Proportional compass with adjustable points; screw and frame studies
An instrument of pivots and joints, like pincers, for scaling drawings up or down
The sheet is dominated by a large threaded screw press or jack, a pair of dividers, a triangular timber frame lettered with dimensions of 4, 8 and 3 braccia, and — the subject of the notes — a proportional compass. Leonardo describes an instrument whose points a and b sit in sheaths of adjustable length, so that a drawing may be reduced more or less as one wishes; he calls these 'compasses of proportion' made of pivots and joints in the manner of pincers. Additional mechanical detail on the sheet is not covered by the transcription.
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Proportional compass with sliding point-sheaths
The points a b are set into their sheaths at greater or lesser length, according to how much one wishes to reduce the thing being drawn. Leonardo names them 'compasses of proportion', made of pivots and joints in the manner of pincers or tongs.
An instrument for scaling the thing you draw
The compass is presented as a drawing aid: by setting its points longer or shorter in their sheaths, the draughtsman diminishes the copied object by as much or as little as desired. It is a tool for enlarging or reducing a design at a fixed ratio.
Timber frame lettered in braccia
Seen with the sheet turned onto its right side, a triangular timber structure is dimensioned 4 braccia, 8 braccia and 3 braccia. A braccio is an arm's-length unit of measure.
Screw press and pair of dividers
A large threaded screw within a heavy block — a press or jack — is drawn in the shaded centre of the sheet, and a pair of open dividers or compasses stands at the right. These mechanical studies are not part of the transcription.