152 Thermomagnetic Properties of Crystalline Bismuth. 



Table VI. shows that the mean Hall electromotive force is 

 not appreciably influenced 'by the Hall electrodes g and h 

 not lying exactly upon an equipotential line. 



Table VI. 

 Hall Effect. Temperature 16°. 







1st Adjustment. 



2nd Adjustment. 



H. 



3 (amp.). 











E.M.F. 



E. 



E.M.F. ! E. 







+2 



- 61 



v. 



+ 9 Mv. 



+4980 



+2 



-317 



-256 



-228 -237 







+2 



- 61 





+ 9 







—2 



+ 58 





- 12 



+4980 



—2 



+314 



+256 



+230 +241 







—2 



+ 58 





- 11 







+2 . 



- 62 





+ 9 



-4980 



+2 



+199 



+261 



+281 +271 







+2 



- 62 





+ 12 









—2 



+ 52 





- 16 





-4980 



-2 



-193 



-245 



-269 



-253 







—2 



+ 52 





- 16 





Mean = 254 



1 



Mean = 250 



§ 4. Tlie Conductivity for Heat. 



The other properties of the crystal, such as change of 

 resistance, Hall effect, &c, have been determined for the two 

 directions and for different field-strengths, and at several 

 different temperatures. The determination of the conduc- 

 tivity for heat, for the two directions, and its variation with 

 temperature, both in and out of the magnetic field, was not 

 possible, since the general methods for the determination of 

 heat-conductivity are not applicable to so small a specimen 

 as we have to deal with in the present. I have sought, how- 

 ever, by the method due to de Senarmont* to get approximate 

 values of the ratio of the conductivities for the two directions 

 in and out of the magnetic field. The crystal was well cleaned 

 and coated with a thin layer of elaidic acid. This has been 

 recommended by Voigtf in preference to the mixture of 

 wax and turpentine used by de Senarmont. On the centre of 

 the crystal plate was pressed the pointed end of a stout copper 

 wire, 1 metre long, which w T as heated in the middle by means 

 •of a Bunsen burner. The isothermal curves on the plate are 



* De Senarmont, C. It. xxv. pp. 459, 707 (1847). 

 t W. Voigt, Gottingen Nachricht. 1896, Heft iii. 



