xii PREFACE TO THE FIFTH EDITION. 



obtain Electricity from Magnetism it was necessary to super- 

 add to this latter, motion ; that magnets while in motion 

 induced electricity in contiguous conductors ; and that the 

 direction of such electric-currents was tangential to the polar 

 direction of the magnet ; that as Dynamic-electricity may be 

 made the source of Magnetism and Motion, so Magnetism 

 conjoined with Motion may be made the source of Electricity. 

 Here originates the Science of Magneto-electricity, the true 

 converse of Electro-magnetism ; and thus between Electricity 

 and Magnetism is shown to exist a reciprocity of force such 

 that, considering either as the primary agent, the other be- 

 comes the re-agent ; viewing one in the relation of cause, the 

 other is the effect 



The Science of Thermo-electricity connected heat with 

 electricity, and proved these, like all other natural forces, to 

 be capable of mutual reaction 



Voltaic action is Chemical action taking place at a dis- 

 tance, or transferred through a chain of media ; and the 

 Daltonian equivalent numbers are the exponents of the 

 amount of voltaic action for corresponding chemical sub- 

 stances 



By regarding the quantity of electrical, as directly pro- 

 portional to the efficient chemical action, and by experimen- 

 tally tracing this principle, I have been fortunate enough to 

 increase the power of the Voltaic-pile more than sixteen 

 times, as compared with any combination previously 

 known 



I am strongly disposed to consider that the facts of 

 Catalysis depend upon voltaic action, to generate which three 

 heterogeneous substances are always necessary. Induced by 

 this belief, I made some experiments on the subject, and suc- 

 ceeded in forming a voltaic combination by gaseous-oxygen, 

 gaseous-hydrogen, and platinum, by which a galvanometer 

 was deflected and water decomposed 



