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OBSEEVATIONS OF ATMOSPHEEIC ELECTEICITY 



AT CAPE TOWN. 



By W. H. Logeman, B.A. 



(Communicated by Professor Beattie.) 

 (Eead August 27, 1902.) 



Observations were taken at the suggestion of Dr. Beattie on the 

 ■sheltered space behind the piUars of the Physical Laboratory of the 

 South African College, Cape Town. An aluminium leaf electroscope, 

 of the form originally used by Messrs. Elster and Geitel,* was con- 

 nected with a distributor similar to that used by them. This consists 

 of a small metal cylinder, about 2 inches in diameter and 4 inches 

 long, connected with the leaves, and taking the place of the plate of 

 an ordinary electroscope. This is surrounded by a large hollow 

 metal cylinder about 7 inches in diameter and 5^ inches long, open 

 at the bottom, but closed at the top with a lid, and connected with 

 the case of the instrument, and thus to earth. The observations 

 were taken as follows : — 



The instrument was charged positively and allowed to stand for 

 about five minutes, then it was recharged if it had leaked at all, 

 and placed outside, and the reading and time was noted. Fifteen 

 minutes later the reading was again noted. The instrument was 

 then charged negatively and allowed to stand for five minutes, and 

 the above process was then repeated with the negative charge. 



When two sets of readings were taken on one day, the first set 

 was taken as above, and the second set was taken in the reverse 



* See Elster and Geitel, " Ueber die Existenz electrischer lonen in der 

 Atmosphare," vol. iv., No. 4, of " Terrestrial Magnetism and Atmospheric 

 Electricity," published by the Johns Hopkins Press. 



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