UNTIL about 1930 there was some doubt as to whether liquid metals showed Hall effects. In 1914, Fenninger failed to find Hall voltages in liquid Hg, but he also found a zero effect in solid Hg and the latter result has been contradicted in at least two subsequent experiments. In 1931, Kikoin and Fakidow showed that a liquid Na-K alloy possessed a Hall coefficient approximately equal to the free electron value of—1/nec, wherenis the number of conduction electrons per unit volume. Nevertheless they too concluded that liquid Hg has zero Hall effect. Taken in conjunction with later results for solid Hg (e.g. those of Serduke and Fisher 1932), this would mean that the Hall coefficient,R, changes considerably on melting. It seemed desirable to check this result in the course of developing apparatus for investigating the Hall coefficient of liquid metals generally.