Benjamin Thompson (Count Rumford). 1798. "Heat is a Form of Motion: An Experiment in Boring Cannon." Philosophical Transactions Vol. 88.]

"Taking a cannon (a brass six-pounder) cast solid, and rough as it came from the foundry, and fixing it (horizontally) in the machine used for boring, and at the same time finishing the outside of the cannon by turning, I caused its extremity to be cut off; and, by turning down the metal in that part, a solid cylinder was formed, 7 3/4 inches in diameter, and 9 8/10 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. . . . "

"The cylinder, revolving at the rate of about thirty-two times in a minute, had been in motion but a short time when I perceived, by putting my hand into the water and touching the outside of the cylinder, that heat was generated; and it was not long before the water which surrounded the cylinder began to be sensibly warm.

At the end of one hour I found, by plunging a thermometer into the water in the box (the quantity of which fluid amounted to 18.77 pounds avoirdupois, or 2 ¼ wine gallons) that its temperature had been raised no less than 47 degrees; being now 107° of Fahrenheit's scale.... At the end of two hours, reckoning from the beginning of the experiment, the temperature of the water was found to be raised to 178 °F.

At two hours twenty minutes it was 200 °F; and at two hours thirty minutes it actually boiled!

It would be difficult to describe the surprise and astonishment expressed in the countenances of the bystanders, on seeing so large a quantity of cold water heated and actually made to boil without any fire...

By meditating on the results of all these experiments we are naturally brought to that great question which has so often been the subject of speculation among philosophers; namely.

What is heat? Is there any such thing as an igneous fluid? Is there anything that can with propriety be called caloric?

. . .  It is in hardly necessary to add that anything which any insulated body, or system of bodies, can continue to furnish without limitation cannot possibly be a material substance: and it appears to me to be extremely difficult, if not quite impossible, to form any distinct idea of anything, capable of being excited and communicated, in the manner the heat was excited and communication in these, except it be MOTION."