The Boy's Book of New Inventions

by Harry E. Maule

AUTOGENOUS WELDING AND CUTTING

"Now," said the scientist, after he and his young friend had finished some experiments, and were ready to talk about autogenous welding, "imagine a little white flame no bigger than a pencil point at the end of a brass pipe about the size, and not entirely unlike in appearance the old-fashioned taper holder with which you used to light the gas, and you have before you in the rough, a picture of one of the oxy-acetylene torches that will in a few minutes weld two pieces of almost any metal, or in a few seconds cut a solid plate of the hardest steel of several inches thickness almost as fast and easy as a carpenter could saw a board, and yet without taking the temper out of the metal."

Picking up what seemed to be a little brass rod bent at the end, the man turned a valve, applied a match, and as the gas burned up with a beautiful little flame of dazzling whiteness, he continued:

"This tiny flame, so easily controlled, is hotter than any produced by man except that generated by the electrical furnace, for it reaches a temperature of about 6,300 degrees Fahrenheit. Previous to the invention of these wonderful torches the oxy-hydrogen was the hottest gas flame, but it only reached a temperature of 4,000 degrees Fahrenheit."

"How do you use it?" asked the boy.

"Well, for instance, Uncle Sam is enabled to weld and cut steel plate in building his battleships, steelworkers to carry on their gigantic tasks, and wreckers to clear away tangled masses of steel beams far more quickly and easily than with the older methods.

"If you had visited one of the navy yards, a shipyard or any place where big work in iron and steel was being carried on as short a time as three years ago, you would have seen a man sitting for hours sawing away on the end of a steel beam, for instance, trying to cut it down to the required length. He would dull many saws, use a great deal of energy, and an appalling amount of the most valuable thing in the world—time. Again, you would have seen them welding pieces of iron and steel by the old blacksmith method, or riveting other pieces that could not be joined by heating them and pressing them together.

"To-day you would see fewer of these processes because autogenous welding and cutting by the powerful little oxy-acetylene torches is revolutionizing certain methods of working with metals. Instead of squatting at the end of the beam and sawing away like an old-fashioned carpenter, the modern iron worker takes up his little torch, turns a valve in the handle and concentrates the flame on the steel beam that he wishes cut. Almost instantly a shower of sparks on the under side of the beam shows him that the flame has burned its way through. Then he slowly moves the flame along the line where he desires to cut and the trick is done."

Illustrating with his own little laboratory torch, the scientist continued his explanation, saying that cutting is only one of the many uses to which this modern invention in steel working is put. Not quite so spectacular but every bit as useful is the autogenous welding by means of these magic wands. Welding metals has ever been more or less unsatisfactory. The old process of heating the two ends and then beating them together is cumbersome and practically impossible in many cases. Consequently inventors have sought other welding processes with wider application and greater facility ever since the first metal workers of earliest times forged crude chains and weapons. With this modern device two pieces of steel or other metal are brought to within a small fraction of an inch of each other and by the use of the oxy-acetylene torch and a thin strip or rod of metal are melted and fused together.

Although the acetylene flame gives off a far greater proportion of light than heat, it is a very powerful gas and Le Chetalier, a French inventor, was sure that he could put it to other uses than furnishing lights for automobiles, etc. To this end he tried mixing acetylene gas with oxygen, for there can be no fire or combustion without oxygen. He very properly figured that by introducing pure oxygen into the acetylene, the burning, or combustion, would be greater, and the heat of the flame greatly intensified. His experiments were ultimately successful, and it was then only a short step to the time when three different oxy-acetylene torches were in use. In France there were developed low pressure, medium pressure, and high pressure torches; but the last named has not been found commercially practicable in the United States, where the "medium pressure" torch is sometimes called the high pressure. As we are dealing entirely with the American use of the invention we also will call the two kinds of torches used here the low pressure and the high pressure.

The general principle of the torch is, as we see, the mixture of oxygen with acetylene in order to obtain a hotter flame, but right here we come to the difference between the low-pressure and the high-pressure tools. Both are made of brass pipes, terminating in the burning tip and connected at the rear of the handle with rubber tubes which run to the separate tanks holding the acetylene gas and the oxygen, but the method by which these gases are combined in the torch constitutes the principle differences in the two systems, with the consequent greater or less efficiency claimed by the manufacturers. Without going into the technical details, which are a matter of controversy between scientists as well as the various commercial concerns interested in the torches, it will be sufficient to say that in the low-pressure torch the acetylene gas is only used under a pressure of a few ounces, with the oxygen under a much heavier pressure, while in the high-pressure torches, the acetylene and oxygen both are under an appreciable pressure of several pounds.

Thus in the low-pressure torch invented by Fouché, the oxygen is forced out of the nozzle by the pressure and the outrush sucks out the acetylene in the proper quantities. The two gases mix in a chamber at the end of the torch just above the tip and flow out into the air in this mixed form. The proportions of the gases in the low-pressure tool are about 1.7 of oxygen to 1.0 of acetylene.

The high-pressure torch, which has largely taken the place of the low-pressure one in France, and which we also see most frequently in this country, has a different method of mixing the gases, due to the fact that they both are under pressure. According to many authorities the tip where the gases are mixed is by far the most important factor in the success or failure of the tool. In the high-pressure torch the oxygen enters the tip from a hole in the centre, while the acetylene enters it from two holes, one on each side. They meet under high pressure at the upper end of the tip, and have the length of the hollow tip in which to mix, before they strike the air. The long, narrow hole in the tip is called the mixing chamber. Those who are interested in the high-pressure torch declare that it is the fact that the gases are positively mixed in proper proportion in the detachable tip, that so greatly adds to the efficiency of the tool. They declare that by allowing the acetylene to enter the tip laterally, at right angles with the oxygen, the blast of the oxygen is broken as it mixes with the acetylene, and the tendency of an oxygen flame to oxidize any metal with which it comes in contact by reason of an excess of oxygen in the flame is largely done away with. This, with the small diameter of the mixing chamber and the friction with the walls, gives a perfect mixture, according to the claims of the high-pressure torch enthusiasts. Moreover, the small hole which is the mixing chamber, effectually prevents serious accidents by flash-backs of the highly explosive acetylene, and also provides a much easier method of control. Each outfit has several different sizes of tips for various kinds of work.

The pressure under which the two gases are used is the other big difference between the high-pressure and the low-pressure torches, as said before. In the the high-pressure tool the oxygen is compressed about the same as in the low-pressure torch, while the acetylene is under several pounds pressure, just in accordance with the size of the tip used. In the low-pressure torch the pressure on the acetylene is only about ten ounces to the square inch, or only enough to keep it flowing. On account of this difference in the pressure making the big difference in the mixture of the gases, scientists have chosen to call the low-pressure torches injector mixture types, from the fact that the acetylene is sucked into the tip by an injector system, while the high-pressure torches are called positive mixture types, because the gases are mixed directly by pressure. In the latest high-pressure tool the mixture of gases is 1.14 parts of oxygen to 1 part of acetylene, while the low-pressure torch takes a proportion of 1.7 parts of oxygen to 1 part of acetylene.

The torches also vary in size from the little 8-ounce "jeweller's" torch, that the scientist used, to nineteen to twenty inches long and a weight of two and a quarter pounds. The average size, however, is twelve inches long with a weight of one pound. The welding torch is made up of two brass tubes, one for the acetylene and the other for the oxygen, connected at the two ends. At the nozzle end there is a sharp turn in the piping so that the tip is very nearly at right angles to the main pipes. At the handle end, are the connections for the rubber tubes that lead to the gas tanks, and the little valves by which the operator can control the flow of gas. The pipes carrying the gases to the tip are the same size the whole length, but at one end are enclosed in a larger tube, which serves as a handle.

Now that we have seen the general construction of the oxy-acetylene torches, we will assume that the tanks, which look like large soda-water reservoirs, are filled with pure oxygen and acetylene gas, and transported to some convenient point in a railroad repair shop where great forges are spurting flames, and one can hardly hear the talk of a man beside him for the roar of the hammers and the compressed air riveters. Assume that some large expensive steel part of a locomotive has been broken and must be repaired quickly so that the engine can go out on the road to help haul an accumulation of freight.

In the old days an engine would have to be taken apart, a new part turned out at the steel mill, shipped to the shops, and the locomotive put together again. Nowadays it is only necessary to take enough of the machinery apart for the workmen to get at the broken parts. After cutting off the edges to be welded so that they make a small V, and supporting them within the fraction of an inch apart in the exact position and shape that they are to be repaired, the workman selects a rod of steel or iron, to use in somewhat the same way the tinker uses a strip of solder when he wants to repair a break in a kettle with solder and soldering iron.

The selection of this filling rod, or wire, is all-important, for the skilful and successful iron worker uses a piece of metal that will fuse well with the parts to be repaired, at about the same temperature at which they themselves will fuse. Mild steel or Norway iron which is 90 per cent. pure is frequently used, but there are no hard and fast rules because every master mechanic has his own ideas about such things, and would not take the word of any manufacturing company.

Then the operator turns on his torch, lights it with a match, takes it in one hand, and the rod of welding steel in the other. Holding the end of the steel rod at the thin crack or bevelled edges between the pieces to be welded the operator directs the small flame on the point, holding the tip of the torch about a quarter to a half inch from the metal. It only takes a few seconds for the terrific heat of the flame to melt the strip of steel and the edges of the parts to be welded so that they all are fused together in one perfect mass.

Strange as it may seem, the brass tip of the torch does not melt in this heat because the pressure behind the gases forces them out with such velocity that the flame is far enough removed from the tip to do it no injury, just so long as the operator does not put the tip square against the metal and drive the flame back against it. This not only would melt the tip but probably would cause a flash-back in the torch.

As the end of the strip melts into the crack the operator moves up the steel, and moves his torch along the crack until the whole operation is complete. At the end the weld is very rough but when it is machined down it may be so perfect that it is difficult to tell where it was made, and the strength is equal to that of any other part of the piece.

In other words, the weld becomes homogenous with the parts repaired. From this fact autogenous welding takes its name. Autogenous is defined as "self produced," or independent of outside materials.

Thus, we see that the autogenous process is a system of putting on new material, without either heating, compression, or adding flux (molten material) to the broken parts. In the foregoing paragraphs we have taken up the welding of steel parts, but the process can be as well applied to steel pipe, steel plate, iron, cast-iron, aluminum, copper, and other materials with only slight variations in the manner of using the torch.

The cutting process is even more spectacular because while the welding proceeds quietly, the cutting is accompanied by just enough fireworks to show us the progress of the tiny flame through the hardest and thickest of metals.

The cutting torch is the same as the welding torch with the exception of an additional pipe from which flows a jet of pure oxygen to give the flame the necessary cutting property. The greater the supply of oxygen the greater the combustion, and the more penetrating the flame. The acetylene gas flame heats up the steel—"fills the office of a preheater," said the scientist—while the oxygen jet follows close behind and makes a thin cut through the hot metal.

The extra pipe is the same size as the others and extends down to the end of the torch at an angle where its tip is clamped alongside the main tip. The rear end of the third tube is connected with a rubber hose like the others, which extends to the oxygen tank. The flow of oxygen is under higher, and individual working pressure, controlled by a valve. In a new style torch the extra hose is done away with and the separation of the oxygen is done in the torch.

When the modern steel carpenter wants to cut a hole, or saw off a strip from a piece of steel, no matter whether it be a steel beam, steel plate, or almost any other form of iron (except cast-iron), he attaches the cutting pipe, lights his torch and sets to work. Holding the tool about half an inch from the surface he directs the little blue flame, which is no more than three quarters of an inch long, and a quarter of an inch thick, against the spot where he desires to start cutting. He holds it there a few seconds, then there is a shower of sparks on the under side of the steel plate, indicating that the flame has eaten its way all the way through. The operator next moves the torch along the line where he wants to cut. The speed with which he can move is governed by the thickness of the steel to be cut. Half-inch ship steel, for instance, could be cut at a rate of more than a foot a minute. The heat of the flame melts a little of the steel, which drops down in molten particles, but the edge that is cut is sharp and clean, and its temper is as perfect as if the cutting were done with one of the laborious old-fashioned steel saws.

AN OXY-ACETYLENE GAS TORCH WELD

Note the little torch in the man's left hand, the filling metal in his right, and the inserted picture of the apparatus.

TINY 200-HORSEPOWER TURBINE

This engine could almost be covered by a derby hat. A part of the casing is removed to show the smooth disks.

THE TESLA TURBINE PUMP

Driven by a 1/12-horsepower motor. The little pump here shown is delivering 40 gallons of water per minute against a 9-foot head.

This cutting process is of especial value to navy yards, shipyards, and wreckers, where there is a great deal of steel to be cut. Uncle Sam uses it at most of his navy yards, for in building his battleships there are thousands and thousands of holes to be cut in steel plates, plates to be shaped, and beams to be cut off to required lengths.

When the scientist and his young friend visited the Brooklyn Navy Yard to see this process in operation the naval constructors had made considerable headway on the framework of the great Dreadnaught New York, in course of building there. The huge steel ribs of the ship towered upward amid the scaffolding nearly as high as a five-story building. In laying this steel framework, and shaping the plates that will make the hull, bulkheads, and decks, there will be millions of holes to be cut, and virtually miles and miles of plates to be shaped. Instead of sawing these the workmen were cutting them with the oxy-acetylene torches.

Half a dozen men were at work, all cutting as fast as possible, and the great steel plates, and beams were coming and going as quickly as ever boards were passed along by a carpenter. The lines that were to be cut were all marked out in advance so the men never put out their torches. The only cessation in the work was when one of them stopped for a minute or so, to wipe his eyes, for in spite of the dark goggles worn by all operators of the oxy-acetylene process the intense flame is very hard on the eyes.

One reason why the cutting process is so popular in shipyards is because in making steel ships, holes are cut in the plates, ribs, and beams, wherever possible without lessening the strength, to lighten the frame.

Probably the most picturesque use of the cutting device is by wreckers of steel structures. Nowadays whenever there is a bad fire the building is left a tangled mass of steel pipes and girders that can only be cleared away with the greatest risk of life, and the greatest difficulty. The process always was a long, tedious one until the oxy-acetylene cutting came into use.

Thousands of New York boys saw the device in use during the winter of 1911-1912 when they visited the ruins of the Equitable Life Assurance Society fire. The sight is unmistakable. Far up in the ruins you see a man bending over a great twisted steel beam that it might take weeks to pull out of the débris. Soon there is a shower of sparks, and the part that is sticking out is cut off and ready to be sent to the street and hauled away. The device has been used in the ruins of a large number of disastrous fires, lately, particularly where men have been entombed in the collapse of ceilings, and haste means everything in getting out their bodies. Also, it was very successfully used in cutting up the old battleship Maine before the hull was removed from Havana harbour.

