244 
CAPTAIN NOBLE AND MR. F. A. ABEL ON FIRED GUNPOWDER, 
A considerable number of rounds have been fired from small guns with mining 
powder. The particular powder of which the analysis is given in this memoir 
generated an energy differing but little from those obtained with R. L. G. under like 
conditions. Another sample of mining powder, however, differing from the first 
sample in containing a higher proportion of saltpetre, generated an energy higher than 
did any of the It. L. G. powders with which it was compared. This last powder, we 
may remark, was that which gave the pressure of 44 tons on the square inch when 
fired in an absolutely close vessel with a gravimetric density of unity. 
The Spanish spherical pellet powder generated rather less energy than did the 
mining powder, but in neither powder did the realised effect vary more from that 
generated by the normal service Waltham Abbey powders than do occasional samples 
of these last—a sufficiently curious result, as we have already remarked, when the dif¬ 
ferences in the composition and the great differences in the decomposition of the 
various powders are taken into account. 
The same remarks as to energy apply generally to the small-gTained powders. 
These, indeed, cannot be fired satisfactorily without special arrangements in very 
large charges, chiefly, among other reasons, from their tendency to cake under the 
pressure of the first ignited portion ; but for smaller charges the tables in this memoir 
alike apply. 
Of course, were similar weights of pebble, R. L. G., and F. G. fired in the same gun, 
the gun being supposed to be of small calibre, the energy realised by the F. G. 
would be greater than that realised by R. L. G., and still greater than that realised by 
pebble, on account of its much more rapid combustion. The maximum pressures 
developed in the bore would correspond with the energies realised. 
When the maximum chamber pressure as well as the energy developed by a given 
charge in a given gun are known, we are able from Table X. to fix very approxi¬ 
mately the position of the shot in the bore when the combustion of the charge may 
practically be considered to be effected. Thus, if with a given energy in the projectile 
it is found that the maximum chamber pressure is 3118 atmospheres (20'46 tons on 
the square inch), we learn from Table X. that this tension corresponds to a density of 
the products of combustion of 70 ; and hence the charge may be supposed to be prac¬ 
tically consumed when the projectile is in such a position in the bore that the products 
have this mean density. Again, if the observed pressure was 2400 atmospheres 
(1573 tons per square inch), the same table shows us that, when this pressure is 
reached, the position of the projectile in the bore corresponds to a density of charge 
of 'GO. 
with a velocity higher than its own, and for some short distance it appears to us probable that its velocity 
may be receiving an appreciable increase. As corroborative of our views, we may note the great indications 
of pressure upon gas-checks on the projectiles after these last are released from the support of the bore. 
Also the fact that when muzzle velocities calculated from data measured inside the bore were compared 
with those calculated from data measured outside, the latter were in all cases somewhat higher. 
