The bombard called 'Fulminaria', with a cooling water box
A giant copper cannon in two pieces, its leaded iron dart, and a water bath to cool the barrel
The long inscription specifies a huge artillery piece the notes name 'Fulminaria' ('the thunderer'), built in two joined sections of 8 braccia each - 16 braccia in all - with a bore of 1/8 that would seat 128 balls of 16 pounds apiece. Because such shot would fly too lightly, the note substitutes a one-braccio iron bar leaded along its length (iron-lead-iron), weighing 40 pounds and driven by 40 pounds of powder. The fine-copper barrel is to be drawn after firing into a box of water, shown at lower left, so that the hot metal quickly sheds its heat. The sheet is crowded with related drawings of the barrel, its carriage and the water-bath, with mirror-writing throughout.
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The 'Fulminaria': a two-piece giant bombard
The instrument is to be called Fulminaria for its great fury. It is built of two pieces, each 8 braccia, making 16 braccia in all without the breech; the bore is 1/8, so that the 16 braccia hold 128 balls of 16 pounds each.
Leaded iron dart and water-cooling box
Because the ball would be too light, a one-braccio iron bar is leaded from the middle forward, leaving a span of bare iron at the point; it weighs 40 pounds and takes 40 pounds of powder. The fine-copper barrel is drawn into a box of water after firing so it quickly loses its heat.
The firing point
The case that holds the weapon is labelled at the spot marked 'where the fire is set'.