VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. \4\ 



Struck with this great difference in the results of the computations of these two 

 able mathematicians, as well as with the subject itself, which appeared both curious 

 and important, I many years ago set about making experiments on gunpowder, 

 with a view principally of determining the point in question, namely, its initial 

 expansive force when fired; and I have ever since occasionally, from time to time, 

 as I have found leisure and convenient opportunities, continued these inquiries. In 

 a paper printed in the year 1781, in the 71st vol. of the Philos. Trans., I gave an 

 account of an experiment (No. 92), by which it appeared that, calculating even on 

 Mr. Robins's own principles, the force of gunpowder, instead of being lOOO 

 times, must at least be 1308 times greater than the mean pressure of the atmos- 

 phere. However, not only that experiment, but many others, mentioned in the 

 same paper, had given me abundant reason to conclude that the principles assumed 

 by Mr. Robins, in his treatise on gunnery, were erroneous ; and I saw no possibi- 

 lity of ever being able to determine the initial force of gunpowder by the methods 

 he had proposed, and which I had till then followed in my experiments. Unwilling to 

 abandon a pursuit which had already cost me much pains, I came to a resolution to 

 strike out a new road, and to endeavour to ascertain the force of gunpowder by 

 actual measurement, in a direct and decisive experiment. 



I shall not here give a detail of the numerous difficulties and disappointments I 

 met with in the course of these dangerous pursuits; it will be sufficient briefly to 

 mention the plan of operations I formed, in order to obtain the end I proposed, 

 and to give a cursory view of the train of unsuccessful experiments by which 

 I was at length led to the discovery of the truly astonishing force of gunpowder; — 

 a force at least fifty thousand* times greater than the mean pressure of the 

 atmosphere ! 



My first attempts were to fire gunpowder in a confined space, thinking, that 

 when I had accomplished this, I should find means, without much difficulty, to 

 measure its elastic force. To this end, I caused a short gun-barrel to be made, of 

 the best wrought iron, and of uncommon strength; the diameter of its bore was -f- 

 of an inch, its length 5 inches, and the thickness of the metal was equal to the 

 diameter of the bore, so that its external diameter was 2\ inches. It was closed at 

 both ends, by 2 long screws, like the breech-pin of a musket; each entering 2 

 inches into the bore, leaving only a vacuity of 1 inch in length for the charge. 

 The powder was introduced into this cavity by taking out one of the screws, or 

 breech-pins; which being afterwards screwed into its place again, and both ends of 

 the barrel closed up, fire was communicated to the powder by a very narrow vent, 

 made in the axis of one of the breech-pins for that purpose. The chamber, which 

 was 1 inch in length, and $ of an inch in diameter, being about half filled with 

 powder, I expected that when the powder should be fired, the generated elastic fluid, 



* It must seem strange to every pilosopher to be told that a force here said to be 50 thousand times 

 greater than that of the atmosphere, should produce effects no greater than are experienced in projectiles. 

 But more of this hereafter. 



