THE CONQUEST OF NATURE 



DAVY AND THE FIRST ELECTRIC LIGHT 



As soon as Volta's great invention was made known 

 a new wave of enthusiasm in the field of electricity swept 

 over the world, for the constant and relatively tractable 

 current of the galvanic battery suggested possibilities 

 not conceivable with the older friction machines. Bat- 

 teries containing large numbers of cells were devised; 

 one having two thousand such elements being con- 

 structed for Sir Humphry Davy at the Royal Institu- 

 tion, of London. By bringing two points of carbon, 

 representing the two poles of the battery, close together, 

 Davy caused a jet of flame to play between them 

 not a momentary spark, but a continuous light a true 

 voltaic arc, like that seen in the modern street-light 

 to-day. 



"When pieces of charcoal about an inch long and 

 one-sixth of an inch in diameter were brought near each 

 other (within the thirtieth or fortieth of an inch)," 

 wrote Davy in describing this experiment, "a bright 

 spark was produced, and more than half the volume of 

 charcoal became ignited to whiteness; and, by with- 

 drawing the points from each other, a constant discharge 

 took place through the heated air, in a space equal to at 

 least four inches, producing a most brilliant ascending 

 arch of light, broad and conical in form in the middle. 

 When any substance was introduced into this arch, it 

 instantly became ignited ; platina melted in it as readily 

 as wax in a common candle; quartz, the sapphire, 

 magnesia, lime, all entered into fusion ; fragments of dia- 



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