Part 34
When soft coal is heated in a closed receptacle a gas is formed which will burn. To show this we have only to take an ordinary clay pipe, put a little piece of coal in the bowl, close the top with wet clay, and put the bowl part of the pipe in the fire. When it is quite hot, a gas will be found coming out of the stem of the pipe, which will, when lighted, burn.
The Story In a Gas Jet.
~HOW ILLUMINATING GAS IS MADE~
Soft coal is heated in large tubes of fire clay called retorts, and the gas that is formed is then collected in a large tank and sent through pipes to our homes after being purified. The part of the coal that is left consists largely of carbon and is what we call coke.
While the gas that comes directly from coal will burn if lighted, it is not a desirable gas to burn in our homes, because it contains a number of substances that should be eliminated before it is used for lighting.
How the Gas Is Purified.
From the clay retorts the gas passes through horizontal pipes containing water. This cools it and takes out of it most of the tar and water vapor that are driven off with the gas when formed. These substances settle in the water. The gas then goes through a series of curved pipes, which are air cooled. These pipes constitute what is known as an atmospheric condenser. From these the gas goes into a series of receptacles containing wooden slat trays, made up like screens. These receptacles are called the scrubbers, and they take out of the gas the last traces of tar and some of the other compounds found present. The removal of the sulphur is very important, for burning sulphur gives off a gas which is not only extremely impure to breathe, but also injurious to the health.
From the scrubbers the gas goes on through pipes to the purifiers--boxes which contain wood shavings coated with iron rust upon which the sulphur is deposited by chemical action. At the same time the lime absorbs a small quantity of carbonic acid gas, which is formed with the other gases. From the purifiers the gas passes into the great iron tanks, in which it is stored until needed.
The gas in the tanks consists chiefly of hydrogen, a number of compounds of hydrogen and carbon, and a small amount of a compound of carbon and oxygen containing less oxygen than carbonic acid gas, known as carbon monoxide. The hydrogen and carbon monoxide burn with a very pale flame, which gives but little light and much heat. The light-giving quality of the gas is found in the compounds of carbon and hydrogen. When these burn, the particles of carbon are heated white hot and glow very brightly, making a luminous flame.
There are, of course, some impurities in the purified gas. These are compounds containing sulphur and ammonia. The quantities of these substances, however, are so small that they are harmless; but the compounds taken out in the process of purifying the gas are saved, as considerable use is made of them. The water used for washing the gas is heavily charged with ammonia and is, in fact, the chief source of the ammonia sold by druggists.
[Illustration: HOW THE IMPURITIES ARE TAKEN FROM THE GAS
PURIFYING BOXES.
The principal impurity to be removed is sulphur, and this is accomplished by passing the gas through large iron rectangular boxes filled with wood shavings coated with iron rust upon which the sulphur is deposited by chemical action.]
[Illustration: STATION METER HOUSE, SHOWING CONSTRUCTION OF TWO NEW 13-FT. METERS.]
[Illustration: HOW THE METER MEASURES THE GAS
Fig 1
Fig 3
Fig. 2.
Fig 4
Gas first enters inlet pipe _A_ (Fig. 3) passing along _A1_ into covered valve chamber _B_ up through orifice _O_. It then passes down through two of the valve ports at the same time, ports _C_ and _D1_ (Fig. 2). Before _C1_ (Fig. 3) has gotten to its extreme opening, the valve on the opposite side has moved to allow gas to pass down port _D_. On every quarter turn of tangent _P_, one port is opening to receive gas which passes down through the valve ports into the chambers below (see arrows on Fig. 2), which shows the gas passing into chamber _F_. The pressure being greater on the outside of the diaphragm, forces the diaphragm inward and expels the gas from the inside of _D2_ through _D_ and passes over the cross-bar into the fork channel (see Fig. 1). On the other side gas is passing down through port _D1_ (Fig. 2) entering diaphragm _D3_, the pressure being greater on the inside of _D3_ therefore forces the diaphragm outward and expels the gas from the outside of diaphragm _D3_; out through port _C1_ into fork channel same as shown in (Fig. 1). All exhaust gas from the chambers below is checked from entering the chamber _B_ by the slide valve _G_ and _G1_ (Fig. 2). Instead of passing into chamber _B_ it passes over the cross-bars between _D1E1_ and _C1E1_ into the fork channels, then to outlet pipe _N_ (Fig. 3) to house pipe.
