On the Principle of Combination and Stokes' Law in the X-ray Series

New $X-\mathrm{Ray}$ Line ${\gamma }_6$ for Elements Tantalum to Uranium.—The two emission lines ${\gamma }_2$ and ${\gamma }_4$ are found to be in reality three lines. The new line ${\gamma }_6$ has wave-lengths of 1110, 1072, 842, 630 and 593 × ${10}^{-11\mathrm{}}$ cm. for Ta, W, Tl, Th and U respectively. In the cases of Ir, Pt and Au it is too near ${\gamma }_2$ and in the cases of Pb and Bi too near ${\gamma }_3$ to be separated.