Good evening everyone. Thanks for coming. Uh, I'm here to talk about 19th century eclipse expeditions and the forging of mathematical community. A total, a total solar eclipse brings a certain transcendent awe, a special kind of wonder. This rare celestial event happens when seasons and orbits align for the moon to pass between the earth and the sun temporarily obscuring the full wattage, leaving visible, only the spectacular solar corona. This phenomena comes with a chilly wind and an eerie hush. And just for a few minutes, it's safe to take off your eclipse glasses and take in as much as you can to sort of gape at the awe of this spell binding site. It's an incredible experience, uh, not remotely captured by looking, looking at a photograph, uh, something I absolutely recommend if you have an opportunity and if you are in North America or will be six months. Hence, uh, you have a tremendous opportunity to put yourself in the past of eclipse totality. So just a travel tip for you there. I first experienced eclipse totality in August of 2017. Uh, it changed my life in many ways. I had no idea at that time either that Eclipse Expeditions would be almost as relevant to my own work and experience of professional community as it was for 19th century mathematical practitioners. There's a particular connective power of experiencing a total solar eclipse, something some authors say that connect us to the past and the present and the future. Uh, and there there is a way in which, in fact, this experience does feel transportive both to, to the past, particularly given my, uh, sort of scholarly interest and the connection to modern, astronomical and mathematical community. Still, my story today begins with a decided lack of community. Uh, I'm gonna start in 1840, and I'm gonna start in the United States, in particular in Cambridge, Massachusetts, where this guy, Benjamin per, was a professor of mathematics at Harvard. It was a time when technical, mathematical and scientific training was rare in the United States, and the educated elite was skeptical about science as a profession. There was no, well-formed identity, even for an American scientist, much less an American mathematician, which is what he was per, nonetheless, had massive ambitions to develop and showcase American mathematical talent. He went about this in lots of ways, but his effort to start the first research mathematical publication in the United States failed within a year. There were only about 360 mathematical practitioners in the country. Most of those had been trained in law or theology, um, worked at rural colleges or high schools, and there simply wasn't a community substantial enough to sustain a research level mathematical publication in the four measly journals. Uh, the measly issues of this journal, he had nonetheless set forth a vision. He had published a manifesto about how mathematical astronomy was going to be the way for American science to establish itself internationally. So that was, that was his plan, and he had a big chance in 1846. So this is an image, a beautiful image, uh, of the planet, Neptune. And that's the, the planet that was first observed in 1846. There was a huge international priority controversy surrounding that discovery, and that's exactly what provided an opportunity for per and his fellow Americans to stake a claim for national mathematical practitioners in the US on the global stage, it's a big drama of astronomical rivalry. There's controversy between Britain and France and the US comes sailing in on the tail end of things. So we only have a tiny bit of that story for you today, but it's a, it's a riveting tale, and it starts in 1781 with, we've already seen this image today earlier of Caroline Herschel and her brother, and they're the two who observed this new planet Uranus. And once you observe a new planet, the first thing you wanna do is to compute its orbit. And so this happened, they computed the orbit and then watched what happened. And what happened was that the planet Uranus began to deviate pretty dramatically from where astronomers expected it to go. And as the planet went further and further, apparently off track, astronomers puzzled over the explanation what could possibly be causing this. And John Cooch Adams, who was kind of a young upstart, recently graduated from Cambridge University. He was a senior Wrangler, which meant he had scored the best on the mathematics, uh, trip posts. He won the Smith Prize. He was kind of the, the top of the heap of undergraduates at Cambridge. Uh, but that was nothing compared to Laer, who was an established French astronomer. He had done extensive study of emotion of mercury, uh, and these two independently predicted the existence of a never before scene planet that could split, oh, a never before seen planet that could explain the apparent disruption of the orbit of Uranus. So this is Uranus, it's going off track. And they, both Lavere and Adams, they used Newton's gravitational theory, right, developed in the wake of the calculus and Kepler's law as a planetary motion to predict the mass and position of this hypothetical body. And the new planet was finally observed from an observatory in Berlin of all places. And when that happened, the scientific administrators in both France and in Britain, they felt robbed. They thought, we have the people who predicted this, we should get the credit you can. It's understandable. But the squabble that ensued meant that Benjamin per had an opportunity, and he and the Americans quickly calculated the orbit of Neptune to salvage some scrap of the success, the glory of planetary discovery. But in this whole story, the biggest winner actually turns out to be Newton's theory of gravitation by mathematics alone. A new planet had been predicted to exist without ever having been seen. And then it was discovered, this raised tantalizing questions about what other big questions mathematics might be able to solve. And in particular, this problem. So there was an unexplained shift that had been observed in the orbit of Mercury, something that gets called the procession of the parhelion of Mercury, if you want to be fancy about it. But there's just a, a sort of a shift that's happening as Mercury gets close to the sun in its orbit, orbital path. Liber had thought a lot about this. He thought a lot about the motion of Mercury. And after this triumph, this triumphant discovery of Neptune, his prediction of Neptune by mathematics, Liberi