3 0 4 D O C U M E N T S 3 0 2 , 3 0 3 A U G U S T 1 9 2 4
302. To Elsa Einstein
[Lautrach Castle,] 14 August
Thank you very much for your good reports. With such good weather, you’ll cer-
tainly be rested soon. Here it’s very nice. I even did some experiments. All are hav-
ing a good time. Mr.
downright boisterous. Tomorrow Willstätter is
to my great delight. Sunday I’m going to see
about your probing into G.
Take it easy and enjoy yourselves. I’m no longer
going to be able to make it there, though; it would be too much of a good thing.
Warm regards to you and Margot from your
303. From Peter Pringsheim
Munich, 19 Arcis St., 17 August 1924
Dear Professor Einstein,
Since we stopped work in Berlin a few days ago, I would still like to send you a
brief report about our admittedly unsuccessful attempts at the experiment you had
We were working with steel spheres of ca. 30-mm diameter that were
suspended from a fine iron wire. In order to be able to fine-tune the oscillatory and
rotational periods precisely, part of the suspension wire was etched slightly thinner
so that, by lengthening that end of the wire around an angle iron, the swinging os-
cillation period increased very much more strongly relative to the rotation period,
whereas given a constant wire thickness the two are, of course, necessarily coupled.
When the sphere was later magnetized, the conditions naturally did have to be cho-
sen differently because of the added directional force. We initially managed, after
some preliminary trials, to suspend the unmagnetized spheres such that, despite
good tuning, they could be set into a swinging oscillation without also gradually
starting to rotate at the same time as a result. It was revealed, as would be expected,
that any possible asymmetry in the suspension must be avoided, as e.g., even a mir-
ror attachable above the spheres. Instead of that, we marked a line on the well-pol-
ished and reflective sphere which, when no rotation is present, had to stay perma-
nently congruent with a mark reflected off the sphere’s surface. For the
unmagnetized sphere, this succeeded completely for many minutes at a time (at an