2 0 0 D O C . 2 3 6 D E C E M B E R 1 9 1 9 human milieu has become so much more agreeable to me that I gladly put up with the superficial difficulties and little privations that are a part of life here. I know very well that you understand me and that you would do just the same as I. As concerns the periodic lectures, now, I would gladly make this sacrifice if it were objectively justified. But there can be no question of that. I have the definite feeling of being incapable of offering you anything more there with lectures, now that physics is so splendidly represented there.[5] As an independent private person, however, I shall very gladly come and see you all often, in order to dip into that sprightly scientific life of yours and also purely for the personal pleasure of it. We don’t really always have to play the schoolmaster! Added to that, another thing: H. A. Lorentz has offered me a visiting professorship at the University of Leyden, which, although it takes away only a few weeks per year, does make it impossible for me to lecture in Zurich in the envisaged way.[6] This reason is more of a sec- ondary one, though. I answered the inquiry about Bernoulli plainly enough [7] I could not answer a second inquiry about a Genevan because I know neither the man nor his work.[8] The invitation by the government already arrived but I declined for the above reasons.[9] I am also very concerned that contining the Zurich lectures would be a difficult sacrifice for me, especially with respect to my ever unstable health condi- tion. Grebe and Bachem in Bonn have now quantitatively confirmed the redshift of spectrum lines from the Sun.[10] Their measurements agree with those by Schwarz- schild and Evershed.[11] It was only by using the Koch photometer on the spectro- photograms, however, that reliable interpretation became possible.[12] The mea- surements by St. John do deviate, though, and even now still yield only half the effect (0.34 instead of 0.6 km apparent Doppler effect).[13] I am very eager to take up your kind invitation. At the moment, I am hindered from all travel by my seriously ill mother, whom we have taken into our home.[14] But as soon as I can do so, I will come and bring my wife or one of her daughters. With best wishes for the New Year to you and your wife and best regards from my family, I am yours, A. Einstein. 236. To Ludwig Darmstaedter [Berlin,] 29 December 1919 Highly esteemed Sir, I cannot allow myself to make available to the public the letters addressed to me personally during my or their authors’ lifetimes.[1] I am, however, entirely in agree-