Screw-and-wheel gearing driven by a water wheel
One wheel-turn drives the screw four turns; 32 teeth to an 8-stave lantern pinion
Two notes work out the gearing between a screw and a wheel turned by water. In the first, one complete turn of the driving wheel makes the screw turn four whole times. The second explains that water should be poured onto one quarter of the wheel, at a n, so its weight acts far from the centre; to make the screw turn once as that quarter completes its course, the wheel is given 32 teeth and each lantern-pinion 8 staves, yielding the four-to-one ratio. The margin carries the figures 8 8 - 8 - 32.
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Gear ratio: screw turns four times per wheel turn
One whole turn of the wheel of the first motion drives the screw through four complete turns, according to the rules that govern such gearing. The note is marked with the figures 8 8 - 8 - 32.
Water delivered onto a quarter of the wheel (a–n)
Water is to be poured over the fourth part of the wheel, shown at a n, so that its weight stays as far as possible from the wheel's centre; when that quarter has run its course, the screw should make one full turn.
32 teeth to an 8-stave lantern pinion
To obtain the intended motion the wheel is toothed with 32 teeth and each lantern-pinion ("rocca") given 8 staves ("fuselli"), which produces the four-to-one relation between wheel and screw.