VOL. XC.] PHILOSOPHICAL TRANSACTIONS. - 665 



and a ^-pound shot between 2 wads. The piece was destroyed from the trunnions 

 to the breech, and its fragments thrown 30 or 40 yards. The ball penetrated 5 

 inches into a block of wood, standing at about a yard from the muzzle of the gun; 

 the part of the swivel not broken, was scarce, if at all, moved from its original 

 position. 



Exper. 5. I oz. avoirdupois of the mercurial powder enclosed in paper, was 

 placed in the centre of a shell 4.4 inches in diameter, and the vacant space filled 

 with dry sand. The shell burst by the explosion of the powder, and the fragments 

 were thrown to a considerable distance. The charge of gunpowder employed to 

 burst shells of this diameter, is 5 oz. avoirdupois. 



Exper. 6. A sea grenade, 3.5 inches diameter, charged like the shell in the last 

 experiment, was burst into numerous fragments, by \oz. avoirdupois of the mer- 

 curial powder. The fragments were projected with but little force, and only to the 

 distance of 8 or 10 yards. The charge of gunpowder required for grenades of this 

 size, is 3 oz. 



Exper. 7. A sea grenade, of the same diameter as the last-mentioned, and 

 charged in the like manner, with -l oz. avoirdupois, or 574- gr., of the mercurial 

 powder, was split into 2 equal pieces, which were not thrown 10 inches asunder. 

 The report in the last 4 experiments was very sharp, but not loud in proportion. 



It seems, from the manner in which the swivel was burst, in the 4th experiment, 

 that a smaller charge would have been sufficient for the purpose. We may there- 

 fore infer, both from this instance and from the 2d experiment made with the gun, 

 in § 5, that any piece of ordnance might be destroyed, by employing a quantity of 

 the mercurial powder equal in weight to half the service charge of gunpowder; and 

 from the 7th and last experiment we may also conclude, that it would be possible 

 so to proportion the charge of mercurial powder to the size of different cannons, 

 as to burst them without dispersing any splinters. But the great danger attending 

 the use of fulminating mercury, on account of the facility with which it explodes, 

 will probably prevent its being employed for that purpose. 



In addition to the other singular properties of the fulminating mercury, it may 

 be observed, that 2 oz. inflamed in the open air, seem to produce a report much 

 louder than when the same quantity is exploded in a gun capable of resisting its 

 action. Mr. Cruickshank, who made some of the powder, by my process, remarked 

 that it would not inflame gunpowder. In consequence of which, we spread a mix- 

 ture of coarse and fine grained gunpowder on a parcel of the mercurial powder; 

 and after the inflammation of the latter we collected most, if not all of the grains of 

 gunpowder. Can this extraordinary fact be explained by the rapidity of the com- 

 bustion of fulminating mercury? or is it to be supposed, as gunpowder will not 

 explode at the temperature at which mercury is thrown into vapour, that sufficient 

 caloric is not extricated during this combustion? 



From the late opportunity I have had of conversing with Mr. Cruickshank, I 

 find that he has made many accurate experiments on gunpowder; and he has per- 



VOL. XVIII. 4 Q 



