D O C U M E N T S 9 7 , 9 8 A U G U S T 1 9 2 0 2 2 7
I didn’t send you anything for your birthday, because it’s extremely complicated
now.[13]
If you have a special wish, though, do write me about it so that I can see
about whether I can fulfill it.
Kisses from your
Papa.
97. From Théophile de Donder[1]
Brussels, 11 Forestière St., 3 August 1920
Sir and highly esteemed Colleague,
It was impossible for me here to procure the report that you published in 1919
(pp. 349–357) in the Berlin
Proceedings;[2]
I nevertheless cited this paper in the en-
closed note: “Théorie nouvelle de la gravifique” [New theory of gravity] (p.
14),[3]
because one of the results that I obtain there offers a strong analogy with a theorem
that appears in the summary of your paper provided in the
Beiblätter.[4]
According
to this summary, I concluded that you have abandoned Hamilton’s general princi-
ple; in my analyses I retained this principle but I modified the generalized force
which you adopt in the study of the atom [which] does not differ essentially from
mine.[5]
I would be very pleased to have your opinion on the subject, and also to be able
to peruse the above-mentioned report. Would it be possible for you to indicate to
me the name and address of a bookseller who would be in a position to supply me
with your publications of 1919, 1920 . . . ? If not, would you be obliging enough to
send me these papers on loan?
In a recent article destined for the Flambeau (a magazine with whose directors
Messrs. Grojean and Grégoire you are acquainted, having received them during
their visit to Berlin), I attempted to present the handsome philosophy that emerges
from your
theories.[6]
Please, Mr. Einstein, allow me to assure you of my utmost respect.
T de Donder
98. To Hendrik A. Lorentz
[Berlin,] 4 August 1920
Highly esteemed Colleague,
If the delay in the appointment matter was painful, it was so only because I was
aware that I caused you, Ehrenfest, and Kamerlingh Onnes an immense amount of