Powder Chambers and Ignition Points of Artillery
Three chamber shapes, five firing positions, and the casting of thick bronze barrels.
Leonardo classifies the powder chamber of a gun into three shapes — wide at the base and narrow at the mouth, the reverse, or of uniform width — sketched at the top right as two triangles and a rectangle. He then enumerates the positions at which the charge may be ignited (at the top or middle of the chamber base, at a distance equal to the base radius, at the centre of the powder's thickness, or at the centre of a round chamber). A column of numbered barrels in section (labelled first through seventh) runs down the right margin, and a closing passage warns that thick castings condense poorly because the metal stays liquid longer and the outer parts set first.
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Three shapes of powder chamber
The chamber, or receptacle for the powder, comes in three shapes: wide at the bottom and narrow at the mouth, narrow at the bottom and wide at the mouth, or of uniform width. These are sketched at the upper right as two triangles and a rectangle.
Positions for igniting the charge
The fire may be set in several places: at the uppermost extreme of the chamber base, in the middle of the base, at a distance from the base equal to the radius of its circle, at the centre of the powder's thickness, or at the centre of a round chamber. The pieces meant to ignite fastest must be of fine, well-condensed material.
Why thick barrels condense poorly in the cast
Good condensation of the metal rarely occurs in casts of great thickness, because the greater the thickness the longer the metal stays liquid, and the parts farthest from the middle of that thickness are the ones that condense first.
Series of barrels in section, numbered first to seventh
A vertical column of artillery barrels is drawn in cross-section down the right margin, each tagged with an ordinal caption (first with a b, second, third, fourth, fifth, sixth, seventh) keyed to the chamber and ignition schemes discussed.