156 Prof. E. Rutherford on Uranium Radiation and 



In consequence of this action, for small electromotive forces 

 the rates of leak are different for positive and negative. 



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Results of this kind are shown more clearly in fig. 14, which 

 gives the current-electromotive-force curves for hydrogen 

 and carbonic acid for small voltages. When there is no 

 external electromotive force acting, the current has a fixed 

 value ; if the uranium is charged positively, the current 

 increases slowly with the voltage ; when the uranium is 

 charged negatively, the current is at first reversed, becomes 

 zero, and rapidly increases with the voltage until for about 

 1 volt between the plates the positive and negative currents 

 are nearly equal. The curve for carbonic acid with a positive 

 charge on the uranium is also shown. It will be seen that 

 the initial slope of the curve is greater for carbonic acid than 

 for hydrogen. 



It is remarkable that the current with zero E.M.F. for 

 hydrogen is about two-thirds of its value when 216 volts are 

 acting between the plates. The ions in hydrogen diffuse more 

 rapidly than in air, and in consequence a large proportion 



