VOL. LXXVI.] PHILOSOPHICAL TRANSACTIONS. 131 



XFIII. Some Particulars of the present State of Mount Fesuvius ; with the 

 Account of a Journey into the Province of Abruzzo, and a Voyage to the 

 Island of Ponza. By Sir fVilliam Hamiltony K. B., F. R. S., and A. S, 

 Dated, Naples, January 24, 1786. 



The eruption of Mount Vesuvius, which began in November, 1784, con- 

 tinued in some degree till about the 20th of last month. The lava either over- 

 flowed the rim of the crater, or issued from small fissures on its borders, on 

 that side which faces the mountain of Somma, and ran more or less in 1, 

 and at times in 3 or 4 channels, regularly formed, down the flanks of the conical 

 part of the volcano ; sometimes descending and spreading itself in the valley 

 between the two mountains ; and once, when the eruption was in its greatest 

 force, in the month of November last, the lava descended still lower, and did 

 some damage to the vineyards, and cultivated parts at the foot of Vesuvius, 

 towards the village of St. Sebastiano ; but generally the lava not being abundant, 

 stopped and cooled before it was able to reach the valley. By the accumulation 

 of these lavas on the flanks of Vesuvius, its form has been greatly altered ; and 

 by the frequent explosion of scoriae and ashes, a considerable mountain has been 

 formed within the crater, which now rising much above its rim has also given 

 that part of the mountain a new appearance. 



Sir W. having never had an opportunity of examining the islands of Ponza, 

 Palmarole, Zannone, and other small islands, or rather rocks, situated between 

 the island of Ventotiene and Monte Circello, near Terracina, on the Continent; 

 and thinking that by a tour of these islands, he should be enabled to render 

 his former observations more complete, he determined to take a favourable op- 

 portunity to visit these islands. But before putting this plan in execution, he made a 

 long excursion in the province of Abruzzo, as far as the Lake of Celano, anciently 

 called Fucinus, and where the famous Emissary of the Emperor Claudius, a most 

 stupendous work for drainingthat lake, remains nearly entire, though filled up with 

 rubbish and earth in many parts, and of course useless. The water of this lake, 

 which is more than 30 miles in circumference, increases daily, and is destroying the 

 rich and cultivated plains on its borders. It is surrounded by very high moun- 

 tains, many of them covered with snow, and at the foot of them are many 

 villages, and rich and well cultivated farms. He went with torches into the Emis- 

 sary of Claudius as far as he could. It is a covered under-ground canal, 3 miles 

 long, and great part of it cut through a hard rock ; the other parts supported by 

 masonry, with wells sunk to give air and light. According to Suetonius, 

 Claudius employed 30 thousand men eleven years on this great work, intended 

 to convey the superfluous water of the lake into the bed of the river Liris, now 

 called Garigliano ; and no doubt, if it was cleared and repaired, it would again 



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