viii
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
