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BY THE LATE CHARLES MEYMOTT TIDY, M.B., M.S., F.C.S. FORMERLY BARRISTER-AT-LAW; PROFESSOR OF CHEMISTRY AND OF FORENSIC MEDICINE AT THE LONDON HOSPITAL; MEDICAL OFFICER OF HEALTH FOR ISLINGTON; VICE-PRESIDENT OF THE INSTITUTE OF CHEMISTRY; ONE OF THE OFFICIAL ANALYSTS TO THE HOME OFFICE.

LONDON: SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE, NORTHUMBERLAND AVENUE, W.C.; 43, QUEEN VICTORIA STREET, E.C. BRIGHTON: 129, NORTH STREET. NEW YORK: E. & J. B. YOUNG & CO. 1897.

PREFACE

These lectures were delivered with the assistance merely of a few notes, the author in preparing them for the press adhering as nearly as possible to the shorthand writer's manuscript. They must be read as intentionally untechnical holiday lectures intended for juveniles. But as the print cannot convey the experiments or the demonstrations, the reader is begged to make the necessary allowance.

The author desires to take this opportunity of expressing his thanks to Messrs. Bryant and May; to Messrs. Woodhouse and Rawson, electrical engineers; to Mr. Woolf, the lead-pencil manufacturer; and to Mr. Gardiner, for numerous specimens with which the lectures were illustrated.

THE STORY OF A TINDER-BOX

Well, you all know what this is? It is a box of matches. And you know, moreover, what it is used for, and how to use it. I will take out one of the matches, rub it on the box, and "strike a light." You say that experiment is commonplace enough. Be it so. At any rate, I want you to recollect that phrase--"strike a light." It will occur again in our course of lectures. But, you must know, there was a time when people wanted fire, but had no matches wherewith to procure it. How did they obtain fire? The necessity for, and therefore the art of producing, fire is, I should suppose, as old as the world itself. Although it may be true that our very earliest ancestors relied for necessary food chiefly on an uncooked vegetable diet, nevertheless it is certain that very early in the history of the world people discovered that cooked meat was a thing not altogether to be despised. Certainly by the time of Tubal Cain, an early worker in metals, not only the methods of producing fire, but also the uses to which fire could be applied, must have been well understood. Imagine the astonishment of our ancestors when they first saw fire! Possibly, the first sight of this wonderful "element" vouchsafed to mortals was a burning mountain, or something of that kind. One is scarcely astonished that there should have been in those early times a number of people who were professed fire-worshippers. No wonder, I say, that fire should have been regarded with intense reverence. It constituted an essential part of early sacrificial worship. Some of my young friends, too, may remember how in ancient Rome there was a special order , whose duty it was to preserve the sacred fire, which if once extinguished, it was thought would bring ruin and destruction upon their city.

Talking about friction as a means of producing heat, I should like to mention that at the last Paris Exhibition I saw water made to boil, and coffee prepared from it, by the heat resulting from the friction of two copper plates within the liquid.

That then is the earliest history I can give you of the production of fire, and at once from that history I come to the reign of the tinder-box. The tinder-box constitutes one of the very earliest methods, no doubt, of obtaining fire. I have searched for some history of the tinder-box, and all I can say for certain is that it was in use long before the age of printing. I have here several rare old tinder-boxes. I intend showing you in the course of these lectures every detail of their construction and use. I have no doubt this very old tinder-box that you see here was once upon a time kept on the mantel-piece of the kitchen well polished and bright, and I do not doubt but that it has lit hundreds and thousands of fires, and, what is more, has very often been spoken to very disrespectfully when the servant wanted to light the fire, and her master was waiting for his breakfast. I will project a picture of it on the screen, so that you may all see it. There it is. It is a beautiful piece of apparatus. There is the tinder, the steel , the flint , and the matches complete.

