the Source of the Heat excited by Friction . 83 
possibly have been furnished at the expence of the latent heat 
of the metallic chips. But, not being willing to rest satisfied 
with these trials, however conclusive they appeared to me to 
be, I had recourse to the following still more decisive experi- 
ment 
Taking a cannon, (a brass six-pounder,) cast solid, and rough 
as it came from the foundry, (see fig. 1. Tab. IV.) and fixing 
it (horizontally) in the machine used for boring, and at the 
same time finishing the outside of the cannon by turning, (see 
fig. 2. ) I caused its extremity to be cut off ; and, by turning 
down the metal in that part, a solid cylinder was formed, 7^ 
inches in diameter, and 9^ inches long; which, when finished, 
remained joined to the rest of the metal (that which, properly 
speaking, constituted the cannon, ) by a small cylindrical neck, 
only inches in diameter, and 3^ inches long. 
This short cylinder, which was supported in its horizontal 
position, and turned round its axis, by means of the neck by 
which it remained united to the cannon, was now bored with 
the horizontal borer used in boring cannon ; but its bore, which 
was 3.7 inches in diameter, instead of being continued through 
its whole length (9.8 inches) was only 7.2 inches in length; 
so that a solid bottom was left to this hollow cylinder, which 
bottom was 2 .6 inches in thickness. 
This cavity is represented by dotted lines in fig. 2 ; as also 
in fig. 3. where the cylinder is represented on an enlarged 
scale. 
This cylinder being designed for the express purpose of ge- 
nerating heat fry friction, by having a blunt borer forced against 
its solid bottom at the same time that it should be turned round 
its axis by the force of horses, in order that the heat accumu- 
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