144 Experiments to determine 



The barrel being -rendered unfit for further service by 

 the bursting of its vent tube, an end was put to this set 

 of experiments. 



In order that a clear and satisfactory idea may be 

 formed of the results of these experiments I have drawn 

 the Fig. n, Plate VI., in which the given densities of 

 the generated elastic fluid, or (which amounts to the 

 same thing) the quantities of powder used for the 

 charge, being taken on the line A B, from A towards B, 

 the corresponding elasticities, as found by the experi- 

 ments, are represented by lines perpendicular to the line 

 A B at the points where the measures of the densities 

 end. 



As the irregularities of the dotted line A C are owing, 

 no doubt, merely to the errors committed in making 

 the experiments, these irregularities being removed, by 

 drawing the line A D in such a manner as to balance 

 the errors of the experiments, this line A D, which must 

 necessarily be regular, will, by bare inspection, give 

 us a considerable degree of insight into the nature of 

 the equation which must be formed to express the rela- 

 tion of the densities to the elasticities ; the discovery of 

 which was one principal object of these experimental en- 

 quiries. 



Putting the density = x and the elasticity =y, the line 

 A D will be the locus of the equation expressing the 

 relation of AT to_y; and had Mr. Robins's supposition 

 that the elasticity is as the density been true, x would 

 have been found to be to y in a constant (simple) ratio, 

 AD would have been a straight line, and A E 

 would have been the position of this line, had Mr. 

 Robins's determination of the force of fired gunpowder 

 been accurate. 



