Tesla: Powering the World

     When examining the modern world, it soon becomes abundantly clear that all the conveniences and technical achievements we utilize to better our lives have a singular thread inescapably interweaving nearly every facet of each: energy. Energy is the cornerstone of modern society and without our ever-increasing demand and production of such, our world, among other things, would be much dimmer. The toothbrushes we use to clean our teeth, the cars we drive, the cell phones we use, and every other electronic device and piece of machinery that has become an integral part of our interactions were produced, first and foremost, with the use of electrical energy. We take for granted the fact that we flip a switch and lights instantaneously come on; or that we can plug our devices into outlets across the country and marvel at the ease with which our manufactured boredom can become manufactured pleasure. How convenient! But, the extraordinary amount of engineering and innovation it took to transmit that energy over vast distances—sometimes hundreds of miles—is a story millennia in the making. So, what exactly does it take for long-distance energy transmission and how in the world was such a concept ever conceived?

     By the mid-1850s, much work in the understanding of electricity had been conducted by heavy-hitters in the field—notably, Alessandro Volta and his battery concept in 1800; Hans Orsted, discovering magnetic field induction; George Ohm with electrical resistance; Michael Faraday, who published his Law of Induction in 1831; and Joseph Henry, developing the DC motor that same year.1 But, it would be several decades before a man named Nikola Tesla synthesized several of these concepts in an engineering tour de force that would forever change the course of human history. It is quite difficult to point to a single of Tesla’s innovations and call it the be-all-end-all. But we can get close if considering present widespread application. In any case, it is important to understand the progression as it unfolded in Tesla’s life. He was perhaps one of the greatest contributors to human progress to have ever lived. With nearly 300 patents awarded2, Tesla’s impact on our modern world is undoubted. And, while it can be argued that another determined experimenter might have arrived at similar innovations, it was ultimately the work of this rather strange, yet fascinating man that molded the world we enjoy today.

     We now transmit power long distances exclusively by means of alternating current. Practically everything that the civilized world does revolves around the ongoing, rapid production and consumption of energy. Two of Tesla’s most important contributions that directly led to the current infrastructure were the applications of his alternating current generators at the 1893 Chicago World’s Fair and the installation of improved designs of those generators at Niagara Falls for the world’s first hydro-electric power station—the latter also represented the simultaneous introduction of renewable energy sources before the concept was popularized. Of all of Tesla’s contributions, perhaps no other is more widely applicable in the highly technical society that has been built up around the globe than the development of wireless technology. Today, wireless routers and cell phones have become ubiquitous—a testament to the innovative prowess of an incredible innovator working well ahead of his time.

     Nikola Tesla was born in 1856 in what is now Smiljian, Croatia. His father was part of the clergy and had great expectations for his son to follow in his footsteps. “I was intended from my very birth for the clerical profession,” Tesla explains, “and this thought constantly opprest me. I longed to be an engineer but my father was inflexible” (7).3 His mother was a descendent of “one of the oldest families in the country and a line of inventors” (8). She had a profound impact on young Nikola’s perception of the world and it is likely that he picked up her trait of working relentlessly “from break of day to late at night” (8) that would reveal itself early in his studies. However, it was Tesla’s way in which he claimed he would see the world at a young age that would eventually blossom into a most fruitful output of ideas and inventions:

In my boyhood I suffered from a peculiar affliction due to the appearance of images, often accompanied by strong flashes of light, which marred the sight of real objects and interfered with my thought and action. They were pictures of things and scenes which I had really seen, never of those I imagined. When a word was spoken to me the image of the object it designated would present itself vividly to my vision and sometimes I was quite unable to distinguish whether what I saw was tangible or not. This caused me great discomfort and anxiety. (9)

Peculiar indeed! It is this method of envisioning working models in his mind that would later lead to what is one of Tesla’s most important inventions: the AC induction motor.

     Throughout his life, Tesla went through several illnesses that nearly cost his life. After recovering from such an illness while working at his first electrical engineering gig in Budapest, this ability to envision his work in full detail would unveil itself while walking in City Park with a friend. The two had been reciting poetry and just as the sun was setting, Tesla was reminded of a Geothe passage from “Faust” when he was struck with an overwhelming vision. He explains, “As I uttered these inspiring words the idea came like a flash of lightning and in an instant the truth was revealed. I drew with a stick on the sand the diagrams shown six years later in my address before the American Institute of Electrical Engineers, and my companion understood them perfectly” (40). This vision in 18824 was that of the rotating magnetic field in a brushless AC motor that would eventually be used in virtually all AC electric motors and generators. But, before examining AC design, it is important to understand DC motors and generators to see why Tesla wanted to work on a more efficient design.