thought maybe, maybe the same trick will work again. Is it possible that there's another new planet out there that's causing this disruption to the orbit of mercury? Maybe this is possible. And so excitement ran high. This is a, a beautiful image of mercury. It doesn't really look like that. This <laugh> just seems exciting because it's an exciting question. Uh, but this is a, an overlay of data from a spectrometer along with, um, the NASA Messenger spacecraft. So it doesn't actually look like that if you go up to space. It's just a picture I really like of Mercury. So the question is, is there another new planet out there that can solve this mystery? Is there something else that's disrupting the orbit of mercury? So excitement ran high. You can imagine we found one new planet, maybe there's another new planet. They gave it a name. It's called what's called Vulcan, and people sent out to look for it. But one challenge, if you're looking for something that's near the sun, is that much like being in front of the lights up here. The sun is bright and it's difficult to see things very close to the sun, but astronomers knew it would be easiest to observe in the area, the vicinity of the sun during those precious few minutes of a total solar eclipse. And so this became one of the outstanding scientific questions pursued by eclipse expeditioners in the second half of the 19th century. Is there some unknown planet between mercury and the sun? So this is one question on the table for Eclipse expeditions in the second half of the 19th century. They also want to test models of the motion of the moon. The the moon's motion is sort of notoriously tricky to describe among astronomers. And lunar theory also relates to navigational accuracy by this point, and therefore is connected to national concerns, military trade commerce, right, things national governments are concerned about. And in 1849, the United States Naval Appropriations Act, a congressional act, authorized an official American Almanac because the Americans wanted to avoid dependence on foreign sources for astronomical data. This was part of the plan to establish independent science of a kind of international level in the United States. And in 1851, they had a chance to check how well their work was going. There was a solar eclipse on the 28th of July, and it brought triumphant vindication, the US nautical almanac offices'. New tables of the moon's positions were significantly more accurate than those of its British counterpart. They were thrilled. The the Britts, based on all the material that I've seen, do not seem to have cared at all. But the, the same year, the Americans are celebrating the triumph of their lunar table. There is another huge milestone for astronomical observation, and that is the developing technology of photography. So we heard a little bit about this earlier. This is a huge change in astronomy in the, over the course of the 19th century. The first photograph of the moon had been displayed in New York City in 1840, but if you wanna take a picture of the sun, your shutter needs to be significantly faster than to take a picture of the moon. And such a shutter was developed in 1845. And this paved the way for this photograph here by Johan Bofski, the first photograph of the solar Corona taken during Eclipse totality in Konigsberg in July of 1851. And with the success kicked off a new debate, could photography become a reliable, astronomical tool? Right? Spoiler, I just showed you some NASA photos. The answer is yes, but they didn't. This was up for debate in, in the 19th century and the golden age of eclipse, eclipse expeditions, which is what the second half of the 19th century gets called if you're into eclipses, Brought many opportunities to find out. So there was a new mathematical approach to calculating the path of eclipse totality. This was determined by vessel in 1824. It's what still gets used to eclipse, to compute the path of totality today. And what it meant was that astronomers had plenty of time, they had a lot of advanced notice to plan and organize eclipse expeditions and how they would get themselves and their prodigious amount of equipment to the zone of totality. They could now predict specific locations on the globe where you would need to be to experience totality, well in advance of the event. And mid-century astronomers were especially keen to use their eclipse expeditions to as practice to observe an even rarer predictable occurrence. So you can see this sort of cluster of eclipses over there, 68, 69, 70, and 71. That's four eclipses, which are all accessible in accessible locations. So the ones, um, highlighted in, in green. There are, um, well, not in Antarctica or anywhere else, that's extremely difficult to reach. So these were eclipses that, um, astronomers were fairly confident they could reach the zones of to totality. And that particular clump of four there were of special interest because they wanted to practice up for the transit of Venus. So the transitive Venus happens even less frequently than a total solar eclipse. Venus passes between the sun and the earth twice, eight years apart, about every 125 years. And from the earth it's possible to watch Venus Transit the sun, as in as beautiful image from the 2012 transit of Venus. So you can see this tiny little black dot up there, that's Venus, and it's traversing across the surface of the sun as seen from Earth. This has only been observed seven times, first in 1639, and most recently in 2004 and 2012. So I'm sorry to tell you, it won't happen again until 2117. But for 19th century scientists, timing the phases of Venus. So in other words, when does Venus make first contact with the boundary of the sun? And when does it go off the edge of the other side of the sun? When has it completed the transit In 1874 and 1882 is when the, the key transitive Venus are scheduled to happen, or would provide essential data for determining the distance between the sun and the earth. So what they hope to do, astronomers wanted to answer one of the great basic science open questions of the time. How big is the solar system? And this piece of data, this timing, they were gonna use solar paragraphs and determine the size of the astronomical unit. And this run of accessible eclipses, 18 68, 69, 70, 71, leading up to 1874, gave them invaluable practice with observational tools and techniques for even higher stakes astronomy. So as exciting as an eclipse is, if