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Abstract
The flux of protons in the primary cosmic radiation has been determined in a stack of nuclear emulsions exposed during 1954 over northern Italy. This determination, which depended on the observation of the nuclear interactions produced by the protons, gave a flux at the top of the atmosphere of 500±70 protons/m2 ster sec, a value in good agreement with that expected from counter measurements. A simple model of the variation of the proton flux with depth in the atmosphere has been derived which appears to be in reasonable agreement with the experimental data.