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VOL,. 12, 1926 PHYSICS: GIBBS AND WHITE 675 EXTENSION OF DO UBLET LAWS IN THE FIRST LONG PERIOD TO CHROMIUM AND MANGANESE By R. C. GIBBS AND H. E. WHITZ DZPARTMoNT OF PHYrSICS, CORNULL UNIVZRSITY Communicated October 30, 1926 We have already shown2 that the regular and irregular doublet laws may be applied to stripped atoms of the first five elements in the first long period of the periodic table. Recently secured data on chromium and manganese in the extreme ultra-violet have made it possible to extend these laws to Crvi and Mnvii. In view of data reported by Lang' on elements in this period it seemed desirable to repeat our observations on vanadium to see whether the lines we had selected for the Vv doublet were correct or not, and to secure more accurate measurements of their wavelengths. A new photograph taken by using vanadium electrodes containing considerable carbon showed, unmistakably, only one line of the regular doublet at X = 1680.26, the other being masked by several carbon lines, especially by a strong carbon doublet of the second order. A fairly strong vanadium line is found on this plate at X = 1722.51 which is the one selected by Lang as the other member of this doublet. The separation between X = 1680.26 and X = 1722.51 does not yield a plausible sereening constant, nor does it show the anticipated progression of AX. Since our earlier plate contained but few carbon lines it seemed evident that the line found at X = 1715.82 with v = 58281.1, was due to vanadium. As that plate was not in excellent focus at this point a new photograph was made using a very pure specimen of vanadium which was very kindly given to us by Dr. A. S. King of the Mt. Wilson Observatory. This plate proved to be in excellent focus in this region with practically no carbon lines in evidence and showed a comparatively strong pair of lines in the same place as our original pl