326 THE EARL OF BERKELEY, MESSRS. E. G. J. HARTLEY AND J. STEPHENSON 



such a change very seldom happened when the proper level of the liquid in the beaker 

 had been found. The first observation, however, of any series was nearly always 

 somewhat different from the subsequent ones ; this was thought to be caused by a 

 slight difference of concentration on the electrode surfaces when first wetted by the 

 solution, and the observation was therefore rejected. 



-Thermometer 



Solution | =*_ . 



Fig. 1. 



Temperature Coefficient. 



As the temperature of the solution was always some seven or eight hundredths of 

 a degree above 0C., a correction was obtained by allowing the temperature to rise 

 slightly and then re-determining the resistance ; by assuming that the change of 

 resistance was proportional to the change of temperature the observed resistance 

 could be extrapolated to C. 



It may be mentioned here that although the level of the solution in the cell could 

 not be seen on account of the mercury jacket (see fig. 1), yet by means of an oil gauge 

 attached to E it was ensured that on filling the cell the level always reached the 

 same height. 



