2 2 6 D O C S . 2 7 3 , 2 7 4 J A N U A R Y 1 9 2 0 273. From Charles-Eugène Guye [Geneva,] 21 January 1920 My dear Colleague, Your kind response pleased me intensely and I thank you cordially [1] we shall be particularly happy to receive you in Geneva. So please be so obliging as to notify me sometime of your arrival in advance, once you yourself have set the time of your stay in Switzerland. To my mind, best would be, it seems to me, to offer a discussion of whatever length is convenient to you, presenting the philosophical significance of the new principle, this discussion being intended for a very large audience. Then, if the re- maining time permits, to give some more substantial lectures for more specialized listeners. But this is a suggestion out of inexperience. You ought to know better than any- one what should be said and how it is most suitably said your freedom thus remains full and complete. I was very sensitive to your appreciation of the research at our laboratory con- cerning the motion of electrons and your opinion, together with that of Larmor, who had written me a note in the same vein, gave me keen satisfaction.[2] If the results obtained do appear to me to have some value, I think it should be attributed primarily to the method of identical trajectories[3] which completely eliminates the uncertainties resulting from calculating integrals of the field. Furthermore, the only absolute values to occur are, on the one hand, the currently very well known term , and on the other hand, the discharge potential V for slow rays, which is easily measurable with precision. Finally, the objectivity of photographic registration eliminates any possible autosuggestion. In the hope of soon seeing you again, I extend to you, dear colleague, with my grateful thanks, my most cordial greetings, C. E. Guye. 274. From Friedrich Kottler[1] Vienna III, 4 Streicher Street, 21 January 1920 Esteemed Professor, Indirectly via Amsterdam I learned that a short while ago you kindly made a friendly statement about me and declared your willingness to support me in apply- ε μ0 -----