D O C U M E N T S 4 1 8 , 4 1 9 M A R C H 1 9 2 9 3 8 1 418. To Leo Kohn Berlin, 2 March 1929 Dear Mr. Kohn, In my opinion, a meeting of the board of trustees is not necessary for the official implementation of my resignation.[1] The board of trustees is a permanent institu- tion and is capable of receiving messages at any time. I would therefore consider it incorrect for you to continue to include my name on the list of members of the board of trustees and the academic council.[2]— Kind regards, your A. Einstein 419. From Norbert Wiener and Manuel  Sandoval Vallarta[1] Cambridge, Massachusetts, 2 March 1929 Dear Professor, As soon as your new article on a unified field theory of gravitation and electric- ity appeared, we started working on it,[2] and we have now arrived at results that appear somewhat paradoxical to us. Following the model of Schwarzschild’s solu- tion to your earlier theory, we investigated the case of a spherically and temporally symmetric static field, and have proved, if we are not in error, that this case leads to impossible physical consequences. May we ask your opinion of this result? Our enclosed note will soon appear in the Proceedings of the National Academy of Sciences.[3] One of us is well known to you as a student in Berlin, when he attended your lectures in 1927/1928 the other had the great pleasure of being your fellow passen- ger in the same compartment between Basel and Geneva.[4] We are very pleased to hear that your health now permits you to resume your scientific activities. Respectfully and sincerely yours, Norbert Wiener M. S. Vallarta