256 GREAT MEN OF SCIENCE 



meantime he was busy with work on the identity of all 

 kinds of electricity, in which he proved in detail that elec- 

 tricity from all known sources, including induction, is 

 exactly aUke in all its effects, which was necessary for mental 

 satisfaction in view of the rapid accumulation of new facts.^ 

 In this connection, Faraday for the first time measured 

 quantities of electricity by means of the galvanometer, 

 whereby he proved, for example, that the quantity of elec- 

 tricity delivered by a certain number of revolutions of an 

 electrical machine, when collected in a small or large 

 capacity, and thus by higher or lower voltage, and then dis- 

 charged through the galvanometer, always produces the 

 same deflection. This is the principle of the measurement 

 of electrical quantity by means of the 'ballistic' galvanometer, 

 and at the same time also the proof that the current strength 

 measured by the galvanometer actually represents quanti- 

 ties of electricity passing through it in unit time in accordance 

 with the conception introduced by Ampere. 



Further, in this period falls also Faraday's profound in- 

 vestigation of the chemical effects of electric currents, in 

 which he made a further great step forward beyond Davy 

 and Berzelius, by discovering, as a result of extensive quanti- 

 tative investigations, the two laws still known by his name 

 regarding the chemical effect of the current. In this con- 

 nection he also introduced the terms generally used to-day - 

 'electrolysis,' 'electrolyte,' 'electrode,' 'anode,' 'kathode,' 

 *ion'; and he also already investigated the secondary chemical 

 reactions so often occurring on the electrodes. On the first 

 of these two laws he founded his voltameter, which measures 

 current strength by means of the quantity of mixed gases 

 produced by electrolysis. The second law, which connects 

 chemical valency with ionic charge, has proved to be just as 



1 Davy had already interested himself in this problem, and had suc- 

 ceeded in showing the identity of the chemical effects of 'frictional' and 

 'voltaic' electricity. 



