Henry Augustus Rowland

Henry Augustus Rowland (November 27th 1848 - April 16th 1901) is a American physicist .

Biography

Rowland is born with Honesdale in Pennsylvania. After its studies with the Rensselaer Polytechnic Institute he works for one short period as engineer in the railroads. He carries out then a course passage to Wooster in 1871 as professor of physics then he turns over to the polytechnic institute as an assisting professor.

In 1876 it takes the direction of the department of physics of the Université Johns-Hopkins which has just been created. It leaves initially in Europe to study its laboratories and to buy material. He works in the laboratory of Hermann Ludwig von Helmholtz. From return to the the United States it spends the 25 following years to make research, Rowland gives little attention to the administration and teaching. It is very désappointé by the little of case which is made fundamental research in its country at that time, at the time of a meeting of the American Association for the Advancement off Science it declares “our colleges and our university does little case of the key figures, I even intended to say of a member of a college well-known that no professor should engage in research because it is a loss of temps.¹”.

It Marie in 1890, little time before learning that he is dying of the diabetes. In the ten last years of its life it takes several patents in the field of the Télégraphie to ensure the safety material of its family. For the same period it is also one of the principal founders of the American Physical Society.

Rowland belongs to a good number of Learned society, it is, amongst other things, foreign member of the Royal Society, the Academy of Science, the Royal Astronomical Society, in its own country, of the National Academy off Sciences, of the American Physical Society, of which he will be president, and of the American Philosophical Society. It receives several prices, the Médaille Rumford in 1883, the Médaille Henry Draper in 1890, the Légion of honor etc the crater Rowland bears its name.

Research

The first searchs published for Rowland begin about 1872, it tries out on the magnetizing Fer while giving a base theoretical to its experiments. It tries to publish an article on the magnetic Perméabilité to the the United States in a review which turns over to him without publishing it by saying to him that by removing the theoretical part, the quality of the article would be increased. Rowland then sends this article to James Clerk Maxwell which makes it publish in the Philosophical Magazine after having corrected to him even the tests.

During its European round of the physics laboratories, it leads an experiment which it had not been able to make for lack of materials. It shows that a disc electrically charged in fast rotation produces a Magnetic field. At the time the Maxwell's equations cause vigorous debates and the work of Rowland is seen with interest.

Of return to the the United States, it carries out of new measurements of the absolute value of the Ohm, which is at the time definite like resistance of a mercury column 106 cm height and of a mm ² of section. Measurements had been made by the British Association and Rowland shows that their results are not correct. Rowland measures also the ratio of the electric units and the absorption of electricity by crystals. It is also Rowland which suggests the experiments which lead to discovered Hall effect.

Rowland studies as the mechanical equivalence of heat , it discovers as the Specific heat of the Eau is not constant when the temperature varies, James Prescott Joule had supposed the reverse.

In 1881 it turns to the Spectrométrie. It builds a machine to manufacture diffraction patterns. During the construction of this machine it corrects errors which appeared on the networks previously built, Rowland writes an article in the Encyclopædia Britannica, 9th edition on its technique of manufacture of Vis which corrects one of its defects. It has then the idea to manufacture diffraction patterns on a concave surface, idea that it studies in theory and in practice, and publishes off Preliminary Notice Results acccomplished in the Manafucture and the Thorey off Concave grantings for Optical Purposes . This idea appears paying, it builds hundreds of these networks to sell them at cost prices. Rowland uses those of its laboratory to establish, with the assistance of an assistant, a table of the spectra emitted by the elements in order to be used as reference. It off publishes then 1895 with 1897 Preliminary Table Solar Waves Lengths containing the solar spectrum most complete at the time, approximately 20 000 lines of 2 975 with 7 330 Å .

Sources

Astrophysical Newspaper, vol. 13, p.241
Monthly Notes off the Royal Astronomical Society, 1902, p.245

External bonds

biography of American Institute off Physics

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