Rowland, ROH luhnd, Henry Augustus (1848-1901), was an American physicist. He invented the concave grating for spectrum analysis, and built an improved ruling and dividing engine for making precise rulings on glass or metal surfaces. In his Berlin experiment in 1876, he proved that electrostatic charges of electricity in motion produce a magnetic field similar to the field produced by an electric current in a wire. Rowland also determined the mechanical equivalent of heat, and the value of the ohm, the unit used for measuring resistance to the flow of an electric current (see Ohm). Rowland was born in Honesdale, Pa. He was a professor of physics at Johns Hopkins University from 1875 to 1901.