Studies for an Archimedean screw
At the centre of this sheet there is a large conical spiral wheel. According to Carlo Pedretti, this study relates to an Archimedean screw destined for a mill and would be linked to the drawings of augers in folios 1036r, 637r and 550v of the Codex Atlanticus. However, Augusto Marinoni believes it to be the study of a wheel for perpetual motion, a supposition which seems to be confirmed by the drawings below, that recall the perpetual motion mechanism of folio 754r. Marinoni links this sheet to the studies carried out in 1490. In the sheet examined here there is no reference to perpetual motion; and the only mention present in the studies of folio 754 does not concern the study of a machine to empty the ditches, but two possible variations of a small unclear scheme. However, it can be deduced that the underlying theme is nevertheless perpetual motion not so much from the reference to the machine drawn in folio 754r, as from the other devices represented here. The wheel on the left, in fact, reproduces the overbalanced wheels of the 1490s and the studies of the screw, which Leonardo illustrated several times combined in devices for perpetual motion. Regardless of the purpose of these drawings, the most interesting part is the study of the construction of spiral tubes, which makes us understand how Leonardo never lost sight of the possibility of actually making perpetual motion machines. On the left we find, in fact, the sketch of a roller mill, a lathe, a template to shape the copper showers and other devices that are probably a grille to bend the showers and form the spiral duct. It is interesting that Leonardo thinks of making the cochlea with a shower and not with the more traditional closed tube. For its operation, in fact, there is no need for the upper part of the tube, but it is sufficient to have the lower part where the water that rises from one spiral to the next is collected.