148 PHILOSOPHICAL TRANSACTIONS. [ANNO 1797. 



peated firing. With the same charge, the recoil of a gun, and consequently the 

 velocity of its bullet, is greater after the gun had been heated by repeated firing 

 than when it is cold. The velocity of the bullet is considerably greater when the 

 cannon is fired off with a vent tube, or by firing a pistol charged with powder into 

 the open vent, than when the vent is filled with loose powder. The velocity of 

 2, or 3, or more, fit bullets, discharged at once from a piece of ordnance, com- 

 pared to the velocity of 1 single bullet discharged by the same quantity of powder, 

 from the same cannon, is greater* than it ought to be according to the theory. 

 Considerable quantities -J- of powder are frequently driven out of cannon and other 

 fire-arms unconsumed. The manner in which the smoke of gunpowder rises in 

 the air, and is gradually dissolved and rendered invisible, shows it to partake of 

 the nature of steam. But not to take up too much time with these general ob- 

 servations, I shall proceed to give an account of experiments the results of which 

 will be considered as more conclusive. 



Having found it impossible to measure the elastic force of fired gunpowder with 

 any degree of precision by any of the methods before- mentioned, I totally changed 

 my plan of operations, and instead of endeavouring to determine its force by causing 

 the generated elastic fluid to act on a moveable body through a determined space, I 

 set about contriving an apparatus in which this fluid should be made to act, by a de- 

 termined surface, against a weight, which by being increased at pleasure should at 

 last be such as would just be able to confine it, and which in that case would just 

 counterbalance and consequently measure its elastic force. The idea of this method 

 of determining the force of fired gunpowder occurred to me many years ago; but a 

 very expensive and troublesome apparatus being necessary in order to put it in exe- 

 cution, it was not till the year 1792, when, being charged with the arrangement of 

 the army of his most Serene Highness the Elector Palatine, reigning Duke of 

 Bavaria, and having all the resources of the military arsenal, and a number of very 

 ingenious workmen at my command, with the permission and approbation of his 

 most Serene Electoral Highness, I set about making the experiments which I shall 

 now describe: and as they are not only important in themselves, and in their results, 

 but as they are, I believe, the first of the kind that have been made, I shall be 

 very particular in my account of them, and of the apparatus used in making them. 



One difficulty being got over, that of setting fire to the powder without any 

 communication with the external air, by causing the heat employed for that pur- 

 pose to pass through the solid substance of the barrel, it only remained to apply 

 such a weight to an opening made in the barrel as the whole force of the generated 

 elastic fluid should not be able to lift, or displace J; but in doing this many pre- 

 cautions were necessary. For, first, as the force of gunpowder is so very great, 



* Very little greater 3 and that only on account of a small portion of powder more fired. — f Very 

 small quantities, in proportion to the whole charges. — J In this way of applying the force of the elastic 

 fluid, it is to be observed that its first impulse acts as a momentum or percussive force, to which the op- 

 posed weight can be no measure, nor can be compared. 



