No. YL^Disirict of the Bay ofBaJa. 81 



must have disfigured most of the craters of the Campi Phle- 

 graei with the exception of a very few, if any others really 

 existed. Its component parts are scoriform and disjointed, the 

 greater part being pumiceous, like the neighbouring eminences, 

 but containing less intermixture of felspar. The pumice is 

 also blacker and heavier. The ejected masses are of an ash- 

 gray colour, sometimes trachytic, and often schistose, resem- 

 bling clinkstone. Mr Scrope mentions some specimens of this 

 rock veined with pitchstone, into which it passes, and also into 

 pumice, the three varieties alternating in a remarkable man- 

 ner.* Sir William Hamilton describes and figures a vein or 

 bed of lava of which a section is seen in the interior of the 

 crater ; but its real nature requires more particular examina- 

 tion. It is said to have been ejected on the seventh day of the 

 eruption, and to have caused the death of about twenty people 

 on the hill, to ♦which we have already alluded. In the bottom 

 of the crater are several caverns which contain alkaline efflo- 

 rescences, particularly carbonate of soda, and from one, pure 

 and tasteless water in the form of steam arises. 



The Monte Nuovo is not a solitary example of such volcanic 

 explosions, which in a few days or hours may elevate an en- 

 tire mountain ; and it is very remarkable that all such explo- 

 sions on record have been completely submarine. The effect 

 of them has been the production not merely of a hill, but of 

 an island. It may be instructive to notice briefly the accounts 

 we have received of such phenomena. 



The most remarkable in every way occurs likewise in the 

 Mediterranean. It is the Island of Santorini in the Grecian 

 Archipelago, and its numerous small dependents. The larger 

 mass, which was anciently called Thera, and now Santorini, 

 according to the account of Pliny, was itself raised from the 

 bed of the sea ; and from its structure and appearance it 

 seems extremely probable that it was so at an early period, 

 though the Roman naturalist has mixed his narrative with 

 some inconsistent details. In form it much resembles the 

 Island of Nisida near Naples, already described, having a har- 

 bour of great depth at one side perfectly resembUng a crater, 

 communicating at one side with the sea. The whole structure 



* Geological Transactions, N. S. vol. ii. 

 NEW SERIES. VOL. II. NO. I. JAN. 1830. F 



