VOL. LXXXV.] PHILOSOPHICAL TRANSACTIONS. 495 



sant reports, like those from a numerous heavy artillery, accompanied by a con- 

 tinued hollow murmur, like that of the roaring of the ocean during a violent 

 storm; and added to these was another blowing noise, like that of the going up 

 of a large flight of sky-rockets, and which brought to my mind also that noise 

 which is produced by the action of the enormous bellows on the furnace of the 

 Carron iron foundery in Scotland, and which it perfectly resembled. The fre- 

 quent falling of the huge stones and scoriae, which were thrown up to an incre- 

 dible height from some of the new mouths, and one of which, having been since 

 measured, was 10 feet high, and 35 in circumference, contributed undoubtedly 

 to the concussion of the earth and air, which kept all the houses at Naples for 

 several hours in a constant tremor, every door and window shaking and rattling 

 incessantly, and the bells ringing. The sky, from a bright full moon and star- 

 light, began to be obscured; the moon had presently the appearance of being 

 in an eclipse, and soon after was totally lost in obscurity. After some time, and 

 which was about 2 o'clock in the morning of the l6th, the lavas ran in abun- 

 dance, freely and with great velocity, having made a considerable progress to- 

 wards Resina, the town which it first threatened, and the tiery vapours which 

 had been confined had now free vent, through many parts of a crack of more 

 than a mile and a half in length, as was evident from the quantity of inflamed 

 matter and black smoke, which continued to issue from the new mouths above- 

 mentioned without any interruption. 



All this time there was not the smallest appearance of fire or smoke from the 

 crater on the summit of Vesuvius; but the black smoke and ashes issuing conti- 

 nually from so many new mouths, or craters, formed an enormous and dense 

 body of clouds over the whole mountain, and which began to give signs of being 

 replete with the electric fluid, by exhibiting flashes of that sort of zig-zag light- 

 ning, which in the volcanic language of this country is called ferilli, and which 

 is the constant attendant on the most violent eruptions. During 30 years that 

 I have resided at Naples, and in which time I have been witness to many erup- 

 tions of Vesuvius, of different sorts, I never saw the gigantic cloud above-men- 

 tioned replete with the electric fire, except in the 2 great eruptions of 1767, 

 that of 1779, and during this more formidable one. The electric fire, in the 

 year 1779, that played constantly within the enormous black cloud over the crater 

 of Vesuvius, and seldom quitted it, was exactly similar to that which is produced, 

 on a very small scale, by the conductor of an electrical machine communicating 

 with an insulated plate of glass, thinly spread over with metallic filings, &c. when 

 the electric matter continues to play over it in zig-zag lines without quitting it. 

 I was not sensible of any noise attending that operation in 1779; whereas the 

 discharge of the electrical matter from the volcanic clouds during this eruption, 

 and particularly on the 2d and 3d days, caused explosions like those of the 



