Note 30 — LETTER V.

Scipione Falcone, a very good observer, in his Discorso naturale delli cause et effetti del Vesuvio, says, that he saw, after the eruption of Vesuvius in 1631 (which was attended with hot water), the mud harden almost to a stone in a few days; his words are these—"fatta dura a modo di calcina e di pietra non altrimenti di cenere, perché dopò alcuni giorni vi ci e caminato per sopra e si e conosciuta durissima che ci vogliono li picconi per romperla." This account, with other circumstances mentioned in this letter, make it highly probable, that all the tufas in the neighbourhood of Vesuvius have been formed by a like operation.