144 PHILOSOPHICAL TRANSACTIONS. [~ANNO 1797. 



bores were in the same right line. The shorter of these tubes, which projected 

 1.3 inch beyond the external surface of the barrel, was closed at its projecting end, 

 or rather it was not bored quite through its whole length, -Aj. of an inch of solid 

 metal being left at its end, which was rounded off in the form of a blunt point. 

 The longer tube, which projected 1.7 inches beyond the surface of the barrel on 

 the other side, and which served for introducing the powder into the chamber, 

 was open ; but it could occasionally be closed by a strong screw, furnished with a 

 collar of oiled leather, provided for that purpose. The method of making use of 

 this instrument was as follows. The barrel being laid down, or held, in a horizon- 

 tal position, with the long tube upwards, the charge, which was of the very best 

 fine-grained glazed powder, was poured through this tube into the chamber. In 

 doing this, care must be taken that the cavity of the short tube be completely 

 filled with powder, and this can best be done by pouring in only a small quantity of 

 powder at first, and then, by striking the barrel with a hammer, cause the powder 

 to descend into the short tube. When, by introducing a priming-wire through the 

 long tube, it is found that the short tube is full, it ought to be gently pressed to- 

 gether, or rammed down, by means of the priming-wire, to prevent its falling back 

 into the chamber on moving the barrel out of the horizontal position. The short 

 tube being properly filled, the rest of the charge may be introduced into the 

 chamber, and the end of the long tube closed up by its screw. 



More effectually to prevent the elastic fluid, generated in the combustion of the 

 charge, from finding a passage to escape by this opening, after the charge was in- 

 troduced into the chamber, the cavity of the long tube was filled up with cold 

 tallow, and the screw that closed up its end, which was 4- an inch long, and but a. 

 little more than -^ of an inch in diameter, was pressed down against its leather 

 collar with the utmost force. The manner of setting fire to the charge was as 

 follows: a block of wrought iron, about 14- inch square, with a hole in it, capable 

 of receiving nearly the whole of that part of the short tube which projects beyond 

 the barrel, being heated red-hot, the end of the short tube was introduced into 

 this hole, where it was suffered to remain till the heat, having penetrated the tube, 

 set fire to the powder it contained, and the inflammation was thence communicated 

 to the powder in the chamber. 



The result of this experiment fully answered my expectations. The generated 

 elastic fluid was so completely confined that no part of it could make its escape. 

 The report of the explosion was so very feeble, as hardly to be audible: indeed it 

 did not by any means deserve the name of a report, and certainly could not have 

 been heard at the distance of 20 paces; it resembled the noise occasioned by the 

 breaking of a very small glass tube. I imagined at first that the powder had not 

 all taken fire, but the heat of the barrel soon convinced me that the 

 explosion must have taken place, and after waiting near half an hour, 

 on loosening the screw which closed the end of the long vent tube, the confined 

 elastic vapours rushed out with considerable force, and with a noise like that at- 



