554 Mr. G. 0. Simpson on the Electrical 



sides of the bath by means of a cathetometer. The readings 

 thus obtained, together with the known coefficients of ex- 

 pansion of glass and mercury, furnish the requisite data for 

 determining the amount of metal volatilized. A partial 

 series of the results obtained is given in Table II., together 

 with the results calculated from the observed tensions of 

 mercury- vapour as given by Regnault and Hertz ; a more 

 complete set of readings will be published later. 



In conclusion I desire to express my thanks to Professor 

 Michelson for the encouragement and helpful criticism given 

 throughout the work, and also to Dr. Gale for the assistance 

 so kindly rendered in the work on the density of mercury- 

 vapour. 



Kyerson Physical Laboratory, 

 March 25, 1902. 



LXII. On the Electrical Resistance of Bismuth to Alternating 

 Currents in a Magnetic Field. By George C. Simpson, 

 B.Sc, Fellow of the Victoria University*. 



IN a previous paper (Phil. Mag. 1901, ii. p. 300) I described 

 experiments which showed that the anomalous effect 

 produced in a bismuth wire carrying an alternating current 

 placed perpendicular to a strong magnetic field can be con- 

 veniently represented by an E.M.F. (called the " bismuth 

 E.M.F/') set up in the bismuth itself. It was then found 

 that this bismuth E.M.F. varies in phase and magnitude with 

 different frequencies of alternating current used — the phase 

 being 100° 13' behind the applied E.M.F. with a frequency 

 of 3 per second, the lag increasing to 126° 31' with a fre- 

 quency of 60 per sec. ; the magnitude being a linear function 

 of the frequency and increasing with it. 



This investigation having given the variations of the 

 bismuth E.M.F. with frequency, the field being kept con- 

 stant, experiments have since been made to find how the 

 bismuth E.M.F. varies with the field-strength for a given 

 frequency. The investigation again consisted of two parts — 

 determinations of the changes in the angle of lag and in the 

 magnitude. 



I. The determination of the variation of the angle of lag until 

 different field-strengths, the f eguency being constant, was made 

 by the same method as that already used and described in 

 the previous paper. The experiments were now more difficult 

 owing to the diminution of the whole effect due to decreasing 



* Communicated b}' the Author. 



