interested in terrestrial
magnetism he made many observations of magnetic intensity and
declination in various parts of Sweden, and was charged by the
Stockholm Academy of Sciences with the task, not completed till
shortly before his death, of working out the magnetic data obtained
by the Swedish frigate "Eugenie" on her voyage round the world in
1851-1853. In 1858 he succeeded Adolph Ferdinand Svanberg (1806-1857)
in the chair of physics at Upsala, and there he died on the 21st of
June 1874. His most important work was concerned with the conduction
of heat and with spectroscopy. In his optical researches, _Optiska
Undersoekningar,_ presented to the Stockholm Academy in 1853, he
not only pointed out that the electric spark yields two superposed
spectra, one from the metal of the electrode and the other from the
gas in which it passes, but deduced from Euler's theory of
resonance that an incandescent gas emits luminous rays of the same
refrangibility as those which it can absorb. This statement, as Sir
E. Sabine remarked when awarding him the Rumford medal of the
Royal Society in 1872, contains a fundamental principle of spectrum
analysis, and though for a number of years it was overlooked it
entitles him to rank as one of the founders of spectroscopy. From 1861
onwards he paid special attention to the solar spectrum. He announced
the existence of hydrogen, among other elements, in the sun's
atmosphere in 1862, and in 1868 published his great map of the normal
solar spectrum which long remained authoritative in questions of
wave-length, although his measurements were inexact to the extent
of one part in 7000 or 8000 owing to the metre which he used as his
standard having been slightly too short. He was the first, in 1867, to
examine the spectrum of the aurora borealis, and detected and measured
the characteristic bright line in its yellow green region; but he was
mistaken in supposing that this same line, which is often called by
his name, is also to be seen in the zodiacal light.

His son, KNUT JOHAN ANGSTROeM, was born at Upsala on the 12th of
January 1857, and studied at the university of that town from 1877
to 1884. After spending a short time in Strassburg he was appointed
lecturer in physics at Stockholm University in 1885, but in 1891
returned to Upsala, where in 1896 he became professor of physics. He
especially devoted himself to investigations of the radiation of heat
from the sun and its absorption by the ea