  In 1934 Enrico Fermi accepted an invitation to deliver lectures in Argentina,
Brazil and Uruguay. He arrived in Buenos Aires on July 30, lectured in Buenos
Aires, Cordoba, La Plata and Montevideo, and then moved on August 18 to Sao
Paulo via Santos and Rio de Janeiro; he traveled back from Rio to Naples on
September 1st. His visit had a large resonance, and halls were crowded despite
the fact that he lectured in Italian. The University of Buenos Aires recorded
his five lectures and transcribed them in Spanish. They contain the first
public presentations of the theory of beta decay and of the works on artificial
radioactivity started by the via Panisperna group, but are not included in
Fermi's Collected Works edited by the Accademia dei Lincei in Rome and by the
University of Chicago, although listed in the Bibliography. In this paper we
present the transcription of Fermi's five lectures in Buenos Aires, a summary
of the lecture in La Plata and an extended summary of the lecture in Cordoba,
translating them in English for the first time.
