Symposium sôbre Raios Cosmicos, Rio de Janeiro, Agõsto 4–8, 1941

Abstract

IN this volume are reprinted, in English and French, the papers given at a symposium on cosmic rays held in August 1941 at Rio de Janeiro, under the auspices of the Brazilian Academy of Sciences, on the occasion of the visit of a group of American physicists led by Prof. A. H. Compton. The scope of the conference is indicated by the following titles selected from some twenty papers: (1) "On the Fluctuations of Cosmic Rays", by A. H. Compton; a discussion of the sidereal time variation of cosmic rays. (2) "On the Latitude Effect of Cosmic Rays", by B. Gross. (3) "Cosmic Ray Studies in the Andes of Southern Peru", by N. Hilberry and A. H. Hilberry. This paper describes the determination of the variation in the frequency of extensive showers with altitude, up to 5,850 m. above sea-level, for two different counter arrays, and affords an interesting proof that most extensive air showers are initiated by high-energy electrons. (4) "Cloud Chamber Photographs at High Altitudes", by D. Hughes. (5) "The Latitude Effect for the Hard Component of Cosmic Rays and Evidence as to the Nature of the Primary Radiation", by W. P. Jesse. (6) "The Influence of a Solar Eclipse on the Cosmic Ray Intensity", by Y. Monteux, G. Occhialini and M. D. Souza Santos. (7) "On the Ultra-Soft Component of Cosmic Radiation", by G. Occhialini and M. Schonberg. (8) "Showers of Penetrating Particles under 30 m. of Clay", by P. A. Pompeia, M. D. Souza Santos and G. Wataghin. (9) "On the Production of Mesotrons at High Altitudes", by E. O. Wollan; this interesting paper gives the results of balloon flights to determine the multiple production of mesons as a function of altitude. No maximum is found up to a height corresponding to a pressure of 3 cm. of mercury.