194 



THE ELECTRIC TELEGRAPH. 



serve only to support it, without resisting any horizontal 



strain. 



Siemens and Halske's stretching insulator is made with a 



stronger and larger cast-iron 

 bell than the ordinary one. The 

 porcelain boss or cup carries a 

 stalk with two notches (Fig. 

 105), through which the wire is 

 drawn and wedged on each side, 

 leaving a loop between them. In 

 cold weather, when the line con- 

 tracts, this loop allows the wire 

 between the posts to be slack- 

 ened, and also, in case of a 

 rupture, gives sufficient spare for 

 making a joint. 



Kohl's stretching insulator 

 is shown in Fig. 106. It is 



cemented upon the vertical bar or stalk a in its centre, and 



is turnable in the supporting bracket b, b', with the aid of a 



ig. 106. Fig. 107. 



lever, /. The top of the porcelain bell is cut out in a deep 

 groove, into which the line wire is placed and then bound up 

 tightly by turning the lever. This insulator finds employ- 

 ment principally in Germany. 