It was with this instrument, long before the invention of matches, that our grandfathers obtained light. I want to show you how the trick was managed. First of all it was necessary to have good tinder. To obtain this, they took a piece of linen and simply charred or burnt it, as you see I am doing now . The servants prepared the tinder over-night, for reasons I shall explain to you directly. Having made the tinder, they shut it down in the box with the lid to prevent contact with air. You see I have the tinder now safely secured in my tinder-box. Here is a piece of common flint, and here is the steel. Here too are the matches, and I am fortunate in having some of the old matches made many years ago, prepared as you see with a little sulphur upon their tips. Well, having got all these etceteras, box, tinder, flint and steel, we set to work in this way:--Taking the steel in one hand, and the flint in the other, I must give the steel a blow, or rather a succession of blows with the flint . Notice what beautiful sparks I obtain! I want one of these sparks, if I can persuade it to do so, to fall on my tinder. There! it has done so, and my tinder has caught fire. I blow my fired tinder a little to make it burn better, and now I apply a sulphur match to the red-hot tinder. See, I have succeeded in getting my match in flame. I will now set light to one of these old-fashioned candles--a rushlight--with which our ancestors were satisfied before the days of gas and electric lighting. This was their light, and this was the way they lighted it. No wonder that they went to bed early.

I should like to draw your attention to one other form of tinder-box, because I do not suppose you have ever seen these kind of things before. I have here two specimens of the pistol form of tinder-box . Here is the flint, the tinder being contained in this little box. It is the same sort of tinder as we made just now. The tinder was fired with flint and steel in the same way as the old-fashioned flint pistols fired the gunpowder. And you see this pistol tinder-box is so constructed as to serve as a candlestick as well as a tinder-box. I have fired, as you perceive, my charred linen with this curious tinder-box, and thus I get my sulphur match alight once more!

Shortly after phosphorus had been discovered, people came to the conclusion that it might be employed for the purpose of procuring artificial light. But I want you to note, that although phosphorus was discovered in 1669 , it was not until the year 1833 that phosphorus matches became a commercial success, so that until the year 1833, our old friend the tinder-box held its ground. I will try and give you as nearly as I can a complete list of the various attempts made with the purpose of procuring fire between the years 1669 and 1833.

The first invention was what were called "phosphoric tapers." From the accounts given , phosphoric tapers seem to have been sulphur matches with a little piece of phosphorus enclosed in glass fixed on the top of the match, the idea being that you had only to break the glass and expose the phosphorus to air for it to catch fire immediately and ignite the sulphur. If this was the notion , it is not easy to understand how the phosphoric tapers were worked. The second invention for the purpose of utilizing phosphorus for getting fire was by scraping with a match a little phosphorus from a bottle coated with a phosphorus composition, and firing it by friction. The fact is, phosphorus may be easily ignited by slight friction. If I wrap a small piece of phosphorus in paper, as I am doing now, and rub the paper on the table, you see I readily fire my phosphorus.

After this, "Homberg's Pyrophorus," consisting of a roasted mixture of alum and flour, was suggested as a means of obtaining fire. Then comes the "Electrophorus," an electrical instrument suggested by Volta, which was thought at the time a grand invention for the purpose of getting light . The nuisance about this instrument was that it proved somewhat capricious in its action, and altogether declined to work in damp foggy weather. I do not know whether I shall be successful in lighting a gas-jet with the electrophorus, but I will try. I excite this plate of resin with a cat-skin , then put this brass plate upon the resin plate and touch the brass ; then take the brass plate off the resin plate by the insulating handle and draw a spark from it, which I hope will light the gas. There, I have done it!

Well, next after the electrophorus comes the "fire syringe" . The necessary heat in this case is produced by the compression of air. You see in this syringe stopped at one end, I have a certain quantity of air. My piston-rod fits very closely into the syringe , so that the air cannot escape. If I push the piston down I compress the air particles, for they can't get out;--I make them in fact occupy less bulk. In the act of compressing the air I produce heat, and the heat, as you see, fires my tinder.

It was in or about the year 1807 that "chemical matches" were introduced to the public for the first time. These chemical matches were simply sulphur matches tipped with a mixture of chlorate of potash and sugar. These matches were fired by dipping them in a bottle containing asbestos moistened with sulphuric acid. Here is one of these "chemical matches," and here the bottle of asbestos and sulphuric acid. I dip the match into the bottle and, as you see, it catches fire.

In the year 1820, Dobereiner, a very learned man, discovered a method of getting fire by permitting a jet of hydrogen to play upon finely-divided platinum. The platinum, owing to a property it possesses in a high degree , has the power of coercing the union of the hydrogen and oxygen. Here is one of Dobereiner's original lamps . I am going to show you the experiment, however, on a somewhat larger scale than this lamp permits. Here I have a quantity of fine platinum-wire, made up in the form of a rosette. I place this over the coal-gas as it issues from the gas-burner, and, as you see, the platinum begins to glow, until at last it becomes sufficiently hot to fire the gas .

