Chapter III: Part 3

The next process is that of “annealing.” This consists in heating the forging to a red heat and then allowing it to cool very slowly, and is usually done by hauling the fires in the furnace after the correct temperature has been attained and permitting both to cool off together. This process is to relieve the strains set up in the metal during forging, and further, it alters the molecular condition of the steel, making a finer and more homogeneous forging.

Photo by Bethlehem Steel Co.

This photograph shows a gun tube ready to be lowered into oil bath for “oil tempering.”]

After annealing, the forging is ready to go to the machine shop to be rough bored and turned. The forging is set in a lathe, the breech end being held by jaws on the face-plate and the muzzle end by a “pot-centre,” a large iron ring having several radial arms screwed through it. The lathe can now be turned and the forging centered by screwing in or out on the jaws of the face-plate or the radial arms of the “pot-centre.” When centered, several surfaces are turned on the forging for “steady rests” and then all is in readiness for the turning and boring.

In both operations of “turning” and “boring,” the work revolves while the cutting tools are fed along. Turning is very simple and usually several tools are cutting at the same time, but boring is a more delicate operation, because the workman cannot see what he is doing. And in boring, either a “hog bit” or a “packed bit” is used; a “hog bit” is a half cylinder of cast iron fitted with one cutting tool and used for rough cuts, while a “packed bit” is a full cylinder of wood with metal framing and carrying two tools 180° apart and used for finishing cuts.

The forging, having been rough machined, is now ready to receive its heat treatment in order to give to the steel its required physical characteristics. Every piece of steel used in gun manufacture must conform to certain specifications as regard both its physical and chemical characteristics. The chemical analysis was made at the time the ingot was cast; now for the treatment of the forging, prior to the physical test as to its tensile strength, elastic limit, elongation and contraction.

The “tensile strength” of a metal is the unit-stress required to break that metal into parts. If a round bar ten inches in cross-section area will fracture under a strain of 120 tons, its tensile strength is 120 ÷ 10 or 12 tons per square inch. Tensile strength is usually expressed in pounds per square inch.

The “elastic limit” of a metal is the unit-stress required to first produce a permanent deformation of the metal. If a bar of metal be subjected to an increasing strain, up to a certain point that metal will be perfectly elastic, resuming its normal shape when the strain is removed; at the first permanent set or deformation, however, the elastic limit of that metal has been reached. Elastic limit is expressed in pounds per square inch.

By “elongation” is meant the increase in length in a bar when its tensile strength is reached. If a bar 10 inches long after rupture measures 11.8 inches, its elongation is 18%.

By “contraction” is meant the decrease in cross-section area in a bar when its tensile strength is reached. If a bar 1 square inch in area after rupture is only .75 of a square inch in area, its contraction is 25%.

These definitions being understood, a brief description of the heat treatment can be taken up, because it is after this treatment that standard bars are taken from the forgings to undergo the physical tests. The first step consists in “tempering” or hardening the metal. The piece to be tempered is placed in an upright position in a high furnace and uniformly heated to the required temperature. It is then lifted from the furnace through an opening in the top and carried by a crane to an oil tank of suitable depth and plunged into the oil. This rapid cooling or “tempering in oil” is facilitated by having the oil tank surrounded by a water bath, so arranged that a supply of cold water is constantly in circulation to carry the heat from the mass as quickly as possible. This operation produces exceeding toughness, increases the tensile strength and raises the elastic limit of the metal.

Now the forging is again annealed, so as to relieve any strains set up by tempering and to soften up the metal to the degree required by the specifications. It also increases materially the elongation and contraction. Great care must be exercised in the heat treatment, as the acceptance or rejection of the forging depends upon whether or not the test bars pass the required specifications.

The forging is now submitted for test and the test bars taken. In the manufacture of a big gun, four test bars are taken from the breech end and four from the muzzle end of each forging and these bars sent to the physical laboratory. Quite an elaborate testing machine is provided, and if the bars pass the required tests the forging is accepted and is sent to the machine shop for finish-boring and turning.

~SEARCHING FOR POSSIBLE DEFECTS~

Frequently during finish-boring the work is examined to see that the bit is running true, and great care must be exercised to prevent its running out of alignment.

After finish-boring every forging is “bore-searched,” that is, the bore is carefully examined for any cracks, flaws, streaks or discoloration. A special instrument called a “bore-searcher” is used and consists of a long wooden handle which has a mirror inclined at 45° at one end, together with a light to illuminate the bore, and so shielded as to obscure the light from the observer. (See sketch.)

The bore is also inspected by the foreman after each boring, but the final “bore-searching” is done by an inspector.

Now to measure accurately the inside diameters of long cylinders, such as are used in gun work, a special measuring device called a “star-gauge” is used. Its name is derived from the fact that it has three measuring points set at 120° apart and two measurements are taken, one and the other , making a star . Every forging is “star-gauged” after being finish-bored and also the liner of the _gun_ after each assemblage operation.

