Tufa from Mount Vesuvius, c 1770.
© Science Museum / Science & Society Picture Library
Hand-coloured etching by Peter Fabris (active 1768-1779). Illustrated plate from William Hamilton's study of Italian volcanoes, 'Campi Phlegraei' (published in Naples, 1776). Tufa from Mount Vesuvius, showing (1) tufa attached to painted stucco from the theatre of Herculaneum, Pompeii, and other tufa fragments embedded with (2, 7) wood, (3, 4, 6) shells and (5) lava. Tufa is a mixture of ashes and pumice stones thrown up by volcanoes in liquid mud form.Hamilton's book is a seminal work on the nature and effects of volcanic activity.