CHAPTER VIII
THE TESLA TURBINE

DR. NIKOLA TESLA TELLS OF HIS NEW STEAM TURBINE ENGINE A MODEL OF WHICH, THE SIZE OF A DERBY HAT, DEVELOPS MORE THAN 110 HORSEPOWER

"HOW would you like to have an engine for your motor boat that you could almost cover with a man's derby hat and yet which would give 110 horsepower?" asked the scientist of his young friend one day when they had been talking about boats and engines.

"I never heard of any real engine as small as that," said the boy. "I used to play with toy engines, but they wouldn't give anywhere near one horsepower, much less 110."

"Well, I think I can show you a little engine that, for mechanical simplicity and power is about the most wonderful thing you ever have seen, if you would like to make another visit to Dr. Nikola Tesla, who told us all about his invention for the wireless transmission of power the other day. Doctor Tesla invented this little engine and he is going to do great things with it."

Of course the boy jumped at the opportunity, for what real boy would miss a chance to find out all about a new and powerful engine?

"Is it a gasoline engine?" he asked.

"No, it is a steam turbine, but if you know anything at all about turbines you will see that it is entirely different from any you ever have seen, for Doctor Tesla has used a principle as old as the hills and one which has been known to men for centuries, but which never before has been applied in mechanics."

After a little more talk the scientist promised to arrange with Tesla to take the young man over to the great Waterside power-house, New York, where the inventor is testing out his latest invention. We will follow them there and see what this wonderful little turbine looks like.

Picking his way amid the powerful machinery and the maze of switchboards, the scientist finally stopped in front of a little device that seemed like a toy amid the gigantic machines of the power-house.

"This is the small turbine," says Tesla. "It will do pretty well for its size."

The little engine looked like a small steel drum about ten inches in diameter and a couple of inches wide, with a shaft running through the centre. Various kinds of gauges were attached at different points. Outside of the gauges and the base upon which it was mounted, the engine almost could have been covered by a derby hat. The whole thing, gauges and all, practically could have been covered by an ordinary hat box.

Yet when Tesla gave the word, and his assistant turned on the steam, the small dynamo to which the turbine shaft was geared, instantly began to run at terrific speed. Apparently the machine began to run at full speed instantly instead of gradually working up to it. There was no sound except the whir of well-fitted machinery. "Under tests," said Tesla, "this little turbine has developed 110 horsepower."

Just think of it, a little engine that you could lift with one hand, giving 110 horsepower!

"But we can do better than that," added the inventor, "for with a steam pressure of 125 pounds at the inlet, running 9,000 revolutions per minute, the engine will develop 200 brake-horsepower."

Nearby was another machine a little larger than the first, which seemed to be two identical Tesla turbines with the central shafts connected by a strong spring. Gauges of different kinds, to show how the engine stood the tests, were attached at various places. When Tesla gave the word to open the throttle on the twin machines the spring connecting the shafts, without a second's pause, began to revolve, so that it looked like a solid bar of polished steel. Outside of a low, steady hum and a slight vibration in the floor, that steadied down after the engine had been running a little while, there was no indication that enough horsepower to run machinery a hundred times the weight and size of the turbine was being generated.

"You see, for testing purposes," said Doctor Tesla, "I have these two turbines connected by this torsion spring. The steam is acting in opposite directions in the two machines. In one, the heat energy is converted into mechanical power. In the other, mechanical power is turned back into heat. One is working against the other, and by means of this gauge we can tell how much the spring is twisted and consequently how much power we are developing. Every degree marked off on this scale indicates twenty-two horsepower." The beam of light on the gauge stood at the division marked "10."

"Two hundred and twenty horsepower," said Doctor Tesla. "We can do better than that." He opened the steam valves a trifle more, giving more power to the motive end of the combination and more resistance to the "brake" end. The scale indicated 330 horsepower. "These casings are not constructed for much higher steam pressure, or I could show you something more wonderful than that. These engines could readily develop 1,000 horsepower.

"These little turbines represent what mechanical engineers have been dreaming of since steam power was invented—the perfect rotary engine," continued Doctor Tesla, as he led the way back to his office. "My turbine will give at least twenty-five times as much power to the pound of weight as the lightest weight engines made to date. You know that the lightest and most powerful gasoline engines used on aeroplanes nowadays generally develop only one horsepower to two and one half pounds of weight. With that much weight my turbine will develop twenty-five horsepower.

"That is not all, for the turbine is probably the cheapest engine to build ever invented. Its mechanical simplicity is such that any good mechanic could build it, and any good mechanic could repair such parts as get out of order. When I can show you the inside of one of the turbines, in a few moments, however, you will see that there is nothing to get out of order such as most turbines have, and that it is not subjected to the heavy strains and jerks that all reciprocating engines and other turbines must stand. Also you will see that my turbine will run forward or backward, just as we desire, will run with steam, water, gas, or air, and can be used as a pump or an air compressor, just as well as an engine."

"But most of your research has been in electricity," Tesla was reminded, for no one can forget that Tesla's inventions largely have made possible most of the world's greatest electrical power developments.

"Yes," he answered, "but I was a mechanical engineer before I was an electrical engineer, and besides, this principle was worked out in the course of my search for the ideal motor for airships, to be used in conjunction with my invention for the wireless transmission of electrical power. For twenty years I worked on the problem, but I have not given up. When my plan is perfected the present-day aeroplanes and dirigible balloons will disappear, and the dangerous sport of aviation, as we know it now with its hundreds of accidents, and its picturesque birdmen, will give way to safe, seaworthy airships, without wings or gas bags, but supported and driven by mechanical means.

"As I told you before when we were talking of the wireless transmission of power, the mechanism will be a development of the principle on which my turbine is constructed. It will be so tremendously powerful that it will make a veritable rope of air above the great machine to hold it at any altitude the navigators may choose, and also a rope of air in front or in the rear to send it forward or backward at almost any speed desired. When that day comes, airship travel will be as safe and prosaic as travel by railroad train to-day, and not very much different, except that there will be no dirt, and it will be much faster. One will be able to dine in New York, retire in an aero Pullman berth in a closed and perfectly furnished car, and arise to breakfast in London."

Tesla's plans for the airship are far in the future, but his turbine is a thing of the present, and it has been declared by some of the most eminent authorities in the world in mechanical engineering to be the greatest invention of a century. The reason for this is not altogether on account of the wonderful feats of Tesla's model turbines, but because in them he has shown the world an entirely unused mechanical principle which can be applied in a thousand useful ways.

James Watt discovered and put to work the expansive power of steam, by which the piston of an engine is pushed back and forth in the cylinder of an engine, but it has remained for Nikola Tesla to prove that it is not necessary for the steam to have something to push upon—that the most powerful engine yet shown to the world works through a far simpler mechanism than any yet used for turning a gas or a fluid into the driving force of machinery.

"How did you come to invent your turbine while you were busy with your wonderful electrical inventions?" Tesla was asked.

"You see," he answered, "while I was trying to solve the problem of aerial navigation by electrical means, the gasoline motor was perfected; and aviation as we know it to-day became a fact. I consider the aeroplane as it has been developed little more than a passing phase of air navigation. Aeroplaning makes delightful sport, no doubt, but as it is now it can never be practical in commerce. Consequently I abandoned for the time being my attempts to find the ideal airship motor in electricity, and for several years studied hard on the problem as one of mechanics. Finally I hit upon the central idea of the new turbine I have just been showing you."

"What is this principle?"

"The idea of my turbine is based simply on two properties known to science for hundreds of years, but never in all the world's history used in this way before. These properties are adhesion and viscosity. Any boy can test them. For instance, put a little water on a sheet of metal. Most of it will roll off, but a few drops will remain until they evaporate. The metal does not absorb the water so the only thing that makes the water remain on the metal is adhesion—in other words, it adheres, or sticks to the metal.

"Then, too, you will notice that the drop of water will assume a certain shape and that it will remain in that form until you make it change by some outside force—by disturbing it by touch or holding it so that the attraction of gravitation will make it change.

"The simple little experiment reveals the viscosity of water, or, in other words, reveals the property of the molecules which go to make up the water, of sticking to each other. It is these properties of adhesion and viscosity that cause the 'skin friction' that impedes a ship in its progress through the water, or an aeroplane in going through the air. All fluids have these qualities—and you must keep in mind that air is a fluid, all gases are fluid, steam is fluid. Every known means of transmitting or developing mechanical power is through a fluid medium.

"It is a surprising fact that gases and vapours are possessed of this property of viscosity to a greater degree than are liquids such as water. Owing to these properties, if a solid body is moved through a fluid, more or less of the fluid is dragged along, or if a solid is put in a fluid that is moving it is carried along with the current. Also you are familiar with the great rush of air that follows a swiftly moving train. That simply means that the train tends to carry the air along with it, as the air tries to adhere to the surface of the cars, and the particles of air try to stick together. You would be surprised if you could have a picture of the great train of moving air that follows you about merely as you walk through this room.

"Now, in all the history of mechanical engineering, these properties have not been turned to the full use of man, although, as I said before, they have been known to exist for centuries. When I hit upon the idea that a rotary engine would run through their application, I began a series of very successful experiments."

Tesla went on to explain that all turbines, and in fact all engines, are based on the idea that the steam must have something to push against. We shall see a little later how these engines were developed, but it will suffice for the moment to listen to Doctor Tesla's explanation.

"All of the successful turbines up to the time of my invention," he says, "give the steam something to push upon. For instance"—taking a pencil and a piece of paper—"we will consider this circle, the disk, or rotor of an ordinary turbine. You understand it is the wheel to which the shaft is attached, and which turns the shaft, transmitting power to the machinery. Now it is a large wheel and along the outer edge is a row of little blades, or vanes, or buckets. The steam is turned against these blades, or buckets, in jets from pipes set around the wheel at close intervals, and the force of the steam on the blades turns the wheel at very high speed and gives us the power of what we call a 'prime mover'—that is, power which we can convert into electricity, or which we can use to drive all kinds of machinery. Now see what a big wheel it is and what a very small part of the wheel is used in giving us power—only the outer edge where the steam can push against the blades.

"In my new turbine the steam pushes against the whole wheel all at once, utilizing all the space wasted in other turbines. There are no blades or vanes or sockets or anything for the steam to push against, for I have proved that they hinder the efficiency of the turbine rather than increase it."

Comparing his turbine to other engines Tesla says, "In reciprocating engines of the older type the power-giving portion—the cylinder, piston, etc.—is no more than a fraction of 1 per cent. of the total weight of material used in construction. The present form of turbine, with an efficiency of about 62 per cent., was a great advance, but even in this form of machine scarcely more than 1 per cent. or 2 per cent. is used in actually generating power at a given moment. The only part of the great wheel that is used in actually making power is the outside edge where the steam pushes on the buckets.

"The new turbine offers a striking contrast using as it does practically the entire material of the power-giving portion of the engine. The result is an economy that gives an efficiency of 80 per cent. to 90 per cent. With sufficient boiler capacity on a vessel such as the Mauretania, it would be perfectly easy to develop, instead of some 70,000 horsepower, 4,000,000 horsepower in the same space—and this is a conservative estimate.

"You see this is obtained by the new application of this principle in physics which never has been used before, by which we can economize on space and weight so that the most of the engine is given over to power producing parts in which there is little waste material."

Tesla then went on to explain the details of his new turbine. Leading the way to a small model in his office he unscrewed a few bolts and lifted off the top half of the round steel drum or casing. Inside were a number of perfectly smooth, circular disks mounted upon one central shaft—the shaft that extends through the machine, and corresponds to the crankshaft of an ordinary engine. The disks all were securely fastened to the rod so that they could not revolve without making it also turn in its carefully adjusted bearings. The disks, which were only about one sixteenth of an inch in thickness, and which he said were constructed of the finest quality of steel, were placed close together at regular intervals, so that a space of only about an eighth of an inch intervened between them. They were solid with the exception of a hole close to the centre. The set of disks is called the rotor or runner.

When the casing is clamped down tight, the steam is sent through an inlet or nozzle at the side, so that it enters at the periphery or outside edge of the set of disks, at a tangent to the circle of the rotor. Of course the steam is shot into the turbine under high pressure so that all its force is turned into speed, or what the scientists call velocity-energy. The steel casing of the rotor naturally gives the steam the circular course of the disks, and as it travels around the disks the vapour adheres to them, and the particles of steam adhere to each other. By the law that Tesla has invoked, the steam drags the disks around with it. As the speed of the disks increases the path of the steam lengthens, and at an average speed the steam actually travels a distance of twelve to fifteen feet. Starting at the outside edge of the disks it travels around and around in constantly narrowing circles as the steam pressure decreases until it finally reaches the holes in the disks at their centre, and there passes out. These holes, then, we see act as the exhaust for the used-up steam, for by the time the steam, which was shot into the turbine by the nozzle under high pressure, reaches the exhaust, it registers no more than about two pounds gauge pressure.

DIAGRAM OF THE TESLA TURBINE

A—Steam Inlet. B—Disks. C—Path of the Steam. D,D´D´´—Exhaust. E—Reverse Inlet. F—Shaft.

For reasons which will be explained later, ordinary turbines cannot be reversed, but Tesla's invention can run backward just as easily as forward. The reverse action is accomplished simply by placing another nozzle inlet on the other side of the rotor so that the steam can be turned off from the right side of the engine, for instance, and turned into the left side, immediately reversing its direction, with the change in the direction of the steam. The action is instantaneous, too, for as we saw in the experiments Tesla showed us, the turbine began to run at practically top speed as soon as the steam was turned on.

The disks in the little 110-horsepower engine which we saw, were only a little larger than a derby hat were only nine and three quarter inches in diameter, while in his larger turbines he simply increases the diameter of the disks.

Tesla further explained that the 110-horsepower turbine represented a single stage engine, or one composed simply of one rotor. Where greater power is required he explained that it would be easy to compound a number of rotors to a double, or triple or even what he calls a multi, or many stage, turbine. In engineering the single stage is called one complete power unit, and a large engine could be made up of as many units as needed, or practicable.

"Then do you mean to say," Tesla was asked, "that the only thing that makes the engine revolve at this tremendous speed is the passage of steam through the spaces between those smooth disks?"

"Yes, that is all," he answered, "but as I explained before, the steam travels all the way from the outer edge to the centre of the disks, working on them all the time; whereas in the ordinary turbines the steam only works on the outside edge, and all the rest of the wheel is useless. By the time it leaves the exhaust of my engine practically all the energy of the steam has been put into the machine."

This is only one of the many advantages that Tesla points out in his invention, for the turbine is the exemplification of a principle, and hence more than a mechanical achievement. "With a 1,000-horsepower engine weighing only 100 pounds, imagine the possibility in automobiles, locomotives, and steamships," he says.

