Principles of progrejjive and rotatory Motion. 5 57 
tion, whilft the center of gravity moves over any 
given fpace (s) : for let p = the periphery of a circle 
whofe radius is unity, then p : 1 : : s : — - the radius 
P 
of a circle whofe circumference is the fpace to be palled 
over in the time of a revolution, and which mull: there- 
fore, by the Propofition, be equal to oc ; the point c 
therefore being determined, d may be eafily found, for 
from mechanics cgkdg is given; and from Cor. 3. 
Prop. I. when d comes to a, c will coincide with b, 
: cgx gd=agx gb, and confequently dg= . 
PROP. VI. 
To determine the time of one revolution y fuppojing every 
thing given as in Prop. III. 
The point d being given, we have from Cor. 2. to 
the laft Propofition, cg = ; put w equal the cir- 
cumference of a circle whofe radius is cg, and it appears 
from the laft Propofition, that w is the fpace the center 
of gravity pafles over in the time of one revolution ; 
hence, becaufe from Prop. iv. the center of gravity 
moves uniformly, we have by Prop. III. == - -- -- - 
X Ww’j'i X lie 
4 D 2 : 1" 
