SYMHC Classics: John Dalton

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Speaker 1: Cappy Saturday. John Dalton was born on September fifth or sixth, seventeen sixty six or two hundred and fifty nine years ago today or possibly yesterday on the day this episode is coming out. John Dalton was a physicist and a chemist, but he's also known for his discoveries related to color vision and color vision anomalies. Our episode on John Dalton is Today's Saturday Classic, and it originally came out on January twentieth, twenty twenty one. Enjoy Welcome to Stuff You Missed in History Class, a production of iHeartRadio. Hello, and welcome to the podcast. I'm Holly Frye and I'm Tracy V. Wilson. Tracy, I bet this happened to you. I know it happened to me. Like you must have had those moments as a child where you thought you were being very insightful. I know I certainly did where I was like, how do I know that what I see is the same thing as other people see? I had this exact Yes. Yes, I also asked my mom one time. I was like, Mom, how do we know that what I see as green is the same thing as what you see as green? And my mom stay at home mom with two little children did not always have a lot of patience for weird questions. And she was like, it's the same. I'm not trying to drag my mom in any way. My mom was like of our creativity and attentive to art. But yeah, this was a case where I liked I just asked her in a question she was not prepared for question time. Here is the thing. I asked the same question of my father, who I did not know, and I don't know that he knew at the time, did not see color the way, so he was trying to describe things. And I just remember, I mean, I was probably like seven or eight, already kind of a smart alec and I was just like, okay, this is going nowhere. I'm out. So maybe just saying green is green was a really a better route because that led to a lot of confusion in our lives for a moment until we finally put the pieces together right, And really what happened was that. And I don't mean to drag my father, but like he was career military, so he's now retired, but his clothes were like sort of prescribed for sure. When he stopped being constantly on active duty and started picking out his own clothes. So things became readily apparent, which is that that does not go together. My dude, Yes, they look they're practically the same color. Oh, we should address this, right. That's we never knew for years, when you're wearing like jeans and a plaid shirt in your off time and then a uniform the rest of the time, it would never come up. Now we learned. But this curiosity about whether other people see the way that you see is really what drives a lot of scientific discovery. And we are talking about somebody who was curious and did a lot of scientific discovery. But in the case of this subject, who was very well known and respected in his day, he just didn't think about how he or anyone else saw color until he kind of stumbled into it while studying plants and realizing that his vision might be different from other people. And that's John Dalton, And really John Dalton is far more famous for his work in atomic theory, which builds the foundations of organic chemistry, but he also wrote one of the first really thorough descriptions of what he called anomalist's vision, meaning that he realized he was not perceiving color in the same way as other people, and his descriptions are very entertaining. We're going to read some of them, so today we will talk a little bit about his life, but mostly about this sort of pocket in his scientific work, where he made a brief foray into exploring the world of photoreceptors and color perception, although he didn't use those words for it. Color blindness is a term that's falling out of favor because it's not really accurate. Colorblind suggests that somebody can't see color at all, but most people who have historically been diagnosed with color blindness can see colors, they just see them differently. So defective color vision or color vision deficiency are becoming more preferred terms. I feel like I see people describing themselves as colorblind still quite a lot. So this is something that's evolving. We're still kind of at the beginning of the scientific community shifting to these different terms, and it's really about clarity more than anything else, right, like, no, you do see color. We'll talk about one exception, but just differently, So we need to make a clearer term for it that's not misleading. And color vision deficiency is the inability to distinguish specific colors red, green, and blue, and to be diagnosed as colorblind historically or color vision deficient. Now, a person only needs to have an inability to distinguish one of these colors, but it is possible for someone who has color vision deficiency to be unable to distinguish all three. So in your retina, you have cells called rods, which perceive light, and then three types of cells called cones. Cones are really the important factor here. They are the photoreceptive cells that enable us to perceive color. The human retina contains six million cones. Red sensing cones make up sixty percent of the total number of cone cells, green sensing cones make up thirty percent, and blue sensing tones make up the remaining ten percent. So if all of your cone cells are functioning