The Subterranean World

The Subterranean World describes earthquakes as generally accompanied by sounds, sometimes resembling a storm or subterranean thunder, at other times the clashing of iron chains. An account of the great Neapolitan earthquake of 1857 records an unusual halo-like light seen in the sky shortly before the shock. Mr. Mallet initially regarded the report as possibly superstitious, but no longer doubted its factual basis after finding the belief widely diffused where communication was bad and news travelled slowly.

The account of mining describes steam draining the deepest pits and bringing materials to the surface with previously unknown quantity, speed and security. A discussion of furnace machinery describes powerful engines forcing air through small tubes arranged to distribute the blast throughout the heated mass. An explanation of siphon action describes intermittent discharge when a constant water supply enters more slowly than water escapes.