the Source of the Heat excited by Friction. 
101 
/ DESCRIPTION OF THE FIGURES (Tab. IV.) 
* 
Fig. l. shows the cannon used in the foregoing experiments, 
in the state it was in when it came from the foundry. 
Fig. 2. shows the machinery used in the experiments No. l, 
and No. 2. The cannon is seen fixed in the machine used 
for boring cannon. W is a strong iron bar, (which, to save 
room in the drawing, is represented as broken off,) which bar, 
being united with machinery (not expressed in the figure) 
that is carried round by horses, causes the cannon to turn 
round its axis. 
m is a .strong iron bar, to the end of which the blunt borer 
is fixed ; which, by being forced against the bottom of the 
bore of the short hollow cylinder that remains connected by 
a small cylindrical neck to the end of the cannon, is used in 
generating heat by friction. 
Fig. 3. shows, on an enlarged scale, the same hollow cylin- 
der that is represented on a smaller scale in the foregoing 
figure, it is here seen connected with the wooden box (g, h, 
i, k,) used in the experiments No. 3, and No. 4, when this 
hollow cylinder was immersed in water. 
P> which is marked by dotted lines, is the piston which 
closed the end of the bore of the cylinder. 
n is the blunt borer seen side- wise. 
d, e, is the small hole by which the thermometer was in- 
troduced, that was used for ascertaining the heat of the cylin- 
der. To save room in the drawing, the cannon is represented 
broken off near its muzzle; and the iron bar, to which the blunt 
borer is fixed, is represented broken off at m. 
