There are two kinds of balances, namely reversed and upright. The reversed balances are of two forms, namely with equal arms and with unequal arms.

The common balances vary in two ways, namely with equal arms and with unequal arms. The shape of the beam of the balance varies in [several] ways, namely straight, angular, and curved. The ways of positioning the arms of the balance are infinite, even though the pendants depart from their arms at right angles and join perpendicularly to their weights. There are three varieties of the angles that the pendants make in separating from the arms of their balances, namely right, acute, and obtuse. There are six diversities of the combinations that the angles of the cords separating from the arms of the balances can make.

1st: with the right angle the acute and the obtuse can stand;

2nd: with the acute angle the right and the obtuse can stand; 3rd: with the obtuse angle the right and the acute can stand: with the right, the acute and the obtuse; with the acute, the right and the obtuse; with the obtuse, the right and the acute. Among equal weights, that one will show itself heavier which separates at a right angle from the arm—natural and potential—more remote from the center of the pole of the balance.

The central line of the universe is that which arises at the center of the world and ends at the center of gravity of each body.

The center of every gravity. Every heavy body weighs along the central line of the universe, because from every side it is equally drawn from that middle. The string of the bow, being of uniform power, will be of uniform resistance; its force will break it in that part which is most remote from the ends, although the like happens at every point of its length. The weight m does not rest on b, but discharges entirely onto a c, pushing along the lines b a and b c upon the poles of the wheels. The lesser quantity will never be able to contain the greater quantity; therefore the quantity a b c cannot descend nor pass through the quantity a c (whence every heavy body distributes itself upon whatever forbids it its natural descent). Now this impediment can, in this case, arise in two different ways, of which the first is by means of the two walls n m and f g, which, not letting the angle b straighten to the line a t c, receive transversally within themselves all the gravity suspended at the angle b; and because the power of every heavy body passes through its supports to the end of their fastenings, that suspended gravity does not weigh along the line b r, but runs entirely into a c, along the line b a and along the line b c. The second way is when such walls do not exist and the aforesaid prohibition is caused by means of the cord a c; then that gravity would distribute itself along the whole length of that cord and, by its own straightness, would exert its force with its entire power.

It is impossible to cause motion in the movable body from its own mover. It would turn with as much power as the weight of the material that pours out, were it not for the great weight of the material resting upon the circle of the wheel, which bears down upon its pole and impedes the ease of its motion.