30 



Dr. H. J. S. Sand on the Measurement of the 



were spread out over several days. The apparatus was also 

 used for single experiments, the side-tube S and rubber 

 tube E with clips YY being then omitted. 



For the purpose of filling the apparatus as illustrated in 

 fig. 1, both the funnels U and V must be employed, the top 

 being inverted for filling the upper part through the funnel V. 

 A vent-hole with tap (not shown in the figure) allows the air 

 to escape through the bung L. The last air-bubbles are 

 removed from the cathode through the side-tube S. When 

 in use the apparatus was placed on a non- vibrating shelf. 



The electrical arrangements are shown completely in fig. 4. 



Fig 4 



They comprise the main circuit, the condenser-bridge circuit 

 already explained on p. 27, and the potentiometer circuit. 

 The current was derived from a battery of small accumulators 

 A, and was kept perfectly constant by variation within 

 suitable limits of the original electromotive force employed 

 as shown at B, fig. 4. It passed through a known constant 

 resistance C, then through a dial-box, provided for the purpose 

 of introducing when required the resistance M referred to on 

 p. 27. As a rule this box was, however, kept free from re- 

 sistance. After this the current passed through the electrolytic 

 cell E, and finally through a rough resistance F of about the 

 same magnitude as the latter, 



