404 FHILOSOPHICAL TRANSACTIONS. [aNNO 1 768. 



/. On the Eruption of Mount Fesuvius, in 17^7 • By the Hon. fVm. Hamilton. 

 Dated Naples, Dec. 2Q, 1767. Fol. LFIII. j4n. 1768. p, 1. 

 The late violent eruption began Oct. 19, 1767, and is reckoned to be the 

 27 th since that which, in the time of Titus, destroyed Herculaneum and Pompeii. 

 The eruption of 1766 continued in some degree till the J 0th of Dec. about 9 

 months in all, yet in that space of time the mountain did not cast up a 3d part 

 so much as the quantity of lava which it disgorged in only 7 days, the term of 

 this last eruption. On the 15th of December, last year, within the ancient 

 crater of Mount Vesuvius, and about 20 feet deep, there was a crust, which 

 formed a plain, not unlike the solfaterra in miniature ; in the midst of this plain 

 was a little mountain, whose top did not rise so high as the rim of the ancient 

 crater. Vesuvius was quiet till March J 767, when it began to throw up stones, 

 from time to time ; in April the throws were more frequent, and at night fire was 

 visible on the top of the mountain ; or, more properly speaking, the smoke, 

 which hung over the crater, was tinged by the reflection of the fire within the 

 volcano. These repeated throws of cinders, ashes, and pumice stones, increased 

 the little mountain so much, that in May its top was visible above the rim of 

 the ancient crater. The 7th of August there issued a small stream of lava, from 

 a breach in the side of this little mountain, which gradually filled the valley be- 

 tween it and the ancient crater; so that the 12th of September the lava over- 

 flowed the ancient crater, and took its course down the sides of the great moun- 

 tain ; by this time, the throws were much more frequent, and the red hot stones 

 went so high as to take up 10 seconds in their fall. Padre Torre, a great ob- 

 server of Mount Vesuvius, says they went up above 1000 feet. 



The lava continued to run over the ancient crater in small streams, sometimes 

 on one side, and sometimes on another, till the 18th of October, when there 

 was not the least lava to be seen, owing probably to its being employed in forcing 

 its way towards the place where it burst out the following day. Sir W. was not 

 surprised on the IQth following, at 7 in the morning, to perceive every symptom 

 of the eruption being just at hand. From the top of the little mountain issued 

 a thick black smoke, so thick that it seemed to have difficulty in forcing its way 

 out ; cloud after cloud mounted with a hasty spiral motion, and every minute a 

 volley of great stones were shot up to an immense height in the midst of these 

 clouds ; by degrees, the smoke took the exact shape of a huge pine tree, such 

 as Pliny the younger described in his letter to Tacitus, where he gives an ac- 

 count of the fatal eruption in which his uncle perished. This column of black 

 smoke, after having mounted an extraordinary height, bent with the wind 

 towards Caprea, and actually reached over that island, which is not less than 28 

 miles from Vesuvius. 



