I cannot say how glad we are for the good news about the chances for the University post in Copenhagen, and how thankful I am for all what our friends have done for me. I look forward so much to come home and take up the work. We had quite given it up for this year, and it came therefore as a great surprise indeed, as you will have understood from our letters and especially from those about the invitation from the University of California.

Although I had not quite made up my mind whether it was right to accept it in my age and with my small knowledge, we were beginning to look forward to go, and I wrote to Prof. Lewis and said that I hoped to be able to go, but could not give a definite answer at once, as I was due to return to my post in Copenhagen in September next. I told him that I had written to Copenhagen and hoped to receive a reply in about a fortnight, and that I should answer the University of California definitely as soon as I got a reply from Copenhagen. All the time, however, I thought this only a matter of formality, as I never really expected the professorpost to come this year, and thought I should easily be able, on the invitation to California, to obtain leave from my lectureship.

Now of course the whole question is quite different, and I understand quite well that it may not be possible to go. I should be so very glad if you as soon as possible would write and tell me what you think about it all, what you would do in such a case, and whether you think it best to refuse the invitation at once. I am so sorry allways to make so much trouble, but I must decide very soon what to answer the Californians.

We are so glad for all mothers letters and do not know how to thank her; I hope you are all well, how shall it be nice all to meet again. I should like so much to hear about your work, and how the book is progressing; how an immense work it must be. How I also wish I could speak to you about my own things. You heard that Sommerfeld has written an exceedingly important paper, which form a generalisation of my speculations, by which it is possible to explain a very great number of things, f. inst. the fine structure of the hydrogen and helium lines. I had thought a little over it, without being able to solve it, and Evans had made some very interesting experiments about it. Evans has written a letter to “Nature”, and I shall send it in a few days together with a letter to Sommerfeld. I have waited so long because I have worked very hard with an improvement of my paper, which already was in type. I thought I had succeeded in bringing all Sommerfeld’s results into the scheme of my paper, and even to improve them from a certain formal point of view. But then I found a difficulty, which, I think, I suceeded in solving, but which disturbed certain analogies used essentially in my paper. I therefore went down to London on Saturday to speak with the Editor of the Phil. Mag. and to get him to postpone the paper, so that I could really get time to think it all over. At present I do not know exactly what to do, not with the matter but with the form of my paper, but next Wednesday my lectures stop for this term and I shall get more time. Now I must end for this time with my kindest regards and our best love to you all. Will you also remember me to all friends you meet (Hansen f.inst). I am dreadfully ashamed not to have written to anybody for a long time, but I have really been very busy. When I thinkA of it, shame is not an adequate word, for the horror I feel when I get to think of Edgar f.inst; and especially of Ole! Think, I have never written to him, but at first I expected to hear from him, and then I thought it too late to write, and now I am waiting for something “impossible” to turn up to change the situation.