NOTE: All gas registered must pass through outlet _N_.]
In addition to coal gas made in the way just described, there is another form of illuminating gas, in the manufacture of which coal is indirectly employed. This gas, known as water gas, because it is formed by the decomposition of water, is produced by passing steam over red hot carbon, in the form of hard coal or coke. When this is done, the hydrogen in the steam is set free and the oxygen combines chemically with the carbon, to form the carbon monoxide, that was mentioned as being present, in small proportions, in ordinary coal gas. This carbon monoxide is poisonous, if much of it is breathed, and as it has no odor it is difficult to detect when escaping. A number of deaths have resulted from water gas for this reason, and in some states the laws forbid its use for lighting purposes.
When water gas is used it must be enriched with some other substances before it will yield much light. You have already learned that neither hydrogen nor carbon monoxide burns with a bright flame, and you will see that water gas must have something added to it to fit it for lighting purposes. The substance usually added is the vapor of some light, volatile oil, like gasoline. This vapor is composed of compounds of carbon and hydrogen, and when it is mixed with the water gas it forms a gas that yields a very satisfactory light; and that may be produced more cheaply than common coal gas.
There remains one more form of illuminating gas which has been the subject of much discussion in recent years, namely, acetylene. This is a compound of carbon and hydrogen, in which there is twelve times as much carbon as hydrogen. It has not been discovered recently, for it was known early in the nineteenth century, but its possible use for lighting purposes was not considered then.
Attention was directed to it a few years ago by the discovery of a substance called calcium carbide. This is a compound of carbon and the metal calcium, formed by heating to a very high temperature a mixture of coal and lime. It has the peculiar property of decomposing, when treated with water. The calcium present combines with the oxygen and half the hydrogen of the water, to form common slacked lime or calcium hydrate, while the carbon and the remainder of the hydrogen combine to form acetylene gas.
The gas formed in this way needs no purifications before burning; it can be produced in small generators, and the production can be checked at any time. When burned in the proper form of burner it yields the brightest of all gas flames. For these reasons it is adapted for use in small villages and for lighting single houses. It is also frequently used in magic lanterns, where a strong and steady light is necessary. But the cost of producing acetylene in large quantities is greater than that of coal gas, and it seems extremely unlikely that it will ever be much used for lighting large cities and towns.
How the Light Gets Into the Electric Light Bulb.
The incandescent lamp was invented in 1879 and the patents were granted to Thomas A. Edison. There were, however, a number of electrical men who were working on the idea at this time who deserve a great deal of credit for developing the lamp.
The incandescent lamp, which is used chiefly for house lighting, consists of a glass bulb from which the air has been exhausted by pumps and chemical processes--in which there is a thin filament of tungsten metal wound on what is called an arbor (as shown in Fig. 4). This filament opposes high resistance to the passage of the current of electricity, and, consequently, is heated to incandescence when a current passes through it. The removal of the air from the bulb prevents the tungsten metal from burning up, as it would do if oxygen were present.
The filaments of the first lamps were made of vegetable fibre. The next development was the cellulose process, which is still used in carbon and metallized lamps, although a number of processes are used now which improve the filament considerably.
The discovery that tungsten metal could be used in incandescent lamps was made in 1906. The first tungsten lamp manufactured in America was made in 1907.
[Illustration: THE DEVELOPMENT OF INCANDESCENT LAMPS
Edison’s first lamp with a filament of bamboo fibre.]
[Illustration: The carbon lamp--the oldest form of incandescent lamp.]
[Illustration: Standard Mazda lamp--the highest development of the incandescent lamp.]
[Illustration: The Tantalum lamp developed just before the Mazda lamp.]
[Illustration: Improved Mazda lamp for lighting large areas--the most efficient lamp ever made.]
The filaments of the first tungsten lamps were composed of two or three short pieces of wire. In 1910, however, a lamp with a continuous tungsten filament was invented which increased the strength of the lamp wonderfully.
Mazda is a trade name given to all metal filament lamps made by the prominent American lamp manufacturers.
The reason that the Mazda lamp is so much more efficient than the carbon filament lamp is because the tungsten filament can be burned at a much higher temperature than the present carbon filament, without seriously blackening the bulb.
How Does an Arc Light Burn?
