Abstract
Interaction mean free paths of relativistic secondary particles emitted from interactions of heavy primary cosmic-ray nuclei in emulsions were measured. The results show that among the Be, Li, He, and singly charged secondary nuclei there are particles present which interact with a cross section several times higher than the expected geometrical value. The stars produced by these particles have the characteristics of ordinary nuclear interactions. There appears to be no interpretation of these observations in terms of any known particle phenomena.