644 HENRY A. ROWLAND 



of different sizes with the same number of turns of his machine, and 

 discharging them through a galvanometer, he proved that the sudden 

 deflection of the instrument depended on the quantity, and not the 

 tension, of the electricity. He then arranged a little voltaic hattery out 

 of zinc and platinum wires, so that, when joined to the galvanometer for 

 three seconds, it gave the same swing to the needle as the Leyden jar 

 battery charged with thirty turns of his machine. By this means he 

 was able to estimate that a small battery which decomposed a grain of 

 water, furnished as much electricity as 800,000 discharges of his large 

 Leyden battery, and would form a powerful stroke of lightning, if dis- 

 charged at once. 



The investigation gives us the first rough idea of the magnitude of the 

 quantities involved in frictional and voltaic electricity, and it may be 

 considered as the first rough approximation to the ratio of the electro- 

 magnetic to the electrostatic units of electricity. 



But Faraday was a chemist. His associations with Davy had made 

 him familiar from the first with the chemical action of the battery, and 

 it is but natural that his attention should be directed to its investiga- 

 tion. In the progress of these researches he noted the curious fact that 

 all bodies which could be decomposed by electricity when a fluid, could 

 neither conduct the current nor be decomposed by it when they were 

 solidified by the cold. The conduction and decomposition went to- 

 gether. Rising from this to a general law, he finally proved, by im- ' 

 mense labor, that, for a given quantity of electricity, whatever the de- 

 composing conductor may be, the amount of chemical action is the 

 same. The current, the size of the electrodes and the strength of the 

 solution might vary, but the amount decomposed by a given quantity of 

 electricity remained the same. Furthermore, the amount of different 

 substances separated was in proportion to their chemical equivalents. 

 Hence, the voltameter for measuring the electric currents which, in 

 the form of the silver voltameter, is to-day one of our most accurate in- 

 struments. 



As I have mentioned before, the leading idea in Faraday's mind was 

 the replacing of all action at a distance by curved lines of force which 

 had a definite physical existence. So, in attacking this subject of elec- 

 trolysis, he very quickly showed that Davy's idea that the poles sepa- 

 rated an electrolyte, by actually attracting its components, was false, 

 and that the theory, according to which decomposition and reeompo- 

 sition took place throughout the whole course of the current in the elec- 

 trolyte, was correct. 



