comprefled or clofed, will reftrain it from unbend- 
ing itfelf. 
j. By the Space through which a Spring is bent, 
I mean that Space or Length through which one End 
of the Spring is removed from its natural Situation. 
6 . By the Force of a Spring bent or partly clofed, I 
mean the leaft Force orW eight, which, when the Spring 
is bent through any Space lefs than its whole Length, 
will confine it to the State it is then in, without 
flittering it to unbend any farther. 
This being premifed, I fhall next, for the Founda- 
tion of what follows, lay down a Principle, which 
was verified by Experiment, in the Prefence of our 
Royal Founder about 70 Years ago, by the famous 
* Dr. Robert Hook'-, and has been lately confirmed 
by the accurate Hand of our common Friend Mr. 
George Graham . 
Principle. 
Ut Tenjio, Jic Vis: That is, if a Spring be forced 
or bent inwards, or drawn outwards, or any way 
removed from its natural Situation, its Refiftance is 
'proportional to the Space by which it is removed 
from that Situation. 
Thus, if the Spring CL, ( Fig 1. Tab. II.) retting 
with the End L againft any immoveable Support, but 
otherwife lying in its natural Situation, and at full 
Liberty, fhall, by any Force p, be p retted inwards, 
or from C towards L , through the Space of One 
Inch, and can be there detained by that Force p. 
* Lectures de Potentia rejlitutiva, 1678. 
the 
