That bombard which has its tail between two trumpets, the fire will not let it move. That powder which is more attractive to fire will drive the ball more, and the more will the bombard recoil.
If you give fire to that bombard which has its hole at the very end of the tail, it will make less flight, because it kindles from the point of fire forward. If you gave fire in the middle of the length of the tail, the fire would take two contrary courses and would kindle double the powder, and very swift would be the course of the ball, and great damage it would do to the rampart.
If you give fire to a pointed tail, small will be the flight of the ball.
The reason why the bombard gives backward. The fire that multiplies within the body of the bombard, not finding a vacuum sufficient nor capable of its quantity, with sudden fury seeks a receiving place; and that place and the air is met with impetuous repercussion. The air being a grosser body than the fire, it makes resistance to the flame and gives place to the heavier ball; and the flame, thrust back by the body of the air, and that part which remains within being unable to discharge itself, seeks to make a place capable of its increase, and pushes the body of the bombard backward. In the likeness of the rocket, which, not being able to have place for its effect, flees the cause; and for this reason the powder that kindles more quickly gives less space to empty the air, and the slower gives space to the air to make it give place.

This flame that issues from the bombard is clearly of marvelous power, as appears in the driving of the ball. And the flame, not being able to receive the vacuum with the quickness of its multiplication, but rather finding resistance in the air it makes, there is made of that condensed air surrounding it a resisting body like the bombard; and with the flame that remains within, joined to that outside, and wishing to multiply but forbidden by the resistance of the said air, it pushes and does to the bombard as it first did to the ball, as appears in the drawing above. And this flame does, between the bombard and the percussion of the air, as a green and strong lance run by a jouster against a resisting wall: that which the lance cannot do with the point, it does with the butt, throwing the jouster to the ground with its resisting hardness. And the road the ball makes through the air is filled for a long distance by the fire that drives the ball. Or if you put a man in a short wine-cask, and the bottom of the cask where the enclosed man's feet stand were near a wall, you would see the man do, by stretching his legs, to the cask as the fired powder of the bombard does; for, not being able wholly to stretch himself, he carries the cask backward with his head.

In walls of brick shoot first with the cortaldo, boring and battering in various places. Then shoot in the middle with a great bombard, otherwise you will not do good work.

Festoon.