     Michael Faraday outlined principles by which electric motors and generators operate in the law bearing his name, Faraday’s Law. This law states in its most basic form that, for a coil of wire, any changes in a magnetic environment will induce a current, or electromotive force (emf), in that coil of wire. The law can be written, as with virtually every other mathematical principle relating to electromagnetic phenomena, as either a differential equation or an integral equation. For the differential form, we use 𝚫𝒙𝚬 = −𝝏𝑩 / 𝝏𝒕; the integral form uses 𝑬 ⋅ 𝒅𝒔 = − 𝒅Φ / 𝒅𝒕. Generalized for multiple loops, Faraday’s Law can be summarized by Ɛ = −𝑵 𝚫𝚽 / 𝚫𝒕, where N is the number of turns or loops of the wire. This equation can be understood as a direct proportionality between the number of turns of a coil and the induced emf. That is, the more turns there are in the coil, the higher the induced emf. This is limited by several factors, however, including the stator permeability and pole piece saturation. It is also important to note that the main difference between an electric generator and an electric motor is the way in which they are wired and controlled. That is, an electric motor and an electric generator use practically the same exact components and design. So, what are they? How do they work?

     [A generator is a device that converts mechanical energy into electrical energy. (In contrast, a motor is a device that converts electrical energy into mechanical energy. This requires essentially the same design. When a motor is turned with the connections reversed, it becomes a generator.) It consists of a ferrous frame, called the stator, pole pieces, wound with wire in opposite directions, and the armature, also known as the core, which is the rotating part. The armature is made of many thin strips of an iron-silicon based material, called laminations, that are typically laser cut or die punched, then stacked together and fixed by a shaft through the center of the stack. Around the ridges of the laminations, copper wire is wound in specific patterns a specific number of times. Essentially, the number depends on the permeability of the stator, i.e. the ease with which a ferrous metal can be magnetized, as well as the saturation point of the pole pieces, i.e. the maximum flux density of the pole pieces. At one end of the armature a piece called the commutator is attached to the shaft. The commutator provides a path to extract the induced voltage as the armature rotates through the magnetic field. (This exploits Faraday’s Law.) It is made by attaching evenly alternating conductors and insulators to the shaft and connecting one end of one of the windings to one of the conductors and connecting the other end of that same winding to the conductor on the opposite side of the shaft. This process is repeated until all the opposite conductors are attached in the same manner to a single winding.
     The pole pieces are also made of high permeability ferrous material and are wound many times with thin copper wire. This winding is called the shunt field and produces the main magnetic field through which the armature spins. If self- excited, the pole windings are wired in parallel with the carbon-based brushes that contact the commutator which means that the output will vary greatly with varying speeds as well as changing load. (The brushes are made of carbon because it is very slick and resistance decreases as temperature increases.) If separately-excited, the shunt field is instead connected to a field supply with a field adjust (typically a variable resistor) and provides much better control. The strength of the shunt field depends upon something called amp-turns. Amp-turns refer to the amount of current put through a conductor coiled a specific number of times. Low currents produce low flux density while high currents produce high flux density. Saturation occurs as the output voltage tapers off when graphed with field amps on the x-axis and output voltage on the y-axis. The relationship is linear at first but tapers off as the pole pieces reach a point where the inherent molecular properties of the material, along with their limited spatial dimensions, prohibit any more field lines, and thus flux, from being produced. As loads are added to the generator, this flux tends to become distorted. This distortion is called armature reaction and is remedied by adding smaller interpoles between the main poles that are wired in series with the armature circuit.](Batenburg 2015)5. So, why did I drag you through that explanation?
     It turns out that DC currents are difficult to transfer over long distances and the problem was not unknown to experimenters at the time. The size and amount of wire required to make such a feat possible is simply impractical. Interestingly, if you graph the output voltage against time, you will see something that is essentially the absolute value of a sinusoidal function. In other words, halfway through the period of what would normally be a sine function, the value reaches 0 and instead of continuing past 0 to the negative values, it repeats the previous positive values. That is, the function looks like it is “hopping along” the time axis. This has significant ramifications; namely, the DC generator consistently reaches 0 output voltage, meaning a large portion of input energy is lost while converting to electrical energy. This is the problem that Tesla sought to remedy. How did he do it?
