Current of Electricity from a hot Platinum Wire, etc. 507 



that the presence of heavy particles in the discharge is not due 

 to dirt on the wire. On November 27 a fresh wire (Wire III.) 

 was taken and boiled for three hours in pure nitric acid, and 

 finally rinsed in boiling distilled water. In addition to this the 

 wire was kept for thirty minutes at a bright yellow heat in air at 

 atmospheric pressure by means of an electric current. We may 

 reasonably expect this process to remove any dirt that might be 

 on the wire. After this treatment the wire was not touched with 

 anything and was thus placed in position between the electrodes 

 in a clean state. The discharge from this wire was now found 

 to be so small that an electrometer was substituted for the gal- 

 vanometer. Table VII. contains some results obtained with this 

 wire soon after it had been set up. 



Table VII. (Wire III.). December 2nd. 



It will be noticed that the discharge from this wire also con- 

 tains a good percentage of heavy particles. 



The wire was now heated to a high temperature in air at 

 a few millimetres pressure. After some minutes heating fresh 

 air was let in to atmospheric pressure. The operation was then 

 repeated several times. This process gets rid of gases occluded 

 in the wire and it was also found greatly to diminish the dis- 

 charge. The following results were obtained on December 5th 

 with Wire III. after it had been subjected to the above treat- 

 ment. 



