OF ELECTROLYTES — MCKITTRICK. 385 



the experiments, except where the narrow strips of the electrodes 

 projected upwards, the box was kept covered. 



With this cell (1) it was the same liquid, whose resistance was 

 measured whether the platinum or zinc electrodes were used, and 

 (2) the tube being in the centre of a large mass of liquid, that 

 liquid being approximately at the temperature of the laboratory, 

 and the time intervening between two measurements, one by 

 platinum the other by zinc electrodes, being small, any change 

 in the resistance due to change in temperature might be 

 neglected. 



The box of resistance coils used was a small one. The coils 

 were arranged so as to form three arms of a Wheatstone's Bridge, 

 Two of them contained two coils each, 10 and 100 Siemens units 

 respectively. The third contained a number of coils ranging 

 from 500 to 1 Siemens units, together with a rheochord for 

 measuring fractions of a unit. The coils had been accurately 

 calibrated in Legal Ohms by White, of Glasgow. 



The Galvanometer used was a " dead beat " one of Lord 

 Kelvin's, having a resistance of 400 ohms. The mirror, with 

 magnets attached, weighed 0.035 grms. 



For making and breaking contact I used a " rocker," like that 

 described by Ewing and MacGregor in the paper referred to 

 above. It was so designed that the battery wire was joined up 

 a small fraction of a second before that of the Galvanometer. 



I found, that I was unable with any certainty to detect the 

 vanishing of the hesitation. To my eye it did not seem to 

 vanish even when the adjustment of the arms indicated less than 

 the actual resistance of the cell. The motions of the magnet cer- 

 tainly became quicker then, but none the less did I think I could 

 detect a hesitation. Nor is this other than we would expect. 

 The current must always act for a certain time before any 

 appreciable motion of the mirror occurs. The length of 

 this time wnll vary with the strength of the current. With 

 a weak current the magnet always starts slowly, while with 

 a strong current it may seem to start almost instantaneously. 

 With a certain current and a certain resistance of our cell, there 

 will be a particular hesitation corresponding to the adjust- 



