240 Count Rumford’s Experiments to determine 
of the whole apparatus made use of in these experiments. 
A. (fig. 1.) is a solid block of very hard stone, 4 feet 4 inches 
square, placed upon a bed of solid masonry, which descended 
6 feet below the surface of the earth. Upon this block of 
stone, which served as a base to the whole machinery, was 
placed the barrel B of hammered iron, upon its support C, 
which is of cast brass, or rather of gun-metal; which support 
was again placed upon a circular plate of hammered iron D, 
8 inches in diameter, and \ of an inch thick, which last rested 
upon the block of stone. The opening of the bore of the bar- 
rel (which was placed in a vertical position, and which was 
just x of an inch in diameter) was closed by a solid hemisphere 
E of hardened steel, whose diameter was 1.16 inch; and 
upon this hemisphere the weight F, made use of for confining 
the elastic fluid generated from the powder in its combustion, 
reposed. This weight, (which in some of the most interesting 
experiments was a cannon of metal, a heavy twenty-four pounder, 
placed vertically upon its cascabel) being fixed to the timbers 
G G which formed a kind of carriage for it, was moveable up 
and down; the ends of these timbers being moveable in grooves 
cut in the vertical timbers K K, which being fixed below in 
holes made to receive them in the block of stone, and above 
by a cross piece L, were supported by braces and iron clamps 
made fast to the thick walls of building of the arsenal. This 
weight was occasionally raised and lowered in the course of 
the experiments (in placing and removing the barrel), by 
means of a very strong lever, which is omitted in the drawing 
to make it less complicated. The barrel, a section of which is 
represented in fig. 2. of its natural size, is 2.78 inches long, 
and 2.82 inches in diameter, at its lower extremity, where it 
