Thomas Alva Edison (Figure 1)…One of the most prolific and legendary inventors history has ever seen. Indeed, “in the United States, where few questioned the values of the technological process, Edison, the ‘uncommon,’ common man, had become a revolutionary figure akin to the Founding Fathers. He did not just invent new and useful things but changed the way men and women” lived and continue to live today. Every one of his inventions can be considered a turning point in history but the incandescent lamp, direct current, and the battery/fuel cell truly changed the face of history; the War or Currents was a turning point because it marked the first time that electricity began to be widely used commercially and residentially in the United States.
From the very beginning, Edison had been fond of science. The thought of science. The questions of science. And the construction of science.Everything fascinated him. When his mother gave him a book of experiments, he bought chemicals, dictionaries, test tubes, and scraps to do experiments with. This book eventually shaped Thomas Alva Edison as he took a job with James Mackenzie, a professional telegrapher, who promised to help Al (as he became known as) master telegraphy. Before Al’s career, when trying to communicate via telegraph between faraway cities, currents leaked and as a result signals faded rapidly; in addition, the machine was very unreliable. But Edison changed the face of the telegraphy and almost reinvented it to create an incredible communications device that would play a decisive role in history—mainly World War I and World War II. And indeed, most of Edison’s patents came not from the light bulb or phonograph—as is the modern misconception—but from the telegraph (Figure 2). To correct the problem of leaky currents, Al built relay instruments that would help correct this monumental issue.
Figure 2: Edison’s 1872 Telegraph
Ultimately, might the Central Powers have won WWI or the Axis have won WWII without the improvements Edison made to the telegraph? Might the Zimmerman telegraph never have been intercepted? Or might the telephone never have been invented because of the obvious failures of the pre-Edison telegraph? While we may never be able to justify a one-hundred percent sure “yes” or “no” answer, the questions certainly do advocate the idea that Edison’s improvements to the telegraph became a turning point in history.
But perhaps Edison’s best known contribution to the modern world was his invention of the incandescent lamp. 200 years ago, people lived in the dark, literally; the only sources for artificial light were kerosene lamps, illuminating gas, arc-lighting, and candles. There were no bulbs and efficiency of doing work at night was significantly low. The story of Edison’s light bulb started when Grosvenor Lowry, Edison’s legal advisor, advised him about the great possible income from electrical power; this would free Edison from market preoccupations—something he abhorred—so he could devote all his time to invention—something he loved. And Edison’s visit to Sierra Nevada and the Rocky Mountains, where he saw the dark and desolate conditions that the men worked in, increased his enthusiasm to create electric light. This relationship eventually ended up making Edison’s Electric Light Co., a company to “own, manufacture, operate, and license the use of various apparatuses used in producing light, heat, or power by electricity.” 
But Edison did not really invent the light bulb, he reinvented it. Before Edison’s lamp, arc-lighting (Figure 3) was frequently used. It involved two pencil like carbon rods—“filaments,” a word Edison coined—which were separated in a “globe of opal glass [that] ‘gave a peculiar silver luster to light which resembled that of the moon.’”  One spectator said that arc-lighting was “brilliant as a fourth of July sparkler.” But the downfall of arc-lighting was that the bulbs, like a candle, burned down in an hour or two. Moreover, they could only be used outdoors, the bulbs produced a deep hissing sound, they were un-adjustable, and they threw off embers. Furthermore, the bulbs required gas; but gas was expensive, extremely explosive, and caused headaches because of the smell of sulfur or ammonia. Coupled with the fact that its price was sky-high and there was no powerful enough sustained electrical source , there was truly no reason to purchase arc-lighting when candles or kerosene lamps were just as—if not more—effective than the expensive bulbs. Imagine what life would be like today if Edison had not reinvented the light bulb and if candles and arc-lighting were still in effect. His reinvention of the bulb was a turning point because it inevitably was used to make enormous historical decisions.
