3 1 6 D O C U M E N T S 2 9 8 , 2 9 9 J U N E 1 9 2 6 298. From Emil Rupp [Heidelberg,] 1 June 1926 Dear Professor, It just occurred to me that for experiment c), a zero may have been forgotten in the figure for the grating distance.[1] In any event, it must read: Distance lines + gaps 0.005 cm. Just to reiterate: In my letter from yesterday the grating distance is indicated as line + gaps, in all earlier letters, by line or by gap, as the case may be. Respectfully yours, E. Rupp 299. To Emil Rupp [Berlin,] 3 June 1926 Dear Mr. Rupp, The experiments that you are telling me about in your letter of 31 May[1] are completely satisfying and to be viewed as a convincing confirmation of the theory. In fact, according to the theory, the distances between the maxima of the interfer- ence pattern should be[2] a) b) c) , which matches your experiments perfectly. If we can also succesfully conduct the experiment with the lens, then no doubts remain about the correctness of the theory actually, as it is now, there already are none. If you can keep your paper short enough (not to exceed one printed sheet), we could publish both papers in the Sitzungsberichten der Akademie, or else in the 0.02 3 1010- ⋅ 1.9 107 ⋅ ------------------- ⋅ 31.5 cm = 0.01 3 1010 ⋅ 1.9 107 ⋅ ------------------- - ⋅ 1.7 cm = 0.005 3 1010 ⋅ 1.9 107 ⋅ -------------------- ⋅ 7.8 cm =