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It’s the height of summer, July 18th, 1878, in the railroad town of Rawlins. The outpost sits on a plateau in the Wyoming Territory, nearly 7,000 feet up. About 800 people call it home, and most work for, or support, the Union Pacific Railroad.
Right after midnight, a train pulls into the station. This one is carrying some notable travelers, all the way from the East Coast. They are here for the clear skies of the frontier.
Leading the party is Dr. Henry Draper.
He’s an eminent New York physician and pioneering astrophotographer. He organized this Western expedition, and he brings nearly a ton of equipment — telescopes, spectroscopes, glass photographic plates, and crates of photographic chemicals.
Beside him stands a 31-year-old man. He’s a young, ambitious Thomas Edison.
Draper invited Edison to leave his Menlo Park laboratory behind and join the expedition west, where he could test his newest, unproven invention. It’s a hypersensitive heat detector called a tasimeter.
Fresh off inventing the phonograph, Edison is already a global celebrity. That fame, however, can sometimes bring forth the craziest of characters and fans — including one waiting for him in Rawlins.
You see, the town has just one hotel, and it is overflowing with scientists, astronomers, reporters, and curious onlookers. Edison finds himself sharing a cramped room with Edwin Marshall Fox, a correspondent for the New York Herald.
Their first night on the frontier is anything but restful.
Late that evening, long after the two men turn in, a loud knock occurs at the door.
When the door opens, a tall stranger steps inside. Long hair to his shoulders. Buckskin and boots. Bloodshot eyes and whiskey on his breath. He walks right into the room and stands before the two startled Easterners. They wonder who he is and what he wants.
It is Texas Jack Omohundro. Frontier scout. Showman. By his own account, the boss pistol-shot of the West! He has read about Edison in the papers and he wants to meet the Wizard of Menlo Park.
To prove exactly who he is, Jack draws his Colt revolver and aims across the street at the freight depot. He fires straight through Edison’s hotel window and hits the weather vane on the depot roof.
Edison would later recall: “The shot awakened all the people, and they rushed in to see who was killed. It was only after I told him I was tired and would see him in the morning that he left. Both Fox and I were so nervous we didn’t sleep any that night.”
Welcome to the Wild West, Mr. Edison.
Somewhere in that same overcrowded hotel, another quest is unfolding.
Enter James Craig Watson. Professor of astronomy at the University of Michigan and Director of the Detroit Observatory. He’s one of the world’s most famous planet hunters, with more than twenty asteroids already to his name.
He’s here to find Vulcan.
For decades, astronomers have witnessed a problem with the planet Mercury. Its orbit shifts, slightly, every time around the Sun. Under Newton’s laws, that shouldn’t happen. Unless something is out there. Something hidden, closer to the Sun, tugging as it goes.
Theorists gave that hidden world the name Vulcan before anyone ever saw it. They believe it’s close to the Sun, drowned out by daytime glare. The only chance to find it is during an eclipse.
And Watson has come to claim it.
Now, nearly two hundred miles to the south, another train cuts through the prairie heat of Colorado. Colorado is a brand-new state, just two years into the Union. And the entire Rocky Mountain region is in the grip of a strange migration.
A total solar eclipse is coming, sweeping down from Montana to Texas. Trains arrive daily, packed with tourists and rival scientists. In Colorado Springs, one enterprising owner even rents out his livery stables. He puts eclipse tourists in the stalls instead of horses. On the street corners, newsboys shout:
“Here’s your colored glass for seeing the eclipse! Genuine French imported Mazarin Blue! London smoke and bottle green! Three kinds, three cents each, or two for five!”
In Denver, another party steps onto the platform. At the helm: Maria Mitchell — America’s most famous female scientist.
She teaches astronomy at Vassar College, in an era when the male scientific establishment insists higher education endangers a woman’s health, and when the federal government won’t fund female researchers.
Raising her own funds, she brings five of her brightest graduates and a haul of heavy telescopes.
She is here for the science and to settle an argument that women can hold their own in the sciences.
So we have Edison, chasing proof of his own genius. Watson, chasing a planet that may not even exist. And Mitchell, chasing the collapse of a prejudice built to keep her out.
The days leading up to July 29th become a race against the clock. Every camp is busy preparing.
