In 1879 Crookes discovered that air seemed to ionize spontaneously. With the discovery in 1896 of radioactivity by Henri Becquerel, it appeared that the mystery was solved. However a number of physicists sought a quantitative agreement between the ”spontaneous ionization” and the radioactivity in the earth. The persistence of these physicists led to the discovery of another source of radiation which appeared to come from the heavens. The nature of this ”cosmic radiation” involved phenomena that were completely unknown. Coming to an understanding of the nature of this cosmic radiation took about 40 years between 1912 and 1953. This history involves extraordinary scientists and the invention of dramatic new detection techniques. This story finishes with a remarkable conference organized by Patrick Blackett and Louis Leprince-Ringuet (1953) in the Pyrenees town of Bagnères de Bigorre. Following 1953 the cosmic ray researchers divided into two groups, those who continued the investigation of the new particles with the accelerators and those who continued with the search for the origin and the astrophysics of the cosmic rays.