Portuguese table cannon sun dial, mid 19th century

These dials has been very popular since the 18th century, combined with a cannon and a burning glass, is set so that when the sun reaches its highest point at noon, a charge of gunpowder is ignited by the bundled rays of the sun, so that a loud bang sounds.

Huge examples were palced in Dockyards and Arsenals to signal noon and lunchtime.