1887.] Rate at which Electricity leaks through Liquids. 413 



meter (White's form) was used to show the fall of potential as the 

 charge leaked through the faulty insulating liquids. 



To facilitate changes of connexion between the condenser, the 

 electrometer, and the cells, a paraffin block, with holes bored through 

 it and filled with clean mercury, was used. The whole arrangement 

 of apparatus was as shown in fig. 2. 



In testing the arrangement the condenser was used as an air-con- 

 denser, and it was found that there were signs of some electrical 

 absorption. These were traced to the paraffin key and the wire con- 

 necting it with the electrometer. The key was improved by the use 

 of very clean mercury, and very careful amalgamation of the ends of 

 the copper wire dipping into the mercury cups. The wire at first 

 used to connect the cup A in the key with the electrometer was 

 covered with gutta-percha, and the whole passed through lead pipe, 

 put to earth to protect it electrically from the experimenter. But it 

 was found that there was absorption on charging and the appearance 

 of residual charge on discharging the electrometer ; the gutta-percha- 

 covered wire was therefore discarded, and bare wire stretched between 

 insulating points, and this was then protected electrically by a shield 

 of zinc, enclosing it and put to earth. 



In testing, the condenser was connected with the electrometer by 

 laying a piece of wire, so as to connect the cups C and A. A second 

 piece of wire carefully insulated in a bar of paraffin which was attached 

 to a metal handle was then used to connect the cells by the cup B to 



