On a new fulminating Mercurj. 2J 



j)0\vder is to be attributed to the rapidity of its combufiion ; 

 and a train of fevcral inches in length being confumed in a 

 ■fingle flalh, it is evident that its combuftion muft be rapid. 

 From the experiments of the 6th and 7th fe6lions, it is fuffi- 

 ciently plain that this force is reftrained to a narrow limit ; 

 both becaufe the block of wood charged with the mercurial 

 powder was more {battered than that charged with the gun- 

 powder, whilft the fand furrounding it was leaft diilurbed ; 

 and likewife becaufe the glafs globe withftood the explofion 

 of ten grains of the powder fixed in its centre : a charge I 

 have twice found fufficient to deflroy old piftol barrels, which 

 were not injured by being fired when full of the beft gun- 

 powder. It alfo appears, from the laft experiment, that tea 

 grains of the powder produced by ignition four cubical inches 

 only of air; and it is not to be fuppofed that the generation, 

 however rapid, of four cubical inches of air will alone ac- 

 count for the defcribed force; neither can it be accounted 

 for by the formation of a little water, which, as will here- 

 after be fhown, happens at the fame moment : the quantity- 

 formed from ten grains muft be fo trifling, that I cannot 

 afcribe much force to the expanfion of its vapour. The 

 fudden vaporifation of a part of the mercury feems to me a 

 principal caufe of this immenfe, yet limited, force; becaufe 

 its limitation may then be explained, as it is well knowa 

 that mercury eafily parts with caloric, and requires a tempe- 

 rature of 600 degrees of Fahrenheit to be maintained in 

 the vaporous ftate. That the mercury is really converted 

 into vapour, by ignition of the powder, may be inferred from 

 the thin coat of divided quickfilver, which, after the explo- 

 fion in the glafs globe, covered its interior furface ; and like- 

 wife from the quickfilver with which a tallow candle, or a 

 piece of gold, may be evenly coated, by being held at a fmall 

 diftance from the inflamed powder. Thefe fails certainly 

 reader it more than probable, although they do not demon- 

 ftiate, that the mercury is volatilifed; becaufe it is not un- 

 likely that n^.any mercurial particles are mechanically im- 

 pelled agaiiill the furface of the glafs, the gold, and the 

 tallow. 



As 