~PUTTING THE PARTS OF A “BUILT-UP” GUN TOGETHER~

In preparation for the assembling of the different parts, the tube is the forging to be finished. It is bored and turned to exact dimensions and carefully “bore-searched” and “star-gauged.” With the data at hand a sketch is made showing the external diameters of the liner under the tube, due allowance being made for the shrinkage when assembling.

The liner is next bored to within .35 of an inch of the finished diameter, and turned to the dimensions required by the sketch above. This extra metal in the bore is left until the gun is completely assembled and is removed in the finish-boring. The liner is then carefully “bore-searched” and “star-gauged” and liner and tube are ready for assembling.

The liner is now taken to the shrinking pit and carefully aligned in an upright position with the breech end down.

The shrinking pit is merely a well of square section with room enough to permit workmen to move freely about the gun when it is in position, and equipped with a movable table at its bottom upon which the gun rests. In the meantime the tube, with breech end down, is being heated in a hot-air furnace. This furnace is a vertical cylinder built of fire-brick and asbestos and so constructed that air which has been passed in pipes over petroleum burners can enter at the bottom, pass around and through the tube and out through the top to be reheated. This service permits a uniform heat to be transmitted to the tube and when the desired temperature has been attained the tube is lifted from the furnace by a crane, carried to the shrinking pit and carefully lowered over the liner. Great care must be exercised in this operation to prevent the tube from sticking while being lowered into place. Should it happen, the tube should be hoisted off at once, allowed to cool, any roughing of the liner be smoothed off, the tube reheated and a second trial made. When the tube is properly in place a cold spray may be turned upon any particular section where it is desired the tube should first grip the liner. The tube is then left to cool by itself, but cold water is constantly circulating through the liner.

When the gun is sufficiently cool for handling purposes, it is hoisted out of the shrinking pit and taken to the shop for careful measurement, the liner being “star-gauged” to note the compression due to the shrinking on of the tube.

The same procedure is followed in the case of the jackets and hoops, until the entire gun is assembled. The gun is considered completely “built-up” when the last hoop has been shrunk on and is now ready to be finished.

The gun is now finish-bored, as .35 of an inch of metal was left in the liner in the first boring. “Packed bits” are used and the greatest care is exercised to keep the bit properly centered and running true. After this step the gun is finish-turned and the powder chamber is bored.

Following this operation the gun is “bore-searched” for any defects that may have shown up in the finish-boring and chambering, and then carefully “star-gauged.” The gun is then ready to be “rifled.”

Photo by Bethlehem Steel Co.

This photograph shows a gun in the Rifling Machine in the process of being rifled.]

The “rifling” of a gun consists in cutting spiral grooves in the surface of the bore from the powder chamber to the muzzle end, and is done from the muzzle end. Rifling is a very difficult operation, and great care must be exercised that the cutting is uniform. The grooves are separated by raised portions called “lands,” and after “rifling,” these grooves and “lands” are carefully smoothed up to remove the rough edges or burrs caused by the cutting tools of the “rifling” machine.

The necessary holes are now drilled for fitting the breech mechanism and the breech block fitted. This operation usually takes some little time, as quite a bit of hand work is necessary to insure a perfect fit. The “yoke,” really another “hoop,” is now put on at the breech end and the gun is complete.

The centre of gravity of gun and breech mechanism is now determined by balancing on knife edges and the whole then weighed. The breech mechanism is also weighed and the two weights marked on the rear faces of the gun and breech mechanism.

The gun is now fitted in its “slide,” that part of the mount which carries the trunnions and through which the gun recoils when it is fired, and after it is adjusted, all is in readiness for the “proof-firing” or testing of the gun.

What Is Motion?

There are practically but two things we see when we use our eyes. One of them is matter, which is a term we apply to the things we see, speaking of them as objects only, and the other is motion which we observe some of the matter to possess. Some of the things we see confuse us, if we bear in mind that everything is either matter or motion. For instance, we see light and know it is not matter and are confused until we understand that light is a movement of the ether which surrounds us and is in and outside of everything. In the same way we feel heat and may think it is matter thrown off by the fire, when it is only another kind of motion of this same ether. When we understand these things we see that motion is a very important and real part of the world.

When a motion is started it will keep on going forever unless some other force which is able to overcome the motion stops it. When a ball is thrown in the air it would go on forever were it not for the law of gravitation which pulls it to the earth and the friction of the air on the ball as it goes through the air. When you stop a thrown ball you sometimes realize that motion is a real thing because it stings your hands. We do wonderful things with motion. Many things when you add motion to them acquire qualities which they did not possess before. For instance, an ordinary icicle thrown against a wooden door will break, but if you put it into a gun and give it sufficient motion, it will go right through the door. There is a story of how a man killed another by using an icicle as a bullet. The icicle entered the man’s body and killed him. Then, of course, the ice melted and no one could tell how the man received his wound, for no trace of anything like a bullet could be found. A piece of paper has no cutting qualities, but if you arrange a circular or square piece of paper with a rod or stick through the center and revolve it fast enough, you can cut many things while it is whirling. The motion gives it the cutting qualities. You can take a piece of strong rope and, by tying the ends together, making a circle of it, you can make it roll down the street like a steel hoop if you catch it just the right way and set it spinning fast enough before starting it on its way. A steam engine has no power to pull the train of cars until the wheels are set in motion. So we see that motion is a very important thing in the world.

