1 1 8 Experiments to determine 



this opening ; but as it was necessary, in order to intro- 

 duce all the parts of this machinery, to make the draw- 

 ing upon a very small scale, it was not possible to ex- 

 press all the smaller parts with that distinctness which I 

 wished. The other figures which are added, in which 

 the parts are expressed separately, and upon a larger 

 scale, will, it is hoped, supply this defect. 



The stand, or support, as I have called it, upon 

 which the barrel was placed, is circular, and in order that 

 k might be united more firmly to the plate of iron upon 

 which it reposes, this plate is furnished with a cylindri- 

 cal projection^, I inch long and \\ in diameter, which 

 enters a hole made in the bottom of the stand to re- 

 ceive it. 



Fig. 5 is a view of the barrel from above, in which 

 the projecting screws, or rather cylinders, are seen, by 

 which the hemisphere E, Fig. 2, which closed the end of 

 the barrel, was kept in its place. Two of these screws 

 i, 2, are seen in the figures 2 and 4. The smaller 

 circle a b> Fig. 5, shews the diameter of a circular plate 

 of gold, which was let into the end of the barrel, being 

 firmly fixed to the iron with solder ; and the larger 

 circle c d represents a circular piece of oiled leather, 

 which was placed between the end of the barrel and the 

 hemisphere which rested upon it. 



The end of the barrel was covered with gold, in order 

 to prevent, as much as possible, its being corroded 'by 

 the elastic vapour, which, when the weight is not heavy 

 enough to confine it, escapes between the end of the 

 barrel and the flat surface of the hemisphere ; but even 

 this precaution was .not found to be sufficient to defend 

 the apparatus from injury. The sharp edge of the bar- 

 rel, at the mouth of the bore, was worn away almost 



