Sir,
Results of field work in Antarctica during the 1964–65 season provide new information concerning the relative permittivity of ice at frequencies between 1 and 1,000 Mc./sec., discussed by Reference EvansEvans (1965). Measurements of the velocity of radio waves at 30 Mc./sec. on the Skelton Glacier, where the estimated density (0.907 g./cm.3), is close to that of pure ice (0.917 g./cm.3), yield a value of 168.5±1.0 m./μsec. The corresponding average relative permittivity value of 3.17 tends to confirm Evans’ conclusion that significant V.H.F. dispersion does not exist, in the face of the contrary values reported by von Hippel and Yoshino.
Polarization changes, which had not previously been observed in the field, were noted in echoes through the Skelton Glacier and through 2,800 in. of ice at the South Pole station. These polarization shifts may be related to preferred crystal orientation in the basal part of the ice sheet, and suggest a possible means of obtaining further information about this critical part of the glacier.