In the year 1826 what were called "lucifers" were invented, and I show you here some of the original "lucifers." They are simply sulphur matches tipped with a mixture of chlorate of potash and sulphide of antimony, and were ignited by drawing them briskly through a little piece of folded glass-paper.

In the year 1828, "Prometheans" were invented. I have here two of the original "Prometheans." They consist of a small quantity of chlorate of potash and sugar rolled up tightly in a piece of paper. Inside the paper roll is placed a small and sealed glass bubble containing sulphuric acid. When it was wanted to light a "Promethean" you had only to break the bulb of sulphuric acid, the action of which set fire to the mixture of chlorate of potash and sugar, which ignited the paper roll.

In the year 1830 "matches" with sulphur tips were introduced as a means of obtaining fire. They were fired, so far as I can make out, by dipping them into a bottle containing a little phosphorus, which then had to be ignited by friction.

So far as I know, I have now given you very shortly the history of obtaining fire between the years 1669 and 1830. You see how brisk ingenuity had been during this long period, and yet nothing ousted our old friend the tinder-box. The tinder-box seems, as it were, to speak to us with a feeling of pride and say, "Yes, all you have been talking about were the clever ideas of clever men, but I lived through them all; my flint and my steel were easily procured, my ingredients were not dangerous, and I was fairly certain in my action."

In the year 1833 the reign of the tinder-box came to an end. It had had a very long innings--many, many hundred years; but in 1833 its reign was finished. It was in this year the discovery was announced, that bone could be made to yield large quantities of phosphorus at a cheap rate. Originally the price of phosphorus was sufficient to prevent its every-day use. Hanckwitz thus advertises it--"For the information of the curious, he is the only one in London who makes inflammable phosphorus that can be preserved in water. All varieties unadulterated. Sells wholesale and retail. Wholesale, 50s. per oz.; retail, ?3 sterling per oz. Every description of good drugs. My portrait will be distributed amongst my customers as a keepsake."

Now, then, comes a very remarkable story to which I desire to draw your attention. There were many disadvantages in the use of this yellow phosphorus. First of all, it is a poisonous substance; and what is more, the vapour of the phosphorus was liable to affect the workpeople engaged in the manufacture of lucifer matches with a bad disease of the jaw, and which was practically, I am afraid, incurable. A very great chemist, Schr?tter, discovered that phosphorus existed under another form, some of which I have here. This, which is of a red colour, was found to be exactly the same chemical substance as the yellow phosphorus, but possessing in many respects different properties. For instance, you see I keep this yellow phosphorus under water; I don't keep the red phosphorus in water. Amongst other peculiarities it was found that red phosphorus was not a poison, whilst the yellow phosphorus was, as I told you, very poisonous indeed. About two to three grains of yellow phosphorus is sufficient to poison an adult. I have known several cases of children poisoned by sucking the ends of phosphorus matches. So you see it was not unimportant for the workpeople, as well as for the public generally, that something should be discovered equally effective to take the place of this poisonous yellow phosphorus.

I should like to show you what very different properties these two kinds of phosphorus possess. For instance, if I take a small piece of the yellow phosphorus and pour upon it a little of this liquid--bi-sulphide of carbon--and in another bottle treat the red phosphorus in a similar way, we shall find the yellow phosphorus is soluble in the liquid, whilst the red is not. I will pour these solutions on blotting-paper, when you will find that the solution of the yellow phosphorus will before long catch fire spontaneously , whilst the solution of the red phosphorus will not fire . Again, if I add a little iodine to the yellow phosphorus, you see it immediately catches fire ; but the same result does not follow with the red phosphorus . I will show you an experiment, however, to prove, notwithstanding these different properties, that this red and yellow material are the same elementary body. I will take a little piece of the yellow phosphorus, and after igniting it introduce it into a jar containing oxygen, and I will make a similar experiment with the red phosphorus. You will notice that the red phosphorus does not catch fire quite so readily as the yellow. However, exactly the same result takes place when they burn--you get the same white smoke with each, and they combust equally brilliantly. The red and yellow varieties are the same body--that is what I want to show you--with different properties.

