SIR ANDREW NOBLE: RESEARCHES ON EXPLOSIVES. 
457 
Although for the elucidation of the laws which govern the transformation of the 
explosives when fired I have taken the densities named, I must point out that the 
requirements of the artillerist are confined to much narrower limits, the density, of 
course, varying considerably with the particular explosive used. 
In modern guns, for example, the chamber density varies from about 0‘310 to 
nearly 0'500, a good deal of the variation being due to the nature of the explosive 
used. It is hardly necessary to point out to artillerists that the chamber density is 
not the density which is responsible for the pressure developed in the gum 
The difference, which is frequently very considerable, is due to the time taken by 
the explosive to burn, and this depends upon the nature, form, and dimensions of the 
explosive, the expansion suffered by the nascent gases and the heat lost, due to work 
done upon the projectile and by communication of heat to the gun, and under these 
circumstances the pressure developed would, with full charges if compared with close 
vessel pressures, represent densities approximately between OT7 and (P23. 
The tables which are given in my late communication* to the Royal Society gave, 
for each particular density, the actual result observed. In the present paper the 
observations have been corrected by drawing curves to represent as nearly as possible 
the whole of the results, the actual observations, which are also given, showing in 
each case the departure from the curve. See Plates 10, 11, and 12. 
If reference be made to the tables, or to the plates just mentioned, it will be 
observed how wide are the differences, not only in the absolute volumes of the 
several gases, but in the variations with reference to the densities at which they were 
fired. 
Thus, for example, comparing Explosives III. and Y. (Norwegian 165 and Italian 
ballistites, see Plate 10), while in the former the carbon monoxide commences at the 
density 0'05 with a percentage volume of 38‘5, falling at a density of 0'45 to 22 per 
cent., the carbon dioxide commences with 13'3 per cent., rising rapidly to 31 per cent. 
In the latter explosive the CO commences at 20‘5 per cent, and falls slowly to 15 per 
cent., while the C0 2 commences a little over 26 per cent., rising also comparatively 
slowly to nearly 34 per cent. 
I may remark in passing that the Italian ballistite is the only explosive with which 
I have experimented, where, at low densities, the volume of C0 2 is greater than that 
of CO. 
But there are in these two explosives other remarkable differences. Thus, in the 
Italian ballistite, at a density of 0 - 05, the volume of methane, CH 4 , is a mere trace, 
about 0‘02 per cent., but it remains very much lower than is the case with any other 
explosive, being only 1'9 per cent, at the density of 0 - 45. With the Norwegian, on 
the other hand, the CH 4 , although the volume at commencement is only 0'4 per cent., 
is, at 0‘45 density, 11 per cent. 
Again, as might be expected from the large quantity of CH 4 found, in the case of 
* ‘ Phil. Trans.,’ A, vol. 205, pp. 221 to 223. 
3 N 
VOL. CCVI.—A. 