     By this time in the late 1880s, Thomas Edison had been well on his way to being one of the most productive and prolific inventors in the world. Paris was a bustling city that was thriving in technological updates. Tividar Puskas of the Edison organization was unveiling the incandescent lighting system in the city and Tesla was invited to attend by his brother Ferenc, for whom he worked in Budapest developing improvements for the telephone exchange there (Cawthorne 20). Tesla gained a fruitful understanding of motors and generators while working for the Edison company in Ivry and in his spare time he would solidify his AC motor designs (Cawthorne 21). After working in Germany and then traveling back to Paris, Tesla met Charles Batchelor of the Edison organization who invited Telsa to New York (Cawthorne 24). Tesla accepted the offer and arrived in New York on June 6th, 1884.
     Of Edison, Tesla remarked, “The meeting with Edison was a memorable event in my life” (Tesla 48). However, admiration would soon turn to bitter dispute over the next few years that would not wane until Edison’s death in 1931. Tesla made many improvements to designs at the Edison company and was promised $50,000 that he never received. “The Manager had promised me fifty thousand dollars on the completion of this task but it turned out to be a practical joke” (Tesla 49). He resigned shortly after and setup the Tesla Electric Company with the help of a few investors. Around this same time, George Westinghouse had begun experimenting with AC systems. Eventually, Tesla and Westinghouse joined forces at the Westinghouse Electric Company in Pittsburgh to develop more efficient AC electric systems. With that began the long, bitter feud between Tesla and Edison sometimes referred to as the War of the Currents.
     Edison was vehemently opposed to the alternating current system and eventually began public demonstrations to highlight the possible dangers of it. In fact, the controversy was accelerated in 1888 when Edison invited H.P. Brown to his laboratory “in order to electrocute animals” (Seifer 55). It wasn’t long before Brown began making and selling electric chairs to popularize a new form of execution. Due to this unfortunate series of events, investors began pulling out of Westinghouse forcing work on Tesla’s motor to be abandoned (Cawthorne 44). After traveling to Paris in 1889, Tesla returned to New York and setup a lab on Grand Street where he spent the next several years perfecting his AC motor design.
     In 1891, Tesla demonstrated the efficacy of wireless devices. His lecture that year at Columbia College before the American Institute of Electrical Engineers began, “There is no subject more captivating, more worthy of study, than nature. To understand this great mechanism, to discover the forces which are active, and the laws which govern them, is the highest aim of the intellect of man.”6 Using a Geissler tube and a high frequency alternating current through what would later be called a Tesla Coil, Tesla showed that power can be wirelessly transmitted to light the tube, stating “The experiments which will prove most suggestive and of most interest to the investigator are probably those performed with exhausted tubes. As might be anticipated, a source of such rapidly alternating potentials is capable of exciting the tubes at a considerable distance, and the light effects produced are remarkable.”7 This lecture, perhaps one of the most important ever delivered, solidified Tesla’s position in the scientific community and would have a marked influence on many in attendance. Robert Millikan later remarked, “I have done no small fraction of my research work with the aid of the principles I learned that night” (Seifer 71).

     Two years after the Columbia College lecture, Westinghouse was contracted to provide electric lighting for the Chicago World’s fair. As Seifer explains,

The Columbian exposition covered almost seven hundred acres, had sixty thousand exhibitors and cost $25 million. With 28 million attendees, the Chicago fair boasted a $2.25 million profit...

The Electricity Pavilion, adorned with a dozen elegant minarets, four of which rose 169 feet above the hall, was over two football fields in length and nearly half the measure in width. Covering three and one-half acres, this “spacious and stately” structure “befit[ted] the seat of the most novel and brilliant exhibit of the Columbian Exposition (Seifer 117-18).

     
     Tesla was exhibiting many of his AC developments in part of Westinghouse’s section. The popularity of his ideas soared and “Tesla returned to New York exhausted but exhilarated” (Seifer 121). One of Tesla’s lifelong dreams was to somehow extract the monstrous amount of energy of the mighty Niagara Falls.

