Inspection of the previously published data on boron reveals less than a dozen spectral lines attributed to this element in the region of longer wave length than 1850 Angstrom units.<sup>1,2</sup> A consideration of the series spectra of the various stages of ionization of boron however shows that a considerably larger number of lines is to be expected in this region. The present. work was undertaken to see whether with the vacuum spark as a source and spectrographs of medium dispersion some of these lines could be found.
R. A. SAWYER and F. R. SMITH, "ON THE SPECTRA OF BORON," J. Opt. Soc. Am. 14, 287-301 (1927)