98 
CAPTAIN NOBLE AND ME. E. A. ABEL ON EIEED GTJNPOWDEK. 
Again, if there were any considerable decrement of pressure due to loss of heat, we 
should expect to find that the tension indicated would be higher when means are taken 
to insure rapidity of combustion. Such, however, is not the case ; for if reference be 
made to experiments 70 and 71, in which the charges were detonated by means of 
mercuric fulminate, it will be observed that the tension realized in these experiments 
was not materially higher than when the powder was fired in the ordinary way. 
We may cite also, in support of our view, some interesting observations made .during 
some earlier experiments in which charges of 10,500 grains (6'80 - 4 grms.) R L. G. and 
pellet powder were fired in chambers entirely closed with the exception of a vent ‘2 inch 
(5*08 millims.) in diameter. 
With the former powder the pressure realized under these circumstances was 36 ‘2 
tons per square inch (5513 atmospheres), with the latter 17 - 3 tons (2634 atmospheres). 
This large difference was due to the slower combustion of the pellet powder, upon the 
ignition of which, therefore, a large part of the products of combustion escaped by the 
vent before the whole of the powder was fired. When, however, the same powders were 
fired in vessels absolutely closed, the pressure indicated by the pellet powder was more 
than doubled (being 35 tons per square inch, or 5330 atmospheres), while the pressure 
indicated by the R. L. G. was practically the same (being 34 tons per square inch, or 
5178 atmospheres). 
From the experiments made by the Committee on Explosives, we are able to name 
approximately the absolute time that would be consumed in burning a charge of R. L. G. 
and of pebble, assuming that the powder be confined. With R. L. G. the time would 
be approximately -00128 second, with pebble approximately -0052 second. Of course 
these figures must vary greatly with different powders, as they depend not only on the 
nature, size of grain, and density of the powder, but also on the mode of ignition. They 
are interesting, however, as indicating the minuteness of the times involved and the 
relatively much larger time required for the decomposition of the pebble powder. It 
follows from the accordance of the pressures in the experiments just referred to, when 
powders differing so considerably in rapidity of combustion are fired in close vessels, that 
there is no very appreciable difference in pressure due to the longer time taken by the 
pebble powder to consume under these conditions. 
But the strongest, and at the same time an altogether independent, corroboration of 
our view is derived from the experiments upon the pressures exerted in the bores of guns 
by the action of the charge. 
Not only do these pressures, as obtained by observation, agree with most remarkable 
accuracy with the theoretical pressures deduced from the experiments in a close vessel, 
but, when in large guns the tensions due to very different charges are compared, not 
with reference to the position of the shot in the bore, but with reference to the mean 
density of the products of explosion, a most striking accordance is found to exist. We 
may therefore conclude that, where powders such as those we have experimented with 
are employed, there is but a trifling correction to be made in the observed pressure when 
