Ballistics of the bombard: firing upward and with the wind
Range, air resistance, and how the gun's report changes with wind, mist, water, or a wall
These notes work out the ballistics of gunfire in relation to air and wind. Leonardo argues that a ball fired straight up travels farthest, because the propelling fire follows it more easily and the rising air grows thinner and resists less, and that firing two balls with two charges in one passavolante yields a single blast, the first ball driven farther than the second. He compares firing with, against, and across the wind, with range and the report of the gun varying in each case, and the lower circle, lettered a, b, c with 'equidistant' and 'oblique', maps the course of direct and contrary winds. A closing note adds that misty air, or aiming the muzzle down at water or a wall, makes the report louder.
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A ball fired straight upward travels farthest
A ball shot upward covers more distance than along any other line of motion, for two reasons: the fire that drives it follows more easily upward and keeps its motion more uniform, and the higher the air rises the thinner it grows and the less it resists.
Two balls and two charges in one passavolante give a single blast
If two balls are fired in one passavolante with an equal charge of powder between them and both charges are lit at once, the two explosions become a single blast, since the first powder acts by opening the air to the second. The first ball is driven farther than the second, augmented in motion by that second charge.
Firing with, against, or across the wind changes range and report
Firing against the wind gives a great report but a short, weak shot; firing along the wind's course gives a small report but a long, powerful shot; firing in still air, both are middling. The behaviour of the moving air governs both the range of the ball and the sound of the flame.
Wind-course circle a, b, c: percussion and thunder
The circle at the foot shows the course of the winds, direct and contrary, with points marked a (maximum or minimum), b (middling) and c (equal) percussion and thunder, and the directions labelled 'equidistant' and 'oblique'.
Louder report in mist or firing down at water or a wall
If you fire in misty air the sound will be great, and if you turn the mouth of the bombard downward toward the surface of the water, or toward a wall, the sound will likewise be great.