THE ROYAL ARTILLERY INSTITUTION. 
461 
opposite direction in another, and in some parts were cylindrical when not 
intended to be so. On trial of these same barrels in the shooting gallery 
he found his idea amply corroborated by the uncertainty in the flight of the 
projectiles. No doubt if an absolutely true delivery can be attained, we shall 
be able to obtain an immense number of highly interesting results,^of which 
at present we are ignorant. 
Defects of System, 
Of defects of system I shall only enumerate three out of the many that 
present themselves. This will be :— 
Windage, Vibrations, Recoil. 
We do not yet know enough of windage to fully work out, or even to 
comprehend its important relations to the present subject. Could we know 
the exact curves, which the projectile describes inside the bore, and hence 
the final angle of rebound at the chase, we might be able theoretically for 
given conditions, to allow for the resulting error in the line of flight, and 
arrive at better conclusions on other subjects. For the initial direction of 
the shot never corresponds to that of the piece. It will in fact always 
make with it some small angle, which must never be neglected in calculating 
either a lateral or vertical deviation. If a be this angle, and R the range; 
R tan a will be the deviation due to this cause, and R tan a + $ ( R ) will 
indeed be the general formula for all deviations. 
In some bronze guns, and whenever the metal of a gun is soft, the shot 
will form lodgments due to excess of windage. There is in most of these 
lodgments a prominent ring caused by the pressing back of the metal, which 
will greatly assist in producing inaccuracy of fire. At the same time the 
ball starts up with accelerated force, and the gun will be correspondingly 
injured. 
The axis of the best theoretical projectile should coincide perfectly with 
the axis of the bore, from which it is fired, and therefore the projectile itself 
should completely fill the bore. The expanding principle is perhaps to be 
preferred to the forcing, but whether compound or homogeneous shot be 
employed there should be an even expansion, or there would be an almost 
equally great inaccuracy of fire from this source. Preponderance of weight 
on any one side of the shot at a distance from the axis is to be avoided as 
producing greater eccentricity. 
When a gun has been fired many times in succession the range is generally 
considerably increased with smooth-bored guns. This is partly due to the 
fouling diminishing the windage, and partly to the warming of the gun, and 
consequent non-wasting of the heat of the gas. Perhaps also this diminish- 
ment of windage may be owing to some peculiar action of the heat on the 
metal composing the gun. For if the exterior of the gun retain the same 
shape, while the interior be expanded by the heat the lines of least resistance 
to the heat forces may lie inwardly and the bore may thus contract. This 
phenomenon if it exists should be best shown in welded guns like Sir William 
Armstrong's. 