How extraordinary was my life an incident may illustrate... I was fascinated by a description of Niagara Falls I had perused, and pictured in my imagination a big wheel run by the Falls. I told my uncle that I would go to America and carry out this scheme. Thirty years later I saw my ideas carried out at Niagara and marveled at the unfathomable mystery of the mind (Tesla 28).

While Tesla’s popularity was rising in 1891, the same year his patent for the “ALTERNATING ELECTRIC CURRENT GENERATOR” (See Figure 1), Mikhail Dolivo-Dobrovolsky developed a 3-phase generator and designed a system to transmit the power produced over 100 miles from Lauffen to Frankfurt.8 This would prove crucial in the attempt to transmit the power generated at Niagara Falls to Buffalo, New York. “In short, without the Lauffen-Frankfurt success, there would have been no proof that AC was capable of traversing the twenty miles from Niagara to Buffalo, let alone from Niagara to New York City, which was over three hundred miles away” (Seifer 133). By the end of 1893, having proven successful numerous times, including with the lighting of the World’s Fair that year, Westinghouse had won the contract to design and build the hydroelectric systems to be installed at Niagara Falls. Working with General Electric (GE), the Fall’s first hydroelectric power plant came online in November 1896.9

 

Figures 1 & 2 (Left & Right): Nikola Tesla’s designs included in his 1891 patent for the ALTERNATING ELECTRIC CURRENT GENERATOR.10

     Riding the wave of fortune and reveling in successful endeavors, things took a turn for the worse when, on March 13, 1895, Tesla’s laboratory on Grand Street burnt down—countless experiments and papers forever lost. It is reasonable to conceive of notes alluding to technologies that wouldn’t be realized for decades having been among the ashes. It’s hard to tell just how far ahead of his time Tesla was thinking. Of the tragedy, Charles Dana of the New York Sun had this to say:

The destruction of Nikola Tesla’s workshop, with its wonderful contents, is something more than a private calamity. It is a misfortune to the whole world. It is not any degree an exaggeration to say that the men living at this time who are more important to the human race than this young gentleman can be counted on the fingers of one hand; perhaps on the thumb of one hand (Seifer 146).

Tragic indeed! But, despite Tesla’s battle with depression, he was soon back to work further developing his concepts of wireless transmission (Seifer 147).

     In 1898, Tesla filed Patent No. 613,809, METHOD OF AND APPARATUS FOR CONTROLLING MECHANISM OF MOVING VESSELS OR VEHICLES, which detailed designs for a remote-controlled boat. Tesla explained, “The apparatus by means of which the operation of both the propelling and steering mechanisms is controlled involves, primarily, a receiving-circuit, which for reasons before stated is preferably both adjusted and rendered sensitive to the influence of waves or impulses emanating from a remote source, the adjustment being so that the period of oscillation of the circuit is either the same as that of the source or a harmonic thereof” (Tesla).11 From this inspiration, an entire wireless world has been built in little more than a century since the patent was filed.

Figure 3: An overhead view of the boat designed by Tesla and filed with his Patent No. 613809 in 1898.12

     In the mid-1890s, Gugliemo Marconi began experimenting with induction coils and other electromagnetic apparatuses—years after Tesla had developed and demonstrated wireless technology. However, in 1900, “Marconi took out Patent No. 7777, which enabled several stations to operate on different frequencies” (Cawthorne 53). It was for this work that Marconi was awarded the 1909 Nobel Prize. However, it wasn’t until after Tesla’s death in 1943 that “the US Supreme Court upheld Tesla’s patent number 645,576”, SYSTEM FOR TRANSMISSION OF ELECTRICAL ENERGY, essentially restoring to Tesla rightful credit for the discovery and initial use of radio waves (Cawthorne 181). The Bureau International des Poids et Mesures (BIPM) now defines the unit of magnetic flux density as the Tesla (T) in honor of the great “Wizard of Physics” (Seifer 121).13

