Cosmic-Ray Investigations on Mt. McKinley

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Abstract
Three cosmic-ray experiments were carried out on Mt. McKinley (Alaska) at an altitude of 18,100 feet. The first experiment measures the absorption curve of penetrating particles in Pb thicknesses up to 50 cm. A large number of slow mesotrons of energies around 200 Mev was found. From the measured mesotron energy spectrum on Mt. McKinley a calculation was made to determine the spectrum which would be anticipated at 14,250 feet (Mt. Evans, Colorado). The result is compared with experimental data obtained on Mt. Evans. The discrepancy between the two curves strongly indicates that an additional production of mesotrons of energies less than 400 Mev takes place in the atmosphere between these altitudes. The other two experiments at 18,100 feet investigate the production of penetrating particles by ionizing and non-ionizing radiation in lead and paraffin.