 I'm Bill Hammack. And I'm Don DeCost. And we created this lecture series, Michael Faraday's The Chemical History of a Candle with Alex Black, a chemistry undergraduate at the time at the University of Illinois. And this commentary track is intended to enhance and enrich the lecture by looking at some of the larger issues that Faraday is going to touch on. You know, and Faraday lets us know right away that this is more than just about a candle. He tells us that there's no better window into science than studying the candle. He's going to hint at and discuss a lot of things, chemical reactions, density, the nature of gases, capillary action. And if you haven't watched these lectures yet or read these, spoiler alert coming up here. By the last lecture, he's going to compare human respiration to the combustion of a candle. And Bill and I have found it very useful to rewatch these lectures again knowing that he's going to do that because it's really fascinating to see the logic that he uses and how he goes about reading us naturally to this point. And the way he does this is by asking questions and making observations. And so he's actually modeling the scientific method or scientific process for us. And in fact, in the lecture, he's going to come back and explicitly tell us that he's doing this. And I think something to make more explicit from Faraday about this part that I really like is that the heat serves two purposes. It melts the wax, which is more obvious. But it also then, by causing the convection currents, it allows the air to flow over the candle and then it cools down the wax on the outside. So it heats and cools at the same time, allowing the candle to keep its shape. So now Faraday's next sentence is one of my favorite and really captures something really important in the lectures. The same force of gravity, which holds worlds together, holds this fluid in a horizontal position. And if the cup be not horizontal, of course the fluid will run away and guttering. And we'll see Faraday make this point again and again throughout the lecture. The point that science gives us a uniform explanation for nature. And this is probably a good time to talk about the language and our choice. You just heard the phrase, if the cup be not horizontal, obviously we decided to keep Faraday's original language. You'll hear many other examples of this in the coming lectures. We decided to do this for a few reasons. One, historically we wanted to keep the language. He's also very poetic in a lot of places. But it's also very vivid in the same passage we heard him use the phrase, holds worlds together. And that really tells us what's going on. But it's a very vivid way of saying that. Yeah, in addition to being vivid, there's also a precision to it, even though it's not always what we will call strictly scientific language today. And I really like the way that Faraday makes segues and makes transitions. He talks, first of all, that the utility of a candle is what's important. And that's actually its beauty, not what it looks like, but how it acts. And then he also looks at candles like these that are bad burning candles. And he finds some beauty in those too. And that beauty is we can learn something about burning by a negative result. Yeah, indeed, as scientists, we can learn from any result. And in fact, in beautiful language, Faraday makes that same point right about here. We come here to be scientists, and I hope you will always remember that whenever a result happens, especially if it be new, you should say, what is the cause? Why does it occur? And you will, in the course of time, find out the reason. So this really nicely sums up the nature of science, and it's a theme that really permeates all of these lectures. And of course, part of this nature is to ask a question, and the question doesn't always lead to an answer, it leads to another question. So he asks the question about the chemical change that occurs in a candle, and that leads him to wonder about the physical change, and that is, how does that wax get up to the flame? You just mentioned physical and chemical changes, and those are going to be really important throughout the lecture. And let's listen to how Michael Faraday discusses chemical and physical changes in a very colloquial yet still precise language. Especially when you come to learn what a vigorous thing flame is, what power it has of destroying the wax itself when it gets hold of it, and of disturbing its proper form if it comes only to near. And so the flame does two things then. The flame melts the wax, and that's a physical change, and Faraday uses the term disturbing its proper form, which lets us know it's actually going then from a solid to a liquid. The flame also allows the wax to react with the oxygen as we'll find out. Yeah, it destroys the wax, and it turns the wax into something new as we'll find out we get carbon dioxide and water as products of the flame. And so this is a chemical reaction. Now, when students are first learning chemistry, this difference between chemical and physical change is a difficult one. It helps if the students think about the molecules, and Faraday provides language that helps us view it this way. Destroying, destroying the molecules, and just disturbing the molecules, changing the form. And Faraday will return to these chemical and physical changes in every lecture. And so this is one example of something that we changed that Faraday did. It's the same idea about different materials. Faraday used Rutan Cain and Camfer because he had the materials in his time, and we decided instead to use a salt column and alcohol to show capillary action of a fluid. You know, and this is one of our favorite demonstrations of Faraday's. It's just so vivid. Don just said a minute ago, it's both good looking and good working. And you really can understand how a part of a candle works after you see this. And so let's return to Michael Faraday here because he just summarizes this so aptly. The fluid has risen by the capillary action of the salt just as it does through the wick in the candle. So another thing about the language, we mentioned a little bit ago that we decided to keep his language for certain reasons, historical reasons. It's very vivid and so on. Obviously the language that he just said, that we had him just say, the capillary action of the salt, those were