Motion is the cause of movements of all kinds, the power which takes things from one place to another.

Is Perpetual Motion Possible?

Perpetual motion will never be possible unless some one discovers a way to overcome the law of gravitation and also the certainty that materials will eventually wear out. Many men have tried to make a machine that would keep on moving forever without the application of any power, the consumption of fuel within itself, the fall of weights or the unwinding of a spring; such a machine would be absolutely impossible, although many people have been fooled into investing money in machines that appeared to have this power within themselves.

How Can an Explosion Break Windows That Are at a Distance?

An explosion is a sudden expansion of a substance like gunpowder or some elastic fluid or other substance that has the power to explode under certain conditions with force, and usually a loud report. Some explosions are comparatively mild and accompanied by a very mild noise, while others are very powerful and accompanied by a very loud noise. When an explosion occurs, the air and everything surrounding the thing that explodes is very much disturbed. The air surrounding the thing that explodes is thrown back in air waves which are powerful in the exact proportion in which the explosion is powerful. These air waves can be so suddenly thrown back against the objects in the vicinity that not only the windows in the buildings are broken, but often the entire building blown away. The explosion acts in all directions at once with equal force. A great hole may be torn in the earth beneath the explosion. If there is anything over the explosion, that is blown away unless its power of resistance is sufficient to withstand the power of the explosion. Then, also, the air surrounding on all sides is forced back against everything in its path.

Very often this air which is suddenly forced back by the power of the explosion is thrown against houses at a distance. These houses may be so strongly built as to be able to withstand the effect of the explosion, but still certain parts of them, such as the windows and the bricks of the chimney, may not be able to withstand this sudden pressure of air against them and they are forced in. The wind from such an explosion acts on the outside of the windows just the same as though you stood on the outside with your hands against the windows and pushed them in. Anything that is thrown against a window with more force than the window glass can resist will break the window, and even slight explosions may be so powerful as to throw the air back and away from them with such force as to break windows at a great distance--even a mile or more away.

Why Do Some Things Bend and Others Break?

When an outside force is applied to some objects, some of them will bend and others break. It is due to the fact that in some things the particles have the faculty of sticking together or hanging on to each other, and it is very difficult to break them away from each other. In such instances, as in the case of a wire, the article will bend when we apply the power to it and it will not break, because the particles which make up the wire have the faculty of hanging on to each other. A piece of glass, however, can be broken right in two by the application of no more force than was used to bend the wire, because the particles which make up the glass haven’t the faculty to hang on to each other. If you continue to bend a wire back and forth, however, at the same point, it will finally break apart, because you eventually overcome the ability of the particles in the wire to hang on to each other.

It all depends upon the hanging-on ability. Sometimes in undergoing different processes an article which will ordinarily only bend will become very brittle or breakable. A steel wire may bend but if you make a steel wire very hard it becomes brittle. On the other hand, glass is very brittle ordinarily, but if you make it very hot, you can bend it into any shape you wish, and thus the glass-worker makes different shapes to various dishes; lamp chimneys, bottles, etc., by heating glass and then bending it. When it becomes cool again, it also becomes brittle or breakable as before.

Why Does a Ball Bounce?

When you throw a ball against the floor in order to make it bounce the ball gets out of shape as soon as it comes in contact with the floor. As much of it as strikes the floor becomes perfectly flat, and because the ball has a quality known as elasticity, which means the ability to return to its proper shape, it returns to its shape immediately and in doing so forces itself back into the air and that is the bounce.

Of course, the first thing we think of when we consider something that bounces is a ball, and in most cases a rubber ball. We are more familiar with the bouncing qualities of a rubber ball. Other balls, like standard baseballs, are not so elastic as a rubber ball filled with air, but a solid-rubber ball is more elastic and some golf balls are much more elastic than a solid-rubber ball. The principle is the same, when you drive a golf ball, excepting that when you bounce a ball on the floor the floor does the flattening and when you drive a golf ball, the golf club does the flattening. A baseball flies away from the bat for the same reason. When you meet a fast-pitched ball squarely on the nose with a good swing, it goes farther and faster than when you hit a slow-pitched ball with an equal swing, because in the case of the fast-pitched ball you flatten the ball out more, and it has so much more to do to recover its proper shape that it bounces away from the bat at much greater speed and goes much further unless caught than a slow-pitched ball under the same circumstances.

What Makes a Ball Stop Bouncing?

