( 34 9 ) 
U 
PR OP. PRO B,. 
To find the Diflance of the Center of Percuffion front 
the Plane faffing thro the Center of Gravity and - 
perpendicular to the Axis of Rotation. 
SOLUT 10 N. 
Let the fixth Figure be fuppofed in the Plane paffing 
thro’ the Axis of Rotation, and in which the Center of 
Percuffion is fought. 
Let A B be the Axis of Rotation A G C be the Inter* 1 
fedtion of this Figure with thePlane paffing 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; BE 
be a Line parallel to AG wherein is the Center of Per- 
ettffion. Then to find the Diflance.^ B , let p Hand for 
an 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 the Summof all the Quantities 
p x G C x C£> taken with their proper Signs, divided by 
the Body it felt multiplied into the Difiance A G. 
Having thus found the Diflance AB, . fuppofe the 
Plane of the Figure in Prop 25. to cut theprefent Figure 
at right Angles in the Line B E, and the Center of Per** 
cuffion will be rightly determined By that Proportion', 
The 2 6^?ropofition (hews 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* effing Force, and that the Power of Gravita- 
tion is reciprocally as the Dihances from the Center of 
the Earth. '■ * 
i 
The 
