A lengthy experiment in which simultaneous measurements of ice nucleus concentrations have been made continuously at 24 places in Eastern Australia is described. The main results show: (1) no association of ice nuclei active at–15C with terrestrial or volcanic dusts; (2) a close association with rainfall; (3) a tendency for high concentrations to occur in an east-west band or bands; (4) a strong lunar control of ice nucleus concentrations. The implications of these results are discussed.

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