Explaining the large engines that he is testing, one against the other, at the power plant, the inventor said:

"Inside of the casings of the two larger turbines the disks are eighteen inches in diameter and one thirty-second of an inch thick. There are twenty-three of them, spaced a little distance apart, the whole making up a total thickness of three and one half inches. The steam, entering at the periphery, follows a spiral path toward the centre, where openings are provided through which it exhausts. As the disks rotate and the speed increases the path of the steam lengthens until it completes a number of turns before reaching the outlet—and it is working all the time.

"Moreover, every engineer knows that, when a fluid is used as a vehicle of energy, the highest possible economy can be obtained only when the changes in the direction and velocity of movement of the fluid are made as gradual and easy as possible. In previous forms of turbines more or less sudden changes of speed and direction are involved.

"By that I mean to say," explained Doctor Tesla, "that in reciprocating engines with pistons, the power comes from the backward and forward jerks of the piston rod, and in other turbines the steam must travel a zigzag path from one vane or blade to another all the whole length of the turbine. This causes both changes in velocity and direction and impairs the efficiency of the machine. In my turbine, as you saw, the steam enters at the nozzle and travels a natural spiral path without any abrupt changes in direction, or anything to hinder its velocity."

But the Tesla turbine engine, claims the inventor, will work just as well by gas as by steam, for as he points out gases have the properties of adhesion and viscosity just as much as water or steam.

Further, he says that if the gas were introduced intermittently in explosions like those of the gasoline engine, the machine would work as efficiently as it does with a steady pressure of steam. Consequently Tesla declares that his turbine can be developed for general use as a gasoline engine.

The engine is only one application of the principle of Tesla's turbine, because he has used the same idea on a pump and an air compressor as successfully as on his experimental engines. In his office in the Metropolitan Tower he has a number of models. Pointing to a little machine on a table, which consisted of half a dozen small disks three inches in diameter, he said: "This is only a toy, but it shows the principle of the invention just as well as the larger models at the power plant." Tesla turned on a small electric motor which was connected with a shaft on which the disks were mounted, and it began to hum at a high number of revolutions per second.

"This is the principle of the pump," said Tesla. "Here the electric motor furnishes the power and we have these disks revolving in the air. You need no proof to tell you that the air is being agitated and propelled violently. If you will hold your hand down near the centre of these disks—you see the centres have been cut away—you will feel the suction as air is drawn in to be expelled from the outer edges.

"Now, suppose these revolving disks were enclosed in an air-tight case, so constructed that the air could enter only at one point and be expelled only at another—what would we have?"

"You'd have an air pump," was suggested.

"Exactly—an air pump or a blower," said Doctor Tesla. "There is one now in operation delivering ten thousand cubic feet of air a minute."

But this was not all, for Tesla showed his visitors a wonderful exhibition of the little device at work. "To make a pump out of this turbine," he explained; "we simply turn the disks by artificial means and introduce the fluid, air or water at the centre of the disks, and their rotation, with the properties of adhesion and viscosity immediately suck up the fluid and throw it off at the edges of the disks."

The inventor led the way to another room, where he showed his visitors two small tanks, one above the other. The lower one was full of water but the upper one was empty. They were connected by a pipe which terminated over the empty tank. At the side of the lower tank was a very small aluminum drum in which, Tesla told his visitors, were disks of the kind that are used in his turbine. The shaft of a little one twelfth horsepower motor adjoining was connected with the rotor through the centre of the casing. "Inside of this aluminum case are several disks mounted on a shaft and immersed in water," said Doctor Tesla. "From this lower tank the water has free access to the case enclosing the disks. This pipe leads from the periphery of the case. I turn the current on, the motor turns the disks, and as I open this valve in the pipe the water flows."

THE MARVELLOUS TESLA TURBINE

The 200-horsepower engine, which a man could lift with one hand.

How the Tesla Turbine compares in size with a man.

THOMAS A. EDISON AND HIS CONCRETE FURNITURE

The white cabinet is a piece of Edison's poured concrete furniture, while the other one is the ordinary wooden phonograph cabinet.

MODEL OF EDISON POURED CONCRETE HOUSE

This little house, which stands on a table in Edison's laboratory, shows what he expects to do with the poured concrete house.

He turned the valve and the water certainly did flow. Instantly a stream that would have filled a barrel in a very few minutes began to run out of the pipe into the upper part of the tank and thence into the lower tank.

"This is only a toy," smiled the inventor. "There are only half a dozen disks—'runners,' I call them—each less than three inches in diameter, inside of that case. They are just like the disks you saw on the first motor—no vanes, blades or attachments of any kind. Just perfectly smooth, flat disks revolving in their own planes and pumping water because of the viscosity and adhesion of the fluid. One such pump now in operation, with eight disks, eighteen inches in diameter, pumps 4,000 gallons a minute to a height of 360 feet.

"From all these things, you can see the possibilities of the new turbine," he continued. "It will give ten horsepower to one pound of weight, which is twenty-five times as powerful as many light weight aeroplane engines, which give one horsepower of energy for every two and one half pounds of weight.

"Moreover, the machine is one of the cheapest and simplest to build ever invented and it has the distinct advantage of having practically nothing about it to get out of order. There are no fine adjustments, as the disks do not have to be placed with more than ordinary accuracy, and there are no fine clearances, because the casing does not have to fit more than conveniently close. As you see, there are no blades or buckets to get broken or to get out of order. These things, combined with the easy reversibility, simplicity of the machine when used either as an engine, a pump or an air compressor, and the possibility of using it either with steam, gas, air, or water as motive power, all combine to afford limitless possibilities for its development."

Doctor Tesla calls the invention the most revolutionary of his career, and it certainly will be if it fulfils the predictions that so many eminent experts are making for it.

It is interesting to think that although this latest and most modern of all steam engines is a turbine, the first steam engine ever invented, also was a turbine.

Though most of us usually think of James Watt as the inventor of the steam engine, he was not the first by any means, for the very first of which history gives us any record was a turbine, which was described by Hero of Alexandria, an ancient Egyptian scientist, who wrote about 100 B.C.

Hero's engine was a hollow sphere which was made to turn by the reaction of steam as it escaped from the ends of pipes, so placed that they would blow directly upon the ball.

Centuries later—in 1629, about the time the New England States were being colonized—a scientist named Branca made use of the oldest mechanical principle in the world—the paddle-wheel—which, turned by the never-ceasing river, goes on forever in the service of mankind. Branca's invention was simply a paddle-wheel turned by a jet of steam instead of by a water current. The engine was really a turbine, for that type is simply a very high development of this idea—the pushing power of a fluid on a paddle-wheel.

The picture of Branca's crude machine shows the head and shoulders of a great bronze man suspended over a blazing wood fire. Evidently it is intended to convey the idea that the figure's lungs are filled with boiling water, for he is pictured breathing a jet of steam on to the blades of a paddle-wheel, the revolving of which sets some crude machinery in motion.

After Branca, however, the turbine dropped from view and what few inventors did experiment with steam worked on the idea of a reciprocating engine.

The principle of the reciprocating engine, as most boys know from their own experiments with toy steam engines, and as was discovered by Watt, is simply the utilization of the power of steam for expanding with great force when let into first one side, and then the other side of the cylinder. Thus, as the steam expands, it pushes the piston back and forth at a high rate of speed, transmitting motion to shafts and flywheels.

In 1888 the world was ready for a bigger and more powerful type of steam engine; and C. A. Parsons, an Englishman, and Dr. G. de Laval of Stockholm, brought forth successful turbines at about the same time.

The machines were developed to a high state of efficiency, and are still in general use, although most turbines for driving heavy electrical machinery in the United States are the great Curtiss engines, which are a combination of the principles of both the De Laval and Parsons machines. All of them are run by the old principle of the water-wheel. Instead of the steam being turned into a cylinder to push the piston, it is turned into a steel drum or casing in which wheels or disks are mounted on the central shaft. All along the edge of these wheels are hundreds of little vanes or blades or buckets against which the steam flows from many nozzles placed all around the inside of the casing. The steam flows with great force, and naturally pushing against the blades, starts the wheels and the engine shaft to revolving. After expending its force on the blades that turn the steam passes on to a set of stationary blades which then shoot it out against the next set of moving blades.

In the Curtiss turbine the wheels at one end of the shaft are smaller than those at the other, and the steam enters at the small end, where it is under heavy pressure. After having expended its force on the blades of the first wheel, the steam passes through holes in a partition at the side and zigzags back so that it strikes the vanes or blades on the next larger disk. It then repeats the process, expands a little, and goes to a larger disk. Finally, by the time the steam has expanded to its full capacity, the greater part of its force has been expended against the disks of the turbine.

THE CURTISS TURBINE

Diagram of Steam Diaphragm Showing Nozzles and Fixed and Moving Blades

A—Single stage turbine wheel. B—Steam nozzles. B´—Steam exhausts. C—Moving blades. D—Stationary blades.

From this we see the main points of difference between reciprocating engines and turbines, and between most turbines and Tesla's invention.

While most turbines take advantage of the expansive power of steam, the main idea is to make use of the velocity of the vapour as it is driven from a set of nozzles around the turbine wheel, under high pressure.

Also it will be seen that Tesla's invention is a turbine in form, but that it is entirely different from either of the two earlier types, because instead of giving the steam something to push against, it is allowed to follow its own natural course around between the smooth disks, and drag them after it.

Some kind of a crank motion is necessary in all reciprocating engines, to convert the backward and forward movement of the piston to the rotary motion of the shaft, but this is done away with entirely in the turbine. What engineers call a "direct drive" is substituted in its place. In other words, the turbine wheels or disks, fastened to the shaft, turn it, and drive the machinery directly from the source of power. The speed of the machine is regulated by gears.

The great advantage of the "direct drive," particularly for big steamships and for turning big electric dynamos, will be plain to every boy when he thinks of the long narrow body of a ship in which can lie the turbine engines working directly on the propeller shafts (with the exception of certain gears, of course, for regulating the speed) instead of the big flywheels, and flying cranks of marine reciprocating engines. Also with dynamos it is just as important to have the power applied directly to save space and increase the general efficiency of the machine.

The greatest disadvantage of the usual kinds of turbines for most machinery, including steamships, is the fact that they cannot be reversed. To solve this difficulty, all the great ocean and coast liners, battleships, cruisers, and torpedo boats that are equipped with turbines have two sets of engines, one for straight ahead and one for backward.

With the Tesla turbine this disadvantage, as we have seen, is entirely done away with, and the one turbine can be reversed as easily and simply as it can be started.

And so, while we are waiting for the world-moving wireless transmission of power and for the completion of Tesla's invention for safe and stable airships, we can look for the speedy development of his turbine in practically all departments of mechanical engineering.

CHAPTER IX
THE ROMANCE OF CONCRETE

THE ONE-PIECE HOUSE OF THOMAS A. EDISON, AND OTHER USES OF THE NEWEST AND YET THE OLDEST BUILDING MATERIAL OF CIVILIZED PEOPLES SEEN BY THE BOY AND HIS SCIENTIFIC FRIEND

WHILE we are looking around at all these epoch-making inventions let us follow our friendly scientist and his boy companion to one of the big cement shows held in the various large cities of the United States every year, for a glance at some of the uses of reinforced concrete in modern engineering and building. For the boy who intends to become a civil engineer this wonderful material will have an especial interest, because its successful use in all of the greatest engineering works going on to-day has brought it to the front as the modern substitute, in a great many cases, for wood, brick, or expensive stone and steel structures.

WHAT ONE SET OF BOYS DID WITH CONCRETE

This Indian tepee of concrete was made by the boys of Dr. W. A. Keyes' summer school, at Sebasco, Maine.

The picture on the top shows the method of construction.

MASSIVE CONCRETE WORK

Completed side walls of solid concrete in the Gatun Locks of the Panama Canal.

A LEVEL STRETCH OF CATSKILL AQUEDUCT

Showing completed section as well as forms for the concrete.

On entering the cement show our friends saw on every side long rows of booths showing models of structures and articles that could be made of concrete. There were models of houses, subways, dams, bridges, dock works, retaining walls, sewers, bridges, pavements and even boats and furniture. In fact, so the men in the exhibition booths said, concrete can be used for practically every building purpose where strength, lasting qualities, and resistance to heat and cold are needed. "This is the concrete age," they declared. "Concrete is fireproof, waterproof, sanitary, and resists frost when properly used. Our timber supply is decreasing, the supply of iron ore for structural steel is limited, and stone is expensive; so concrete, reinforced with steel, and used by engineers who understand their business, will be the greatest building material of the future."

These are the things that the enthusiasts at all the concrete shows say, but they admit that there are certain kinds of construction in which concrete is not as effective as steel or granite. Also they say that the use of reinforced concrete requires the highest type of engineering skill, and a complete understanding of the technicalities of the subject.

One of the places where we know concrete best is in pavements and sidewalks, and several of the booths exhibited samples of such work. To show its strength the men in charge piled on weights, struck the slabs with hammers, or subjected them to any kind of hard usage suggested by the crowd. Then, too, there were sections of concrete buildings, and exhibitions of various systems of reinforced concrete construction. With these there were concrete chimneys, portable concrete garages, railroad ties, and what not.

"Oh, but look here," broke out the boy as he led his older friend about. "Here's a perfect model of a house."

"Yes," answered the man, "that is a model of the famous Edison poured cement, or 'one-piece' house, the latest invention of our great American inventor."

There the little building stood, perfect in every way, surrounded by a model concrete wall, a beautiful lawn, and approached by fine concrete walks and driveways.

"This model," explained the scientist, "represents what Thomas A. Edison is trying to get time to accomplish for workingmen and their families. Instead of being built piece by piece, the house is supposed to be made all at one time by pouring the concrete into a complete set of moulds. This house is so interesting that we shall look at it much closer a little later on."

"And here," said the boy; "what's this?"

He had paused before a perfect model of the Gatun locks of the Panama Canal, where the world's greatest work in concrete, or any other kind of masonry, is being carried on. The work is greater than the Pyramids of Egypt or the Great Wall of China. Though we will not bother ourselves much with figures, it will give an idea of the size of the job on the canal when we realize that it will require 8,000,000 cubic yards of concrete, and more then 900,000 tons of Portland cement.

In all there will be six great locks for the transportation of our ships from the Atlantic to the Pacific and back. Three of these locks are at Gatun on the Atlantic side of the canal, one at Pedro Miguel, and two at Miraflores. Each lock will be 1,000 feet long, 110 feet wide, and 45 feet deep—and practically all of this is done with concrete. So massive is most of the work that steel reinforcement is only necessary in certain parts of the project. The problem of sinking the great retaining walls to bedrock, and making them strong enough to hold in the face of the tremendous floods of the Chagres River, alone makes one of the most stupendous engineering works ever undertaken by man. Were it not for the use of concrete the cost of the work would be so great as to make it almost impossible of accomplishment.

