566- Mr. vince’s InveJHgation of the 
on each fide ab are fimilar, and fimilarly fituated, and' 
the force to adt as before, then it is manifeft, that as 
each plane endeavours to preferve the fame plane of ro- 
tation, the two planes connected will alfo continue to 
move in the fame plane of rotation, for the adlion of 
one plane on another, on each fide the plane of rota- 
tion, being equal, cannot tend to difturb the motion in 
that plane ; and as this muft be true for any number of 
planes thus fimilar and fimilarly fituated, it is evident,, 
that if a force fhould adt upon a body, and each fee- 
tion, perpendicular to the diredtion of the force, Ihould 
be fimilar on each fide the plane puffing through the di- 
rection of the force, and the center of gravity of the 
body, that that plane would be the plane of rotation in 
which the body would both begin and continue its mo- 
tion. It appears alfo from what has been proved, that 
if every fedtion on each fide that plane had not been fi- 
milar, the plane of rotation would not necejfarily have 
continued the fame after the commencement of the mo- 
tion. Hence all bodies, formed by the revolution of any 
plane figure, will have the axis about which they were 
generated, afixt axis of rotation ; to determine, however, 
every other axis of a body about which it would continue 
to revolve, would be foreign to the fnbjedt of this paper. 
Suppofing therefore the plane of rotation to continue the 
fame 
