In a continuation of a study of slow, penetrating cosmic-ray particles at sea level further evidence has been obtained for long-lived particles with mass $\approx \left(\frac{9}{2}\right)m_p$ and charge either exactly or approximately equal to unity. Also, in relatively complicated events, further possible examples of slow, accompanied, heavy particles with charge ≈ 0.7 were observed.

• Received 20 May 1980

DOI:https://doi.org/10.1103/PhysRevD.23.1207