432 
PRINCIPLES OP GUNNERY. 
Personal Errors in laying are incident to all systems of laying or sighting, 
faying 1 , 11 and may be reduced to a small quantity by careful and intelligent 
gunners when the object can be clearly seen. Constant practice at 
different ranges is the best way of acquiring this great essential of the 
gunner's art. 
inclination Owing to the gun being sighted when the trunnions are horizontal, 
trunnions there arises an error in fire when the trunnions are not horizontal— 
horizon w ^ en gun-carriage stands on uneven ground. If the gun is 
laid by the sights, the projectile deflects towards the side of the lower 
trunnion. 
If h is the height of the perpendicular tangent sight for a given 
elevation, and the axis of the trunnions is inclined at an angle a, the 
right trunnion down, the deflection leaf must be increased by h sin a; 
if, on the contrary, the axis of the trunnions is inclined at an angle a, 
the left trunnion down, the deflection leaf must be diminished by 
h sin a. 
Unsteadi- Unsteadiness of the gun and carriage may result from too large a 
£ua S car- charge being used for the weight of the gun and carriage, causing an 
platform on excess i ve jump. The nature of the ground, or platform on which 
firing. the carriage stands, will have some effect on the amount of jump • also 
the method of applying the brake on the carriage to check the recoil. 
If the brake does not act exactly at the same time in each round, there 
will probably be a variation in the jump of the gun, which will cause 
an error in fire. 
(To be continued.) 