what you're really after is the transit of Venus, it's a warm act, warmup act, right? And so I'm gonna talk about a few of these eclipse expeditions, and I wanna start with 1860. So this is a nice picture from Harper's Weekly, and it gives you a sense of the level of interest surrounding some of these events. There was wide newspaper coverage around the world, in fact, um, and it's sort of a general interest in what might come of these eclipse expeditions. And I wanna focus in 1860 on particularly the American observations in 1860. So just a word about what the United States looked like at that point. So what's in orange? Here are states. So it's just, whoops, I've gone off mic. Am I, it's just after the gold rush. Uh, so California has recently become quite populated due to the Gold Rush. It's recently become a state. Uh, and you can see that in between sort of Ohio, Missouri, Texas, and so on. There's this kind of vast blue zone, blue and green. Those are territories at that point. So not part of the official United States of America. Uh, however, there is an enormous amount of activity going on there, not all of which is, uh, commendable. Uh, so there just a note about the context of those territories. There is, um, decimation of indigenous populations that's happening, uh, at, at exactly this point in time in the United States. And as the nation is taking shape in a way, quite literally, you can see, but also in terms of its institutions and um, kind of governmental bodies, there is increasing interest in solar, ex solar eclipse observations. And in 1860, they think this is a great, this is great for us. We don't have to go very far. Totality is going to come to us. And so there, there are three US Eclipse observing parties that attempt to, I will say that attempt to make observations in 1860. Uh, the first one is the US Navy Lieutenant. His name is James Gillis. He took a few boxes of kind of second rate equipment, leftover stuff he could borrow from anybody. He would give him a telescope, a chronometer, you know, he was writing letters to various places. Hey, do you have anything I can take? I'm going to go to Oregon to observe the eclipse. And everybody said, Oregon, it's always cloudy in Oregon, so nobody would give him a camera. So James Gillis did not have a camera, but he took telescopes and kilometers, and he took a steamer from New York over here, all the way down around and up to San Francisco where he picked up his son. He was working on the Coast survey. Uh, it took three weeks on a steamer, and then they traveled another two weeks to reach that red star on the left side of the map and a camp near the Cascade Mountains and Wonder of Wonders. They had a clear view of the Corona. Uh, they did not have a camera, however, uh, but the other thing, and this is a very, very relatable sentiment from Jane Gillis. He found the sunrise eclipse so spectacular. And this is his quote, I was irresistibly drawn to its contemplation, and he neglected his scientific observations, <laugh>. So he had a kind of recollection that he reported after the fact of what he had seen, but didn't have any kind of scientific data. And this is certainly a relatable sentiment, I think, for anyone who's experienced eclipse totality. And it is also a great reason why Eclipse expeditions always wanted experienced observers. So there's this sort of collection of people who sort of recur on these eclipse strips because, well, they, they know a little bit what what they're in for. And that in fact was the best of the outcomes for these three American parties in 1860. Uh, the second in the middle of the map there, the Red star up by the Saskatchewan River was a, a party of four. It took them 47 days to get there. It is a terrible slog. The the travel log that they write about this trip is, it sounds miserable. There were clouds of mosquitoes. The stagecoach got stuck in the mud, they had to switch to a wagon, and then they were in a canoe, and the canoe was leaking, and they spent the night in the mud. It, it just was a terrible slog to get there to Northern Saskatchewan. And on Eclipse Day, they sat in a marsh and watched clouds obscure the corona, nothing for them. And then they made it a, the long trudge back home again. The third group up there on the top of the slide was a team of 11. They had managed to borrow a steam ship from the Coast Survey, not the Coast surveys, best steam ship, right? Kind of a leftover one that was parked in the back. And they had to navigate through ice fields, through snow, through coastal mist. They about ran out of fuel. They thought they were gonna get stuck, uh, and they make themselves make their way up to Avik Island. And there also clouds. Only one person saw any part of the Corona and that person, they had left on the boat with no equipment. So again, nothing. And that itself would be sufficiently disappointing. However, it's more disappointing when your competition has a great day and an ocean away. The Royal Society fellow Warren LaRue had the help of the British Navy behind him, and he had a new railroad across northern Spain that reached the zone of totality. And because of these advantages, he was able to transport this purpose-built Q Photo Helio graft. So just for context, uh, this instrument weighs about 400 kilograms. It's about eight feet tall. It's a massive instrument. And if you're going to use this instrument to take a photograph of the sun, you need to have also a photographic darkroom with you, with glass bottles full of toxic chemicals and glass plates and somewhere to develop it all. So this is not a small enterprise to schlep all this stuff, even if you have the British Navy and a railroad across northern Spain, it's going to take some doing to get all of this to the zone of totality. But he does this, and he, given all of that investment in getting this equipment and all of the supplies to the zone of totality, he takes an epic risk. He gambles on a new kind of photo photography, the, a wet collodion technique, which is a risky new technique, but it has the potential to capture much finer detail than the existing standard methods. And it worked. And Warren UE gets this photograph, the sensational photograph. It winds up reproduced in newspapers around the world, in particular in the New York Times, where it is described as a photograph of with rosy flames. And this made headlines around the world. So you can see the, the detail here of the, the prominences coming