Wave length measurements in the Arc Spectra of Neodymium and Samarium

The arc spectra of neodymium and samarium were photographed from 5475 A in the green out into the infra-red. The materials used for the work were neodymium oxalate and samarium oxide prepared at the University of Illinois and samarium oxalate prepared at New Hampshire College. The wave length tables contain about 1500 lines for Nd and about the same number for Sa. A third table contains 130 lines which were common to both spectra. These lines are of unknown origin and may belong to the missing element of order number 61, coming between Nd and Sa. The methods used for the work are identical with those described in a previous work on yttrium, lanthanum, and cerium.