CHRONOLOGY OF ELECTRIC LIGHT 



1800 — Allesandro Volta demonstrated his discovery that electricity 

 can be generated by chemical means. The Volt, the unit 

 of electric pressure, is named in his honor for this discovery 

 of the electric battery. 



1802 — Sir Humphry Davy demonstrated that electric current can heat 

 carbon and strips of metal to incandescence and give light. 



1809 — Sir Humphry Davy demonstrated that current will give a bril- 

 liant flame between the ends of two carbon pencils which are 

 first allowed to touch each other and then pulled apart. This 

 light he called the '' arc " on account of its arch shape. 



1820 — Andre Marie Ampere discovered that current flowing through 

 a coiled wire gives it the properties of a magnet. The Am- 

 TERE, the unit of flow of electric current, is named in his 

 honor for this discovery. 



1825 — Georg Simon Ohm discovered the relation between the voltage, 

 ampereage and resistance in an electric circuit, which is 

 called Ohm's Law. The Ohm, the unit of electric resis- 

 tance, is named in his honor for this discovery. 



183 1 — Michael Faraday discovered that electricity can be generated 

 by moving a wire in the neighborhood of a magnet, the 

 principle of the dynamo. 



1840 — Sir William Robert Grove demonstrated his experimental 

 incandescent lamp in which platinum is made incandescent 

 by current flowing through it. 



1 84 1 — Frederick De Moleyns obtained the first patent on an incan- 

 descent lamp. The burner was powdered charcoal operating 

 in an exhausted glass globe. 



1845 — Thomas Wright obtained the first patent on an arc light. 



1845 — J- ^^- Starr invented an incandescent lamp consisting of a 

 carbon pencil operating in the vacuum above a column of 

 mercury. 



1856 — Joseph Lacassagne and Henry Thiers invented the " differen- 

 tial " method of control of the arc which was universally 

 used twenty years later when the arc lamp was commercially 

 established. 



1862 — The first commercial installation of an electric light. An arc 

 light was put in a lighthouse in England. 



