22 



Messrs. Stroud and Henderson on the 



as the battery circuit is broken. Experiment shows that the 

 arrangement shown in the figure is much the better of the two. 



In practice, however, it is found that the polarization in 

 the two cells is not always exactly the same ; generally speak- 

 ing at least 99 per cent, of the polarization may be balanced 

 in this manner, but ordinarily the balance is much more 

 perfect than this. The next point then is to drown the 

 residual differential polarization by working with high re- 

 sistances and high voltages, and in this way the detrimental 

 effects of polarization are reduced to insignificance. With 

 electrolytic cells having a difference in resistance of about 

 20,000 ohms, the remaining arms being 1000 ohms each, and 

 with a D'Arsonval galvanometer of about 300 ohms, when 

 the voltage on the bridge is 30 the measurements are very 

 like measurements of metallic resistances. 



To get the specific resistance immediately in ohms, without 

 reference to any other electrolyte, the cells C and c are con- 

 structed as shown in the figure. 



Each ceU consists of three parts, two being small, thick- 

 walled test-tubes with necks half-way up their sides. Into 

 these necks fit the well-ground ends of a tube of nearly uni- 



Ffc. 2. 



form bore. In the case of the cell C this tube is 30 centim. 

 or more in length, while in the case of c it is only a few 

 centim. long. In every other respect the two cells are as 

 nearly as possible alike. 



The vertical limbs of the H cells were about 1*2 centim. in 

 diameter, and about 6 centim. high, and the horizontal tubes 

 about 0*6 centim. external diameter, the diameter of the 

 bore being chosen to give a convenient resistance with the 



