Note 12 — LETTER II.

In all accounts of great eruptions of Mount Etna and Mount Vesuvius, I have found mention of this sort of lightning. Pliny the younger, in his second letter to Tacitus upon the eruption of Vesuvius in the time of Titus, says, that a black and horrible cloud covered them at Misenum (which is above fifteen miles from the Volcano), and that flashes of zig-zag fire, like lightning, but stronger, burst from it; these are his words: "ab altero latere nubes atra et horrenda ignei spiritus tortis vibratisque discursibus rupta, in longas flammarum figuras dehiscebat; fulgoribus illæ et similes et majores erant." This was evidently the same electrical fire, and with which I am convinced that the smoak of all Volcanos is pregnant. In several accounts of the great eruption of Vesuvius in 1631, mention is made of damage done by the lightning that issued from the column of smoak. Bulifon, in particular, says, that, in the neighbourhood of the Volcano, people were struck dead in the same manner as if by lightning, without having their cloaths singed. Pliny mentions a like instance, which shews that the ancients had observed this phænomenon; for he says, that at Pompeii, the day being fair, Marcus Herennius was struck dead by lightning. These are his words; "In Catilianis prodigiis, Pompeiano ex municipio M. Herennius Decurio serena die, fulmine ictus est." Plin. Hist. Nat. lib. II. cap. li. The learned and ingenious Father Beccaria, at Turin, assured me, that he had been greatly pleased with my observations on this species of lightning, as coinciding perfectly with several of his electrical experiments.