A STUDY OF TELEPHONE LINE INSULATORS 



703 



Still another way of increasing the length of path is the use of corru- 

 gations (Fig. 6, for example). The data at hand while not conclusive, 

 indicate that corrugations are of questionable value. 



The third dimension of the conducting path, namely its thickness, 

 can be controlled to some extent by insulator design. The thickness 

 of the water film is determined by the rate of rainfall and by a balance 



Fig. 5 — Experimental design with long skirt. 



between the forces tending to make the film adhere to the surfaces and 

 the force of gravity tending to pull the water away. 



To reduce the amount of water intercepted by the insulator for a 

 given rate of rainfall, it is again advantageous to make the insulator 

 diameter as small as possible. 



To facilitate the running off of the water intercepted, the surfaces 

 in the conducting path should be nearly vertical and smooth. These 

 remarks apply mainly to the outside surfaces. 



