Rowland, Henry Augustus (1848–1901)

US physicist who developed the concave diffraction grating in 1882, which made the analysis of spectra much faster and more accurate. He also carried out the precise determination of certain physical constants.

Rowland was born in Honesdale, Pennsylvania, and studied at the Rensselaer Polytechnic Institute at Troy, New York, later joining its staff. From 1876 he was professor at Johns Hopkins in Baltimore, and made the physics laboratories at the newly established university among the best equipped in the world.

Rowland provided in 1875 the first demonstration that an electric current could be regarded as a sequence of electric charges in motion, by showing that a rapidly rotating charged body was able to deflect a magnet.

Rowland was able to produce greatly improved diffraction gratings and went on to introduce a concave metal or glass grating. This was self-focusing and thus eliminated the need for lenses, which absorbed some wavelengths of the spectrum. He put his invention to use 1886–95 by remapping the solar spectrum, publishing the wavelengths for 14,000 lines with an accuracy ten times better than his predecessors had managed.