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Library/Codex Arundel/ff. 21v-24r

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Codex Arundel — ff. 21v-24r

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British Library, London — Arundel MS 263

Modo di mantaci de' fornelli.

Le ventole contrarie son fatte perché quella che apre in fuori, serve a mandare fuori il caldo, e che dopo el moto d'esso caldo egli non possa per nessuna via tornare indirieto. E questo esce per la finestra m, la qual si serra colla ventola b. Il vento fresco è tirato nel mantace per la finestra n, la quale, entrata nel mantace la ventola a, si serra, e mai pò spirare per essa finestra; ma quando è riscaldato, ritorna fori per l'altra finestra m, come prima fu decto.

Il brieve e spesso alitare soffoca quello che alita, perché non si scambia ogni alitatura tutta l'aria che si riscalda nel polmone; ma ve ne resta una parte tanta riscaldata, che darebbe gran nocimento all'animale, se con grande e lungo alitare non fussi sospinta fori di tale polmone.

A kind of bellows for furnaces. The contrary valves are made because the one that opens outward serves to send out the heat, and so that, after the motion of that heat, it cannot by any way return backward. And this goes out through the window m, which is closed by the valve b. The fresh air is drawn into the bellows through the window n, which, once the valve a has entered the bellows, closes, and can never breathe out through that window; but when it is heated, it returns out through the other window m, as was said before. Brief and frequent breathing suffocates the one who breathes, because not every breath exchanges all the air that is heated in the lung; but there remains in it a part so heated that it would do great harm to the animal, if by great and long breathing it were not thrust out of that lung.

Bellows with contrary valves for furnaces

One-way valves a and b at windows n and m, likened to breathing in the lung

Machines & Devices Anatomy

This note describes a bellows for furnaces fitted with 'contrary' valves: the valve opening outward sends the heat out and prevents its return, escaping through window m which the valve b closes, while fresh air is drawn in through window n past valve a and, once heated, leaves again through m. Leonardo then draws a physiological analogy, that brief and frequent panting suffocates because not all the air heated in the lung is exchanged, leaving a hot remnant that would harm the animal unless expelled by deep, long breathing. A small perspective sketch of the furnace-box appears at the upper right.

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Contrary one-way valves a and b

The outward-opening valve sends the heat out through window m, which is then closed by the valve b so the heat cannot return. Fresh air is drawn into the bellows through window n past valve a, which shuts, and the air escapes reheated through window m.

Why brief panting suffocates

Brief, frequent breathing does not exchange all the air heated in the lung, leaving a part so hot that it would greatly harm the animal unless thrust out by deep and long breathing.

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