However, the person to truly inspire Edison was William Wallace who divided power among eight arc-lamps with a circuit breaker. This was catalyst for Edison as it was the first time that electricity had been provided from one source. He was very excited about this: “With ten lights have been produced by a single electrical machine, it has been a triumph of scientific skill. With produce a thousand – aye ten thousand – from one machine. Indeed the number may be infinite.” This became Edison’s goal: to control output and efficiently power many bulbs from one power source. And he became set that “when light leaves the laboratory, [it will be in] such shape that it cannot get out of order at all, except of course by some accident.” Indeed, scientists and researchers before Edison had created systems of electric lighting that were adequate, but no one—not even Wallace as his system was very ineffective—had created a system in which all bulbs were lit by one source. And as trivial as this may sound, it was and is truly revolutionary to not have to pay a light bill for every light bulb one owns. Edison changed the course of history by instigating the idea that everything in a building should be powered from one source not multiple sources. In addition, contrary to arc-lighting’s series wire distribution system, in which if one lamp went out, all went out, Edison used a parallel wire distribution system in which voltage could be held constant and lamps could be added or dropped at will ; this was also revolutionary as this had never been done before in this field. Though he did not invent the method, he did popularize it. It is still used today.
At first, Edison started off using platinum wire but this only allowed him to alight 18 lamps, equal to 16 candles; he had created a prototype that worked greatly in the lab but one that was not ready to enter into the real world. Then the epiphany came when Edison decided to utilize carbon filament instead of a platinum one as the latter is not only more expensive but also more scarce than the former. Now the bulb (Figure 4) glowed “like a yellow sun-set of an Italian autumn…a little globe of sunshine, a veritable of Aladdin’s lamp… [And] in a twinkling, the area bound by space, wall, and Nassau, and Pearl Street was in a glow.” Edison later tested tantalum and titanium filaments and discovered that titanium filaments were even more superior to carbon because of the high temperatures and stress they could withstand when coupled with inert nitrogen gas inside the bulb. And the result was revolutionary as Menlo Park became an electric showplace and everyone in the town was rushing to be employed by the wizard that had reinvented the world with his lamp. But in addition to Menlo Park, “two hundred sites across America—mills, factories, hotels, steamships, stores, and residences,” were alight with over 45,000 bulbs. This is perhaps Edison’s most lasting invention without which life would truly be different; modern discoveries might not have been made without the light needed to make them, rate of crime may have increased, and rate of fires might increase as result of greater consumption of candles. Would we still be living in the dark without it?
And even though Edison is not as well known for his work in electricity, he made huge contributions that changed the face of history and life today. But most of his contributions arose in “the first and nastiest standards war [which] was fought between Alternating Current (AC) [masterminded by George Westinghouse and Nikola Tesla (Figure 5)] and Direct Current (DC) [masterminded by Thomas Edison].” The major difference between AC and DC is that in AC, current alternated in direction as the dynamo armature revolved while in DC, the current did not alternate (it went directly); DC required low voltages to be effective and avoided dangerous sparking; AC was far more effective for electric power transmission over long distances. Though this war occurred long before modern standards wars such as “VHS versus Betamax, Windows versus Macintosh, or Blu-Ray versus HD-DVD,” it marked the first time electricity was used extensively outside the laboratory setting and its effects still play an integral part in determining today’s electricity. But this so called war was not fought with guns and armies and generals but with words and only with words. Edison seemed to have an emotional, rather than practical attachment to DC. Pragmatically, consumers favored a system that served a wide area, and could be distributed more economically and greater distances; AC did exactly that. This was because AC utilized transformers which could be used to step up or step down voltages; these transformers allowed for efficient power transmission over long distances. On the other hand, because of high costs, DC could only serve small districts (similar to Pearl Street—Figure 6). But Edison believed that DC was superior because the incandescent lamps that he invented were powered by direct current. He also thought they were superior because in addition to lighting up to the dark, DC could be used to drive streetcars and factory machinery; AC could not do this. Nevertheless, because AC served a larger area, sales for Edison’s Light Company fell dramatically and hopes for the company fell. But Edison was not going to
Figure 7: Edison’s last move in the War
give up so he launched the war to regain the electric power. In his words, “there is no point in introduction of electricity so dangerous to people” and “the only remedy is to restrict electrical pressures,” something that DC did. This war of words was a turning point in history because after it, electricity (both AC and DC) began to be widely used; before the war, scientists were just researching in the lab (under controlled conditions, with small voltages and small danger, and with small risk of failure), but after, electricity was introduced into the modern world. One must deeply contemplate its deep roots in today’s society and in the course of history to truly appreciate how integral electricity is to the lives of every creature and being on the planet. Would the second industrial revolution have been as successful as it was without it? Would we have as much electronic technology as we do today without it? Either way, the war and Edison must be thanked.
