Sir,

I have seen Professor Cailleux’s letter, and would say that the phenomena described by him are similar to the “icings” which commonly form on rivers and lakes in Siberia. One of the ways in which the water which feeds the “icing” is forced up from under the floating ice, is by the pressure caused by the freezing process itself; as the floating ice on the surface grows thicker, the water beneath it (if there is no outlet) may be forced up through a crack in the ice into the open air, where it freezes at once. The mound thus formed can look very like those in the photographs.

A very general description is given in P. A. Shumskiy’s Osnovy strukturnogo ledovedeniya (Moscow, 1955), p. 199–200.