496 MEASUREMENT OF CAPACITY. DIELECTRICS. 



If c = c, as required by the law in question, it follows that 



that is to say, that when the circuit is broken, the algebraical sum of 

 the electromotive forces should be constant in other words, they 

 should vary by quantities which are equal and of opposite signs ; this 

 is what is shown by experiment if each of the electrodes is connected 

 with the inner coating of two identical condensers united by their 

 external armatures, as shown in 1049. The outer coatings and 

 one of the liquids being connected by a galvanometer, or, still better, 

 by an electrometer, the connection of the short circuit is opened. 

 If the two electrodes are equal, the needle is stationary, which 

 proves that the two armatures experience equal and opposite changes 

 of potential. The needle is deflected as soon as there is an. appre- 

 ciable difference of potential between the surfaces of the two 

 electrodes. 



Let us observe, in passing, that equation (2) would furnish a 

 method of measuring the capacity of polarization c. The voltameter 

 being connected with a battery of less than the maximum electro- 

 motive force, the intensity of the current of polarization / is measured 

 by a galvanometer, and, connection being broken, the loss of electro- 



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motive force is measured by an electrometer. 

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