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Rh fine harvest, proceeds of his inventions, for at his death he was worth ₤169,000. He did not look upon it as derogatory for a man of science to reap the pecuniary benefit derived from the sale of the inventions of his own brain; by so doing he was enabled to add considerably to the general store of knowledge.

Kelvin's theory of the "dissipation of energy" was announced in a paper on "The Secular Cooling of the Earth," in 1852. He argued that the earth was a hot body like the sun; that it has gradually cooled, is still cooling; and that ultimately it will become cool to the core: life will then be untenable owing to the lowness of temperature.

In 1885 he delivered the Bakerian lecture on the "Electro-dynamics of Qualities of Metals," and in it is published for the first time his "electric convention of heat." Papers on mathematical and physical subjects flowed from his pen, and his inventions were not less numerous. Kelvin, like Newton, was a profound natural philosopher, and the higher mathematics were as play-things to his gigantic and fertile brain.

Among other papers of Kelvin's may be mentioned: "Rigidity of the Earth," "The Mathematical Theory of Elasticity," "The Thermal Effects of Fluids in Motion," "The Determination of a Ship's Place at Sea from Observation of Altitudes," "Approach caused by Vibration," "An Account of Carnot's Theory of the Motive