252 Mr Forbes's Phijslccd Notices of the Bay of Naples. 



by submarine eruptions. The fact, that the ocean once wash- 

 ed the foot of the Apennines at Capua, since suggested by 

 Scrope, appeared then to me the inevitable conclusion from 

 the state of facts ; and that Vesuvius has gradually raised itself 

 by successive accumulations to its present character, and proud- 

 ly surveys the regions of its own creation, is a simple induc- 

 tion from an attentive view of the physiognomy of the coun- 

 try. The minutiae of those localities under our present re- 

 view, are best calculated to explain plausibly the mode of for- 

 mation, though in this I shall be disposed not to go so far as 

 Breislak has done, and even to dissent somewhat from his doc- 

 trines. This geologist was an indefatigable crater hunter, and 

 he has often strengthened most palpably the features of his 

 maps, to writhe the most gentle and detached rising grounds 

 into portions of the boundaries of vast basins. This is most 

 conspicuous in his Plan Physique de Rome, * as may be seen 

 by comparing it with any good map of the city, where anti- 

 quaries, for the honour of the seven hills, are not usually averse 

 to mark strongly the inequalities of the surface. About 80 

 craters have been put down by Breislak between Naples and 

 the point of Misenum, and he freely acknowledges the strength 

 of imagination necessary to decypher some of them. He even 

 admits the preconceptions which aided him in finding a crater 

 in every group of hills, however large, distant or undefined. 

 But, according to my idea of subaqueous formation, there is 

 no occasion for the number of craters he supposes, and per- 

 haps we should be nearer the truth were we to reduce the num- 

 ber to a dozen. The points of emission of fluid tufa under 

 water would naturally be below the hills formed by it ; the hol- 

 low of a crater is caused by the eruption of the materials which 

 once filled it, into the air, and the emission of streams of lava 

 from its sides ; but this would not be the mode of action un- 

 der the sea. If the volcanic materials were ejected through 

 extended fissures formed by the elastic force beneath, and after- 

 wards modified by the action of the waves, we shall have the 

 exact result which the hill of Pausilipo, for instance, would 

 seem to afford. This will account at once for the varying di- 

 rections and obvious ramifications of the hills which Breislak 



• See Campanie, torn. ii. and Daubeny on Volcanos. 