     It seems reasonable to proclaim that Tesla’s influence on the modern world continues to this day. And this is certainly true in some respects. Yet, it wasn’t until I was in my 20s that I learned about him. It appears that Tesla’s work isn’t pedagogically important. Sadly, we will never know the information lost in that laboratory fire in 1895. Perhaps the reason that we aren’t presented, even in high school, with supporting material for most of Tesla’s early work is because it went up in flames. As explained earlier, Tesla’s mind worked in peculiar ways that allowed him to perfect his designs without drawing a thing. In fact, almost no one aside from Tesla believed after 5 years of construction that the power station at Niagara would function. “The outlay was huge and no one knew whether it would work as the plans lay principally in Tesla’s three- dimensional imagination. However their worries evaporated when the switch was thrown and the first power reached Buffalo at midnight on 16 November 1896” (Cawthorne 69). With the regulations that have grown up beside the infrastructure over the decades, Tesla’s rather unorthodox method of design generally wouldn’t get financial backing these days. If investors are funneling millions of dollars into a project, they expect to see fully finalized designs—not the seemingly-fantastic claims of a lone engineer, however confident that engineer may claim to be in their work. Perhaps the reason why Tesla’s experiments aren’t generally considered methodologically important is that they were too unorthodox. Then again, we typically don’t have people with such a peculiar ability for interacting visions. This raises other interesting questions, though. Of the innovators, engineers, and scientists of the past several centuries, how many can we really point to and say, “They did groundbreaking, revolutionary work that changed the world!”? 50? Maybe 100? Nowadays, people unfortunately would rather enjoy exploiting and abusing the fruits of those 50 or 100 people’s labor for selfish ends than learn how to contribute themselves. It’s a weird world right now.

     It’s a fascinating exercise to wonder how Tesla would view the modern world—the Internet, the Space Program, Lasers, cell phones, and lighting. After all, he did lay out the framework for what he called “The World System” that, in one way or another, predicts much of current, global society:

          (1) The inter-connection of the existing telegraph exchanges or offices all over the world;

           ...

6. (6)  The inter-connection and operation of all stock tickers of the world;
7. (7)  The establishment of a ‘World-System’ of musical distribution, etc.;
    ...

          (9) The world transmission of typed or handwritten characters, letters, checks, etc.; 

         (10) The establishment of a universal marine service enabling the navigators of all ships to steer                  perfectly without compass, to determine the exact location, hour and speed to prevent                          collisions and disasters, etc.; (Tesla 63-64)

It is not unreasonable to think (and perhaps I am a little biased and would simply love to hear him say it) that if Tesla were by some happenstance able to see the world today, he would be more than justified in proclaiming, “I told you so!”

     Nikola Tesla was a masterful innovator whose work will, in one way or another, continue to be foundational for our ever-increasingly technical world. My hope is that his vision to provide “free” energy to the world will eventually be realized. Our system of competitive monetary acquisition and exchange has been outdated and unnecessary for decades now and Tesla saw it coming. Unfortunately, the word “free” was not what investors like JP Morgan or George Westinghouse wanted to hear. The situation is scarcely different in 2017. It is a rather unique, potentially tumultuous time to be alive. Never in humankind’s history have we had access to so much technology. And what exactly do we do with it? We kill each other over antiquated ideas, such as money and religion—mere figments of our imaginations. Where did our empathy go? Where have our critical thinking skills and respect for the environment that sustains us go? With so much information available at our fingertips, the number of people currently lacking basic scientific knowledge in society is frightening. We have the opportunity to build up our global society into one that is sustainable, efficient, and abundant; yet, we prefer to bicker about who people want to live and be miserable with. We’d rather focus on outmoded, supposedly righteous, religiously-based conjecture that has cause more death and destruction than anything in history. How do we move beyond the supposed necessity of untenable beliefs?

     Children are capable of learning anything we teach them. We simply find excuses to not teach them the basics of physics, chemistry, calculus, biology, computer programming, and other disciplines important in the modern era, in, for example, elementary school because we might find them difficult. Well, our children are not us—they are capable of being exponentially more intelligent than us but we still fill their heads with garbage that makes us feel good. Perhaps this is because “that was the way daddy and granddaddy were raised” or whatever other primitive, selfish excuse used. Yeah? Well, compared to the amount of information available to and accessed by children nowadays, daddy and granddady weren’t very smart. We’re not even that smart! But we like to convince ourselves of it. In general, children are far more impressionable than teenagers while there is almost no comparison with adults. In other words, our future successes will be directly linked to the information we give the current generation of 5-10 year olds in these strange days. So, do we continue spreading lies and fairy tales or do we prove that we deserve stewardship of this marvelous world? Our choice at this point really is that simple. We have the information. We have the technology. We have the resources. What the hell are we waiting for?!

