Scientists’ thought that heat acted like a fluid, it flowed from one object to another. Heating a pan on the stove, it seemed that the heat flowed from the stove into the pan and spread out to heat all parts of the pan. In the eighteenth century scientist mistakenly thought that heat was an invisible fluid called “caloric”, this is where we get the term calories that you see on food labels.
This idea was wrong, if you rub your hands together, they will warm up. But no fluid moved between your hands, what actually happened was that the friction of one hand rubbing off the other caused the increase in temperature.
Benjamin Thompson (Count Rumford) an American, was working in Germany boring cannons for the army, he noticed the process generated a great amount of heat. The thinking of the time was that if heat was a fluid then a cannon should contain a certain amount of this fluid and sooner or later, it would run out.
He carried out experiments to find out the amount of heat generated when drilling a canon. He found that the amount of heat generated does not depend on the amount of material being drilled. As long as the drill was rotating, the cannon would produce heat. Count Rumford’s experiments with canons lead to the idea that
“Heat had something to do with motion”.