off the solar Corona. It's a really a spectacular image. And this British success of, of course, you can imagine only compounded the sense of disappointment amongst American astronomers in 1860. It happened here, it happened in North America. We didn't, it didn't, we didn't get anything. So they resolved to take full advantage when Eclipse totality, again, returns to North America in 1869. And planning started in 1867. And this coincides with two things. It coincides with Benjamin Perce becoming the superintendent of the United States Coast Survey. So Benjamin, per of our, we previously encountered of our ambitions of putting American mathematical sciences on the global stage, and also in 1867 is the transfer of Alaska, which means that the United States is going to immediately start mapping Alaska, sort of related to their, the re recent acquisition, but also related to this eclipse opportunity. So in 1869, the situation in the US is somewhat different than in 1860. It's after the Civil War reconstruction is largely underway. Infrastructure has been rebuilt and expanded. There are new railroads. 1869 is the date of the completion of the transatlantic, the Transcontinental Railroad. Uh, there's also a telegraph service going crisscrossing the country. And the railroads then will facilitate the transportation of bulky observational equipment and dark rooms for developing any photographs you might get. And the telegraph lines meant that surveyors could determine longitude for the observers. So you need to know where exactly are the bounds of totality so you can make sure to get all of your astronomers in the zone where they've got a chance. Anyway, to see totality. This is a map, uh, that was in the New York Times. And you can see that the zone of totality is going across the entire continent, right? It's going from Alaska up here on the left, all the way down across and off the coast of South Carolina. And so newly in charge of the Coast Survey responsible for governmental mapping and exploration, Benjamin per promptly sent surveyors to Alaska. So his, his vision is to have observers across the zone of totality, right? They all know what happened happened last time we got stuck by clouds. So if you have somebody everywhere, then you can maybe minimize the risk of catastrophe in the case of cloud cover in some place. So this is, this is a landscape over which they want to get inland from the coast to the zone of totality. And again, just as a reminder, they have a lot of finicky, astronomical observational equipment that they wanna take with them. So it's a little bit, it's a little bit precarious, and they enlisted some help. This is a kind of incredible story. They enlist, enlisted some help from Chika sling Chief Klux, and he and his wives drew this map of ancestral trade routes that turned out to be the key for the US Coast Survey personnel to observing the eclipse in Alaska. It's the oldest known map of southwest Yukon. It's drawn in pencil and it shows trade routes and landmarks. Uh, there's some interesting work being done on this to do with indigenous place names and stretching hundreds of kilometers inland from the, the village of Kwan traversing traditional territory of several of the first nations. And this, there was, um, big celebrations of this map in 2019 on the hundred and 50th anniversary of, well, these eclipse observations, but also the, the drawing of this map. It's, uh, quite a, quite a significant cultural object. So meanwhile, the Americans are making plans. They're trying to figure out how to access as much as possible of the zone of totality. And meanwhile, there is another path of totality in 1868 that is crossing the Indian subcontinent. There aren't any Americans who plan to go. There was one who was invited, but it didn't, didn't work out. But in 1868, in the zone of totality here, European astronomers again made huge news. The Royal Astronomical Society had sent John Herschel to jam Condi India with this single prism spectroscope to study the chemical composition of the solar Corona so that nobody had tried this. The Spectroscope is a new item. And the, the thought of using this training, the spectroscope on the solar Corona is a new plan. Uh, the, the French astronomer we heard about earlier, uh, Johnson made similar observations, um, for both of them. The spectrum of the Chromophore show showed an unfamiliar line near the sodium d that's this one here, and this turned out to be helium. They detected a new element in 1868 in the solar Corona. This would not be isolated on Earth until 1895. So this is huge news. We found a new element, and this raised, again, more new questions. It raised questions about the chemical composition of the solar Corona. And this added some new things to the US observer's eclipse observation to-Do list for 1869. We're looking for an incur planet. We wanna find out about the, the composition of the solar Corona. We wanna be able to time the eclipse phases so that we can gear up for the transit of Venus. So, and we also, we wanna take a lot of photographs. They're really interested in photographs. And Charles Augustus Young, who had recently become a professor of natural philosophy and astronomy at Dartmouth, following his Civil War service, he immediately took up spectroscopy. And this became a research trajectory that would make him, by the end of the century, one of America's most significant astronomers. And he developed a new style of spectroscope in hopes of more effectively identifying elements in the Corona. So there's a real sense of opportunity for exploration and discovery, right? No one's quite sure how these spectral analyses of the Corona, how they're working, how you could improve them. So astronomers in various places are experimenting with all kinds of different, all kinds of different approaches per is overseeing the US preparations for eclipse observations in 1869. And they're taking this seriously. The stars on the map are where there are observers who reported into the US Coast survey reports. So they really don't want to miss it. And in Percy's words, he said, it's nothing less than a duty owing to civilization that everything in our power and within our means should be done to make the observations as complete as possible. So again, visually displayed here in this map. Now, the available means, it's kind of interesting to think about. They got $5,000 out of Congress in a kind of unconventional move. So that's a current