Doubtless it would have been considered a very unimportant question two hundred years ago, as to whether heat were an igneous fluid or a mode of motion. Perhaps not more than two or three men wrestled with the question for centuries before it was settled. By the masses of the people they were regarded as wasting their time in vain and idle speculation. By an experiment made by Count Rumford, it was put beyond the possibility of doubt that heat was not an igneous fluid, but a mode of motion. Was this a question that concerned the multitudes, that two or three men spent a hundred years talking about and torturing their brains to understand? There is not a single human being in the civilized world to-day whose interests and welfare have not been touched by the settlement of it. There are millions of peasants in Russia who never heard of Count Rumford, or of an igneous fluid, or of caloric, who have this present year been fed by flour sent them by the western millers and transported on the strength of the conclusion that heat is not an igneous fluid, but a mode of motion. Every steam-car that crosses the continent, and every steamboat that crosses the ocean, moves in the wake of this same conclusion. At first we see some algebraic formulas, an array of curves and figures, that practical people said had nothing to do with everyday life. After a while we see the abstract conclusions reached by aid of the algebraic signs, and settled by the test of experiment, translated into steam engines, and transporting even the peasants of India and Mexico from one end of the country to the other. We see the abstract conclusions of the few thinkers turned into steam to spin the people’s clothes and grind the people’s bread.