RECENT PROGRESS IN PHYSICS. 



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ritb the conductor, and thus made inductive, there appeared with a 

 lositive conductor — ■ 



parks alone up to an interval of 0.49 in. 



^legative brush, from the small ball alone, when the inter- 

 val was greater than ,. 0.52 '• 



"With a negative conductor — 



Iparks alone up to an interval of 1.15 " 



Positive brush, from the small ball alone, when the interval 



I was greater than 1.G5 •" 



I Between these limits he obtained sparks and brushes mixed. 

 * The balls were then exchanged, the small ball being connected with 

 jhe conductor, and the large one uninsulated. The result with a 

 ijositive conductor was — 



Sparks alone to an interval of. 0.4 in. 



f^egative brush alone, when the interval was greater than.. 0.44 " 

 i From these experiments it follows that — 



! 1. Longer sparks are obtained when tlie small ball is positively 

 [ilectrified. 



I 2. Longer sparks are obtained when the large ball is the inducing, 

 Lnd the small one th" inducteous ball. 



! When the small ball discharges electricity in the form of brushes, 

 Ihey are much more numerous, and each one seems to carry ofi'.much 

 less electrical force when the discharged electricity is negative than 

 pirhen positive. 



I This appears to indicate that a small ball requires a greater tension 

 for discharging when positive than when negative. 

 \ To illustrate this important point, Faraday arranged an apparatus, 

 hpresented in fig. 73. A fork. A, carrying a large and a Fi?. 73. 

 f^mall ball, was connected with the conductor of a machine ; 

 ft perfectly similar fork, B, was connected with a discharg- 

 ing train ; the small ball on each fork was placed opposite 

 Lihe larger one on the other. The intervals at n and were 

 ?qual. The conductor being negative, the discharge al- 

 [ways happened at n, which is not surprising, because the 

 liegative charge of the small inducing ball at n is always 

 Wronger than the positive charge of the small inductions 

 iball at 0. But had the discharge taken place at o with a 

 Ijositive cl large of the conductor, it would have appeared 

 [that the weak negative charge of the small inducteous 

 Iball discharges with greater facility than the far stronger 

 positive charge of the small inducing ball at n, which 

 jwould have been a decisive proof of the more facile dis- 

 icharge of negative electricity. But such a decisive result 

 jthe experiments did not give ; when the intervals at n and 

 :0 were 0,9 of an inch, or 0.6, the discharge always took 

 place at n, whether the conductor was positive or negative. 



The interval n being made 0.79 and 0.58 of an inch, if the con- 

 ductor was positive, the discharge at both w and was about equal, 

 }jUt if negative, the discharges mostly happened at n, which signified, 



