7 2

Sir Isaac Newton’s Book I.

the weight at E. Now here, if, when the lever should beput in motion, and turned upon the point C, the velocity,wherewith the point F would move, bears the fame propor-tion to the velocity, wherewith the point E would move, asthe weight at E bears to the weight or force at F ; then thelever thus charged will have no propensity to move eitherway. If the weight or other force at F be not so great as tobear this proportion, the weight at E will not be sustained ;but if the force at F be greater than this, the weight at E willbe surmounted. This is evident from what has been saidabove % when the forces at E and F are placed (as in fig. x 3.)on different sides of the support D. It will appear also equal-ly manifest in the other cafe, by continuing the bar B C infig. 2.4. on the other side of the support D, till CG be equalto C F, and by hanging at G a weight equivalent to the powerat F; for then, if the power at F were removed, the twoweights at G and E would counterpoize each other, as in

the former cafe : and it is evident, that the point F willbe listed up by the weight at G with the same degree offorce, as by the other power applied to F ; since, if theweight at E were removed, a weight hung at F equal to*that at G would balance the lever, the distances CG andC F being equal.

33. If the two weights, or other powers, applied to thelever do not counterbalance each other ; a third power mayhe applied in any place proposed of the lever, which shall

1 Pag. 65. 68.

hold