VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. Ill 



weight of the bullet, and compute the velocities from the reciprocal sub-tripli- 

 cate ratio of the quantity (b -+■ ip) in each experiment, there then results a 

 pretty near agreement between the actual and computed velocities in 5 out of the 

 8 experiments compared ; but in the other same 3 faulty ones, as before, the dif- 

 ference is still very great. 



Of an attempt to determine the explosive force of aurum fulminans, or a com- 

 parison between its force and that of gunpowder. — Mr. T. having provided him- 

 self with a small quantity of this wonderful powder, he endeavoured to asser- 

 tain its explosive force by making use of it instead of gunpowder for discharging 

 a bullet, and measuring, by means of the pendulum, the velocity which the 

 bullet acquired ; and concluding, from the tremendous report with which this 

 substance explodes, that its elastic force was vastly greater than that of gun- 

 powder, he took care to have a barrel provided of uncommon strength, on pur- 

 pose for the experiment. Its length in the bore was 13.25 inches, the diameter 

 of the bore 0.55 of an inch, and its weight 7 lbs. 2 oz. This barrel being 

 charged with -fa of an ounce (= 27-34 grains) of aurum fulminans and 2 leaden 

 bullets, which, together with the leather that was put about them to make them 

 fit the bore without windage, weighed 427 grains ; it was laid upon a chafing- 

 dish of live-coals, at the distance of about 10 feet from the pendulum, and 

 against the centre of the target of the pendulum the piece was directed. After 

 some minutes the powder exploded, but with a report infinitely less than what 

 was expected, the noise not greatly exceeding the repoi t of a well-charged wind- 

 gun. The bullets struck the pendulum nearly in the centre of the target, and 

 both of them remained in the wood : and Mr. T. found, on making the calcu- 

 lation, that they had impinged against it with a velocity of 428 feet in a 

 second. 



If we now suppose that the force of aurum fulminans arises from the action 

 of an elastic fluid generated from it in the moment of its explosion, and that the 

 elasticity of this fluid, or rather the force it exerts on the bullet as it goes on to 

 expand, is always as its density, or inversely as the space it occupies ; then, from 

 the known dimensions of the barrel, the length of the space occupied by the 

 charge (which in this experiment was 0.47 of an inch), and the weight and 

 velocity of the bullets, the elastic force of this fluid at the instant of its genera- 

 tion may be determined : and on making the calculation on these principles, Mr. 

 T. found that its force was 307 times greater than the mean elastic force of 

 common air ; and consequently was but about the 5 th or Oth of the strength of 

 gunpowder. 



Of the specific gravity of gunpoiuder. — To determine the specific gravity of 

 gunpowder, Mr. T. used the following method. A large glass bucket, with a 

 narrow mouth, being suspended to one of the arms of a very nice balance, and 