our words because as we mentioned, we changed the demonstration to include a salt column. And so we did this when we needed to do this. We kept his language as much as possible if we needed to change a demonstration or we needed to say something in a slightly different way. We changed the language slightly. So the demonstration that we just saw and the one that's coming up are used to show that the fuel used by the candle is vaporous. So in that experiment where he turned the candle over, the liquid would come down on the flame and the candle cannot burn, the liquid fuel has to become vaporous first. And then this experiment that's coming up is a very famous one where he's going to relight the vapor. And I should note that both of these experiments are a little difficult to do when we turned the candle over, that took a number of tries and you're going to see me lighting the vapor here in just a second and this was certainly not a single take that we used to do this, that we did this in. And in fact, what's interesting is Faraday in the later lectures does even more fantastic things in piping that vapor around through a glass tube and relighting it. Things that just are, I find just truly astonishing. So in this section that's coming up, Michael Faraday it's lyrical about science. And you can really see or hear his enthusiasm come through and so I think we should just let him speak for a moment here. Where you such beauty and brightness is nothing but combustion or flame can produce. You have the glittering beauty of gold and silver and the still higher lustre of jewels like the ruby and diamond. But none of these rival the brilliancy and beauty of flame. What diamond can shine like flame? It owes its luster at night time to the very flame shining upon it. The flame shines in darkness, but the light which the diamond has is is nothing and to the flame shine upon it when it is brilliant again. The candle alone shines by itself and for itself and for those who've arranged the materials. Let's be Faraday here for a moment and make all the observations we can. The wick is bright at the end, it's blacked on the length of it up to where the wax is and the flame only touches up to where the wax is and the flame is multicolored as well. Of course what he did was he turned those all into questions and used that to motivate a scientific investigation into how a candle works. And so if you know where Faraday is going with this, he just dropped a couple of really big hints. He mentioned the phrase, ignition is not so perfect, which is talking about incomplete combustion, which he'll get into more about not being able to burn the carbon completely. He used the phrase, matter rising about it, which is the carbon dioxide, which takes up almost an entire lecture. And he used the phrase, which you do not see, which is the first hint that he's going to work at getting the invisible visible for us. Yeah, in fact, that's going to come up again and again throughout the lectures. This is the first example using these shadows where he makes the invisible visible, but we'll see examples of that throughout the lectures. And this is one of the many times I think both Bill and I were just fascinated by what we saw in that we actually see a shadow of a flame, which never occurred to me that we could do that. And what's great about this as Faraday points out is that the darkest part of the shadow is actually the brightest part of the flame. And it's worth making a tie to the later lectures in that here he makes the observation that the brightest part of the flame shows up darkest in the shadow. But as we explain in later lectures, that's because there's incandescent particles, carbon particles, that are what give a flame its brightness. And in that last clip, we used some special effects so that we could take photographs of the flames of those candles. And we did this because Faraday actually said that. He said that we have to photograph these in order to find out everything concerning them. We were very surprised to hear him mention photographs and we found out that he was very interested in photography. And in fact, at the Royal Institution in January 1839, he made the first public announcement in Britain of the New Art, which was to become photography. So now let's listen to Faraday as he explains this demonstration that he used with this sufficiently large flame. You have the air creeping in over the edge of the dish forming these tongues. Why? Because through the force of the current and the irregularity of the action of the flame, it cannot flow in one uniform stream. The air flows in so irregularly that you have what would otherwise be a single image broken up into a variety of forms. And each of these little tongues has an independent existence of its own. Indeed, I might say you have here a multitude of independent candles. Now with that phase, a multitude of independent candles, Faraday introduces a kind of reasoning that he'll use more often throughout the remaining lectures. It's reductionism. In other words, it's a way to look for a unity in nature by reducing it to some essential elements and actually making the philosophical point that these elements are identical. And by elements here, we mean principles. Notice he's not saying that this large flame is like independent candles. He's saying you have here a multitude of independent candles. So instead of just being an analogy, he's actually equating the two. And I think this is a good reminder at the end of the lectures that, well, the lectures appear to be about a candle and then ultimately about respiration, that really these lectures are an extended study in the scientific method, in how you reason as a scientist and how you ask questions. And in fact, at the very end here, he asks a series of questions that then will be answered in later lectures. And so as you'll see here at the end, this video series has a companion volume, a companion book that goes with it. It contains transcripts of all the lectures. And it also contains lecture guides written in contemporary language. And it includes as well a set of activities that you could do at home or at school. And you'll notice that there's a free PDF at the website and there also you can buy hardbound copies and paperbound copies and electronic versions. So I'm Bill Hammack. I'm Don DeCost. And thanks for listening.