Fig. 8. Air-flow tubes of ion counter (small tube) 

 and conductivity apparatus (large tube) on roof 

 of atmospheric-electric cabin 



Fig. 9. Conductivity recording apparatus installed 

 at San Francisco in August 1929, and used at 

 sea September through November, 1929 



Fig. 10. Potential-gradient apparatus No. 2 (PGA2) 

 with umbrella- shaped conductor, used for eye- 

 reading observations until September 16, 1928 



Fig. 11. Potential-gradient recording apparatus 

 installed on stern rail to starboard of eye- 

 reading apparatus PGA2. Note form and po- 

 sition of collector rod; this was used from 

 July 7, 1928 to November 5, 1928 



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