Arcetri, 1928 -1932

Early in 1928, a short time after receiving my doctorate at the University of Bologna, I was offered a position of assistant at the Physics Institute of the University of Florence. The Institute rose among olive trees, on the hill of Arcetri, a short distance from the villa where Galileo had spent the last years of his life as a political exile. The chair of physics was held by Professor Antonio Garbasso (Fig. 1) who, in earlier years, had done some creditable scientific work. But the first world war and the events of the post-war period had diverted his interests toward politics. He was now a senator and the mayor of Florence. However he still went to Arcetri three times a week to deliver his lectures and he still had a strong desire to see the Institute, which he had built, become an important center of research. The group I found in Arcetri was quite small, but quality made up for size. Gilberto Bernardini (Fig. 2), a recent doctor in physics from the University of Pisa, had joined the group a short time before my arrival. Among the students, were Giuseppe Occhialini, Giulio Racah, Daria Bocciarelli, Guglielmo Righini, and Lorenzo Emo. And we had the benefit of regular visits of Professor Enrico Persico, who had undertaken to unravel for us the mysteries of wave mechanics. Life at Arcetri was rather austere. My monthly salary was 600 lire (30 dollars at the then current rate of exchange). Not enough money was available in the laboratory budget to buy heating fuel and winters in Florence are quite severe. To combat the cold, we would wear heavy woolen linings inside our laboratory smocks. The laboratory was always far behind with the payment of the electric bills, and the only reason why our electricity was not cut off was that the director of the laboratory was also mayor of the city. Both Bernardini and I were very anxious to start some experimental program, and we spent our first year in Arcetri exploring, without much success, a few different lines of research. For me, the turning point in the search came in the fall of 1929, with the appearance, in Zeitschrift fUr Physik, of the historical paper "Das Wesen der Hohenstrahlung" by W. Bothe and W. Kolhorster (Bothe and Kolhorster, 1929) Until then, I had not been particularly interested in the phenomenon of the "Hohenstrahlung" or "cosmic radiation," using the suggestive expression introduced by Robert Millikan. I had not thought that it would offer, to me at least, a profitable field of research. I had not been seduced by Millikan's well publicized theory, maintaining that cosmic rays were the "birth cry of atoms" in cosmic space, being born, in the form of r-rays, when hydrogen atoms "fused" to form the heavier elements. To my skeptical mind, this was a romantic idea, lacking sound experimental support. On the other hand, I had accepted, uncritically, the prevailing view that primary