normally, you are said to have trichromacy, meaning you can see three try of these colors. They combine to create standard vision. But it is also possible to have dichromasy with only two types of cone cells present or functioning, or even monochromacy where only one type of cone is functioning. Monochromacy is a little bit tricky because it can also be used to describe a scenario where none of a person's cones are functioning, and a person who has monochromacy may have other vision issues as well, And monochromacy that we just talked about with no cone function is kind of the one variation in all of this where the color blind label would be actually pretty accurate, because everything to them appears not in the rainbow of colors, but as a shade of gray most of the time. Dichromacy manifests itself in a way that a person can't see a difference between red and green, and dichromacy of this nature is broken down into separate classifications based on which types of cones do and don't work in a person's retina. Protonopia describes a state of not being able to see red, and due to anopia is a case where the red cones function but the green cones do not. Blue yellow color deficiency, which is a little rarer, is similarly broken down into classifications based on its specific nature in a given person. So someone with a lack of blue cones is said to have tritonopia, and if they have blue cones but reduce sensitivity to that color, it is actually described as tritinomaly. An all color vision deficiency can fall on a spectrum. Some people have a diminished ability to distinguish red from green, for example, but they're able to see difference within specific shades of these colors. Yeah. Sometimes you know, people can't hit the lighter tones of the darker tones get real muddy, but they can see different shades. It's all. It manifests in many different ways, and in the United States an estimated five to ten percent of the population have some form of color vision deficiency. Usually this gets tested for when people are kids, and more boys than girls have colored vision deficiency, and the percentage shifts based on race. So there was a twenty fourteen study that gets cited a lot. This was published in the journal Optthalmology, and it had taken studies of the color vision of four thousand California children ranging in age from three to six. And in this study it was found that among the girls, less than half a percent of them exhibited signs of color vision deficiency, regardless of race, but in boys the numbers were different. Six percent of the white boys in the study were diagnosed with color vision deficiency, three percent of the Asian boys had some form of color vision deficiency. It was found in fewer than three percent of the Latino boys and less than two percent of Black boys. Genetically, boys are more likely to have red green color vision deficiency because they only need to inherit it from their mother. It is a recessive characteristic that's associated with the X chromosome. So if a female inherits the trait from her mother but not her father, she'll generally have normal color vision she only has that one X chromosome, but then she could pass the trait onto her own children. And this is different from blue yellow color vision deficiency, which is a dominant characteristic, and so that only needs to be inherited from one parent, and it is not linked to a person's sex. I'm just gonna say these are related to sex and not to gender. That's the different thing. Yeah, we're going with kind of that twenty fourteen studies Separation of Boys and Girls, which simplifies the whole discussion, and is sex assigned at births not necessarily? How if they did that, I would be fascinated if they did the same exact test today and how they would break it out, because it's things have shifted a bit. So if anybody knows of any studies similar to that going on today, I'm very curious. But here's the thing. You're probably wonder how we figured all of this out. And in the late eighteenth century, this idea of people perceiving color differently than most humans was certainly not unknown. King George the Third, for example, reportedly discussed this with an English novelist, Fanny Burney, at court in seventeen eighty five, and there were some theories about what caused color vision anomalies published in Germany in the late seventeen hundreds, but the first systematic analysis of color vision deficiency appears in seventeen ninety three, at least the first that we know of, and that brings us to the person we mentioned at the top of the show, John Dalton. John Dalton was born in early September seventeen sixty six. His actual date of birth is either September fifth or September sixth. His parents, Joseph Dalton and Deborah green Up Dalton, were Quakers. His father made a living as a weaver. The Dalton's had three children who lived to adulthood, and John was the youngest of them, and as a child, John attended a Quaker school and that school chain hands. When John was twelve, John Fletcher, the man who had been running it, gave it to John Dalton's older brother, Jonathan Dalton, and then Jonathan enlisted John's assistance in this new role, and this set John on a path as an educator. Just kind of delights me that they had a John and a Jonathan. It makes me giggle as well. John and Jonathan expanded their