Tungsten L series lines.—The experiments of Duane and Patterson on the strong lines in the L series of tungsten were repeated with improved apparatus, and also some of the weaker lines were studied. The value 10 obtained by Duane and Patterson for the relative intensity of $\mathrm{L}{\alpha }_1$ to $\mathrm{L}{\alpha }_2$ was confirmed. The theoretical ratio is 9. For the $\beta$ group the relative intensities were found to be, ${\beta }_1:{\beta }_2:{\beta }_3:{\beta }_4:{\beta }_5:{\beta }_6:{\beta }_7:{\beta }_9:{\beta }_{10}=100\mathrm{} :49.3\mathrm{} :15.0\mathrm{} :7.7\mathrm{} :.\mathrm{}47\mathrm{} :2.0\mathrm{} :.\mathrm{}4\mathrm{} :.\mathrm{}68\mathrm{} :.\mathrm{}60\mathrm{}$. The relative intensities of the weak lines among themselves are not very reliable on account of the faintness of the lines and the critical absorption of the target, yet it is clear that the forbidden lines ${\beta }_9$, ${\beta }_{10}$ are of the same order of intensity as ${\beta }_5$, ${\beta }_7$. For the $\gamma$ group the relative intensities were found to be, ${\gamma }_1:{\gamma }_2:{\gamma }_3:{\gamma }_4:{\gamma }_5:{\gamma }_6:{\gamma }_8=100\mathrm{} :14.0\mathrm{} :22.3\mathrm{} :7.0\mathrm{} :3.0\mathrm{} :2.3\mathrm{} :1\mathrm{}(?)\mathrm{}$. ${\gamma }_8$ could not always be obtained. The determination of the intensity ratios for ${\alpha }_1$, ${\beta }_1$ and ${\beta }_2$, ${\gamma }_1$ was complicated by absorption in the target. The agreement of the observed value of the intensity ratio for $\frac{{\beta }_3}{{\beta }_4}$ with the theoretical value 2, tends to confirm Stoner's suggestion that there are twice as many electrons in the ${\mathrm{M}}_{22}$ orbit as in the ${\mathrm{M}}_{21}$. The deviation of the observed intensity ratio for $\frac{{\gamma }_3}{{\gamma }_2}$ from 2 may be due to the influence of intervening levels.

Copper K series lines.—The average of two determinations of the relative intensity of $\beta$ to $\gamma$ gave 100/2.4. No reliable evidence of the non-diagram lines $K_{{\alpha }_3{\alpha }_4}$ was obtained at 30,700 volts.

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