THE phenomenon alluded to by the Duke of Argyll in NATURE, vol. xxi. p. 274, is not at all of unfrequent occurrence. I remember having been struck by the beauty of these ice-filaments on dead branches in Epping Forest many years ago, and some friends of mine observed some beautiful specimens of such branches in Surrey some few weeks since. The explanation which I have been inclined to give is the following:—During the moist weather preceding the frosts, the dead branches on the ground become sodden with water; the interstices between the cells of the dead ligneous fibre get saturated by capillarity, and the branches become water-logged. Now if a certain amount of dry weather intervenes between the moist period and the frost, this absorbed water would have time to partially evaporate and leave the branches more or less dry. But if the frost immediately follows the moist period—as pointed out by the Duke of Argyll—there is no time for the drying of the branches, and the interstitial water becomes frozen in situ. Under these circumstances the expansive force of the ice would cause it to flow out from every available pore by virtue of its viscosity, and such I take it is the origin of the filaments observed. Those portions of the branches which are protected by bark are sheathed by the latter in such a manner that the ice is prevented from oozing outwards; but my friends who have recently observed the phenomenon inform me that where the bark was partly separated from the wood beneath it so as to leave a small intermediate space, this space was likewise filled with filamentous ice.
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Cold Regions Science and Technology (1988)