VOL. LXX.] - PHILOSOPHICAL TRANSACTIONS. 6l5 



impelling another, and by an accumulation of those, clouds of smoke resembling 

 bales of the whitest cotton. Such a mass of them was soon piled over the top 

 of the volcano as exceeded the height and size of the mountain itself at least 4 

 times. In the midst of this very white smoke, an immense quantity of stones, 

 scoriae, and ashes, were shot up to a wonderful height, certainly not less than 

 2000 feet. He could also perceive, by the help of an excellent refracting 

 telescope, at times, a quantity of liquid lava, seemingly very weighty, just 

 heaved up high enough to clear the rim of the crater, and then take its 

 course impetuously down the steep side of Vesuvius, opposite to Somma. 

 Soon after a lava broke out on the same side from about the middle of the 

 conical part of the volcano, and, having run with violence some hours, ceased 

 suddenly, just before it had arrived at the cultivated parts of the mountain above 

 Portici, near 4 miles from the spot where it issued. 



During this day's eruption the heat was intolerable at the towns of Somma 

 and Ottaiano; and was likewise sensibly felt at Palma and Lauro, which are 

 much farther from Vesuvius than the former. Minute ashes, of a reddish hue, 

 fell so thick at Somma and Ottaiano, that they darkened the air in such a 

 manner, as that objects could not be distinguished at the distance of 10 feet. 

 Long filaments of a vitrified matter like spun-glass were mixed and fell with 

 these ashes;* and the sulphureous smoke was so violent, that several birds in 

 cages were suffocated, the leaves of the trees near Somma and Ottaiano were 

 covered with white salts very corrosive. It was generally remarked, that the 

 explosions of the volcano were attended with more noise during this day's erup 

 tion, than in any of the succeeding ones, when probably the mouth of Vesuvius 

 was widened, and the volcanic matter had a freer passage. 



August 6, the fermentation in the mountain was less violent; but about noon 

 there was a loud report, at which time it was supposed, that a portion of the 

 little mountain within the crater had fallen in. At night the throws from the 

 crater increased, and proceeded evidently from 2 separate mouths, which 

 emitting red-hot scoriae, and in different directions, formed a most beautiful and 

 almost continued fire-work. 



August 7, the volcano remained much in the same state; but, about mid- 

 night, its fermentation increased greatly. The 2d fever-fit of the mountain may 

 be said to have manifested itself at this time. Sir W. was watching its motions 

 from the mole of Naples, which has a full view of the volcano, and had been 



» During an eruption of the volcano in the isle of Bourbon in 1766, some miles of country, at 

 the distance of 6 leagues from that volcano, were covered with a flexible, capillary, yellow glass, 

 some of which were 2 or 3 feet long, with small vitrous globules at a little distance one from the 

 other, which perfecUy resembled the filaments of vitrified matter which fell at Ottaiano and in other 

 parts on the borders of Vesuvius during this eruption. — Orig, 



