CAPTAIN NOBLE AND MR. E. A. ABEL ON FIRED GUNPOWDER, 
123 
arrived at ; and before proceeding to the theoreticalc onsideration of the relation which 
should then exist between the tension and the density of the gases, we must direct 
attention to an important point — and that is, “ what loss of heat do the gases suffer 1 or, 
in other words, what proportion of energy in the powder is wasted by communication 
to the envelope in which the powder is fired, that is, to the barrel of the gunl” 
Every one is aware that if a common rifled musket be very rapidly fired, as may 
easily now be done by the use of breech-loading arms, the barrel becomes so hot that 
it cannot be touched with the naked hand with impunity, and, even with a field-gun, 
the increment of heat due to a few rounds is very considerable. 
As far as we know, the Count de Saint-Robert* made the first attempt to deter- 
mine the amount of heat actually communicated to a small arm. 
De Saint-Robert made three series of experiments with service rifled muskets, firing 
the ordinary charge of 4-5 grms. In the first series the muskets were loaded in the 
usual manner, in the second series the ball was placed near the muzzle, in the third 
the muskets were loaded with powder alone. The results at which De Saint-Robert 
arrived, and which are not difficult to explain, were, that the greatest quantity of heat 
was communicated to the musket when the ball w r as placed near the muzzle, that the 
quantity communicated, when no projectile at all was used, stood next in order, and 
that least heat was communicated when the musket was loaded in the usual manner. 
He further found that the quantity of heat communicated in this last case, with the 
powder and arm used, was about 250 gramme-units per gramme of powder fired. 
We found ourselves unable, however, to adopt Count de Saint-Robert’s important 
results for the guns and charges we have been considering, because conclusions derived 
from small arms could hardly be applied to large ordnance without modification. 
We therefore instituted the experiments described under Nos. 72 and 73. The gun, 
used was a 12-pr. B. L., and in the first experiment (No. 72) nine rounds were fired 
with If lb. (794 grms.) and a projectile weighing nearly 12 lb. (5330 grms.). 
Prior to the rounds being fired, arrangements were made for placing the gun, when- 
ever the series should be concluded, in a vessel containing a given weight of water ; and 
before the experiment was commenced the gun and water were brought to the same 
temperature, and that temperature carefully determined. 
After the firing the gun was placed in the water, and the rise of temperature due 
to the nine rounds determined. This rise was found to be equivalent to 236,834 grms. 
of water raised through 2°‘305 C., or the heat communicated to the gun by the com- 
bustion of 1 gramme of the charge was equal to 76 ‘4 gramme-units. 
Of course an addition has to be made to this number on account both of some loss of 
heat in the determination and of the unavoidable loss of heat between the rounds. 
The second experiment (No. 73) was made with 5 rounds of 1^- lb. (680-4 grms.) of 
the same powder with the same weight of projectile. The heat communicated to the 
gun by the five rounds was, when expressed in water, sufficient to raise 112,867 grms. 
* Traite de Thermodynamique (Turin, 1865), p 120. 
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