2 0 4 D O C U M E N T 2 5 1 J U N E 1 9 2 2 concerns scientific reputation, practical judgment, and energy. Provided, of course, you need an exact scientist. We are expecting Michelson here in a few days, who will be occupied with three projects: 1. Continuation of the interferometric determination of stellar diameters. 2. New measurement of the velocity of light according to Fizeau along a light path of c. 70 km.[5] 3. Sagnac’s experiment with the Earth as a rotating disk.[6] This last is a product of the not-yet-overcome theory of condensation of the ether near Earth. M[ichelson] says: It is not at all astonishing that in Sagnac’s experiment the ether is not dragged along by the air, but it is an entirely different matter when the whole Earth with its enormous mass is rotating, and then the ether could be dragged along. I think it is quite good that he is doing this experiment so that these speculations finally be eliminated for good. I would have liked to come to Europe for the summer vacation but am prevented from doing so for private reasons. However, I do hope to be in a position next sum- mer to feel the pulse of science. Are you thinking of going to Holland this year? If so, do please give my most cordial regards to Lorentz and Ehrenfest.[7] With most respectful greetings, I remain very devotedly yours, Paul S. Epstein. 252. From Gustave Le Bon Paris, 27 June 1922 [Not selected for translation.] 253. From Friedrich Sternthal[1] Berlin, 28 June 1922 [Not selected for translation.] 254. From Emile Borel Paris, 2[9] June 1922 [Not selected for translation.]