Arc spectra in the region 1600-2100

A simple method is described of photographing ordinary arc spectra down to about λ 1600, and measures are given of the spectra thus observed between λ 1600 and λ 2100 of thirteen elements. The measures are believed to be of an accuracy sufficient to make them useful as provisional standards of wave-length. A number of lines hitherto unobserved is recorded and additions have been made to the analysis of the spectra of Mg 1, Be 1 and B 1.