THE LOWER FORMS OF LIFE. 127 



Now remember that in the whole district of coral formation in 

 the Pacific, there are numerous active and many extinct volcanoes. 

 It is part of Mr. Darwin's theory that the mountain which has 

 sunk in the middle of the lagoon island was, when surrounded by 

 the " fringing reef," an active volcano, as shown in the diagram ; 

 and it is a strikingly confirmatory fact that the known active 

 volcanoes are all in islands or coastland which have "fringing reefs." 

 When its activity was exhausted it began to subside, as seen in the 

 diagrams. 



It is quite true that Mr. Darwin's theory implies that the base of 

 the coral belt round the lagoon shall be at an enormous depth ; and 

 in many instances quoted by him this is actually the case. But 

 after a time the subsidence ceases. How long the submerged 

 mountain remains quiescent is not known ; but that a subsequent 

 upheaving takes place is proved by the fact that many of the 

 South Sea. Islands are entirely formed of Coral, from top to bottom. 

 Some of them are quite recent, and from 80ft. to 200ft. high, and 

 can only be accounted for by what I may term the indisputable fact 

 that they have been upheaved from the sea after the Coral polyp had 

 for ages been building up its reefs thereon. Great facts in confir- 

 mation of this sinking and submergence of large tracts of land and 

 mountains are well known to geologists. Marine strata are found 

 at the top of the Alps at 800ft. from the sea-level ; on the Pyrenees 

 at 10,000ft. ; on the Andes at 15,000ft. ; and on the great chain of 

 Himalayas at 18,000ft. Now, unless these mountains had been 

 raised up from the ocean, we must believe the ridiculous alternative 

 that the sea-level has subsided 18,000ft. ! 



On this subject, and the causes which operate in the rising and 

 sinking of the earth, and the proofs that both are in constant 

 operation, I must refer to " Principles of Geology," by Sir 0. Lyell, 

 where the subject is handled with great ability and research. 



But there is still a very interesting question among the many 

 connected with coral reefs, about which I must offer a few remarks 

 the rate of growth, and the known age of those now living, or 

 which have been formed during recent times. 



On this subject we have most interesting data furnished by 

 Professor Agassiz, in the researches upon which he has founded a 

 beautiful series of deductions as to the formation of the peninsula 

 of Florida. By actual experiment he determined that in the period 

 of fourteen years the crust of Coral formed on the new foundation 

 of Fort Taylor, at Key West, and Fort Jefferson, on the Tortugas 

 Islands, did not exceed one inch. But as branching Corals only 

 occupy half the space they cover, Professor Agassiz considers that 

 the real rate of growth does not exceed half an inch in fourteen 



