416 



Capt. Noble and Mr. F. A. Abel 



[June 18, 



As it was one of the principal objects of the authors to determine, 

 with as much accuracy as possible, not only the tension of fired gunpowder 

 when filling completely the space in which it was exploded, but also to 

 determine the law according to which the tension varied with the density, the 

 experiments instituted to ascertain these important points were both 

 varied and complete. The general results obtained are given in the 



annexed Table. 



TABLE IV. 



Showing the pressure corresponding to a given density of the products of 

 explosion of F. G., 2i. L. 6r., and. pebble powders, as deduced from actual 

 observation, in a close vessel* 



The determination of the heat developed by the explosion was also 

 made the subject of careful direct experiment, and, from the mean of 

 several closely concordant results, it was found that the combustion of a 

 gramme of the powders experimented with generated about 705 gramme- 

 units of heat. Bunsen and Schischkoff s assumption, that the specific 

 heats of the solid products remain invariable over the great range of 

 temperature through which they pass, is considered by the authors 

 untenable ; they have, however, deduced the temperature (about 3800 C.) 

 upon this hypothesis, both to facilitate comparison of their results with 

 those of Bunsen and Schischkoif, and to give a high limit, to which the 

 temperature of explosion can certainly not attain. 



The volume of solid products obtained from a gramme of powder is 

 fixed by the authors at about -3 cub. cent, at ordinary temperatures. 



A comparison is next instituted of the pressures actually observed to 

 exist in a close vessel with that calculated upon the assumption that, at 

 the moment of explosion, about 57 per cent, by weight of the products of 

 explosion are non-gaseous, and 43 per cent, in the form of permanent 

 gases. The relation between the pressure and the density of the pro- 

 ducts of combustion may be expressed by the following equation, 



^=const. x A-j (3) 



(a being a constant determined from the experiments) ; and a comparison 

 of the results is given in the following Table : 



