10 



BELL SYSTEM TECHNICAL JOURNAL 



which would otherwise tend to break the glass and copper away from 

 each other. Successful disc seals have been made with copper up to 

 1-10" thick. There is, of course, a certain maximum thickness that 

 can be used for a seal of a given diameter and it is preferable to keep 

 well below this limit. 



The seals shown in Fig. 4 close the ends of glass tubes to the other 

 ends of which are sealed pilot lamps for the purpose of testing the 

 vacuum. Tubes sealed in this way have been kept a number of 

 years without any impairment of the vacuum. 



B 



C 



^ '\\ INCHES 2 



ffilllll.lllllllllll.llllllllll 



O 3 



ililiUliiilili 



Fig. 5 



N.yC.AjiiP/'cl V.6. ^ 



iiiLiJiiilih 



iiJiirli 



[iili!.l.i,lrii! 



The third type of seal and the most important in connection with 

 the present problem is the tube seal shown in Fig. 5. This furnishes 

 the means of joining metal and glass tubes end to end and is used in 

 the water-cooled tube to attach the anode to the glass cylinder which 



