The use of polarized light is extended to the determination of the distribution and evaluation of axial stresses in long rectangular plates subjected to torsion. The equation connecting the stresses, $\sigma$, with the distance from the axis of rotation, $r$ is $\sigma =\frac{1}{2}\frac{E{\varphi }^2}{l^2}\left(r^2-\frac{h^2}{12}\right),$ from which it follows that the compression along the central axis is half as large as the tension along the edges. A new photometric method for measuring the stress intensities was employed. As a photometer, a selenium cell with a narrow window was used; and it is suggested that the photo-electric cell may be applied to this purpose with great advantage.

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