A study of photographs taken in a very powerful magnetic field with the aid of a cloud chamber activated by counter responses shows (1) that such an arrangement has a strong selective action on showers; (2) that showers so selected have an exceptional multiplicity of tracks; (3) that the two counters show simultaneous responses when no single particle can pass through both of them; (4) that in general these showers consist of a mixture of positive and negative electrons rather than of electrons and protons, no effects certainly attributable to neutrons being observed; (5) that these electrons in getting out of the nucleus some times produce an intense photon spray of the nature of "brems strahlung"; (6) that these photon sprays are increasingly responsible for the simultaneous activation of the two counters the thicker the intervening lead; (7) that a light element like carbon has little effect in producing either showers or sprays; (8) that the total energy of a shower is not larger than that of single electrons (+ or -); (9) that the Dirac theory encounters certain difficulties in accounting for the observed effects.

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