A bouncing ball, when you first throw it against the wall bounces back at you about as fast as you throw it, but if you do not catch it on the rebound, it goes to the floor again, because the law of gravitation which is the pulling power of the earth, pulls it down again. When it strikes the floor it is again flattened to a certain extent and bounces up again, but does not come back so high. It goes on striking the floor and bouncing back into the air again each time a shorter distance, until the force of gravity has actually overcome its tendency to bounce back.

When you bounce a ball on the floor and it bounces up again, the motion of the ball through the air is affected by the friction that the contact with the air produces and this friction of the air overcomes part of the bouncing ability in the ball also.

What Makes a Cold Glass Crack if We Put Hot Water Into It?

Hot water will not always cause a cold glass to crack, but is very apt to, especially a thick glass. The very thin glasses will not crack. The test tubes used by chemists are made of very thin glass, and will not crack when hot liquids are poured into them.

When a glass cracks after you have poured a hot liquid into it, it does so because, as soon as the hot liquid is put in, the particles of glass which form the inside of the glass become heated and expand. They begin to do this before the particles which form the outside of the glass become heated, and in their efforts to expand the inside particles of glass literally break away from the particles which form the outside, causing the crack. The same thing happens if you put cold water into a hot glass, excepting in this instance the inside particles of the glass contract before the particles which form the outside of the glass have had time to become cool and do likewise.

What Causes the Gurgle When I Pour Water from a Bottle?

The air trying to get in causes the gurgle. Air has one strong characteristic which stands out above everything else. It wants to go some place else all the time. When it learns of a place where there is no air it wants to go there above all things, and goes at it with a rush.

Now, when you turn a bottle full of water upside down, the water comes out if the cork is out, of course, and as soon as the water starts out the air strives to get in, and every time you hear a gurgle you know the air is getting in. Every gurgle is a battle between the water and the air. Sometimes the air comes and pushes the water back enough to let it slide into the bottle; sometimes the water pushes the air back, and thus they fight back and forth. The water always gets out and the air always gets in. In doing so they make the gurgle.

Where Does the Part of a Stocking Go That Was Where the Hole Comes?

Perhaps this is a foolish question, but many boys and girls have been puzzled for an answer to it. When you put your stockings on they have no holes in the feet, and at night, when you take them off, there are often quite large holes in them. The answer is the same as in the case of the lead in the lead-pencil. The lead in the pencil wears away. You can see it wear away because that is what makes the marks.

When a hole is coming into your stocking, the stocking on your foot is being rubbed between your foot and something else (probably some part of your shoe) and this constant rubbing will wear through the yarns with which the stocking is knitted. Of course, the yarns in the stocking are stretched somewhat when it is on your foot and the rubbing finally cuts through the threads and releases the tension of the threads of yarn, so that not always is as much stocking lost as the size of the hole. But, if you were to look carefully at your foot and inside your shoe, when you first take the stocking off and see the hole, you would find little particles of yarn all about.

Why Do Coats Have Buttons On the Sleeves?

The practice of putting buttons on coat sleeves, which serve no useful purpose at all and do not add to the beauty of the coat, is a relic of very old days.

There was a time when people did not use handkerchiefs, and it was common practice for men to wipe their noses on their sleeves. They had coats also in those days, but they did not have buttons on the sleeves. One of the old kings finally developed the idea of dressing his soldiers in fancy uniforms and, as he sat in his palace and reviewed his troops, he noticed many of them using the sleeves of their coats as handkerchiefs. He immediately issued a decree that all sleeves should have a row of buttons sewed on them, but at a point directly opposite to where they are now on the sleeves. This was done to remind the soldiers that the sleeves of their beautiful uniforms were not to be used as handkerchiefs, and those who attempted to draw their sleeves in front of the nose were quickly reminded of the decree by the buttons which scratched them. And so the buttons really had a quite useful purpose at one time, and so also all sleeves had buttons sewed on to them at this place. Later on, however, when the unsightly practice had been cured and people had learned to use handkerchiefs, the buttons remained as a decoration, but their former purpose was lost sight of. Then some tailor or leader of fashion had the buttons set on the under side of the sleeves for a change, and it became the fashion to have them there, and the tailors have been sewing them there ever since.

Why Has a Long Coat Buttons on the Back?

The buttons on the back of a long coat, i. e., one with skirts, had a more sensible reason originally. At one time the skirts of such coats were made very long, and when the wearer moved quickly the tails of the coat flapped about the legs and interfered with progress. So an ingenious gentleman had buttons sewed on to the back and buttonholes made in the corner of his coat-tails. Then when he was in a hurry he simply buttoned up his skirts and went his way comfortably.

