The Editor,

The Journal of Glaciology,

Sir, Polygonal frost patterns

The ice features illustrated in the Figure on p. 290 may be of some interest especially in view of their great similarity in plan to much-patterned ground, a similarity which might provoke speculation upon a genetic relationship. The larger units in the cellular grouping were some 30 in. (0.46 m.) across. They were seen on the morning of 17 February 1958 at Newcastle, Staffs, on a smooth dark tarmac surface. Although the air temperature was below freezing, only in the shade, where the photograph was taken, were the features still intact.

This quite superficial frost growth followed a night of keen frost with clear skies and low relative humidity; there was a strong north breeze. At the time it was not possible to attempt to relate the cells and particularly their nuclei to the nature of the ground surface; but when an examination of the tarmac was made it was seen to have slight undulations on the crests of which there were small polished tar patches. These were the only specific surface details with which the ice nuclei seemed likely to be related and such a connexion was not established. The only other alternative mode of design which suggested itself was a cellular ground level air turbulence such as is thought to have created desiccation polygons noted on Deception Island (1 December 1955).

R. Clark

91 Highcliffe Road, Sheffield, 11 11 April 1958

Polygonal frost patterns, see letter from Mr. R. Clark on p. 328.