Intelligence and Miscellaneous Articles. 455 



form of the circuits be altered, the variation of the stream' of force 

 emanating from one of the currents in the direction of the other is 

 comprised in the terms d(TY) and d(TV) ; and in order to value 

 the action of a circuit upon itself it suffices to regard the factor U 

 as variable. We thus find again the known equations of electro- 

 dynamic induction-currents. 



The same mode of reasoning permits us to take account of the 

 changes which have happened in exterior magnets, and of the mag- 

 netization produced by currents on masses of soft iron. — Comptes 

 Mendusde VAcademie des Sciences, April 27, 1880, t. xc. pp. 981-984. 



EXPERIMENTAL RESEARCHES ON THE DECOMPOSITION OF SOME 

 EXPLOSIVES IN A CLOSED VESSEL; COMPOSITION OF THE 

 GASES FORMED. BY MM. SARRAU AND VIEILLE. 

 These researches were undertaken for the purpose of determin- 

 ing the conditions of the employment of gun-cotton in mines. 



Since the important improvements introduced by Mr. Abel into 

 the manufacture of gun-cotton, this explosive is prepared in homo- 

 geneous masses of determined form and density, it is kept without 

 danger in the wet state, and its explosive force, comparable with 

 that of dynamite, is much greater than that of gun-powder ; con- 

 sequently its use in mines affords great advantages. It presents, 

 however, an inconvenience in that its explosion produces mephitic 

 gases injurious to the workmen in the galleries. In fact its decom- 

 position gives rise to the formation of carbonic oxide. This can be 

 obviated by adding to the gun-cotton an oxidizer, such as a nitrate. 

 In this memoir we make a comparative study of the products 

 formed, the heat evolved, and the pressure developed by the ex- 

 plosion in a closed vessel, — 1st, of pure gun-cotton*; 2ndly, of a 

 mixture of equal parts of gun-cotton and nitrate of potass ; 3rdly, 

 of a mixture of 40 parts of gun-cotton and 60 of nitrate of am- 

 monia ; 4thly, of nitroglycerine ; and, 5thly, of ordinary mining- 

 powder f. We exhibit today the results of our study of the gases 

 formed during the explosion in a closed vessel. 



Some previous experiments having shown that the nature and 

 the composition of the gases depend on the conditions of their 

 production, and particularly on the pressure under which they are 

 formed, we operated upon gases collected in a closed test-tube, 



* The composition, by weight, of gun-cotton, deduced from organic 

 analysis, and verified by elementary analysis of the products of decompo- 

 sition, has led us to regard the products of the manufacture current at the 

 Moulin-Blanc works as a mixture of 3 eq. of trinitrated and 1 eq. of bi- 

 nitrated cellulose — 



3[C ia H 7 (K0 4 } 3 O 10 ] + C ia H 8 (NO,) a O 10 , 



corresponding to the rough formula 



C 48 H a9 N u 84 . 



t This powder consists, from its manufacture, of 62 parts saltpetre, 

 20 parts sulphur, and 18 charcoal. 



