Yukawa was a very prudent and tidy person. He stored everything related to research for safekeeping. He sorted the research manuscripts, calculation notes, memos, letters, lecture manuscripts, and programs of meetings and colloquia by subject and saved them in envelopes.

The way Yukawa organized those materials is interesting. He placed documents he had at a given time in a large envelope written with his address for storage. Using a brush, he wrote, for example, “Internal Pair Prod. 1935,” in large letters on the envelope. Yukawa was well-versed in calligraphy, so even his carelessly written English looks beautiful.

The envelopes tell us about the past. For example, the envelope in OU1935-A6 was written with the following address:

Professor Hideki Yukawa
Faculty of Physics
School of Science, Osaka Imperial University
Osaka City

In those days, mail addressed to “Osaka Imperial University, Osaka City” reached the destination without getting lost. There was no need to write the full address including “Nakanoshima” to send mail to Yukawa. The envelope shown in OU1937-C6 was delivered from Tokyo without any problem even though the address was written as follows:

Professor Hideki Yukawa
School of Science, Osaka Imperial University

The envelope in OU1935-A7 was addressed to Yukawa’s residence, “Mr. Yukawa, Kurakuen bus stop, Nishinomiya.” The envelope in OU1936-C3, which was sent from the editorial office of the American scientific journal (Physical Review), was written with the following address:

Dr. Hideki Yukawa
Institute of Physics
Osaka Imperial University
Osaka, Japan

Those envelopes were put into the “Envelopes” category (11 items) of the historical material archive.

Written by: Yutaka Hosotani (Osaka University)

Historical material OU1934-A1

Historical material OU1935-A6

Historical material OU1936-C3