chap. vi. Volcanic Islands. 141 



volcanic, or of modern coral rocks. It would be tedious 

 to give a long catalogue of all the volcanic islands ; but 

 the exceptions which I have found are easily enumer- 

 ated: in the Atlantic, we have St. Paul's Rock, de- 

 scribed in this volume, and the Falkland Islands, 

 composed of quartz and clayslate ; but these latter 

 islands are of considerable size, and lie not very far 

 from the South American coast : 1 in the Indian Ocean, 

 the Seychelles (situated in a line prolonged from Mada- 

 gascar) consist of granite and quartz : in the Pacific 

 Ocean, New Caledonia, an island of large size, belongs 

 (as far as is known) to the primary class. New Zealand, 

 which contains much volcanic rock and some active 

 volcanos, from its size cannot be classed with the small 

 islands, which we are now considering. The presence 

 of a small quantity of non-volcanic rock, as of clay-slate 

 on three of the Azores, 2 or of tertiary limestone at 

 Madeira, or of clay-slate at Chatham Island in the 

 Pacific, or of lignite at Kerguelen Land, ought not to 

 exclude such islands or archipelagos, if formed chiefly 

 of erupted matter, from the volcanic class. 



The composition of the numerous islands scattered 

 through the great oceans being with such rare excep- 

 tions volcanic, is evidently an extension of that law, 

 and the effect of those same causes, whether chemical 

 or mechanical, from which it results, that a vast majority 

 of the volcanos now in action stand either as islands 



1 Judging from Forster's imperfect observation, perhaps Georgia 

 is not volcanic. Dr. Allan is my informant with regard to the 

 iSeychelles. I do not know of what formation Rodriguez, in the 

 Indian Ocean, is composed. 



2 This is stated on the authority of Count V. de Bedemar, with 

 respect to Flores and Graciosa (Charls worth 'Magazine of Nat. Hist.' 

 vol. i. p. 557). St. Maria has no volcanic rock, according to Captain 

 Boyd (Von Buch's ' Descript.' p. 365). Chatham Island has been 

 described by Dr. Dieffenbach,in the ' Geographical Journal,' 1841, p. 

 201. As yet we have received only imperfect notices on Kerguelen 

 Land, from the Antarctic Expedition. 



