An instrument for demonstrating the freezing of water by evaporation, invented by W. H. Wollaston.
The cryophorus consists of a short glass tube with a right-angle bend at each end terminating in a bulb. The apparatus is evacuated except for a small amount of water in one of the bulbs. When the empty bulb is immersed in a freezing mixture or a liquefied gas, the resultant cooling causes a drop in pressure and so more evaporation of the water, which soon freezes.
Early 19th century. From cryo- + -phorus.