Then comes the next improvement in the manufacture of matches, which is putting the phosphorus on the box and not on the match. This is why the use of red phosphorus, was introduced into this country by Messrs. Bryant and May. I have no doubt that many a good drawing-room paper has been spared by the use of matches that light only on the box.

I cannot help thinking that the old tinder-box, which I have placed on the table in a prominent position before you to-night, feels a certain pleasure in listening to our story. Envious perhaps a little of its successor, it nevertheless fully recognizes that its own reign had been a thousand times longer than that of the lucifer match. If we could only hear that tinder-box talk, I think we should find it saying something of this kind to the lucifer match--"I gave way to you, because my time was over; but mind, your turn will come next, and you will then have to give way to something else, as once upon a time I had to give way to you." And that is the end of the first chapter of my story of a tinder-box.

We were engaged in our last lecture in considering the various methods that have been adopted from early times for obtaining fire, and we left off at the invention of the lucifer match. I ventured to hint at the conclusion of my last lecture, that the tinder-box had something to say to the lucifer match, by way of suggestion, that just as the lucifer match had ousted it, so it was not impossible that something some day might oust the lucifer match. Electricians have unlimited confidence in the unlimited applications of electricity:--they believe in their science. Now one of the effects of electricity is to cause a considerable rise of temperature in certain substances through which the electrical current is passed. Here is a piece of platinum wire, for example, and if I pass an electrical current through it, you see how the wire glows . If we were to pass more current through it, which I can easily do, we should be able to make the platinum wire white hot, in which condition it would give out a considerable amount of light. There is the secret of those beautiful incandescent glow lamps that you so often see now-a-days . Instead of a platinum wire, a fine thread of carbon is brought to a very high temperature by the passage through it of the electrical current, in which condition it gives out light. All that you have to do to light up is to connect your lamp with the battery. The reign of the match, as you see, so far as incandescent electric lamps are concerned, is a thing of the past. We need no match to fire it. Here are various forms of these beautiful little lamps. This is, as you see, a little rosette for the coat. Notice how I can turn the minute incandescent lamp, placed in the centre of the rose, off or on at my pleasure. If I disconnect it with the battery, which is in my pocket, the lamp goes out; if I connect it with my battery the lamp shines brilliantly. This all comes by "switching it on" or "switching it off," as we commonly express the act of connecting or disconnecting the lamp with the source of electricity.

Here is another apparatus to which I desire to call your attention. If I take a battery such as I have here--a small galvanic battery of some ten cells--you will see a very little spark when I make and break contact of the two poles. This is what is called an electrical torch, in which I utilize this small spark as a gas-lighter . This instrument contains at its lower part a source of electricity, and if I connect the two wires that run through this long tube with the apparatus which generates the current, which I do by pressing on this button, you see a little spark is at once produced which readily sets fire to my gas-lamp. We have in this electrical torch a substitute--partial substitute, I ought to say--for the lucifer match. I think you will admit that it was with some show of reason I suggested that after all it is possible the lucifer match may not have quite so long an innings as the tinder-box. But there is another curious thing to note in these days of great scientific progress, viz. that there are signs of the old tinder-box coming to the front again. Men, I have often noticed, find it a very difficult thing to light their pipes with a match on the top of an omnibus on a windy day, and inventors are always trying to find out something that will enable them to do so without the trouble and difficulty of striking a match, and keeping the flame a-going long enough to light their cigars. And so we have various forms of pipe-lighting apparatus, of which here is one--which is nothing more than a tinder-box with its flint and steel . You set to work somewhat in this way: placing the tinder on the flint , you strike the flint with the steel , and--there, I have done it!--my tinder is fired by the spark. So you see there are signs, not only of the lucifer match being ousted by the applications of electricity, but of the old tinder-box coming amongst us once again in a new form.

