[15] I have since found in this stratum of erupted matter at Pompeii, stones weighing eight pounds: but many accounts of the great eruption of Vesuvius, particularly that of Antonio Bulifon, mention that a stone like a bomb was thrown from the crater of Vesuvius in 1631; and fell upon the Marquis of Lauro's house at Nola, which it set on fire. As Nola is twelve miles from Vesuvius, this circumstance seems rather extraordinary: however, I have seen stones of an enormous size shot up to a very great height by Mount Vesuvius. In May 1771, having a stop watch in my hand, I observed that one of these stones was eleven seconds falling from its greatest height, into the crater from whence it had been ejected. In 1767, a solid stone, measuring twelve feet in height, and forty-five in circumference, was thrown a quarter of a mile from the crater; the eruption of 1767, though by much the most violent of this century, was, comparatively to those of the year 79 and 1631, very mild. [16] See Letter V. in this collection. [17] It is the common received opinion, that this mountain rose from the bottom of the Lucrine lake. I had not seen the very curious and particular account of its formation (which account is in my next letter) when I wrote this, and was therefore in the same error. [18] This must depend greatly upon the quality of the lava's; some have been in a more perfect state of vitrification than others, and are consequently less liable to the impressions of time. I have often observed on Mount Vesuvius, when I have been close to the mouth from whence a lava was disgorging itself, that the quality of it varied greatly from time to time: I have seen it as fluid and coherent as glass when in fusion: and I have seen it farinacious, the particles separating as they forced their way out, just like meal coming from under the grindstones. A stream of lava of this sort, being less compact, and continuing more earthy particles, would certainly be much sooner fit for vegetation, than one composed of the more perfect vitrified matter. [19] This earthquake happened in the year 1693, and destroyed forty-nine towns and villages, nine hundred and twenty-two churches, colleges, and convents; and near one hundred thousand persons were buried in their ruin. [20] It is intituled, "A true and exact relation of the late prodigious earthquake and eruption of Mount AEtna, or Monte Gibello; as it came in a letter written to his Majesty from Naples, by the Right Honourable the Earl of Winchelsea, his Majesty's late Embassador at Constantinople, who, in his return from thence, visiting Catania in the island of Sicily, was an eye-witness of that dreadful spectacle; together with a more particular narrative of the same, as it is collected out of the several relations sent from Catania; published by authority. Printed by T. Newcomb, in the Savoy, 1669."