of the Galvanic Battery. 453 



vellous. We get from them heat sufficient to melt the most 

 refractory substances, or light of a dazzling brilliancy, which 

 approaches nearer to that of the sun than does any other arti- 

 ficial light. With a small fraction of the actual power of these 

 wires we can get volleys of electrical discharges, each one so 

 powerful that the strongest man could not endure it ; or we can 

 endow iron with the force of magnetism in its greatest intensity ; 

 and the compass forgets its steadfast direction when brought 

 near one of these wires, and commits vagaries which would cer- 

 tainly appear most alarming to navigators who are accustomed to 

 trust their lives to its directions ; and last, but not least, we can 

 decompose the strongest compounds, or combine the most slug- 

 gish and inert of elements by the action of the forces at work in 

 these wires. 



If a fairy gave you her wand, and told you that it was endowed 

 with power to evoke five of the chief forces in nature, as they 

 are often called, viz. heat, light, electricity, magnetism, and che- 

 mical affinity, with all their wondrous effects, you would surely 

 not despise the gift, or neglect to learn its use. Now this wire 

 is such a wand, and Science is the fairy who gives it you ; but, 

 like a wise and beneficent fairy, she tells you that you must 

 patiently examine and study its nature, and that its use will be 

 proportioned to the progress of that study. 



The successive discoveries and theories which have rapidly suc- 

 ceeded one another in this field of inquiry, and given us a know- 

 ledge of this wonderful instrument, constitute one of the most 

 brilliant and instructive chapters of scientific history. It is par- 

 ticularly interesting to notice how the metaphysical theory of 

 contact force, invented by the illustrious Volta, has gradually 

 given way before the steady advance of chemical discoveries, and 

 how we now explain it by describing the actual nature of the 

 transformations which occur in the working of the battery. 

 Many a clear head and steady hand has helped to work out our 

 knowledge of the subject ; but towering above them all in undis- 

 turbed preeminence, we see the figure of our own Faraday, a 

 man to whose fertile genius and indefatigable industry we owe 

 the chief discoveries relating to the chemistry of the galvanic 

 battery. 



But chemistry alone is unable to explain the forces at work in 

 this wonderful instrument, she is obliged to call other sciences 

 to her aid, and to combine physical and mechanical discoveries 

 with chemical ones in her final chain of facts. 



It has been proved beyond all dispute that heat is a motion of 

 atoms. Whenever the motion of masses is gradually or partially 

 arrested by the friction of the particles of one against those of 

 the other, we find that the particles get heated. Yet there is no 



