tjx} Mr. landen’s new Theory of 
force f ceafes to act thereon ; like as the varying direc- 
tion of a projectile near the earth’s furface would imme- 
diately ceafe to change, if the force of gravity ceafed to 
;aCt. 
It is obfervable, that whilft the force f aCts, and the 
revolving fphere, in confequence of fuch aCtion, every 
moment takes a new axis, the angular motion about the 
axis will continue invariable; the aCtion of fuch force 
-only altering the axis without altering the angular velo- 
city of the fphere about it: like as the direction of a 
moving body is altered, without altering the velocity 
thereof, by an attractive force continually aCting on it in 
a direction at right angles to that in which the body is 
moving. And if ever the force f lliall ceafe to aCt, the 
fphere will inftantly revolve with its primitive velocity 
if) about the axis it then may have been brought to take 
by the preaCtion of that force. 
The new axis, about which the fphere has fuch ten- 
dency to revolve at any inftant during the a Chon of the 
force f, I lliall call the momentary axis', and the poles 
thereof the momentary poles. 
3. From the equation ~~ Ws// ’ r ~ x (art. 1.) we have 
~ — i-. Now if a continued attractive force (f) aCt 
* s/ r % — x z 
during the time t as above-mentioned, inftead of the 
4 inftan- 