The model of the Gatun locks showed the boy everything, just as it will be when the canal is opened for traffic in 1913. There was the wide Gatun lake, surrounded by the tropical forests, the great Gatun dam, and the series of locks in one solid mass of concrete. These locks when completed will be 3,800 feet long, and their tremendous height and thickness can be seen from the pictures of the work as it is actually being carried on. In the model there were perfect little ships on the lake and going through the locks.

Besides the many present day uses of cement some of the concrete enthusiasts are suggesting that heavily reinforced concrete be used in place of steel in making bank vaults, as they declare that the material will resist the keen tools and the powerful explosives of bank robbers even more successfully than the hardest steel.

Then too, at the cement show, the boy saw, besides models of big works and examples of all kinds of concrete construction, exhibits of the various methods of placing steel bars and steel network in the cement to make it stronger, and the different machines used in mixing concrete and in making Portland cement, which is the binding element in concrete.

As concrete is a material that can be mixed by an amateur and used for a great many purposes, the booths where mixing and simple uses were demonstrated attracted a great deal of attention. For instance, in the last few years the farmers have found out that they can make watering troughs, drains, floors for stables, hen houses, and even fence posts, of concrete just as easily as they can of wood or iron. Moreover, the articles thus made will last practically forever. All that is needed is a supply of Portland cement, and a little careful study as to the best way of mixing it with the proper amounts of sand and gravel. The amateur has best results if he starts modestly and takes up the use of reinforced concrete after learning how to use the material in its simple form.

One of the most interesting uses of reinforced concrete for the amateur who has learned something of the craft is in making a good, seaworthy rowboat, or even a small motor boat. Poured boats are strong, graceful, and durable. If they are properly made there never is any danger of their leaking, and by a little extra pains it is possible to make them with air-tight compartments so that they are non-sinkable.

The usual method of making concrete boats is very simple. The kind of boat to be duplicated is borrowed and hung on the shore so that it swings free of the ground. Then a mould of clay is built all around it. A strong bank of sand is heaped around the clay, to hold it firm. Then the boat is worked a little each way so that a space of about an inch and a half is left all around between the outside of the boat and the clay. The space between the boat and the clay is the space into which the concrete is poured for sides and bottom after the reinforcing rods have been properly inserted. After the whole thing has stood a day or so the inside boat is taken out and the clay mould broken down, revealing a complete concrete hull.

Thus, we see that concrete can be used as a building material in practically any kind of construction, that it is easily handled since all that is necessary is to pour it into the moulds after the engineers have properly placed the reinforcement, and that it can be cast in practically any decorative design just as easily as plain. Add to this the fact that concrete is cheaper than stone or steel, and that it is practically indestructible when properly handled, and it is easy to see the reason for calling this the cement age, and concrete the building material of the future.

After the Panama Canal, the greatest engineering feat in which concrete figures as one of the chief materials used, is the Catskill aqueduct, by which water from four watersheds in the Catskill Mountains of New York State is to be piped to all five boroughs of New York City. The Ashokan reservoir, near Kensington, N. Y., was the first part of the work to be taken up, together with the Kensico storage reservoir twenty-five miles from New York, several smaller reservoirs, and the aqueducts to carry this water from the mountains to every home in greater New York. The dam and containing walls of the Ashokan reservoir are all made of reinforced concrete, and the size of the lake and the strength of the walls can be appreciated when one thinks that the 130,000,000,000 gallons of water it holds in check would cover all Manhattan Island with twenty-eight feet of water. A large part of the aqueduct proper, through which this great stream of water is carried from the mountains, under the Hudson River, and to the city where it runs more than a hundred feet below the street level, is made of reinforced concrete.

For other examples of the use of this material in big engineering works a boy has only to look around him. There are the tunnels under the rivers around New York, the New York subways, the Philadelphia and Boston subways, the Detroit River tunnel, bridges, culverts, big piers and other dock works, miles of concrete snowsheds along the lines of the railroads that cross the continental divide of the Rocky Mountains, and in fact practically every big structural undertaking.

Almost anywhere we look these days we see a big machine crushing rock, mixing it with sand and mortar, and turning out concrete to be shovelled into a hole and perhaps used far below the surface by "sand hogs" working under compressed air, or hoisted to the towering walls of some great office building or factory that is being constructed of the artificial stone.

We are familiar with the falsework of a concrete building under construction. It is all, apparently, a maze of wooden beams that look like scaffoldings, and yet they seem to make the outlines of the building. This maze of woodwork, seemingly so lacking in plan or system, as a matter of fact is a triumph of engineering skill, for it is the mould for the building, and was all built by the most careful plans as to strains, stresses, floor loads, etc.

First, however, before building the mould for a residence, school, theatre, office building, or factory, the engineer decides what strength his foundations must have. The foundation for a small residence is an easy matter, but when it comes to a big factory, or an office building of a dozen stories or so, the most careful work must be done beforehand. In the old days, when it was desired to sink the foundations of a building down to bedrock, they used steel or wooden piles, but these will rust or rot, and the modern way is to use concrete piles. Either the great poles are moulded first and sunk like the ordinary wooden ones, or a pipe with a sharpened point is sunk and the concrete deposited in it by buckets designed for the purpose. Once these piles are driven, they are there for all time, if the work is done properly, and the engineer can be sure that his building is as good as if resting on bedrock.

From then on the erection of a reinforced concrete building is a most intricate matter, because while concrete in itself is a very simple substance, its use in buildings is a highly developed science. Of course there are many different methods of using concrete, and each one prescribes a different kind of steel network for the reinforcement. Then, too, some engineers cast parts of their buildings separately and put them in place after they have set, while others run the concrete for beams, floors, and walls into moulds, built right where those parts are to be in the finished structure. In laying the steel reinforcing rods, before the concrete is poured, the engineer sees that they make a perfect network so as to take care of all the strains, just as they will be put upon the building when it is completed. It is in the proper placing of reinforcement that the greatest engineering knowledge is needed in this kind of building.

As the wooden moulds for the first foundation beams and girders are completed and the reinforcement is placed, the concrete is poured in. The subcellar or cellar floor mould then is laid, the reinforcement placed and the concrete run in. Next the moulds for the cellar walls are built and perhaps the moulds for the beams and girders for the first floor. The reinforcing rods are placed in these moulds and the concrete run in, and so on, a story at a time, or a small section at a time, until the structure reaches the height called for in the plans, and it stands completed. As the building progresses and the concrete on the lower floor sets, the moulds can be taken down and used on higher stories. Concrete is even used for the roofs of buildings, as it can be moulded right in place or set up in slabs that can be later cemented together.

When properly used reinforced concrete is absolutely fireproof, so it is coming into extensive use in the construction of schools, theatres, warehouses, factories, and all other such buildings where a great height is not required. So far, none of the great skyscrapers has been built of reinforced concrete, although office buildings of sixteen stories have been erected with complete success.

There is still another method of using concrete as a building material. This is in the form of building blocks, and doubtless all who read this will recall seeing many beautiful residences built of blocks of stone that on closer inspection proved to be concrete. The blocks can be cast in any size or form and used in just the same way as structural stone.

Now, after having looked about the city and having seen the numerous ways that concrete is used as a building material, we come back to the very latest thing in the use of this man-made stone—the "one-piece" or poured house.

For a good view of it let us take a little jaunt out to West Orange, N. J., with the scientist and look into the library of Thomas A. Edison's laboratory, where we will see a perfect model of this marvel of invention. It is practically the same as the one at the cement show. Standing in the centre of the great room where Edison works is this perfect little cottage, about the size of a large doll's house. It represents not only Edison's latest invention, but also his favourite scheme. In years to come, when the boys who read this are grown men, it will probably be no novelty to build houses by pouring them all at once into a steel mould, but just at present it is one of the most startling developments in an age of epoch-making inventions.

Every boy knows that Edison has never followed the ideas of others in working out his inventions, and the poured house is no exception to his rule. It will be interesting to take a little look back over a part of Edison's life and see how he came to enter the cement-making business, and how, when he had his process down to a fine point, he said to himself, "It is cheap and easy to build a house or an office building of concrete in sections, why not build it all in one piece?"

We shall see that no sooner had he asked himself this startling question than he began by making models, and satisfied himself that it was not only possible, but one of the cheapest and best methods of making small, simply arranged houses, such as could be bought or rented for a small sum.

Although Edison has within the last few years brought his idea to a state where it can be put to practical use, he himself is not trying to push it commercially, as he has his other great inventions like the phonograph, storage battery, and the motion-picture machine. In fact, he is content to let it be worked out by others just so long as it fulfills his idea of giving to workingmen good houses at a low price.

"Years ago, long before Edison had retired from active business affairs to give his whole attention to scientific research," said the scientist, as he and the boy walked about the laboratory, "he became interested in metallurgy, just as he was and always is interested in every other science where great difficulties must be overcome. In those days iron and steel were not used as extensively as they are now, but the scientists and leaders in the big industries saw that the day was coming when far, far greater quantities of iron ore would be needed to supply the great demand for steel to build skyscrapers, ships, machinery, and so on. Men were going farther and farther away in their search for iron ore, but Edison, with his never failing originality, said to himself that it was likely there was plenty of iron ore right around his laboratory in New Jersey if he only knew how to get at it.

"For one thing," continued the boy's friend, "Edison had seen on the ocean beaches great stretches of white sand with millions and millions of little black particles sprinkled through them. He knew that the specks were pure iron ore. You can prove this to yourself by simply holding a good magnet close to a pile of such sand, and watching the iron particles collect."

It was Edison's idea to concentrate the iron ore found in the earth, in just this way, for he had sent out a corps of surveyors who had reported vast quantities of low-grade ore in most of the Atlantic Coast States. Low-grade ore is that which contains only a small percentage of the metal desired, and hence it does not pay to smelt it, unless a very cheap process can be found. Edison thought he had a process cheap enough, for he simply intended to grind the mountains to sand and take out the particles of iron by running it through a hopper with a high-power magnet at the mouth.

The process sounds simple, but the machinery required was very complicated, to say nothing of being extremely heavy. Edison set up his mill in the mountains of New Jersey and started to blast down the cliffs of low-grade ore and run them through a series of gigantic crushers that ground them to a fine powder. The iron particles, called concentrates, after being extricated were pressed into briquets ready for delivery to the foundry.

After having spent close to $2,000,000 on the experiment, and satisfactorily proving its mechanical success, the discovery of vast quantities of high-grade ore in the Messaba range of Minnesota forced Edison to close his plant. "This would have been a crushing failure to most men," added the scientist, "but Edison's only comment was a whimsical smile. Indeed, even on his way home after closing his plant, Edison was planning new and more important activities, for with his experience at rock crushing he was satisfied he could enter the field as a maker of the building material called Portland cement."

At that time cement and concrete were even less used than were steel and iron, but Edison for many years had seen that in the future they would take the place of wood, stone, and brick.

"Well-made concrete, employing a high grade of Portland cement," said Edison on one occasion, "is the most lasting material known. Practical confirmation of this statement may be found abundantly in Italy at the present time, where many concrete structures exist, made of old Roman cement, constructed more than a thousand years ago, and are still in a good state of preservation.

"Concrete will last as long as granite and is far more resistant to fire than any known stone."

But Edison had something more than a successful business in mind when he returned from his rock-crushing plant, for he intended setting up cement-making machinery such as had never before been seen. With this end in view he began to read up on the subject, just as we have seen the Wright brothers read up on aviation. Incidentally, as an indication of the manner in which this wizard works, it may be said that all this time Edison was perfecting his new storage battery.

One big improvement upon the usual process in the manufacture of cement, planned by Edison, was that the grinding should be so fine that 65 per cent. of the ground clinker should pass through a 200-mesh screen instead of only 75 per cent. as is the usual rule. Thus, Edison made into cement 10 per cent. more material that other manufacturers sent back to be ground over again.

The success of Edison's Portland cement plant is not matter for our attention here, so we will pass over those busy years to the time of Edison's retirement to devote all his time to scientific research.

For many years he had watched the cities grow, had seen the great tenements become more crowded, and less comfortable each year. He had seen the children playing in the streets, and had compared their lives to the happy lives of the children whose parents could afford to live away from the great cities, where boys could have yards to play in. He decided that the boys of the city streets would have a far better time, that their mothers and fathers would have a far more cheerful life if they could live in comfortable little houses in the country with yards, and gardens, and plenty of room for every one.

Edison saw that what was needed was a building material cheap enough, and a method of using it cheap enough, so that dwellings could be put up at a cost that would place them within the means of workingmen and their families.

Concrete, he decided, was the material to solve the problem, and Edison set himself to the task of making houses poured complete into one mould so as to make the cost of labour as low as possible. The "one-piece" house was an assured thing from that time on. All that remained was for the "Wizard of Orange," as he is called, to work out the difficult details of a properly mixed cement and a practical system of moulds.

An incident that occurred at the time of the failure of his ore crushing plant in the New Jersey mountains was one of the things that brought the whole situation home to him. When the plant was closed and the buildings vacated, the fire insurance companies cancelled the policies, declaring that the moral risk was too great.

The inventor's reply was short and to the point. He made no protest against the cancellation of his policies, but simply said he would need no more policies, as he would erect fireproof buildings in which there would be no "moral risk."

This promise of Edison's, made at the time of his so-called failure and pondered during the years of his tremendous activities, was not redeemed until he had retired from the business of invention as a means of gaining riches. "I am not making these experiments for money," Edison has said many times. "This model represents the character of the house which I will construct of concrete. I believe it can be built by machinery in lots of 100 or more at one location for a price which will be so low that it can be purchased or rented by families whose total income is not more than $550 per annum. It is an attempt to solve the housing question by a practical application of science, and the latest advancement in cement and mechanical engineering."

HUGE CONCRETE MOULDS AT PANAMA

These great locks are made as monoliths or in moulds of one piece, the whole making the greatest masonry work the world has ever seen.

CONCRETE LOCKS ON THE PANAMA CANAL

The Gatun middle locks, east chamber, looking south from the east bank.

Edison's plan, as we have seen before, was simply to make a set of moulds in the shape of the house he desired to build, run the concrete into them, let them stand until the material had settled, and then take down the retaining surfaces, exposing to view the finished house.

It was contrary to all the previous ideas in building, and was ridiculed by many famous architects. Nevertheless, tremendous obstacles are the stuff upon which Edison's genius feeds, and he only worked the harder to produce a concrete that would be liquid enough to fill all the intricate spaces and turns in the moulds and yet sufficiently thick to prevent the sand or gravel in the concrete from sinking to the bottom. Thus, it first had to run like thin mush and then set in walls and floors harder than any brick or stone. Another of the difficulties to be overcome was to discover a concrete that would give perfectly smooth walls.

