AuG. 19, 1923 MEGGERS: ARC SPECTRUM OF VANADIUM 317 
Rep, H. F., and SterHen Taser, The Virgina Islands earthquake of 1867-1868: Seis- 
mol. Soc. Amer. 10: 20-25. 1920. 
TABER, STEPHEN, The great fault troughs of the Antilles: Jour. Geol. 30:89-114. 1922. 
VaucuHan, T. W., Platforms of barrier coral reefs: Amer. Geograph. Soc. Bull. 46: 426- 
429. 1914. 
——.,, Some littoral and sublittoral physiographic features of the Virgin and northern 
Leeward Islands and their bearing on the coral reef problem: Journ. Wash. 
Acad. Sci. 6: 53-66. 1916. 
—, Fossil corals from Central America, Cuba, and Porto Rico, with an account of 
the American Tertiary, Pleistocene, and Recent coral reefs: U. S. Nat. Mus. 
Bull. 103: 180-524, pls. 68-152, text figs.4-25. 1919. 
———., The biologic character and geologic correlation of the sedimentary formations 
of Panama in their relation to the geologic history of Central America 
and the West Indies: [bid. 547-612. 1919. 
———., Corals and the formation of coral reefs: Smithsonian Inst. Ann. Rept. for 1917: 
189-276, 37 pls., 1919. 
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‘graph. Ann. 9: 78-82. 1919. 
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SPECTROSCOPY—Regularittes in the are spectrum of vanadium. 
W. F. Mraanrs, Bureau of Standards. 
Kossel and Sommerfeld, in 1919, proposed the spectroscopic dis- 
placement law? (Verschiebungssatz) which states that the spark 
spectrum of any chemical element resembles in structure the are 
spectrum of the element preceding it in the periodic system. This 
led to the alternation law? (Wechselsatz); that is, the even and odd 
structures of both are and spark spectra alternate between adjacent 
columns of the periodic classification. Until recently, the validity 
of these laws could be tested only in the first three columns since 
scarcely any spectral regularities were known except for the rela- 
tively simple spectra of elements in these groups. The incomplete 
and inaccurate description of the more complex spectra has been 
responsible, in part, for the delay in finding significant regularities 
among them. In recent years many of these spectra have been more 
accurately measured in international Angstrom units, and the majority 
of them have had their wave-length tables extended into the red and 
infra-red regions, chiefly as the result of investigations by the Spec- 
1 Received July 16, 1923. Published by permission of the Director, Bureau of 
Standards. 
2 Sommerfeld, Atombau und Spektrallinien 3rd Ed; 455. 1922. 
