D O C U M E N T S 2 6 8 , 2 6 9 S E P T E M B E R 1 9 2 8 2 6 5 268. To Leopold Lichtwitz Scharbeutz, 22 September 1928 Dear and esteemed Professor Lichtwitz, I hasten, before my departure from this Dorado,[1] which is very slowly but surely being transformed into a frozen lake, to express my gratitude to you for the kind, dare I say almost paternal, care that you, a very busy man, have lavished on me and my wife.[2] Through your verdict, you have made her almost well again, and also in my case nearly the same is true. But the best thing is that in this way I have become acquainted with you. I wish you, your family,[3] and also your splendid mutts, cheerful and happy times. Your, A. Einstein 269. From Chaim Herman Müntz [Berlin-Nikolassee,] 22 September 1928 Dear, esteemed Professor, With thanks I return your letter, which leads again down the difficult path to the intrinsic mastery of the equations of motion.[1] A great deal of personal misfortune (in particular a lot of illness in my immediate surroundings) has delayed my dealing more intensively with the solution. But now I would like to sketch at least the major difficulties as I perceive them. 1. The overdetermination of 16 functions with 16 partial differential equations through the addition of 4 more is of relatively limited nature and permits in itself countless possibilities to obtain the equations of motion themselves, one will therefore have to look for additional compelling reasons. 2. As a proof, I take the liberty of selecting a particularly delicate point of your relevant discussion. There, on p. 4, lines 5–7, you state: “…, since the solution of the 2nd equation leads to terms proportional to , which can never be solutions of the equation …” The latter, however, cannot really be asserted with such generality it suffices to cite a counterexample, , , r0  0 =   x r   r x  = =  0 =