HELMHOLTZ IN BERLIN 



of the air is great enough to make the common 

 velocity of the electrical and magnetic transversal 

 undulations equal to that of light.' 



Finding the notion of action at a distance in- 

 consistent with dynamic principles and with ex- 

 periment, he abandoned it and accepted Faraday's 

 principle. Then followed, as the years went by, 

 papers on the origin of electric currents and on 

 their action in circuit, on galvanic polarisation 

 of fluids free from gas, on the electrolysis of 

 water, on galvanic currents due to differences of 

 concentration of fluids, on electric border-plates, on 

 currents on polarised platinum, on the galvanic 

 polarisation of mercury, and on the capillary electro- 

 meter. In some of these papers the method followed 

 is less mathematical and more that of experiment 

 and induction ; but in all the fundamental principle 

 is the conservation of energy. In the tract on the 

 conservation of energy he had shown long before that 

 if the phenomena of Oersted and Ampere be assumed, 

 that is, if a wire carrying an electric current is 

 impelled across the lines of magnetic force, then the 

 phenomenon discovered by Faraday follows necessarily, 

 namely, a conductor moved across the lines of 

 magnetic force shows an electromotive force whose 

 intensity can be determined by the application of 

 the equation of energy. 1 



Ampere had stated the laws of action between 



' Tait, op. cit., p. 89. 

 O 



