VOL. LXX.] PHILOSOPHICAL TRANSACTIONS. 617 



which was continually issuing fresh from the crater, formed with it one complete 

 body of fire, which could not be less than 1 miles and a half in breadth, and of 

 the extraordinary height abovementioned, casting a heat to the distance of at 

 least 6 miles around it. The brush wood on the mountain of Somma was soon 

 in a blaze, which flame, being of a different tint from the deep red of the 

 matter thrown out of the volcano, and from the silvery blue of the electrical 

 fire, still added to the contrast of this most extraordinary scene. The black 

 cloud, increasing greatly, once bent towards Naples, and seemed to threaten 

 this fair city with speedy destruction; for it was charged with electric matter, 

 which kept constantly darting about it in strong and bright zig zags, just like 

 those described by Pliny the younger in his letter to Tacitus, and which accom- 

 panied the great eruption of Vesuvius that proved fatal to his uncle. This vol- 

 canic lightning however very rarely quitted the cloud, but usually returned to 

 the great column of fire towards the crater of the volcano whence it originally 

 came. Once or twice indeed, he saw this lightning (or ferilli as it is called here) 

 fall on the top of Somma, and set fire to some dry grass and bushes. 



After the column of fire had continued in full force near half an hour, the 

 eruption ceased all at once, and Vesuvius remained sullen and silent. After the 

 dazzling light of the fiery mountain, all seemed dark and dismal, except the 

 cone of Vesuvius, which was covered with glowing cinders and scoriae, from 

 under which, at times, here and there, small streams of liquid lava escaped, and 

 rolled down the steep sides of the volcano. In the parts of Naples nearest 

 Vesuvius, while the eruption lasted, a mixed smell, like that of sulphur, with 

 the vapours of an iron foundry, was sensible; but nearer to the mountain that 

 smell was very offensive. 



August 9, about 9 o'clock in the morning, the 4th fever-fit of the mountain 

 began to manifest itself by the usual symptoms, such as a subterraneous boiling 

 noise, violent explosions of inflamed matter from the crater of the volcano, 

 accompanied with smoke and ashes, which symptoms increased every instant. 

 The smoke was of two sorts; the one as white as snow, the other as black as 

 jet. The white, as described in the former part of this journal, rolled gently 

 mass over mass, resembling bales of the softest cotton ; and the black, composed 

 of scoriae and minute ashes, shot up with force in the midst of the white smoke, 

 which, from the minerals, was also sometimes tinged with yellow, blue, and 

 green. Presently such a tremendous mass of these accumulated clouds stood 

 over Vesuvius as seemed to threaten Naples again, and actually made the 

 mountain itself appear a mole-hill. This day's eruption was similar to that of 

 the 5th, but many degrees more violent. Some stones, thrown near as high as 

 those of last night, fell on the mountain of Somma, and set fire to the brush 

 wood with which it is covered; but there being little wind, and that westerly, the 



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