Current of Electricity from a hot Platinum Wire, etc. 505 



galvanometer was therefore employed to measure the discharge 

 from the wire. The instrument used was of the D'Arsonval type 

 giving 1 division for 8 x 10 -9 amperes. 



The method of experimenting now was to subject the dis- 

 charge to a known magnetic field and note the current passing 

 through the galvanometer. The magnetic field was then cut off 

 and the current again measured. Thus the two observations 

 could be made within a few seconds of one another. The follow- 

 ing results given in Table V. were obtained on October 26, with 

 wire I. This wire, during the experiments on previous days, had 

 been kept glowing for many hours. This is to be noted as it has 

 a bearing upon the result. 



At the commencement of a set of observations the apparatus 

 was pumped to as low a pressure as possible. The pressure was 

 again measured at the end of the set. The pressures given in 

 the table are therefore the highest during the series of 

 observations. 



Table V. (Wire I.). 



Air was now let into the apparatus up to atmospheric pressure. 

 After this treatment the discharge in a vacuum was found to 

 be much smaller than before. At a temperature of 1120° C. all 

 the discharge was stopped by a magnetic field of 300 lines. The 

 value of the current in this case was 5'2 x 10 -7 amperes. 



The results given in the above table show that the discharge 

 from a wire which has been subjected to prolonged heating con- 

 sists almost wholly of corpuscles. It is to be noted also that the 



