THE EOYAL AETILLEEY INSTITUTION. 
297 
be very difficult to calculate this theoretically; it must therefore be 
decided experimentally. 
An important point in gunnery is the relation between the weight of 
a projectile and its calibre. In days of smooth-bore ordnance, when 
all projectiles were spherical, this question did not arise; but now it is 
both necessary and difficult to decide what is the proper proportion 
between the weight and calibre of a projectile. In connexion with this 
subject comes up that of lowness of trajectory. 
Lowness of trajectory is advantageous— 
(1) On account of greater accuracy. 
(2) On account of harder hitting—for lowness of trajectory means 
greater velocity, and consequently more energy in the shot. 
(3) On account of the greater distance covered effectively by the 
projectile—“longueur battue,” as the French term it; that is to say, 
a projectile with low trajectory passes over a greater distance within 
the height from the ground reached by the objects fired at, than one 
with a high trajectory. 
It has been mentioned above that a lower trajectory implies a greater 
velocity—for projectiles drop equal distances in equal spaces of time, and 
the quicker they are moving the greater space they pass over while 
falling any given distance; but it must be clearly borne in mind that 
the velocity which gives effective lowness of trajectory is not initial 
velocity, but the velocity remaining when the projectile arrives within 
the rayon of the objects aimed at; and it is not at all necessary that the 
projectile that has the greatest initial velocity should have the greatest 
remaining velocity at a given range, for it may easily be that a projectile 
of such a shape as to experience much resistance from the air may start 
with an initial velocity considerably higher than that of a second 
projectile of a form to experience little resistance, and that the first 
should lose its velocity so rapidly as to be caught up and passed by the 
second before it reaches the end of its range. Our object, therefore, 
will be to obtain as great a remaining velocity as possible. 
If two projectiles are of equal weight, and have similarly shaped heads, 
the one which is longer with smaller calibre will experience less 
resistance from the air, and will therefore lose its velocity slower than 
the other. The inference comes at once that guns should be made of 
small calibre, and that long projectiles should be used. 
But there are certain things to be considered which point in the 
opposite direction. 
It is true that if two projectiles start with the same initial velocity^ 
the one of smaller Calibre will have a greater velocity at the end of a 
certain range; but in a gun of a very small calibre the cartridge becomes 
very long, and the powder is blown out partially unconsumed, unless 
the gun is of inordinate length, so that the projectile will not start 
with the initial Velocity that one would from a gun of larger calibre 
that burnt all its powder* Moreover, the longer projectile requires a 
sharper twist to keep it steady^ dnd this causes a greater strain upon 
the gun. Again, the internal capacity of a long shell of small diameter 
is less than that of one of the same weight and larger diameter ; so that 
