In an experiment utilizing the double cloud-chamber technique at an altitude of 10 600 ft, 46 charged $V$ particles have been observed. Where possible these have been classified according to the value, $p^{*}$, of the momentum of the charged decay particle in the rest system of the primary particle. On this basis decaying particles have been classed as:

1. Consistent with two-body decay of known heavy mesons and not consistent with known hyperons.

2. Consistent with two-body decay of heavy mesons but also consistent with two-body decay of hyperons.

3. Not consistent with two-body decay of heavy mesons.

In the first group it is generally not possible to distinguish between the possibilities $\theta \to \pi +{\pi }^0$, on the one hand and $K_{\mu 2}\to \mu +\nu$ on the other. However, several cases suggest strongly the $\theta$ particle and yield an average mass $953\pm 18m_e$. Several other special decay events are reported. After classification by $p^{*}$, lifetime measurements are made on groups consistent with two-body heavy meson decay. The nine positive events in this class give a lifetime $3.7\times {10}^{-10\mathrm{}}<\tau <8.5\mathrm{}\times {10}^{-10\mathrm{}}$ sec with 50% confidence limits, and 7% probability that $\tau >5\mathrm{}\times {10}^{-9\mathrm{}}$ sec. The six negative events in this class give a lifetime $3.0\times {10}^{-10\mathrm{}}<\tau <8.0\mathrm{}\times {10}^{-10\mathrm{}}$ sec with 50% confidence limits and 11% probability that $\tau >5\mathrm{}\times {10}^{-9\mathrm{}}$ sec. Effects of possible biases are discussed and it is concluded that these lifetimes characterize the charged $\theta$ meson. No unambiguous examples of the $K_{\mu 3}$ or $K_{e3\mathrm{}}$ heavy mesons were observed.

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