AbstractAccurate measurements by electrical means of temperatures at various levels in shelf ice, glaciers or ice caps are of themselves insufficient; they must be accompanied by data on densities at the same levels and on incoming and outgoing radiation, as well as other things. Depths of measurements must be known accurately, and changes in them due to changes in surface level must be recorded. Levels chosen should be, 1, 2, 4, 8, 16, 32 and 64 m., and readings (if repeated to ensure

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... need be taken only once daily down to 4 m. and weekly or so at lower levels. Measurements should be free of external influences such as heat from buildings or deep drifts. Only when all other necessary data are available and all precautions observed will it be possible to explain the thermal structure of the ice sheet as shown by the sub-surface measurements of temperature.