CAPTAIN NOBLE AND MR. F. A. ABEL ON FIRED GUNPOWDER, 
241 
Multiplying these energies by the factors of effect obtained from the proof of the 
powder and by the number of pounds in the charge, we should expect the energy 
realised from the 
70 lb. charge to lie between 3547*3 and 3633'8 foot-tons 
90 „ „ „ „ 5050-9 „ 5174-0 
100 „ „ „ 5841-7 ,, 5984-2 
Compare now these results with the actual experiments. On firing the above 
charges it was found that the 70 lb. charge gave to an 180 lb. shot a velocity of 
1694 feet per second, corresponding to a total energy of 3637 foot-tons, the 90 lb. 
charge a velocity of 2027 feet per second, or a total energy of 5133 foot-tons, and the 
100 lb. charge a velocity of 2182 feet per second, or an energy of 5940 foot-tons. 
In the 10-inch gun the number of expansions and the gravimetric densities were 
For the charge of 130 lb., number of expansions 4*294,gravimetric density 0*792 
„ „ 140 „ „ „ 4-050 „ „ 0-840 
Hence, as before, the maximum energies realisable are found to be 
For the 130 lb., 65'14 foot-tons per lb. (84*94—19*80) 
„ 140 ,, 66-84 „ „ „ (82-50-15-66) 
and multiplying by the same factors of effect, the total energy realised would lie 
between 6943*9 and 7113*3 foot-tons for the former, and between 7673*2 and 7860*4 
foot-tons for the latter charge. 
The actual results obtained with the 10-inch gun were for the 130 lb. charge a 
velocity of 1605 feet per second and an energy of 7158 foot-tons; for the 140 lb. 
charge a velocity of 1706 feet per second and an energy of 8092 foot-tons. With the 
235 lb. charge fired from the 11-inch gun the number of expansions was 4*214, the 
gravimetric density of the charge *770, while the energy realised was found to be 
13,066 foot-tons, or 55*6 foot-tons per pound of powder used. 
It will be noted that with the 8-inch gun (it happens that this calibre is the same 
as that of the gun used for powder proof, although the charges employed with this 
last are from one-half to one-third of those we are now discussing) the results realised 
are in each case very close to those predicted ; *84 as a factor of effect gives calculated 
results all but coincident with the high limit above given, but it must not be expected 
that results so closely accordant can always be obtained. Even when the same charges 
of the same powder and under precisely the same conditions are fired, considerable 
variations in energy sometimes have place. In the 10-inch gun, and with the larger 
charges of 130 and 140 lb., it will be observed that the realised energies are in both 
instances higher than the highest expected energy above given. In other words, for 
this gun and these charges a factor of from *85 to *86 should be used instead of the 
mdccclxxx. 2 i 
