FIGURES 1 - 25 



TITLE Page 



Fig. 1. Atmospheric-electric cabin at right, showing starboard wall and entrance 21 



Fig. 2. Looking down on roof of atmospheric-electric cabin just forward of the mainmast 21 



Fig. 3. Ion counter DTM No. 1 (ICl) for measurement of small-ion content of the 



atmosphere 21 



Fig. 4. Penetrating radiation apparatus No. 1 (PR 1) for measurement of ionization due to 



cosmic rays and other penetrating radiation 22 



Fig. 5. Ionization apparatus of radioactive-content apparatus No. 4 (RCA4) 22 



Fig. 6. Kolhorster penetrating radiation apparatus No. 5503 in use on quarter-deck for special 



tests 23 



Fig. 7. Conductivity apparatus No. 8A (CA8A), showing vertical air-flow tube and the eye- 

 reading electrometer which was used until September 1929 23 



Fig. 8. Air -flow tubes of ion counter and conductivity apparatus on roof of atmospheric- 

 electric cabin 24 



Fig. 9. Conductivity recording apparatus installed at San Francisco in August 1929 24 



Fig. 10. Potential-gradient apparatus No. 2 (PGA2) with umbrella- shaped conductor, used for 



eye-reading observations until September 16, 1928 24 



Fig. 11. Potential -gradient recording apparatus installed on stern rail to starboard of eye- 

 reading apparatus PGA2. 24 



Fig, 12. View of recording electrometer for potential-gradient, as installed with accessories 



in weatherproof box for mounting on stern rail 25 



Fig. 13. Aitken nuclei counter, used to determine the number of condensation nuclei per cubic 



centimeter in the atmosphere 25 



Fig. 14. W. C. Parkinson operating the Aitken nuclei counter on the bridge 25 



Fig. 15. Potential-gradient reduction-factor station on Watson's Island, Apia, Samoa, April 1929 26 



Fig. 16. View of short vertical collector rod on potential-gradient recording apparatus substi- 

 tuted for bent rod (fig. 11) on November 5, 1928 26 



Fig. 17. Calibrating the potential-gradient recording apparatus, an operation performed once 



each week unless bad weather prevented 26 



Fig. 18. View of potential-gradient recorder and eye-reading apparatus on stern rail of ship 27 



Fig. 19. View of potential-gradient apparatus from quarter-deck with awning up 27 



Fig. 20. View of unifilar electrometer of recording conductivity apparatus CA8A 28 



Fig. 21. View of high resistance ionium cell of recording conductivity apparatus 28 



Fig. 22. Schematic diagram of Gerdien conductivity apparatus with unifilar electrometer, high 



resistance cell, and variable calibrating condenser 29 



Fig. 23. Design of shielding "cup" at intake of ion counter devised to avoid error in ion 



measurements when the 'charging" method of operation is used 29 



Fig.24. Detail drawing of Aitken nuclei counter 30 



Fig. 25. High potential generator for radioactive content apparatus No. 4 shown removed from 



metal housing 30 



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