new careers by taking over a school in Kendall, England, when John was just fourteen. This was a larger operation than the Quaker grammar school they had been running, and it included students who boarded as well as day students. That's totaled about five dozen students in all. And John was sort of learning on the job. He was studying with scholars to learn math, Latin, Greek and science to stay ahead of his students and to be able to speak on the subjects of their curriculum. And keep in mind, again he's like fourteen fifteen at this fight, so he is taking in a lot of information. And he stayed in that job for a dozen years and then at the age of twenty seven, John moved on to a new professional post as a mathematics teacher at New College, and this was in Manchester. And he found all this a little bit frustrating though, because his workload in that job prevented him from having time to pursue his own scientific study. So he switched gears and decided that he would become a private tutor so that he could manage his own time in a way that would enable him to carry on with his side work. At this point, his work outside of his daily teaching task was focused largely on meteorology. He had been publishing articles in the subject for several years, but he kept studying other sciences as well, and it was through these studies that he wound up writing a paper that expounded on the idea that not everyone saw colors in the same way. So this was not the first time the mention of non standard color vision appeared in print. As we said earlier, surely, color vision diviiciency has been in play almost as long as humans have existed, and even before Dalton there had been some mentions of it, including a write up of a man named Thomas Harris that was published in Philosophical Transactions and that described Harris's Inability to Distinguish Colors, which was published in seventeen seventy seven. We're going to come back to Harris and we'll talk first more about John Dalton. But before we do all of that, we're going to pause for a brief sponsor break. John Dalton presented his paper, which was titled Extraordinary Facts relating to the Vision of Colors with Observations by Mister John Dalton, at Manchester's Literary and Philosophical Society on October thirty first, seventeen ninety four. He had joined the Society upon moving to Manchester. And as scientific papers go, this one is kind of unique in that Dalton himself is really the subject of the paper, or at least his vision was. That text opens with quote, it has been observed that our ideas of colors, sounds, tastes, et cetera, excited by the same object, may be very different in themselves without our being aware of it. He goes on quote I was always of the opinion, though I might not often mention it, that several colors were injudiciously named. The term pink in reference to the flower of that name seemed proper enough. But when the term red was substituted for pink. I thought it highly improper. It should have been blue in my apprehension, as pink and blue appear to me very nearly allied, whilst pink and red have scarcely any relation. He goes on in his introduction to mention how he had learned about light and optics in his scientific studies, but he hadn't really thought about applying any of that information to colors because that entire area, the idea of color, seemed kind of confused and odd to them. Like he really was, like, why would people group these colors together? It doesn't make any sense, But I guess that's how we've always done it. It was not until he turned his scientific work to botany that he really started thinking about why some color groupings just made no sense. And this study prompted him to ask other people questions about colors. He actually uses the example in this paper of asking a person whether a flower was blue or pink. But they always just thought he must be joking because the queries came off as so completely absurd to them. So he just thought everybody had this weird relationship with color, even though he thought colors made no sense. It didn't really occur to him to wonder if there was something unusual about the way he was perceiving colors. It was a moment in seventeen ninety two, two years before he presented his paper, that really gave him this moment of pause. That moment happened when he was looking at a geranium by candlelight. So he had frequently seen these flowers in this particular variety he was looking at were in fact pink in daylight, and to him, in daylight he perceived them as sky blue. But by candlelight, he saw this flower as a vibrant red, And this significant shift in their color due to lighting changes startled him and led him to make a quick study by asking a number of friends to look at these same flowers in both daylight and candlelight. All the people he initially asked about it saw them as pink in both lighting conditions, except for his brother, who perceived that same shift of them being sky blue in the day and red in candle light. This experience caused him to start a more structured study of light and color, which he did with an assistant who had quote normal color vision. First, he used a prism to project sunlight into a dark room and then recorded the number of colors that various people saw in that band of light. Most of them saw six red, orange, yellow, green, blue, and pearl. He