140 Experiments to deter 7nine 



idea may be formed of the real force of this elastic fluid, 

 I have added a column in which its force, answering to 

 each charge of powder, is expressed in atmospheres. 



The numbers in this column were computed in the fol- 

 lowingr manner. The diameter of the bore of the barrel 

 at its muzzle being just \ of an inch, the area of its 

 transverse section is 0.049088 of a superficial inch; and, 

 assuming the mean pressure of the atmosphere upon i 

 superficial inch equal to 15 lbs. avoirdupois, this will 

 give 0.73631 of a pound avoirdupois, for that pressure 

 upon 0.049088 of a superficial inch, or upon a surface 

 equal to the area by which the generated elastic fluid 

 acted on the weight employed to confine it ; consequently 

 the weight expressed in pounds avoirdupois which meas- 

 ured the force of the generated elastic fluid in any given 

 experiment, being divided by 0.73631, will show how 

 many times the pressure exerted by the fluid was greater 

 than the mean pressure of the atmosphere. Thus in 

 the experiment No. 6, where the weight which measured 

 the elastic force of the generated fluid was = 504.8 lbs. 

 avoirdupois, it is ■o.^v's^gIt ^^ 685.6 atmospheres. And 

 so of the rest. 



I have said that the diameter of the bore of the bar- 

 rel made use of in the following experiments was just 

 \ of an inch at its muzzle^ and this is strictly true, as I 

 found upon measuring it with the greatest care ; but its 

 diameter is not perfectly the same throughout its whole 

 length, being rather narrower towards its lower end ; yet 

 the capacity of the barrel being known, and also the di- 

 ameter of the bore of its muzzle, any small inequalities of 

 the bore in any other part can in no wise afl^ect the re- 

 sults of the experiments, as will be evident to those who 

 will take the trouble to consider the matter for a mo- 



