Edison's Electric Lighting System

From Research to Development

From the very beginning of his research Edison had periodically considered other elements of his system, such as meters and underground conductors, but the during the research phase he and his staff had focused on the lamp and generator.  With the shift to commercial development, they now paid greater attention to the rest of the system.  With an expanded staff Edison was able to assign the development of these minor though important components to his assistants. Nonetheless, the lamp remained the most important subject of research during 1880 as Edison sought a commercial lamp capable of hundreds of hours of use.  

Lamp research focused on each part from the filament to the electrical connections to the glass bulb.  Most of the experiments, however, were designed to find the best filament material for the commercial lamp. The lamps used during the New Year demonstrations were made with carbonized cardboard filaments in the shape of a horseshoe.  While cardboard worked for a demonstration, it had serious defects that made it impractical for use in a commercial lamp.  As one of his assistants later recounted,  Edison discovered that "Paper is no good.  Under the microscope it appears like a lot of sticks thrown together.  There are places where the fibres are packed and other places where there are few fibres, dense spots and great open holes."  If carbon was the solution, he still needed to find the best form of it.  In typical Edisonian fashion he told his staff, "Now I believe that somewhere in God Almighty's workshop there is a vegetable growth with geometrically parallel fibres suitable to our use.  Look for it.  Paper is man made and not good for filaments."  Edison assigned one of his chemists, Dr. Otto Moses, to make a systematic study of scientific literature on carbon substances which helped to guide the research.  Filament experiments soon focused on grasses and canes such as hemp, palmetto, and bamboo which possessed long, uniform fibers that would make for a sturdy long-lasting filament. By July 1880, bamboo and bast had become the most promising materials and by the beginning of December Edison finally settled on bamboo as the best material for the commercial lamp.

bamboo lamp and socket commercial

During the spring and summer the staff was busy building a full-scale model of his underground system at Menlo Park.  This system would allow him to test each component and also provide more exact knowledge regarding costs. The installation of the Menlo Park system provided the impetus for work on many of the components to be used in a commercial system, which Edison had put aside while focusing on the dynamo and lamp. During this period the staff worked on a variety of components, including metersfusessockets and fixtures. The underground system required a good insulation for the wires, and he placed Wilson Howell in charge of devising an insulating compound.  

By the late spring of 1880, Edison also began to consider the problems of lamp manufacture as he made plans to convert the old electric pen factory at Menlo Park into a lamp factory.  Although technical problems remained, Edison wanted to work out some of the manufacturing difficulties and to make large test runs of experimental lamps. During the summer he had his experimenters and machinists design special tools for making filamentsclamps, and bulbs.  The most important work focused on improved vacuum pump designs intended to reduce the time required to evacuate a lamp.  By the end of September the factory was producing experimental runs of bulbs.  At the end of December Francis Upton was placed in charge of the factory and regular production finally began in March or April 1881.

As he began to make plans for a large central station in New York, Edison designed a new steam dynamo to reduce the energy lost in the linkage between engine and generator.  Developed with steam engine maker Charles T. Porter, this was a 100-horsepower generator coupled directly to a high-speed steam engine that would waste less energy than using several smaller dynamos run from an engine with belts and pulleys. Charles Clarke, a mechanical engineer who had been Upton's classmate at Bowdoin College, was given the job of supervising the construction and testing of this dynamo.  This design came to be known as the "Jumbo," after the famous elephant exhibited by P. T. Barnum at Madison Square Garden in April 1882.  

Edison also had to convince the New York City Board of Aldermen to approve the laying of underground conductors for the station. He invited the Aldermen to come to the laboratory on Monday evening, December 20.  A reporter from Truth described the effect of the demonstration and the lobbying effort:

By this time the city fathers had begun to look quite dry and hungry, and as though refreshments would have looked much more palatable to them than the very scientific display they had been wondering at for two hours without a great deal of comprehension, although with a wonderful exhibition of understanding and appreciation. 

Their hopes were quickly realized by the announcement that the collation was ready. For half an hour only the clatter of dishes and the popping of champagne corks could be heard, and then the wine began to work and the Aldermen, true to their political instincts, began to howl, "Speech, speech." One of the witnesses of this visit said that the City Fathers were amazed at the appearance of the man they called "Professor" Edison. "Why," whispered one City Father to another, "he looks like a regular fellow. See how he handles his cigar—just like the boys in the Wigwam [Tammany Hall]."

More negotiations followed to work out the terms under which Edison interests would be allowed to dig up the streets, but the demonstration at Menlo Park left no doubt of the workability of the Edison system.

Menlo Park Lab Menlo Park shop Menlo Park upstairs
Dynamo Room, Pearl Street Station  Pearl Street Station cross section Map showing area lighted by Pearl St.

In March 1881, Edison moved his operations from Menlo Park to New York, where he expanded his manufacturing operations with three additional factories: the Edison Machine Works, which manufactured dynamos; the Electric Tube Company, which manufactured insulated underground condcutors; and Bergmann & Company, which manufactured most of the other small elements of the system.  Edison’s own time was largely spent overseeing the installation of the large central station plant on Pearl Street in lower Manhattan, which finally commenced operation on 4 September 1882, almost four years to the day after Edison began experimenting on the electric light. 

On the occasion of the 35th anniversary of the electric light Edison offered a prediction that foreshadows its impact on the modern world.  

“The one great value of the electric light – and the electric railway too – is that they expand mankind’s day. . . In the old days man went up and down with the sun.  A million years from now we won't go to bed at all.  Really, sleep is an absurdity, a bad habit.  We can't  suddenly throw off the thraldom of the habit, but we shall throw it off." 

Want to know more about the Menlo Park laboratory? Check out The Invention Factory.

Suggested reading: Edison's Electric Light by Robert Friedel and Paul Israel