Compared with freshwater ice, whose physical properties are well known, sea iceis a relatively complex substance whose transition to a completely solid mixtureof pure ice and solid salts is completed only at extremely low temperaturesrarely encountered in nature. The physical properties of sea ice are thusstrongly dependent on salinity, temperature and time. Many of these propertiesare still not fully understood or accurately known, particularly those importantfor the understanding of a natural ice cover. The specific heat for example isan important term in the calculation of the heat energy content of a cover.However, Malmgren (1927), whose calculatedvalues of the specific heat of sea ice are in general use, neglected the directcontribution of the brine present in inclusions. Re-examination of thequestion of specific and latent heats of sea ice has led to distinguishingbetween the freezing and melting points and enabled significant observations inthis range. Similarly, because the thermal conductivity is a necessary parameterin the description of the thermal behaviour of ice. the sea-ice modelsuggested by Anderson (1958) has beenmodified and extended in the present work to the case of saline ice containingair bubbles. This enabled the completion of calculations of density andconductivity. In order to illustrate the theoretically calculated values.measurements were made on sea-ice samples to determine the specific heat,density and thermal conductivity.