Endnotes

1. This timeline is available at https://en.wikipedia.org/wiki/Timeline_of_electrical_and_electronic_engineering
2. According to http://teslasciencefoundation.org/patents/, there are a confirmed 308 patents in 26 countries. “However, many patents related to the same inventions.”
3. This is taken from My Inventions and Other Writings on page 7. Tesla is lauding his father’s achievements and abilities as a multi-linguist. However, it is quite clear that Tesla wanted nothing to do with the clergy.
4. This date comes from www.teslasociety.com/biography.
5. This explanation, which is available in a much broader explanation on my blog,
   http://thehumanendeavor.blogspot.com/2015/05/acdc-revolutions.html, was compiled from notes taken in a class I had in 2013 called DC Machinery in Ohio and presented in a much longer essay for my Honors Physics II course here at CU. In the DC Machinery class, which was taught by the same professor that taught my Circuits II class, we had the design of DC Generators/Motors drilled into our heads and this is the best way I can explain my understanding. It was interesting to be able to segue into multi-faceted discussions since we were talking about both DC and AC, often comparing the two to gain deeper insight into EM applications. The reason I decided to leave it in the way I wrote it before (with minor edits—namely, the parenthetical explanations in the first paragraph) is because the more I read this explanation, the more I felt I pretty much nailed it the first time and should just quote myself in full.
   To be clear, I denoted the chosen text by indenting to express the fact that it is a quote and found that, if I were to subtract this section from the entire essay, I would still meet the 4000 word minimum. Considering the information I have provided in this section, to me it seems reasonable as long as I acknowledge as I did that I have used my own text and what text it was. In this, I feel I am being as honest as one can be. I hope that I am not mistaken!
6. The text of this lecture is available online from many sources. I used the site http://www.tfcbooks.com/tesla/1891-05-20.htm.
7. See 6.
8. This story is outline on the website
   http://www.edisontechcenter.org/LauffenFrankfurt.html.

      9. The world’s first hydroelectric power plant was built on the Fox River in Appleton, Wisconsin.            This is catalogued at http://www.americaslibrary.gov/jb/gilded/jb_gilded_hydro_1.html.

    10. In his patent, readable at https://www.google.com/patents/US447921, Tesla explains, “In the systems of distribution of electrical energy from alternating-current generators in present use the generators give ordinarily from one to three hundred alternations of [current] per second. I have recognized and demonstrated in practice that it is of great advantage, on many accounts, to employ in such systems generators capable of producing a very much greater number of alternations per second-say fifteen thousand per second or many more. To produce such a high rate of alternation, it is necessary to construct a machine with a great number of poles or polar projections; but such construction, on this account, in order to be efficient, is rendered difficult. If an armature without polar projections be used, it is not easy to obtain the necessary strength of field, mainly in consequence of the comparatively great leakage of the lines of force from pole to pole. If, on the contrary, an armature-core formed or provided with polar projections be employed, it is evident that a limit is soon reached at which the iron is not economically utilized, being incapable of following without considerable loss the rapid reversals of polarity. To obviate these and other difficulties, I have devised a form of machine embodying the following general features of construction.”

     11. The text of the patent wasn’t available on the US Patent Office website but I did find it at

https://www.google.com/patents/US613809?dq=patent+613,809&hl=en&sa=X&ved=0a

hUKEwjsxZyvns7TAhVX42MKHRHlBqQQ6AEIJzAA.

12. See 11.
13. This reference is from the introductory speech for Tesla at the 1893 Chicago World’s Fair by Elisha Gray.

References

Cawthorne, Nigel. Tesla: The Life and Times of An Electric Messiah. Chartwell Books, 2014.

Print.

Seifer, Marc J. The Life and Times of Nikola Tesla: Biography of a Genius. Secaucus: Carol

Publishing Group, 1999. Print.

Tesla, Nikola. My Inventions and Other Writings. New York: Penguin Group, 2011. Print. Tesla, Nikola. US Patent 447921 A. United States Patent Office, 1891. Grant.

Tesla, Nikola. US Patent 613809 A. United States Patent Office, 1898. Grant.

Tesla, Nikola. US Patent 649621 A. United States Patent Office, 1900. Grant. 

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