1 6 4 D O C . 1 9 2 D E C E M B E R 1 9 1 9 D[ear] Adn, I don’t think that the propeller should be tilted more. If it has too little power, that’s due to the motor, in my opinion. Such a thing can’t be calculated, especially since during start-up (at rest against the air) completely different condi- tions prevail than during flight. I’m glad that you are taking lessons with Amberg. He’s a very nice man. Please give him my regards, if you don’t mind doing so. He was assistant to Hurwitz when I was a young stripling of a student. In those days he examined me at the review sessions. He was still very young. Seiler was also an assistant in the physics building when I was a student. He appealed to me less and even then already had a portly little paunch. I have to be in Basle 14–16 Jan- uary regarding the university to be established in Palestine. If it’s possible, let’s see each other then. Affectionate greetings to both of you from your Papa. 192. To Willem H. Julius [Berlin,] 5 December 1919 Dear Colleague, The wonderful day I spent at your house will remain with me as a lasting mem- ory, to be treasured not only for the scientific enrichment but also for the personal experience. I have been thinking your theoretical interpretations over in my mind and am convinced that they deserve to be taken into account most seriously. There is no sense in discussing redshifts without carefully taking into consideration the line displacements through asymmetric scattering that you have introduced. The line displacement between the solar center and the solar limb is clearly evident. Likewise, your so plausible explanation for the S-shape of the sunspot spectrum with a radially positioned slit shows that continuous refraction may also play a role. I have not been able to study all of your papers yet, because currently I’m being harassed by such a great variety of duties, scientific and otherwise, that I find it difficult to immerse myself properly into anything. Hopefully, things will soon improve again. There is now the prospect of my coming to Holland more often and [?] being able to keep up the scientific, personal, and musical relations with you and yours. Music making with your daughters and Ehrenfest was so very nice! In sending all of you my most cordial regards, I am, with best wishes to you and your family, yours, Einstein.