480 Dr. G. Gore. Thermo-Electric Behaviour of [Dec. 11, 



Remarks. — Many of the remarks which I have made in a previous 

 paper on the thermo-electric properties of liquids (Proc. Roy. Soc, 

 vol. xxvii, pp. 535-538) respecting the cause of the currents, apply 

 to the results obtained in the present research ; and I consider that 

 the causes of the currents and of their direction are similar in the two 

 cases. 



On examining the results it will be observed that the effects are not 

 manifestly related to the chemical nature of the solutions ; thus, the 

 liquids in which hot mercury is positive include those of acid, as well 

 as those of alkaline reaction ; and similarly with the solutions in which 

 cold mercury is positive. To what extent chemical action occurred in 

 the experiments and operated as a cause of electric currents, would 

 be a difficult point to completely prove, because the amount required 

 to produce such feeble currents would be so extremely small ; the 

 result of a general examination of the phenomena, however, does not 

 support the hypothesis that the currents were of chemical origin. 



The evident cause of the currents was heat, and the direction of 

 them was probably due to molecular changes in the liquid attendant 

 upon alteration of temperature. In nearly all cases the magnitude of 

 the current increased with the amount of 1 difference of temperature ; 

 the apparent, but not real, exceptions were those in which a reversal, 

 or an advance towards it, occurred. 



The strength of the solution manifestly affected the quantity, and in 

 some cases the direction of the current, as may be perceived with the 

 solutions of potassic cyanide (Nos. 1, 2, 3, and 4), selenic acid 

 (Nos. 5 and 6), ammonia alum (Nos. 9 and 10), formic acid (Nos. 11 

 and 12), sulphuric acid (Nos. 15, 16, and 17), and phosphate of 

 sodium and ammonium (Nos. 33 and 34). If the cause of the cur- 

 rent, in the case of sulphuric acid, was chemical action, the direction 

 of the current would probably not have been reversed by mere altera- 

 tion of temperature, ^or by variation of strength of the mixture. If, 

 also, the cause of the currents in general was of a chemical nature, 

 the currents would probably have been much stronger, especially with 

 the stronger solutions, and would have increased in all cases, with the 

 strength of the solution, until the latter was much more concentrated 

 than those which were employed. 



Stirring either portion of the liquid influenced the deflection in 

 59 cases out of 72, increased it in 49, and decreased it in 10 of those 

 cases. Stirring the cold portion altered the current in 31 cases out of 

 36, and stirring the hot portion changed it in 28 cases out of 36. 

 Stirring the cold portion also had a greater average magnitude of effect 

 upon the current than stirring the hot portion. Stirring a liquid of 

 acid reaction increased the current in 13 cases out of 20, decreased or 

 reversed it in 3 cases, and had no effect in 4 cases. Stirring an 

 alkaline one increased the deflection in 12 cases out of 24, decreased it 