Nevertheless, the story of the War of Currents is long and complicated; still, it must be understood to completely appreciate how the war was a turning point in history. Edison tried to show that this direct current was safe because it utilized copper conduits that avoided hazards as they were under the street; on the other hand, alternating current did not and was, in his eyes, hence deadly. As such, he labeled Westinghouse as a “shyster” and the “enemy” and began saying that AC is “electricide:” a combination of “homicide” and “suicide.” But Edison’s conviction that AC was any more dangerous than DC was a fallacy that appeared true superficially but was false on a deeper level; this is because Edison focused on voltage (the force that pushes electricity through wire) and not amperage (the rate of flow of electricity). Solely based on voltage, the electric pressure should stay under 1200 volts to be safe; but as Edison argues in North American Review, AC had a pressure of 1000 to 3000 volts. So in Edison’s eyes, it had to be dangerous, right? Edison’s campaign argued that contact to AC wires meant instantaneous death. And to his morbid delight, there were accidents; in one, Niram Corliss, a longtime employee of an electric company, was climbing a pole to see what was wrong with the lighting when AC wire touched him and he was “struck dead in a second,”  without “the least distorted” feelings and without any visible bruises. But in reality, the event was truly based on chance: it was something that could have happened to anyone with any (including DC) type of lighting. Westinghouse challenged that the dangers were inevitable in a modern city: ‘“If all things involving the use of power were to be prohibited because of the danger to life, then the cable wars, which have already killed a number of people, would figurehave to be abolished. Should we say bye to railroads too?” Here Westinghouse tries to regain his credibility utilizing pathos by relating the deaths to inventions that have become an essential part of their life, such as the railroad. Edison tried to justify this and continue to scare the public by arguing that “right now there are limited deaths but with [the AC] system spreading, deaths will spread.” Furthermore, he tried to undermine Westinghouse’s reputation by finding out how much current was needed to execute a human being. So Edison’s company began offering 25 cents for dogs to be used as surrogates for humans in the lab; the company even electrocuted an elephant. Westinghouse fired back saying that danger did not come from current type but from inadequate insulation; if shielded, wires are perfectly safe.” This became very important in the course of history because now, as result of all the accidental deaths that had occurred during the war of currents, companies would be sure to insure that there was shielding on top of wire—it became a lesson.
To some extent, Edison’s campaign was successful; many states, mainly New York, took up electrocution with electric chair as primary source of execution rather than hanging. And on August 6, 1890, William Kemmler (Figure 8) was first to be electrocuted; his execution was done as a trial to see if it was just to electrocute a man. But the results were anything but what Edison had expected; the criminal did not die when the switch was pulled (it had to be pulled again to ensure death). The New York Times even said that the chair was “far worse than hanging” and a “disgrace to civilization.” Nevertheless, this was perhaps the first time in history when electricity began to be used legally outside of the lab setting: a true turning point in history.
Eventually AC won a landslide victory because people did not seem to care about how dangerous AC was; by 1920, 1000 American had died from electric shock but the appeal of cheap electricity trumped the scare of danger. AC was significantly less expensive because DC required expensive investments in the copper wire necessary. Edison’s campaigning had failed. DC had failed. Edison had failed. At this point, it may seem as if the war was not a turning point—Edison lost after all didn’t he? But on a deeper level, the war marked the first time in history when electricity, even if it was not Edison’s creation, began to be used in everyday, pedestrian life. As one spectator exclaimed, “ELECTRIC GIVING…THE PROMISE OF THE FUTURE. Its tireless energy takes place of yesterday’s human effort. [It] has woven itself so inseparably into our lives that its miracles are taken for granted.” Indeed, now electricity could be used efficiently and with little cost more commonly; this significantly reduced the amount of human effort needed, became a tool essential for everyday life, and historically, played a vital part in the Second Industrial Revolution and in the manufacture of many, many weapons.
But Edison was once again steadfast; if DC was not going to be used to deliver electricity to homes and businesses, it could at least be used to power a storage battery (Figure 9)—a box of direct current, right? This appealed to Edison because he yearned for an electric car with an electric battery. But Edison was not trying to invent a primary battery which converts chemical energy to electricity and exhausts itself (and which had already been invented) but a secondary/storage battery which could be charged and recharged multiple times. Earlier on, the storage battery was a lead and acid battery in which the two chemicals combined to spark a chemical reaction that produced a DC flow; but this battery was remarkably heavy and dangerously corrosive and so it was unsafe to use with an automobile. Edison wanted to invent a lightweight, noncorrosive, battery to power a car hundreds of miles on a single charge. Edison knew that if he invented a superior storage battery, he would “open up new epoch in electricity” in which DC holds its rightful place with (not above since he lost War of Currents) AC.
