54 
CAPTAIN NOBLE AND ME. E. A. ABEL ON EIEED GUNPOWDER. 
He states that, from theory*, the quantity of gas should be comprised between 330 
and 350 volumes, and should amount in weight to three fifths of that of the powder. 
As regards the tension of the products at the moment of explosion, he accepts as 
tolerably correct the first series of Rumford’s experiments, and makes the pressure of 
gunpowder, when fired in its own space, about 23,000 atmospheresf. 
He further considers it possible that the presence $ of the vapour of water may add 
to the explosive force of gunpowder. He shares Rumford’s views as to the solid 
products being in the state of vapour at the moment of explosion ; he ascribes the high 
tension he assumes to the difference in the behaviour of vapours and permanent .gases 
when highly heated, and divides the phenomenon of explosion into two very distinct 
epochs : — the first when the solid products are in the state of elastic vapours, adding 
their tension to that of the permanent gases; the second epoch being when the perma- 
nent gases act alone, the vapours being condensed. 
In 1843 General Cavalli § proposed to apply to an experimental gun, at various 
distances from the bottom of the bore, a series of small barrels of wrought iron, arranged 
to throw a spherical bullet which would be acted upon by the charge of the gun while 
giving motion to its projectile. By ascertaining the velocities of these bullets, Cavalli 
considered that the tensions in the bore would be ascertained. This arrangement was 
carried out with a “ canon de 16,” under his own superintendence, in 1845; and from 
these experiments was deduced the theoretical thickness of the metal at various points 
along the bore. 
General Cavalli appears to have estimated at a very high rate the tensions realized 
in the bores of guns. He || considered that, with the Belgian “ brisante ” powder of 
1850, a tension of 24,000 atmospheres (158 tons per square inch) was actually realized, 
while in the less inflammable powders the tension was, he considered, under 4000 
atmospheres. 
In 1854 a Prussian Artillery Committee made a series of experiments to determine 
the pressure exerted by the powder in the bores of the 6- and 12-pounder smooth-bored 
guns. 
The plan adopted was a great improvement on that suggested by Cavalli, and was 
as follows : — 
In the powder-chamber a hole was drilled, and in this hole was fitted a small gun- 
barrel of a length of, say, 8 inches. Now, if the gun be loaded, and if in the small side 
barrel we place a cylinder whose longitudinal section is the same as that of the projec- 
tile, when the gun is fired, on the assumption that the pressure in the powder-chamber is 
uniform, the cylinder and the projectile will in equal times describe equal spaces, and 
* Piobeet, loc. tit. p. 291. f Loc. tit. p. 359. + Log. tit. p. 316. 
§ Revue de Technologie Militaire, tom. ii. p. 147. 
|| Cavalli, Gen., ‘ Memoire sur les Eclatements des Canons &c.,’ 1867, p. 83. 
Archiv fur die Offiziere der Koniglich Preussischen Ar tiller ie- und Ingenieur-Corps, tom. xxxiv. p. 2. 
Revue de Technologie Militaire, tom. i. p. 9, tom. ii. p. 152. 
