An early mechanical device used to provide light in coal mines before the invention of the safety lamp. It consisted of a steel disk rotated rapidly against a piece of flint to produce a continuous shower of sparks. Miners relied on this dim illumination because the sparks were believed to be less likely to ignite explosive firedamp than an open candle flame, though it was still highly dangerous.
Heard on the job
The museum has an old flint mill that a boy would have to crank continuously just so the hewers could see the coal face.
Insider tip
The device was notoriously exhausting to operate and frequently caused the very explosions it was meant to prevent.