Abstract
It is found that pin-hole photographs may be made of ions or electrons emitted by a heated source. The crossed paths of the charged particles is explained by the space charges in the immediate neighborhood of the emitting points on the source, which distort the lines of force and allow of accelerations in various directions. Part of the electron emission from an oxide coated filament and the positive ion emission from spodumene is thus found to be concentrated at definite points on the surface.

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