Although this may sound very simple, it has not yet been completely worked out in this country, owing to the heavy demands on Edison's time. The perfected process, however, will be made known just as soon as the inventor can find time to complete certain small details that he wants to clear up before giving the system to the world. A French syndicate working along Edison's ideas for a poured house has made some progress and it is reported they have constructed two attractive dwellings with considerable success. One of these is at Santpoort, Holland, and the other near Paris.

Whether the houses are poured completely in one mould, or whether they are built a story at a time on different days, this newest form of house building is carried on along about the same lines.

"Let us just suppose," said the scientist, "that we are standing on a building site in some pretty suburb of a great city. We will also suppose that an Edison poured house is to be erected there. Plans are drawn beforehand for a small house of simple arrangement and a set of steel moulds in convenient sizes are turned out. These moulds all have connections so they can be set up and joined together in one piece. First, we see that a solid concrete cellar floor, called the 'footing', has been laid down just the size and shape of the house. A crowd of skilled workmen quickly set up the moulds on this footing and lock them together. The moulds make one complete shell of the house, from cellar to roof, just as it will appear when completed. Reinforcing rods are placed in the mould so that they will be left in the concrete walls, floors, etc., of the house after the steel shell is taken away.

"Nearby we see a few more skilled workmen mixing the concrete in great vats. When the mould and the material are ready we see the concrete taken to a tank on the roof and poured into troughs which carry the stuff to a number of different holes through which it flows into the mould. We hear it splash, splash, splash as it gradually fills every space in the shell, and finally after six hours or so it overflows at the roof. The main part of the work is now done and we can go away for a few days while the liquid in the shell sets, or turns to the hardest kind of stone.

"After about six days we return to see the moulds unlocked, taken down and the complete house standing ready with walls, floors, stairways, chimneys, bathtubs, stationary tubs in the cellar, electric-wire conduits, water, gas and heating pipes all complete. In making the moulds the spaces for bathtubs, wash-tubs, electric wiring and piping for gas, water, and heat, are just as carefully arranged as walls and floors. The only work necessary after the concrete has set is to put in the doors and windows, install the furnace and necessary fixtures for heating, lighting and plumbing and connect them up ready for use. No plaster is used in these houses, but the walls can be tinted or decorated just as the landlord or occupant desires."

The boy's friend went on to say that one might think that this was about as far as science could carry the use of concrete, but Edison said to himself: "If we can make houses, why can't we make furniture?" and he set about experimenting with poured furniture. He obtained some wonderful results with this newest use of concrete, and in his Orange laboratory he has several cabinets, chairs, and other articles of furniture that are every bit as attractive to look at as wooden furniture and that are practically indestructible.

"And my concrete furniture will be cheap, as well as strong," says Edison. "If I couldn't put it out cheaper than the oak that comes from Grand Rapids, I wouldn't go into the business. If a newlywed starts out with, say, $450 worth of furniture on the installment plan, I feel confident that we can give him more artistic and more durable furniture for $200. I'll also be able to put out a whole bedroom set for $5 or $6."

At present the weight of this concrete furniture is about one third greater than wooden furniture, but Edison is confident he can reduce this excess to one quarter. The concrete surface can, of course, be stained in imitation of any wood finish. The phonograph cabinet shown at the left of Edison in the picture opposite page [281] has been trimmed in white and gold. Its surface resembles enamelled wood. The cabinet at his right is the old style wooden type.

This concrete cabinet easily withstood the hard usage of shipment by freight for a long distance.

THE WORLD-WIDE USE OF CONCRETE

Courtesy of the Atlas Portland Cement Co.

An eight-story all-concrete office building under construction in Portland, Maine.

Courtesy of the Atlas Portland Cement Co.

A perfect little model of the great Gatun Locks of the Panama Canal.

THE CATSKILL AQUEDUCT, ONE OF THE WORLD'S GREATEST CONCRETE WORKS

Laying a level section of the great concrete tunnel through which New York City is to get its drinking water.

THE AQUEDUCT DEEP UNDER GROUND

A partially completed section showing the concrete work. Note the size of the tunnel.

Of course, the poured concrete furniture is made in just the same way as the houses except that it is a much simpler process. It is a very easy matter to set up a steel mould for a chair, a cabinet, a dresser, or a bedstead, whereas a house, with its tubs, conduits, stairways, hallways, doorways, window frames, plumbing system, etc., is a most complex matter, requiring a set of moulds that could be put together properly by only a man who combined the highest abilities of an architect, a builder, an engineer, and a mechanic. Although concrete has been used for many years in making garden furniture, Edison's plan for making finished indoor pieces with it is entirely new.

But to return to the houses; Edison says it is just as easy to make poured dwellings in decorative designs as in plain ones. It is only necessary to have the moulds cast in the desired shape. It is his idea to have all the poured houses pretty as well as perfectly sanitary and substantial. He intends that there shall be many different kinds of moulds, and also that each set of moulds shall be so cast that it can be joined in different ways, in order to give the houses a variety of appearance. Thus, in a small town where a large number of poured houses were set up, there would be no two exactly alike if the owners preferred to have them different.

According to the plans Edison now has on foot, the first complete poured houses will have on the main floor two rooms, the living room and dining room, while on the second floor there will be four rooms, a bathroom and hallway. Of course as the main idea is to give perfectly sanitary and comfortable houses, there will be plenty of windows, for lots of fresh air and sunlight. Edison figures that he can build a house of poured concrete for $1,200 that would cost $30,000 if built of cut stone. Furthermore, he figures that the rent ought to be about $10 per month, as he will only license reputable concerns to use his patents, and his licenses will stipulate the approximate rent that can be charged.

Thus, the high cost of living about which we all hear so much at the family dinner table as well as everywhere else is being attacked by science and invention through a new channel, and Edison's latest invention can be expected soon to give good homes at low rents to thousands of families now paying exorbitant prices for dark stuffy city flats.

It was significant that at the celebration of Edison's sixty-fifth birthday, February 10, 1912, the great American inventor should sit at the head of the table surrounded by his family and associates facing a perfect model of one of his poured cement houses. The chair in which he sat, to all appearances was beautiful mahogany, but in reality was cast in a mould of Edison concrete at the Edison plant. At the place of each guest was a bronze paperweight, appropriately engraved, with Edison's favourite motto:

"All things come to him who hustles while he waits."

HISTORY OF CONCRETE

Although concrete is in truth the newest building material in our time, it is the oldest known to civilization because it was the stuff with which the eternal buildings of ancient Rome were constructed. Even before the Romans used concrete it was used by the Eygptians, more than 4,000 years ago. Every boy will remember from his history classes that the Egyptians, so far as we can learn, were the first people in the history of the world to reach a high state of civilization. Every boy also will remember that the only way we know this is through the evidence of ruins of tombs and buildings. Many of these buildings were made of a material very much like concrete that must have been made in some such manner as concrete is made nowadays.

About 2,000 years later, long after the Egyptian civilization had died, the men of Carthage discovered concrete for themselves and built a marvellous aqueduct 70 miles long, through which water was brought to their city. It was carried across a great valley over about 1,000 arches, many of which are still standing in good condition.

To the Romans, however, we are indebted for some of the best examples of ancient concrete work. They used this material in their wonderful city for buildings, bridges, sewers, aqueducts, water mains, and in fact in a great many of the ways that we have seen it is used to-day. The great Coliseum and the Pantheon at Rome are relics of the skill of the ancient architects in the use of concrete.

Although many historians think that the secret of making cementious building material was lost from the fall of Rome until the middle of the eighteenth century, there are ruins of ancient castles which stood in mediæval times in Europe which indicate at least some use of concrete.

The real discoverer of natural cement in our modern times though, was John Smeaton, who will be remembered by the readers of "The Boy's Second Book of Inventions" as the man who built the first rock lighthouse at Eddystone, England, in 1756. In his great work he discovered a kind of limestone with which he could make a cement that would set, or harden, under water. His discovery was hailed as the recovery of the secret of the ancient Romans of making hydraulic cement. It was so called because it would harden under water.

In 1796, Joseph Parker, another Englishman, made what he called Roman cement. Several others followed, and in 1818 natural cement was first made in the United States by Canvass White near Fayetteville, N. Y. The material was made from natural rock and was used in the construction of the Erie Canal.

All of these early cements are called natural cements by engineers nowadays, because they were made from natural rock. It was only necessary to find a clayey limestone which contained a certain percentage of iron oxide and two other minerals known as silica and alumina. The limestone was crushed to a convenient size and was burned in a kiln. The heat turned the stuff into cinders which, when ground to a fine powder and mixed with water, would make a cement that would harden under either air or water very quickly, and last for practically all time. Just for the sake of those who have studied chemistry we will say that in this process the heat drives off the carbon dioxide in the limestone, and the lime, combining with the silica alumina and iron oxide, forms a mass containing mineral properties called silicates, aluminates, and ferrites of lime. These properties mixed with the water make natural cement. In the United States, natural cement was called Rosendale cement, because it was first made commercially in a town of New York State by that name.

The supply of natural cement, however, is limited, because the proper kind of limestone is only found in a few places. Consequently, when an artificial mortar called Portland cement was invented in 1824, the world took a step forward that could not be measured in those days.

Most authorities give the credit for the invention to Joseph Aspdin, a bricklayer of Leeds, England. He took out a patent on the material and in 1825 set up a large factory. In 1828 Portland cement was used in the Thames tunnel, making the first time that the material figured in any big engineering work. In those days even the most enthusiastic supporters of cement little dreamed that in this modern age it would be the material that would make possible such tremendous victories over the obstacles of nature as the Panama Canal, the tunnels under the rivers that surround New York and the great dams that hold back the waters all over the country.

Aspdin, however, is not given the credit for the invention of Portland cement by all authorities, as some claim that Isaac Johnson, also an Englishman, who early in 1912 died at the age of 104, was really the first man to invent a practical, commercial, artificial cement.

The advantage in Portland cement is that it can be made of a number of different kinds of earth, to be found in many different parts of the world, and makes a far stronger rock. It sets more slowly than natural or hydraulic cement, but is more satisfactory for use in reinforced concrete work. In the Lehigh Valley, where about two thirds of the Portland cement used in the United States is made, the raw material is a rock, called cement rock, and limestone. In New York State they make Portland cement of limestone and clay; in the Middle West they make it of marl and clay, while in other Western States they make it of chalk and clay. In Europe slag is sometimes used. The artificial product contains lime oxide, silica, alumina, iron oxide, and other minerals in varying quantities, but the necessary ones are silica, alumina, and lime. In making Portland cement the raw material is ground into a fine powder and poured into one end of a long cylindrical kiln which looks like a smokestack lying on its side. Powdered coal is shot into the kiln, where it is kept burning, at a heat of about 2,500 to 3,000 degrees Fahrenheit. After the raw material has been burned thoroughly and is taken from the kiln it looks like little cinders or clinkers about the size of marbles. The cement clinker is then cooled and ground to a powder, after which it is stored away for a little while to season.

The first Portland cement ever made in the United States was turned out by David O. Saylor, of Coplay, Pa., in 1875, but the development of the new industry was very slow, as builders and engineers seemed to be blind to the great possibilities of the material that built Imperial Rome. In 1890, nearly twenty years after the process was introduced in America, only 335,500 barrels of Portland cement were manufactured in this country. The country woke up to the situation a few years later, and in 1905 there were manufactured in the United States 35,246,812 barrels of Portland cement. In 1911 the industry turned out the stupendous total of 77,877,236 barrels.

This was because the age of concrete had dawned on the world and man had learned in those years that by mixing gravel and sand with cement he could make a material cheaper, more easily handled, and far more lasting than wood, brick or some stone.

As Edison once said to some of his associates:

"I think the age of concrete has started, and I believe I can prove that the most beautiful houses that our architects can conceive can be cast in one operation in iron forms at a cost, which, by comparison with present methods, will be surprising. Then even the poorest man among us will be enabled to own a home of his own—a home that will last for centuries with no cost for insurance or repairs, and be as exchangeable for other property as a United States bond."

The technical definition of concrete is as follows: "Concrete is a species of artificial stone formed by mixing cement mortar with broken stone or gravel. Cement is the active element called the matrix and the sand and stone forms the body of the mixture called the aggregate."

The ingredients are mixed in different proportions for different work. A common proportion is 1 part cement, 2 parts sand, and 5 parts broken stone or gravel. Cement users speak of this as a "1: 2: 5 mixture." Sometimes the gravel is left out and a mixture of 1 part cement to 3 or 4 parts sand is made. The cement binds the mass together and sand fills up any little vacant spaces about the gravel, making what is called a dense mixture.

THE SILENT KNIGHT MOTOR

Two views of the latest automobile engine. At the top can be seen the sliding sleeves, the inlets and outlets which do away with valves.

A PORTABLE ARMY WIRELESS OUTFIT

The Signal Service is rapidly increasing its wireless equipment for use on land.

THE WIRELESS IN THE NAVY

Practically all of Uncle Sam's warships and Navy Yards now are equipped with wireless, and a regular navy wireless operators' school is maintained at the Brooklyn Navy Yard.

From the use of concrete it was only a short step to reinforced concrete, or, concrete braced on the inside with iron or steel rods. It is sometimes called concrete steel, ferro-concrete, and armoured concrete. If we asked an engineer the idea in using reinforced concrete he might say to us that the steel when imbedded, united so closely with the concrete as to form one single mass of very great strength. Steel rods add to the tensile strength of concrete which alone has a tremendous strength under compression. In other words, steel does not break nor stretch easily; that is, it has great tensile strength. Concrete has great strength under compression; that is, it will hold up an enormous weight without crushing. Thus, a concrete beam alone might crack on the bottom, because it has not as great tensile strength as steel. But, if we put steel rods into a concrete mould, an inch or so from the bottom, turn out a reinforced concrete beam, for instance, and place it in the building, with the reinforcement at the bottom, we use a beam in which the strength of the concrete and iron is combined. Thus, when a great weight is placed on the top of the beam the concrete resists the compression of the weight, and the reinforcement at the bottom, by its tensile strength, prevents the beam from cracking where the strain of the weight is greatest.

That is what the engineer might tell us is the theory of reinforced concrete, and the practice requires the highest engineering skill and technical knowledge, but in the simplest terms, it is concrete, braced by an imbedded skeleton of steel. In actual practice the reinforcing rods run both ways, or diagonally, just as the engineers decide it is necessary to resist the particular kind of stress that the wall or beam must withstand.

