On the Secondary Particles of Local Penetrating Showers

An analysis of the secondary particles of the local penetrating showers has been done by means of absorption experiments and delayed coincidence measurements. The large majority of those particles, filtered with about 12 in. of lead, appear to be mesons, which have been identified as $\pi$-mesons in our preceding paper. The average number of those mesons per shower is about four. The analysis appears to give a lower limit of 1200 g/${\mathrm{cm}}^2$ for the mean free path for nuclear absorption of $\pi$-mesons having energies of some hundred Mev. This result is discussed in connection with other experiments on local penetrating showers.