Showing in outline the apparatus necessary to complete the simplest kind of a telephone call--to a number in the same exchange]

The Story in the Telephone

~WHAT HAPPENS WHEN WE TELEPHONE~

Mrs. Smith, at “Subscriber’s Station No. 1,” desires to telephone to Mrs. Jones at “Subscriber’s Station No. 2.” When she lifts her receiver, the movement causes a tiny white light to appear instantly on the switchboard at the Central Office. Directly beneath this light is another and larger lamp, which glows in a way to attract the operator’s attention immediately.

The operator inserts a “plug” in a little hole on the switchboard called a “jack,” directly above the tiny light which appeared when Mrs. Smith lifted the receiver. This connects her to Mrs. Smith’s line. Then she pushes a listening key on the board, connecting her telephone set to the line. “Number, please?” she calls.

Mrs. Smith gives the number; the operator repeats it to be sure there is no mistake, places another “plug” in a “jack” corresponding to the number of Mrs. Jones’ telephone and makes the connection.

Each subscriber’s telephone has a particular signal on the switchboard to which it is connected by a pair of wires. Mrs. Smith’s wires run from her instrument to the nearest “cable terminal,” a gathering point for the wires of various telephones in her neighborhood. Here they form part of a group of wires going to the Central Office. These groups, called cables, are made up of from 50 to 600 pairs of wires, according to the telephone needs of the district the “terminal” serves.

When the wires reach the Central Office they pass through the “cable vault” to the “main distributing frame,” which is the Central Office terminal of the cable.

When the wires come to this frame they are in numbered order in the cable. Subscribers living next door to Mrs. Smith may have entirely different call numbers and yet use consecutive wires. It is the task of the main frame to redistribute these wires, so that they will be arranged according to their call numbers and to make it possible to connect Mrs. Smith’s line with the line of any other subscriber with the least possible delay. This frame has two parts: the “vertical side” and the “horizontal side.” Before the wires are redistributed they are taken to pairs of springs equipped with devices for protecting the lines against outside currents.

After leaving the main frame they are taken to the “intermediate distributing frame,” the central connecting point for various branches of the lines going to the switchboard, signaling and other apparatus. From the “horizontal side” of this frame, wires go to the switchboard, where they terminate in little holes known as “multiple jacks.” They also connect with the line and position message registers, where the calls from each Line and the calls handled at each operator’s position at the switchboard are recorded. The “multiple jacks” are additional terminals placed at necessary intervals throughout the switchboard, where they can be used by operators to make connections with any other line on the board.

From the “vertical side” of the intermediate frame Mrs. Smith’s wires reach the “line and cut-off relay,” an electrically controlled switch which turns on the light signal that appears on the switchboard when she lifts the receiver from the hook. This “line relay” also extinguishes the light when the operator makes the connection, or when Mrs. Smith returns the receiver to the hook.

The swift moving electric current that was set in motion when Mrs. Smith began the call, instantaneously passes through all these devices for safeguarding and protecting the subscriber’s telephone service. The light announcing Mrs. Smith’s desire to make a call is called the “line lamp,” and is flashing on the switchboard. Directly beneath it is the “pilot lamp,” which glows whenever any “line lamp” lights. With the “line lamp” is a “jack” or terminal, where connection can be made with Mrs. Smith’s line. This is the “answering jack.”

When the operator sees the flashing signal of Mrs. Smith’s “line lamp,” she inserts one end of a pair of “connecting cords,” which are on the board before her, in the “answering jack” for Mrs. Smith’s line. These “connecting cords” are flexible conductors that put the wires of subscribers in electrical connection. Then she pushes forward the “operator’s key” directly in front of her and is connected with Mrs. Smith’s line.

The operator ascertains the number wanted and places the other “connecting cord” in the “jack” corresponding to Mrs. Jones’ line. If she finds she cannot herself connect with Mrs. Jones’ “jack,” because it is on another part of the board out of her reach, she makes a connection with another operator who can reach Mrs. Jones’ line. The second operator then makes the connection with Mrs. Jones’ “multiple jack” and places her line in connection with Mrs. Smith’s line at the first operator’s position. At the same time the first operator pushes the operator’s key back, thus ringing Mrs. Jones’ bell.

“Supervisory lamps” on the board before her, connected with the “connecting cords,” tell the operator when Mrs. Jones answers the summons. They flash when the connection is made and one goes out just as soon as Mrs. Jones takes the receiver from the hook to answer. If one of these lamps flashes and dies out alternately it tells the operator that either Mrs. Smith or Mrs. Jones is trying to attract her attention and she connects herself and ascertains the party’s wishes. When both subscribers “hang up,” both lights flash to indicate the end of the conversation. The operator then disconnects the cords from the subscribers’ “jacks” and presses the “message register” button recording the call against Mrs. Smith.

The subscriber, after looking up in the directory the desired number, takes the telephone off the hook, which causes a tiny electric light to glow in front of the operator assigned to answer his calls. (In some exchanges equipped with a magneto system, a drop is released by the turning of a crank.)]

