inches in length, was introduced into the hole made to receive it in
the side of the cylinder, when the mercury rose almost instantly to one
hundred and thirty degrees.

"In order, by one decisive experiment, to determine whether the air
of the atmosphere had any part or not in the generation of the heat, I
contrived to repeat the experiment under circumstances in which it was
evidently impossible for it to produce any effect whatever. By means
of a piston exactly fitted to the mouth of the bore of the cylinder,
through the middle of which piston the square iron bar, to the end of
which the blunt steel borer was fixed, passed in a square hole made
perfectly air-tight, the excess of the external air, to the inside of
the bore of the cylinder, was effectually prevented. I did not find,
however, by this experiment that the exclusion of the air diminished in
the smallest degree the quantity of heat excited by the friction.

"There still remained one doubt, which, though it appeared to me to be
so slight as hardly to deserve any attention, I was, however, desirous
to remove. The piston which choked the mouth of the bore of the
cylinder, in order that it might be air-tight, was fitted into it with
so much nicety, by means of its collars of leather, and pressed against
it with so much force, that, notwithstanding its being oiled, it
occasioned a considerable degree of friction when the hollow cylinder
was turned round its axis. Was not the heat produced, or at least some
part of it, occasioned by this friction of the piston? and, as the
external air had free access to the extremity of the bore, where it came
into contact with the piston, is it not possible that this air may have
had some share in the generation of the heat produced?

"A quadrangular oblong deal box, water-tight, being provided with
holes or slits in the middle of each of its ends, just large enough to
receive, the one the square iron rod to the end of which the blunt steel
borer was fastened, the other the small cylindrical neck which joined
the hollow cylinder to the cannon; when this box (which was occasionally
closed above by a wooden cover or lid moving on hinges) was put into
its place--that is to say, when, by means of the two vertical opening
or slits in its two ends, the box was fixed to the machinery in such
a manner that its bottom being in the plane of the horizon, its axis
coincided with the axis of the hollow metallic cylinder, it is evident,