292 Mr. H. Tomlinson on the Effect of Magnetization 



we divide the last number by 14 x 10 -6 , the magnetic suscep- 

 tibility, we shall obtain the E.M.F. which would be produced 

 by magnetizing the bismuth to unit intensity ; this is 15714 

 C.Gr.S. units. Now, according to Ewing, the E.M.F. produced 

 in a certain specimen of soft iron wire by a magnetic intensity 

 of 160 C.Gr.S. units was 6 microvolts, when the junctions of 

 the magnetized and unmagnetized wires were at 100° C. and 

 16° C. respectively. Accordingly the E.M.F. produced by unit 

 magnetic intensity would be 3'75 C.G.S. From this it is evi- 

 dent that, for a given intensity of magnetization, bismuth has its 

 thermoelectrical properties altered by longitudinal magnetiza- 

 tion 4000 times as much as iron. We see, then, that the rela- 

 tive changes produced by magnetization in the thermoelectrical 

 properties of bismuth and iron are comparable with the 

 changes wrought in the electrical and thermal conductivities 

 of these metals. 



Grimaldi has already published researches* on the effect of 

 both transverse and longitudinal magnetization on the thermo- 

 electrical properties of bismuth, and finds that magnetization 

 in either of these two directions makes the bismuth of com- 

 merce thermoelectrically negative to unmagnetized bismuth. 

 He also finds that the thermoelectrical E.M.F. of a pure 

 bismuth and copper couple is increased by both longitudinal 

 and transverse magnetization. Now according to Ettings- 

 hausenf, who also quotes Rollmann$,pt<r« bismuth is thermo- 

 electrically negative to copper, whilst commercial bismuth is 

 positive to copper. The following table is taken from 

 Ettingshausen''s memoir: — 



Table III. — Bismuth alloyed with different amounts of Tin. 



Potential difference, in 

 C.G.S. units, for 1° C. , 

 between a bismuth and; dumber of parte, by 

 copper couple with onei ™ lg I».° f ^.n 

 j unction at 20° C. and, b,smllth lu 1C " 

 the other at 0° C. 



-6500 



10000 



+ 280 



9905 



+ 1950 



9854 



+3910 



9386 



+3390 



86-90 



* R, Ace. del Lincei, vol. iii. Also memoir, entitled Influenza del 

 Magnetismo mile Propriety Termoelettriche del Bismuto (Palermo, 1887) : 

 Journal de Physique, Dec. 1887, p. 569. 



f Sitzb. de?- kais. Akad. der Wissensch. 1887. 



% Pogg. Ann. lxxxiii., lxxxiv., lxxxix. 



