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M A Y M A Y 649 industry of the place is the cloth manufacture, which occupies 8000 persons iu the town, and neighbourhood. The population in 1876 was 10,098. Mayenue had its origin in the castle built here by Juhel, the son of Geoffroy of Maine, in the beginning of the llth century. It was besieged by William the Conqueror, and afterwards by the earl of Salisbury ; and the possession of it was disputed by the Royalists and the Leaguers, as also by the Republicans and the Vendeans. MAYER, JOHANN TOBIAS (1723-1762), one of the greatest of last century s astronomers, was born at Marbach in Wiirtemberg, February 17, 1723. He was brought up at Esslingen in comparatively poor circumstances, and as a mathematician was mainly self-taught. He had already published several original geometrical tracts when, in 17-16, he entered Homann s cartographic establishment at Nuremberg. Here he introduced many improvements in map-making, and gained a scientific reputation which led (in 1751) to his election to the chair of economy and mathematics in the university of Gb ttingen. In 1754: he became superintendent of the observatory, where he laboured with great zeal and success till his death, February 20, 1762. His first important astronomical work was a careful investigation of the libration of the moon (Koamo- fjraphische Nachrichten, Nuremberg, 1750), the elements of which and the position of the moon s axis of rotation he | determined with much greater accuracy than had previously been done. His great fame rests on his lunar "tables, which were published in 1753 along with new solar tables, and transmitted to England in 1755. These tables, which were compared by Bradley with the Greenwich observa tions, and found to be sufficiently accurate to determine the longitude at sea to within half a degree, solved the problem of practically determining longitude anywhere on the earth s surface. An improved set was afterwards published in London (1770), as also the theory (Theoria Lunx juxta Systema Newtonianum, 1767) upon which the tables are based. They were sent to England by his widow, who in consideration received from the British Government a grant of 3000. Appended to the London edition of the solar and lunar tables are two short tracts, the one on determining longitude by lunar distances, together with a description of the repeating circle (invented by Mayer in 1760), the other on a formula for atmospheric refraction, which applies a remarkably accurate correction for temperature. Mayer left behind him a considerable quantity of manuscript, part of which was collected by Lichtenberg and published in one volume (Opera Incdita, Gottingen, 1775). It contains, amongst other papers, an easy and accurate method for calculating eclipses; an essay on colour, in which three primary colours are recognized; a catalogue of nine hundred and ninety-eight zodiacal stars ; and a memoir, the earliest of any real value, on the proper motion of fixed stars, which was originally communicated to the Gottingen Royal Society in 1760. The other part still remains in manuscript, and in cludes papers on atmospheric refraction (dated 1755), on the motion of Mars as affected by the perturbations of Jupiter and the Earth (1756), and on terrestrial magnetism (1760 and 1762). In these last Mayer seeks to explain the magnetic action of the earth by a simple hypothesis. He supposes a small bar-magnet to be placed with its centre at the earth s centre, and calculates the position of equili brium of a second small magnet at any given point on the earth s surface, assuming the law of magnetic attraction and repulsion to be that of the inverse square. Though the values of the declina tion and dip calculated according to this theory do not agree with the observed values, Mayer must be credited with the first really definite attempt to establish a mathematical theory of magnetic action, and as the first who gave any experimental evidence in favour of the inverse square of the distance as the law of force. See Han- steen s Magnctismus der Erdc. MAYER, JULIUS ROBERT (1814-1878), was born at Heilbronn, Nov. 25, 1814, studied medicine at Tubingen, Munich, and Paris, and, after a journey to Java in 1840 as surgeon of a Dutch vessel, obtained a medical post in his native town. He claims recognition as an independent a priori propounder of the " First Law of Thermodynamics," but more especially as having early and ably applied that law to the explanation of many remarkable phenomena, both cosmical and terrestrial. His first little paper on the subject, " Bemerkungen iiber die