386 TENTH ANNUAL REPORT OP 



= 20 — 2 =: 18. 



— 34 _ 6 = 28. 



= 41 — 11 = 30. 



^o_^ _ JA^ = 43 — 15 = 28. 



40 — 21 = 19, 



34 _ 24 rr: 10. 



Thus, in fact, the maximum effect is changed from the fourth to 

 the third comhination. 



We see, from these results, that among the ratios here considered, 

 the diminution of strength of current, hy polarization, is less for 

 those comhinations for which the entire resistance is greater, and 

 therefore the change of maximum, in the way indicated, is explained. 



We have supposed here that the amount of polarization is constant ; 

 hut this is not the case, as we shall see suhsequently. The final result 

 of this consideration, however, will not he changed essentially in 

 consequence of this. 



§ 33.* Bimimdion of the resistance of liquids hj heat. — While the 

 resistance of metals is increased by heat, that of liquids, on the_ other 

 hand, is considerably decreased. The first measurement of this was 

 made by Becquerel, (Annales de Chemie et de Phys., 3 Series, XVII, 

 285.) He used the method above described. One of the vessels, 

 Fig. 26, was heated in a water bath until the temperature became 

 constant. 



At the temperature 14°. 4 Becquerel found the resistance of a column 

 of saturated solution of sulphate of copper, whose height was 3.88, 

 equal to the resistance of a given platinum wire. But at the tem- 

 perature 56° the resistance of the same wire was equal to a liquid 

 column 8.50 in height. 



Since a rise of temperature of 56° — 14°. 4 = 41°. 6 is required to 

 increase the conductive capacity of the saturated solution of sulphate 

 of copper in the ratio of 3.88 to 8.50, a rise of temperature of 35° is 

 necessary to double the conductive capacity of this liquid, provided 

 the changes of conductive capacity are proportional to those of tem- 

 perature. With a rise of temperature of 1° the conductive capacity 

 of this solution will be increased by sh, or 0.0286 of its value at 

 14°. 4. 



In the same manner Becquerel found that for a rise of temperature 

 of 1°, the conductive capacities of the following liquids were increased 

 by the following parts of their original values indicated below : 



