THE ROYAL ARTILLERY INSTITUTION". 
463 
Accidental Causes . 
There is very little new to say about accidental causes, and their name is 
legion. Several of these are described in the Course of Musketry Instruc¬ 
tion for the Army . Such are,'—damage caused to the powder or ball by 
careless ramming home,—the effect of the sun glancing on the sights,—the 
powder from the cartridge being more or less carelessly weighed, or any 
being spilt, &c. But the perpendicularity of the sights, or in artillery 
practice, the horizontality of the trunnions is a more important matter. 
Thus, if the right wheel be raised six inches the shot is thrown to the left, 
and there is a deviation of 17 yds. in 2000 in this case. There would also 
be at the same time a slight decrease in range. Perhaps a table might be 
constructed with advantage, for rifle practice, showing the amounts of 
deviation, from the sights not being perpendicular. 
The target and gun are also seldom in the same horizontal plane, so that 
gunners may be without knowing it, sometimes firing up, and sometimes 
down an inclined plane, and the ranges would be altered accordingly. This 
matter of ranges is especially important when firing up hill, and seems to be 
too often neglected. 
If the axis of the bullet be inclined while in the bore, or if its base 
changes its form unequally during the explosion so that something of the 
kind was to occur that is shown in Eig. 7, the projectile would have a 
deviation to the side opposite to that to which it was inclined on leaving the 
bore. The elasticity of the gas at the open part will impede this action, but 
it will be much diminished outside the barrel. 
If there is an overcharge, or a strong pull on the trigger, the tendency will 
be to incline the axis of the gun to the side of the shoulder from which it is 
fired, for it is evident (Eig. 8) that the leverage of the force required will be 
exerted about the axis on which the gun is held in this direction. A pull 
on to the target accounts for many a lucky shot. 
There is also always a tendency in firing from the shoulder for the muzzle 
of the piece to rise. The reason of this I have shown in the accompanying 
figure (Fig. 9) is owing to the bent shape of the stock. A great deal of bad 
firing arises from this source, as novices contract bad habits of leaning 
forward and shutting their eyes, even while they are pulling the trigger, 
which very much impairs their chance of hitting the target. 
After a considerable period of rapid firing there may not be such good 
practice at long distances, from the motion of the particles of air produced by 
heat resulting in the .distortion of the aim. The amount of deviation will of 
course be R sin e } if R be the range, and e the angle of refraction of the air 
between the sights. 
I omitted to state, when treating of defects of system, an improvement 
which would certainly mitigate a great number of evils, but which has been 
strictly tabooed by government, viz. the introduction of telescopic sights. 
No one who has ever practised at long distances can have failed to see that 
these are the very things calculated to make rifles serviceable as an arm, and 
their practice, as far as aiming goes, all but perfect. It is the small angle 
[vol. iv.] 61 