A MULTIPLE SWITCHBOARD]

On the top floor of this building, in 1875, Prof. Bell carried on his experiments and first succeeded in transmitting speech by electricity]

How the Telephone Came to Be.

It is hard to realize that there was once a time, not so very many years ago, when the telephone was regarded as a scientific toy and hardly anyone could be found willing to invest any money in the development of the telephone business.

The story of Professor Alexander Graham Bell’s wonderful invention is full of romantic interest and the early days of its exploitation were replete with dramatic incidents.

~THE MEN WHO MADE THE TELEPHONE~

Young Bell had come to America in 1870 in search of health, the family settling at Brantford, Canada. He numbered among his forebears many distinguished professional men. For three generations the Bells had taught the laws of speech in the universities of Edinburgh, Dublin and London. He himself was an accomplished elocutionist and an expert in vocal physiology.

During the year spent in Canada in regaining his health, Bell taught his father’s method of visible speech to a tribe of Mohawk Indians and began to think about the “harmonic telegraph.”

In 1871 young Alexander Bell accepted an offer from the Boston Board of Education to teach the “visible speech” method in a school for deaf mutes in that city.

For two years he devoted himself to the work with great success. He was appointed a professor in the Boston University and opened a school of “Vocal Physiology” which was at once successful.

He might have continued his career as a teacher had it not been that his active brain still clung to the “harmonic telegraph” idea and his inventive genius demanded an outlet.

So we find him in 1874 working out his idea of the “harmonic telegraph,” the perfection of which meant a fortune to the young inventor. That he never realized his goal was due to the fact that while experimenting, he made a discovery which led to a far greater invention and one that was fraught with more benefit to mankind than the “harmonic telegraph” could ever have been.

It was while working with his faithful man Friday, Thomas A. Watson, in the dingy little workrooms on Court Street, Boston, that Bell got the inspiration which made him turn from the “harmonic telegraph” to devote himself to the invention which was destined to make his name famous--the speaking telephone.

~THE FIRST SOUND OVER A WIRE~

Mr. Watson has dramatically described the incident as follows:

“On the afternoon of June 2, 1875, we were hard at work on the same old job, testing some modification of the instruments. Things were badly out of tune that afternoon in that hot garret, not only the instruments, but, I fancy, my enthusiasm and my temper, though Bell was as energetic as ever. I had charge of the transmitters, as usual, setting them squealing one after the other, while Bell was retuning the receiver springs one by one, pressing them against his ear as I have described. One of the transmitter springs I was attending to stopped vibrating and I plucked it to start it again. It didn’t start and I kept on plucking it, when suddenly I heard a shout from Bell in the next room, and then out he came with a rush, demanding, ‘What did you do then? Don’t change anything. Let me see!’ I showed him. It was very simple. The make-and-break points of the transmitter spring I was trying to start had become welded together, so that when I snapped the spring the circuit had remained unbroken while that strip of magnetized steel by its vibration over the pole of its magnet, was generating that marvelous conception of Bell’s--a current of electricity that varied in intensity precisely as the air was varying in density within hearing distance of that spring. That undulatory current had passed through the connecting wire to the distant receiver which, fortunately, was a mechanism that could transform that current back into an extremely faint echo of the sound of the vibrating spring that had generated it, but what was still more fortunate, the right man had that mechanism at his ear during that fleeting moment, and instantly recognized the transcendent importance of that faint sound thus electrically transmitted. The shout I heard and his excited rush into my room were the result of that recognition. The speaking telephone was born at that moment. Bell knew perfectly well that the mechanism that could transmit all the complex vibrations of one sound could do the same for any sound, even that of speech. That experiment showed him that the complex apparatus he had thought would be needed to accomplish that long-dreamed result was not at all necessary, for here was an extremely simple mechanism operating in a perfectly obvious way, that could do it perfectly. All the experimenting that followed that discovery, up to the time the telephone was put into practical use, was largely a matter of working out the details. We spent a few hours verifying the discovery, repeating it with all the differently tuned springs we had, and before we parted that night Bell gave me directions for making the first electric speaking telephone. I was to mount a small drumhead of gold-beater’s skin over one of the receivers, join the center of the drumhead to the free end of the receiving spring and arrange a mouthpiece over the drumhead to talk into. His idea was to force the steel spring to follow the vocal vibrations and generate a current of electricity that would vary in intensity as the air varies in density during the utterance of speech sounds. I followed these directions and had the instrument ready for its trial the very next day. I rushed it, for Bell’s excitement and enthusiasm over the discovery had aroused mine again, which had been sadly dampened during those last few weeks by the meagre results of the harmonic experiments. I made every part of that first telephone myself, but I didn’t realize while I was working on it what a tremendously important piece of work I was doing.

ALEXANDER GRAHAM BELL’S FIRST TELEPHONE]

The First Telephone Line.