Kriifte der unbelebten Natur," appeared in 1842 in Liebig s Annalen, five years subsequent to the republication, in the same journal, of an extract from the great memoir of MOHR (?.? .). Mayer s statements as to the " indestructibility of force " (as he calls it) were based almost entirely upon scholastic dicta, such as causa xquat effectum, &c. The main experimental fact which he adduces in support of his reasoning as to the convertibility of work and heat is a mere repetition, in a very inadequate form, of a curious experiment made by Dr Reade of Cork, who found (Nicholson s Journal, xx., 1808, p. 113) that water was sensibly heated after being violently shaken in a phial. But Dr Reade states explicitly the precautions he had taken to protect the phial and its contents from heating by the hand of the operator, an important detail which is unnoticed by Mayer. It has been repeatedly claimed for Mayer that he calculated the value of the dynamical equivalent of heat, indirectly no doubt, but in a manner altogether free from error, and with a result according almost exactly with that obtained by Joule after years of patient labour in direct experimenting. Mayer assumed that the heat developed by compression of air is the equivalent of the work spent in the compression. If we had independent proof of this the result would undoubtedly follow. 1 And it has been urged that the man who, by a single burst of genius, reached at once the goal which others had been painfully seeking, merits an amount of fame com mensurate with that due to discoverers like Newton or Galileo. This claim on Mayer s behalf was first shown to be baseless by Thomson and Tait (" Energy, " Good Words, 1862). This article gave rise to a long but lively discussion. A calm and judicial annihilation of the claim is to be found in a brief article by Stokes, Proc. Moy. Soc., 1871, p. 54. See also Maxwell s Theory of Heal, chap. xiii. Mayer entirely ignored the grand fundamental principle laid down by Sadi Carnot, a principle which has done even more for physics than lias the conservation of energy itself, viz., that nothing can be concluded as to the relation between heat and work from an experiment in which the working substance i.s left at the end of an operation in a different physical state from that in which it was at the commencement. Mayer has also been styled the discoverer of the fact that heat consists in (the energy of) motion, a matter settled at the very end of the 18th century by Rumford and Davy. In the teeth of this statement we have Mayer s own words, " We might much rather assume the contrary, that in order to become heat, motion must cease to be motion." Mayer s real merit consists in the fact that, having for himself made out, on inadequate and even questionable grounds, the con servation of energy, and having obtained (though by inaccurate reasoning) a numerical result correct so far as his data permitted, he applied the principle with great power and insight to the ex planation of numerous physical phenomena. His papers, which have been republished in a single volume with the title Die Mechanik der Warmc (2d ed., Stuttgart, 1874), are of extremely unequal mrit. But some, especially those on Celestial Dynamics and Organic Motion, are admirable examples of what really valuable work may be effected by a man of high intellectual powers, in spite of imperfect information and defective logic. Different, and, it would appear, exaggerated, estimates of Mayer are given in Dr Tyndall s papers in the Phil. Mag., 1863-64 (whose avowed object was "to raise a noble and a suffering man to the position which his labours entitled him to occupy "), and in the extraordinary treatise by Diihring, liobcrt Mayer, der Galilei, dcs neunzchntcn Jahrhunderts, Chemnitz, 1880. Some of the simpler facts of the case are summarized by Tait in the Phil. Mag., 1864, ii. p. 289. MAYHEM (MAIM), an old term of the law signifying an assault whereby the injured person is deprived of a member proper for his defence in fight, e.g., an arm, a leg, a fore tooth, &c. The loss of an ear, jaw tooth, &c., was not mayhem. The most ancient punishment in English law was retaliative membrum pro membra, but ultimately at common law fine and imprisonment. Various statutes were passed aimed at the offence of ^S and dis " 1 Seguin, three years before, had assumed that the work done by steam or any other expanding substance is the equivalent of the heat which disappears during the expansion. A similar idea, but more accurately expressed, is to be found in Mohr s paper, above referred to.

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