D O C U M E N T 4 5 3 J A N U A R Y 1 9 2 7 4 4 7 You will now probably soon see Zangger there again give him my cordial re- gards, and I thank both of you together warmly. —But from you ¢I hear² I haven’t heard anything at all since! I imagine that the incorporation of the speed of light and of electric and magnetic forces into Schrödingerism is keeping you in suspense.[4] Did I already tell you the recent news about my number mystic, Dr. Beck,[5] the chemist? In one of his heat generation formulas for chemical compounds, the log nat plays a role, of course: log nat .[6] Something that seemed funny to him: for compounds in which the largest contrac- tion ever to occur takes place, this log nat = 1 and the volume ratio is between 2.68 and 2.72. The compressibility of solid and liquid substances leads to the same order of magnitude for the internal pressure as in the chemical case, and both agree in order of magnitude with the electron velocities in the hydrogen atom.[7] But strangest are his discovery of those integral-number issues, and most im- portant practically: the criterion for polymerization. Schrödingerism with a lot of variables? Warm regards from your Mich[ele] The other Beck[8] sent me his Schrödingerism on the photoelectric effect[9] (manuscript)—I don’t know whether it has meanwhile appeared. Seemed good to me! 453. From Paul Ehrenfest Leyden, 13 January 1927 Dear Einstein, Your willingness to remain connected to our faculty[1] is going to be received with great jubilation by everyone involved, because we all were very sad, although all of us naturally—or, precisely because we naturally—certainly grasped that you must successively shake off those kinds of duties. But now, of course, everything is in the best of order!!! IT IS NOT TRUE that, as you write, “from a particular number of molecules on” (from a certain density on), “an increasing number of molecules lacking in energy” should result. There is absolutely no such thing as a singular density at which volume of the components volume of the compound ---------------------------------------------------------------