156 PHILOSOPHICAL TRANSACTIONS. [ANNO 1797- 



of the atmosphere ! For it is as 74- lbs. to 1 atmosphere, so 412529 lbs. to 55004 

 atmospheres.* 



* At first glance such an experiment, and such enormous consequences and inferences deduced from 

 it, may probably cause great amazement, and even astonishment, at the assertion of a force 53 times 

 greater than it has hitherto been accounted. But on recollecting himself, after a little reflection, the 

 real and calm philosopher will conclude that there must exist a fallacy in some part of this business, 

 when he considers that an elastic fluid, of a strength less than the 50th part of that above deduced, has 

 been found capable of producing all the experimented and known effects of military projectiles. If 

 these effects, when applied to calculations on unerring mathematical and physical principles, be due to 

 an elastic force of 1 000 atmospheres only, or little more, where and what are the effects that must result 

 from a force of 50 times as great ? These ought to be 7 or 8 or more times as much as are always expe- 

 rienced in real practice. Where then must the fallacy lie ? What can it be ? There may be several 

 causes of this illusion : but 2 especially suggest themselves to us, that seem fully adequate, to 

 have caused it. These are, the haviug measured the force of percussion by mere weight or pressure, to 

 which it is not comparable ; and the having supposed the small powder barrel to have broken in all parts 

 of its fracture at once, instead of being rent or torn in succession from end to end, as it appears was ac- 

 tually and really the case. From the known rapidity with which gunpowder inflames and expands; it is 

 manifest that its first action must be of the nature of a percussive force, especially when the opposing 

 weight or resistance is at some distance from the charge. Hence it must be in vain to expect that a 

 very heavy weight, when just lifted up by the elastic fluid, is to be considered as the measure of the 

 strength of that fluid : for the two forces, being of different kinds, are quite incommensurable to each 

 other, as much so as a surface and a solid are ; the smallest momentum exceeding and overcoming the 

 greatest pressure or mere dead weight ; and the least body let fall from above, on one arm of a lever, 

 moving or raising the other arm with the heaviest weight attached to it. The method of measuring the 

 initial force therefore, of the explosion of the powder, by the bare moving of the heavy opposing weight, 

 is a method that must be abandoned, as utterly unlit for the purpose. For nearly the same reason also we 

 must reject the other method of measuring the force, by comparing the bursting of the barrel with the 

 weight that by drawing breaks the rod of iron. For here again, not only is the iron drawn asunder by a 

 weight, which is the proper measure of its cohesive force or strength, while the small charged barrel is 

 acted on by the sudden or percussive force of the exploded powder ; but moreover, the particles of the 

 rod, at the fracture, or in the area of its section, do all yield and separate at the same time, while the 

 sides of the small barrel are torn asunder from end to end in all its parts in succession, or one after ano- 

 ther, in the manner that we easily tear a sheet of paper or piece of cloth, from end to end, which perhaps 

 our utmost strength could not accomplish if it were closed or twisted all together. That this was the 

 manner in which the barrel was broken and separated into 2 parts, we gather from the circumstances 

 which Count R. has so minutely and commendably described : had he not given the description in so 

 particular a manner, it might not have been so easy to detect the fallacy in this case. When cannon of 

 hard or cast iron break on firing them off, the fracture is made in all its parts at once, and the broken 

 pieces are projected and fly off with amazing velocities and to great distances, like so many balls, to the 

 great danger and sometimes the destruction of the spectators. But when a barrel of soft or tough metal 

 breaks, it is often after the manner of tearing or rending one part after another, and sometimes without 

 entirely separating the barrel in pieces, the force of the explosion being spent before this is effected. 

 Now that this was nearly the case in the present experiment, appears evident from the circumstances that 

 attended it. The 2 pieces of the barrel were separated from each oilier with a small velocity, and one of 

 them fell at the feet of the experimenter, standing near the machine, on purpose to watch and observe 

 the effects of the explosion : a circumstance that shows the successive tearing of the metal, and that the 

 force of the explosion was nearly quite spent just when the total separation was effected. And fortunate 

 was it for Count R. that this was the case j for had the pieces been blown asunder rapidly, and separated 

 with great velocity, he would probably not have escaped with life to make his report of these expert- 