Reinforced concrete was first used, so far as known, by M. Lambot, who exhibited a small rowboat made of that material at the World's Fair in Paris, in 1855. The sides and bottom of the boat were 1-1/2 inches thick, with reinforcement of steel wires. The boat is still in use at Merval, France. F. Joseph Monier, however, is called the "father of reinforced concrete," as he took out the first patent on it in France in 1865. Monier was a gardener and had experimented with large urns for flowers and shrubs. He wanted to make his pots lighter but just as strong, so he tried making some of concrete with a wire netting imbedded in the material. But even then the world did not realize that his accomplishment was more important to mankind than a great many of the wars that had been fought, and little was done with concrete as a building material until the Germans developed it.

Reinforced concrete was not used in the United States, according to the best records, until 1875, when W. E. Ward, without having studied the subject very carefully, built himself a house of it, in Port Chester, N. Y. He made the whole thing, including foundation, outside walls, cornices, towers, and roof of reinforced concrete, placing the steel rods where his own good judgment told him they would do the most good. About this time the Ransome Cement Company began to use the material for building, and put up a great many strong and beautiful structures, still to be seen in California and elsewhere.

Finally, bit by bit, in the face of opposition of all kinds, reinforced concrete came to be recognized by architects, engineers, and builders as one of the best materials for certain kinds of work. To-day we find that most of the predictions of the early enthusiasts have been fulfilled and that the age of concrete has dawned. That it will be used even more extensively in the future, as men learn more and more about this wonderful artificial stone, is certain.

CHAPTER X
THE LATEST AUTOMOBILE ENGINE

OUR BOY FRIEND AND THE SCIENTIST LOOK OVER THE FIELD OF GASOLINE ENGINES AND SEE SOME BIG IMPROVEMENTS OVER THOSE OF A FEW YEARS AGO

WHILE we are following the conversations of the scientist and his young friend about new inventions, we must not overlook some of their most interesting times in keeping abreast of the vast improvements that are being made every year—almost every day—in the inventions of a dozen years ago.

For instance, there is the gas engine. Ten years ago it was a very imperfect machine, as every boy who has heard the old jokes about "auto-go-but doesn't," "get a horse," etc., will remember.

Then there is the wireless telegraph. No invention of recent years has shown a more remarkable development than that of Guglielmo Marconi for sending messages without wires.

But these are only a few of the things that the two friends talked about. They looked into the wonderful advancement in the art of photography about which every boy knows something, and they investigated the latest achievements of science in electric lighting. Ten years is a very short time, even in this fast moving age of ours, and we shall see that many inventions made years ago are still being worked upon by the original inventors and others.

First, let us see a few of the ways the gas engine has been improved, for we are all more or less familiar with it in automobiles, motor boats, or the hundred and one other places that it has become an invaluable aid to man in carrying on the world's work.

Our young friend brought up the subject one day when he asked the scientist for a few pointers on getting better results with his motor-boat engine.

"We will look it over together," said the man. "Of course you know that every gasoline engine has its own peculiarities, and crankinesses, so it's hard to tell just what's the matter with one until you see it. I don't know very much about them; I wish I knew more, but I have been talking with my automobile friends a good deal lately about the new motor invented by Charles Y. Knight."

"Oh, I know," replied the boy, "it is called the 'Silent Knight' motor because it doesn't make any noise, and it is used on a great many high-priced automobiles."

"That's it. If you like we will go and have one of these engines explained to us. At any rate the automobile man can tell you more about your motor-boat engine than I can."

The expedition was made shortly after the conversation. "You understand, of course," said the scientist on the way, "that the Knight motor represents only one of the many, many improvements in the gas engine, but it is what we call a fundamental improvement, as it is a development in the main idea of the gasoline motor, rather than merely an improvement of one of the parts. Most of the evolution of gas engines has consisted merely of the improvement and perfection of the various parts for more power, and more all around efficiency.

"You remember what you found out about gasoline motors in general when we were spending so much time talking about aeroplanes. The high speed motor, as we know it now, was invented, you know, by Gottlieb Daimler, a German inventor, in 1885, and with the ordinary four-cycle engine it takes four trips, or two round trips of the piston rod, to exert one push on the crankshaft of the engine. In other words, the explosion drives down the piston giving the power, and on its return trip the piston forces out the burned fumes. On the next downward stroke the fresh vapour is sucked into the cylinder and on the fourth trip, or second upward trip, the gas is compressed for the explosion. The carbureter on your motor-boat engine, and all others, as you know, is the device that mixes the gasoline with air and converts it into a highly explosive gas, and the sparking system is the electrical device that ignites the gas in the cylinders for each explosion which makes the 'pop, pop, pop' so familiar with all gasoline engines.

"In the old gas engines the ignition was derived from a few dry-cell batteries and some sort of a transformer coil, whereas nowadays the magneto takes care of this work. As you know there are many kinds of magnetos, and inventors have spent years working out better and better ones. Also, in the old style motors the carbureter was more or less of a makeshift, with a drip feed arrangement, and a hand regulating shutter for admitting the air. Now a special automatic device regulates this, so that it is no longer a toss up whether the gas is mixed in the proper quantities or not. Then, too, the oiling systems have been improved, so that the function is done automatically. In short, the motor has been made a perfectly reliable servant instead of a very capricious plaything.

"All these improvements made no fundamental change in the valves through which the gas was admitted to the cylinders, and the exhausted vapours expelled—and from your own experience you know that you are just about as apt to have trouble with your valves as with any other part of your machine.

"It is in these valves that the Knight motor departs from the usual style, and by this it eliminates the well-known 'pop, pop, pop' by which gas engines have been known all over the world."

As they looked over the engine, an expert in gasoline motors explained all the parts of the "Silent Knight" and showed the scientist and his boy friend just how the machine worked.

He said that the only big difference between the Knight motor and other standard makes of engines is that the Knight substitutes for the intake and exhaust valves an entirely new device composed of two cylinders, one within the other, sliding upon each other so as to regulate the flow of gas and the exhaust of fumes.

Early in his career as an inventor, while living in his home city of Chicago, Knight decided that gasoline engines had entirely too many parts—that they were too complicated—and he set about trying to simplify them. For one thing, he made a careful study of valves, and collected a specimen of every kind known to mechanics. The sliding locomotive valve seemed to him to hold the greatest possibilities for his work, and he began a series of experiments with sliding valves until he finally brought out his first engine in 1902.

Strange as it may seem, Knight's work was not recognized in his own country until after he had gone to Europe, where his engine was taken up by some of the biggest automobile manufacturers of England, France, Germany, Belgium, and Italy. After that it was taken up in the United States, and only now is coming to be generally known. The inventor now lives in England, where he was first successful, and he is still at work on improvements of his engine.

The motor expert went on to explain that the advantage of the Knight motor lay in the fact that the two sleeves or cylinders, which go to make up the combustion chamber or engine cylinder, sliding up and down upon one another, give a silent, vibrationless movement, as against the noisy action of the old style poppet or spring valve motors.

"But," interrupted the boy, "there are lots of other engines that run without making a noise nowadays."

"That is true," the man answered, "but most of them run quietly only when at low speed, or stationary. When they begin to hit the high places the noise of the poppet valves is very noticeable. A few years ago, when most engine builders were satisfied to make motors that would run, regardless of noise, they paid no attention to some of the finer mechanical problems, but since they have become more skilful, they are cutting down on the noise. But, as I say, the explosions are plainly heard when these engines are running at high speed. With the 'Silent Knight' the only noise is that of the fan and magneto, whether at low speed or the very fastest the motor can run. There can be no noise, for there is nothing for the sleeves to strike against."

The expert then went on to explain the motor in detail. The combustion chambers of the four or six-cylinder "Silent Knight," he explained, are made up of two concentric cylinders or sleeves, or, in other words, one cylinder within another. There is only the smallest fraction of an inch between them, and as they are well oiled by an automatic lubricating device they slide up and down upon each other with perfect ease. Of course the sleeves, which are made of Swedish iron, a very fine material for cylinder construction, are machined down inside and out so that they are perfectly smooth to run upon each other.

The two sleeves which go to make up one cylinder work up and down upon each other by means of a small connecting rod affixed to the bottom of each sleeve connected to an eccentric rod, which is driven by a noiseless chain from the engine shaft.

The most important features are the slots cut in each side, and close to the upper end of each sleeve, so that, as the sleeves move upon one another the slot in the right-hand side of the inner one will pass the slot of the right-hand side of the outer sleeve, and also the same with the left-hand side.

Then when the left-hand slots of the outer sleeve open upon, or come into register with the left-hand slots of the inner sleeve, a passage into the cylinder is opened for the new gas to enter. When a charge of gas has been drawn into the cylinder, one sleeve rises while the other falls, so that the openings are separated and the passage is tightly closed. The compression stroke then begins with the piston rising to the top. At this juncture the igniting spark explodes the compressed gas and the downward or power stroke takes place. During the upward compression stroke and the downward impulse stroke the slots have been closed, allowing no opportunity for the gas to escape. When the explosion has taken place and the piston has been driven to the bottom of its stroke, the right-hand openings in the inner sleeve and those of the outer sleeve come together, providing a passage for the exhausted gases to escape with the fourth or exhaust stroke. Thus it is plain that the motor is of the four-cycle type and it should not be confounded with two-cycle motors.

As the expert explained the motion he showed how it was carried out on an engine from which the casing had been partly removed. The careful mechanical adjustment of the eccentric shaft, which operated the connecting rods that pull the sleeves of the cylinder up and down so that the openings for the entrance of the fresh gas and the expulsion of the exploded fumes come together at just the proper second, was what took the boy's eye.

In connection with this the scientist handed the boy a magazine to read. It was a copy of the Motor Age in which an expert said editorially:

"Those who pin their faith to the slide-valve motor do so for many reasons, chief of which is that with this motor there is a definite opening and closing of the intake and exhaust parts, no matter at what motor speeds the car be operating. Two years ago one of the leading American engineers experimented with poppet valves and discovered that frequently at the high speeds the exhaust valves did not shut, there not being sufficient time owing to the inability of the valve spring to close the valve in the interval before a cam returned to open it again. With such a condition it is certain that the most powerful mixture was not obtained. With the sleeve valve such failure of operation cannot be, because no matter how fast the motor is operating there is a definite opening and closing for both intake and exhaust valve.

"It is a well-known fact that with poppet valves the tension of the springs on the exhaust side varies after five or six weeks' use, and consequently the accuracy of opening and closing is interfered with. Carbon gets on the valve seatings and prevents proper closing of the valve, with the result that the compression is interfered with and the face of the valve injured. These troubles are, as far as can be learned, obviated in the sleeve valve."

The friends of the Knight motor claim that it is simpler than the ordinary types of engines, having about one third less parts, that it is economic, powerful, and, as previously pointed out, runs silently. Beside these advantages, there are claimed for it many technical virtues that we need not enter into here.

The lubricating system of the Knight motors is another interesting point, as it serves to illustrate one more way in which the gasoline engine has been improved upon of late years. The manner of oiling used is known as the "movable dam" system. Located transversely beneath the six connecting rods are six oil troughs hinged on a shaft connected with the throttle. With the opening and closing of the throttle these troughs are automatically raised and lowered. When the throttle is opened, which raises the troughs, the points on the ends of the connecting rods dip deep into the oil and create a splashing of oil on the lower ends of the sliding sleeves. These sleeves are grooved circularly on their outer surfaces in order to distribute the oil evenly, while toward the lower ends holes are drilled to allow for the passage of oil.

When the motor is throttled down, which lowers the troughs, the points barely dip into the oil and a corresponding less amount of oil is splashed. An oil pump keeps the troughs constantly overflowing.

The motor is cooled by a complete system of water jackets, and it is fitted with a double ignition system, each independent of the other.

Of course in the adoption of the sliding sleeve type, mushroom valves, cams, cam rollers, cam shafts, valve springs, and train of front engine gears all are eliminated, the sliding parts fulfilling their various functions.

Before Mr. Knight ever achieved success with his motor it was subjected to some of the severest tests on record in the whole automobile industry. In France, Germany, and England, it was only accepted by the leading manufacturers after being tried out for periods extending over several months of the hardest kind of usage. Now, that it has proven itself a practical success, automobile men declare that the sliding valve principle, never before applied to gas engines until Knight began work, will undoubtedly have a lasting effect on the whole industry.

The compact little two-cycle motors represent another big fundamental development in the field of gas engines. There are many different makes of two-cycle motors, of course, and all have their various merits. They are used in practically all the work for which gas engines are employed, including automobiles, motor boats, and aeroplanes. It will not be necessary to describe these engines further than to say that the name describes the fundamental difference between them and the four-cycle motors. Instead of the piston making four strokes for every explosion—that is, an, upward stroke to clean out the burnt vapours, a downward stroke to suck in the fresh gas, an upward stroke to compress it, and finally the downward explosion or power stroke, all this work is done in two strokes.

For the general development of the gasoline engine, it is only necessary for a boy to look about him. Everywhere motors built on the same ideas as laid down in earlier inventions, but improved in every detail, are in use. Not only do we see them on fine pleasure automobiles, motor boats, and aeroplanes, but on our biggest trucks, fire engines, and in business establishments where light machinery is to be run.

CHAPTER XI
THE WIRELESS TELEGRAPH UP TO THE
MINUTE

THE SCIENTIST TALKS OF AMATEUR WIRELESS OPERATORS—THE GREAT DEVELOPMENT OF WIRELESS THAT HAS ENABLED IT TO SAVE ABOUT THREE THOUSAND LIVES—LONG DISTANCE WORK OF THE MODERN INSTRUMENTS

WHILE the inspiring stories of Jack Binns of the steamship Republic, and of J. G. Phillips and Harold S. Bride of the ill-fated Titanic are fresh in our minds, it is not necessary to say that within the last few years the wireless telegraph has established itself as indispensable to the safe navigation of the seas. The story of its development is a marvellous one when we think that it was only in December of 1901 that Marconi received the first signal ever transmitted across the Atlantic Ocean without wires. Now, as every boy knows, all the big steamships are equipped with wireless, all the governments of the world operate their own stations to communicate with their warships, at sea, and thousands upon thousands of boy amateurs operate their own little plants with complete success.

More wonderful still is the story when we think that by the use of this invention a total of about three thousand persons have been saved from death in shipwrecks. Nowhere in the pages of all history are there any more thrilling stories of heroism and devotion to duty than those of the men who, in the face of death themselves, have stuck by their keys sending out over the waves the "C. Q. D." and the "S. O. S." signals, which as every boy knows are the wireless calls for help.

The scientist and his boy friend never tired of talking of these things, for the young man was one of the many amateurs who had mastered the art, so that many a night as he sat at his receiver he caught the messages of steamships far out on the broad Atlantic, and heard the Navy Yard station transmitting orders to Uncle Sam's ships at sea.

