THE EOYAL ARTILLERY INSTITUTION. 427 
This result is entirely due to the use,, with these guns, of powder suitable 
only for smaller natures; for, if the guns are of the same construction and 
equally perfect manufacture, they will stand the same strains, and if the 
strains he the same throughout corresponding lengths of bore the initial 
velocities ought to be identical. 
It is true no doubt that in heavy guns the manufacture slightly deteriorates 
and the length in calibres has to be decreased; but these are reasons, if we 
wish to retain the velocity and at the same time not overstrain the gun, 
for making the law of pressure conform more instead of less closely to 
the strength of the gun as the various lengths of bore come under the 
influence of pressure. Any departure from this will result either in a loss 
of initial velocity, or cause an undue strain on the gun at some particular 
point. 
Perfection would be attained by having a special powder suitable for each 
nature of gun, but practically this cannot well be carried out. It is of all 
the more importance therefore that we should be provided with the fullest 
information on the subject, that we may be able to decide on some single 
powder suitable to all heavy guns, or on two or more sorts, the mixture of 
which will best answer the purposes required. 
To a great extent the Committee have, in their investigations, followed in 
the footsteps of Rodman, i.e ., they have endeavoured to obtain the pressures 
as they actually occur in the bore; and, like him, they have adopted two 
methods of doing so. 
Instead of his “ pressure gauge ” they use a “ crusher gauge,” a repre¬ 
sentation of which is given in Fig. 7 ; and, instead of estimating the pressure 
from the velocity of recoil of the gun, they do so from the velocity of the 
shot in the bore. 
For this last purpose they make use of a “ chronoscope,” invented by 
Captain Andrew Noble, late R.A., of Elswick. It notes the moments of 
passing various points in the bore by electric sparks which arise from the 
shot in its course causing projecting tools to shear wires in succession, as 
shown in Fig. 8. 
Their experiments have been confined to four kinds of powder, viz., 
R.L.G., prismatic, pellet, and a new sort called pebble. The following 
results have been obtained with the 8-incli gun by the chronoscope* 
Nature of powder. 
Charge. 
Initial 
velocity. 
Maximum 
pressure. 
lbs. 
f.s. 
tons. 
R.L.Gr..... 
30 
1324 
29-8 
Russian prismatic .. 
32 
1366 
20-5 
Service pellet . 
30 
1338 
17*4 
Pebble No. 5. Density 1 ) 
178 .5 
35 
1374 
15-4 
The pressure curves during the initial stages of the shot's motion are 
given in Fig. 9. 
* Preliminary Report, Committee on Explosives. 
