128 
SHORT NOTES ON PROFESSIONAL SUBJECTS. 
77. 
Memorandum, dated 12. 7. ’70, relative to the progress of experiments by the 
Committee on Explosives since the preliminary report submitted to the Secretary 
of State for War in February, 1870 :— 
10 -inch Gun.-— The experiments of the committee since the above date have 
chiefly consisted in observing the effects of various kinds of powder, fired from a 
10-inch gun, in a similar manner to those fired from the 8-inch gun (as described 
in the preliminary report). 
A chronoscope constructed with eight discs has, however, been brought into use 
in place of the one with six discs, and observations of the velocity outside the 
muzzle have been taken with the Navez-Leurs apparatus. The committee have 
therefore obtained, in every round fired from the 10-inch gun, three different and 
independent series of indications of the action of the powder, viz. :— 
(1) The times occupied by the shot in passing over eight known intervals within 
the bore of the gun, by means of the eight revolving discs of Captain A. Noble’s 
chronoscope. 
(2) The velocity outside the bore at a distance of 50 yds. from the muzzle, by 
the Navez-Leurs chronoscope. 
(3) The pressure exerted by the gas at various points of the bore (usually five 
in number), as indicated by the crusher gauges described in the preliminary report. 
The pressures have also been calculated, as before, from the various rates of 
movement in the bore indicated on the Noble chronoscope, and it has been highly 
satisfactory to find that all the observations of pressure and velocity thus indepen¬ 
dently taken, have corroborated and confirmed one another in a remarkable degree, 
with the exception of certain discrepancies as regards pressure, which have been 
confined to quick-burning powders, and which the committee hope to explain in 
their detailed report. 
In several instances copper cylinders that have been compressed in the crusher 
by one round, have been used a second time to ascertain whether they would 
undergo further compression, and thus to learn to what extent the explosion of 
the charge acted like a blow on the gun. The importance of obtaining data on 
this point was strongly urged by the Superintendent Royal Gun Factories. The 
experiment has been tried ten times, in four of which the velocity was greater on the 
second occasion, and a further slight compression necessarily resulted. In three 
cases of the remaining six there was no alteration; in two cases one of the crushers 
showed a slight change. The only instance in which the crushers were decidedly 
more compressed without the velocity being increased, was in firing R.L.G. (the 
quickest powder used) with a rear axial vent. 
The committee have now fired 97 rounds from the 10-inch gun with pro¬ 
jectiles of 400 lbs. weight, and charges varying from 60 lbs. to 70 lbs. of powder, of 
different kinds and different degrees of density. 
Charge. 
Rounds. 
R.L.G-. 
lbs. 
60 
28 
Pellet . 
64 to 70 
20 
Prismatic, Russian. 
61 and 68 
7 
n Ritter’s . 
61 70 
7 
Pebble . 
70 
35 
n ... 
60 
2 )°° 
Total . 
97 
