Lava from Mount Vesuvius, c 1770.

Hand-coloured etching by Peter Fabris (active 1768-1779), after his own drawing carried out under Hamilton's directions. Illustrated plate from William Hamilton's study of Italian volcanoes, 'Campi Phlegraei' (published in Naples, 1776). Specimens of lava found in the crater of Mount Vesuvius. Based on letters to the Royal Society, Hamilton's book was a more precise study of the nature and effects of volcanic activity than had previously existed, illustrating his claim that volcanoes are creative natural forces.