I2O Experiments to determine 



experiment by which the weight was ascertained, which 

 was just able to counterbalance the pressure of the 

 generated elastic fluid, was in no wise vitiated, either by 

 the increased diameter of the bore at its extremity or by 

 any corrosion of the hemisphere itself; for as long as 

 the bore retained its form and its dimensions in that 

 part to which the efforts of the elastic fluid were con- 

 fined, that is, in that part of the bore immediately in 

 contact with the lower part of the stopper, the experi- 

 ment could not be affected by any imperfection of the 

 bore either above or below. 



In the figures i and 4 this stopper is represented in 

 its place, and Fig. 6 shews the plan, and Fig. 7 the profile 

 of one of these stoppers of its full size. Fig. 8 shews 

 a small, but very useful instrument, employed in intro- 

 ducing these stoppers into the bore, and more especially 

 in occasionally extracting them ; it resembles a common 

 cork-screw, only it is much smaller. 



In the figure (where it is shewn in its full size) it is 

 represented screwed into a stopper. Fig. 9 shews the 

 plan, and Fig. 10 a side view, of the full size, of the 

 hemisphere of hardened steel, by which the end of 

 the barrel was closed. In the figures 2 and 4. the barrel 

 is represented as being about half filled with powder. 



Presuming that what has been already said, together 

 with the assistance of the annexed drawings, will be 

 sufficient to give a perfect idea of all the different parts 

 of this apparatus, I shall now proceed to give an ac- 

 count of the experiments, which, from time to time, 

 have been made with it. And in order to render these 

 details as intelligible as possible, and to shew the results 

 of all these inquiries in a clear and satisfactory manner, 

 I shall first give a brief account of the manner in 