does mention that purple is separated into indigo in violet in Newton's writings on color for the purposes of a person simply looking at a band of light, that distinction is really nominal. I think we talked about this in one of our episodes that touched on Newton previously. He put indigo and violet in there separately because he wanted there to be seven. So that's why people typically don't actually see them as two estate shades in light from a prism. Yeah, or you'll see what you think is maybe a slight difference, but it's hard to be sure. Yeah, So for Dalton, he just called that one thing, it's purple. When Dalton looked at the prismatic light, though, he could only make out two or sometimes three colors, so generally he just saw yellow and blue, or sometimes he would see yellow, blue and a little bit of purple. And through his work he identified that the band that he saw as yellow was where other people were seeing red, orange, yellow, and green, and he wrote quote that part of the image, which others call red, appears to me little more than a shade or a defect of light. After that, the orange, yellow, and green seem one color which descends pretty uniformly from an intense to a rare yellow, making what I should call different shades of yellow. Dalton's perception of blue and purple aligned with what other people were seeing, and the contrast between the end of his band of yellow and the adjacent blue was really sharp. So next he did the same collecting of perceptions from himself and others when looking at candle light projected through a prism, and these results were mostly the same. The only exception that Dalton calls out is that for him, the red edge of the image looks more vivid in candle light than it did looking at sunlight under the same conditions of being put through a prism. Dalton's paper next breaks out studies of specific colors as he had always perceived them. He starts out by describing color grouped with red as they appear in the daylight versus candlelight. His description of Crimson is pretty charming. Quote Crimson has a grave appearance, being the reverse of every showy and splendid color. A similarly quaint description is his description of pink. He breaks that down as nine parts light blue and one part red quote or some other color which has no other effect than to make the light blue appear dull and faded a little. He also lists out all the flowers that to him look blue to give the reader a sense of context. When he says he says pinks and reds as blue, blood, he says appears to him as the color most people call bottle green, and he mentions that if he saw a light colored stocking that was spattered with either fresh blood or dirt, he would not be able to tell the difference visually. I love this entire paper so much. It's exactly like this the whole way through. His turn of phrase is quite quite charming and endearing. He goes on to describe the significant change that red undergoes for him when viewed in candlelight. He describes it as much more vivid, and the blue no longer being present and instead replaced by yellow tones. While he found most reds and pinks quite drowned by daylight, in candlelight, they became really vivid and even exciting. Orange and yellow, he says, are not too different for him than anyone else. When he moves on to discussing green, he writes, quote, I take my standard idea from grass. This appears to me very little different from red. The face of a laurel leaf is a good match to a stick of sealing wax. Hence, it will be immediately concluded that I see either red or green, or both different from other people. The fact is I believe that they both appear different to me from what they do to others. He concludes that blue he generally sees the same as other people, and purple is just a little bit different from blue. He described brown in the same creative way that he does other colors, writing quote, my idea of brown I obtain from a piece of white paper heated almost to ignition. He also notes that seeing colors in moonlight presents the same or near same results for him as seeing them in candlelight. Lightning gives the same effect as daylight. It doesn't matter whether the sun is rising or setting when it comes to color, and any kind of combustible substance creates the same color perception as any other flame. He concludes the section of the paper with quote, my vision has always been as it is now. His next section breaks out the information that he's collected from other people and their perceptions of color, starting with people he has found who have vision that seems similar to his own, and Dalton mentions mister Harris of Maryport and his alternate perceptions of color. Dalton thought that, based on the description, Harris's anomalist's vision might have been different from his own. He discovered that one of Harris's brothers was still alive, so he made contact and went to visit. Upon questioning this brother and testing his vision, Dalton found that the Harris family seemed to have the same genetic variable that he and his brother had when it came to how they perceived the colors of the world around them. This led to a general line of questioning of the students and colleagues that Dalton regularly came in contact with kind of as a subject group, and he found a small proportion of them shared his specific experience