2$& Mr. Thompson’s Experiments 
Of the method made ufe of for computing the velocities of the 
bullets. 
As the method of computing the velocity of a bullet from, 
the arc of the vibration of a pendulum into which it is fired is 
fo well known, I fhall not enlarge upon it in this place, but 
lhall juft give the theorems that have been propofed by different 
authors, and fhall refer thofe who wifh to fee more on the fub~ 
je£t to Mr. robins’s New Principles of Gunnery; to Profeflor 
euler’s Obfervations upon Mr. robins’s Book; and, laflly, to 
Dr. huttqn’s Paper on the initial Velocities of Cannon Balls,, 
which is publifhed in the Tran factions of the Society for the 
year 1778. 
If a denote the length from the axis of the pendulum to the 
ribbon which meafures the chord of the arc of its vibration ; 
g , the diifance of the center of gravity below the axis ; 
f the diifance of the center of ofc illation ; 
h, the diifance of the point: If ruck by the bullet; 
c, the chord of the afeending arc of the pendulum 
P, the weight of the pendulum ; 
b , the weight of the bullet, and 
v , the original velocity of the bullet; 
v = c - . Xy| -i- y x — j-rr, is a theorem, for finding the velocity 
upon Mr. robins’s principles. 
is the theorem propofed by Pro- 
felfor Euler, who. has correfled a fmall. error in Mr. . robins’ s- 
/+!> 
V- X rf + ~ — 7~ * 
a bh ' 2/ 
method;, and 
r Yg f+h 
* Put the rational part — X — , -f- — : 
r a bh 2 j 
n 7 . and exp refs /in the thoufandth- 
garts of a Rhy.nland foot ; then the velocity with which the ball flrikes the pendui 
Lum will be — — 
/ 
Rhynland feet in a fecond,. 
