The flint mill was invented by Carlisle Spedding, a colliery manager in Cumberland, around the middle of the 18th century. It was designed to provide miners with a safer light than candles in an attempt to avoid setting off explosions.
The flint mill consists of an iron frame containing two shafts geared together. In turning the handle on the end of one shaft, a steel disc on the other is made to spin rapidly. A flint would be held in contact with this spinning wheel creating a shower of sparks.
The flint mill was not popular. It gave off a poor light and was expensive to use, requiring a boy to be employed to operate it while the men worked. It was also not entirely safe, and the sparks it gave off could sometimes ignite explosive 'firedamp' gas. Its use in mines did not last into the 19th century.