feet below the surface of the ocean. Mr. John Murray's explanation 

 is fully confirmed that the coral reefs often begin on shoals ; that 

 these shoals are due to elevations of the sea-bottom ; that the reef 

 when once established can and does grow seaward upon its own frag- 

 ments broken and submerged ; that these form a "talus" capable of 

 indefinite advance until the farthest limit of the shoal is reached ; 

 that the rearward ranks of the coral animals die as they are left be- 

 hind in the hot and shallow waters of the lagoon ; that their calcare- 

 ous skeletons are then attacked by the solvent action of the water, 

 are eaten away and carried off to form the materials of new reefs and 

 the shells of countless other creatures. These have likewise been con- 

 firmed by the investigations of Mr. Alexander Agassiz in the West 

 Indies. Often in the Pacific, as in all other regions of the earth, the 

 elevating forces rest for ages, having done all the work which on 

 some particular area they have got to do. The shoals remain shoals, 

 only covered with the walls and battlements of coral. This is the 

 case which accounts for countless islands never exceeding a certain 

 height. On the other hand, and " otherwhere," the elevating forces, 

 after a rest, resume their operation, lift up these coral walls and battle- 

 ments wholly out of the sea, and make other islands by the thousand 

 Avhich become the delight of man ; while in yet another class of cases 

 the elevations open out into volcanoes, and constitute great areas of 

 land which are among the most fertile regions of the habitable globe. 

 But everywhere and always the ubi(juitous coral animals fix on every 

 shoal and on every shore whether old or new, and resume the wonder- 

 ful cycle of operations in which they are a subordinate but a powerful 

 agent. 



In a recent ai'ticle in this Review I had occasion to refer to the 

 curious power which is sometimes exercised on behalf of certain 

 accepted opinions, or of some reputed prophet, in establishing a sort 

 of Reign of Terror in their own behalf, sometimes in philosophy, 

 sometimes in politics, sometimes in science. This observation was 

 received as I expected it to be— by those who, being themselves sxib- 



