244 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, NO. 12 
The spectra of the chemical elements in the periodic table become 
more complex, in general, as the right-hand side of the table is 
approached and the difficulty of classification is correspondingly 
increased. Thus the spectra of the elements in the first two columns 
are almost, completely classified, and typical series or groups of lines 
have been indentified for one or more elements in the remaining 
columns, except the 5th and 8th, for which no significant regularities 
have heretofore been detected. Of the metals in the eighth column, 
iron, although its spectrum contains more than 5000 lines, is never- 
theless, the best adapted for study because of the following reasons. 
Since the iron are was adopted as the source of secondary and tertiary 
standards of wave-lengths, more of its lines have been measured with 
high precision and the relative values of the wave-lengths are of first 
importance in testing the constancy of wave-number differences. 
Furthermore, the data on temperature classification and Zeeman effect 
which sometimes assist in detecting spectral regularities, are more 
extensive for the lines of iron than for any other element in the 8th 
column. In this preliminary report is presented a classification of 
about 200 of the stronger lines of the iron are spectrum in twenty 
multiplets. 
The wave-lengths and intensity and character designations given 
in Table 1 are taken from the observations of Burns.’ Wave-lengths 
were converted to wave numbers (number of waves per centimeter) 
by the use of a table of reciprocals and corrected to vacuum by the 
table given by Meggers and Peters.?. The temperature classification 
is that of King. The notation for the Zeeman effect, measured 
by King’, expresses the observed separations as fractions of the 
normal effect, the figures in parentheses refer to the parallel com- 
ponents, the others to the normal components. 
In Table 1, the lines of each multiplet are given in the order of 
increasing wave-length. Each of these groups may be readily re- 
arranged to bring in evidence the line structure and separations of 
the polyfold sets of levels involved in the multiplet. The first three 
multiplets are rewritten in this manner following Table 1, and will 
serve as examples. 
6 Lick Obs. Bull. No. 247, vol. 8, 1913. 
7 Bull. Bureau of Standards, 14: 697, 1918. 
8 Astrophysical Jour. 37: p. 239. 1913. 
Astrophysical Jour. 56: 351. 1922. 
9 Papers Mt. Wilson Solar Obs. Vol. 2, 1912. 
