340 Volcanic Electricity. [Book VI. 



without any interruption, our author concluded that 

 at Naples all danger from earthquakes, which had 

 been his greateft apprehenfion, was totally removed, 

 and he returned to his former ftation at St. Lucia at 

 Naples. 



All this time there was not the fmallefl appearance 

 of fire or fmoke from the crater on the fummit of 

 Vefuvius ; but the black fmoke and afhes ifluing con- 

 tinually from fo many new mouths, or craters, formed 

 an enormous and denle body of clouds over the whole 

 mountain, and which began to give figns of being 

 replete with the" electric fluid, by exhibiting flames of 

 that fort of zig-zag lightning, which in the volcanic 

 language of the country is called ferilliy and which is 

 the conftant attendant on the mofl violent eruptions. 



Sir William Hamilton proceeds to remark, that 

 during thirty years that he had refided at Naples, and 

 in which fpace of time he had been witnefs to many 

 eruptions of Vefuvius, of one fort or other, he never 

 faw the cloud of fmoke replete with the electric fire, 

 except in the two great eruptions of 1767, that 

 of 1779, and during this more formidable one. The 

 electric fire, in the year 1779, tnat played conftantly 

 within the enormous black cloud over the crater of 

 Vefuvius, and feldom quitted it, was exactly fimilar 

 to that which is produced, on a very {"mall fcale, by 

 the conductor of an electrical machine communicating 

 with an infulated plate of glafs, thinly fpread over 

 with metallic filings, &c. when the electric chatter con- 

 tinues to play over it in zig-lag lines without quitting 

 it. He was not fenfible of any noife attending that 

 operation in 1779 j whereas the difcharge of the 

 electrical matter from the volcanic clouds during this 

 eruption-, and particularly the fecond and third days, 

 cauitd exploficns l!!:e th^le of the loudefl thunder 4 



and 