In the arc light a current of electricity is made to leap across from the tip of one rod of carbon to the tip of another that is held a short distance from the first. In passing across the current does not follow a straight path, but makes a curve, or arc, whence comes the name “arc light.”
In this form of light the carbons are not enclosed in a space from which air is excluded, consequently there is some destruction of the carbon. The light is due to the fact that the air between the tips of the carbon rods opposes a high degree of resistance to the current, so that the rods become intensely hot at their tips. The high degree of heat causes a slow burning of the carbon at the tips, and the small
## particles that burn are heated white hot before they are consumed, thus
producing light.
In order to keep the light from an arc light uniform in strength, it is necessary to keep the tips of the carbon rods always the same distance apart. This is practically impossible, and, as a result, the arc light does not produce light that is well adapted for reading or for other purposes that require constant use of the eyes. The light produced by the arc light is very powerful, however, and for that reason it is much used for street lighting.
What Are X-Rays?
It was discovered by Professor Conrad Roentgen in 1895, that if a current of electricity be passed through a certain form of glass bulb, from which most of the air has been exhausted, a disturbance is produced in the ether that bears some resemblance to light waves. For want of a better name to give to a disturbance which was not well understood, Roentgen called his discovery the X-Ray, but it is now frequently called in his honor the Roentgen ray. The nature of this disturbance is not yet known, but as it does not affect the eye it is not light. These rays are produced with a glass vacuum tube and a battery from which a current of electricity is sent through the tube. The wires of the battery are connected with two electrodes, one of which consists of a concave disk of aluminum, and the latter of a flat disk of platinum. The X-rays are discharged in straight lines as shown in the figure. The most striking properties of the X-ray is its power to penetrate many substances that are impermeable to light. All vegetable substances, and the flesh of animals, are penetrated by it very readily. Glass, metals, bones, and mineral substances generally are opaque to it. Consequently, when a limb, or even the body of an animal, is exposed to X-rays they pass through the fleshy parts, but are stopped by the bones. Certain substances have the property of glowing, or becoming fluorescent, when exposed to the X-ray, and when screens of paper are coated with these substances they form a convenient means of detecting the presence of X-rays. By holding the hand between a tube that is giving off X-rays and a screen of this kind, the bones of the hand will be outlined in shadow on the screen, and the rest of the surface will glow with a greenish light. If a bullet or other piece of metal has become imbedded in the body, it may easily be located, if it is not in a bone, and the extent of an injury to a bone or a joint may be plainly shown. For this reason the X-ray is now widely used by surgeons.
How Man Learned to Fight Fire.
When you see the modern fire engine racing through the streets, gongs ringing, with the firemen hanging on and the police clearing the track, you should remember that it has taken man a long time to learn as much as he has about fighting fire.
No sooner did man learn to make fire than he found it necessary to learn how to put it out.
The first fire apparatus of record is found in Rome. The Gauls burned the city in 390 B. C., each citizen was ordered to keep in his house a “machine for extinguishing fire.” This consisted of a syringe.
The first record of an actual machine for putting out fire is by Hero of Alexandria. This contrivance, a “siphon used in conflagrations,” was used in Egypt about a hundred and fifty years before Christ.
The first record of what we would call a fire department is also found in Rome. A disastrous fire, occurring in the reign of Augustus called his attention to the benefit of a regular fire brigade would bring. So he organized a fire department. It consisted of seven companies of a thousand men each.
The first real fire engines were used in 1633 at a big fire on London Bridge. The first fire hose was invented by the two Van der Heydes in 1672. One of the earliest engines used consisted of a tank drawn by two horses, which threw a stream an inch in diameter to a height of eighty feet. An improved engine was invented in 1721 by Newsham, of London, and the first engine used in the United States was made by Newsham. The first steam fire engine was invented by John Braithwaite, of London, in 1829.
Fire alarms came into use in medieval times. It was the custom, in many of the towns to have a watchman stationed on a high building whose duty it was to look for fires. As soon as he saw one, he gave warning by blowing a horn, firing a gun, or ringing a bell.
The first London fire department consisted of ten men of each ward.
The first municipal American fire department was created in Boston in 1678. The fire engine was a hand pump bought in England.
The first leather fire hose was made in America in 1808 in Philadelphia. Rubber hose was first made in England at about 1820.
How Did Man Learn to Cook His Food?
