Charles Meymott Tidy

“ Oxygen is the spark's nourishment and life, and the more it gets the better it thrives. Oxygen is an extremely active agent in nourishing flame. If, for instance, I take a little piece of carbon and merely set fire to one small corner of it, and then introduce it into this jar of oxygen, see how brilliantly it burns; you notice how rapidly the carbon is becoming consumed (Fig. 26) . In the tinder-box I blow on the tinder to supply a larger amount of oxygen to my spark. A thing to burn under ordinary conditions must have oxygen, and the more oxygen it gets the better it burns. ”

“ I want almost—not quite—actual flame to fire coal gas. But here is another gas, about which I may have to say something directly, called marsh gas (the gas of coal-mines) . This requires a much higher temperature than even coal gas to fire it. I want you to understand that although all gases require heat to fire them, different gases ignite at very different temperatures. Bisulphide of carbon gas, e. g., ignites at a very low temperature, whilst marsh gas requires a very high temperature indeed for its ignition. You will see directly that this is a very important fact. ”

“ Carbon is an element; you can get nothing out of carbon but carbon. You can combine it with other things, but if you have only carbon you can get nothing out of the carbon but carbon. But this carbon is found to exist in very different states or conditions. For instance, it is found in the form of the diamond. (Fig. 18 a) . Diamonds consist of nothing more nor less than this simple elementary body—carbon. It is a very different form of carbon, no doubt you think, to tinder. Just let me tell you, to use a very hard word, that we call the diamond an "allotropic" form of carbon. ”

“ 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 (Fig. 17) . ”

“ 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. ”

“ 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 (I can assure you) in the unlimited applications of electricity:—they believe in their science. ”

“ Now, when I take a piece of fine gauze, the flame does not pass through at all until the gauze is nearly red-hot. There is plenty of gas passing all the time. If I take a still finer gauze, I shall find that the flame won't pass even when it is almost red-hot (Fig. 32 B) . Plenty of gas is passing through, remember, all the time, but the flame does not pass through. Now why is it that the flame is unable to pass? The reason is this—because the metal gauze has so cooled the flame that the heat on one side is not sufficient to set fire to the gas on the other side. ”

“ 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. ”

“ One single experiment knocked it on the head. It was certain, that in water there is a great deal more entrapped heat—"latent heat" it was called—than there is in ice. If you take two pieces of ice and rub them together, you will find the ice melts—the solid ice changes (that is to say) into liquid water. Where did the heat come from to melt the ice? You could not get the heat from the ice, because it was not there, there being admittedly more latent heat in the water than in the ice. The explanation is certain—the heat was the result of the friction. ”

“ The solid sulphur could not catch fire. Therefore the heat of my tinder during the interval that I was coaxing the match (as I called it) was being exerted in converting my solid into gaseous sulphur. When the solid sulphur had had sufficient heat applied to it to vapourize it, the sulphur gas immediately caught fire. Now understand, that in order to convert a solid into a liquid, or a liquid into a gas, heat is always a necessity. I must have heat to produce a gas out of a solid or a liquid. I will endeavour to make this clear to you by an experiment. ”

“ 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. ”

“ I told you that in England we generally use chlorate of potash in the preparation of the phosphorus composition, whilst abroad nitrate of potash is usually employed. You know that when we strike a light with an English match a slight snap results, which is due to the chlorate of potash in the match. In the case of nitrate of potash no such snapping noise occurs. Some people are wicked enough to call them "thieves' matches." Just let me show you (in passing) how a mixture of chlorate of potash and sulphur explodes when I strike it. ”

“ The friction produces heat, the heat fires the fulminate, and off it goes with a crack. And now put this question to yourselves, What produced the friction? Force. What is more, the amount of heat produced is the exact measure of the amount of force used. Heat is a form of force. ”

“ 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. ”

“ 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. ”

“ The carpenter finds sawing hard work, and he does not want the force of the muscles of his arm—his labour, in short—to be converted into heat, and so he greases the saw, knowing that the more completely he prevents friction, the more wood he will cut. It is the force of steam that makes the engine travel. Steam costs money. The engine-driver does not want that steam-force to be converted into heat, because every degree of heat produced means diminished speed of his train ”

“ Only powder the lead sufficiently fine,—that is to say, bring it into a state of minute subdivision,—and it fires by contact with the oxygen of the air. And now apply this. We have in our diamond the element carbon, but diamond-carbon is a hard substance, and not in a finely-divided state. We have in this tinder the same substance as the diamond, but tinder-carbon is finely divided, and it is because it is in a finely-divided condition that the carbon in our tinder-box catches fire so readily. ”

“ 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. ”

“ Considerable friction results between the wheel and the brake;—heat is produced;—the train gradually comes to a stop. Why? We have now the conversion of that force into heat which a minute ago was being used for the purpose of keeping the train a-going. Given a certain force you can have heat or motion; but you cannot have heat and motion with the same force in the same amount as if you had them singly. In every-day life, you cannot have your pudding and eat it. ”

“ The platinum, owing to a property it possesses in a high degree (which property however is not special to platinum) , has the power of coercing the union of the hydrogen and oxygen. Here is one of Dobereiner's original lamps (Fig. 8) . 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 (Fig. 9) . ”

“ I take the steel and the flint, and striking them together I get sparks. I want you to ask yourselves, Where do the sparks come from? Each spark is due to a minute piece of iron being knocked off the steel by the blow of flint with steel. Note the precise character of the spark. Let me sprinkle some iron filings into this large gas flame. You will notice that the sparks of burning iron filings are very similar in appearance to the spark I produce by the collision of my flint and steel. ”

“ What I want you to understand is, that although I have in both these cases precisely the same chlorine and the same metal, nevertheless, that whilst the action of the chlorine on the lump of antimony was not very apparent, in the case of the powdered antimony the action was very energetic. Again, there is a lump of lead (Fig. 21 a) . You would be very much astonished if the lead pipe that conveys the water through your houses caught fire spontaneously; but let me tell you that, if your lead water-pipes were reduced to a sufficiently fine powder, they would catch fire when exposed to the air. ”

“ Diamond, black-lead, and tinder are allotropic forms of carbon, just as I explained to you in my last lecture, that the elementary body phosphorus was also known to exist in two forms, the red and the yellow variety, each having very different properties. ”

“ For instance, if you were to put a copper rod and a glass rod into the fire, allowing a part of each to project, the copper rod that projects out of the fire would soon become so very hot that you dare not touch it, owing to the copper conducting the heat from the fire, whereas you would be able to take hold of the projecting end of the glass rod long after the end of the glass exposed to the fire had melted. ”

“ 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. ”

“ Black-lead—or, as we term it, graphite—of which I have several specimens here—is simply carbon—an allotrope of carbon—the same elementary substance, notwithstanding, as the diamond. This black-lead (understand black-lead, as it is called, contains no metallic lead) is used largely for making lead-pencils. The manufacture of lead-pencils, by the bye, is a very interesting subject. Formerly they cut little pieces of black-lead out of lumps of the natural black-lead such as you see there; but now-a-days they powder the black-lead, and then compress the very fine powder into a block. ”

“ You remember, too, perhaps reading about Prometheus, who stole fire from heaven, bringing it to earth in a copper rod, which combined act of theft and scientific experiment made the gods very angry, because they were afraid mortals might learn as many wonderful things as they knew themselves. History seems to show that the energetic rubbing together of dry sticks was one of the earliest methods adopted by our ancestors for producing fire. ”