Experimenteller Nachweis der Ampèreschen Molekularströme [Experimental Proof of Ampère’s Molecular Currents]
FIRST EDITIONS IN ORIGINAL WRAPPERS of the papers documenting the “Einstein-de Haas” effect, Einstein’s greatest experimental success.
“Einstein was no mere armchair experimenter. Another Dutch friend, Hendrik A. Lorentz, had a son-in-law, Wander de Haas, who was also a physicist. When Einstein was in Berlin, de Haas needed work and came to join Einstein as an assistant in April 1915. Together they worked on the properties of a magnetic field, about which Einstein wrote, ‘I have done a wonderful experimental thing this semester, together with Lorentz’s son-in-law.’ The paper, ‘Experimental Proof of Ampere’s Molecular Currents,’ was published... right in the middle of Einstein’s major work on general relativity, in the Proceedings of the German Physical Society...
“Ampere suggested, in 1820, that magnetism is caused by electric currents in motion. By 1915, the electron had long since been discovered, and it seemed natural to explore Ampere’s idea further. Einstein and de Haas tool a large iron cylinder and wrapped a coil around it. They passed an alternating current through the coil, and the changing current altered the cylinder’s magnetization. This changing magnetization set up a torque on the cylinder, which began to rotate... Einstein and de Haas thought that magnetization... gets all the electrons orbiting the atoms in the iron cylinder to move together. When the angular momentum of the electrons is in sync, the cylinder starts to rotate. Einstein and de Haas described theoretically the motion of an electron orbiting in a circular path. They found a relation between the magnetization and the angle through which the cylinder rotates. Their idea, that a magnet can behave like a gyroscope, is now known as the Einstein-de Haas effect. Einstein wrote that ‘the experiment yielded in all detail a confirmation of the theory.’”
While their results were quantitatively off [“in the pre-spin days of 1915, any dynamic theory of ferromagnetism had necessarily to be incorrect” (Pais)], they were qualitatively correct and the experiment was extremely influential. “Niels Bohr, who applied the idea of the quantum to the atom, loved the Einstein-de Haas effect... [for] Einstein and de Haas provided experimental support for Bohr’s [model of the atom]. Bohr wrote, ‘As pointed out by Einstein and de Haas, their experiments indicate very strongly that electrons can rotate in atoms without the emission of energy radiation.’ It was another important step forward for quantum theory” (Calaprice, Albert Einstein: A Biography). Weil *73.
WITH: THE OFFPRINT of the Dutch version of the paper (Proefondervindelijk bewijs voor het bestaan der moleculaire stroomen van Ampère”) in Koninklijke Akademie van Wetenschappen te Amsterdam, 14 May 1915. pp. 1-16. This Dutch version appears to be extremely rare and is often misattributed (for example, Calaprice mentions it as a “correction”). It seems to have appeared immediately after the appearance in Verhandlungen.
The Verhandlungen issues also contain influential papers by Planck on quantum theory (“Die Quantenhypotese für Molekeln mit mehreren Freiheitsgraden”, pp. 438-451; “Bemerkung über die Entropiekonstante zweiatomiger Gase”, pp. 418-19) and Max von Laue on Einstein’s work “Die Einsteinschen Energieschwankungen” 198-202).
Early ownership signatures on the wrappers; two are presumably the signatures of Hermann Behnken (1889-1945), a noted physicist and contemporary of Einstein's.
Einstein and de Haas, Experimenteller Nachweis der Ampèreschen Molekularströme. IN: Verhandlungen der Deutschen Physikalischen Gesellschaft. Band 17, Hefte 8, 10, 22 und 24 (Index). In Part I: pp. 152-170) ; with Berichtigung (Part II: p. 203)  with Notiz zu unserer Arbeit (Part III: p. 420); . Braunschweig: Vieweg & Sohn, 1915. Octavo, original wrappers; custom box. Four issues. Only slight wear to wrappers. Beautiful copies. EXTREMELY RARE IN ORIGINAL WRAPPERS.