174 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



iO 



20 30 40 30 60 70 80 90 100 

 Spacirvq Cm. 



Fig. 4 



Rain 

 (0.2"perMin) 



fnsulaior Spark-over 



I0"(25 Cm) Diameter Suspension 



Insulators in Strings 

 Sine Wave -60 Cycle -Effective 



Points o = Both Sides Insulated 

 x= One Side 'Grounded 



I 3 5 7 9 II IS 15 17 19 21 23 

 No. of Discs ir) String. 



Fig. 5 



