Neutrons in the Extensive Air Showers of the Cosmic Radiation

Neutrons associated with extensive air showers have been studied by recording delayed coincidences among Geiger-M\"uller counters and proportional B${\mathrm{F}}_{3}$ counters. The experiments have been performed at 260, 3260 and 4300 m above sea level. It has been shown that in the extensive showers both neutrons of moderate energies and radiations capable of producing such neutrons are present. The number of neutrons and neutron-producers in showers of different sizes is roughly proportional to the number of the electrons. The neutron-producers cannot be, at least in a large fraction, either electrons, or photons, or $\ensuremath{\mu}$-mesons. Nuclear interactions induced by fast neutrons and protons are consequently thought to give the main contribution to the neutron production observed. The total neutron-producing-radiation is of the order of 2-3 percent of the electronic component of the showers at 3260 m. Its altitude variation is consistent with the assumption that nucleons constitute its main component.The multiplicity of the neutron production in lead is very high: \ensuremath{\sim}60 neutrons of energies between 2 and 15 Mev are produced at a time on the average.