2 7 8 D O C U M E N T 2 6 5 A P R I L 1 9 2 6 . Your very fundamental requirements are thus fulfilled. I am otherwise very grate- ful for this slip of the mind because by your comment an important characteristic of the formula apparatus rose to my awareness. Additionally, it always is elevating to one’s confidence in a formulation if someone—and especially if you construct it anew out of a couple of fundamental requirements.— I recently read with utmost interest in Naturwissenschaften your suggestion for a new coherence experiment.[5] However, I have not finished pondering yet. That always takes a bit long with me. I am not quite sure how you imagine the arrange- ment behind the grating. (“Behind the grating the light is made parallel by another lens …”) I imagine the wire grating in the focus of this other lens and then perhaps a Fabry-Pérot interferometer (plane parallel air plate, rings of equal inclination). One tends to say here: each point of the light source corresponds to a point on the ring image. The grating is the light source. Then light from different grating slits would not be able to interfere at all. But here is where—according to the classical theory—the peculiar case exists that various points of the light source oscillate co- herently in a regular way. It has not become clear to me yet what effect this has. But maybe the arrangement I am continually imagining is foolish. Your charming explanation of meander formation entertained me very much.[6] My wife[7] happened to have interrogated me about this “teacup phenomenon” a few days earlier. But I had no reasonable explanation for it. She said that now she will never again stir tea without thinking of you. Kind regards to you, dear professor, sincerely yours, E. Schrödinger 265. From Michele Besso Bern, Trechselstrasse 9, 25 April 1926 Dear Albert, A couple of months ago I sent you (registered) Mr. Beck’s paper but heard noth- ing about it from you since.[1] Some days ago he wrote me what’s on the verso today we spoke with each other. The result really is striking: instead of RT in the formula indicating the isothermal work of compression for a perfect gas, there ap- pears a series of numbers with simple whole number relations, if the heat produc- tion and the reduction in volume from the chemical compounds with all condensed phases [are taken into account]. If the heat produced is set equal to the product of div gradϕ E Φ-ϕ – h2 ------------- + 0 =