292 THE REVOLUTIONS OF THE CKUST OF THE EARTH. 



recent, and that it must have been covered by the sea at no very dis- 

 tant period. He supports this opinion by the accounts of travelers who 

 have visited Central Australia. They all declare the existence of a 

 vast surface in the center of the continent, surrounded with mountains 

 and covered with sand, in which are found the broken shells and the 

 carapaces of Crustacea as well preserved as if they were recent. The 

 strange flora and fauna of Australia, the salt lakes of its interior, as 

 well as the presence, frequently contested, of the more recent Tertiary 

 deposits, alike confirm this supposition.* 



Another proof of a slow rising is given us by the small island of Santa 

 Maria, not far from the island of Conception. Captain Fitz Koy found, 

 from the traces produced by the erosion of the sea and from the per- 

 forations of the Pholadites that the northern part of the island has been 

 elevated 10 feet, while the southern part has risen only 8 feet, above the 

 level of the ocean. We cannot attribute this rising to a retreat of the 

 sea, for the unequal elevation of the ancient line of erosion would be 

 then unexplained. Mr. Darwin attributes, also, to a general rising of 

 the continent of South America the beds of shells he observed at a height 

 of from 4 to 5 English feet. 



The shores of France, also, offer examples of an oscillation of the sur- 

 face of the earth. In the vicinity of Bourgneuf, not far from La Eo- 

 chelle, are the remains of a ship wrecked in 1752 upon an oyster bank 

 along the coast. To-day these remains are found surrounded by cultiva- 

 ted fields, and 4.2 meters (13^ feet) above the mean level of the ocean. The 

 neighborhood has gained in the course of twenty-five years more than 

 a thousand acres of ground merely by the rising of the coast.t Nor- 

 mandy and Bretagne, on the contrary, are sinking, although very slowly. 

 We find there are on the coast of Greenland submerged edifices which 

 date from the eighth century.| 



We must not forget that, according to an hypothesis generally admit- 

 ted in regard to the increase of coral formations, the presence of the 

 latter in a sea indicates a slow sinking of the bottom of the ocean. 

 The researches of Darwin upon these formations in Polynesia show that 

 the corals live ordinarily only at a depth of from 34 to 43 meters. 

 Now, on examining the coral islands, we find that the calcareous forma- 

 tions of the corals descend in abrupt slopes 335 meters below the 

 level of the sea. As the corals cannot live at such a depth, it must 

 have been the sinking of the bed of the ocean which caused them to 

 descend. 



These facts are sufficient to show that the plications and the rising of 

 the sedimentary crust have altered greatly the surface of the globe. 

 We will see that volcanic force, which is a more direct result of the cen- 

 tral heat, produces the same effects. It is these two forces, heat and 

 volcauic action, which have raised enormous masses of granite to the 



* Tltc Annah and Hajazint of Xatiiral Bititorij, vol. xv!, 3d ser., 1«65, p. '.VS.i. 

 i Girard, op. cit., p. 101. I Ihid., p. 110. 