“The two rooms in the attic were too near together for the test, as our voices would be heard through the air, so I ran a wire especially for the trial from one of the rooms in the attic down two flights to the third floor where Williams’ main shop was, ending it near my work bench at the back of the building. That was the first telephone line. You can well imagine that both our hearts were beating above the normal rate while we were getting ready for the trial of the new instrument that evening. I got more satisfaction from the experiment than Mr. Bell did, for shout my best I could not make him hear me, but I could hear his voice and almost catch the words. I rushed upstairs and told him what I had heard. It was enough to show him that he was on the right track, and before he left that night he gave me directions for several improvements in the telephones I was to have ready for the next trial.”

Then followed many heart-breaking months of experimenting and it was not until the following March that the telephone was able to transmit a complete, intelligible sentence.

On February 14, 1876, Professor Bell filed at Washington his application for patents covering the telephone which he described as “an improvement in telegraphy” and on March 3, of the same year, the patent was allowed.

That was the year of the Centennial Exposition at Philadelphia and Professor Bell had a working model of the telephone on exhibition. Tucked away in an obscure corner it had attracted but little attention, until on June 25th an incident occurred which had a tremendous effect in giving to the new invention just the sort of publicity it needed.

Professor Bell himself describes the incident in the following interesting manner:

“Mr. Hubbard and Mr. Saunders, who were financially interested in the telephone, wanted this instrument to be exhibited at the Centennial Exhibition. In those days--and I must say even up to the present time I am afraid to say it is true--I was not very much alive to commercial matters, not being a business man myself. I had a school for vocal physiology in Boston. I was right in the midst of examinations.

“I went down to Philadelphia, growling all the time at this interruption to my professional work, and I appeared in Philadelphia on Sunday, the 25th. I was an unknown man and looked around upon the celebrities who were judges there, and trotted around after the judges at the exhibition while they examined this exhibit and that exhibit. My exhibit came last. Before they got to that it was announced that the judges were too tired to make any further examinations that day and that the exhibit could be examined another day. That meant that the telephone would not be seen, for I was not going to come back another day. I was going right back to Boston.

~HOW AN EMPEROR SAVED THE TELEPHONE~

“And that was the way the matter stood--when suddenly there was one man among the judges who happened to remember me by sight. That was no less a person than His Majesty Dom Pedro, the Emperor of Brazil. I had shown him what we had been doing in teaching speech to the deaf in Boston, had taken him around to the City School for the Deaf and shown him the means of teaching speech, and when he saw me there he remembered me and came over and shook hands and said: ‘Mr. Bell, how are the deaf mutes of Boston?’ I said they were very well and told him that the next exhibit on the program was my exhibit. ‘Come along,’ he said, and he took my arm and walked off with me--and, of course, where an Emperor led the way the other judges followed. And the telephone exhibit was saved.

An Emperor Wonders.

“Well, I cannot tell very much about that exhibit, although it was the pivotal point on which the whole telephone turned in those days. If I had not had that exhibition there it is very doubtful what the condition of the telephone would be today. But the Emperor of Brazil was the first one to bring that situation about at that time. I went off to my transmitting instrument in another part of the building, and a little iron box receiver was placed at the ear of the Emperor. I told him to hold it to his ear, and then I heard afterward what happened. I was not present at that end of the line. I went to the other end and was reciting, ‘To be or not to be, that is the question,’ and so on, keeping up a continuous talk.”

“I heard afterward from my friend, Mr. William Hubbard, that the Emperor held it up in a very indifferent way to his ear, and then suddenly started and said, ‘My God! it speaks!’ And he put it down; and then Sir William Thomson took it up and one after another in the crowd took it up and listened. I was in another part of the building shouting away to the membrane telephone that was the transmitter. Suddenly I heard a noise of people stamping along very heavily, approaching, and there was Dom Pedro, rushing along at a very un-Emperor-like gait, followed by Sir William Thomson and a number of others, to see what I was doing at the other end. They were very much interested. But I had to go back to Boston and couldn’t wait any longer. I went that very night.”

“Now, it so happened there, that, although the judges had heard speech emitted by the steel disc armature of this receiving instrument, they were not quite convinced that it was electrically produced. Some one had whispered a suspicion that it was simply the case of the thread telegraph, the lovers’ telegraph, as it was known in those days, and that the sound had been mechanically transmitted along the line from one instrument to the other. Of course, I did not know about it at that time; but when the judges asked permission to remove the apparatus from that location I said, ‘Certainly, do anything you like with it.’ But I could not remain to look after it; they had to look after it themselves.”

“My friend, Mr. William Hubbard, who had kindly come up from Boston to help me on this celebrated Sunday, June 25, said he would do his best to help them out, although he was not an electrician. He knew nothing whatever about the apparatus, beyond being in my laboratory occasionally, knowing me well. But he undertook to remove this apparatus and set up the line under the direction of the judges themselves. So they had an opportunity finally of satisfying themselves that speech had really been electrically reproduced.”

“Sir William Thomson’s announcement was made to the world in England, before the British Association, and the world believed--and from that time dates the popular interest in the telephone.”

