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quantities for practical use are abundant. As the time 

 for experiments was necessarily short, the lecturer pro- 

 ceeded at once with them. He took, at first, one of the 

 simplest methods of developing a galvanic current. He 

 said this is done most effectually by subjecting to an acid 

 solution two metals of an entirely opposite nature, one of 

 which shall be most easily oxidized by the acid, and the 

 other not oxidized at all. The easily oxidized or positive 

 metal is commercial zinc ; the other or negative metal is 

 pure platinum, the most refractory and valuable of metals 

 to the chemist and the electrician. If the two metals 

 were alike, they would be acted upon equally, thus offer- 

 ing no inducement for a transfer of force from one to the 

 other, and consequently no electrical action. 



The lecturer then placed the metals in a glass of water, 

 slightly acidulated with sulphuric acid. The zinc plate 

 was amalgamated with mercury, so that no local action 

 should take place until the condition required for a trans- 

 fer of the tension or electro motive force from one plate 

 to the other was fulfilled. That condition is to place a 

 metallic connection from one plate to the other, outside of 

 the solution, as a conductor for the current to travel upon. 

 This was done with a piece of copper wire. The current 

 then was flowing rapidly along the wire, from the platinum 

 to the zinc plate. Through the solution it was flowing 

 from the zinc to the platinum. The water was decom- 

 posing, the oxygen evolving at the zinc plate and the 

 hydrogen at the platinum. The sulphur attacking the 

 zinc was precipitated in the form of crystallized sulphate 

 of zinc. 



The wire conductor may be one inch long or one thou- 

 sand miles long, and the electric force will be felt equally 

 along its whole length, the strength of battery being 

 equal to the resistance of the wire. Now to utilize this 



