The Encyclopedia Americana (1920)/Regelation

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REGELATION, rē-jē-lā'shȯn, a phenomenon observed by Faraday in 1850, namely, that two pieces of moist ice placed in contact will freeze together, even in a warm atmosphere. It is proved that beside the pressure from the weight of the upper piece of ice there is atmospheric pressure holding the two pieces together; this pressure melts the ice at the parts which bear on one another, and thus enough heat is absorbed to produce regelation. A snowball is formed by the regelation of the particles composing it; so also are the snow bridges spanning chasms on high mountains. The phenomena or regelation are easily seen in the making of snow balls, which is well known to be impossible, by the hands at least, when the snow has been exposed to great cold, and is therefore dry. Professor Thomson's discovery, that the freezing-point is lowered by pressure, explains the motions of glaciers and the apparent plasticity of ice under pressure.