FABABAY'S CONCEPTION OF ELECTRICITY. 245 



positive electrode the equivalent quantity of oxygen, one atom of 

 oxygen for every pair of atoms of hydrogen. If, instead of hydrogen, 

 any other element capable of substituting hydrogen is separated from 

 the electrolyte, this is done also in a quantity exactly equivalent to 

 the quantity of hydrogen which would have been evolved by the 

 same electric current. 



Since that time our experimental methods and our knowledge of 

 the laws of electrical phenomena have made enormous progress, and a 

 great many obstacles have now been removed which entangled every 

 one of Faraday's steps, and obliged him to fight with the confused 

 ideas and ill-applied theoretical conceptions of some of his contempo- 

 raries. We need not hesitate to say that, the more experimental 

 methods were refined, the more the exactness and generality of Fara- 

 day's law was confirmed. 



In the beginning, Berzelius and the adherents of Volta's original 

 theory of galvanism, based on the effects of metallic contact, raised 

 many objections against Faraday's law. By the combination of No- 

 bili's astatic pairs of magnetic needles with Schweigger's multiplicator, 

 a coil of copper wire with numerous circumvolutions, galvanometers 

 became so delicate that the electro-chemical equivalent of the smaller 

 currents they indicated was imperceptible for all chemical methods. 

 With the newest galvanometers you can very well observe currents 

 which would want to last a century before decomposing one milligramme 

 of water, the smallest quantity which is usually weighed on chemical 

 balances. You see that, if such a current lasts only some seconds or 

 some minutes, there is not the slightest hope to discover its products 

 of decomposition by chemical analysis. And, even if it should last a 

 long time, the feeble quantities of hydrogen collected at the negative 

 electrode can vanish, because they combine with the traces of atmos- 

 pheric oxygen absorbed by the liquid. Under such conditions a feeble 

 current may continue as long as you like without producing any visible 

 trace of electrolysis, even not of galvanic polarization, the appearance 

 of which can be used as an indication of previous electrolysis. Gal- 

 vanic polarization, as you know, is an altered state of the metallic 

 plates which have been used as electrodes during the decomposition of 

 an electrolyte. Polarized electrodes, when connected by a galvanom- 

 eter, give a current which they did not give before being polarized. 

 By this current the plates are discharged again and returned to their 

 original state of equality. 



This depolarizing current is indeed a most delicate means of dis- 

 covering previous decomposition. I have really ascertained that un- 

 der favorable conditions one can observe the polarization produced 

 during some seconds by a current which decomposes one milligramme 

 of water in a century. 



Products of decomposition can not appear at the electrodes without 

 motions of the constituent molecules of the electrolyte throughout the 



