With radio methods devised as a part of a program for development of radiometeorographs, it has been found possible to record the response of a Geiger-Müller tube counter to cosmic rays at altitudes up to 116,000 feet. Records were made automatically by means of a recording receiver at a ground station. The results show a gradual rise in cosmic-ray intensity which is clearly evident at a pressure of about 500 millibars and then decreases slightly at a pressure of about 300 millibars after which the rise to maximum intensity at a pressure of about 100 millibars is very rapid. This maximum is about 150 times the count recorded near the ground level and is followed by a rapid decrease in counting rate at pressures below 100 millibars. At the highest altitude reached, approximately 116,000 feet, where the pressure is only 5 millibars, the counting rate falls to a value which is about the same as that observed at a pressure of 600 millibars. The general trend of these observations indicates that as the limit of the atmosphere is approached the counts continue to decrease, confirming the view which has been put forward by other observers that the greater part of cosmic-ray phenomena are due to secondary effects generated within our atmosphere.

• Received 8 November 1937

DOI:https://doi.org/10.1103/PhysRev.53.23