260 
MINUTES OF PROCEEDINGS OF 
shot should strike below the level on the target. The instant the pro¬ 
jectile leaves the muzzle, it commences to fall by gravity, and the 
distance it will drop in 120 ft. can be found from the equation 
in which 
S = distance fallen in ft., 
g — force of gravity = 32*2, 
t = time taken by the shot in passing over 120 ft. 
If the projectile strikes above the level, the “jump” or angle of de¬ 
parture can be found from the equation 
where 
tan e = 
a *f* S 
e = angle of departure, 
a = mean height above level in ft., 
S = distance fallen by gravity in ft., 
x — distance from muzzle of gun to target in ft. 
For example, the mean height above the level on a target at 
120 ft. struck by three rounds from the 12-pr. rifled B.L. gun, was 
8*7 ins., or 0*7250 ft. The mean velocity of the projectile was 
1143 ft.; therefore the mean time of passing over 120 ft. was 0*1029 sec. 
Therefore 
so that 
S = 16*1 X (0-1029) 3 
= 0*1775 ft., 
and a + S = 0*7250 + 0*1775 
= 0*9025 ft,; 
0*9025 
tan , = ___ 
= -007521, 
and e = 25' 51". 
That is to say, when the 12-pr. rifled B.L. gun was fired with the axis 
of the bore horizontal, or apparently with no elevation, the shot really 
issued from the muzzle at an angle, or with an elevation, of about 
26 minutes. 
