7 2 2 D O C U M E N T 5 1 0 A P R I L 1 9 2 9 PD. Reichspatentamt Patentschrift Nr 590 783. [1] The Einsteins, after having spent December 1932 to March 1933 at the California Institute of Technology in Pasadena, accepted the invitation of the Belgian royal couple to reside in Belgium at the small seaside resort Le Coq sur Mer until they would decide whether to accept the invitation of the University of Oxford or Abraham Flexner’s offer of a position at the new Institute for Advanced Study in Princeton. After several short visits to London and Oxford, Einstein traveled to Princeton on 7 October 1933, never to return to Europe. [2] The idea to diminish the rigidity by compression or expansion was Goldschmidt’s (see Doc. 495), and was used by him in thirteen inventions he was working on during the second half of the 1920s. In all of them, the rigidity of the membrane of the loudspeaker and not that of its rod mag- net was reduced (see, e.g., Doc. 181). Therefore, the claim in this invention may be attributed to Einstein (see Illy 2012, pp. 121–124). 510. To Ethel Michanowsky-Charol[1] [Berlin, 25 April 1929] I have remained speechless since you were struck by heavy fate[2] […] You are one of those fragile natures, whose conscious experience cannot keep up with all the weight fate keeps putting on you […] Along with the horrible news however, came a hopeful sentiment. All of a sudden you have become a free human being who, for the second time has the chance, as a ripe and conscious being, to look for a new path in life […] PLf (Sotheby’s Auction Catalog, December 1999, lot 79). [84 102]. [1] Eleonora (Ethel) Michanowsky-Charol (1896–1968) was a Russian-born Jewish socialite and artist in Berlin. [2] Most likely a reference to the death of her husband (see Doc. 507, note 1).