CAPTAIN" NOBLE AND ME. F. A. ABEL ON FIEED G-UNPOWDEE. 
107 
To test, however, the behaviour of the residue for ourselves, we placed in one of 
Siemens’s gas-furnaces, the temperature, of which was estimated at about 1700° C., 
several crucibles containing powder-residue. The behaviour of the residue was in all 
cases the same ; at first there was a little spirting (probably due to escape of water), which, 
however, soon diminished, and in time the contents of the crucibles became perfectly 
quiet, but up to the end of the experiment only a very slight volatilization could be 
observed. In the case of three of the crucibles, two of which contained powder-residue, 
the other a mixture of potassium carbonate and liver of sulphur, when removed from 
the furnace after being exposed to the full heat for about a quarter of an hour, the 
volumes of the contents in the highly heated state were observed without difficulty. 
The contraction in cooling was evidently very great, especially at first. The contents 
set at a temperature of between 700° and 800° C., and when cool the expansion was 
measured by calibration with mercury. The first crucible gave an expansion of 77 - 8 
per cent, between 0°C. and 1700° C. ; the second (potass, carb. and liver of sulphur) an 
expansion of 93' 8 per cent. The third (powder-residue) gave a considerably higher rate 
of expansion, above 100 per cent. ; but we have not included the result, as, owing to the 
presence of a piece of platinum put in to test the temperature of the furnace, we were 
unable to make a very accurate measurement. 
Of course the expansions, under the conditions we have just named, cannot be strictly 
compared with those which would have place in a close vessel under the high tension 
we know to exist ; but they tend to confirm the results arrived at by a perfectly inde- 
pendent method. The experiments also show that, at a temperature approaching that 
developed by explosion, and under atmospheric pressure, the liquid products are still in 
that condition ; and our experiments so far confirm those of Bunsen aud Schischkofe to 
which we have alluded. 
E. OBSEEVED PEESSUEES IN THE BOEES OF GUNS. 
The data which we shall use for the discussion of the phenomena attending the com- 
bustion of gunpowder in ordnance are nearly entirely derived from the experiments 
carried on by the Committee of Explosives under the presidency of Colonel Young- 
husband, F.R.S. 
Two methods, of an entirely distinct nature, were employed by the Committee for the 
elucidation of the questions they had to consider. 
One method consisted in determining the tension of the gas at various points in the 
bore, by direct measurement. The other mode consisted in measuring the time at which 
the projectile passed certain fixed points in the bore, thence deducing the velocities 
from the seat of the shot to the muzzle, and finally obtaining, by calculation, the gaseous 
pressure necessary to generate the observed velocities. 
The apparatus used for determining the tension by direct measurement was the 
crusher-gauge, which we have already described ; that for ascertaining the velocity was 
a chronoscope specially designed for measuring very minute intervals of time. As the 
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