DARWIN. 59 



and barrier-reefs have been formed during periods of 

 subsidence. 1 



No such strikingly original theory is propounded in the 

 second part of "The Geology of the Beagle? dealing 

 chiefly with volcanic islands. St. Jago, in the Cape de 

 Verde Islands; Fernando Noronha, Terceira, Tahiti, 

 Mauritius, St. Paul's, Ascension, St. Helena, and the 

 Galapagos are in turn more or less fully described, 

 according to the opportunities the explorer had possessed. 

 To some extent, as in the succeeding part, Darwin adapts 

 his views on mountain elevation too closely to those enun- 

 ciated by Elie de Beaumont. The third part of the 

 geology of the Beagle, entitled " Geological Observations 

 on South America," was not published till 1846. Even 

 this did not exhaust the contributions to geology made 

 from the Beagle voyage, for it did not include the papers 

 on the " Connection of certain Volcanic Phenomena in 

 South America " (1838) ; on the " Distribution of Erratic 

 Boulders" (1841); on the "J?ine Dust which falls on 



1 Mr. John Murray's views, derived from the experience acquired in 

 the voyage of the Challenger, and published in 1 880, tend to modify 

 Darwin's conclusions to some extent. Mr. Murray says that it is 

 now shown that many submarine mountains exist, which are usually 

 volcanic, and which, being built upon by various forms of shell- 

 bearing animals, could be raised to such a level that ordinary corals 

 could build upon them. He concludes that probably all atolls are 

 seated on submarine volcanoes, and thus it is not necessary to sup- 

 pose such extensive and long-continued subsidences as Darwin sug- 

 gested. This view is also in harmony with Dana's views of the great 

 antiquity and permanence of the great ocean basin. See "The 

 Structure and Origin of Reefs and Islands." By John Murray; 

 Proc. Roy. Soc., Edin., x. 505-18 (abstract) ; also Nature, xxii. 

 351-5- 



