Rowland, Henry Augustus
Rowland, Henry Augustus (1848-1901), a United States physicist. Rowland invented the concave diffraction grating, which eliminated the need for lenses in a spectroscope, and a machine for producing gratings of high quality. With the spectroscope, he made a detailed study of the sun's spectrum. Rowland made an accurate determination of the unit of electrical resistance (the ohm) and showed that electrical charges on a moving body are equivalent to an electric current.
Rowland was born in Honesdale, Pennsylvania. He studied at Rensselaer Polytechnic Institute, where he taught briefly. He became professor of physics at Johns Hopkins University in 1876, remaining there until his death.