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Library/Codex Forster I/004r

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Codex Forster I — 004r

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© Victoria and Albert Museum, London

Figura geometrica ripetuta dalla terza proposizione (f. 39r)

Compasso di proporzione e sua madrevite, con:

p p - d d - c c - b b - a a - n m; h

Per fare un paio di seste da diminuire o crescere una cosa1 da loro misurata con equal proporzione in ciascuna parte.

Serransi a vite con una vite che ha tanto di pulito quanto n'entra nelle seste, e tutto il resto è intagliato a vite. E puossi essa vite transmutare in diversi lochi per la lunghezza de le seste, perché in diversi lochi sono buchi e equalmente distanti dalli stremi di tal seste, nelli quali po entrare la vite come nel mezzo a, nel quarto b, nello ottavo c; e così seg[u]e per tutto e serrasi colla madre h d'essa vite.

Geometric figure repeated from the third proposition (f. 39r)

Proportional compass and its screw-nut, with:

p p - d d - c c - b b - a a - n m; h

To make a pair of compasses for diminishing or enlarging a thing measured by them in equal proportion in each part. They are closed with a screw that has as much smooth part as enters into the compasses, and all the rest is cut as a thread. And this screw can be moved to different places along the length of the compasses, because in different places there are holes equally distant from the ends of these compasses, into which the screw can enter, as in the middle a, at the quarter b, at the eighth c; and so it continues throughout, and it is fastened with the nut h of this screw.

The Proportional Compass and Its Screw-Nut

A scaling instrument, with a geometric figure from proposition 3

Machines & Devices Geometry Arithmetic & Proportion

The page describes a proportional compass, a pair of dividers built to enlarge or reduce any measured thing in equal proportion in every part. Its two legs are closed by a screw whose plain, unthreaded portion just fits the compass while the rest is cut as a thread; the screw can be shifted to holes set at equal distances along the legs (at the middle a, the quarter b, the eighth c) and is fastened by its nut h. At the upper right a geometric figure repeats the third proposition from folio 39r. The drawings show a semicircle, the crossed compass legs, and the small screw device.

On this page

Proportional compass closed by a movable screw

To make a pair of compasses that diminish or enlarge a measured thing in equal proportion in each part. They close with a screw whose polished part fits within the compasses while the rest is threaded; the screw can be moved along the legs to holes equally spaced from the ends (the middle a, the quarter b, the eighth c) and is secured with its nut h.

Geometric figure repeated from proposition 3 (f. 39r)

At the upper right a geometric figure is drawn, captioned as a repetition of the third proposition found on folio 39r. It accompanies the instrument as a reference construction.

Reader's Edition — described with AI from the e-Leo transcription.