economy cost of just over $17 million out of Congress. And they also had the rail companies who donated the excess of $2,000 of free travel for astronomers who were going from the East coast into the, the band of totality. Uh, there's a great story about an amateur photographic society in Philadelphia who had a custom outfitted train car to transport all of their, uh, photographic equipment and their jars of chemicals in their darkroom. And the, the railroad company wanted to support the cause of science, so they made a special train car for them. So there's, there's all kinds of amazing stories of this nature of what people did to practice their photographic techniques. You, you don't have a lot of time, right? You're not using your iPhone. You have to, you have to expose things that takes time. You need a plan and to practice your plan if you wanna get a good photograph. And you only have about two minutes of totality to, to make that happen. So there are lots of amateurs, there are astronomers from various, uh, universities in the us various colleges, and there are also a vast numbers of Coast survey employees. So Benjamin Purse, again, in charge of the Coast survey, the coasts survey has a total budget of about half a million dollars for the year. And that covers equipment and survey personnel in the zone of totality. Just by way of perspective, about 35% of the coast survey report for that year is about the eclipse. So they're, they've got a lot of other things they're supposed to be doing, right? They're mapping the entire country, uh, but 35% of that year, they're, they're focused on the eclipse. So just to give you an idea of sort of the conditions. So this is a temporary observatory that was built in Burlington, Iowa. This is an easy train journey then and now from Chicago, Illinois. And it was the destination for thousands, thousands of eclipse watchers. Uh, this photo shows a very posed scientific party. Uh, the group includes, you can see down here, uh, with the parisel and the black dress. It's Mariah Mitchell. She was, um, astronomy faculty at Vassar College, which is a, a women's college. And some of her female students are there as well. And their, their scientific visit created quite sensation in the local newspapers. Uh, Charles Young was also in Burlington. He's in this photograph as well over there with this spectroscope. So you can see this looks very different from the one that John Herschel took to India. Uh, he's trying to innovate here. He designed and built this himself, and he's successfully captured the green Corona line, K 1474. It's the one there on the far right. And this was first thought to be another new element. So there was kind of immediate sense of triumph. We found another new element, they named it Coron after being in the, in the, in the solar Corona. Uh, it was a subject of debate for a number of years, um, but early in the 20th century was determined to be highly ionized iron. So not a new element, but nonetheless, uh, exciting to have found, uh, to have found something I so nearby in Des Moines, Iowa. So a couple hundred, so miles further inland, uh, the furthest west in the band of totality that was accessible by the railroad. So that's a kind of key piece of information. Uh, there was Simon Newcombe. So he was one of the four that was stranded in a soggy canoe in 1860, uh, stuck up in the Saskatchewan River. And he, I'm sorry to say, was also disappointed in 1869 because what he wanted to do in 1869 was to find the inial planet. So he observed eclipse totality. This is his diary entry from Eclipse Day. And he writes how he was disappointed as he would be understandably not to find the inial planet. But overall, the eclipse observations in 1869 were viewed as a tremendous success. The, the effort of the American astronomers produced photographs, hundreds of photographs and observational data, pages and pages and pages and pages of so much data about the weather <laugh>, about the birds, about the observations, lots of data, and also it excited, tremendous popular interest. Newspapers from San Francisco to New Hampshire described the, the sort of flaming corona and the airiness of impending totality in parts of the country that would not have had any part of the path of totality. Thousands of people witnessed at least a partial eclipse as far east as Boston and as far west as California. This level of interest led to an increase in governmental funding, particularly earmarked to supply astronomers for future scientific expeditions. So kind of a win for the astronomers there. One other, perhaps more surprising outcome of the Eclipse expedition is the beginning of this, the annals of mathematics. If we have any mathematicians in the room, you'll recognize this as one of the most prominent, highest ranked journals in mathematics currently. And this publication, this prestigious publication had its start in the unlikeliest of places in Des Moines, Iowa. And its first couple of issues looked like this. And you can see that the type setting is not standardized there. It's printed by different publishers. This was kind of a home job that was borrowed type that was type set in the basement. There's a incredible story about the, the origins of this journal, and perhaps even more unlikely, is that this guy, Joel Hendricks, is the editor of this journal. He was self-taught in mathematics and astronomy. He had made money as a railroad surveyor, and he was essentially retired from his railroad surveying days and living with his family in Des Moines, which was at the time viewed as the border of civilization. So it's the red star over here on the left. And so where is most scientific activity happening, happening on the east coast in the population centers, which you can see, Am I back on? Which you can see in the, the kind of orange circles here. So that is about a thousand miles. That's a long way. And somehow, somehow this guy doesn't have any training, didn't go to any of the institutions where astronomers and mathematicians would be assumed to have been trained and made their professional contacts. He's not a member of any professional societies. There is no good reason this guy should be the editor of a mathematical journal in the United States that is the most successful mathematical journal in the 19th century, deeply mysterious, right? We saw in 1840, Benjamin Purse tried to start a research journal. He's at Harvard, right? Last for not even a year. This guy