[6] From what I have seen and read of eruptions of Vesuvius and Etna, I am convinced that Volcano's lie dormant for several years, nay even for centuries, as probably was the case of Vesuvius before its eruption in the reign of Titus, and certainly was so before that of the year 1631. When I arrived at Naples in 1764, Vesuvius was quiet, very seldom smoak was visible on its top; in the year 1766, it seemed to take fire, and has never since been three months without either throwing up red hot stones, or disgorging streams of lava, nor has its crater been ever free from smoak. At Naples, when a lava appears, and not till then, it is styled an eruption; whereas I look upon the five nominal eruptions I have been witness to, from March 1766 to May 1771, as, in effect, but one continued eruption. [7] It is certain, that, by constant attention to the smoak that issues from the crater, a very good guess may be given as to the degree of fermentation within the Volcano. By this alone I foretold[47] the two last eruptions, and, by another very simple observation, I pointed out, some time before, the very spot from whence the lava has issued. When the cone of Vesuvius was covered with snow, I had remarked a spot on which it would not lie: concluding very naturally that this was the weakest part of the cone, and that the heat from within prevented the snow from lying; it was as natural to imagine that the lava, seeking a vent, would force this passage sooner than another; and so indeed it came to pass. [8] These are his words: "Nubes (incertum procul intuentibus ex quo monte Vesuvium fuisse postea cognitum est) oriebatur, cujus similitudinem & formam, non alia magis arbor, quam pinus expresserit. Nam longissimo veluti trunco elata in altum, quibusdam ramis diffundebatur, credo quia recenti spiritu evecta, dein senescente eo destituta, aut etiam pondere suo victa, in latitudinem evanescebat: candida interdum, interdum sordida & maculosa, prout terram cineremve sustulerat." Plin. lib. vi. ep. 16. [9] The windows at Naples open like folding-doors.