1 7 0 D O C U M E N T S 1 9 4 , 1 9 5 M A Y 1 9 2 2 Haber is convinced of the conclusiveness of the Stern-Gerlach photographs. Cordial greetings to all of you, y[our], Einsteins. The Dutch did so much for the expedition. I cannot join them on the expedi- tion. Do you believe that anything is served by my stopping over in Batavia on my return trip (which isn’t possible without a considerable loss of time)? 194. Recommendation for Paul Hertz [Berlin,] 18 May 1922 I have known Mr. P. Hertz for many years through his scientific papers and in person. He is, without a doubt, one of the most discerning theoretical physicists in Germany, with great expertise and remarkable originality. His high degree of general culture should be particularly pointed out, which allows him to appear excellently suited for literary work of a broad-ranging scope. I value him as highly as an intellectual as I do his personality and am convinced that he will complete in a satisfactory manner any mission that he feels confident to take on. A. Einstein. 195. To Gustave Le Bon Berlin, 19 May 1922 Sir, Your note interested me very much. It is truly remarkable that by means of the equivalence of mass and energy you arrived at consequences in conformity with those of the theory of relativity. It would interest me to become acquainted with the method you used. I would appreciate being informed about this point. If you would like to do me this favor, I ask you please to take into account that I have difficulty reading your handwriting. Most sincerely yours, A. Einstein.