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iv. education and mental culture.
A. J. Ångström (1814—74) was one of the leading scientists of Uppsala
University. He may indeed be claimed to be one of the chief founders of the
spectrum analysis. Thus in 1853 he enunciated the principle that a body in an
incandescent condition should emit the same kinds of light as it absorbs at ordinary
temperature. Among his other optical works may be mentioned his atlas of
the solar spectrum, which was for a long time the standard for all determinations of
wave-lengths, his researches in the optics of crystals, and those in the spectrum
of the aurora borealis. Moreover he invented an extremely ingenious method for
determining the heat conductivity of bodies. — Another of Sweden’s most eminent
physicists was E. Edlund (1819 — 88), who elaborated a new theory to explain
electricity: like Franklin he assumed the existence of one electric fluid, which
he identified with the ether of light. He endeavoured to explain
electro-dynamics by the current of ether. Amongst his numerous experimental
investigations may be particularly mentioned his works on extra currents; on the
heating effects of induction currents; on unipolar induction, by which he tried to
explain the aurora borealis and atmospheric electricity; on discharges of
electricity in rarefied gases, which, in accordance with his theory, led him to suppose
a vacuum to be a good conductor of electricity. Further, he discovered the
electro-motive force in the electric arc; he investigated the evolution of heat in
metals ensuing on a change of volume, and endeavoured by wire-stretching
experiments to determine the mechanical equivalent of heat; he studied also the
formation of ice in the sea. — T. E. Thalén (1827 —1905) has conducted
experiments of great delicacy in spectrum analysis, and was the assistant of
Ångström at many of his labours in the same field. Thalén also wrote several
works on magnetism; thus lie made important contributions to our knowledge
of terrestrial magnetism in Sweden, and also methods of investigating iron
ore fields. — K. Ångström (1857—1910) devoted himself almost exclusively
to the study of radiation and questions connected with it. His studies of
solar radiation were of great scope and of fundamental importance: for this
purpose he constructed an instrument called the pyrheliometer. This
instrument, which came into extensive use, was adopted in 1905 as the standard
instrument for measuring solar radiation at the Meeting of the International
Union for Cooperation in Solar Research at Oxford, and shortly afterwards at
the International Meteorological Conference at Innsbruck. Ångström also
constructed an apparatus for measuring the nightly radiation from the surface
of the earth.
Among other eminent Swedish physicists of the past, may be mentioned F.
Wrede (1802 — 93), who directed his attention chiefly to optics, P. A. Siljeström
(1815—92), who carried on a series of experiments with regard to the validity
of Boyle’s law at low pressures, and John Ericsson (1803—89), of whose
remarkable discoveries and studies may here be noticed his experiments on the
radiation of heat and his invention of the calorific and the sun engine. — K. A.
V. Holmgren (1824—1905) who worked in the sphere of electricity, G. B.
Dahlander (1834—1903; electricity) and A. Wijkander (1849—1913; terrestrial
magnetism).
Among now living physicists should be mentioned: K. B. Hasselberg (b. 1848;
professor at the Academy of Sciences, Stockholm), who has published accurate
works on spectrum analysis and spectrography; S. Arrhenius (b. 1859; professor
at the Nobel Institute), who has published numerous works on physical chemistry,
and developed the theory of electrolytical dissociation, for which he obtained the
Nobel Prize in chemistry in 1903. A. Gullstrand (b. 1862; professor at
Uppsala), who has published a series of works in geometrical optics which have
revolutionized the theory of optical imagery, and who obtained in 1911 the Nobel Prize
in medicine for works relating to the dioptrics of the eye. G. Lundquist (b.
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