regarding pink and light blue looking similar by daylight and different by candlelight. Dalton also found just a couple of examples of people who quote differ from the generality and from us, also meaning that they seemed to have a different type of color vision deficiency. He also mentioned a shared experience among all of these people that just as with him, it had not occurred to them that they were seeing things differently from the majority of people, but that they too found the names and groupings of colors perplexing at times. Though his paper was really the beginning of science's study of color vision deficiency, even in his really relatively small data set, Dalton was already capturing information that showed a difference in instances of color vision deficiency in regards to people's sex. He noted that in the Harris family, four of six sons in the family had what would come to be known as color vision deficiency, sometimes also called Daltonism for obvious reasons, but their sister didn't. Similarly, Dalton and his brother Jonathan had the same color experience, but their sister did not. He wrote, quote, it is remarkable that I have not heard of one female subject to this peculiarity. He also included the line quote, I did not find that the parents or children in any of these instances have been so unless in one case. So. Even though he didn't really realize it. He was gathering information on the recessive genetic nature of red green color vision deficiency. Next up, we'll talk about what Dalton thought was causing his anomalist vision, but first we will take a break for a word from our sponsors. The third section of Dalton's paper tries to unravel the cause of what he was referring to as quote our anomalous vision. One of the ways that he worked out his theory here was to work with transparent colored liquids, and then he would have various people look at objects through those transparent colored liquids to record their perception of color. So he would hold up a thing behind, like a tank of blue water, whatever, and ask them what they saw. And because people with you know, quote unquote normal vision described color similar to what he saw in his normal day to day life when they looked through a tank of blue water, he came to this incorrect conclusion that quote one of the humors of my eye must be a transparent but colored medium, so constituted as to absorb red and green rays principally because I obtain no proper idea of these in the solar spectrum, and to transmit blue and other colors more perfectly. Honestly, this is a totally reasonable conclusion based on understanding rates. He outlined how this would impact the perception of various colors, and then addressed why the colors changed so drastically for him and others like him in candle light, writing quote, when any kind of light is less abundant in blue, as is the case with candlelight compared to daylight, our eyes serve in some degree to temper that light so as to reduce it nearly to the common standard. The Earth's atmosphere, he believed, was a blue fluid that quote, modifies the Sun's light so as to occasion the commonly perceived difference. So this paper was met with some curiosity, and his very detailed comparisons of his vision to that of other people who saw color normally offered a lot of insights. But this idea of a blue humor in his eye that was causing his anomalous color vision was kind of dismissed by the scientific community, and in response, Dalton, who really thought he was onto something with it, donated his eyes to science. He wrote up a document that requested that his eyes be dissected upon his death to see if he had been correct and whether there was any other physical evidence to explain the way he perceived color. A little less than a decade after Dalton's writing on his anomalous vision, scientist Thomas Young published on the theory of light and colors, and this put forth the idea that there were receptors in the eye for each of the colors red, green, and blue. So he was totally onto it. And Young addressed Dalton's work and his anomalous color vision with a different theory that there was a quote absence or paralysis of those fibers of the retina which are calculated to perceive read. He was so completely on the right track that you would think that this would have just broken eye science wide open. But no, no, it advancement slowed down after this and studying the eye, and that went on for decades. Yeah, I was like people were like neat idea, and they moved on to other stuff beyond the study of color vision deficiency. John Dalton, of course, continued to make important contributions to the scientific world concurrently while working on figuring out why he couldn't see flowers the same way as other people. He also published a work titled Meteorological Observation and Essays. He published additional work in meteorology as well, and his work in this field led to some fellow scientists considering him the father of meteorology, although his work anytime somebody gets called the father of something, I always have to go eh, because his work was of course building on that of his mentors on this subject. He had particularly had a really good mentor in meteorology when he was studying as a teacher. Dalton also did a lot of work in chemistry, specifically atomic theory. His work in this area came to