190 Profs. Richardson and Cooke on the Heat developed 



found that an arc or spark discharge took place which melted 

 the grid. The melting took place inside the brass support 

 carrying the filament. This may perhaps be regarded as an 

 argument in favour of the first view. It is, however, impos- 

 sible to settle the question until further experiments have 

 been made ; so far we have contented ourselves with being 

 careful to employ only potentials below the critical point in 

 order to insure the absence of complications arising from 

 this cause. 



§ 8. Grid saturated with O.n/gen. 



The results of all the experiments made with the grid of 

 platinum strip after saturation with oxygen by electrolysis 

 in nitric acid are exhibited in the following table : — 



o a 

 h 8 



a! 



S 5 



- — 



Time electro- 

 lysed since last 

 experiment. 



u G 

 © o 



= s 



- * 



m A 



¥ ~ 



to 



> 

 ft 



5 



u 



JdX 



Saturation cur- 

 rent XlO 5 . 



Uncorrected 

 value (volts). 



o . 



p 9 



a a 



"m ° 

 to 

 0} 



-u o 



Jl s_^ 



"c/3 



o <» 



fa, 



el 



H3 . 



° 2 



!• 



If bra. 



60 ! -02 3-32 



17-1 M> 745 

 1/1 (2;13-3 



684 



8-2 



12-4 



•21 



636 



2. 



20hrs. 



30 W 01 

 ™ (2) -002 



312 



17-0 



(1)10-77 

 (2)21-24 



586 



1004 

 (14°C.) 



14-2 



•24 



5-35 



3. 



12 hrs. 



on (1) -013 



w (2) -004 



3-56 



17-1 



(1) 8-92 



613 





14-3 



•24 



5-62 



4. 

 5. 



6 



not touched 



since last 

 experiment. 



30 (1) -008 2-00 



166 



(i) rn 



(2) 12-1 



607 





13-2 



•22 



5-58 



7} hrs. 



30 3-06 



i 



164 



(1) 5-8 



5-99 



9-67 

 (22°0.) 



13-4 



•22 



5-50 



34 hrs. 



30 j -006 ; 317 



1 1 



16-5 < 1} 10 ' 43 

 lb0 |(2)16-85 



5-99 





14-2 



•23 



5-49 



In the second column are given the times during which the 

 oxygen was being deposited by electrolysis. The electrolytic 

 currents used were always of the order of *1 ampere. The 

 third column gives the interval of time during which the 

 thermionic current was turned on or turned off. In the 

 fourth and subsequent columns, where the numbers are pre- 

 ceded by the figures 1 or 2 respectively in brackets, (1) 

 denotes that the value in question was that at the beginning 

 of the observations, whereas (2) denotes the value at the end 

 of the observations. The fifth column gives the fall of poten- 

 tial alono- the osmium filament due to the heating current. 