Down in Denver, Maria Mitchell and her Vassar graduates turn their campsite into a masterclass in discipline. They choose a hill at the edge of town. They set up wooden chairs, a small tent for shade, and telescopes mounted on tall tripods, including a four-inch Alvan Clark scope that Mitchell owns. It is the same instrument she was using in 1847, the night she found a comet that made her famous.
A hundred miles south, on the summit of Pikes Peak, conditions are brutal. Fourteen thousand feet up, Samuel P. Langley and his team fight off freezing weather. To keep his telescope from rusting, Langley coats the steel in animal lard.
With almost no level ground among the jagged granite boulders, the men sleep beneath canvas stretched over makeshift beds of logs, hay, and damp blankets. Cleveland Abbe — the country’s leading government weather forecaster — gets altitude sickness, and it gets bad enough that the others fear for his life. They carry him down the mountain on a stretcher.
And at night, the cold gets worse.
Wind hammers the canvas. Snow blows into the tent. Langley later remembers waking to find a deep snowdrift piled against his pillow. The scientists who remain fight off the conditions and wait for the clouds to break.
Now, back up in Rawlins, Thomas Edison runs headlong into the Wyoming wind.
Gale-force gusts sweep through the camp. When Edison tries to work outside, the wind shakes his equipment. His tasimeter is far too delicate for this. It’s designed to detect small changes in heat, and out here, every vibration sends the instrument out of adjustment.
He needs shelter. But Rawlins is already overflowing with visiting astronomers, and Edison ends up with an unlikely observatory — a crude chicken coop.
He hauls his equipment inside and sets up near the doorway.
Nearby, James Craig Watson, in his hunt for Vulcan, takes a completely different approach. He packs up his telescope and moves out of town altogether, just a dozen or so miles down the Union Pacific line, setting up camp at a lonely rail stop with a name you couldn’t invent: It’s called Separation.
There he finds a low, curving sand dune, and he sets up in its shelter. He is joined by another late arrival — Simon Newcomb of the Naval Observatory, soon to be the most famous astronomer in America.
Watson stands beside his telescope, ignoring the wind, the crowds, the cold. He has spent weeks memorizing the stars that will surround the Sun at totality. He checks his pocket watch. The instant the sky goes black, he will be ready.
Then, on the afternoon of July 29th, the countdown expires.
It’s 2:13 p.m., and the Moon begins to bite into the Sun.
Over the next hour, the daylight decays into twilight and the temperature drops.
At five past three, the Sun is almost fully covered.
Outside Edison’s shack, the local hens look up and decide the workday is over.
The problem, of course, is that America’s most celebrated inventor is squatting in their bedroom.
Then… totality arrives!
Étienne Léopold Trouvelot. Public Domain.
Around the Moon’s black circle, the solar corona appears.
In the final minute of totality, Edison swings his telescope into line and pulls the protective screen, focusing the corona’s light into his heat detector.
The tasimeter reacts instantly. A tiny beam of light leaps across the measurement scale. It races to the right, gathers speed, and in five seconds flies clean off the edge of the scale.
Edison is thrilled, convinced his device has caught the immense radiant heat of the corona. He works fast, twisting the balancing screws to pull the beam back into range and take a reading he can actually verify. But in the darkness of the chicken coop, the seconds bleed away.
Now, out at Separation, James Craig Watson is glued to his eyepiece looking for Vulcan. He sweeps his telescope across the darkened sky, working the region near the Sun.
Then his eye catches something.
A faint point of light, close to the Sun, sitting where no star should be. He has memorized this patch of sky. Nothing belongs there.
He fixes the position and holds it in his head.
He believes he has found Vulcan.
Back down on the hill outside Denver, Maria Mitchell’s party works quickly. She strips the dark filter off her eyepiece, swaps in clear white glass, and goes to work studying the corona — its shape, its color, and whether it looks like a substance or is it just light coming off the sun.
One of the graduates, a young woman from California — counts the seconds aloud. Her voice is the only one on the hill.
Nobody looks up from an instrument until it is finished.
Further south, high atop Pikes Peak, Samuel Langley drops his gaze from the telescope and takes it in with his naked eye. He begins sketching that same strange, extended light — a vast structure reaching millions of miles into space.
Then, the darkness over the earth begins to recede.
Totality is over.
