MAYER, JULIUS BonEnr voN (1814-78). A German physicist, horn in Heilbronn, Wiirttem berg. Ile attended the gymnasium at Heilbronn. studied medicine at Tiibingen, and finished his university course at Munich and Paris. Ile made a voyage to Java in 1840, and while there made observations on the blood whip)) led him to the in vestigation of the subject of animal heat, and final ly to that of the conservation and correlation of fumes. After his return to Heilbronn he prac ticed medicine there, but after a few year; de voted himself almost exclusively to his scientific investigations. He published ;t preliminary notice of his work up to 1842, in 1Aelsig's..4minfen inic und under the title gen fiber die Kriifte der unbelebten Natur." after it had been refused by Poggendortrs nna fen on ac count of its novel and revolutionary character. It was in this paper that the first announcement was made of the principle underlying the theory of the conservation of energy. In 1815 he made a fuller explanation of the subject in a memoir, under the title Die organiscbe Heti-pining in ihr, sic Zusammenhange mit dent Stoffirechel. In 1848
he published Beitriige zur nynamik des Himmels, and in 1851 the essay for which he is perhaps more generally known in popular science, that upon the mechanical equivalent of heat ( firmer kung, n iiber doss mcchitnische Aequirab nt der Warm,), in which he developed and expanded the prineiples laid down in his former papers. To Slayer is due the first coneeption of the doctrine of the conservation of energy. though be was soon followed by .rotile and Helmholtz (cm.v.) with in vestigations and papers on the same subjects. His collected appeared under the title Die 31 (Thu nil: der 1Viirme, 3(1 ed., by Weyrauch Consult : Weyratieh, Robert Mayer (Stuttgart, 1890) : id., Kleinerc Sehriften and Brief(' 1'011 Robert Mayer (its., 1893) : and Gross, Robert Mayer and Hermann ron Helmholtz: ("Ber lin, 1898).