Page:Proceedings of the Royal Society of London Vol 60.djvu/559

 FRANZ ERNST Neumann was born on September 11, 1798, at Joa- chimsthal, a small town ahout forty miles to the north-cast of Berlin At the early age of seventeeu he entered the army as a volunteer to fight against Napoleon in the campaign of 1815. A serious wound, received in the battle of Ligny, kept him to his bed for many weeks; but, on recovery, he onee more joined the arny. At the end of the war he returned to his lessons at the "Gymnasium" of Berlia, and subsequently entered the University as a student of theology. Soon afterwards he migrated to Jena, where he came under the infiuence of C. S. Weiss, the Professor of Mineralogy, and turned his attention to that subject. His papers, published between 1823 and 1830, all referred to crystallography, and even his earliest work attracted attention, and left a lasting impression on the science of mineralogy. It secured him a call to the University of Königsberg as Privat-docent," where Bessel, Jacobi, and Dove became his colleagues. Under their influence he gradually drifted more and more towards the study of physics. His knowledge of mathematics was acquired by private study, for althongh the University of Berlin nominally possessed a teacher of mathematics, no lectures were given If the circumstances of Neumann's early education are considered, it is remarkable that he obtained such a command of mathematical physics, and this seems to have been ascribed by himself to the careful study of Fourier's writings, wlich he admired to such an extent that he made a manuscript copy of the great treatise on the Condnction of Heat. In the year 1828 Neumann was appointed Professor Extraordinarius at a salary of 200 thalers (E30). Bessel, who had formed a high opinion of his powers, wrote in the same year a letter to the Minister of Education pressing Neumann's claim to a better positiou. The letter had the desired effect, and Neu- mann was nominated, in 1829, Professor Ordinarius, and his salary raised to £75. He never left Königsberg, continuing his professorial duties until 1876, and died on May 23, 1895.

Among his earlier papers on physical subjects, attention must be drawn to one on the specific heat of minerals (Pogg. Ann., 1831). It contains an extension of Dulong and Petit's law of specific heats to compound bodies having a similar chemical constitution, but is chiefly valuable for the improvement, both in the methods employed and in the theoretical discussion of the experimental results It is shown how the method of mixture may be applied to the case of badly conducting substances. The second paper treats of the specific heat of water. The older observers had stated tat when hot water is poured into cold water, the resulting temperature of the mixture is lower than that calculated, on the assumption that the specific heat of water is constant. Neumann showed that this result is due to errors of experimentation, and demonstrated with