490 APPENDICESents were awarded after Einstein had left that country. In 1927 Einstein autho-
rized Szilard to apply in his own name for patents abroad of some of their joint
ventures [E28].
A detailed discussion of these patents is found in Szilard's collected papers
[F4].* Briefly, the task Einstein and Szilard had set for themselves was to devise
a noiseless household refrigerator. Their principal novelty was the so-called Ein-
stein-Szilard pump, later described by Einstein in general terms. 'By means of an
alternating electric current, a magnetic guide field is generated which moves a
liquid mixture of sodium and potassium. This mixture moves in alternating direc-
tions inside a casing and acts as the piston of a pump; the refrigerant [inside the
casing] is thus mechanically liquified and cold is generated by its re-evaporation'
[E29]. It appears that the inventors received a modest amount of money for their
work [S7], but it did not make them rich. 'As it turned out, such refrigerators
were never commercially utilized because of the rapid advances made in mechan-
ical refrigerators which eliminated their objectionable noise, the dangers from
leakage of the poisonous refrigerant, and erratic operation' [F4]. However, there
were other applications. 'For many years there did not appear to be any other
practical use for such pumping systems, but with the advent of atomic energy their
need became evident (first to Szilard), and much effort has since been expended
in their further development' [F4].
In 1933 Szilard went to England. In 1938 he settled in the United States. His
first position was at Columbia University. He then moved to Chicago, where he
participated in the first nuclear reactor project. In 1946 he was appointed profes-
sor of biophysics at the Enrico Fermi Institute in Chicago. 'In his work in biology,
Szilard finally reached his full potential' [W2]. He had a strongly developed
political conscience. On August 2,1939, he and Eugene Wigner called on Einstein
to urge him to bring the need for action on the development of atomic weapons to
the attention of President Roosevelt. This visit led to the letter drafted and signed
by Einstein which was handed to Roosevelt on October 11, 1939. Later, Szilard
suggested that Einstein write a second letter to the president, urging him to speed
up these activities. A letter to this effect was sent on March 7, 1940. d. 1964,
Lajolla, California.
- Rudolf Goldschmidt.** b. 1876, Neubukow (Mecklenburg-Schwerin),
Germany. Engineering diploma in 1898. From 1899 to 1909, Goldschmidt
worked in England with such electrotechnical firms as Westinghouse. Upon his
return to Germany, he became first Privatdozent, later professor, in Darmstadt.
One of his main achievements was the invention of the high-frequency apparatus
•See also [K3], [M4], and [M5]. The Swiss patent is mentioned in [F5] and [M5], not in [F4].
**I am grateful to Professor Goldschmidt's daugther-in-law Rose Goldie from New Maiden, Surrey,
England, and to Horst Melcher from Potsdam for information which was of great help to me in the
preparation of this note on the Einstein-Goldschmidt patent. I first became aware of this patent
through Professor Melcher's papers [M4, M5],