IN a recent letter to NATURE (Feb. 16, p. 244) I directed attention to Beilby's observation that water drops become hard when chilled to -12°C., and to the fact that water is quite fluid at -9.3° (White and Twining, Jour. Am. Chem. Soc., 50, pp. 380-389; 1913). That an important change in properties takes place between these temperatures is indicated by the difficulty all experimenters have had in cooling water below -10°. It may be that here the steady expansion which water undergoes below 4° ceases, and that with further lowering of temperature the contraction obtains which was predicted by Bridgman (Proc. Am. Acad., 47, p. 543; 1911–12). Water has been cooled in capillary tubes to -18.5° (T. Borovik-Romanova, rev. in Chem. Abs. Am. chem. Soc., 19, p. 3186; 1925), and as fine drops suspended in oil to -20° (M. L. Dufour, Arch. Sci. Geneva, 10, p. 350; 1861), but no information is given as to the physical state at these temperatures.