128 Physical Notices cfthe Bmj of Naples. 



of a bituminous nature, and contribute very much to unite the 

 whole into a compact mass. It burns on hot coals with no 

 smell of sulphur, but a cerulean flame. When thrown in 

 powder into hot water, a small quantity of aluminous matter 

 is dissolved. 



From a combination of all the circumstances, T should be 

 disposed to believe, that the catastrophe by which Hercula- 

 neum was overwhelmed took place in the following manner. 

 I have elsewhere given it as my opinion, * that the alteration 

 in the point of ejection of the volcanic materials, which is ge- 

 nerally agreed to have taken place in the year 79, was owing 

 to a peculiar tendency of action towards the sea, by which the 

 wall of the crater of the Monte Somma was totally overthrown 

 in that direction, and its debris formed the plain from which 

 the present cone of Vesuvius rises. As it is also admitted 

 that no siliceous lava has flowed in the memory of man till 

 near 1000 years later, we suppose the vast basin of the origi- 

 nal crater filled with the materials fitted for the production of 

 an eruption of mud, — a phenomenon no less naturally to be 

 looked for from the action of the sea-water introduced into the 

 seat of volcanic agency, than established by decisive evidence, 

 more especially on the volcanos of South America. The fall 

 of the southern wall of the crater would bring the whole fiery 

 deluge in the direction of the sea, and, without doubt, the in- 

 terment of Herculaneum was only a portion of the ravages it 

 produced. During the time of this torrent flowing, which 

 probably took place from a lateral rupture, there is every rea- 

 son to believe that another mouth of the volcano ejected the 

 ashes which covered the country for so many miles, and which, 

 we have already seen, divided the mass of tufa into layers. 



Brocchi, in his *' Suoh di Roma,'' -f in illustration of a par- 

 ticular theory of the production of tufas, alludes to Hercula- 

 neum, and the substances formed by modern volcanos. His 

 wish to generalize too much has led him beyond the limits of 

 probability. He says, that among the productions of modern 

 volcanos in full formation, although we have scoria, ashes, poz- 



• See last Number, p. 193. T 8vo, Roraa, 1820. Page 194. 



