Half-Cylindrical, Half-Pyramidal Screws for Perpetual Lifting
A screw shaped part-cylinder, part-pyramid, and one linked to two pumps that Leonardo calls perpetual
Two variants of an Archimedean screw fill the leaf, following a figure like the last on folio 52r. In the first, half cylindrical and then pyramidal, the length d a serves for lifting while a e b serve for increase; b c makes an equidistant lever, and from c to d the water returns to the foot of the screw whence it rises again. The second screw is linked to two pumps, and Leonardo claims that if b c is made greater than a b it will be perpetual, adding that the right-hand screw should have eight turns so that two rise to a.
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Screw part-cylindrical, part-pyramidal (a e b - d c)
A screw made half cylindrical and then pyramidal: d a serves for lifting, while a e b serve for increase. b c forms an equidistant lever, and from c to d the flow returns to the foot of the screw whence it rises again.
Screw coupled to two pumps
A screw like the first but joined to two pumps, labelled a b - a c. Leonardo directs that the right-hand screw be given eight turns so that two rise to a.
A design Leonardo claims to be perpetual
He asserts that if the length b c is made greater than a b this arrangement will be perpetual - a claim of self-sustaining motion typical of this run of studies.