some incorrect conclusions, but it was also instrumental in moving the scientific community away from the long held idea that matter was, at the basic level all the same and just configure differently to form different things. Dalton championed the idea that there were all kinds of different atoms with different sizes and weights, and that they behaved differently. He started a project to measure the masses of different atomic particles to begin cataloging all of the different atoms that could be found. He presented the first table of atomic weights in eighteen oh three, and his work in this area propelled organic chemistry forward. He is also sometimes called the father of chemistry. Dalton had joined the Manchester Literary and Philosophical Society in seventeen ninety three when he was still in his twenties. In eighteen seventeen, as a man in his early fifties, he became its president. He held this position for the rest of his life. His scientific career slowed down quite a bit. Yeah, there were some other issues where he had some papers that were denied for publication, and it just wasn't like the heyday he had when he was a little younger. He had the unique distinction though, of seeing, for example, his own statue erected in Manchester during his lifetime for his accomplishments. And while he had been barred from an education at Oxford or Cambridge as a young man because he was a Quaker not an Anglican, he received honorary degrees from both later in life. He also served as a foreign Associate of the French Academy of Sciences. On April eighteenth, eighteen thirty seven, Dalton, who was seventy at the time, had a stroke that resulted in a part paralysis, and then he had another small stroke or possibly a seizure several days later. Being pretty pragmatic, he set his affairs in order as soon as he was recovered enough to do so. But then he lived another seven years. He continued as president of the Literary and Philosophical Society. He made visits to Lake Country. That's something that he had been doing throughout his life. Yeah, it was a very close call, and then he kind of was like, well, I'm still alive. I'm going to keep doing my living stuff. John Dalton died finally on July twenty seventh, eighteen forty four. He was really really beloved in Manchester by this point, and he was given a public funeral by the city on August twelfth, eighteen forty four, and estimated forty thousand people paid their respects before Dalton was interred. The day after Dalton's death, on July twenty eighth, eighteen forty four, his wishes were carried out. His eyes were dissected. This was done by doctor Joseph Bransom to determine whether this idea about having a blue humor and his eye was correct. Of course it was not. Ransom described what he found in Dalton's eye as quote perfectly pellucid. Ransom also sliced off a section of the posterior pull of the eye and used it as a lens to see if colors that were viewed through it, especially red and green, took on a different hue, which they did not. But Dalton's eyes were not discarded after that, so for clarity he did the full dissection on one eye. That little part he sliced off was from the second eye, so he had only taken the primary samples from one. The other was mostly intact, and the remains of Dalton's eyes were preserved and were eventually given to the Manchester Literary and Philosophical Society. That was not the end of their story. One hundred years after Dalton died in nineteen ninety five, a DNA analysis was conducted on his preserved eyes, and this examination determined that he had deuterinopia, conclusively proving that he had red green color vision deficiency. Two years after those findings were published, in nineteen ninety seven, the eyes were donated to the Science and Industry Museum in Manchester and they remained in the collection there to this day. YEP, you can find pictures of them online in the eighteen seventies, German anatomis Max Schultz identified the rods and cones of the retina and deduced that rods were dedicated to night vision and cones to daylight vision. Then later in the eighteen seventies, Wilhelm Cune laid the groundwork for a concept of photochemical basis for vision. In the eighteen nineties, Spanish neuroscientist Santiago Ramoni Cajel studied the retina and drew detailed diagrams of the cells within it. Cahl's scientific drawings are incredibly intricate and very beautiful, and they were part of an art exhibit at NYU in twenty eighteen. Yeah, so, you know, all of the things that would have explained to Dalton what was going on came a little too late. There was also a cool discovery in nineteen ninety one. So recently a new kind of photoreceptor was discovered, the ganglion cell, and that once again refined our knowledge of how the human eye takes in and processes visual information. Always learning. I really, really really love John Dalton's story, and I love this part of it. I knew a little bit more about, you know, his work in establishing the basis of a lot of the chemistry we use. But I didn't. I had never read this paper before, and I honestly it's the most fun read. Thanks so much for joining us on this Saturday. If you'd like to send us a note, our email addresses History Podcast at iHeartRadio dot com, and you can subscribe to the show on the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.