keeps his journal going for 10 years, and then it gets sent to the University of Virginia, and then it gets sent to Harvard, and then it gets sent to Princeton, and then it gets edited jointly by the Institute for Advanced Study and is now the Annals of Mathematics. How in the world did this happen? This <laugh> this is an incredible question, and this is actually how I got in to thinking about Eclipse expeditions at all. I was working on mathematical journals, and this is a question that came up. It's a perplexing question, and the answer of it turned out to be the 1869 eclipse, because Hendricks was living in Des Moines, Iowa, which was in the zone of totality in 1869, as Hendricks was a man about town. He was friends with the mayor, and the mayor threw a party for the visiting scientist who had come to Des Moines to observe the eclipse. And at that party, Hendricks met Simon Newcombe and his various compadres from the US Naval Observatory, the US Naval, uh, core of mathematics professors and various other visiting astronomers from other parts of the country. And he likely never, ever would've met any of these people otherwise. So a few years later, when his idea of a mathematical journal is realized, he draws on an incredibly wide network of correspondence in Boston and Washington DC and New York and Italy and the United Kingdom and around the world. And this is the correspondence that's, uh, interleaved in his own bound copy of the issues of the analysts, the journal that he began. And it successfully runs for 10 years, right? And this sort of flourishing of mathematical community is partially due of course, to the development of infrastructures, educational infrastructures happening in the US at this time, but it's also pretty significantly pinpointed as a result of an eclipse expedition that he starts this journal and a range of contributors participate in this journal, and mathematics is circulated in the United States in a way that it would not have been expected to do ordinarily. So this is perhaps an unexpected outcome for an eclipse expedition, and it exemplifies the incredible potential of scientific meetings to foster surprising collaborations and new ideas. A bit less surprising perhaps, is the fact that the enthusiasm from the 1869 eclipse generates huge interest in the eclipse in 1870. So there's enormous momentum for planning expeditions to observe Eclipse totality in Spain in 1870 per himself planned to go, it would be his only international trip. He never left the country otherwise. And he said the constitution of the sun. So what we can find out through spectral analysis of the solar Corona is the chief scientific problem of our time. And he thought the 1870 eclipse was going to remove the last obscurity from the subject. Well, that didn't happen, uh, but the 1870 eclipse did generate widespread excitement. And this map of the US observation camp party camp gives a sense of the size of their expedition party. So there's a transit observatory, a photography tent, a spectroscopic tent, telescopes outside as well. So there's a sort of a, a sizable number of people who've gone. And one observer that I want to just highlight here is Zina Fe Purse. So she's an American feminist and a founder of what becomes known as the Cooperative Housekeeping movement. So this is sort of primarily what she's known for. But she had married Charles Saunders purse, who was a employee of the Coast Survey. And as it happened, the son of the superintendent of the Coast Survey. And so they were going on this expedition. And so that's how she found herself on a ship crossing the Atlantic to observe an eclipse in 1870. And during the weeks at sea, she pinned photos of the moon to the canopy of her bed, and she practiced sketching. Could she capture a likeness of the moon? In two minutes, she would time herself and she would draw, because it was kind of all hands on deck. If we're taking you to this eclipse, you're gonna produce some observations. And she also tried to sketch the clouds of smoke on the steamer just to get practice sketching, things moving in the sky. And about her eclipse experience, she said, this is a quote, the time is too brief, the novelty too complete, and the agitation too great. I'm convinced for a person observing an eclipse for the first time to see truly more than one thing in it. Still her preparation paid off. She produced this sketch here that captures these three dark lines, uh, and these along with a photograph taken by a wealthy amateur, or taken as evidence that the Corona was in fact a solar feature. So there was some debate about whether the Corona was part of the moon or part of the sun. Uh, and her sketch here was taken as evidence that it was in fact a solar feature. Her father-in-law, declared the 1870 observations to be the triumphant vindication of American observations from the year before, the novelty of which had made them somewhat suspect in Europe. Uh, and he thought that it established the superior accuracy of the American predictions. So we can see he's ever got the angle on making American science more visible on the international stage. At a time when the sciences were not yet well established in the United States. These solar eclipse expeditions generated huge public interest and support connections forged beneath and about the sun's shadow. Sustained networks of communication facilitated periodical publication and set precedent for government funding and support of mathematical activity in the 19th and early 20th century in the United States. This provided the growing scientific community with a platform to advance mathematics and astronomy in the United States. And the highly publicized 1878 eclipse across North America involved a mistaken, sorry, citing of the intra mercurial planet. So that was huge news. That news, again, was debated throughout the 1880s and the 1890s, and eventually was debunked Newton's gravitational theory, which was powerful enough to predict. Neptune, as we saw, could only explain about half of the observed shift in Mercury's solar orbit as the close, as the closest planet to the sun. Mercury occupies a region of the solar system where Einstein's theory of general relativity suggested that the sun's mass would disturb space, time, and eclipse observations in 1919 and also 1922 confirmed Einstein's predictions and ushered in a general, uh, an era of general relativity. So this is a kind of iconic image, a photograph of the solar