TRUE VOLCANOES. 



365 



not only extremely arbitrary, but founded on totally different 

 principles drawn from the number and size, or the complex- 

 ion and descent of the inhabitants, and to commence the enu- 

 meration of the still active volcanoes of the South Sea with 

 those which lie to the north of the equator. I shall after- 

 ward proceed in the direction from east to west, to the isl- 

 ands situated between the equator and the parallel of 30 

 south latitude. The numerous basaltic and trachytic islands, 

 with their countless craters, formerly at different times erup- 

 tive, must on no account be said to be indiscriminately scat- 

 tered.* It is admitted, with respect to the greater number 

 of them, that their upheaval has taken place on widely ex- 

 tended fissures and submarine mountain chains, which run in 

 directions governed by fixed laws of region and grouping, and 

 which, just as we see in the continental mountain chains of 

 Central Asia, and of the Caucasus, belong to different sys- 

 tems; but the circumstances which govern the area over 

 which at any one particular time the openings are simultane- 

 ously active, probably depend, from the extremely limited 

 number of such openings, on entirely local disturbances, to 

 which the conducting fissures are subjected. The attempt to 

 draw lines through three now simultaneous volcanoes, whose 

 respective distances amount to between 2400 and 3000 geo- 

 graphical miles asunder, without any intervening cases of 

 eruption (I refer to three volcanoes now in a state of ignition 







* " The epithet scattered, as applied to the islands of the ocean (in 

 the arrangement of the groups), conveys a very incorrect idea of their 

 positions. %here is a system in their arrangement as regular as in the 

 mountain heights of a continent, and ranges of elevation are indicated 

 as grand and extensive as any continent presents." Geology, by J. 

 Dana, United States Exploring Expedition, under command of Charles 

 Wilkes, vol. x. (1849), p. 12. Dana calculates that there are in the 

 whole of the South Sea, exclusive of the small rock islands, about 350 

 basaltic or trachytic and 290 coral islands. He divides them into 

 twenty-five groups, of which nineteen in the centre have the direction 

 of their axis N. 50 60 W., and the remaining N. 20 30 E. It 

 is particularly remarkable that these numerous islands, with a few ex- 

 ceptions, such as the Sandwich Islands and New Zealand, all lie be- 

 tween 23 28" of north and 'south latitude, and that there is such an 

 immense space devoid of islands eastward from the Sandwich and the 

 Nukahiva groups as far as the American shores of Mexico and Peru. 

 Dana likewise draws attention to a circumstance which forms a con- 

 trast to the insignificant number of the now active volcanoes, namely, 

 that if, as is probable, the Coral Islands, when lying between entirely 

 basaltic islands, have likewise a basaltic foundation, the number of 

 submarine and subaerial volcanic openings may be estimated at more 

 than a thousand (p. 17 and 24). 



