352 
THE 80-TON GUN. 
considered as most suitable to the calibre. An inspection of table C 
will show that, on the whole, the cubes having a 1‘7-in. edge and 
re-worked from L.G. powder proved the best. For the full explanation 
of column 8, I must refer to p. 133 of the truly admirable treatise on 
“ Fired Gunpowder,” recently published in the “ Philosophical Trans¬ 
actions of the Royal Society ” by Capt. A. Noble, of Elswick, and 
Professor Abel—a treatise which forms a distinct step in advance in the 
science of gunnery. Captain A. Noble there gives most comprehensive 
explanations of the action of gunpowder in the bore of a gun, and 
shows how to compute the work actually performed by the conversion 
of the solid into gas. This work is calculated by Capt. Jones in column 8, 
and column 9 gives the amount realised, which is obtained from the 
vis viva of the shot on leaving the muzzle. The difference is occasioned 
by the heating of the gun and projectile, the friction, the escape through 
the vent, and the work done in expanding the gas-check. This last 
loss, however, is far more than compensated by the saving of escape 
round the projectile. Column 10 gives the amount of work got out of 
every pound of powder. The greater the disproportion between the 
weights of cartridge and shot, other things being equal, the more work 
will be obtained from each pound of the charge. Column 11 gives the 
ratio of pressure to work realised. In considering this column it must 
be borne in mind specially that the relation will be represented by an 
ascending curve—that is, that as the velocity increases, a greater incre¬ 
ment of pressure is required to produce a constant increment of 
velocity. 
Column 12 gives the per-centage of theoretic effect actually realised, 
being the ratio between columns 8 and 9. Column 13 is the energy 
(= -| vis viva) of the shot on leaving the gun, and is of course identical 
with the work realised; while column 14 gives the calculated energy 
of the shot at a range of 1000 yds., the difference being the loss 
occasioned by the resistance of the air. 
Columns 15 and 16 are given to suit the formula for penetration put 
forward by Major W. H. Noble, R.A., who considers that, other things 
being equal, the resistance offered by armour varies with the first 
power of the shot's diameter. 
The powder consisting of 1‘7-in. cubes of re-worked L.G. also estab¬ 
lished a clear superiority when shot weighing 1460 lbs. Were employed. 
(See rounds 18, 19, 20.) These were fired ill order to connect the 
experiments in the 14^-in. calibre with those to be carried out after 
boring up the gun to 15 ins. 
I do not propose in this paper to enter at all upon the question of 
rifling. The 80-ton gun in its 14^-in. calibre was rifled with eleven 
grooves, having a spiral which increased from 0 at the breech to 
1 turn in 35 calibres at the muzzle, the curve being a parabola. This is 
precisely similar to the system adopted in the 11-in., 35-ton, and 38-ton 
guns of the service, in which it has given good results; and as firing 
into the Proof Butt yields but scanty information on this particular 
subject, nothing would be gained by enlarging on it in connection with 
the experiments hitherto carried out with the 80-ton gun. 
Turning back for a moment to the problem set by the Admiralty at 