One day shortly after the Titanic disaster the boy said to his friend: "I saw by the paper to-day that they are talking of passing a law to prevent the amateur wireless operators from working. I don't think they ought to do that. I'm sure most amateurs never interfere with any signals, as was said they did in connection with the messages to and from ships that went to the rescue of the Titanic."

"So long as the amateurs do not have powerful sending apparatus," answered the scientist, "I don't think they will make any serious trouble, for it makes no confusion to have them 'listening in' on the passing radiographs. Of course with a powerful sender a mischievous person could work irreparable damage by sending fake messages of one kind or another. In fact there have been several instances of messages that were thought to be fakes, but I am sure no boy with the intelligence to rig up a wireless outfit, would be so lacking in understanding of his responsibilities as to try to confuse traffic.

"But it would be a shame to stop the amateurs altogether," he continued, "for, no matter what the companies may say, the wireless telegraph is still in an experimental stage, and we must look to the bright boys who are studying it now, for its greatest development. The marvellous strides in improving the apparatus, and solving the mysteries of electro-magnetic currents, that have been made in the last dozen years, should be eclipsed in the next decade, if young men with some practical experience and a desire to get at the real scientific basis of the art, work at it."

"What are some of the main improvements of the last few years?" asked the boy.

For answer, the scientist and the boy made a journey down to the steamship docks, and visited the wireless cabins of several of the big transatlantic liners. They also went to the Brooklyn Navy Yard, where there is a wireless school, that turns out Navy operators after a thorough course in all the various branches of the art. While on vacations to the seashore, the youth had visited some of the big high-power stations that send and receive messages to and from the ships at sea.

In talking to the operators and electricians the boy learned much about the wide extent to which wireless is used nowadays. The law passed by Congress in the United States in 1911, making it necessary for every passenger steamer sailing from American ports with fifty or more passengers, to carry a wireless outfit capable of working at least 100 miles, in charge of a licensed operator, capable of transmitting 20 or more words a minute, did a great deal to increase the use of wireless. Also, not only the actions of one government but the concerted action of all the civilized nations represented at the various international wireless conferences have brought it to the official notice of the whole world.

Thus it has become a commercial reality on the sea, and the Great Lakes, and also it has become a big factor in war. All of the nations, besides having their warships equipped with wireless, now have wireless squads in the army, and have small compact apparatus that can be transported in small wagons, or even on horses' backs. These portable army wireless outfits are very valuable for the communication between detachments of an army, particularly in places where there are few disturbing elements to intercept the electro-magnetic waves.

In the recent campaign in Tripoli, in the war between Italy and Turkey, the wireless was extensively used by the Italian army in the field, and it was found that the messages radiated over the desert just about as well as over the sea. Of course as will be seen later, it is not meant here to convey the idea that wireless cannot be sent over the land, for the electro-magnetic waves travel through the ether in every direction, and as the ether fills the whole universe, mountains, buildings, or water just as well as the air, the waves are thought to go through obstacles as well as over water. The difficulty in sending over land, is that there are various electrical disturbances that intercept and confuse the wireless waves. In other words, wireless works through mere physical obstructions without any difficulty, just so long as certain little known electrical disturbances do not interfere. Just think of the thousands and thousands of wireless messages that are passing through the ether every hour of the day and night. And yet the scientists really know very little about the laws that govern them!

One of the instances of the strange antics of wireless was told to the boy by an operator who had been in charge of the wireless outfit on a Hudson River boat. He said that he and the operators on the other boats were able to communicate with a station on shore until they had passed the Poughkeepsie bridge, and the great steel and stone structure stretched between the boat and the station. Immediately communication stopped short and all efforts failed to get any response. A series of experiments proved that the obstruction was at the bridge, but whether it was some electrical property in the bridge itself, or in the hills on each side of the bridge, they have never been able to find out, and the land station was finally discontinued.

This is just an instance of what the scientists do not know about wireless, but it shows the many boy amateurs that there are still worlds for them to conquer in scientific research.

The central principle upon which the wireless telegraph works now is the same as it was when Marconi, through his marvellous invention, first received a signal from the other side of the Atlantic Ocean, but the inventors have learned much more about the details of the theory and it is in the improvement of devices for applying these laws of electricity that the development has been, rather than in the discovery of new theories. Nikola Tesla's invention for the wireless transmission of power by earth waves is a revolutionary departure from the usual wireless practice, but as we saw in the earlier chapter on this subject the Tesla invention has not yet been put in practical operation.

Though Guglielmo Marconi did not discover the laws of electricity upon which his invention is based, to him belongs all the credit for making use of the discoveries of the scientists of his day, and working out from them a practical system of wireless communication.

As many boys know, the wireless telegraph is possible through the radiation of electric waves. For instance, if a stone is thrown into a pool waves are started out in every direction from the point where the water is disturbed. The water does not move except up and down, and yet the waves pass on until they reach the side of the pool, or their force is expended.

The scientists before Marconi found out that when an electric spark was made to jump between two magnetic poles it started electric waves in every direction, much like the stone thrown into the pool, except at a speed that is reckoned at 186,000 miles per second.

Prof. Amos Dolbear, of Tufts College, Massachusetts, first made use of these waves in 1880, and a few years later Doctor Hertz, conducting experiments along the same lines, discovered them. Since that time these waves have been called Hertzian waves.

For many years scientists had understood that electrical waves or vibrations travelled through the ether in a copper wire, and that gave us telegraphy by wires, but it was a new thing to think of the waves travelling in every direction through space without wires. These early investigators found out that they could detect these waves by a device called a Hertzian loop, which was simply a copper wire bent into a hoop with the two ends close together but not touching. A spark would appear between the ends of the wire when the electric waves were sent out.

Marconi began his work where these scientists left off, as a very young man on his father's farm in Italy, but soon went to England, of which country his mother was a native, and placed the results of his experiments before the government authorities. Continuing his labors he soon had his wireless apparatus worked out in the form in which it first became known to the world.

It consisted of a transmitter, receiving machine or detector, and a set of antennæ or aerial wires from which the electrical waves were sent. For his transmitter, he created a spark between the two brass knobs on the ends of two thick brass wires by closing and opening an electrical circuit with a key, very much like, but somewhat larger than the regulation telegraph key. The space between the knobs was called the spark gap. For a dash he would hold down his key and make a large spark, and for a dot he would release his key quickly and make only a short one. Thus, he could send the regular Morse or Continental telegraphic codes of dots and dashes. These impulses were transmitted by wires to the aerial wires, or antennæ. The impulses left the antennæ as electro-magnetic waves, and went forth in all directions, only to be caught on the antennæ of another station aboard a ship or on land.

Here is where the receiver did its work, and the problem was a far more difficult one than the working out of the transmitter, for the waves as received were too weak in themselves to register a dot or a dash. In Marconi's first instruments he used a device called the "coherer." This was a glass tube about as big around as a lead pencil, and perhaps two inches long. It was plugged at each end with silver, and the narrow space between the plugs was filled with finely powdered fragments of nickel and silver, which possess the strange property of being alternately very good and very bad electrical conductors. The waves in Marconi's first experiments were received on a suspended kite wire, exactly similar to the wire used in the transmitter, but they were so weak that they could not of themselves operate an ordinary telegraph instrument. They possessed strength enough, however, to draw the little particles of silver and nickel in the coherer together in a continuous metal path. In other words, they made these particles "cohere," and the moment they cohered they became a good conductor for electricity, and a current from a battery near at hand rushed through the connection, operated the Morse instrument, and caused it to print a dot or a dash; then a little tapper, actuated by the same current, struck against the coherer, the particles of metal were broken apart, becoming a poor conductor, and cutting off the current from the home battery.

In Marconi's early experiments there was little or no attempt at tuning the instruments for waves of certain lengths, but this art has been developed to a high state in modern wireless telegraphy and we shall see how the operator tunes his instruments to talk to any one special station.

The distinguishing feature of the modern wireless transmitter, now familiar to every boy who has ever taken a trip aboard a large ship, or attended an electrical show, as it was in the old days, is the "crack, crack, cr-r-r-ack, crack" of the spark as it flickers between the brass knobs of the instrument, as the operator pounds away at his key. In some of the great high-power land stations, where long distance work is done the crash of the spark is like that of thunder, the flame is as big around as a man's wrist and of such intensity that it could not be looked at with unshaded eyes. On ships where the crash is too loud it has become necessary to cover the spark gap with a wooden muffler so as to deaden the noise.

While the simple spark gap of the early Marconi instruments was enough to send out the Hertzian waves, the modern transmitter is a marvel of electrical construction utilizing as it does the latest discoveries in electrical apparatus.

The most noticeable difference in the sending apparatus is in the arrangement of the two wires between which the spark flies. In the early instruments the wires were set in a horizontal line, and connected to an induction coil, but in the later ones the oscillator was turned up lengthwise with the spark gap between the vertical wings.

The different position of the spark gap is a change only in form, and not in principle. In the Marconi apparatus used nowadays the current comes from a dynamo of more than 110 volts, direct current. The two terminals of the circuit are connected with an induction coil, and from there to the two ends of the wires, making the terminals of the spark gap. The upper wire runs from the spark gap to the aerial, and the lower runs through a battery of Leyden jars, through a high tension transformer (as does the other side of the circuit), and thence to the ground. Aboard ship the ground connection is simply made by attaching a wire to the hull of the ship, which is in connection with the water, the best possible earth connection.

MARCONI TRANSMITTER LAYOUT

A—Key.  B—Induction coil.  C—Spark gap.  D—Dynamo.  E—Rheostat.  F—Interrupter magnet.  G—Aerial.  H—High tension transformer.  I —Ground wire.  K—Battery of Leyden jars.

There are, of course, a great many different kinds of transmitters, but they are all worked out on the same general principle—a spark gap which creates electrical oscillations that are sent into the ether from the aerials.

In some modern stations an alternating current is used at more than 100 volts and is stepped up through a transformer to about 30,000 volts. This high power current then charges a condenser consisting of a battery of Leyden jars.

When the operator presses his key he establishes a connection, which immediately sets up electrical waves oscillating at a rate of anywhere from 100,000 to 2,500,000 per second. These oscillations are carried to the antennæ where they pass into the ether and spread in all directions to be caught on the aerials of all stations within range.

One of the improvements in wireless transmission which makes long distance work possible aboard ships is the use of what the engineers call "coupled circuits." The arrangement consists in connecting the aerial to an induction coil, and connecting the latter with a ground wire. Another coil is placed close to this and is connected with the spark gap, and a condenser. The period of oscillation of the antennæ circuit, and of the spark gap circuit are timed to be exactly the same. The two circuits are then called "coupled circuits," for while they are coupled together by induction only, the oscillation or spark gap circuit increases its capacity, and at the same time has a small spark gap.

With these new devices for increasing the power of the oscillations, or in other words throwing a bigger stone into the pond, the electrical waves are sent out with far greater force, just as the water waves are sent farther in the pond, and will reach stations at a greater distance.

"Crash, bang," goes the oscillator, and in less time than it takes to think it the oscillations have reached the antennæ of ships hundreds or thousands of miles away, or even those of another land station on the other side of the Atlantic Ocean.

The next thing is to understand the apparatus used for receiving the faint electric waves transmitted through the ether, for the modern instruments are far different from the old style "coherer" explained before. As with the spark gaps, there are many different styles of receiving devices, all known by the general name of "detectors," as they detect the faint electro-magnetic waves radiating through the ether.

Some of the latest Marconi experiments show a return to the "coherer" idea, very greatly improved upon, but the full details of the device have not been made public.

Courtesy of the New York Edison Co.

THE NAVY WIRELESS SCHOOL

At top is the class in sending, while below is shown the class learning to receive messages.

AN AMATEUR WIRELESS OUTFIT

Hundreds of boys are receiving and sending wireless messages with far less efficient apparatus than that shown here.

MARCONI DETECTOR LAYOUT

A—Aerial.  B—Condenser.  C—Glass tube oscillator transformer.  D—D´—Rollers.  E—E´—Iron wire passing through oscillator transformer.  F—F´—Magnets.  G—G´—Ground wires.  H—Telephone receiver.

One of the detecting devices used by the Marconi system, after the old-style "coherer" was done away with, was very simple indeed in comparison to the cohering and tapping machines. It was made up of a small glass tube wound with copper wire. One end of this made the ground connection, and the other end led to the aerial, and also to an earth connection through a tuning inductance coil. Then another coil was wound around the first one on the glass tube and connected with the head telephone receivers which have taken the place of the Morse dot and dash printing instrument in all the modern wireless instruments. Two magnets were placed just above the glass tube, and a flexible iron wire was made to move through it by means of a pair of rollers a little way from each end. When the electro-magnetic waves reached the aerial and made oscillations in the first coil about the glass tube, the magnetic intensity of the iron wire band was disturbed and the glass tube became an oscillation transformer, setting up currents in the coil leading to the telephone receivers. The impulses were manifested by ticks, just the length of the dots and dashes being sent out by the operator perhaps thousands of miles away.

Another form of detector is the "electrolytic" which consists of a very fine platinum wire about one ten-thousandth of an inch in diameter, which dips into a platinum cup filled with nitric acid. When the invisible electro-magnetic waves impinge upon the wires of the receiving station, and cause electrical surges to take place in those wires, they in turn affect the detector, giving an exact reproduction of the note of the transmitting spark at the distant station.

This device has since been replaced by one of another type, equally sensitive and much better suited for general work on account of its greater stability and freedom from atmospheric disturbances. This detector consists simply of a crystal of carborundum supported between two brass points. When connected to the antennæ it is affected by the oscillations caused by distant transmitting stations as previously stated. These wireless signals are reproduced in telephone receivers.

Another frequently used detector known as the Audion is composed of a small incandescent lamp with filaments of carbon, tantalum, or preferably tungsten, and one or more sheets or wings of platinum secured near the filaments. The lamp is lighted by a set of home batteries, and is connected with a ground wire, the aerial, and the telephone receivers. The tungsten filament and the platinum wing act as two electrodes, and the faint electric oscillations received on the antennæ and transmitted to the platinum plate are supposed to affect the discharge of negatively electrified particles, or ions, between the two electrodes. This affects the flow of the battery current, and consequently registers the oscillations in the telephone receivers.

By diligent study of the subject the wireless experts also have learned that the arrangement of the aerials is of great importance, because much depends upon the send-off received by the electrical oscillations. In Marconi's early experiments he used a single wire attached to a kite, then changed to a single wire stretched from the top of a high mast. Later, the system of stretching the wires horizontally between two masts, as we see them so often aboard passenger steamships, and at land stations, came into general use. The old idea that the height of the aerial wires had something to do with the efficiency of the apparatus has passed, for science showed that the electro-magnetic waves travelled in all directions irrespective of land, water, mountains, or buildings. Whether, in sending messages across the ocean, they actually pass through the globe, or follow the curve of the surface, is more than the most careful wireless students have been able to tell.