Figure 9: Edison’s 1918 Storage Battery
“Out of Menlo Park came improved telegraph and telephone systems, dynamos, electric rail system, and photoelectric effect. The phonograph also sprang from Menlo Park.” These inventions all clearly changed the face of history yesterday and continue to do so today and are therefore all turning points; but all of them have been upgraded, changed, or redesigned throughout time. Edison’s success with the battery similarly affected the course of history and continues to affect us; but it is different in that the battery today is very similar to the Edison battery of the 20th century—perhaps this is his only invention that applies. The fact that the battery’s ideas are still being applied truly demonstrates how much ahead of its time it was: it changed history. Nevertheless, without the battery, there would be no electric car, no airplane, no electric train, and no cell phone. Indeed, without the battery, Henry Ford may never have come up with design for the modern vehicle. Edison’s first battery was the E battery made of Nickel, Iron, and an alkaline solution of Potassium Hydroxide; but this was a failure as it leaked and lost power quickly.  Then the idea of the A battery came; it had two metal electrodes in which a mixture of iron compounds and carbon gives off electricity to sheets of nickel, therefore discharging that battery. It was an excellent conductor of electricity. He exclaimed that there would now be “a miniature dynamo in every home…an automobile for every family,” and said that the time has come “when every man may not only be able to light his own house, but charge machinery…work his food by electricity without depending on anyone for these services.” And this time, Edison’s gloating was not premature as the A battery was not only lighter than the former lead-acid batteries, but also could be charged in half the time and lasted more than three times longer. Edison had succeeded and had changed the world yet another time. And according to the Detroit Electric Car Company, “next season an electric not thus equipped [with the Edison battery] will be as outdated as a single-cylinder gas engine.” Indeed, the Edison battery changed the face of the world by enabling the world to be more portable: a turning point in history that eventually led to the mobile age today.
The War or Currents was a turning point in history because marked the first time electricity began to be widely used outside the lab; but the invention of direct current (even though it and Edison lost the war) was also a turning point in history because it is still used in a variety of different ways today. AC was actually not perfect because it required the peaks and valleys of the 60 hertz alternating currents to be synchronized when electricity is sent from one area of the grid to another part; but this was not always possible and so DC was used to connect out-of-step sections of the AC grid. Indeed, without Edison’s invention of DC, some sections of the country might not be getting electricity; even though it only assists AC, it was used and is used to ensure electricity in every corner of the country; although not as flagrant a turning point as the invention of AC, the invention of DC still changed the face of history by letting electricity access every notch of America.Batteries have not changed much from Edison’s age. Edison’s battery laid the foundations for the Lithium ion battery that is most commonly used today; but his nickel-iron battery is making a comeback because its material
components are cheaper than those of a Lithium cell. At the same time, fuel cells (Figure 10) seem to continually take over batteries’ jobs altogether. They use hydrogen and then strip it of an electron. Then the remaining positively charged hydrogen ions (H+) combine with oxygen to form water. Theoretically, it can power something indefinitely as long as hydrogen and oxygen is present.  This DC powered engine may bring an end to the internal combustion engine. One has to ask himself: without Edison’s invention of the DC, would Lithium ion batteries or hydrogen powered vehicles exist today? Probably not.
Furthermore, the genius of Edison and Westinghouse in the War of Currents laid the foundations for electric power generator and mass transit rail electrification efforts such as New York Subway and Norfolk – West railroad. Now, almost every major city across the world has a subway system and many homes have generators. The invention of these was a turning point because they revolutionized public transportation. Edison is once again the man to thank.
Now there are a growing number of high voltage DC lines like the 850 mile line that connects the Pacific Northwest and LA; the revolutionary part of this HVDC (as it has become called) is that the high voltage lets one step up or step down the voltage and does exactly what a transformer does for AC. And HVDC is used to connect different countries’ AC power systems. As seen in Figure 11, HVDC transformers are located all over the world. This HVDC technology may not have been invented if Edison had not discovered DC in the nineteenth century: it was a turning point.
