A Helical Method of focussing β-Rays

Experiments with a helical method of focussing β-rays are described. Although the method does not appear to be so generally useful for obtaining ordinary β-ray spectra, it possesses certain advantages, of which may be mentioned: (1) Large dispersion; (2) Greater intensity; (3) Good screening. The method produces some evidence on the question of the continuous background, and experiments with it in this connection are described.