Cinematographic Record of the Iron Transition, as seen by the Electron-Microscope

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RECENTLY E. Bruche and W. Knecht1 described the electronoptical observation of the transition of into iron. In their beautiful experiments, however, the emission of the test-piece (after activation by means of an evaporated barium layer) at the transition temperature of about 900° C. was so small that the actual occurrence of the process could not be observed on the fluorescent screen without sufficient adaptation of the eye. In order to obtain a fluorescent image clear enough to be photographed, the temperature of the test-piece had to be raised to about 1000° C. A photographic record of the transition could therefore only be obtained by observing whether, after lowering the temperature to the neighbourhood of the transition point and raising it again at 1000°, the texture of the test-piece had changed or not.