Balancing a heavy body with oblique cords; a man-powered mill
Two unequal weights (5 and 6) and the obliquity of their cords; the best one-man mill
The upper problem asks how to hold a heavy body n m o p in place with two unequal weights (5 and 6) attached at n m, pulling oppositely, and how the obliquity of their cords must be set so the body is neither moved nor bent (text 2). It works the equilibrium with cords h n and m k, the pole o, and the 'spiritual levers' r p and n o, and adds a practical rule that a mill wheel should be started without grain and fed only once it has momentum. A lower note describes mill spindles that can turn backward (text 3), and the last paragraph praises the best mill one man can work: his whole weight rests on the lever f or g while he also pushes or pulls a fixed cord (text 5).
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Two unequal weights (5 and 6) holding a heavy body n m o p
Two unequal weights, one of 5 and one of 6, are hung at n m and pull oppositely so the heavy body n m o p is neither displaced nor bent; the question is how the obliquity of the cords must be set. Given equal 5-pound counterweights on cords h n and m k, the body bends toward h until o is its pole, the perpendicular dividing two unequal parts in the proportion of the spiritual levers r p and n o, and rests once equality is reached.
The best mill one man can work (levers f, g)
This mill is called the best a single man can operate, because the man's whole weight rests on the lever f or g. Beyond that he adds force by pushing the floor with shoulders or hands, or pulling a cord fixed to the pavement below, so he applies part of his force and all his simple weight — impossible at other mills.
Mill spindles that can turn backward
A short caption beside the small figure at lower left notes mill spindles (roche) able to turn backward. It keys the second small mill sketch on the page.