If th(' ict> is 20.000 years old . then the bo ttom tempcnll ures in these three different cases would b e. respectively, -4 ' 9° C. , -12 ' 7° C. and -5' 5 ~ C. H O\\"'ver b ecause of the loss of geothermal h eat through th e ice, especially in the early stages, the actual temperatures would be several degrees lowei·. There is , however, considerable doubt whether Mr. Fisher's "bubbly" ice would b e similar to that found at the great pressure existing under 3,000 m. of ice. At the bottom of

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... Maudheim hol e at 100 m., Schytt 4 found ice of density 0·885 containing air bubbles, mostly round , with a mean diameter of about o' 5 mm. At a pressure 30 times greater , the air bubbles would be even smaller and hence the effect on thermal conductivity probably negligible. It is hoped that further light on trus problem can be cast by measurements of thermal conductivity on the ice recovered from 300 m. in the Byrd hole.