( 94 9 ) 
PR OP. PRO B, 
To find the Di fiance of the Center of Percuffion from 
the Plane faffing thro' the Center of Gravity and 
perpendicular to the Axis of Rotation . 
SOLUTION. 
Let the fixth Figure be fuppofed in the Plane palling 
thro’ the Axis of Rotation, and in which the Center of 
Percuffion is fought. 
Let A B be the Axis of Rotation* AG C be the Inter-* 
fe&ion of this Figure with thePlane palling thro’ the Center 
of Gravity, and perpendicular to the Axis of Rotation, 
G be the Point whereon a Line, rais’d perpendicular to 
this Figure, will pafs thro’ the Center of Gravity ; B E 
be a Line parallel to A G wherein is the Center of Per~ 
cuffion. Then to find the Diflance .A B, let p Rand for 
&n Element of the Body propofed Handing perpendicular-, 
ly on any point D Draw D C perpendicular to AGC. 
and A B will be equal to theSummof all the Quantities 
p x G C x CD taken with their proper Signs, divided by 
the Body it fell multiplied into the Diflance A G. 
Having thus found the Diflance A B, . fuppofe the 
Plane of the Figure in Prop 25. to cut the prefent Figure 
at right Angles in the Line A E, and the Center of Per- 
cuffion will be rightly determined By that Propofition', 
The 26/^Propofition fhews how to determine the Den* 
fity of the Air at any Diflance from, the Center of che 
Earth, fuppofing the Denfity always to be proportional 
to the comp elling Force, and that the Power of Gravita- 
tion is reciprocally as the Diflances from the Center of 
th$ Earth* ; 
. ;Vi 1 
