the Anode in Vacuum-Tubes. 



191 



These potential differences were measured by means of a 

 Braun electrometer. The asterisks and other signs following 

 some of these quantities denote the type of discharge occur- 

 ring in the tube. With high pressures there appears on the 

 anode, the anode glow which is succeeded by a dark space 

 and the faintly luminous positive column. In this case no 

 distinguishing sign follows the values of V. Then as either 

 the current increases or the pressure decreases, the positive 

 column contracts towards the anode till only the surface of 

 the anode is illuminated. This condition is denoted by the 

 asterisk *. Then as the pressure decreases further, the 

 anode glow disappears, and except for the negative glow, no 

 luminosity appears in the tube. This condition occurred 

 only once — with a current of 0*002 amp., and a pressure of 

 0*35 mm. As the vacuum becomes more perfect, there 

 appears a hazy luminosity throughout the tube, without any 

 glow on the anode. This condition is denoted by the sign j. 

 Finally, the luminosity in the tube increases in brightness, 

 and there is cast behind the anode a shadow, which becomes 

 more definite as the pressure is reduced. The sign § marks 

 this sta^e. 



Tables III. and IV. give other results for the energy 

 (MO) given to the anode per second for constant current 

 0'003 amp. at various pressures. 



Table III. 



Table IV. 



Pressure 



M0 



1 



Pressure | M # 



(mm. Hg). 



(UP 4 erg). 



(mm. Hg). 



(10- 4 erg). 



1-75 



175 



4-80 



130 



1-75 



186 



3-36 



106 



1-48 



183 



2 85 



110 



1-25 



175 



2-52 



120 



1-00 



167 



219 



113 



094 



159 



1-80 



129 



0-94 



157 



1-62 



134 



0-73 



146 



1-40 



177 



0-62 



129 



1-27 



159 



0-41 



86 



11 5 



174 



0-26 



26 



103 



163 



0-16 



202 



0-92 



167 







0-85 



160 





0-67 



143 





046 



85 





0-32 



25 





24 



34 





20 



57 





045 



107 



