Thirty-four "forked tracks" similar to two previously reported by Rochester and Butler have been observed in 11,000 cloud-chamber photographs of cosmic-ray penetrating showers, confirming their conclusion that new unstable neutral and charged particles exist. The lifetime of the neutral particles is found to be about 3×${10}^{-10\mathrm{}}$ sec., and some information as to the nature of the decay products is given.

• Received 6 March 1950

DOI:https://doi.org/10.1103/PhysRev.78.290