THE ROYAL ARTILLERY INSTITUTION. 
207 
ON FINDING THE CENTRE OF GRAVITY OF A GUN ON ITS CARRIAGE AND 
LIMBER, OR OF A GUN ON ITS CARRIAGE UNLIMBERED. 
By Lieut.-Col. H. H. MAXWELL, B,H.A. 
I had occasion a few years ago to endeavour to find the centre of gravity 
of a gun on its carriage unlimbered, as a preliminary to the solution of 
another question. The method I pursued was a slight and obvious alteration 
in the following method of finding the centre of gravity of a four-wheeled 
cart, derived from Fisck's Elementary Treatise on Mechanics of Solid Bodies, 
and quoted in the Treatise on Mechanics by Joseph Dirschl, Vienna, 1857. 
As I have never seen this subject written of elsewhere, I have ventured to 
lay it before your readers. 
1. Let it be taken for granted that the carriage as should be the case 
is symmetrically built and laden, the vertical plane passing through the 
middle point of both axles must be that in which gravity acts. If we run 
the carriage on to a platform such as MN (fig. 1), inclined to the horizon at 
Fig. 1. 
an angle in such fashion that both axles shall be horizontal, and chock 
the hind wheels with wedges AT; if, again, we suspend the ends of the 
axle-arms of the front wheels by the two ends of a chain, and attach the 
centre of this chain to one arm of a balance, and then increase the counter¬ 
poise in the opposite scale, until by the play of the beam the front wheels 
just lift clear of the inclined plaue MN and no more, then, the weight in the 
scale, less the weight of the chain and the front wheels will indicate the 
vertical pressure, which the front axle exerts on the naves of its wheels. 
Let this weight be represented by jo, and let us imagine an equal force at 
C acting vertically upwards; this force, after abstraction of the chain and 
front wheels, will keep in equilibrium the upper part of the carriage (that is, 
less the four wheels) and its load on the fulcrum C of the hind axle. 
Let S be the centre of gravity and W the weight of the carriage ( less its 
wheels) and its load, which acts in the line SJD vertically downwards, 
then is 
CD . W = cC.p. 
