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JOHN S. BARLOW 



10 20 30 40 50 60 70 80 90 

 Geomagnetic latitude 



Fig. 9. The latitude effect for the ionization produced by cosmic rays at different 

 altitudes. The altitudes 2,000 and 4,360 meters correspond to 6,500 and 14,000 feet, 

 respectively. (From Janossy, 1950, and adapted from Compton, 1933.) 



is somewhat more than twice the energy that corresponds to the rest mass 

 of the proton or neutron and hence is in the range of the threshold energy 

 for production of nucleon-antinucleon pairs (Segre, 1958). It is also in the 

 same energy range as that required for a primary proton to penetrate the 

 atmosphere and come to the end of its path in a thickness of some 10-60 cm 

 of water equivalent (Aron et al, 1949), i.e., to come to rest in the brain or 

 spinal cord of a human in the open air. The greatest biologic effect of 



