﻿274 



Mr. S. Skinner on the Clark Cell 



Cells. 



N4-B+C 



L+B4-C 



N+L+C 



C 



July 20th. 



16°& 



July 23rd. 

 18°. 



July 24 th. 



17°-8. 



After. 



Before. 





13-20 



12-8 



131 



11-69 



10-8 



1105 



1104 



107 



10-9 



093 



093 





July 25th. 

 17°'8. 



Before. 

 1325 

 1115 

 1098 



After. 

 13-11 

 11-10 

 1090 



From which are calculated the following values of resistance 



4-30 



3-S8 



3-96 



5-81 



5-88 



601 



6-46 



5-99 



6-16 



3-97 

 6-07 

 6-25 



3-98 

 5-99 

 6-19 



The temperatures are those of the water-bath in which the 

 cells stood ; the cells were not moved during the whole of 

 the measurements. It will be noticed that the resistance of 

 the cells is lower at high than at low temperature. This 

 agrees w 7 ith the fact that electrolytes decrease in resistance 

 with increase of temperature. 



§ 5. The Resistances, and Apparatus for Comparison of 

 Electromotive Forces. 



The compensating apparatus was the same as that de- 

 scribed in § 8 of the paper by Mr. Glazebrook and the author 

 already quoted. However, in the place of the Leclanche 

 cells there described to produce the main current, I used 

 one or two large Clark cells. The reason for this change 

 arose from the irregular behaviour of the Leclanche cells, 

 when changes were made in the amount of current taken from 

 them. The results of eleven series of observations were 

 rendered useless on this account. When only one Clark was 

 used in the main circuit, the standard cell for reference was 

 a Helmholtz mercurous-chloride cell, § 7. When two Clark 

 cells were used, the standard was some other Clark cell which 

 was kept at rest. 



The circuits, through which the currents from the cells 

 under test were taken, consisted of thick wire coils from a 

 legal ohm resistance-box for the values 1000, 500, 200 legal 

 ohms, and of a german- silver wire of 147 legal ohms wound 

 on an ebonite frame, which was placed in a tank of paraffin 

 oil. This german-silver wire was always used when the 

 current was maintained for any length of time, as from its 

 construction its temperature could be very accurately observed. 