But to proceed. What do I want now? I want a spark to fire my tinder. A spark is enough. Do you remember the motto of the Royal Humane Society? Some of my young friends can no doubt translate it, "Lateat scintilla forsan"--perchance a spark may lie hid. If a person rescued from drowning has but a spark of life remaining, try and get the spark to burst into activity. That is what the motto of that excellent society means. How am I to get this spark from the flint and steel to set fire to my tinder? I take the steel in one hand, as you see, and I set to work to strike it as vehemently as I can with the flint which I hold in the other . Spark follows spark. See how brilliant they are! But I want one spark at least to fall on my tinder. There, I have succeeded, and it has set fire to my tinder. One spark was enough. The spark was obtained by the collision of the steel and flint. The sparks produced by this striking of flint against steel were formerly the only safe light the coal-miner had to light him in his dark dreary work of procuring coal. Here is the flint and steel lamp which originally belonged to Sir Humphry Davy . The miners could not use candles in coal-mines because that would have been dangerous, and they were driven to employ an apparatus consisting of an iron wheel revolving against a piece of flint for the purpose of getting as much light as the sparks would yield. This instrument has been very kindly lent to me by Professor Dewar. I will project a picture of the apparatus on the screen, so that those at a distance may be better able to see the construction of the instrument.

I want you then to realize this great fact, that when I hold the steel and strike it with the flint, and get sparks, I first of all knock off a minute fragment of iron by the blow that I impart to it, whilst the force I use in striking the blow actually renders the little piece of detached iron red-hot. What a wonderful thought this is! Look at the sun, the great centre of heat! It looks as if it were a blazing ball of fire in the heavens. Where does the heat of the sun come from? It seems bold to suggest that the heat is produced by the impact of meteorites on the sun. Just as I, for instance, take a hammer and heat the nail by the dash of the hammer on it, so the dash of these meteorites on the sun are supposed to produce the heat so essential to our life and comfort.

Recall for a few minutes the facts I brought before you in my last lecture. The first point we discussed was the preparation of the tinder. I explained to you that tinder was nothing more than carbon in a finely-divided state. The second point was, that I had to strike the steel with the flint in such manner that a minute particle of the iron should be detached; the force used in knocking it off being sufficient to make the small particle of iron red-hot. This spark falling upon the tinder set fire to it. The next stage of the operation was to blow upon the tinder, in order, as I said, to nourish the flame; in other words, to promote combustion by an increased supply of oxygen, just as we use an ordinary pair of bellows for the purpose of fanning a fire which has nearly gone out into a blaze.

But let us go a step further: why must the solid sulphur be converted into a gas? We want a flame, and whenever we have flame it is absolutely necessary that we should have a gas to burn. You cannot have flame without you have gas. Let me endeavour to illustrate what I mean. I pour into this flask a small quantity of ether, a liquid easily converted into a gas. If I apply a lighted taper to the mouth of the flask, no gas, or practically none, being evolved at the moment, nothing happens. But I will heat the ether so as to convert it into a gas. And now that I have evolved a large quantity of ether gas, when I apply a lighted taper to the mouth of the flask I get a large flame . There it is! The more gas I evolve the larger is the flame. You see it is a very large flame now. If I take the spirit lamp away, the production of gas grows less and less, until my flame almost dies out; but you see if I again apply my heat and set more gas free, I revive my flame. I want you to grasp this very important fact, upon which I cannot enlarge further now, that given flame, I must have a gas to burn, and therefore heat as a power is needed before I can obtain flame.

Well, you ask me, is that true of all flame? Where is the gas, you say, in that candle flame? Think for a moment of the science involved in lighting a candle. What am I doing when I apply a lighted match to this candle? The first thing I do is to melt the tallow, the melted tallow being drawn up by the capillarity of the wick. The next thing I do is to convert the liquid tallow into a gas. This done, I set fire to the gas. I don't suppose you ever thought so much was involved in lighting a candle. My candle is nothing more than a portable gas-works, similar in principle to the gas-works from which the gas that I am burning here is supplied. Whether it is a lamp, or a gas-burner, or a candle, they are all in a true sense gas-works, and they all pre-suppose the application of heat to some material or another for the purpose of forming a gas which will burn.

Before I pass on, I want to refer to the beautiful burner that I have here. It is the burner used by the Whitechapel stall-keepers on a Saturday night . Just let me explain the science of the Whitechapel burner. First of all you will see the man with a funnel filling this top portion with naphtha . Here is a stop-cock, by turning which he lets a little naphtha run down the tube through a very minute orifice into this small cup at the bottom of the burner . This cup he heats in a friend's lamp, thereby converting the liquid naphtha, which runs into the cup, into a gas. So soon as the gas is formed--in other words, so soon as the naphtha has been sufficiently heated--the naphtha gas catches fire, the heat being then sufficient to maintain that little cup hot enough to keep up a regular supply of naphtha gas. When the lamp does not burn very well, you will often see the man poking it with a pin. The carbon given off from the naphtha is very disposed to choke up the little hole through which the naphtha runs into the cup, and the costermonger pushes a pin into the little hole to allow the free passage of the naphtha. That, then, is the mechanism of this beautiful lamp of the Whitechapel traders, known as Halliday's lamp.

