I'HILOSOPHICAL TRANSACTIONS. [aNNO 1780. 



which he instantly put in execution, and with so little difficulty, that they 

 followed him without hesitation, having felt no other inconveniency than what 

 proceeded from the violence of the heat on their legs and feet; the crust of the 

 lava was so tough, besides being loaded with cinders and scoriae, that their 

 weight made not the least impression on it, and its motion was so slow, that 

 they were not in any danger of losing their balance and falling on it. Having 

 thus got rid of the troublesome heat and smoke, they coasted the river of lava 

 and its channels up to its very source, within a quarter of a mile of the crater. 

 The liquid and red-hot matter bubbleil up violently, with a hissing and crackling 

 noise, like that which attends the playing off of an artificial firework, and by 

 the continual splashing up of the vitrified matter, a kind of arch or dome was 

 formed over the crevice from which the lava issued. It was cracked in many parts, 

 and appeared red-hot within, like a heated oven: this hollowed hillock might 

 be about 15 feet high, and the lava that ran from under it was received into a 

 regular channel, raised on a sort of wall of scoriae and cinders, almost perpendi- 

 cularly, of about the height of 8 or lO feet, resembling much an ancient aque- 

 duct. They then went up to the crater of the volcano, in which they found, 

 as usual, a little mountain throwing scoriae and red-hot matter with loud 

 explosions; but the smoke and smell of sulphur was so intolerable, that they 

 were under the necessity of quilting that curious spot with the utmost 

 precipitation. 



After this slight sketch of the most remarkable events on Vesuvius since the 

 year 1767, Sir W. comes to the account of the late eruption, which affords 

 indeed ample matter for curious speculation. The usual symptoms of an 

 approaching eruption, such as rumbling noises and explosions within the bowels 

 of the volcano, a quantity of smoke issuing with force from its crater, accom- 

 panied at times with an emission of red-hot scoriae and ashes, were manifest, 

 more or less, during the whole month of July; and towards the end of the 

 month, those symptoms were increased to such a degree, as to exhibit in the 

 night-time the most beautiful fire-works that can be imagined. These kinds of 

 throws of red-hot scoriae and other volcanic matter, which at night are so bright 

 and luminous, appear in broad day-light like so many black spots in the midst 

 of the white smoke; and it is this circumstance that occasions the vulgar and 

 false supposition, that volcanoes burn much more violently at night than in the 

 day-time. 



On the 5th of August, about 2 o'clock in the afternoon, Sir W. perceived, 

 from his villa at Pausilipo in the bay of Naples, whence he had a full view ot 

 Vesuvius, which is just opposite, and at the distance of about 6 miles in a direct 

 line from it, that tlie volcano was in a most violent agitation: a white and 

 ^sulphureous smoke issued continually and impetuously from its crater, one pufF 



