the Force of Fired Gimpowder. 153 



raised twice by charges of 12 grains. That, in the 

 morning of the 3d of July, it was not raised by 12 

 grains nor by 13 grains ; but that 14 grains just raised 

 it. That, in the afternoon of the same day, two experi- 

 ments were made with 14 grains of powder, in neither 

 of which the weight was raised ; but that in another ex- 

 Deriment, in which 15 grains of powder were used, it was 

 raised with a moderate report. That, in the morning 

 of the 8th of July, in two experiments, one with 15I- 

 grains, and the other with 13 grains of powder, the weight 

 was raised with a loud report ; and in an experiment with 

 12 grains, it was raised with a feeble report. And lastly, 

 that in two successive experiments, made in the morn- 

 ing of the 17th of July, the weight was raised by charges 

 of 12 grains. 



Hence it appears that, under circumstances the most 

 favourable to the development of the force of gun- 

 powder, a charge (= 12 grains) filling j^^^ of the cavity 

 in which it is confined, on being fired, exerts a force 

 against the sides of the containing vessel, equal to the 

 pressure of 9431 atmospheres ; Vv'hich pressure amounts 

 to 141,465 lbs. avoirdupois on each superficial inch. 



Mr. Robins makes the initial, or greatest force of the 

 fluid generated in the combustion of gunpowder (namely, 

 when the charge completely fills the space in which it is 

 confined) to be only equal to the pressure of 1000 atmos- 

 pheres. It appears, however, from the result of these ex- 

 periments, that even admitting the elasticities to be as the 

 densities, as Mr. Robins supposes them to be, the initial 

 force of this generated elastic fluid must be at least 

 twenty times greater than Mr. Robins determined it ; — 

 for 3*0 Vo> the density of the elastic fluid in the experi- 

 ments in question, is to i, its density when the powder 



