A D V E N T U R E S in C Y B E R S O U N DEdison's Incandescent Electric Lamp, 1879
"We are striking it big in the electric light, better than my vivid imagination first conceived. Where this thing is going to stop Lord only knows." Prior to the invention of the electric lamp, America and the world relied on oil lamps and natural gas to illuminate the night. In the United States the gas companies became huge because they had no competition that offered an alternative to providing a source of light. By the middle 1800's every major city had miles of underground gas pipes that splintered off into homes and businesses to provide fuel for gas lamps and even cooking.
Francis Upton joined the laboratory force to provide the mathematical and theoretical expertise that Edison himself did not understand. It was primarliy "Ohms" law that Edison was unable to comprehend, which was key to the success of making the first practical electric light bulb For at least 50 years others had experimented with some sort of electric lamp, but none with success. In the period from 1878 to 1880 Edison and his associates worked on at least three thousand different theories while developing the incandescent lamp. The lamp would consist of a filament housed in a glass bulb, in a vaccum. He had his own glass blowing shed where the fragile bulbs were hand blown for his experiments. For the filament of his electric lamp, Edison's crew experimented on six thousand different types of materials. They eventually narrowed their filament choices down to just two. Edison and staff began working primarily with fine platinum wire, which proved unsuccessful. They tried mixing 10 percent iridium with the platinum, but problems continued because the filament still would not handle the current without melting. Eventually Edison got the idea of using a carbonized cotton thread. His first experiments with this method produced the Edison Effect or "Thermonic Emmission", caused by the flow of electricity from a hot filament across a vaccum to a metal wire. This development eventually led to the electronic vaccum tube.
The final filament chosen was carbonized cotton thread. The theory was that a current flowing through the carbonized filament would cause it to radiate a steady glow. The vaccum was needed to keep the filament from burning up. On October 21, 1879 Edison and his associates were ready to test their carbon filament light bulb. Voltage was applied to the terminals on the bottom of the fragile glass bulb and it immediately began to illuminate a soft orange glow. This first test lasted 13 hours before the tiny filament broke. Now that Edison and his staff had a working model, they had to determine a method of supplying the power to light the lamps. Edison had been using direct current in his experiments. He spent the next several years developing a commercial electrical system. In 1880 he purchased two buildings on Pearl Street in New York City to house his central power station. His staff manufactured huge dynamo's powered by coal, that would generate DC current fed to underground wires. Fourteen miles of wire were laid in a one square mile area from the Pearl Street power station. After nearly three years of work at Pearl Street, the system was brought on-line at 3 pm on September 4, 1882. Even though Edison was able to demonstrate he could supply electrical power, his method of using direct current had severe distance limitations. The DC distribution system meant that the building receiving the power had to be within a 2 to 3 mile radius of the power station. Other researchers including Nicola Tesla, were working with alternating current which could supply power to homes and buildings as far away as 200 miles. Edison never gave AC much research, believing that it was destructive to the human body. This is interesting to note in that for about the last two decades scientists have been warning of the harmful effects of electromotive radiation on the human body. Many believe prolonged exposure to high EMF's from high voltage power lines and home appliances can lead to cancer.
Source: http://www.naples.net/~arzone/invent.htm
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Thomas Edison knew there had to be alternative to the money hungry gas companies and set about to put them out of business. He was a man on a mission to generate electric power that would be cheaper to produce and provide a source for illumination. To that end he formed the Edison Electric Light Company in 1878, with a syndicate of leading financiers, including J.P. Morgan and the Vanderbilts, who advanced him $30,000 for research and development.