To contrive a self-trimming lamp.
Let A B C (fig. 33), be a lamp
through the mouth of which is inserted an iron bar, D E, capable of
sliding freely about the point E, and let the wick be wound loosely
about the bar. Place near a toothed wheel F, moving freely about an
axis, its teeth in contact with the iron bar, that, as the wheel
revolves, the wick may be pushed on by means of the teeth. Let the
opening for the oil be of considerable width, and when the oil is poured
in let a small basin float upon it, G, to which is attached a
perpendicular toothed bar, H, the teeth of which fit into the teeth of
the wheel. It will be found that, as the oil is consumed, the basin
sinks and causes the wheel F to revolve by means of the teeth of the
bar, and thus the wick is pushed on.