PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 517 



we shall be forced to allow that only a fraction of the possible elastic 

 energy of the generated gases comes into play, and that therefore the 

 computed velocities sought (if loe have correctly determined the maximum 

 pressure) are very greatly in excess of the velocities actually observed, 

 and should probably exceed them a number of times. 



It is probable that further experiment would prove that contrary to 

 Piobert's opinion, the combustion of gunpowder must go on more rapidly 

 in the chamber of a gun, than under the circumstances in which it is most 

 easy directly to observe it. But it is not by any means probable that the 

 rapidity of burning is ever great enough to permit us to discard the con- 

 sideration' of time from among the elements which must enter into this 

 problem. On the contrary the pi'essures registered by Rodman's indicator 

 when rifle powder and large grained cannon powder are successively fired 

 in the same gun and with the same weight of projectile, show that the evo- 

 lution of gas in the second case is much less rapid than the first, and 

 observers who have witnessed the firing of the fifteen inch guns state that 

 the mammoth powder grains are visible in full combustion after leaving the 

 muzzle of the gun. 



Without a more extended examination of the subject than it has been 

 found practicable to introduce into the present article, (designedly brief) 

 we shotild not perhaps be justified in stating an absolutely definite conclu- 

 sion in regard to the maximum pressure which gunpowder is capable of 

 producing; but it seems impossible to reconcile the actually observed veloc- 

 ities of projectiles thrown by it, with any supposition which should place 

 this maximum at less than ten thousand atmospheres, or one hundred and 

 fifty thousand pounds per square inch. 



If we admit s'jch a maximum, however, we find ourselves on the other 

 hand, obliged to discredit, to a certain extent, the results of the very able 

 and elaborate investigation of Messrs. Bunsen and SchischkofF, and to sup- 

 pose that they have underestimated the volume of the generated gases or 

 the amount of the heat developed. In the specimen of powder examined 

 by them the charcoal was in unusually small proportion.^ This may have 

 produced a sensible effect upon their results, by leading to a larger pro- 

 duction of sulphuric acid and a smaller of carbonic. Still, after makino- 

 every reasonable allowance for this consideration, we find it impossible to 

 draw from their analysis a satisfactory explanation of the mechanical 

 effects which gunpowder actually produces, and it seems exceedingly desir- 

 able that their investigation should be repeated. 



One observation may here be made in regard to the allowance commonly 

 made in calculation, for the effect upon the velocity of projectiles, of the 

 windage of g-uns. In the table above, examples one, two and three are 

 similar in all respects except windage, to examples five, six, seven. The 

 computed velocities are, therefore, in the parallel cases, as they should be 

 almost exactly equal. But the actually observed velocities materially dif- 

 fer. No. 5 being greater by forty-seven than No. 1; No. 6 greater by 

 seventy-two than No. 2; and No. 7 greater by ninety-three than No. 3. 

 In the first set of examples the windage is about one-fortieth and in the 

 second one-forty-sixth. The higher observed velocities correspond to the 

 less windage. And it is observed that the effect on velocity of difference 



