1879.] 



Researches on Explosives. 



139 



Such causes, affecting the energy realised, are then discussed, and 

 in particular the authors draw attention to the effect of retaining the 

 shot in its seat for a greater or less time, thus giving rise in the former 

 case to a more perfect and earlier combustion of the charge. They 

 cite experiments to show that from this cause alone differences of 

 energy, in guns having a calibre of 12 centims. of 13 to 14 per cent, 

 have been obtained. 



They add that in cases where the projectile has been removed for a 

 considerable distance from the charge, that is, when there is a con- 

 siderable air-space between the charge and the projectile, it has been 

 found that the energy developed in the projectile is materially higher 

 than that due to the expansion of the powder-gases through the space 

 traversed by the projectile, and the cause of this appears clear ; when 

 the charge is ignited at one end of the bore, and the ignited products 

 have to travel a considerable distance before striking the projectile, 

 these ignited products possess considerable energy, and a portion of 

 this energy will be communicated to the projectile by direct impact. 



The authors then compare the energies realised in a gun by the 

 various classes of powder which form the subject of their memoir, 

 and remark that none of the powders, in realised effect, vary more 

 from that generated by the normal Service Waltham Abbey powders, 

 than do occasional samples of these last ; a sufficiently curious result, 

 as already remarked, when the differences in the composition and the 

 great differences in the decomposition of the various powders are taken 

 into account. 



It is then pointed out that from the principles laid down it is possi- 

 ble, if the maximum chamber-pressure be known, to fix, very approxi- 

 mately, the position of the shot in the bore when the combustion of 

 the charge may practically be considered to be effected. 



Values of the "factor of effect " are then discussed, and the 

 authors conclude the memoir by observing that although the agree- 

 ment between the results of the long and laborious series of experi- 

 ments and calculations, which they now bring to a close, have far 

 exceeded the expectations they had formed when they commenced 

 their task, it would yet be idle to suppose that many of their deduc- 

 tions, referring as they do to temperatures and tensions far above the 

 range of ordinary research, will not require some subsequent correc- 

 tion. 



But, although certain minor points may, as the authors have said, 

 require considerable correction, they have little doubt that the main 

 theories upon which they insist, confirmed as they are by experiments 

 made, or facts obtained, under very great variety of circumstances, 

 may be accepted as, at any rate, close approximations to the truth. It 

 is satisfactory to find that the laws which rule the tensions and tem- 

 peratures of gases under ordinary circumstances do not lose their 



