Page:Popular Science Monthly Volume 9.djvu/258

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celebrated French chemist Lavoisier, who was beheaded in the French Revolution. The union, however, not proving a happy one, they soon separated, and Rumford died in his residence at Auteuil the 21st of August, 1814. His first wife had died in 1792, and his daughter, who inherited his title, had come to him at Munich, and returned to America after her father's decease.

The philanthropic interest of Count Rumford in the poor and defective domestic life of the lower classes of society had a great influence in determining the course of his scientific inquiries. It was this feeling that led him to investigate the properties and domestic management of heat. He determined the amount of it arising from the combustion of different kinds of fuel, by means of a calorimeter of his own invention. He reconstructed the fireplace, and so improved the methods of warming apartments and cooking food as to produce a saving of from one-half to seven-eighths of the fuel previously consumed. He improved the construction of stoves, cooking-ranges, coal-grates, and chimneys, and showed that the non-conducting power of cloth is due to the air inclosed among its fibres; and he first pointed out that mode of action of heat called convection; indeed, he was the first clearly to discriminate between the three modes of propagation of heat—radiation, conduction, and convection. He determined the almost non-conducting properties of liquids, investigated the sources of the production of light, and invented a mode of measuring it. He was the first to apply steam generally to the warming of fluids and to culinary operations. He also, as has been stated, experimented extensively upon the use of gunpowder, the strength of materials, and the maximum density of water, and made many valuable and original observations upon an extensive range of subjects, which are described in the essays recently for the first time published in a complete form. As Prof. J. D. Forbes remarks, "all Rumford's experiments were made with admirable precision, and recorded with elaborate fidelity and in the plainest language. Everything with him was reduced to weight and measure, and no pains were spared to obtain the best results."

But it was his investigations concerning the nature of heat that will make him immortal. By experiments in boring cannon he proved its immateriality, and that it does not consist of an imponderable substance or fluid, as implied by the old theory of caloric. In these experiments he demonstrated that the heat generated by friction does not come from any latent source in the materials used, but is derived from the power spent in producing the friction; that its amount is in the ratio of the power expended; that it is a case of the transformation of energy, and a mode of molecular motion. He was half a century in advance of his age, and his researches were long unappreciated; but they are now recognized as forming an epoch in the progress of physical science.