An older mechanical timing device used primarily on beam engines to control the stroke rate. It consists of a small water pump or plunger mechanism where the gradual escape of water through an adjustable valve determines when the steam valves open for the next stroke. By tuning the water flow, operators could set the engine to pause between strokes, matching the pumping rate to the water ingress in a mine.
Heard on the job
Adjust the cataract valve to slow the engine down by a few strokes per minute.