FROST HEAVING is a process by which ice columns can grow like plants out of moist soils. In the Arctic structures as big as hundreds of meters wide and 50 m tall ("pingos") can form in this way. Where does the energy come from to thrust ice upwards against the force of gravity? Hisashi Ozawa, now at the Nagaoka Institute for Snow and Ice Studies in Japan (ozawa@nisis.nagaoka.bosai.go.jp) observes frost heaving in the lab. He grows ice columns above a reservoir of supercooled water (water below its freezing point kept in a liquid state). A microporous filter (approximating the role of Arctic soil) between water and ice keeps the ice from intruding into the liquid. Ozawa believes that newly formed ice is able to push against gravity not through any conventional mechanical force but by a thermodynamic tendency by which the system as a whole (water plus ice) gains entropy. In principle, one could build a "frost engine" which could produce a heaving pressure of a megapascal per degree of supercooling. Similarly one might make a "helium frost engine" operating near 0 K and a "metal frost engine" operating at blast-furnace temperatures. One could also purify solutions (separate solvents from solutes) without distillation. (In Physical Review E, September 1997; figures at Physics News Graphics.)