354 
VELOCITY AND PEESSUEE INSTEUMENTS. 
INSTRUMENTS EMPLOYED BY THE COMMITTEE ON EXPLO¬ 
SIVES. FOR INVESTIGATING THE ACTION OF GUNPOWDER 
IN THE BORES OF GUNS. 
BY 
CAPTAIN C. JONES, R.A., 
Assistant in the Experimental Branch of the Director of Artillery's Department. 
Dueing the past few years, immense progress has been made in the 
investigation of the action of fired gunpowder, resulting in considerable 
improvement in the descriptions of powder employed in the service, and a 
great increase in the power and safety of our heavy guns. Up to the year 
1869, however, when the Committee on Explosives was first appointed, 
there is no question but that England was behind-hand in the matter of 
powder, and that the R.L.G. then used-—which had been introduced for the 
B.L. rifled guns—was quite unsuited for the large charges fired from heavy 
rifled guns. The subject had been under the consideration of a special 
committee, whose experiments had led to the recommendation of a powder 
known as “ pellet ” powder, the grains of which were exactly uniform in 
size and shape. This pellet powder was, however, never issued in any 
large quantity, though nominally adopted into the service for heavy guns. 
The introduction of the present service pebble powder, in 1870 (consisting 
roughly of cubes of about 0*5 in. edge), was a decided step in the right 
direction, but the experiments since carried out with the 38-ton and 80-ton 
guns have shown clearly that the size of even this comparatively large¬ 
grained powder must be further increased to render it suitable for the 
enormous charges fired from these pieces of ordnance. The methods of 
investigation, and the instruments employed for this purpose, I propose to 
describe in this paper, referring those who wish for detailed information 
on the question of powder to the papers which have appeared, from time to 
time, in these “ Proceedings,” and to the Eeports of the Committee on 
Explosives. 
The methods of investigation maybe divided into three sections:—(1) 
measuring the velocity of the projectile just after leaving the muzzle of the 
gun; (2) ascertaining the maximum pressure exerted by the powder gas on 
the bore of the gun at certain definite positions; and (3) measuring the 
velocity of the projectile at several successive points in its passage through 
the bore, and calculating therefrom the mean pressure exerted by the gas at 
these points. 
(1) The muzzle velocity is measured by means of a chronograph invented 
by Major Le Boulenge, of the Belgian artillery, which has almost entirely 
superseded the Navez-Lours* instruments, employed with so much success 
for many years; (2) the pressure at any point in the bore is recorded by a 
“ crusher gauge,” inserted in the gun at that point. I have placed these 
two instruments before (3) the Noble chronoscope (employed for measuring 
the velocity inside the bore), as they are much oftener and more generally 
used, having been adopted, both in this country and in India, for proving all 
cannon powder passed into the service. I shall commence, therefore, with 
