208 



VOLCANIC ORIGIN. 



sorting the materials have undergone, and from 

 their being strewed in narrow lines and sheets over 

 large spaces, with the same thickness in all its parts. 

 It is evident that if the pebbles of lava of whioh 

 some of the beds are composed, had been deposited 

 on a slope of any thing like the angle they now 

 have, either in air or under water, they must, many 

 of them, have rolled down and accumulated at its 

 foot, and the bed formed of them have been much 

 thicker there than elsewhere. Since the deposition 

 of these beds, therefore, they have been elevated 

 above the sea from 300 to 700 feet, and in some 

 places tilted up into an angle of f)0° j and in the 

 island of Erroob they have been covered up by a 

 thickness of 400 or 500 feet of igneous rock, some- 

 time after their deposition, and either previously or 

 subsequently to their elevation above the sea. 1 did 

 not succeed in finding any organic remains to give 

 a relative date to the formation of these rocks, but 

 the pieces of limestone look exactly like the masses 

 of limestone now forming in the coral reefs, just so 

 much altered by heat as we might expect from the 

 circumstances they would be. I believe that, geo- 

 logically speaking, these volcanic islands are of re- 

 cent origin. They are evidently an offset of that 

 great belt of volcanic operations, part of which ranges 

 at no great distance to the northward and eastward, 

 along the north coast of New Guinea, into the Solo- 

 mon islands, New Hebrides, and New Zealand. 

 On April \<)th we again anchored at Erroob, on 



