Self-Feeding Oil Lamp; Division of a Pyramid
A float-and-gear lamp that raises its wick as the oil sinks, with a pyramid cut parallel to its base
Leonardo designs an oil lamp that keeps its flame steady: as the oil level falls, the wick automatically rises. A wheel resting on the oil sinks with it, unwinding a cord about its pole and turning; the wheel's teeth then drive a toothed rod that carries the wick upward. A variant works from a float b riding on the oil surface, and two further analogous figures are shown. In the lower part of the sheet, three figures treat the geometry of a pyramid cut by a plane parallel to its base, dividing it at seven-eighths of its quantity.
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Oil lamp that raises its wick as the oil sinks
A wheel supported on the oil descends as the oil diminishes, turning upon itself by a cord that unwinds around its pole; its teeth push the toothed rod holding the wick, so the wick rises exactly as much as the oil falls.
Float-driven variant of the self-feeding lamp (a, b)
The same effect occurs even if the pole a of the wheel does not descend but only the float b, riding on the oil, sinks with the surface. The float turns the wheel, which with slow motion pushes the toothed rod upward.
A pyramid cut parallel to its base yields seven-eighths
A pyramid divided through its height by a cut equally distant from its base is divided at seven-eighths of its quantity. This is proved because the whole splits into 12 pyramids, of which 8 compose the body of eight bases, worth the 4 larger pyramids.