In October, 1876, the first outdoor demonstration, in which conversation was carried on over a private telegraph wire, borrowed for the occasion, took place between Boston and Cambridge, a distance of two miles.

In April, 1877, the first telephone line was installed between Boston and Somerville.

A month later an enterprising Boston man put up a crude switchboard in his office and connected up five banks, using the system for telephoning in the day-time and as a protection against burglars at night. This was the beginning of the exchange system, all previous telephoning having been between two parties on the same circuit.

~NINE MILLION TELEPHONES IN U. S.~

Soon after exchanges sprang up in several cities, and by August of that year there were 778 Bell telephones in use. From this modest beginning the telephone has grown until on January 1, 1914, there were 13,500,000 telephones in the world, nearly 9,000,000, or over 64 per cent being in the United States.

When the wires come to this frame they are in numbered order in the cable. The main frame redistributes these wires so that they are arranged according to their call numbers, making it possible to connect any wire with any other wire anywhere that telephone service is installed.]

Breaking Up the Asphalt Pavement. First Step in Laying an Underground Cable.]

The use of the telephone instrument is common, but it affords no idea of the magnitude of the mechanical equipment by which it is made effective.

~UNSEEN FORCES BEHIND YOUR TELEPHONE~

To give you some conception of the great number of persons and the enormous quantity of materials required to maintain an always-efficient service, various comparisons are here presented.

The poles are set all over this country, and strung with wires and cables; the conduits are buried under the great cities; the telephones are installed in separate homes and offices; the switchboards housed, connected and supplemented with other machinery, and the whole system kept in running order so that each subscriber may talk at any time, anywhere.

Where Does Sound Come From?

Somebody or something causes every sound we hear. Sounds are the result of disturbances in the air. Sound is produced by waves in the air. The buzz of the bumble-bee is caused by the quick movement of his wings in the air. The wings themselves do not make the sound, but their motion causes waves or vibrations in the air which produce the sound of buzzing. Every motion made by anybody or anything produces waves in the air just like the waves you see in the water--a big movement makes a big wave and a tiny movement a tiny wave. When you clap your hands you make a disturbance in the air which causes a sound--the harder you clap the louder the sound. You can hear this sound and anybody else near can hear it. If there were no air about us, however, we would hear no sound, even if we could live in such a condition of things, for it is the air waves produced striking against the drum of our ears that enable us to discern sounds. When we talk we make air waves also and thus produce sound. If you were deaf, and talked, you could not hear any sound, because even when there are air waves they must still strike against a sounding board in order to be recognized as sound--and the drum of our ear is our sounding board for hearing sounds.

When the air waves produced are regular we call the sound musical, and when they are irregular we call it noise. Some people can make musical sounds when they sing, while others cannot.

If you take a piece of thin wire and stretch it tightly, fastening it at both ends, and then pull it with your finger and let go, you will hear a musical sound, because the vibrations produced will be regular and will continue for some time. If you shorten the distance on the wire where it is fastened at both ends and pull it as before, the sound produced will be in a higher key. If you take a guitar and snap the big G string you will produce the bass note of G. If the other G string (the smaller one) is in tune (if you watch the smaller one closely while you strike the larger one) you will notice the smaller one vibrate also. Sound waves of the same tone, although in different octaves, produce the same sounds, although in different keys.

This is the principle on which the piano is made to produce music. Inside the piano are wires of different lengths and the keys of the piano are arranged to operate certain little hammers, each of which strikes a certain wire. Every time you strike a piano key you cause one of the little hammers to hit its wire--the wire then makes vibrations which cause air waves. The air waves strike against the sounding board which is located behind the wires, and being thrown back into the air, strike against the drum of our ears, and we can hear the note.

Why Can We Make Sounds With Our Throats?

The sounds we make when we talk are produced in exactly the same way with the exception of the little hammers. In our throats are two cords which we call our vocal cords. When we talk we cause these cords to vibrate and thus we make the sounds of our voices. The most wonderful part of this voice of ours is that with only two vocal cords or wires, we can produce practically all the notes that can be made with a piano, which has a wire or cord for every note, excepting that we cannot make so many at one time. The human throat is so wonderfully constructed that we can lengthen or shorten our vocal cords at will and produce, with two strings, in our throats as many notes as it takes the piano many more strings to produce.

Why Does the Sound Stop When We Touch a Gong that Has Been Sounded?

When we touch the gong we stop the sound waves which the gong gives off when it is struck. These sound waves continue after the gong has been struck in continuous vibrations until something stops them. When you touch the vibrating gong, you stop its vibrating. If you only touch your finger to the vibrating gong you can feel the vibrations which cause a little tickling sensation. Naturally when you stop these vibrations you stop the air waves which the vibrations cause, and thus also the sound of these air waves striking your ear are stopped and the sound ceases.

How Can Sound Come Through a Thick Wall?