New studies on the radioactivity of the atmosphere

1. I.
   The effect of the gamma rays from the various radioactive substances floating in the atmosphere—previously only estimated theoretically—was determined directly by measuring the total ionization with and without a 1,2 cm. iron plate on top of the ionization chamber which was shielded on the bottom and on all sides by 10 cm. iron. The absorption of the soft component of cosmic radiation in 1,2 cm. iron was taken into account. It was found that the gamma radiation from the radioactive substances in the atmosphere (“air radiation”) amounts, on the average to 0,15I (ion pairs per cm.³·sec) near the ground. It varies considerably from day to day. These variations can exaggerate or mask actual fluctuations which may occur in the soft component of cosmic rays.