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 MAYER MAYFLY 301 in its production. He then sought to express this relation numerically. In the beginning of 1842 he had made considerable progress, but having in the- mean time become town physi- cian of Heilbronn, he could devote but little time to purely scientific inquiry. He deter- mined however to publish a preliminary notice of the work then accomplished, and he con- tributed to the May number of Liebig's Anna- len der Chemie und Pharmacie a brief but re- markable paper entitled Bemerkungen uber die Krafte der unbelebten Natur, which contained the germ of his future labors. In 1845 he published a memoir entitled Die organische Bewegung in ihrem Zusammenhange mit dem Stoffwechsel, in which he expanded and illus- trated the physical principles laid down in his first paper, applying them to organic nature. In 1848 appeared his essay, Beitrdge zur Dy- namik des Himmels, in which he applied the same principles to the heavenly bodies. In 1851 he published another essay, Bemerkungen uber das mechanische Aequivalent der Warme, in which he developed yet further the mechan- ical theory of heat. His general argument is that all the mechanical motions upon the earth and all the phenomena of vegetable and animal life are produced by the sun's heat, the source of all power. Nature stores up the light which streams earthward from the sun and casts it into a permanent form. To this end she has overspread the earth with organisms which, while living, take in the solar light, and by its consumption generate forces of another kind. These organisms are plants, and the vegetable world therefore constitutes the instrument whereby the wave motion of the sun is changed into the rigid form of chemical tension, and thus prepared for future use. The physical forces collected by plants become the property of animals. Animals consume vegetables and cause them to reunite with the atmospheric oxygen. Animal heat is thus produced, and also animal motion. Mayer thus grasped the mechanical theory of heat, illustrating it and applying it in the most di- verse domains. He began with physical prin- ciples; he determined the numerical relation between heat and work ; he revealed the source of the energies of the vegetable world, and showed the relationship of the heat of our fires to solar heat. He followed the energies which were potential in the vegetable up to their local exhaustion in the animal. He then drew attention to the great amount of heat generated by gravity where the force has suffi- cient distance to act through. He found that the gravitating force between the earth and sun was competent to generate an amount of heat equal to that obtainable from the com- bustion of 6,000 times the weight of the earth of solid coal. He saw that this was a power sufficient to produce the enormous tempera- ture of the sun, and also to account for the primal molten condition of the earth ; and he concludes that the light and heat of the sun are maintained by the constant impact of meteoric matter. Similar conclusions in rela- tion to the mechanical theory of heat were arrived at in England by Dr. James Prescott Joule almost contemporaneously with the in- vestigations of Dr. Mayer ; but there is no rea- son for supposing that either derived his inspi- ration from the other. Each was an indepen- dent creator of the theory. (See CORRELA- TION.) In the revolution of 1848 Dr. Mayer took what was called the side of order, which aroused against him the antagonism of many of his neighbors. His scientific labors were attacked, and this in connection with the loss of children threw him into an excited and sleepless condition. On May 28, 1850, being suddenly seized with a fit of delirium, he quit- ted his bed and leaped from a second-story window, 30 ft. high, to the street below. He recovered from the shock, but his mind was se- riously affected. After spending some time in an asylum he was fully restored to health, and he now (1875) resides in Heilbronn. A com- plete edition of his works has been published under the title Die Mechanik der Wdrme (Stutt- gart, 1867). In 1871 the Copley medal was awarded to him by the royal society of London. MAYER, Karl, a German pianist and composer, born in Clausthal in 1799, died in Dresden, July 2, 1862. His father was a clarinet vir- tuoso, and was attached to the military band of a regiment ordered to Russia in the cam- paign of 1812. He remained in Russia, and the young Karl received at Moscow lessons from the pianist John Field. In 1818 he went to Paris, and during 1819 resided at Brussels. After this he travelled through Germany, and then returned to Moscow, where, as well as at St. Petersburg, he was held in high esteem as a teacher. He eventually returned to Ger- many. He was one of the most graceful com- posers for the piano of his day, and his num- bered works for that instrument are 351. His larger compositions consist of concertos and rondos for piano and orchestra. MAYER, Karl Friedrich Hartmann, a German poet, born at Neckar-Bischofsheim, Wurtem- berg, March 22, 1786, died in Tubingen, Feb. 25, 1870. He studied law at Tubingen, where he became chief councillor of justice. In 1833 he was a liberal member of the chamber. He was an intimate friend of Uhland, whose biog- raphy he published (Stuttgart, 1867). Several editions of his poems have appeared. MAYFLY, an insect generally placed in the order neuroptera, with the dragon flies, ephe- 1 merje, myrmeleon, and termites or white ants, forming the genus phryganea as restricted by Latreille. The jaws are hardly perceptible; the lower wings are broader than the upper, and longitudinally plaited ; they have no sting nor piercer, and the antennae are as long as the body ; they undergo complete transformation, larvaa and pupse living in the water and feeding on aquatic insects and plants. The eggs are laid on the leaves of willows and other trees