Curious Formation of Ice

IN NATURE of December 12, 1912, was published a letter wherein I described a curious formation of ice the hope that some of your readers would be able explain the cause, but there was no reply. After five years the formation occurred again in similar circumstances, and I submit a partial explanation which occurred to me on seeing this second example the phenomenon. The ice was again formed on water in a rough hole or pond (about 2 ft. by 1 ft.) the garden in clay soil. it was observed at 3.30 p.m. on January 13, 1918. The ``dark, sinuous lines'' in this case were about¼in. wide, and again ran ``about parallel to the major axis'' of the small pond. These dark lines were again due to the ridges ice on the under-side of the ice covering the water, but were closer together than before, being about 1½ in. apart. The cross-section of the ridges was again of ``dovetail'' shape, the attachment being at the smaller end of the ``dovetail.''