Corona from the 1919 paper by Edington and Dyson and Davidson verifying Einstein's theory of general relativity. So this is probably the most famous, uh, the most famous result of, um, kind of most well-known outcome from an eclipse expedition. There are nonetheless many other eclipse expeditions that also provide great material for historical research. And this work has developed a community of researchers who are captivated by 19th century eclipse expeditions, including a number of early career scholars whose projects at St. Andrews in particular have developed into publications and funded research positions. So I just wanna give you a little bit of an overview of some work that's currently going on. So this map here is the map of totality in 1871. So this is just following the eclipse at which Zena made her, made her sketch. So this is the, an eclipse across the Indian subcontinent, and a couple of students did some research on this about Rangan Char, who's pictured in the middle there. It's the first Indian fellow of the Royal Astronomical Society based on some observations that he made. Uh, and he also wrote this beautiful pamphlet, which is about the transit of Venus. Uh, and it's translated into six Indian languages. And it was a blend of Indian traditional astronomy with methods imported from Europe. So it's a really sort of incredible, uh, and incredible work. Uh, and this research was done by these two, som Lina there in the middle is now doing some graduate work. She's a chemist working in spectroscopy. Uh, and Meg Breyers there on the right has just started a PhD program, a PhD project directly related to this on women in 19th century British and astronomical field work. So she's a, um, max plank in, in Berlin. So another eclipse that has some sort of interesting historical features is this one, right? You can see it goes across Africa there and the very top of South America. And this particular eclipse features in some work that was done by Joelle Hendricks. So he is, uh, from Trinidad, and I said Hendricks, Joelle Beckel. He's, um, from Trinidad and was interested in doing some work on the eclipse observations in Trinidad in 1889. And this resulted in a paper in the notes and records of the Royal Society, featuring some individuals whose contributions to eclipse expeditions, uh, in Trinidad were unrecognized. Uh, I don't have any pictures of those individuals, but I do have a picture of Elizabeth Brown who went on that expedition. She funded her own way. She took along her cousin. It's an incredible story of adventures on the high seas. Uh, and they made some observations at the eclipse in 1889. Uh, in 1941, there's a passive eclipse totality that goes across China, which at this point is in experiencing extreme wartime conditions. Uh, and a student, Yong Lee, who should be purch pictured there, oh, he's not pictured anyway, is, uh, is working on this, uh, and has tracked down some of the official Chinese governmental reports about the observations that were taken in Lin Tao. Um, they had photographs, but they were also filming the eclipse for the first time. Uh, they had airplanes or an or airplane enlisted in service, which is an extraordinary governmental commitment during a time of war. And this was a very similar case to the kind of us interest in getting on the map. Uh, this sort of results of this solar eclipse in 1941 were the subject of the first radio broadcast. They talked about, uh, the observations from the eclipse. So this is some work in progress, um, that's turned out to be quite, um, quite exciting. Uh, there's also a team of students who have developed a website for public use. So the links to this are the Gresham website, the history and Science of Total Solar Eclipses. So some of the things I've talked about today, but also quite a lot of other interesting stories and other geographical locations and cultural perspectives on, uh, eclipse observation. So that's a kind of exciting, uh, exciting thing to look at. And these students who are doing these work and are joining a global community of scholars from the South Pacific, from the Indian subcontinent, from China, south Asia, Europe, African regions, who will all gather at an ICMS funded workshop that's upcoming. So this is happening, oh, oh, that's not there. It's happening a year from now. And it's a ambitious meeting that will bring together cross-cultural interdisciplinary cohort of scholars with a vision of generating a coherent sense of shared ownership of the mathematical tradition of Eclipse reckoning. So we heard earlier about some 11th century approaches to Eclipse reckoning, and the this is a subject of fascination over time and across geography. And we're hoping to pull together, uh, a wide number of scholars to, to think about this in conjunction, of course, with mathematicians, physicists and astronomers who are doing current work like this. Uh, to understand and model the solar Corona as in the 19th century, present day astronomers also see solar darkness as a valuable time-limited opportunity for observation and testing current theories. Now as then, high stakes astronomical expeditions depend not only on well posed scientific questions and adequate funding, but also as ever on the vagaries of changeable weather, uh, and delicate instruments. These are ongoing concerns and eclipse observation. They also involve networks of scientists working alongside students, civilian observers, journalists, broadcasters, and you too can share the collective experience of eclipse observations. Uh, there's several accessible paths of totality coming up. So there's the one I've already mentioned, uh, coming up in April, the, uh, 2024. If you missed that, there's one on the 12th of August, 2026, not so far away. Uh, also, uh, it'll go over the northern part of Russia there off the top of the map, uh, in 2027 over Northern Africa and 2028, when I'm really looking forward to this is five and a half minutes of totality. So fingers crossed it works out to be there for that. So mark your calendars now for an opportunity to forge your own connections in the shadow of the sun. Thanks. Thank you. I don't know very much about solar eclipses, but in the map that you showed of the line of totality in 1869, a lot of the observation points appeared to be very close to the edge, and I wondered whether there was a reason for it. Yes. So they want to know if they're right in where the edge is. So you'll see, um, sorry to do