130 Capt. Noble and Mr. F. A. Abel. [May 29, 



in experiments 40, 42, and 47, was not due to accident in the mani- 

 pulations, and that, in those residues in the general series of analyses 

 which were found to contain large quantities of hyposulphite (as in 

 six out of the nineteen experiments with pebble and R.L.G. powder, 

 and eight out of the nine with F.G. powder) the greater proportion 

 at any rate, of that hyposulphite existed in those particular residues 

 before their removal from the explosion- vessel. 



In experiments which the authors have instituted with a sample of 

 sporting powder and one of mining powder, the following course of 

 proceeding was adopted for the removal of the solid residue from the 

 explosion-vessels, and its preparation for analysis. Distilled water, 

 which had been freed from air by long-continued boiling, was siphoned 

 into the explosion-vessel when the latter had cooled, so that air was 

 never allowed to come into contact with the solid residue. When the 

 cylinder was thus quite filled with water it was closed, and set aside 

 for sufficient time to allow the residue to dissolve completely. The 

 solution was then decanted into bottles freed from oxygen, which were 

 quite filled with the liquid and carefully sealed up until required for 

 analysis. 



The residues of the two experiments in which these special precau- 

 tions were adopted to guard against the possible accidental formation 

 of hyposulphite were found to contain respectively 4 and 6 per cent, of 

 that substance. In the series of experiments with pebble powder 

 there were three, in that with R.L.G. powder four, while in that with 

 F.G. powder there was one, of which the residues contained propor- 

 tions closely similar to those furnished by these two special experi- 

 ments, there being no peculiarity in those seven experiments nor any 

 attendant circumstances which could be assigned as a possible reason 

 why the proportions of hyposulphite in those cases should be so much 

 lower than in the other experiments with the same powders carried 

 out under the same conditions. The authors, therefore, cannot but 

 conclude that the production of a small or of a larger proportion of 

 hyposulphite (whether as a primary or secondary product, but before 

 the explosion-vessel is opened) is determined by some slight modifica- 

 tion of the conditions attending the explosion itself. 



The sporting powder (Curtis and Harvey, No. 6) used by the 

 authors for the purpose of comparing the results of explosion with 

 those of the military powders used in these researches, did not differ 

 very widely in composition from these ; the composition of the char- 

 coal which it contained was intermediate between those contained in 

 the R.F.G. and F.G. powders. No striking points of difference were 

 exhibited between the proportions of the gaseous and solid products 

 Avhich it furnished, and those obtained with the four Service powders 

 used. With the mining powder employed the case was very different. 

 This powder presented very important differences in composition from 



