On the Penumbra of Cosmic Radiation

The development of the theory of the penumbra is given, and a few examples of penumbral trajectories are shown. Pairs of values of the energy and latitude having penumbral regions are indicated. Two methods of analyzing the data obtained by means of Bush's Differential Analyzer are given; the first yielding the allowed directions for just one type of penumbral orbit over all latitudes and for one energy; the second giving the whole penumbra for one energy and one latitude. The energy chosen in each case was $r=0.425$ st\"ormer (1.08×{}10¹⁰ ev for electrons). By means of the second method, the almost complete allowed cone is obtained for this energy and for a geomagnetic latitude of 20^∘{}.