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Codex Madrid II — f 73v-f 74r

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Biblioteca Nacional de España, Madrid

(dall'alto in basso:)

Per fare pietre miste come diasspro.

Tolli chiara e vetro pesto e porcellette minute, e nero di fumo. E mista ogni cosa insieme, e llasscia secare al sole o vento. E poi pulissci con olio di lino, a sstrumento da conciare, con issmeriglio minuto e polissci col tripoli.

Togliesi il vetro, acciò lo ssmeriglio193 non consumi l'intervalli delle chiocciole. A[n]cora sare[be] bono scaglia di ferro pessta 'n isscanbio di vetro.

Ancora se ttu togli vari colori misti con chiara e riducili a ssimilitudine di passta. E poi mista insieme, rimenando e ragirandole insieme con varie revolitioni, tu farai una mistura a uso d'agatis. E massime mistandole poi insieme con chiara senplice. E poi fa bollire ogni cosa nela cassetta, over teglia, ove tu tal materia conponi. E pulita194 che è, vernicia 4 o 5 volte di vernice d'anbra. In tal mistione sia tolto pezetti della medesima misstura rossa e ttrita e sseminata infra lla chiara e poi195 bollita e sseca, e ssarà fissa e ttrassparente.

Ancora sia fatto nugoli di minio infra lla chiara fresca, e minuti grani seminati infra essa chiara196.

[Continuazione delle dimostrazioni del fol. 74 recto. Separato dal testo superiore con una linea orizzontale e segno di rimando in basso a destra.]

Per la prima di sopra, e c L K è equale in quantità al h c n K, onde io leverò il triangolo ortogonio h m n del suo sito, e renderollo in c p K, e arò fatto un paralello rettangulo, equale e ssimile al paralello a b c d. E che sia simile ed equale l'uno all'altro, io lo provo per la difinition del cerchio. I' lato c h è equale al lato c a, perché l'una e ll'altro lato son197 semidiamitri d'un medesimo cerchio, e lla linia p m è equale alla linia c h, perché a cquella è paralella e congiunta da congiuntione rettangula, dalle 2 linie equali c p h m. La qual superficie è equale al h c n p, per la concetione che dice: chi rende quel che gli fu tolto, ritorna nel primo grado. Io tolsi il triangolo h m n alla superfitie h c n p e lielo rendei in c p

(from top to bottom:)

To make composite stones like jasper.

Take egg white and ground glass and tiny [ground] shells, and lampblack. And mix everything together, and let it dry in the sun or wind. And then polish with linseed oil, using a dressing tool, with fine emery, and polish it with tripoli.

The glass is taken so that the emery does not wear away the interstices of the whorls. It would also be good to use ground iron scale instead of glass.

Also, if you take various colours mixed with egg white and reduce them to the likeness of a paste, and then mix them together, kneading and turning them with various revolutions, you will make a mixture in the manner of agate, and especially by then mixing them together with plain egg white. And then boil everything in the little box, or pan, in which you compose such material. And once it is polished, varnish it 4 or 5 times with amber varnish. Into such a mixture let there be put little pieces of the same red mixture, ground and scattered through the egg white, and then boiled and dried, and it will be fixed and transparent.

Also let there be made little clouds of red lead (minium) through the fresh egg white, and tiny grains scattered through that egg white.

[Continuation of the demonstrations of fol. 74 recto. Separated from the text above by a horizontal line, with a reference mark at the lower right.]

By the first above, e c L K is equal in quantity to h c n K, whence I will remove the right triangle h m n from its place, and render it at c p K, and I will have made a rectangular parallelogram equal and similar to the parallelogram a b c d. And that they are similar and equal to one another I prove by the definition of the circle. The side c h is equal to the side c a, because the one and the other side are semidiameters of the same circle, and the line p m is equal to the line c h, because it is parallel to it and joined by a right-angled junction by the two equal lines c p, h m. Which surface is equal to h c n p, by the conception that says: whoever restores what was taken from him returns to the first degree. I took the triangle h m n from the surface h c n p and rendered it to c p.

Recipe for imitation jasper and agate; a geometrical area proof

Making coloured artificial stone from egg white and ground glass, above a demonstration of equal figures

Ornament & Heraldry Geometry

A full page of text with no diagrams. The upper part is a craft recipe for making composite decorative stones resembling jasper and agate, mixing egg white, ground glass, tiny shells and lampblack, drying the paste, then grinding and polishing it with emery, tripoli and amber varnish; coloured pastes and red-lead 'clouds' are worked in to imitate veined stone. Below a horizontal rule the text resumes a geometrical demonstration carried over from folio 74 recto, proving two parallelograms equal by removing a right triangle h m n and rendering it at c p, justified by the equal semidiameters of a circle.

On this page

How to make composite stones like jasper and agate

Egg white is mixed with ground glass, small ground shells and lampblack, dried in sun or wind, then polished with linseed oil, fine emery and tripoli. Coloured pastes kneaded together in swirls yield an agate-like effect, and little clouds of red lead (minium) scattered in fresh egg white imitate veining; the finished piece is varnished several times with amber varnish to leave it fixed and transparent.

Proving two parallelograms equal by transposing triangle h m n

Continuing a demonstration from folio 74 recto, Leonardo removes the right triangle h m n from its place and renders it at c p K to form a rectangular parallelogram equal and similar to a b c d. Side c h equals side c a as semidiameters of one circle, and line p m equals c h, so the whole is proved equal by the principle that whoever restores what was taken returns to the first state.

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