Wave-lengths of a number of lines, chiefly of carbon, which frequently occur in the spectra of other elements have been measured in the second and third orders on plates obtained in a vacuum spectrograph with a concave grating with a radius of 6 feet ruled with 30,000 lines to the inch. The dispersion was approximatly 4.5A per mm. The carbon lines and the iron standard lines used as comparisons were obtained simultaneously by passing a condensed spark discharge between a carbon and an iron electrode. Details are given of a new method of obtaining curves to correct for (a) deviation of the spectra from normality, (b) error in the tilt of the photographic plate. These curves can be used for correcting the calculated wave-lengths obtained by interpolation between any pair of standards chosen within the range of the curves.

• Received 10 April 1926

DOI:https://doi.org/10.1103/PhysRev.28.36