TOL. XXV.] PHILOSOPHICAL TRANSACTIONS. 363 



An Experiment showing the Quantity of Air produced from a certain Quantity of 

 Gunpowder fired in common Air. By Mr. F. Hauksbee, F. R. S. N° 3 1 1 , 

 p. 2409. 



I took a fine glass tube about 36 inches long, the diameter of its bore about 

 three quarters of an inch : its upper orifice had a brass ferrel soldered to a 

 screw cemented on it, to which was screwed a cock : the lower or bottom part 

 was naked and open, wanting the bladder formerly used : near the upper part 

 of this tube within, was fixed a piece of cork, notched on its edges, to give the 

 greater liberty for the explosion to vent itself; the cork had a small cavity in its 

 middle, the better to receive and hold the gunpowder, which was let down on 

 it, through a small glass funnel, before the cock was screwed on. In this 

 manner the lower orifice was plunged under the surface of a vCvSsel of water ; 

 the cock being then screwed on and open, it was easy, by sucking at it with 

 one's mouth, to draw out the included air, by which the pressure of the external 

 air would raise the water in it to any determinate height : the tube was pre- 

 viously measured by an accurate cubical inch, and graduated on its outside by a 

 file. When the water had ascended to the designed mark, by the before- 

 mentioned means, the cock was turned, which suspended it there : then the 

 focus of a burning glass being cast on the powder, it soon fired, blowing the 

 water down violently ; but suddenly rising again, it rested so much below the 

 mark it stood at before firing, as was equal to the quantity of seeming air pro- 

 duced from it. The quantity of gunpowder used in this experiment, was one 

 exact grain weight; and I found the quantity of space the water had deserted, 

 just after the explosion, was nearly equal to the bulk of a cubical inch of gun- 

 powder, whose weight was 222 grains : so that 222 grains weight of the same 

 powder, as soon as fired, seems to produce something to possess the space of so 

 many cubical inches of air. Now, whether the space deserted by the water is 

 possessed by a body of the same weight and density, or is of the same quality 

 as common air, I dare not affirm; since an experiment I have lately made, to 

 try how much the heat produced by the explosion of the gunpowder, might 

 contribute to the size of the space dispossessed by the water, seems to conclude 

 it otherwise: for I found that when the gunpowder had been fired an hour, the 

 water had ascended about -/-g- of the whole deserted space, which was in length 

 about 24- inches, and was equal to about a cube inch in quantity, the space in 

 length being divided into 20 equal parts : at two hours after firing, it had 

 ascended near -^\ of the same. By this time I judged it might have become of 

 an equal degree of temperature with the outer air : but still continuing the 



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