The invention of DC was a turning point in history because DC can also be used to send electricity underwater with a cable. AC cannot be used for this purpose because AC builds up high capacitance—stored electric charge—which has to be overcome; but DC is completely unaffected from being used underwater. Today, there is a 155 mile line from Sweden to Germany under the Baltic Sea and a 67 mile line from New Jersey to Long Island that uses this technology. Without Edison discovering DC, these lines could not have been built and some sections of land near the areas mentioned above may not receive electricity; the invention of DC, even if it failed in the 19th century, was a true turning point in history.
It took more than a century just for DC to supplement AC; but now every portable device from a laptop to a cell phone to a PDA to a MP3 Player runs on DC. Even in industry, DC is used: railway signals, industrial machinery, miner’s lamp, and hand truck all utilize DC. And today, the world seems to be making a run towards a world that is connected 24/7. This calls for devices untethered from wall outlets and wires; so they have to be powered by batteries or fuel cells. Are we slowly moving from AC to DC? Alternating current may have dominated the industrial age but the computer age is bound to be dominated by direct current; the computer age is bound to be DC’s vengeance upon AC. Again, without Edison’s discovery of DC, there may have never been a computer age. The innovation of direct current is irrefutably a turning point in history.
Today, Thomas Alva Edison’s legacy continues to amaze every being on earth. He became the founder of General Electric (GE), the leading supplier of equipment for producing stoves, dynamos, refrigerators, transformers, airplanes, transmission lines, engine boosters, and X-Ray machines.  Edison was truly a Renaissance man of his time, without whom we may not have any of the above items. GE would not have existed without Edison; he completely changed the course of history by leading the mass production of common household items for low prices (to some extent even before Henry Ford did with the automobile).
Something that defined Edison’s inventions was that they were all practical even though he was just utilizing them to gain money. In his own words, “A scientific man busies himself with theory. He is absolutely impractical. An inventor is essentially practical.” All of his inventions were also topical and jumped into mainstreamed technology—like the telegraph, or developing technology such as the telephone, light, X-ray, or rubber.  Perhaps this is why his life was a turning point in history; because he invented items that the common person could use, items that were practical, and items that were topical.
Whatever reason one believes in, “The Wizard of Menlo Park” was truly a wizard who changed the face of the earth. But with his 1093 patents, the majority of his patents/inventions could not be discussed and so will be briefly mentioned here. The repeater let the user slow the speed at which incoming telegraph messages came at. The printer let user ascribe/translate telegraph signals into Roman characters. The perforator was the opposite of printer and encoded characters for translation by an automatic telegraph system. The Quaduplex was known as multiple telegraphy and let user handle multiple messages at the same time. Electromotograph was a musical telephone that later evolved into the phonograph by Edison. The phonograph later was used by Edison to make the kinescope and start developing motionpictures.
Here is a poem written by the genius himself:
“I am the wizard of the Electric Light
And a hide awake wizard too.
I see you’re rather bright and appreciate the might
Of what I daily do
Quadruplex, telegraph, or try phonograph
It’s all the same tone;
With ideas I evolve and problems I solve…” 
It is clear now to say that Thomas Alva Edison was truly the Wizard of Menlo Mark.
 Harold Green, “The Wizard of Menlo Park: How Thomas Edison Invented the
Modern World.” International Social Science Review 84, no. ¾ (2009): 193. MasterFILE Premier, EBSCOhost, http://search.ebscohost.com/login.aspx?direct=true&AuthType=
cookie,ip,cpid&custid=cincy&db=f5h&AN=47559849&site=ehost-live, Internet, Accessed December 18, 2012, n.p.
 Jan Adkins, Thomas Edison (New York: DK Publishing, 2009), 10-29.
 Ibid., 26-29.
 John S. Anderson, John M. Saby, “The electric lamp: 100 years of applied
This primary source talks about why alternating current is dangerous and why it should be not be used anymore; it talks about the positives of DC over AC. It also talks of the imminent possibility of death if AC is continued to be used. Since, it is primary source, it provides great quotations about Edison’s beliefs.
“FAR WORSE THAN HANGING – KEMMLER’S DEATH PROVES AN AWFUL
SPECTACLE.” The New York Times, August 7, 1890. http://query.nytimes.com /mem/archive-free/pdf?res=9E06E4D9133BE533A25754C0A96E9C94619ED7CF (accessed January 1, 2013).
