After introductory observations on the phenomenon of the overheating of crystals and on previous investigations of Tyndall stars produced by radiant overheating of single-crystals the heating of ice in a high-frequency electric field is described. From the measured temperature increase up to the melting point the overheating caused thereby in ice is estimated to be at least 0.3°C. Tyndall stars were observed and an attempt is made to explain their genesis and behaviour. The considerations of W all on the dynamics of the growth of snow crystals may also be applied to Tyndall stars.