This paper describes a method for presenting on a fluorescent screen the time varying velocity and density modulation of an electron beam, modulated at a frequency of 3000 Mc, as it emerges from the cavities of a klystron, the wave guide in a traveling wave tube, or similar structures. In order to deflect an electron beam at this frequency, each pair of the usual deflection plates is replaced by a two‐wire transmission line, resonant at the beam modulating frequency. Under proper phase conditions a circular trace is obtained, where one complete revolution of the beam corresponds to exactly one complete cycle of events on the beam at the point of its deflection. Since electrons having different velocities will be deflected differently, a complete velocity and density picture of the beam at a given point of interest is obtained. This is demonstrated by observing the bunching action in the drift region of a velocity modulated electron beam.

Review of “Die Welt der ungewohnten Dimensionen” by Arnold Hildesheimer.

Excerpt: In our first study of the beginnings of mental life we analyzed the origins of intelligence in children and tried to show how the forms of intellectual activity are constructed on the sensorimotor level. In the current work we have tried, on the other hand, to understand how the real categories of sensorimotor intelligence are organized, that is, how the world is constructed by means of this instrument. In conclusion, the time has come to show the unity of these various processes and their relations with those of the child’s thought, envisaged in their most general aspect.