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A number of observations have been made of structure changes that occur in hollow and solid electron beams which are confined by a magnetic field. These structure changes occur in both the density of the beam and the transverse velocity components of the beam electrons. The velocity components have been measured by use of a pinhole camera. Some of the results obtained are as follows. The density of electron paths in a beam may become non‐uniform if there is a spread in the forward component of velocity of the electrons. This may occur either because of a spread in initial angle of the electrons or because of a potential depression in the beam. In addition, changes in beam shape and transverse velocity components of the beam electrons can occur as a result of drifting of electrons in crossed electric and magnetic fields, the electric fields in this case being provided by the space charge of the electrons themselves. Thin beams have been found to be unstable and it has been observed that they divide into an array of vortex‐like current filaments when the beam current is sufficiently high. A possible connection between this occurrence and phenomena in the aurora is suggested.