The primitive man lived on raw food--raw flesh, roots, fruits and nuts. There must have been a time when he lived thus because there was a time when he had no fires and no knowledge of how to make a fire. There are no records, however, to show when man learned that cooked food was best.
It must have come about almost simultaneously with his knowledge of fire, for the art of cooking goes back to the first knowledge of fire. We do not know either how man learned to make a fire. The earliest nations of which we have any record seem to have been acquainted with fire and certain methods for producing it. Not only one but all early nations seem to have been possessed of this knowledge. Occasionally travellers have reported that people have been found who were unacquainted with either fire or cooking, but investigation has always proven these reports unauthentic. Cookery has always been found in practice where people knew about fire.
It is strange how man has lost track of the beginning of his knowledge of fire and cookery, because fire represents the beginning of man’s culture and cookery goes hand in hand with it.
There are many legendary accounts of how man learned the value of cooked food, all of which are based upon the accidental burning or roasting of animals or birds. Perhaps, therefore, Charles Lamb’s “Roast Pig” story, which we read with much laughter in our school readers, was quite accurate from a historical standpoint. According to the story a man’s house burned and he cried more over the fate of his pet pig than about the loss of his house. He kept his pig in the house you will remember and as soon as the fire died away he rushed into the debris to look for his pet pig, hoping still to rescue him. He found him in a corner and made haste to pick him up and carry him into the open air. But the poor pig had been roasted to a turn and was still hot. The man’s fingers went right into the well done roast pig and were burned. With a cry he withdrew his fingers and put them into his mouth to blow on them and thus he secured his first taste of roast pig, which he found so much to his taste that he repeated the operation of licking his fingers.
While this is but a story, it is quite likely historically correct as to this discovery of the value of cooked food to some of the early nations. No doubt Fire and Cookery were developed together.
When man had learned to make fire, he found that it often got beyond his control. Here and there he would set the woods on fire quite without intention perhaps, but with damaging results. He would watch the conflagration and, when it was passed, he would find the baked bodies of deer or other animals which had been overcome by the fire and learned that baked meats were good to the taste and more easily digestible than raw meats.
Why Does a Sponge Hold Water?
A sponge will hold water because it has, on account of the plan on which it is grown the power of capillary attraction. The sponge is made up of little hair like tubes. If you take a glass tube, open at both ends and immerse one end in a vessel of water, you will find that the water will rise in the tube to a level higher than the surface of the water in the vessel. The smaller the hole through the glass tube, the higher the water will rise. This is caused by the cohesion of the water against the inside surface of the hole in the tube and causes a pull upward. The water is pulled up into the tube because the surface of the tube has a greater cohesive attraction for the water than for the air which was in it and the air is forced out partly. Some liquids, such as mercury will not rise in the same way, but is depressed in a glass tube, since it cannot adhere to glass. Mercury however will run or rise in a tin tube, just as water in a glass tube, because it adheres to the tin.
Now a sponge is merely a lot of capillary tubes which have the same power of pulling up the water as the glass tube. The tubes in a sponge are so fine that the water will rise to the entire length of the tubes. In addition, this adhesive quality of water to the inside of the tubes in the sponge is so strong, that the sponge can be taken entirely out of the water and the water will remain in it.
Why Is the Right Hand Stronger Than the Left?
The right hand is stronger than the left only in case you are right-handed. If you have the habit of being left-handed, your left hand becomes stronger. If you are truly ambidextrous, your strength will be the same in both hands.
We get our strength by moving the various parts of the body, i. e., by using them. When a little baby stretches his arms and legs and kicks, he is only exercising naturally, making the blood circulate.
You can prove that the fact that your right hand is stronger than your left because of the greater use or exercise you give it, by tying your right arm close to your side and keeping it in that condition without using it for several weeks. When you remove the bands which held it tight, you will find your arm has lost its strength and that now your left hand is stronger. If, however, you are left-handed and tie that hand down for the same length of time, your right hand would be the stronger. This shows that the strength we have in our arms and legs, and other parts of the body, is developed by using them and giving them rational exercise. Of course, it is possible to over-use a part of the body, but you will notice that nature always gives us a warning by making us tired before we come to the point where further use of that
## particular part of the body would cause injury.
Why Do My Muscles Get Sore When I Play Ball In the Spring?
They do this because you have probably not been exercising the
## particular muscles which you employ in throwing a ball enough in the