CAPTAIN NOBLE AND MR, F. A. ABEL ON FIRED GUNPOWDER. 
243 
chamber in as clear a light as possible, the following experiments were made. Four 
projectiles for a 12-centimetre B. L. gun were manufactured of precisely the same weight, 
and which differed from one another in the following respect only : that two of these 
were fitted with a rotating gas-check of such a form that a high pressure would be 
necessary to force the projectile into the bore ; the two others being fitted with gas- 
checks of a form such that a comparatively feeble pressure only would be requisite. 
The copper surfaces in contact with the bore were the same in each case. 
Two rounds, one with each form of gas-check, were then fired with a charge of 
7 lb. of B, L. G. powder, every condition, except as noted, being precisely the same ; 
the velocities with the two forms were respectively 1609 feet per second and 1512 feet 
per second, giving rise to 82’04 and 72‘44 foot-tons per lb. of powder. The chamber 
pressures were respectively 15‘2 and 12‘0'"' tons per square inch. Two further rounds 
were then fired with charges of lb. R. L. G., when velocities of 1644 and 1544 feet 
per second, or energies per lb. of 7 9'9 4 and 70'51 foot-tons were respectively obtained, 
the chamber pressures in this case being 16’4 and 14 - 1 tons per square inch. 
These experiments prove in the most complete manner that although there may be, 
and doubtless is, some difference in the amount of friction due to the employment of 
lead or copper as the driving or rotating material, that difference is perfectly insigni¬ 
ficant when compared to the alteration in energy due to the projectile being more or 
less retained in its initial position, and thus permitting the powder to be consumed 
earlier and in a more complete manner. 
In cases where the projectile has been removed for a considerable distance from the 
charge, that is, when there is a considerable air space between the charge and the 
projectile, it has been found that the energy developed in the projectile is materially 
higher than that due to the expansion of the powder gases through the space traversed 
by the projectile, and the cause of this appears to us clear. When the charge is ignited 
at one end of the bore and the ignited products have to travel a considerable distance 
before striking the projectile, these ignited products possess considerable energy, 
and a portion of this energy will be communicated to the projectile by direct impact. 
With the great lengths of charges used in the larger guns of the present day, some 
action of this sort doubtless, under ordinary circumstances, frequently happens, thus 
giving rise to somewhat more energy in the projectile than that due to the expansion 
of the gases from their initial density in the powder chamber to their final density 
when the projectile reaches the muzzle of the gun.t 
* The figures given denote the pressures on the bottom of the chamber and the base of the projectile 
respectively. The pressures are given as observed, but that on the base of the projectile requires an 
addition not generally made in actual practice. 
t As bearing npon the energy which is usually assigned to a projectile, we may remark that it is 
customary in correcting the measured to the muzzle velocity to assume that the loss due to the resistance 
of the air has accrued from the instant the shot quitted the muzzle. But, especially with the large 
charges and high-muzzle pressures now employed, we believe this rule should be greatly modified. 
For a considerable distance from the muzzle of the gun the projectile will be moving in an atmosphere 
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