Almost instantly, communications flood the telegraph wires. Operators tap out bulletins to Chicago, New York, and London. Watson wires the world that the lost world of Vulcan has finally been discovered. The papers celebrate Maria Mitchell’s expedition. And Edison, emerging from his chicken coop, tells reporters his tasimeter has officially registered the heat of the Sun’s crown.
In the weeks that followed, the verdicts came in. They did not match the ambitions people had carried west.
Henry Draper’s photographs of the corona were a real achievement, but Edison’s tasimeter was not. He had initially thought that the device measured the heat of the sun’s corona. Astronomers soon realized it measured nothing of the kind. The instrument had never been calibrated. What it actually recorded was vibration, warm brass expanding in the telescope tube, and Wyoming winds. Edison eventually abandoned his tasimeter. But don’t feel too sorry for Edison. He found his historic breakthrough the following year, in a very different application of carbon and current—that being the lightbulb.
For a while, Watson’s Vulcan made headlines worldwide. Other astronomers, including a rival named Lewis Swift, also claimed to have spotted the phantom world. But nobody could confirm it, and nobody could ever find it again. Most astronomers now believe the two men saw known stars.
Watson spent the rest of his short life chasing Vulcan. He died in 1880, not yet forty-two, the planet still unproven. It would take another thinker entirely — that being Albert Einstein. In 1915, Einstein’s general relativity accounted for Mercury’s wobble. Vulcan had never existed at all.
Maria Mitchell left Denver with exactly what she came for. Her observations were precise. Her team’s execution was flawless. And the record showed what she came to show — that science has never belonged to one half of the population.
Our story has lived in the American West because that is where the reporters and the rivalries gathered. But many outside the U.S. saw the eclipse. It first touched eastern Siberia, crossed the Bering Strait, swept down the spine of the Rockies, crossed Texas and the Gulf, and finally dissolved over the Caribbean.
Before the event, the U.S. Naval Observatory — the nation’s official astronomy office — asked everyday citizens to sketch what they saw and mail the drawings back to Washington. Many of those drawings are still in the archives. You could call it “citizen science” long before the phrase existed.
Sources and Further Reading
Baron, D. (2017). American eclipse: A nation’s race to catch the shadow of the moon and win the glory of the world. Liveright Publishing.
Cheyenne Weekly Leader Telegraph. (1878, August 1). Scientific observers: Reports from the Wyoming delegations—Prof. Watson’s great discovery—Interesting details. Cheyenne Weekly Leader Telegraph, 1. Wyoming State Archives.
Draper, H. (1878, July 29). The eclipse as observed at Rawlins, Wyoming—Favorable weather and complete success—The character of the corona determined—Edison’s tasimeter measures the heat from the corona. The New York Herald.
Draper, H. (1878). The total solar eclipse of July 29th, 1878. American Journal of Science and Arts, 16(95), 227–230.
Edison, T. A. (1878). Report of Dr. Thomas A. Edison to Dr. Henry Draper on the tasimeter observations at Rawlins, Wyoming Territory, July 29, 1878. National Archives and Records Administration.
Frederick-Frost, K. (2017, August 16). Donkeys, lard, and a telescope: Eclipse exploration in 1878 and 1900. National Museum of American History, Smithsonian Institution. https://americanhistory.si.edu/blog/eclipse-exploration
Grundhauser, E. (2024, March 11). How the 1878 eclipse almost killed the father of American meteorology[cite: 7]. Atlas Obscura[cite: 7]. https://www.atlasobscura.com/articles/how-the-1878-eclipse-almost-killed-cleveland-abbe
Hallberg, C. (n.d.). Scientific findings from the 1878 total solar eclipse. Wyoming State Archives.
Langley, S. P. (1878). Observations at Pike’s Peak, Colorado, during the total solar eclipse of July 29, 1878. U.S. Government Printing Office.
Nadan, T. (2017, August 18). Turn around, bright eyes: Henry Draper and the 1878 eclipse[cite: 23]. The New York Public Library[cite: 23]. https://www.nypl.org/blog/2017/08/18/henry-draper-1878-eclipse
Todd, M. L. (1894). Total eclipses of the sun[cite: 25]. Roberts Brothers[cite: 25].
Trouvelot, É. L. (1878). Total eclipse of the sun: Observed July 29, 1878, at Creston, Wyoming Territory [Lithograph]. The Miriam and Ira D. Wallach Division of Art, Prints and Photographs, The New York Public Library.