a c n b d. Experiment of the force that an iron wire can exert in various lengths. Reminder of how you should make the experiment of holding, or how much an iron wire can sustain. For which experiment keep this method. Fix an iron wire 2 braccia long, or thereabouts, in a place where it stays firm. Then attach to it a basket or hamper or whatever you like, into which, through a small hole, a hopper will pour fine sand. And when that iron wire can no longer sustain and breaks, fit a little spring so that the hole of the hopper closes at once, so that no more sand falls into the basket, which will fall on its foot, because it will fall from a height of half a finger. And note how much weight it was that broke the wire, and note in what part of itself the said wire breaks, and make this test several times to confirm whether it always breaks in one same place. Then make the wire shorter by half than before, and note how much more weight it sustains. And then make it 1/4 of the first length, and so, little by little, you will proceed at various lengths, noting the weight that each one breaks and the place where it breaks. And this test you will make of each metal, and of woods, stones, ropes, and everything apt to sustain. And make of each thing a general rule. And this same you will do of earthbound supports, that is those which, in sustaining, have one extremity of themselves fixed in the ground or toward the ground.