282 



Dr. G. Gore. Relations of Heat to Voltaic and 



effect upon reversal point by gradually heating the liquid). This 

 difference of effect during a rising and falling of temperature is 

 probably due to some hindrance to change of molecular movements 

 analogous to that of supersaturation of a liquid by a salt. 



A series of experiments were made to determine whether the 

 difference in potential, caused in a voltaic ce.ll by rise of temperature, 

 is usually completely accounted for by the electromotive forces pro- 

 duced by the same rise of temperature of the same metals separately 

 in the same liquids. The electric potentials in Table XVIII of the 

 voltaic elements (A) at 60 F. (B) and 160 F. (C) were separately 

 ascertained by means of the thermo- piles (p. 257) ; and those of the 

 separate metals in the form of thermo-elements (D and B) as pro- 

 duced by a difference of from 60 to 160 F. were also separately 

 determined in the same manner, and by the aid of the bent tube 

 apparatus, &c. (see pp. 251 and 257). The liquids employed were of 

 the same quality and strength as those mentioned on p. 252. The 

 following table exhibits the results. The arrows represent the direc- 

 tion of the current at the heated junction : 



Table XVIII. 



Remarks. These results show a considerable percentage of exc 

 in four and a small one of deficiency in two of the cases ; and indi- 

 cate that the difference of potential produced in a voltaic cell by rise 

 of temperature is not in all cases equal to the sum of the potentii 

 produced by heating the two metals separately. 



