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says Edison； 〃repudiated his contract with the automatic telegraph people and they never received a cent for their wires or patents； and I lost three years of very hard labor。 But I never had any grudge against him because he was so able in his line； and as long as my part was successful the money with me was a secondary consideration。 When Gould got the Western Union I knew no further progress in telegraphy was possible； and I went into other lines。〃*
* Quoted in Dyer and Martin。 〃Edison〃； vol。 1； p。 164。
In fact； however； the need of money forced Edison later on to resume his work for the Western Union Telegraph Company； both in telegraphy and telephony。 His connection with the telephone is told in another volume of this series。* He invented a carbon transmitter and sold it to the Western Union for one hundred thousand dollars； payable in seventeen annual installments of six thousand dollars。 He made a similar agreement for the same sum offered him for the patent of the electro…motograph。 He did not realize that these installments were only simple interest upon the sums due him。 These agreements are typical of Edison's commercial sense in the early years of his career as an inventor。 He worked only upon inventions for which there was a possible commercial demand and sold them for a trifle to get the money to meet the pay rolls of his different shops。 Later the inventor learned wisdom and associated with himself keen business men to their common profit。
* Hendrick； 〃The Age of Big Business〃。
Edison set up his laboratories and factories at Menlo Park； New Jersey； in 1876； and it was there that he invented the phonograph； for which he received the first patent in 1878。 It was there； too； that he began that wonderful series of experiments which gave to the world the incandescent lamp。 He had noticed the growing importance of open arc lighting； but was convinced that his mission was to produce an electric lamp for use within doors。 Forsaking for the moment his newborn phonograph； Edison applied himself in earnest to the problem of the lamp。 His first search was for a durable filament which would burn in a vacuum。 A series of experiments with platinum wire and with various refractory metals led to no satisfactory results。 Many other substances were tried； even human hair。 Edison concluded that carbon of some sort was the solution rather than a metal。 Almost coincidently； Swan； an Englishman； who had also been wrestling with this problem； came to the same conclusion。 Finally； one day in October； 1879； after fourteen months of hard work and the expenditure of forty thousand dollars； a carbonized cotton thread sealed in one of Edison's globes lasted forty hours。 〃If it will burn forty hours now；〃 said Edison； 〃I know I can make it burn a hundred。〃 And so he did。 A better filament was needed。 Edison found it in carbonized strips of bamboo。
Edison developed his own type of dynamo； the largest ever made up to that time； and； along with the Edison incandescent lamps； it was one of the wonders of the Paris Electrical Exposition of 1881。 The installation in Europe and America of plants for service followed。 Edison's first great central station； supplying power for three thousand lamps； was erected at Holborn Viaduct； London； in 1882； and in September of that year the Pearl Street Station in New York City； the first central station in America； was put into operation。
The incandescent lamp and the central power station； considered together； may be regarded as one of the most fruitful conceptions in the history of applied electricity。 It comprised a complete generating； distributing； and utilizing system； from the dynamo to the very lamp at the fixture； ready for use。 It even included a meter to determine the current actually consumed。 The success of the system was complete； and as fast as lamps and generators could be produced they were installed to give a service at once recognized as superior to any other form of lighting。 By 1885 the Edison lighting system was commercially developed in all its essentials； though still subject to many improvements and capable of great enlargement； and soon Edison。 sold out his interests in it and turned his great mind to other inventions。
The inventive ingenuity of others brought in time better and more economical incandescent lamps。 From the filaments of bamboo fiber the next step was to filaments of cellulose in the form of cotton； duly prepared and carbonized。 Later （1905） came the metalized carbon filament and finally the employment of tantalum or tungsten。 The tungsten lamps first made were very delicate； and it was not until W。 D。 Coolidge； in the research laboratories of the General Electric Company at Schenectady； invented a process for producing ductile tungsten that they became available for general use。
The dynamo and the central power station brought the electric motor into action。 The dynamo and the motor do precisely opposite things。 The dynamo converts mechanical energy into electric energy。 The motor transforms electric energy into mechanical energy。 But the two work in partnership and without the dynamo to manufacture the power the motor could not thrive。 Moreover； the central station was needed to distribute the power for transportation as well as for lighting。
The first motors to use Edison station current were designed by Frank J。 Sprague； a graduate of the Naval Academy； who had worked with Edison； as have many of the foremost electrical engineers of America and Europe。 These small motors possessed several advantages over the big steam engine。 They ran smoothly and noiselessly on account of the absence of reciprocating parts。 They consumed current only when in use。 They could be installed and connected with a minimum of trouble and expense。 They emitted neither smell nor smoke。 Edison built an experimental electric railway line at Menlo Park in 1880 and proved its practicability。 Meanwhile； however； as he worked on his motors and dynamos； he was anticipated by others in some of his inventions。 It would not be fair to say that Edison and Sprague alone developed the electric railway； for there were several others who made important contributions。 Stephen D。 Field of Stockbridge； Massachusetts； had a patent which the Edison interests found it necessary to acquire； C。 J。 Van Depoele and Leo Daft made important contributions to the trolley system。 In Cleveland in 1884 an electric railway on a small scale was opened to the public。 But Sprague's first electric railway； built at Richmond； Virginia； in 1887； as a complete system； is generally hailed as the true pioneer of electric transportation in the United States。 Thereafter the electric railway spread quickly over the land； obliterating the old horsecars and greatly enlarging the circumference of the city。 Moreover； on the steam roads； at all the great terminals； and wherever there were tunnels to be passed through； the old giant steam engine in time yielded place to the electric motor。
The application of the electric motor to the 〃vertical railway；〃 or elevator； made possible the steel skyscraper。 The elevator； of course； is an old device。 It was improved and developed in America by Elisha Graves Otis； an inventor who lived and died before the Civil War and whose sons afterward erected a great business on foundations laid by him。 The first Otis elevators were moved by steam or hydraulic power。 They were slow； noisy； and difficult of control。 After the electric motor came in； the elevator soon changed its character and adapted itself to the imperative demands of the towering； skeleton…framed buildings which were rising in every city。
Edison； already famous as 〃the Wizard of Menlo Park；〃 established his factories and laboratories at West Orange； New Jersey； in 1887； whence he has since sent forth a constant stream of inventions； some new and startling； others improvements on old devices。 The achievements of several other inventors in the electrical field have been only less noteworthy than his。 The new profession of electrical engineering called to its service great numbers of able men。 Manufacturers of electrical machinery established research departments and employed inventors。 The times had indeed changed sinc