A magnet cloud chamber recently constructed at Yale University was operated at mountain altitudes (Climax, Colorado, elev. 11 200 feet) during the late fall of 1952. The cloud chamber was electronically controlled to photograph penetrating shower events initiated by high-energy cosmic rays. Five examples of neutral V-particle decays have been observed. One photograph reveals the decay of two V20 particles that probably originated in a single nuclear interaction. Secondary particles in the penetrating showers have been examined for sign of charge. From the positive-to-negative ratio of charge of the secondary particles, it has been determined that 30 percent of the observed proton-plus-meson secondary particles are protons. This percentage is a lower limit, but is probably close to the actual value.