22 April 1926
I have just seen from your first article that you really based your considerations on the equation
div grad ψ + constant (E—Φ) ψ = 0
which satisfies the addition theorem for independent systems. So my letter was superfluous.
I see no basic difference between your work9 on the theory of the [ideal] gas and my own. For according to you, too, the state (of equal probability) is characterized by the values of the set of numbers n1, n2, n3, …, where the numbers n1, n2, etc. have the same meaning as they do for me.
I do not understand how you are allowed to use the last form of (4), in your article, since this is not consistent with the condition Σn4 = const.
Best wishes from