On the bombard: degrees of velocity as fractions of a circle
Quarter-circle, semicircle and full circle stand for 1, 2 and 4 degrees of speed
Under the heading 'On the bombard', Leonardo pairs three framed figures with degrees of velocity: a quarter-circle in a rectangle's corner (a) yields one degree, a semicircle (b) two degrees, and a full circle with wheel and crank (c c) four degrees in the same time, though this last needs good reinforcement and material. He concludes that the bombard in which a greater amount of powder is ignited in equal time drives its ball faster and farther. A small standing figure at the right serves as a scale.
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More powder ignited in equal time drives the ball faster
The bombard in which a greater amount of powder is ignited in the same time propels its ball more swiftly and to a greater distance. Leonardo ties the gun's power directly to the rate at which its charge fires.
Degrees of velocity: 1, 2, 4
In equal time the three figures give one, two and four degrees of velocity, the last being quadruple the first. Leonardo notes that the fourfold case demands good reinforcement and good material to withstand it.
Quarter-circle, semicircle and full circle in rectangles
Three rectangles carry, in turn, a quarter-circle (a1), a semicircle (b) and a full circle (c c), the geometric fractions standing for successive degrees of speed. The full-circle case is drawn with a wheel and crank.