c 



b 



S3 



s_ 



u 



PR 



Properties of some Liquid Metals. 403 



the copper-mercury element with the current direct; and 

 lastly, a reading from this element with the current reversed. 

 The cycle then began again. From the means of each pair 

 of readings, reduced, two curves were plotted, one giving the 

 relation between temperature and time, and the other giving 

 the relation between E.M.F in arbitrary units, and time. 



The curves (fig. 4) give the relation between E.M.F. and 

 temperature deduced from these two curves, for two experi- 

 ments. 



Fig. 4.— Copper-Mercury Thermo-element. 



20 



10 





X 



*~ =S =^ 



=^— J 





■■/■ 





• , ^tttS-O 





/. 







f 



/ 



o 2- st Exp e ri me nt 





/ 





.. eaptnmM 





Jo 







! 



— ^ 



Temperature C. 



In figs. 2, 3, 4 two curves are in each case given. These 

 two curves were obtained from the same metal. The effect 

 is most marked with bismuth (fig. 3). At the conclusion of 

 one experiment the apparatus was cooled very rapidly by 

 removing the sand and blowing air on to the tube containing 

 the melted metal. Another set of readings was then taken, 

 with the temperature of the hot junction rising, and the lower 

 of the two curves in fig. 3 was obtained. At the conclusion 

 of this experiment the apparatus was cooled very slowlv, 

 about two hours being occupied^ and the result of the next 



-80 



