Welcome Address to the 17th International Cosmic Ray Conference

Abstract

Both Pierre Auger and I are reckoned as being among the last representatives, the last witnesses, the last vestiges of the remarkable days of cosmic-ray research in the thirties. One half-century ago, thanks to the work of Hess, a very weak radiation was already known, whose intensity increased with altitude, but only very little information had been obtained on its nature and its effects. At that time, the detection technique of fast moving charged particles was just beginning to be useful for the study of this radiation. Coincidence arrangements of Geiger counters were developed first by Bothe and Kolhörster, and then by Rossi; the use of Wilson chambers, which were previously triggered at random, was widely extended thanks to the triggering counters conceived by Blackett and Occhialini. A few years later, the practice of “thick” photographic emulsions was completed by Powell, Lattes and Occhialini.