this. Uh, There we go. All right. So you'll see, I feel so sad always for these people who are just outside<laugh>. They didn't see anything. Um, so yes, that's exactly right. So they're, they're trying to figure out how accurately they've calculated the, the band of totality. So they put people exactly where they think it is. Uh, the people in the middle, they're, well, they don't quite make the middle, but uh, the people sort of closer to the middle are tasked mostly with, um, sort of more serious the scientific questions, the cameras, the spectro scopes and so on. Do our old friends, The Greeks have much to say about solar eclipses. Did they have much to say about, about them? Say about them? They were aware of them. I guess there's sort of reports of observing them Thought about 'em, wasn't they? I mean, there mathematicians, did they read records of what they thought? Uh, there are some, there are some records. The one, one thing that's challenging with sort of ancient eclipse observations, as I understand'em, so I'm not a classicist or a scholar of that period, um, is that if you are computing when a solar eclipse is going to happen, that's kind of one thing. But if you're computing where you have to be to see it happening, that's something else altogether. And so there are certainly ancient accounts of having experienced eclipse totality and assorted kind of legends that arise from that and so on. Um, but as far as a sort of a plan or mounting a research trajectory as it were for observing all of them, that that's a very 19th century, they, they Had no theory about the things then. No theories about it? Not as far, I wouldn't, not not as far as I know, but there are other people here who know more about that than I do. Thank you. Uh, thank you there. So there's yes, go this one 'cause you're nearest, then there's one in the back row. Just The last thing you mentioned about the 2028 Yes clips. You said five minutes. What's making it last longer? Is it known why? Oh yes. People know this. I don't think I'm one of them. Um, <laugh>, it, it just has to do with the sort of alignments of the innate orbits and so on. That's, yeah, sorry. I'm struck by the fact that, uh, the, the eclipses in the period that you were talking about particularly, but I guess in general also happen, uh, with a particular frequency, not precisely regular of course, but with a particular frequency that allowed us to predict and then plan and then observe and then make capital out of the result. In other words, it seems to have been very fortunate not only for American science actually, but all over the world, that, that these events that are completely out of our control, but they happen at exactly the right frequency. That, that the scientific community in general was able to, uh, make not only scientific use of them, but also embed itself and get significantly greater funding as a result. I'm just puzzled to know whether anybody can think of any other natural phenomenon that has that particular feature. This seems to me to be an unusual feature of eclipses. Well, there certainly are other kind of periodic astronomical events, right? The inter the transit of Venus, the changing of the seasons, right? There's all kinds of astronomical events that happen periodically. Things like the tides happen also on a sort of regular basis that at can be observed, comment, alley comment, right? Things like, if you wanna think about other sort of natural, I guess the comic would be the, the other one that a good candidate, it ties happen every day. These, these are the things that you can build up to a scientific and you can convince a government that it's got time to put funding aside. Is that what I mean? Yeah. The um, the Transit of Venus in 1874 was epic governments around the world. I mean, the amount of money that was spent, the amount of people that were shipped to all corners of the globe, the effort that went into the 1874 transit of Venus is really hard to overstate. Um, and it unfortunately was hugely disa <laugh>, hugely disappointing. And many people then didn't, many entities did not have other exhibitions go in 1882 because it was so expensive and it was so disappointing. Um, it wasn't until 2012 that was figured out that the Black drop problem is why it was so disappointing. And they actually, it was impossible, the task they had set for themselves to time the, the transit at Venus. So that, that, that's a kind of, I would say a pretty singular case that the epic nature of the expeditions for the Transit of Venus. Thank you. If I, I'll take prerogative and ask the final question. Just because of the transit of Venus, you talked about the reason why that's gonna help you determine the distance to the sun is because you're using parallax. Does that mean you need to be able to observe it, not just well in one place, but in two quite far away places? Yes, exactly. And so that's the reason for the massive coordinated efforts to send people to opposite sides of the globe. Yeah. To, to observe and then to not just have them in two places on opposite sides of the globe, but more places in case of cloud, you know, bad weather, right? You wanna try to cover your bases. Yeah. So with a, it was a really extraordinary amount of time and effort and planning and expenditure of resources and there are many incredible tales of people who tried and failed and Yeah. Et cetera with the observing the transit of Ven. Yeah. Yes. So it goes with astronomy, I guess. So it always goes, yes. Um, so listen, we, we need to wrap up now, but um, I want to say a few thank yous. So thank you of course to our wonderful speakers this afternoon who just a fantastic array of talks in, in just covering such a huge variety of topics. Um, thank you to everyone at the BSHM and at Gresham College for all that they've done in helping to organize just smoothly run events, which, uh, which has been a delight to have the easy job of just standing here and saying a few words that I had the easiest possible job of all of it. So I'm grateful for all the support that everyone's provided. Um, and thank you everybody for coming, attending and asking such fantastic questions. We hope to see you again at the SHM events and at Gresham events in the future. So do look at the websites of both our organizations and see what is coming up. And we hope to see you at those. But that's all from me today, so let's give everyone a big round of applause. Thank you very much for our speaking.