This source describes Kemmler’s awful death on the electric chair. He had to be electrocuted twice before he died. And the source says that the electrocution in far worse than hanging. It is a great source because it has many great quotes of the people who were at the scene when it happened; the reporter was at the scene as well.
Green, Harold M. 2009. “The Wizard of Menlo Park: How Thomas Edison Invented the Modern
World.” International Social Science Review 84, no.314: 193. MasterFILE Premier, EBSCOhost (accessed December 18, 2012).
This journal has a great quote describing how Thomas Edison has become a revolutionary figure. It describes how Edison completely changed the way people live today.
Killed by an Electric Shock, New York Times, October 7, 1887. http;//query.nytimes.com/mem/
This source contains information about a man who was accidently electrocuted by AC wires. Since it was written by someone who was at the scene when the event occurred, it has a lot of quotes. Overall it is a great source to get information from.
aspx?direct=true&AuthType=cookie,ip,cpid&custid=cincy&db=aph&AN=14428300&site=ehost-live (accessed January 1, 2013).
This source contains information about Edison’s storage battery and how it had been a century ahead of its time. It explains how it works and also explains that to some extent it is still being used today.
Varrasi, John. “The Age of Ingenuity.” Mechanical Engineering 127, no. 2 (2005):
direct=true&AuthType=cookie,ip,cpid&custid=cincy&db=f5h&AN=15865025&site=ehost-live (accessed December 20, 2012).
This source contains empirical information on the advantages and disadvantages of AC and DC. It also contains empirical information on how AC and DC affected the world today. However, it does not go into much depth.
Adkins, Jan. Thomas Edison. New York: DK Publishing, 2009.
This source presents Edison’s life chronologically but does not go into much detail or description. All events are superficially described and depth is not present. At the same time, it gives a holistic overview of Edison’s life. It has a lot of information about Edison’s childhood and how his passion for inventing developed.
Baldwin, Neil. Edison: Inventing the Century. New York: Hyperion, 1995.
This source contains a lot of information describing Edison’s invention of the incandescent lamp. It contains a plethora of details and has several chapters devoted solely to the light bulb. It also contains information about the Edison’s storage battery, DC, and the War of Current with Westinghouse.
Conot, Robert. A Streak of Luck: the Life and Legend of Thomas Alva Edison. New York:
Seaview Books, 1977.
This source contains a holistic overview of all of Edison’s inventions. It briefly describes each of his prominent inventions and describes the affect it has on life today. The source also contains a breakdown of which area each of Edison’s 1093 patents came from i.e. lighting, electricity, battery, motion pictures.
McNichol, Tom. AC/DC: The Savage Tale of the First Standards War. San Francisco:
This book is devoted to the War of Currents and therefore has tons of details about the war of words. However, it seems to be biased towards Edison and does not include a lot of information or opinions of opponents such as Westinghouse or Tesla. Nevertheless, in addition to discussing AC and DC, it also contains information about Edison’s other inventions and includes info about the effect of Edison’s inventions on the world today.
Stross, Randall. The Wizard of Menlo Park. New York: Crown Publishers, 2007.
This source provided a tremendous amount of information about the War of Currents. It has a plethora of quotes by all the major players including Edison and Westinghouse. It presents the conflict in an easy to understand chronological order. It presents the issue from multiple points of views and is a great source for information about the war of currents.
Barrett, Simon. “Westinghouse (The Minutes Of History).” Blogger News Network.
http://www.bloggernews.net/124093 (accessed January 5, 2013).
This is a picture of George Westinghouse and Nikola Tesla. They were partners advocating AC against Edison and DC.
“Converter Transformer – Siemens.” Siemens Energy Sector.
http://www.energy.siemens.com/us/en/power-transmission/hvdc/hvdc-classic/converter-transformer.htm (accessed January 5, 2013).
This is a picture of the locations of HVDC transformers today. It demonstrates the extent of their usage.
“Electric Light and Power System – The Edison Papers.” The Thomas A. Edison Papers.
http://edison.rutgers.edu/power.htm (accessed January 5, 2013).
This is a picture of the Pearl Street dynamo DC warehouse. It was Edison’s first electric warehouse.
“History of Lighting 1888.” Global Greenhouse Warming.