IT was noticed long ago that the special type of interaction between the nucleons and the particles responsible for nuclear forces leads to the possibility of production of many such mesons in one single act1,2. This result has later been disputed, especially by Heitler and his co-workers3, with the argument that the same interaction could possibly produce a strong damping effect as well, which might prevent any multiple production of particles. Jánossy4 then put forward the view that some cascade process inside a nucleus may be responsible for showers consisting of several mesons. The recent admirable progress in photographic technique achieved by Powell and his group5, however, has resulted in most beautiful pictures of the creation of many mesons (very probably π-mesons) in one single act. At the same time, the experiments on local penetrating showers show that these showers are produced in light material, probably also hydrogen, even more frequently than in heavy material6. Therefore it seems natural to analyse the recent experimental data with the help of the old theory.