Engraving: As a toothed wheel, moving freely about an axis, with its teeth in contact with an iron bar, revolves, the wick may be pushed on by means of the teeth. A small basin floating on the oil is attached to a perpendicular toothed bar, the teeth of which fit into the teeth of the wheel. As the oil is consumed, the basin sinks and causes the wheel to revolve by means of the teeth of the bar, and thus the wick is pushed on. Illustration from 'Gli artifitiosi et curiosi moti spiritali di Herrone' (commonly called 'Pneumatics') by Hero of Alexandria, published in Ferrara in 1589.
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