If it were allowed to make a comparison between the earth and a human body, one might consider a country replete with combustibles occasioning explosions (which is surely the case here) to be like a body full of humours. When these humours concentre in one part, and form a great tumour out of which they are discharged freely, the body is less agitated; but when, by any accident, the humours are checked, and do not find free passage through their usual channel, the body is agitated, and tumours appear in other parts of that body, but soon after the humours return again to their former channel. In a similar manner one may conceive Vesuvius to be the present great channel, through which nature discharges some of the foul humours of the earth: when these humours are checked by any accident or stoppage in this channel for any considerable time, earthquakes will be frequent in its neighbourhood, and explosions may be apprehended even at some distance from it. This was the case in the year 1538, Vesuvius having been quiet for near 400 years. There was no eruption from its great crater, from the year 1139 to the great eruption of 1631, and the top of the mountain began to lose all signs of fire. As it is not foreign to my purpose, and will serve to shew how greatly they are mistaken, who place the seat of the fire in the centre, or towards the top, of a Volcano; I will give you a curious description of the state of the crater of Vesuvius, after having been free from eruption 492 years, as related by Bracini, who descended into it not long before the eruption of 1631: "The crater was five miles in circumference, and about a thousand paces deep; its sides were covered with brush wood, and at the bottom there was a plain on which cattle grazed. In the woody parts, boars frequently harboured; in the midst of the plain, within the crater, was a narrow passage, through which, by a winding path, you could descend about a mile amongst rocks and stones, till you came to another more spacious plain covered with ashes: in this plain were three little pools, placed in a triangular form, one towards the East, of hot water, corrosive and bitter beyond measure; another towards the West, of water salter than that of the sea; the third of hot water, that had no particular taste."