THE ROYAL ARTILLERY INSTITUTION. 
295 
ON THE PRINCIPLES 
WHICH EEGULATE THE 
EFFICIENCY OF ARTILLERY PROJECTILES, 
BY 
LIEUT. E. CLAYTON, R.A. 
THE R.A. INSTITUTION PRIZE ESSAY OF 1873. 
/ 
“ Amphora ccepit 
Institui, currente rota cur urceus exit.” 
A clear understanding of the principles upon which the efficiency of 
artillery projectiles depends is of the utmost value, both for the most 
effective use of the materiel we at present possess, and for the direction 
of our attention to the paths in which the improvement of that 
materiel is to be sought. 
These principles divide themselves broadly into two great classes. 
Firstly, those affecting the chance of the projectile striking the object 
aimed at; and 
Secondly, those which relate to the effect produced by the projectile 
when it does strike. 
These two classes of principles will be found to touch one another at 
certain points; but it will be convenient to consider them separately, 
pointing out, as they present themselves, the circumstances under which 
they are mutually dependent upon one another. 
We will proceed to consider first the principles of the first class. 
When a projectile is fired from a gun, it describes a path through the 
air which is called its “ trajectory •” the shape of this path being 
determined by the three forces acting on the projectile—the force of 
projection, the force of gravity, and the resistance of the atmosphere. 
It will be out of place in this essay to go into the theory of the flight 
of projectiles; we will only consider the practical questions that arise. 
The two conditions for rendering the chance of hitting the object 
aimed at as great as possible, are accuracy of flight and lowness of 
trajectory. 
Accuracy of flight is sought to be obtained by giving the projectile 
a rotation round an axis coincident with that of the bore of the gun, so 
as to counteract the effect of the resistance of the air, and of inequalities 
in the density of the shot in different parts, tending to produce eccen¬ 
tricity of the centre of gravity, and of irregularity of motion in the bore 
of the piece. This rotation also allows of the use of elongated projec- 
