OF ARTS AND SCIENCES, 189 



XI. 



ON THE VARIATIONS OF THE "HALL EFFECT" IN 



SEVERAL METALS WITH CHANGES OF 



TEMPERATURE. 



By Albert L. Clough and Edwin H. Hall. 



Presented April 12, 1893. 



The variation of the so called " Hall effect " with change of tempera- 

 ture in the magnetic metals has long been known. In 1885 the 

 following estimate was given : — 



" A fall of 1° C. in temperature causes in the R. P. [rotational 

 power] of Iron a fall of § ^ approx. 



Steel, soft, " ^ " 



" tempered, " 

 Cobalt « 



Nickel « 



Non-magnetic metals, apparently a small increase." * 



The evidence in favor of an increase with fall of temperature in 

 non-magnetic metals was very slight. 



Leduc t has more recently studied the temperature change in 

 bismuth. 



The Hall effect shows itself in the form of an electromotive force, 

 brought about by magnetic action, at ri^ht angles with the lines of flow 

 of an electric current. It is evident that under such conditions the 

 equipotential lines are no longer at right angles with the lines of flow, 

 as they are when the magnetic force is not operating. This fact 

 gives rise to the terms " rotational power" and "rotational coefficient," 

 which have been used in describing the phenomena under discussion. 

 These terms are somewhat ambiguous, for the reason that they may 

 with as much propriety be used in connection with the rotation of 

 the plane of polarization of light. 



« E. H. Hall, Amer. Journ. of Sci., February, 1885, p. 133. 

 t La Lumiere Electrique, Vol. XXIX., 1888. 



