D O C U M E N T S 4 0 4 , 4 0 5 N O V E M B E R 1 9 2 6 3 8 5 404. To Emil Rupp [Berlin,] 5 November 1926 Dear Mr. Rupp, I took the liberty of deleting the last sentence before the “summary” in your paper because the assertion mentioned in there is incorrect. The irregular addi- tional velocities (e.g., the thermal ones) in the canal ray bundle can never be cor- rected by means of rotating the mirrors (in particular the components ⊥ to the canal ray velocity). If you wish to insert anything regarding the aforementioned, you have to request an additional correction proof sheet. It is not clear yet why interfer- ences of such a large phase difference are possible. Discuss it with Frank. Kind regards, your A. Einstein Translators’ note: Based on a translation by Doris Lonk and Tilman Sauer. 405. From Heinrich Zangger Zurich, 6 November 1926 Dear Friend Einstein, Thank you for your letter. Your warm invitation to Berlin comes in addition to a succession of invitations and letters that proved to me that, on the one hand, peo- ple in Berlin know me better than I anticipated and that, on the other, goodwill ex- ists to a great extent so that I can in no case reject the call without further scrutiny as to what is wanted from me and what I can accomplish under the existing conditions. I came to Berlin on 26 September as a completely unknown personality (as a Swiss delegate to the meeting of the international criminal police organization) and did not encounter a single acquaintance in Berlin. I had, however, already on 30 September a rather clear opinion, promises from several Prussian and, above all, Reich ministers, who gave me an almost overwhelming image of the will for in- sight, of the drive and the energy to put the insight into practice quickly such that, as a result, the call to Berlin is already for me a great experience and already virtu- ally guarantees the prospects for development of the specialties and of the great leading-edge tasks for medicine in law. Of course, I need your advice in many areas before I decide on any direction. I will notify you immediately after my arrival in Berlin so I can discuss the situation with you.