I showed you the steel and flint lamp--if I may call it a lamp--used by coal-miners at the time of Davy . Davy set to work to invent a more satisfactory lamp than that, and the result of his experiments was the beautiful miner's lamp which I have here . I regard this lamp with considerable affection, because I have been down many a coal-mine with it. This is the coal-miner's safety-lamp. The old-fashioned form of it that I have here has been much improved, but it illustrates the principle as well as, if not better than, more elaborate varieties. It is simply an oil flame covered with a gauze shade, exactly like that gauze with which I have been experimenting. I will allow a jet of coal gas to play upon this lamp, but the gas, as you see, does not catch fire. You will notice the oil flame in the lamp elongates in a curious manner. The flame of the lamp cooled by the gauze is not hot enough to set fire to the coal gas, but the appearance of the flame warns the miner, and tells him when there is danger. And that is the explanation of the beautiful miner's safety-lamp invented by Sir Humphry Davy.

Now let me once more put this fact clearly before you, that whether it is the gas flame or our farthing rushlight, whether it is our lamp or our lucifer match, if we have a flame we must have a gas to burn, and having a gas, we must heat it to, and maintain it at, a certain temperature. We have now reached a point where our tinder-box has presented us with flame. A flame is indeed the consummated work of the tinder-box.

Just let me say a few words about the grand result--the consummated work of the tinder-box. A flame is a very remarkable thing. It looks solid, but it is not solid. You will find that the inside of a flame consists of unburnt gas--gas, that is to say, not in a state of combustion at all. The only spot where true combustion takes place is the outer covering of the flame. I will try to show you some experiments illustrating this. I will take a large flame for this purpose. Here is a piece of glass tube which I have covered with ordinary white paper. Holding the covered glass tube in our large flame for a minute or two, you observe I get two rings of charred paper, corresponding to the outer envelope of the flame, whilst that portion of the paper between the black rings has not even been scorched, showing you that it is only the outer part of the flame that is burning . The heat of the flame is at that part where, as I said before, the combustible gases come into contact--into collision with the atmosphere. So completely is this true, that if I take a tube, such as I have here, I can easily convey the unburnt gas in the centre of the flame away from the flame, and set fire to it, as you see, at the end of the glass tube a long distance from the flame . I will place in the centre of my flame some phosphorus which is at the present moment in a state of active burning, and observe how instantly the combustion of the phosphorus ceases so soon as it gets into the centre of the flame. The crucible which contains it is cooled down immediately, and presents an entirely different appearance within the flame to what it did outside the flame. It is a curious way, perhaps you think, to stop a substance burning by putting it into a flame. Indeed I can put a heap of gunpowder inside a flame so that the outer envelope of burning gas does not ignite it . There you see a heap of gunpowder in the centre of our large flame. The flame is so completely hollow that even it cannot explode the powder.

