The Mean Lifetime of the Mesotron from Electroscope Data

In order to eliminate some experimental difficulties found in detecting the mesotron decay with Geiger counter apparatus, an experiment which consisted of the measurement of cosmicray intensity at various depths in two lakes of widely different altitude but of the same geomagnetic latitude was performed. One of our self-recording electroscopes which has been used in other cosmic-ray work was used. In the higher lake, about 12,000 ft. above the lower, readings were taken at depths of 4.9, 5.9 and 6.9 meters and in the lower lake at 1.3, 2.3 and 3.3 meters, the difference in depth being about equal in mass to the air between the lakes. On the basis of the most recent theory, air and water were assumed to be gram for gram equivalent absorbers for the mesotrons involved. The ratio of intensities at equivalent points in the two lakes was theoretically calculated and by matching this with the observed ratios a mean rest lifetime, ${\tau }_0$, of 2.8×${10}^{-6\mathrm{}}$ sec. was found for a rest mass of 160 times that of the electron.