Henry Augustus Rowland

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

Life and work

Rowland came from a family with a number of Protestant theologians. He was scheduled for a clerical career. However, Rowland was interested in already as a student of physics and frequently conducted experiments in his parents' house, to acquire physical knowledge base. Because he rebelled against the intended career for him, he was finally sent at the age of seventeen years on the Rensselaer Technological Institute. In 1870, he graduated as an engineer there. After he then spent two years working for a major railway and as a teacher in Wooster (Ohio ), he returned to Rensselaer, to teach natural history.

Whenever it allowed his time, he conducted research in the field of magnetism. Since the American Journal of Science refused to publish his results, he turned to James Maxwell in the UK. Maxwell was impressed and arranged for the publication in the London Philosophical Magazine, but the little attention was paid in the States.

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

In 1875 he finally met with Daniel Coit Gilman, who built a faculty at Johns Hopkins University, the newly founded. This university was the first real research institution in the United States, built on the German model. Rowland was sent on a trip to Europe to see the laboratories and shop equipment.

At the Berlin Helmholtz Institute, he carried out a basic experiment, as it were for the first time the necessary funds are available. It was about magnetic effects in a rotating, electrically charged metal plate. The experiment was extremely difficult, requiring extensive calculations, the effects measured at the detection limit were. Rowland eventually able to prove that a rotating, electrically charged body creates a magnetic field. This discovery took place in the professional world attention.

Rowland returned with a selection of the best equipment for the Johns Hopkins University. But He turned on as little time as possible for the teaching and administrative duties, but experimented in his laboratory. With his students and his colleagues, he was sometimes feared, because he did not tolerate mediocrity and in his criticism could be hurtful.

Although Rowland was an able mathematician and created some work on the theory of electromagnetism, were his greatest skills 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 specific heat capacity of water at different temperatures. He suggested a series of experiments that eventually led by one of his graduate students to the discovery of the Hall effect.

As his greatest contribution to science applies an improved diffraction grating, the development of which he began in 1882. He discovered that an applied on a concave surface lattice, the best results, also called Rowland grating. Rowlands diffraction grating, which were ten times more accurate than previous devices have been delivered all over the world and formed the basis for spectroscopic applications in physics, chemistry and astronomy. Rowland himself used his grid to the solar spectrum to study in depth. In 1887 he published an atlas with the full solar spectrum and thousands of absorption lines, which was for the next few years the standard work.

For his achievements Rowland numerous honors were bestowed. He received honorary doctorates from the universities Johns Hopkins (1880 ), Yale (1883 ) and Princeton (1896) and was named in France a Knight of the Legion of Honour. He was one of twelve foreigners that have been added to the London Physical Society. In 1881 he was inducted into the National Academy of Sciences.

As a delegate of the U.S. government, he participated in international congresses establishing electrical units.

On June 4, 1890 he married Henrietta Law. A short time later, he learned that he was suffering from diabetes and it only remained a few years of life. To secure the financial situation of his family, he devoted himself in the aftermath improvements in the field of telegraphy, and reported more than one invention patent for. Because he wanted to leave something permanent in physics, he was co-founder and first president of the American Physical Society.

In 1901, he died in Baltimore. His ashes were, according to his wish, embedded in a wall of his laboratory.