I want you, if you will, to go a step further The heat of the flame is due, as I explained in my last lecture, to the clashing of molecules. But what is the light of my candle and gas due to? The light is due to the solid matter in the flame, brought to a state of white heat or incandescence by the heat of the flame. The heat is due to the clashing of the particles, the light is due to the heated solid matter in the flame. Let me see if I can show you that. I am setting free in this bottle some hydrogen, which I am about to ignite at the end of this piece of glass tube . I shall be a little cautious, because there is danger if my hydrogen gets mixed with air. There is my hydrogen burning; but see, it gives little or no light. But this candle flame gives light. Why? The light of the candle is due to the intensely heated solid matter in the flame; the absence of light in the hydrogen flame depends on the absence of solid matter. Let me hold clean white plates over both these flames. See the quantity of black solid matter that I am able to collect from this candle flame . But my hydrogen yields me no soot or solid matter whatsoever . The plate remains perfectly clean, and only a little moisture collects upon it. The light that candle gives depends upon the solid matter in the flame becoming intensely heated. If what I say be true, it follows that if I take a flame which gives no light, like this hydrogen flame , and give it solid particles, I ought to change the non-luminous flame into a luminous one. Let us see whether this be so or not. I have here a glass tube containing a little cotton wadding , and I am about to pour on the wadding a little ether, and to make the hydrogen gas pass through the cotton wadding soaked with ether before I fire it. And now if what I have said is correct, the hydrogen flame to which I have imparted a large quantity of solid matter ought to produce a good light, and so it does! See, I have converted the flame which gave no light into a flame which gives an excellent light merely by incorporating solid matter with the flame . What is more, the amount of light that a flame gives depends upon the amount or rather the number of solid particles that it contains. The more solid particles there are in the flame, the greater is the light. Let me give you an illustration of this. Here is an interesting little piece of apparatus given to my predecessor in the chair of chemistry at the London Hospital by the Augustus Harris of that day. It is one of the torches formerly used by the pantomime fairies as they descended from the realms of the carpenters. I have an alcohol flame at the top of the torch which gives me very little light. Here, you see, is an arrangement by which I can shake a quantity of solid matter into the non-luminous alcohol flame. You will observe what a magnificently luminous flame I produce .

I have told you that the light of a flame is due to solid matter in the flame; further, that the amount of light is due to the amount of solid matter. And now I want to show you that the kind of light is due to the kind of solid matter in the flame. Here are some pieces of cotton wadding, which I am about to saturate with alcoholic solutions of different kinds of solid matter. For instance, I have in one bottle an alcoholic solution of a lithium salt, in another of a barium, in a third of a strontium, and so on. I will set fire to all these solutions, and you see how vastly different the colours are, the colour of the flames being dependent on the various forms of solid matter that I have introduced into them.

I have not forgotten Frankland's experiments on this subject, but the lectures did not admit of dealing with exceptional cases.

Thus I have shown you that the heat of our flame is due to the clashing of the two gases, and the light of the flame to the solid matter in the flame, and the kind of light to the kind of solid matter.

Well, there is another point to which I desire to refer. Light is the paint which colours bodies. You know that ordinary white light is made up of a series of beautiful colours , which I show you here. If I take all these spectrum or rainbow colours which are painted on this glass I can, as you see, recompose them into white light by rotating the disc with sufficient rapidity that they may get mixed together on the little screen at the back of your eye. White light then is a mixture of a number of colours.

Just ask yourselves this question. Why is this piece of ribbon white? The white light falls upon it. White light is made up of all those colours you saw just now upon the screen. The light is reflected from this ribbon exactly as it fell upon the ribbon. The whole of those colours come off together, and that ribbon is white because the whole of the colours of the spectrum are reflected at the same moment. Why is that ribbon green? The white light falls upon the ribbon--the violet, the indigo, the red, the blue, the orange, and the yellow, are absorbed by the dye of the ribbon, and you do not see them. The ribbon, as it were, drinks in all these colours, but it cannot drink in the green. And reflecting the green of the spectrum, you see that ribbon green because the ribbon is incapable of absorbing the green of the white light. Why is this ribbon red? For the same reason. It can absorb the green which the previous piece of ribbon could not absorb, but it cannot absorb the red. The fact is, colour is not an inherent property of a body. If you ask me why that ribbon is green, and why this ribbon is red, the real answer is, that the red ribbon has absorbed every colour except the red, and the green ribbon every colour except the green, not because they are of themselves red and green but because they have the power of reflecting those colours from their surfaces.

This then is the consummated work of our tinder-box. Our tinder-box set fire to the match, and the match set fire to the candle, whilst the heat and the light of the candle are the finished work of the candle that the tinder-box lighted.

The clock warns me that I must bring to an end my story of a tinder-box. To be sure, the tinder-box is a thing of the past, but I hope its story has not been altogether without teaching. Let me assure you that the failure, if failure there be, is not the fault of the story, but of the story-teller. If some day, my young friends, you desire to be great philosophers--and such desire is a high and holy ambition--be content in the first instance to listen to the familiar stories told you by the commonest of common things. There is nothing, depend upon it, too little to learn from. In time you will rise to higher efforts of thought and intellectual activity, but you will be primed for those efforts by the grasp you have secured in your studies of every-day phenomena.

"Great things are made of little things, And little things go lessening, till at last Comes God behind them."

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