![EINSTEIN, Albert. Autograph postcard signed ('Einstein') to Wander Johannes de Haas ('Dear De Has [sic]'), [postmarked Berlin, 17 March 1915], including an autograph diagram showing two states of a spool under a magnetic field, one page, 8vo, autograph address panel.](https://www.christies.com/img/LotImages/2005/CKS/2005_CKS_07088_0120_000(110228).jpg?w=1)
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EINSTEIN, Albert. Autograph postcard signed ('Einstein') to Wander Johannes de Haas ('Dear De Has [sic]'), [postmarked Berlin, 17 March 1915], including an autograph diagram showing two states of a spool under a magnetic field, one page, 8vo, autograph address panel.
REFINEMENTS TO THE CELEBRATED EINSTEIN-DE HAAS EXPERIMENT. 'According to your method even the induced effect of the electromagnetic field of the rod can be eliminated, by positioning the identical, oppositely-wound spools right next to each other' -- a diagram demonstrates the proposition. In this way the magnetic field of the rod will produce in both spools an almost equally great but opposite electromagnetic force.'But the spools must have the smallest possible diameter'.
The Einstein-de Haas experiment aimed to measure the torque generated by a reversal of the magnetisation of an iron cyclinder: it involved suspending an iron rod by a glass wire; a fixed solenoid was placed coaxially around the cylinder, and an alternating current was run through the solenoid at a frequency correlated to the torsional vibrations of the suspended wire (the 'resonance method'). The experiment demonstrated Ampère's hypothesis that magnetism is due to the circulation of 'hidden electric currents', provided the first proof of the existence of rotation induced by magnetisation, and confirmed the existence of electrons in stationary orbits without loss of energy radiation.
REFINEMENTS TO THE CELEBRATED EINSTEIN-DE HAAS EXPERIMENT. 'According to your method even the induced effect of the electromagnetic field of the rod can be eliminated, by positioning the identical, oppositely-wound spools right next to each other' -- a diagram demonstrates the proposition. In this way the magnetic field of the rod will produce in both spools an almost equally great but opposite electromagnetic force.'But the spools must have the smallest possible diameter'.
The Einstein-de Haas experiment aimed to measure the torque generated by a reversal of the magnetisation of an iron cyclinder: it involved suspending an iron rod by a glass wire; a fixed solenoid was placed coaxially around the cylinder, and an alternating current was run through the solenoid at a frequency correlated to the torsional vibrations of the suspended wire (the 'resonance method'). The experiment demonstrated Ampère's hypothesis that magnetism is due to the circulation of 'hidden electric currents', provided the first proof of the existence of rotation induced by magnetisation, and confirmed the existence of electrons in stationary orbits without loss of energy radiation.
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