How a Cannon-Ball Strikes a Wall: Aligned or Twisting Blows
The ball does most damage when the striking part is farthest from the mouth and aligned with its centers
Two sketches, at the top and middle of the folio, show a bombard firing point-blank at a stout wall: the ball at the instant of contact, and the wall collapsing just after. Leonardo reasons that the wall is damaged more or less according to which part of the ball strikes it, the part farthest from the mouth, lying in a line with the centers of weight and of flight, unites the powers and delivers the greatest percussion and ruin. When instead the part nearer the mouth strikes, it lies off that center, the heavier side pushes harder, and the shot twists furiously so that its blow has less effect. He adds that more powerful shots meet weaker resistance from the wall, and, cramped for space, refers the reader to the two walls drawn above.
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Which part of the ball strikes decides the damage to the wall
A wall struck by a bombard's shot is damaged more or less according to whether the part of the ball that strikes is nearer to or farther from the cause of its motion. Whether the blow is heavier or lighter derives from the projectile striking at a nearer or farther distance from that cause.
Aligned centers give the heaviest blow; off-center makes the shot twist
The part farthest from what drives it goes foremost and lies in a line with the point thrusting it and with the centers of weight and of flight, so both powers bear equally on it and, united, cause the greater percussion and ruin. When the part nearer the mouth strikes, it lies beyond that center, the heavier side pushes more, and the shot twists furiously, its line of flight bending so the blow has a lesser effect.
Stronger shots meet weaker resistance from the wall
The percussions of projectiles having greater power find the wall's opposition against them weaker, while the lesser ones meet greater and stronger resistance. Constrained for space, Leonardo refers the reader to the two walls depicted above rather than defining the greatest line of resistance.
Bombard firing at a wall, before and after collapse
The upper sketch shows the nose of a bombard shooting its ball horizontally against a stout wall at the instant of contact. The middle sketch repeats the view just after impact, with the wall collapsing.