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