CALORIFICATION. 373 



the shock took place, the water in the wells had 

 considerably diminished, some requiring ropes 

 of great length to reach the water, and in others 

 the water totally disappearing. About eleven 

 o'clock at night, the 12th of June, 1793, Sir 

 William says, "atNaples, we were sensible of a 

 violent shock of an earthquake which lasted 

 nearly half a minute ; it was more particularly 

 felt by the inhabitants of mount Vesuvius, who 

 all agree that the shock was from the bottom 

 upwards, after which an undulatory motion 

 was felt arising from the east and spreading 

 towards the west, and which extended upwards 

 of 30 miles from Naples. On the 15th of June, 

 soon after ten at night, another shock was felt, 

 but neither so long nor so violent as the former 

 one ; at the same moment, a fountain of fire, 

 attended with a very black smoke, and a loud 

 report, was seen to issue and arise to a great 

 height from out the middle of the cone of Vesu- 

 vius. Soon after, another of the same kind 

 broke out at some little distance lower down, 

 as I suppose, by the blowing up of a covered 

 channel full of red hot lava. Fresh fountains 

 of fire succeeded one another hastily, and all in 

 a direct line, tending for about a mile and a 

 half towards the town of Torre del Greco. 1 

 could count fifteen of these, although I believe 

 there were many more, but which were obscur- 

 ed by the smoke : it seems probable that all 



