7 0 D O C U M E N T S 4 8 , 4 9 F E B R U A R Y 1 9 2 2 could be cured by means of a fifth dimension. While thinking about whether the primary emission proceeds in a spherical wave, the following experiment occurred to me now. Very obliquely incident cathode rays K produce on one of two parallel plates of the same thickness, at A, planar light. The plates generate interference with- out phase differences—provided emission proceeds in a spherical wave. Does a similar experiment exist? A positive result is very probable, however. Warm regards, yours, Einstein 48. To Hans Albert and Eduard Einstein [Berlin, 12 February 1922] My dear boys, You are shrouded in mysterious silence again, you rascals. I am feeling well, but there’s little news. The experiment on which I had placed so much importance proves nothing for and nothing against the undulatory theory, so all the labors of love were actually in vain.[1] Did you send the four photographs that were left over from the 10 + 2 to my friend: Kuno Kocherthaler, 9 Lealtad, Madrid, d[ear] Albert? If not, do it directly, but don’t forget. I still don’t have a sailboat but am on the lookout.[2] It simply has to be a very sturdy one, because everyone is so anxious that my precious life not be put in danger. I’m very keen on spending our summer vacation in my castle (haha).[3] Heartfelt greetings to all three of you from your Papa. D[ear] Albert, please go to the Zurich Kantonalbank and inquire there about why I supposedly have 4,000 marks deposited there and then write me about it. I received from there notification to that effect, which I cannot explain. Ask please when and from whom the money was deposited there. 49. From Hans Albert Einstein [Zurich, between 12 February and 4 March 1922][1] Dear Papa, I really haven’t written you for a very long time now but there are two reasons for it: First, I don’t have any news at all and second, I’ve got quite a lot to do at