LONDON. Physical Society, April n.—Mr. F. E. Smith in the chair.—C. R. Darling and R. H. Rinaldi: The thermo-electric properties of bismuth alloys, with special reference to the effect of fusion. With a note on thermo-electric inversion. A number of different alloys of bismuth with lead and tin respectively were prepared, some of which expanded on freezing, whilst others contracted. The E.M.F. given by these alloys against copper was observed up to 400° C. or over, and it was found that (i) the change in E.M.F. due to the addition of increasing portions of either lead or tin to bismuth reached a maximum value for certain compositions; and (2) that the alloys which expanded appreciably on freezing showed a change in thermo-electric power at the freezing point. The methods employed were not sufficiently sensitive to decide whether the point of disappearance of the thermo-electric change was reached in the case of alloys which were unaltered in volume on freezing. One of the alloys (60 bismuth, 40 tin), when coupled with iron, shows the unusual phenomenon of thermoelectric re-inversion. With a cold junction at o°, this couple shows a zero E.M.F. at o°, 200°, and again at 350°.—J. J. Manley: (i) Preliminary measurement of a primary gas-grown skin. An electrical method for detaching a gas-grown skin from a glass surface is described. Determined in this way, the massiveness of the skin per unit area is much larger than is generally supposed. (2) Removal of gas-grown skins from a Sprengel pump. The pump possesses two vacuum tubes which are interposed between the cistern and the fall-tube. The vacuum tubes have external electrodes. When the pump is in use the electrodes are activated; and the mercury, in falling through the glow discharges, is largely freed from condensed and adsorbed gases.—W. N. Bond: Sub-harmonics produced by a tuning-fork. An extension of experiments described in NATURE of March 8, p. 355.