608 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



Figs. 395 and 396 show how these insulators are arranged on the 

 poles, and how they hold the wires, in the straight parts of the 



FIG. 395. Telegraphic air lines ; suspending posts ; insulators. 



line or at points where sharp turns are made, and special arrange- 

 ments (annular supports) are required. 



FIG. b9G.-Mr.sli room insulators; annular insulator. 



The poles are set up about 60 or 80 yards apart, according to the 

 weight of the suspended wire ; they are placed nearer in curves, and 



