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157. From Jean Perrin
[Paris, after 5 November
My dear Einstein,
I wrote to the officer in charge of the prisoner-of-war geologist in whom you are
interested, urging the mildest treatment
Besides, I cannot believe that,
peace having been signed, you will have grounds to worry. The treaty is, I hope,
going to go into force, and liberation is undoubtedly a question of days or weeks.
I was overjoyed when I learned, some days ago, of the success of the observa-
tions on the deflection of light in the sun’s gravitational field. It is definitely one of
the grandest things achieved for many centuries. And I congratulate you with all
my heart. It is a great day in the history of science.
As regards my reflections on light and chemistry, one can but wait for definitive
confirmation by experiment. But I have scarcely a doubt. Too many facts are com-
ing to light already for it to be a matter of simple chance.
I do indeed believe that I2 decomposes like radioactive bodies (and I devoted a
chapter of my work to this) but precisely on the conviction that radioactive bodies
like I2 are decomposed by light (for radium, ultra-short X rays emanating from the
Earth at λ =
(light which suddenly increases the internal
I read your letters to Mrs. Curie and to
They too send you their very
Yes, I do hope to see you again soon. The moment you see a favorable opportu-
nity, let me know. Langevin and I, and Weiss, we all shall be very happy to hold a
small scientific conference with you, when traveling is a little
meantime, let’s continue writing each other.
I did receive your book. Thank you.
Francis was the 1st to be accepted (at the age of 16½) at the École normale (sci-
He will be a better physicist than his father.
158. To Theodor K. von Wasielewski
6 November 1919
[Not translated for this volume.]