from Long Vacuum Tubes. 741 



that someone will be able to show that . they have been 

 obtained under other conditions. 



The wave-lengths are given in the following table, referred 

 to International iron standards (Bulletin of Bureau of Stan- 

 dards) : — 



4139-60 faint. 



—41-95 faint. 



—42-34 1 not "] 

 le at ..-, ~ n J resolved. 



jroup. ~^ oU I strong 



— 42-97 ^isolated 



-43-50 j gr ° Up - 



—44-30 J 



-46 CO 



— 19-40 



—5107 



-52-63 



— 53 00 



—54-70 



— 55 65 



—56-55 Hyd. 2nd. Spect. 



-57-15 



— 57 '73 



—58-75 . 



—59-40 



—59-85 



The white stage is undoubtedly associated with the com- 

 plete or nearly complete removal of adsorbed water-vapour 

 from the glass. The X group of lines disappears as soon as 

 the slightest trace of water-vapour is liberated from the 

 glass, which always happens sooner or later with continued 

 operation of the tube. When operated in the extreme white 

 stage, which is marked by the reduction of H a to a brick-red 

 colour of very low luminosity, the tube is rapidly darkened, 

 especially at the angles, by a reduction of silicon on the 

 walls, the bulbs blown for the emergence of the light 

 becoming quite opaque after a time. On this account it is 

 a good plan to have the bulbs on short extensions (2 cms.) 

 of the u end-on " tube, bringing the current in through side 

 tubes ; this keeps the windows clean. 



If a condenser, consisting of three or four medium-sized 

 leyden-jars is placed in parallel with the circuit, when the 

 tube is in the white stage, the X group is weakened or dis- 

 appears entirely from the spectrum and the lines of silicon 



4108-00 



412203 



-08-96 



—22-68 



—10 65 



-11-3 



—12-4 



—23-07 

 __ 9 Isolat 

 "° -° middl 

 —'.7-86 



—12-8 



—28-07 



— 13 - 5 hazy. 



—28-86 



—1408 



—29-74 



—14-46 



-30-49 



— i5-4<n 



—31-03 faint. 



— 15-75 )■ 



—31-25 



—16-22 j 



—31-88 



—17-46 



—32-60 



—17-83 



—32-89 



—19 07 



—33-88 



—19-46 



-34-18 



—19 62 



—34-90 



—20-21 



—35-57 



—20-58 



—36-40 faint. 



—21-36 



—37-53 



