VOL. LXXXV,] PHILOSOPHICAL TRANSACTIONS. 493 



eruption of Vesuvius, which destroyed the towns of Herculaneum and Pompeii, 

 and many of the existing printed accounts of its great eruption in l631, might 

 pass for an account of the late eruption by only changing the date, and omitting 

 that circumstance of the retreat of the sea from the coast, which happened in 

 both those great eruptions, and not in this; and I might content myself by 

 referring to those accounts, and observing, that the late eruption, after those 

 two, appears to have been the most violent recorded by history, and infinitely 

 more alarming than either the eruption of 17^7, or that of 1779, "^ both of 

 - which I had the honour of giving a particular account to the r. s. 



The frequent slight eruptions of lava for some years past have issued from near 

 the summit, and ran in small channels in different directions down the flanks of 

 the mountain, and from running in covered channels, had often an appearance 

 as if they came immediately out of the sides of Vesuvius, but such lavas had not 

 sufficient force to reach the cultivated parts at the foot of the mountain. In the 

 year 1779, the whole quantity of the lava in fusion having been at once thrown 

 up with violence out of the crater of Vesuvius, and a great part of it falling, 

 and cooling on its cone, added much to the solidity of the walls of this huge 

 natural chimney, if I may be allowed so to call it, and has not of late years al- 

 lowed of a sufficient discharge of lava to calm that fermentation, which by the 

 subterraneous noises heard at times, and by the explosions of scoriae and ashes, 

 was known to exist within the bowels of the volcano; so that the eruptions of 

 late years, before this last, have been simply from the lava having boiled over 

 the crater, the sides being sufficiently strong to confine it, and oblige it to rise 

 and overflow. The mountain had been remarkably quiet for 7 months before 

 its late eruption, nor did the usual smoke issue from its crater, but at times 

 it emitted small clouds of smoke, that floated in the air in the shape of little 

 trees. It was remarked that for some days preceding this eruption a thick vapour 

 was seen to surround the mountain, about a quarter of a mile beneath its crater, 

 and that both the sun and the moon had often an unusual reddish cast. 



The water of the great fountain at Torre del Greco began to decrease some 

 days before the eruption, so that the wheels of a corn-mill, worked by that 

 water, moved very slowly ; it was necessary in all the other wells of the town and 

 its neighbourhood to lengthen the ropes daily, in order to reach the water; 

 and some of the wells became quite dry. Though most of the inhabitants were 

 sensible of this phenomenon, not one of them seems to have suspected the true 

 cause of it. It has been well attested, that 8 days before the eruption, a man 

 and two boys, being in a vineyard above Torre del Greco (and precisely on the 

 spot where one of the new mouths opened, from whence the principal current 

 of lava that destroyed the town issued), were much alarmed by a sudden puff of 

 smoke that came out of the earth close to them, and was attended with a slight 



