Lloyd — Magnetic Effects in Tellurium. 57 



Art. VI. — The Thermo-magnetic and Galvano-magrietic 

 Effects in Tellurium ; by Morton Githens Lloyd, Ph.D. 



The investigations here described were begun with the idea 

 of measuring all of the thermo-magnetic and galvano-magnetic 

 effects in the same specimen of a non-metal, tellurium being 

 the substance chosen. It has heretofore been investigated for 

 only two of the transversal effects. Satisfactory numerical 

 values of the magnitude of most of these effects have not yet 

 been obtained, owing to the difficulties involved in their meas- 

 urement, but as the work must be interrupted for some time, 

 it is thought best to publish the qualitative results at once. 



If a conducting plate carrying an electric current be placed 

 in a magnetic field perpendicular to the lines of force, the fol- 

 lowing galvano-magnetic effects have been observed. 



1. A difference of electric potential is produced between the 

 edges of the plate, perpendicular to the cfirection of the cur- 

 rent and of the magnetic field. (Hall effect.) 



2. A difference of temperature is produced between the 

 same points. 



3. A change of resistance occurs. (Longitudinal Hall effect.) 



4. A difference of temperature is produced in the direction 

 of the current.* 



If a flow of heat replace the primary electric current, four 

 analogous thermo-magnetic effects are observed. 



1. A difference of electric potential between the edges of 

 the plate. 



2. Rotation of the isothermal lines or a difference of tem- 

 perature between the same points. 



3. A change of conductivity for heat. 



4. A difference of potential in the direction of the heat- 

 flow. (Longitudinal thermo-magnetic effect.) 



The transversal effects are reversed in direction when either 

 the magnetic field, or the primary current of heat or electricity, 

 is reversed in direction ; but the longitudinal effects are inde- 

 pendent of the direction of the field. 



It has already been proposedf to call the galvano-magnetic 

 temperature-difference, the thermo-magnetic temperature-dif- 

 ference, and the thermo-magnetic potential-difference by the 

 respective names, Ettingshausen effect, Leduc effect and Nernst 

 effect. Most of these effects were first observed in bismuth, 

 and some of them only in bismuth. The change of conduc- 



* Nernst, Wied. Ann., xxxi, p. 784, 1887. 



f Thesis: The Transversal Thermo-magnetic Effect in Bismuth, M. G. Lloyd, 

 Philadelphia, 1900; Beiblatter, 24, p. 1014. 



