CAPTAIN NOBLE AND MR. F. A. ABEL ON FIRED GUNPOWDER. 221 
analyses of tlie F. G. residues. But the highest result furnished by pebble powder is 
nearly equal to, and that furnished by R. L. G. powder is not far below the highest 
number obtained with F. G. powder. 
4. As regards potassium monosulphide, the mean result in the case of pebble is 
very considerably higher than that furnished by R. L. G. powder, and more than four 
times the mean result given by F. G. powder. It is noteworthy, too, as indicative of 
the great and apparently uncontrollable irregularity in the amount of this product 
formed by the explosion of powders of normal composition in closed spaces, that the 
proportions of sulphide produced from pebble powder at the higher pressures were 
very small, and similar to those formed from F. G. powder at low as well as high 
pressures (except where none was found in the residues), and that in several instances 
very considerable quantities were formed from Pebble at densities ranging from 20 to 
60 per cent., some of them being indeed very much higher than that produced in the 
special experiment with sporting powder, in which extra precautions were adopted to 
guard against oxidation of sulphide. Then, in the case of R. L. G. powder, the pro¬ 
portions of sulphide found may be said to be intermediate between those produced 
from pebble and F. G., the amounts ranging from 2 to 10 per cent.; and the higher 
and lower proportions are indiscriminately distributed through the different residues 
obtained at low, high, and intermediate pressures. In no instance, either with pebble 
or R. L. G., was there a complete absence of sulphide, as in three instances, at the 
higher pressures, with F. G. powders. We feel bound again to lay stress upon the 
fact that there were no accidents of manipulation to account for these remarkable 
differences in residues furnished by powders of practically the same composition. 
5. One or two other points of interest present themselves in connexion with the 
potassium sulphate found in the residues from the three powders. Both in the pebble 
and F. G. residues, those obtained at the lowest and the highest densities differed very 
decidedly from the remainder in regard to the sulphate present, while the proportions 
in the residues obtained at the densities intermediate between those two extremes 
present comparatively slight differences in the case of both these powders. But the 
residues furnished by R. L. G. powder exhibit a very decided difference to the above ; 
the proportions of sulphate in those produced at the four lowest pressures (up to a 
density of 40) are high, and very similar in amount to those found in the majority of 
the F. G. powder-residues, while those in the residues produced at the six higher 
pressures are only from one-fourtli to one-half in amount of the others, some being 
similar to, and others still lower than those formed in the pebble powder-residues. 
On comparing the proportions of hyposulphite and sulphide in these R. L. G. residues 
with the sulphate, it will be seen that they vary as much among themselves in the 
residues where the proportion of sulphate is high as in those where it is small in 
amount. That the amount of sulphate produced by the explosion of this particular 
powder, even under the same conditions as regards pressure, was liable to considerable 
variation, is demonstrated by comparing the results of special examination of the residue 
