THE ROYAL ARTILLERY INSTITUTION. 
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Any other density can be tried, if necessary, in order more satisfactorily to 
elucidate the allowability of increase in column of powder and projectile with 
increase of density. 
If equal columns of powder and projectile in all the guns give similar 
pressures, then the size of gun for any particular density of powder will be 
given by the length of the columns; but if not, a modification must be 
made according to the influence of the size of the bore on the pressure. In 
the latter case much light will be thrown on the relative values of big and 
small bores, especially if taken in connection with the known laws of the 
resistance of the air and the penetration of armour plates. 
In this manner we shall not only be able to say what the pressure is 
with varied charges, calibres, and densities of powder, but we shall be able, 
from the laws which may be established, to calculate with tolerable accuracy 
what will be the pressures with larger charges and bigger guns, and what 
density of powder is suitable for each. 
Lastly, having fixed certain densities which are to be manufactured, 
and what guns they are suitable for, we may, if thought advisable, make 
some experiments to determine what mixture of these densities would give 
better results with intermediate guns. 
This method of proceeding is founded on the supposition that density will 
not fail us, but it may not be all that we require. If it fail us, other 
methods of regulating and moderating the combustion of gunpowder might 
be tried. 
It is possible that with our heaviest guns we may have not only to search 
for the very best description of powder, but also for the very best description 
of gun. We can obtain some very good practical information to guide us 
in fixing what is the maximum pressure which it is safe to use; for, by firing 
the battering charges of our service guns in these experimental guns, we can 
note the pressure given, and adopt that as the maximum, which must not be 
exceeded in any new gun of similar construction.^ 
I am indebted to Mr. Bashforthf for the suggestion that a gun with a 
movable breech, on the plan proposed by me a year ago, would be the best 
means of carrying out these experiments. I may observe that of late I have 
very much improved its construction, my object being to allow the breech to 
move right away, so as not to disturb the elevation. In this way there 
would be no shock on the carriage, and, with a 15-inch gun firing at 15° 
elevation, the strain would be reduced from 1000 tons to 100 tons at most. 
This enormous reduction of strain would make it exceedingly well adapted 
to the small gun-boats now being constructed to carry heavy guns on 
platforms, which can be raised or lowered at will, on the plan invented by 
Mr. Bendel, of the firm of Sir W. G. Armstrong & Co. Eig. 11 shews 
an elevation of the gun. The breech is run home on the guide bars, and 
thus the hollow part of the curve is bridged over.f 
* Some very valuable information could also be obtained during these experiments by firing 
through the Bashforth chronograph, which would show the amount of steadiness given to varied 
lengths of projectile with varied velocities. 
f Professor of Applied Mathematics to the Advanced Class of Artillery Officers. 
J A small model 1 in. to a foot has been made for me at Elswick and fired. The shot was 11 ozs. 
and charge 2 ozs. of powder. The action was perfect. A leather gas check entirely prevented the 
escape of gas at the breech, and could be used over again. 
