The events described earlier showing the production of slow heavy mesons in photographic emulsions were interactions in which many shower particles were also produced. I should like to draw attention to three photographs which have been obtained in a cloud-chamber experiment carried out at the Jungfraujoch by a group from Manchester. These show the production of F-particles in interactions of very low multiplicity. In two of these events (Astbury, Chippindale, Millar, Newth, Page, Rytz & Sahiar 1952) slow-charged F-particles are produced in secondary interactions in a lead plate in the cloud chamber. The only other visible products of these interactions are one and two shower particles respectively. The third event is a star in the gas of the cloud chamber from which a neutral
V
-particle emerges. The total energy of the star is estimated as less than 1010 eV. This event is fully described by Astbury, Buchanan, James, Millar, Newth, Page, Rytz & Sahiar (1953).