Henry Augustus Rowland

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Henry Augustus Rowland

Henry Augustus Rowland (born November 27, 1848 in Honesdale , Pennsylvania , † April 16, 1901 in Baltimore , Maryland ) was an American physicist . He mainly worked in the field of electromagnetism . He became known for the concave diffraction grating produced by him , through which z. B. the solar spectrum could be determined more precisely than previously known.

life and work

Rowland came from a family of a number of Protestant theologians . He himself was earmarked for a spiritual career. Rowland, however, was already interested in physics as a schoolboy and often carried out experiments in his parents' house in order to acquire basic physical knowledge. Rebelling against his intended career, he was eventually sent to the Rensselaer Technological Institute at the age of seventeen . In 1870 he graduated as an engineer there . After he then for a major railway and as a teacher in two years Wooster ( Ohio had worked), he returned to Rensselaer to natural history to teach.

Whenever his time allowed, he conducted research in the field of magnetism. Since the American Journal of Science declined to publish his results, he turned to James Maxwell in Great Britain . Maxwell was impressed and arranged for a publication in London's Philosophical Magazine , which, however, received little attention in the United States.

Rowland became increasingly outraged by the situation at his institute and the inadequacies of research opportunities in the United States in general. The university business is characterized by mediocrity, the professors see research as a waste of time.

In 1875 he finally met Daniel Coit Gilman , who was building a faculty at the newly established Johns Hopkins University . This university was the first real research institution in the States, built on the German model. Rowland was sent on a trip to Europe to see laboratories and buy equipment. In 1876 he was elected to the American Academy of Arts and Sciences .

At the Physics Institute of the University of Berlin with Hermann von Helmholtz , he carried out a fundamental experiment in 1875, as the necessary resources were available to him for the first time. It was about the magnetic effects of a rotating, electrically charged metal disc (a gold-plated ebonite disc ). The experiment was extremely difficult, required extensive calculations, and the measured effects were at the detection limit. Rowland finally succeeded in demonstrating that a rotating, electrically charged body generates a magnetic field . This discovery received a lot of attention in the professional world. His results were presented by Helmholtz to the Berlin Academy and published in the Annalen der Physik

Rowland returned to Johns Hopkins University with a selection of the best equipment. However, he spent as little time as possible on teaching and administrative tasks, instead experimenting in his laboratory. He was sometimes feared by his students and colleagues because he did not tolerate mediocrity and could be hurtful in his criticism.

Although Rowland was a skilled mathematician and did some work on the theory of electromagnetism, his greatest skill lay in practical experimentation. He determined the absolute value of the electrical resistance , the ratio of electrical units , the mechanical equivalent of heat and the change in the specific heat capacity of water at different temperatures. He suggested a series of experiments that eventually led to the discovery of the Hall effect by one of his doctoral students .

His greatest contribution to science is an improved diffraction grating, which he began developing in 1882. He discovered that a grid applied to a concave surface gave the best results, also known as a Rowland grid. Rowland's diffraction gratings, which were ten times more accurate than previous devices, were delivered all over the world and formed the basis for spectroscopic applications in physics, chemistry and astronomy . Rowland himself used his grids to study the spectrum of the sun in depth. In 1887 he published an atlas with the complete solar spectrum and thousands of absorption lines , which became the standard work for the next few years.

Rowland has received numerous honors for his achievements. He received honorary doctorates from the universities of Johns Hopkins (1880), Yale (1883) and Princeton (1896) and was made a Knight of the Legion of Honor in France . He was one of twelve foreigners who were accepted into the London Physical Society . In 1881 he was accepted into the National Academy of Sciences . In 1892 he was elected a corresponding member of the Göttingen Academy of Sciences and in 1893 of the Académie des Sciences . Since 1896 he was an elected member of the American Philosophical Society and since 1897 Honorary Fellow of the Royal Society of Edinburgh .

As a delegate of the US government, he took part in international congresses on the definition of electrical units.

On June 4, 1890, he married Henrietta Law. A short time later he found out that he had diabetes and that he had only a few years left. In order to secure the financial situation of his family, he devoted himself in the aftermath improvements in the field of telegraphy and reported several inventions for patent on. Wanting to leave something permanent in physics, he co-founded and first president of the American Physical Society in 1899 .

In 1901 he died in Baltimore. According to his wishes, his ashes were placed in a wall of his laboratory.

In 2000 the asteroid (10557) Rowland was named after him.

Web links

Individual evidence

  1. ↑ Book of Members 1780 – present, Chapter R. (PDF; 508 kB) In: American Academy of Arts and Sciences (amacad.org). Retrieved April 11, 2018 .
  2. ↑ Hermann von Helmholtz, report on experiments on the electromagnetic effect of electrical convection, carried out by Mr. Henry A. Rowland of J. Hopkins' University in Baltimore, Annalen der Physik, Volume 158, 1875, p. 94, monthly reports of the Academy from 17 June 1875, p. 425, digitized . He later repeated the experiments in Baltimore, published in: Philosophical Magazine, Series 5, Volume 27, 1889, p. 445
  3. ↑ Holger Krahnke: The members of the Academy of Sciences in Göttingen 1751-2001 (= Treatises of the Academy of Sciences in Göttingen, Philological-Historical Class. Volume 3, Vol. 246 = Treatises of the Academy of Sciences in Göttingen, Mathematical-Physical Class. Episode 3, vol. 50). Vandenhoeck & Ruprecht, Göttingen 2001, ISBN 3-525-82516-1 , p. 206.
  4. ^ List of members since 1666: Letter R. Académie des sciences, accessed on February 24, 2020 (French).
  5. ^ Member History: Henry A. Rowland. American Philosophical Society, accessed April 11, 2018 .
  6. ^ Fellows Directory. Biographical Index: Former RSE Fellows 1783–2002. (PDF file) Royal Society of Edinburgh, accessed April 4, 2020 .
personal data
SURNAME Rowland, Henry Augustus
BRIEF DESCRIPTION American physicist
DATE OF BIRTH November 27, 1848
PLACE OF BIRTH Honesdale , Pennsylvania
DATE OF DEATH April 16, 1901
Place of death Baltimore , Maryland