VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. 105 



rods by which it is suspended, and the weight of the bullet remaining the same, 

 and this whatever the charge of powder may be that is made use of, and how- 

 ever it may differ in strength and goodness. 



According to this rule the velocities of the bullets in the several experi- 

 ments have been computed from the recoil; and by comparing them with the 

 velocities shown by the pendulum, we shall be enabled to judge of the accuracy 

 of this new method of determining the velocities of bullets. The consequence 

 of this comparison is, that several of the velocities, as determined by the two 

 methods, agree nearly together; and that several, on the contrary, disagree 

 very much, and that by differences which Mr. T. cannot account for. Hence 

 it ought to be inferred, that the new method is not generally to be relied on. 



Of a very accurate method of proving gunpowder. — All the eprouvettes, or 

 powder-triers, in common use are defective in many respects. Neither the abso- 

 lute force of gunpowder can be determined by means of them, nor the compa- 

 rative force of different kinds of it, but under circumstances very different from 

 those in which the powder is made use of in service. As the force of powder 

 arises from the action of an elastic fluid, generated from it in its inflammation, 

 the quicker the charge takes fire, the more of this fluid will be generated in any 

 given short space of time, and the greater of course will be its effect on the 

 bullet. But in the common method of proving gunpowder, the weight by which 

 the powder is confined is so great in proportion to the quantity of the charge, 

 that there is time quite sufficient for the charge to be all inflamed, even when 

 the powder is of the slowest composition, before the body to be put in motion 

 can be sensibly moved from its place. The experiment therefore may show which 

 of two kinds of powder is the stronger when equal quantities of both are con- 

 fined in equal spaces, and completely inflamed; but the degree of the inflamma- 

 bility, which is a property essential to the goodness of the powder, cannot by 

 these means be ascertained. » 



Hence it appears how powder may answer to the proof, such as is commonly 

 required, and may yet turn out very indifferent when it comes to be used in ser- 

 vice. And this, Mr. T. believes, frequently happens; at least he knows com- 

 plaints from officers of the badness of our powder are very common ; and he 

 would suppose that no powder is ever received by the Board of Ordnance but 

 such as has gone through the established examination, and has answered to the 

 usual test of its being of the standard degree of strength. But though the 

 common powder triers may show powder to be better than it really is, they 

 never can make it appear to be worse than it is; it will therefore always be the 

 interest of those who manufacture that commodity to adhere to the old method 

 of proving it. But the purchaser will find his account in having it examined in 

 a method by which its goodness may be ascertained with greater precision. 



vol. xv. P 



