1879.] 



Researches on Explosives. 



137 



larger proportion of the products of combustion in the form of perma- 

 nent gases. This suggestion would also appear fully to explain the 

 fact alluded to in the authors' first paper, and to which they had 

 been led purely by experiment, namely, " that the variations observed 

 in the decomposition of gunpowder do not, even when very consider- 

 able, materially affect either its tension or capacity for performing 

 work." 



A comparison between different gunpowders, or a comparison between 

 gunpowder and other explosive agents cannot, therefore, as has been 

 proposed, be determined by a simple measurement of the correspond- 

 ing units of heat they evolve. 



Did such a law hold, the Spanish powder should have more than 50 

 per cent, advantage over the mining powder, but, as a matter of fact, 

 although not very widely different, the mining powder had the advan- 

 tage both in respect to the tension observed in a close vessel and to the 

 energy developed in the bore of a gun. 



As regards the actual temperature of explosion, the results of the 

 further experiments detailed in this paper leave little doubt, that the 

 temperature named in the authors' first memoir, viz., 2,200° C, is not 

 far removed from the truth for the principal powders with which they 

 then experimented. 



The slight differences or accidents which appear to give rise to not 

 inconsiderable variations in the ■ products of decomposition of gun- 

 powder are obviously nearly sure to give rise to corresponding varia- 

 tions in the temperature of explosion, and therefore this temperature, 

 even in one and the same powder, cannot be supposed to be always 

 identical. 



The authors then discuss the constants in the equation expressing 

 the relation between the tension of the products of explosion and the 

 volume these products occupy, as stated by them in their first memoir, 

 and give values of those constants, corrected from the analyses and 

 experiments made since the publication of that memoir, concluding 

 their remarks upon this part of their subject with a table which gives 

 in terms of the mean density of the powder products the tensions 

 which would exist in the bores of guns were perfectly dry powder of 

 normal composition suffered to expand, with or without production of 

 work. The tensions are expressed in kilogrammes per square centi- 

 metre, tons per square inch, and atmospheres. 



The authors call attention to the great utility of a table (XI) showing 

 the theoretic work which a charge of gunpowder is capable of effecting 

 in expanding to any value, v. The table given by them exhibits the 

 theoretic work for all necessary volumes of v, from v=l to v = d0, and 

 several illustrations of the use of the table are annexed. 



They continue : if it be desired to know the maximum work of a 

 given charge fired in a gun with such capacity of bore that the charge 



