DOCUMENT 52 AUGUST 1899 225 Einstein makes no further mention in his letters of work on the electrodynamics of moving bodies for almost two years. However, the inclusion of "die prinzipielle Trennung von Lichtäther und Materie, Definition absoluter Ruhe" among the topics he discussed with Besso in April 1901 (Doc. 96) indicates his continued interest in the subject. In March 1901, he wrote Maric that he looked forward to the successful conclu- sion of "unsere Arbeit über die Relativbewegung" (Doc. 94). In September he wrote Grossmann that he had devised a simpler method for the investigation of the mo- tion of matter relative to the ether, based "auf gewöhnlichen Interferenzversuchen" (Doc. 122). By December he was hard at work on an electrodynamics of moving bodies, which promised to become "eine kapitale Abhandlung" (Doc. 128). A calcu- lational error had earlier led him to doubt the correctness of his "Ideen über die Relativbewegung," but he now believed more than ever in these ideas (ibid). He ex- plained this work to Professor Kleiner, who encouraged him to publish both his theoretical and experimental ideas (see Doc. 130). In spite of Einstein's enthusiasm and Kleiner's encouragement, no publication on this subject ensued for over three years. In Einstein's final reference to this subject in this volume, he states his inten- tion to study "was Lorentz und Drude über die Elektrodynamik bewegter Körper geschrieben haben" (Doc. 131).  See the Introduction to Volume 1 for comments on the nature of Maric's collab- oration with Einstein.  Einstein 1905c is datelined June 1905. 52. To Mileva Maric Paradies [Mettmenstetten,] Donnerstag. [10? August 1899] L[iebes] D[oxerl]! Vielen Dank für Ihr Brieferl, das ich schon wieder beantwortet hätte, wenn ich nicht mit unserm Wirt eine Fußtour ins Gebirge gemacht hätte, die übrigens ganz wunderbar war (Zug-Einsiedeln-Züricher Obersee). Hof- fentlich haben Sie mein erstes Brieferl bekommen, wenn auch nicht grad viel ALS (CLE). This letter may have been en- closed in an envelope addressed in Ein- stein's hand: "Fräulein Mileva Maric Katy bei Neusatz Ungarn." A postmark, "[Me]tt- menste[tten]," is only partially legible be- cause of cropping. The verso of the envelope bears two docketed postmarks: "Ujvidek 99- Aug. 14 8" and "Katy 99 Aug 15." On the verso Einstein's mother has written: "Gruß. P. Einstein." and Maja Einstein: "Ich hätt' Ihnen auch gern geschrieben, aber A. hat's nicht erlaubt. M."  Dated by the reference to Maric's re- ceipt of Einstein's first letter from Mettmen- stetten (Doc. 50).  Robert Markstaller (1865-1933), owner of the Hotel-Pension Paradies (see Staats– steuerregister 1900, SzMet-Ar, IV B 29d).  Site of a famous Benedictine abbey in the canton of Schwyz.