If the wheel raises a weight with a single tooth set on its axle, you will find that the blow given by the fall of such a weight is of greater force than would be the fall of two blows made when that axle had two teeth. For with a single tooth it can raise a greater weight, because of the momentum the wheel acquires while it turns empty, that is, without raising a weight, and then, coming upon the weight, it raises it with great force.

d, a b c e f, h

This instrument is for stamping medals, of which the mould must sit at a, and the medal at b, and one strikes the die d with the wooden mallet. And when you wish to open the medal, strike the die f. And at h there must be a strong spring, so that when the die f goes down by the blow given to it, that spring h may be powerful enough to drive back the pieces c and e and open the medal b of itself. And the piece c must be broad below and narrow above, so that, on striking the die d, it does not lift up on the opposite side.

c