7 C ITALIAN FIELD GUN. 
39 7 
It might appear at the first glance paradoxical to state that the 
lightness of the equipment is in a very great measure due to the small 
diameter of the wheels. This statement we will endeavour to substan¬ 
tiate by the following considerations. 
The diameter of the wheel, if taken as a starting point, determines 
very closely the width of track. It further determines the length of 
the trail—seeing that all artilleries have nearly the same trail angle. 
It further implies the scantling of the wood and metal work of the 
wheel within certain limits, and thus the weight of the wheel. It 
determines indirectly the length of the axles of all carriages, the width 
of framework of limbers, wagons, &c. 
In former days, the height of the gun above the plane was very 
properly considered an important element in a gun-carriage; for it was 
argued that with the smooth-bores the greater the range at point blank 
with a spherical shot which ricochets, the more efficient the gun, and 
the readier it is to fire case-shot to resist a charge of cavalry. But is 
that element of the same importance with rifled guns as it was with the 
smooth-bores of old ? The answer may fairly be given in the negative, 
provided the height of the muzzle be convenient in serving the gun. 
Case shot being now almost abolished, resort must always be had to 
the tangent sight at all ranges. If, now, it be conceded to be a fact— 
which to all intents and purposes it most assuredly is—that the tra¬ 
jectory of a rifled gun at 2000 yds. is precisely the same for a little 
more than its first half as that at 1000 yds.,* the height of the gun 
above the plane, excepting for convenience of service, is a matter of no 
importance: If this be granted, why should not the diameter of a 
gun-wheel be 4 or 4^ ft. in lieu of 5 ft. ? The answer to this question 
will probably be that the higher the wheel the easier the draught, 
within reasonable limits. This is true, provided the weight drawn 
be taken to be constant; but if the weight vary in some direct ratio 
with the height of the wheel, that answer will not be true.- If the 
weight, for instance, could be reduced one-third by cutting 1 ft. <jff the 
diameter of the wheels, it would hardly be contended that the draught 
with the bigger wheel was the lighter. 
Again, if we consider the strength of a wheel, we see that within certain 
unknown limits the strength—supposing the scantling the same—varies 
inversely with the diameter; in other words, the smaller the diameter of 
the wheel, within practical limits, the stronger it is. Or, to put it another 
way, we may produce wheels of the same strength by using smaller 
scantlings of materials in a small wheel, than we can in a large wheel. 
In other words, we can get a proportionately lighter wheel of 4 ft. in 
diameter equally strong with the service wheel of 5 'ft. 5 and this would 
have, as above shown, no injurious effect upon the shooting of the gun. 
Now, supposing we reduce the diameter of the wheel from 5 ft. to 4 ft., 
by way of argument, we may reduce the track of the carriages from 
* Consider the trajectory at 2000 yds. on paper to be represented by a bent wire. Pin the wire 
down at the muzzle point, then cause the bent wire to revolve round the muzzle point until it cuts 
the horizontal line, representing the range, at 1000 yds.; that portion of the bent wire which is 
above the horizontal line will represent the trajectory at 1000 yds. 
