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FRANZ ERNST NEUMANN was born on September 11, 1798, at Joa- 

 chimsthal, a small town about forty miles to the north-^ast of Berlin. 

 At the early age of seventeen 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 once more joined the army. At tbe 

 end of the war he returned to his lessons at the " Gymnasium " 

 of Berlin, and subsequently entered the University as a student of 

 theology. Soon afterwards he migrated to Jena, where he came under 

 the influence 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 Kchiigs- 

 berg 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 although 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, which he admired to such an 

 extent that he made a manuscript copy of the great treatise on the 

 ' Conduction of Heat.' In the year 1828 Neumann was appointed 

 Professor Extraordinarius at a salary of 200 thalers (30). 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 position. The letter had the desired effect, and Neu- 

 mann was nominated, in 1829, Professor Ordinarius, and his salary 

 raised to 75. He never left Konigsberg, 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 that when 

 hot water is poured into cold water, the resulting temperature of 

 the mixture is lower than tha.t 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 



