Sir

In reference to the last paragraph of the very interesting comments by Mr. J. W. Glen, of the Cavendish Laboratory, on the paper by the late Max Harrison Demorest (Journal of Glaciology, Vol. 2, No. 13, 1953, p. 219 and 201–3 respectively), the recrystallization induced by deformation in Demorest’s experiments was, in reality, so rapid as to be practically instantaneous. In fact, it was so rapid that the process is recorded in moving pictures that were taken by Dr. Demorest during the course of an experiment. The recrystallization could be observed to have taken place as a sudden change during the passage of a few frames, at minute intervals, of the moving picture film.

Since recrystallization in metals proceeds with variable speed at different temperatures, it may be that the instantaneous recrystallization in ice is caused by the fact that Demorest’s experiments were carried on at temperatures that were relatively near the melting point of ice.