OF ELECTROLYTES — MCKITTRICK. 



389 



measurements as if e had the value zero, would the error be 

 negligible ? 



To test this, I simply made several measurements, first by this 

 method, and then by neutralizing e. I varied both the size a,nd 

 the direction of «, but, in no case, was I able to notice any differ- 

 ence in the two measurements. 



To proceed in this way, however, the Galvanometer must be 

 joined up first. Rigorously this will not give accurate results ; 

 for the principle on which measurement of resistances by Wheat- 

 stone's Bridge rests, requires that the current shall have attained 

 a steady value. Whether, practically, with circuits such I was 

 using, any error would be introduced by this method, could be 

 ■decided only by experiment. To test this, I simply measured the 

 resistance of a solution of zinc sulphate, using amalgamated zinc 

 electrodes, first joining up the battery wire before the Galvano- 

 meter wire, and then vice versa. The experiments that I made 

 perfectly satisfied me, that the error, if there was one at all, was 

 clearly negligible. 



During my experiments the resistance of my cell varied from 

 100 to 10,000 Legal Ohms. The accuracy with which I could 

 determine the resistance is shown in the following table, which 

 ^ves a few average results : — 