Another of the big improvements in wireless is in the tuning of the instruments to certain wave lengths or rates of vibrations, and in controlling the wave lengths by the sender. Science has established that these waves usually vary from a few feet up to 12,000 feet or more. The ordinary wave lengths for ships is between 1,000 feet and 1,800 feet, but on the biggest land stations and the transatlantic liners the full 12,000 feet is used. Even greater lengths of waves are used by the big Marconi stations transmitting messages between Clifden, on the west coast of Ireland, and Glace Bay, Nova Scotia. The reason for this is that with the same power messages can be sent greater distances with long wave lengths than with shorter ones.

The wave length is controlled by an apparatus called the "helix," which may be seen in the picture of the wireless outfit. It looks like a drum wound with a spiral of copper tubing, and although it looks simple it presents some of the greatest problems in connection with wireless.

On the receiving end is the instrument called the tuner, by which the operator can adjust his detector to the wave lengths being sent out by the station with which he wishes to talk. There are various kinds of "tuners," all more or less complicated. The device corresponds to the telephone exchange or the telegraph switch-board. Of course a good receiving apparatus can be tuned so that the operator can listen to any messages going through the ether, within range, but all messages that are intended to be secret are sent in code, just as all wire and cable messages that are secret are sent in code.

In line with the advent of wireless telegraphy it is fitting that we should have the wireless telephone. While this instrument is still in the experimental stage, some very promising results have been obtained. There are several experimental wireless telephone stations in New York City, but the best results are obtained when some one keeps up a steady conversation, so it is far easier to connect the reproducer of a phonograph to the transmitter of the wireless telephone. It is surprising how distinctly this music or speech is received. In fact the ship operators nearing New York are often entertained by strains of music from these wireless telephones. The wireless telephones employ what are known as undamped oscillations created by electric arcs, and it is very easy to "tune out" such vibrations for musical effects.

Just as we have the motion-picture "newspaper," we have the wireless newspaper published aboard the big transatlantic liners every day. The news is sent out from certain land stations at certain times in the day and night, and every ship within range copies it, and publishes it just as our regular daily papers are published. Of course, the paper is small, but it usually contains most of the important news of the day, the big sporting items, such as baseball scores, and the stock quotations.

In the United States the great station at Wellfleet, Cape Cod, Mass., sends out the press matter each night from dispatches prepared in the main offices of the big American press associations. Ships as far as 1,600 miles distant frequently receive this news matter, and by the time the ocean-going editor is ready to get out his next day's edition he is in touch with the wireless press station on the other side, and is receiving the world's news from the English coast.

As our young friend found out when he was gathering up all the information he could about aeroplanes, some success has been made in the equipment of the fliers with wireless. The project offers some serious difficulties, however, as on an aeroplane there is no place for long aerials. Experiments have been tried with long trailing wires, but these are dangerous to the aeroplane, and to use the wires of the machine for antennæ endangers the operator to electric shocks. One scheme tried by several aviators in the United States with some success has been the stringing of aerials in the rear framework.

The problem of equipping balloons and airships with wireless is much simpler because it allows of long trailing wires to act as the antennæ. Most boys will remember the success of the wireless apparatus that was set up on the America at the time Walter Wellman made his famous attempt to cross the Atlantic in his airship.

That wireless will take its place as one of the great forces in civilization is the idea of Guglielmo Marconi, the inventor of the wireless telegraph, expressed when he was in New York in the spring of 1912.

"I believe," he said, "that in the near future a wireless message will be sent from New York completely round the globe with no relaying, and will be received by an instrument located in the same office as the transmitter, in perhaps even less time than Shakespeare's forty minutes.

"Most messages across the Atlantic will probably go by wireless at a comparatively early date. In time of war wireless connections will be invaluable. The enemy can cut cables and telegraph wires; but it is difficult seriously to damage the wireless service. The British Empire has realized this, and is already equipping many of its outposts with wireless stations."

CHAPTER XII
MORE MARVELS OF SCIENCE

COLOUR PHOTOGRAPHY, THE TUNGSTEN ELECTRIC LAMP, THE PULMOTOR, AND OTHER NEW INVENTIONS INVESTIGATED BY OUR BOY FRIEND

BEFORE we leave our good friend the scientist and his young companion, let us go over a few more of the things about which they talked. To take up all of them would be to prolong this book indefinitely, for the boy's mind was ever unfolding to the new things of the world and with each subject mastered, or at least partially understood, he was anxious to go on to the next. Not that he did not have his special hobbies upon which he spent most of his time, for he did, but that did not prevent his inquiring young mind from reaching out for new and more wonderful things once he had come to realize the world of marvels in which we live.

One of this youth's favourite pastimes was photography, and as an amateur his work had attracted considerable attention from his friends. One day in the summer, when all the trees, shrubs, and flowers were at the height of their beauty, he came into the laboratory where his scientific friend was working over an experiment.

"I have heard of a process of colour photography," he said, "and I wonder if I couldn't make use of it to get some good pictures out in the country, showing just exactly how it is."

"Certainly," replied his friend. "There are a number of systems of colour photography now—all invented within the last few years. None of them is perfect though, and you would have the added fun of carrying on some experiments that might bring to light some valuable knowledge.

"While it is possible to make coloured photographic prints now, by means of a specially treated paper, colour photography is best known as a means of making beautiful transparent glass plates and lantern slides. When held up to the light, the transparencies give an accurate picture of the scene in natural colours. The paper I mention can be bought at the photographic houses, but the inventors do not claim yet that their process is so perfect as to give exact reproductions of all the shades of colours unless they are well defined in the positive plates. The prints are made from the positive transparencies in just the same way that photographic prints are made from black and white photographic plates."

"Let's try some colour photographs," promptly said the boy. "Will you go out into the country with me some Saturday and help me?"

"I certainly will be glad to go with you, but you are a better photographer than I am, for you see, about the only kind of photography I do now is with a microscope, such as you have looked through here many times. Your own regular camera and tripod will be all you will need, for I will buy the colour plates upon which the pictures are to be taken."

They made their trip to the country on the first pleasant Saturday, and while they were out the scientist explained many points about the system.

"Years ago," he said, "even before that wonderful Frenchman, Daguerre, invented light photography, scientists were trying to discover some means of mechanically registering on paper, the beautiful things they saw in nature, in their natural colours, as well as in their natural form in black and white. All through the years of the development of photography with light and shadow, scientists never relaxed their search for some way of photographing colours. Although many of them hit upon the colour screen idea by which it finally was accomplished, there remained years and years of patient experiment. Prof. James Clark Maxwell, Ducos du Hauron, Doctor Konig, Sanger Shepherd, and, in later years, Frederick Eugene Ives, of Philadelphia, all worked on the idea.

"In 1907, however, Antoine Lumiére, of the famous French photographic house that bears his name, announced a system of colour photography which has grown in popularity ever since. The system, which is known as the autochrome, was the result of many years patient study and research with his sons who are associated in business with him."

The scientist then went on to explain that in attacking the problem the investigators first had to learn all they could about colours, and how they are reflected by light rays. As we have seen in the colour process for motion pictures there are really only three fundamental or primary colours, and all other shades and tints are made up from combinations of these. The three are blue-violet, green, and orange-red, and a screen of these forms the foundation of all the colour plates now used.

In the autochrome process the lowly potato, which we generally think of merely as a common article of our food, forms the first factor. The starch of the potato is ground down and sifted so that the grains are the same size—not more than 0.0004 to 0.0005 of an inch in diameter. These grains then are divided into three equal portions, and each portion is dyed, respectively, blue-violet, green, and orange-red. The three little piles of starch grains are then mixed together in suitable amounts and dusted on to a plate, which has previously been coated with a substance to make them stick. The difficulty in dusting on the starch grains is great, for they must cover the whole plate equally and yet not make any piles of starch at any one point, for to have several grains on top of one another would spoil the effect. The extreme delicacy of this operation will be appreciated when it is realized that there are over five million grains to the square inch. When the starch is all properly placed it makes the colour screen, though in appearance the plate is a dark gray.

The plate is next put through a rolling process so that all the grains are flattened out to form a mosaic covering over the whole surface. In spite of all the manufacturers can do there will still be some microscopic spaces between the particles, and these are filled up with a fine powder of carbon to prevent the passage of light.

The screen is then coated with a very thin layer of varnish and upon this is laid a thin and extremely sensitive photographic emulsion.

"And so that is the way these autochrome plates we have here were made," concluded the scientist. "Now our troubles begin, for we must be careful to give them a fair trial with the proper kind of an exposure and the proper kind of development."

As the plates are extremely sensitive to all kinds of light the scientist cautioned the boy against loading the camera carelessly. It is better, he said, to load in a dark room.

In putting the plates in the camera the plates are reversed and instead of placing the sensitized side toward the lens, the uncoated glass is put in front and the photograph is taken through the glass. Thus, the image first passes through the glass, next, through the grains of coloured starch, and, lastly, is recorded on the sensitive photographic emulsion.

Before loading the camera, however, the scientist fitted a yellow colour screen over the lens, explaining that this was necessary to absorb some of the overactive blue-violet light rays, to which the emulsion is extremely sensitive.

In exposing the plate what happens is this: Suppose a green field is to be photographed. The green rays of light, reflected from the field, pass through the lens, and through the glass support of the plate. But when they reach the coloured starch, the green rays pass through the green particles of starch, but not through the violet-blue particles, or the orange-red particles, for the grains of other colours absorb the green rays and hold them. Thus, development would show that the green light rays passing through the green starch particles caused the emulsion to darken under the green particles in just the proportion in which the green light reached them, and to record the image they carried. As the light would not pass through the other coloured particles they would not record any image. Thus a negative is produced, as we have seen, not the colour we see in life but the complement. By treating the plate with a solvent of silver the tiny black specks that were brought out behind each green particle are removed and each starch grain is allowed to transmit exactly the colour we see in life. In other words, we have a positive.

This is just as true of all the shades and hues as it is of the three fundamental colours, for the various rays of light will penetrate the starch in just the proportion of the hues they represent in the scene before our eyes. While the silver solvent will remove the dark images built up by the penetration of green light, it will leave behind the particles of red-orange, and blue-violet, backed up by the creamy silver bromide of the emulsion. If above the green field we had a blue sky, the blue-violet particles would let the blue-violet rays penetrate them, and record the image of the sky.

After the negative has been treated and made a positive, a second development reduces the silver bromide to opaque metallic silver, preventing any light from passing through the grains through which a part of the image did not pass. This second bath also brightens the colours, while the hypo bath removes the unaltered silver bromide ensuring permanency to the image.

"Of course in taking these colour photographs," went on the scientist, "we must take into consideration a great many things, to which the manufacturers will call your attention in their booklets. The exposure is the most important part of all, for these plates are necessarily slow and must be exposed for a much longer time than the ordinary rapid plates. For instance, this field, with this bright summer sunlight, will require a full second with this lens at U. S. 4."

The scientist then went on to give the boy directions for developing his colour plates, as follows:

The whole process of development consists of three operations and but two solutions are required, one of them being kept preferably in two stock solutions. Apothecary weight is used.

STOCK DEVELOPER

Water	30 ounces
Metoquinone	3-1/2 drams
Sodium sulphite (dry)	3 ounces
Ammonia (density 0.923 or 22 degrees B)	1 ounce
Potassium bromide	1-1/2 drams

Dissolve the metoquinone first in lukewarm water and then the other chemicals in the order given.

STOCK REVERSING SOLUTIONS

A. Water	25 ounces
Potassium permanganate	50 grains
B. Water	25 ounces
Sulphuric acid	4 drams

Errors in exposure are to be corrected by varying the duration of development and the amount of stock solution added after the appearance of the image. Use the solutions at a temperature of 60 degrees Fahrenheit, and start development of a 5 × 7 plate in

Water	4 ounces
Metoquinone stock solution	2 drams

Have ready two graduates, one containing 6 drams of the stock developer, the other 2-1/4 ounces. Begin counting seconds upon immersion of the plate in the weak developer and watch for the outlines of the image, not considering the sky. If the time of appearance is less than 40 seconds, add the smaller quantity of stock solution; if more, add the greater. The total times of development are given in the following table. Cover the tray for protection from light as soon as the solution has been modified properly.

TIME, IN SECONDS, OF APPEARANCE OF IMAGE, DISREGARDING THE SKY.	QUANTITY OF METOQUINONE STOCK SOLUTION TO BE ADDED AFTER IMAGE APPEARS.	TOTAL DURATION OF DEVELOPMENT, INCLUDING TIME OF APPEARANCE.
		Minutes.	Seconds.
12 to 14	6 drams	1	15
15 " 17	"	1	45
18 " 21	"	2	15
22 " 27	"	3	15
28 " 33	"	3	30
34 " 39	"	4	30
———	————	—	——
40 to 47	2-1/2 ounces	3
Over 47	""	4

As soon as development is finished rinse the plate briefly, immerse in equal parts of the reversing solutions and carry the tray into bright daylight. Gradually the image clears and the true colours are seen by transmitted light. In three or four minutes the action will be complete. Rinse the plate in running water for thirty or forty seconds and immerse again, still in daylight, in the developer. In three or four minutes the white parts of the image will be seen to have turned entirely black. The plate may now be rinsed for three or four minutes in running water and set away to dry without fixing.

To avoid frilling in summer, it is well to immerse the plate for two minutes after reversal in

Water	5 ounces
Chrome alum	25 grains

After a brief rinsing proceed with the second development as usual.

The completed transparency may be protected from scratches to a certain extent by varnishing the film side, although this is not necessary. The varnish consists of

Benzole (crystallizable)	5 ounces
Gum dammar	1 ounce

It should be applied cold in the usual way, making sure that the entire surface is covered, and then setting the plate on edge to dry.

The other colour processes now used with success also are based upon the colour screen.

The process known as the omnicolore, which was brought out in France, depends upon a screen consisting of a very fine network of violet lines in one direction, crossed by red and green lines at right angles. The usual sensitive emulsion is placed over these. The lines run more than two hundred to the inch but they can be seen by close examination of the plate.

In the Thames process which was brought out in England the colour screen and the sensitive emulsion are on separate plates which must be bound together during exposure and again placed in register or in exactly the same relative position after development. This causes some trouble, but reduces expense as the failures waste the sensitive plates but not the colour screens. The primary colours instead of being scattered at random, as in the autochrome system, are arranged in a pattern to give the proper proportions to each. The red-orange and green particles are arranged in circles, with the green a little larger than the red ones, while the blue particles fill the spaces.