2 4 6 D O C . 2 9 4 F E B R U A R Y 1 9 2 0 294. To Paul Ehrenfest [Berlin,] 2 February 1920 Dear Ehrenfest, I have received the 10000 marks.[1] The accounting now looks like this: 16500 marks is what the grand piano costs, 239 marks is the cost of packing, delivery to the train station, and export permit. Remainder is 111 marks,[2] which is conse- quently being applied toward the violins.[3] I didn’t have any other expenses. The violins aren’t ready yet. Your offer regarding the professorship is so fabulous that I just couldn’t get used to it so easily. I have the feeling deep down that I’m obliged to do something for it.[4] You’ll second me in that, not just in “nay-saying.”[5] Progress is slow with the violins, because the man first worked on mine, which is finished except for the varnishing and has come out very nicely. The snag is that the varnish needs a whole year to dry thoroughly and that until then the surface is very sensitive to touch. In any event, I’ll bring you the violins myself so that I can instruct you personally on their care and can fully secure their delivery. I’m going to have the inaugural lecture printed here, as soon as I’ve written it, and will bring the copies along.[6] When should it take place? I can’t go away for a couple of months because I have various obligations here that I can’t abandon, and particularly because I’m unwilling to leave my wife alone with my terminally ill mother.[7] It’s an extremely tragic case: chronic course, acute consciousness, psy- chological depression from the suffering and narcotics.[8] My mind balks at any edition of my papers.[9] Whatever is worthwhile is mostly already assimilated in the literature, the rest is mostly of no interest. Let’s drop it for the time being! The more important papers on relativity are being published by Teubner now, anyway.[10] Weyl has now added his electromagnetic theory to the new edition of his text- book, unfortunately, so this admittedly very ingenious nonsense will make its way into the cerebra.[11] But I console myself that the sieve of time will do its work here as well. Nothing else has worked for me in relat. theory since. The electromagnetic field thwarts all efforts, and an overdetermination with differential equations that do justice to the “horizontal” regularities also refuses to work.[12] But I firmly be- lieve that this will turn out to be the way to true (intellectual) progress. An Italian is supposed to have proved that the equations have as a generally regular solution only the Euclidian one.[13] If this is true, then no boundary conditions are needed at all, not even in the case of an infinite world. But the principle still holds that a finite density of matter demands a finite world.[14] Warm greetings also to your wife and the whole dear little company,[15] yours, Einstein. Rik 0=