280 Prof. Challis on Newton's "Foundation of all Philosophy" 



A comparison of these results shows at first sight that, on the 

 whole, the products of combustion of powder are little dependent 

 on the manner in which the combustion takes place. But that the 

 composition of the powder has a great influence, is seen from 

 the fact that in Bunsen's powder, which contains much nitre, 

 nearly 4 per cent, of this substance are found in the residue ; 

 while, on the other hand, in the residue of the ordnance powder, 

 which contains less nitre, almost 7 per cent, of sulphur and 

 charcoal are separated unburnt. The influence of the compo- 

 sition on the nature of the products of combustion is still more 

 surprising. Where the reducing body preponderates, the com- 

 bustion of the carbon is more imperfect. Whereas the gases 

 of sporting-powder only contain 3 per cent, of carbonic oxide, 

 the gas from ordnance powder contains nearly 10 per cent. The 

 quantity of hydrogen and of marsh-gas increase in the same 

 direction, so that the ordnance-powder gas contains nearly 

 20 per cent, of combustible gases. Hence it is not surprising 

 that the gases of ordnance powder, as well as those of gun-cotton, 

 may be ignited, as direct experiment showed, by a glimmering 

 piece of wood. 



There might apparently be no difficulty, from the results of 

 these analyses, in arriving at a right composition of powder ; yet 

 in this respect practice prefers its own empirical path. But in 

 any case the results obtained serve as an additional proof of the 

 inaccuTacy of the view which prevails in many chemical text- 

 books and in almost all artillery institutions, — that powder must 

 decompose, in burning, into sulphide of potassium, carbonic acid, 

 and nitrogen. If practice has no other reason for the composi- 

 tion of powder than the possibility that these products may occur, 

 it is certainly allowable to attempt to prove experimentally that 

 the products of combustion, even under the circumstances which 

 prevail in practice, can never be formed alone, and that, indeed, 

 one of them — sulphide of potassium — in many cases is not formed 

 at all. 



\l XXXIX. On Newton's "Foundation of all Philosophy: 3 

 By Professor Challis, M.A., F.R.S., F.R.A.S.* 



IN the Third Book of the Principia, under the head of " Regula 

 Tertia Philosophandi," Newton concludes the statement of 

 certain views respecting the ultimate qualities of bodies by say- 

 ing, "Et hoc est fundamentum philosophise totius." An asser- 

 tion of this kind, coming from such an authority, and made so 

 emphatically, may well excite an inquiry as to what is its precise 



* Communicated by the Author. 



