4 6 D O C U M E N T S 5 0 , 5 3 F E B R U A R Y 1 9 2 1
50. To Johannes W. Classen[1]
Berlin, 17 February 1921
Dear Colleague,
Your information naturally interested me very
much.[2]
I recommend, however,
in any case that you use great caution in interpreting your experiments. The phe-
nomena for magnetically hard bodies complicate quantitative evaluation of the data
by the phase shift between magnetization and field as well as by the slowness of the
process of magnetic reversal. It might be sensible to effectuate the magnetic rever-
sal by short pulses of current. Your interpretation of an external release of a part of
the angular momentum of atoms undergoing gyroscopic motion conflicts with a
careful series of measurements by Dr. Beck in Zurich, who found that massive rods
and rods contained in a wire bundle behaved entirely
identically.[3]
Did you take
great care in compensating for the earth’s magnetic field? Errors caused by residu-
als of the terrestrial field are particularly dangerous when using magnetically hard
bodies, because of the complicated phase conditions. Looking forward with great
interest to further reports from you, amicable regards, yours.
51. To Eduard Schweigler
Berlin, 17 February, 1921
[Not selected for translation.]
52. From Max M. Warburg
Hamburg, 18 February 1921
[Not selected for translation.]
53. To John G. Hibben[1]
Berlin, 21 February 1921
Highly esteemed President,
I thank you for your kind letter of 24 Dec.
1920.[2]
The situation has meanwhile
changed for me insofar as I am compelled to travel to America at the invitation of
the Zionist organization in the middle of March, because of the founding of the uni-