* It is impossible that the cord which turns any wheel, being wound about its circle, should not make its line form a right angle with the line of division — that line which goes from the centre of the wheel to the extremity, where the cord parts from the wheel.

a x – m – n – o – f r – 6 – 4 – 2 – 4 – t – 11

* In this demonstration the simple office of the balance occurs, since the weights that hang from the arms of the said balance — the threads, the supports of those weights — always make right angles between their own line and that of the beam of the balance; and right are the angles of the threads that leave the round balance formed by those threads and by the line of division of the threads from the circles at a o and at r f. I shall always call 'line of division' the one that goes from the centre of the wheel to the places where the threads pulled by the weights begin to straighten and abandon the roundness of the wheel — such as the thread x a, which begins to straighten at a; and likewise from a to the centre of the wheel I call and conclude the line of division; and likewise the thread f t parts from the wheel at f, and from f to the pole is the second line of division.

* Now let us speak of the weights hung on the wheel. I say that, because the weight 4 is hung four times nearer to the pole than the weight f, it therefore of itself deserves four times more weight than f; and, so as not to weary you, the others simply follow the balance generally in all its rules.