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 resistance, is named in his honor for this discovery. 1831--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. 1841--Frederick De Moleyns obtained the first patent on an incandescent 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. W. 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 “differential” 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. 1866--Sir Charles Wheatstone invented the “self-excited” dynamo, now universally used. 1872--Lodyguine invented an incandescent lamp having a graphite burner operating in nitrogen gas. 1876--Paul Jablochkoff invented the “electric candle,” an arc light commercially used for lighting the boulevards in Paris. 1877–8--Arc light systems commercially established in the United States by William Wallace and Prof. Moses Farmer, Edward Weston, Charles F. Brush and Prof. Elihu Thomson and Edwin J. Houston. 1879--Thomas Alva Edison invented an incandescent lamp consisting of a high resistance carbon filament operating in a high vacuum maintained by an all glass globe. These principles are used in all incandescent lamps made today. He also invented a completely new system of distributing electricity at constant pressure, now universally used. 1882--Lucien Goulard and John D. Gibbs invented a series alternating current system of distributing electric current. This has not been commercially used. 1886--William Stanley invented a constant pressure alternating current system of distribution. This is universally used where current is to be distributed long distances. 1893--Louis B. Marks invented the enclosed carbon arc lamp. 1898--Bremer’s invention of the flame arc lamp, having carbons impregnated with various salts, commercially established.