Experiments with gratings have been instituted by Sir G.
By persistent research, powerfully aided by the photographic camera and by the concave gratings invented by H.
In 1882, before the Physical Society of London, he gave a description of the diffraction gratings with which his name is specially associated, and which have been of enormous advantage to astronomical spectroscopy.
These gratings consist of pieces of metal or glass ruled by means of a diamond point with a very large number of parallel lines, on the extreme accuracy of which their efficiency depends.
Rowland's efforts the construction of gratings has been improved to such an extent that their use is becoming universal whenever great power or accuracy is required.