242 Count Rumford’s Experiments to determine 
to express 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 it might be united 
more firmly to the plate of iron upon wiiich it reposes, this 
plate is furnished with a cylindrical projection p, 1 inch long 
and i-§- in diameter, which enters a hole made in the bottom of 
the stand to receive it. 
Fig. 5. is a view of the barrel from above, in which the pro- 
jecting screws, or rather cylinders, are seen, by which the he- 
misphere E, fig. 2. which closed the end of the barrel, was kept 
in its place. Two of these screws 1,2, 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 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 barrel at the mouth of the bore was worn away almost 
immediately, and even the flat surface of the hemisphere, not- 
withstanding it w r as of hardened steel and very highly polished, 
was sensibly corroded. This corrosion of the mouth of the 
