THE BOYAL ARTXLLEKY INSTITUTION. 
117 
REPORT 
ON 
EXPERIMENTS WITH MWS ELECTRO-BALLISTIC 
APPARATUS. 
By Captain Noble, late Royal Artillery. 
1. In forwarding to the Ordnance Select Committee the results of 
the experiments in initial velocity, which I have had the honour of 
carrying on under their direction, I have to make the following 
remarks :— 
2 . The instrument employed in these investigations was the electro- 
ballistic apparatus of Major Navez,* and it may not he out of place 
here to recapitulate the leading points of its construction. 
The apparatus itself is merely an arrangement for measuring, with 
extreme accuracy, a certain very small interval of time. Two screens, 
the nearer one a short space from the muzzle of the gun, are placed 
at an accurately measured distance apart, and it is the object of the 
instrumenhto ascertain the time which the projectile takes to pass over 
this measured space. 
3. The apparatus consists of three parts, the pendulum, &c., the 
conjunctor, and the disjunctor. The principal part is the pendulum 
and graduated arc. The pendulum, before an observation, is held sus¬ 
pended by an electro-magnet, the current magnetizing which passes 
through the first screen. To the pendulum is attached, by means 
of the pressure of a spring, an arm with a vernier. The pressure of 
this spring is so regulated that the arm vibrates freely with the pendu¬ 
lum, but at the same time it offers but little resistance to the action of 
a powerful horseshoe electro-magnet, which, when the circuit mag¬ 
netizing it is complete, clamps the vernier arm with great firmness. 
4. The current which passes through the second screen holds, 
by means of an electro magnet, a weight suspended over a spring, a 
point from which is kept just over a cup of mercury. When this 
weight is permitted to fall, it presses the point into the cup of mercury, 
and completes the circuit, magnetizing the horseshoe magnet which 
clamps the vernier needle. This part of the apparatus is termed the 
conjunctor. The action of the instrument is very simple and readily 
understood. When the projectile cuts the wires in the first screen, the 
magnet which holds the bob of the pendulum in its initial position is 
demagnetized, and the pendulum commences an oscillation. When the 
wires in the second screen are cut, the weight of the conjunctor drops, 
completes the circuit, clamping the vernier, and the arc through which 
the pendulum has moved is a datum from which may be computed the 
corresponding time. 
o. An important part of the apparatus (the disjunctor) remains yet 
to be mentioned. It will be obvious that the arc which we have just 
supposed to be measured corresponds to the time which the projectile 
takes to pass over the distance between the screens, plus the time which 
the weight of the conjunctor takes to fall from its initial position to 
6177. 
Belgian Artillery. 
A 
