That the crews of the war-ships will have to undergo the strain of submarine attack in the next naval war is almost sure. All the great nations of the world have built fleets of submarines or are preparing to do so.

In the development of under-water fighting-craft France leads, as she has the largest fleet and was the first to encourage the designing and building of them. But it was David Bushnell that invented and built the first practical working submarine boat, and in point of efficiency and practical working under service conditions in actual readiness for hostile action the American boats excel to-day.

A PEACEFUL SUBMARINE

Under the green sea, in the total darkness of the great depths and the yellowish-green of the shallows of the oceans, with the seaweeds waving their fronds about their barnacle-encrusted timbers and the creatures of the deep playing in and about the decks and rotted rigging, lie hundreds of wrecks. Many a splendid ship with a valuable cargo has gone down off a dangerous coast; many a h.o.a.rd of gold or silver, gathered with infinite pains from the far corners of the earth, lies intact in decaying strong boxes on the bottom of the sea.

To recover the treasures of the deep, expeditions have been organised, ships have sailed, divers have descended, and crews have braved great dangers. Many great wrecking companies have been formed which accomplish wonders in the saving of wrecked vessels and cargoes. But in certain places all the time and at others part of the time, wreckers have had to leave valuable wrecks a prey to the merciless sea because the ocean is too angry and the waves too high to permit of the safe handling of the air-hose and life-line of the divers who are depended upon to do all the under-water work, rigging of hoisting-tackle, placing of buoys, etc.

Indeed, it is often impossible for a vessel to stay in one place long enough to accomplish anything, or, in fact, to venture to the spot at all.

It was an American boy who, after reading Jules Verne's "Twenty Thousand Leagues Under the Sea," said to himself, "Why not?" and from that time set out to put into practice what the French writer had imagined.

Simon Lake set to work to invent a way by which a wrecked vessel or a precious cargo could be got at from below the surface. Though the waves may be tossing their whitecaps high in air and the strong wind may turn the watery plain into rolling hills of angry seas, the water twenty or thirty feet below hardly feels any surface motion. So he set to work to build a vessel that should be able to sail on the surface or travel on the bottom, and provide a shelter from which divers could go at will, undisturbed by the most tempestuous sea. People laughed at his idea, and so he found great difficulty in getting enough capital to carry out his plan, and his first boat, built largely with his own hands, had little in its appearance to inspire confidence in his scheme. Built of wood, fourteen feet long and five feet deep, fitted with three wheels, _Argonaut Junior_ looked not unlike a large go-cart such as boys make out of a soap-box and a set of wooden wheels. The boat, however, made actual trips, navigated by its inventor, proving that his plan was feasible. _Argonaut Junior,_ having served its purpose, was abandoned, and now lies neglected on one of the beaches of New York Bay.

The _Argonaut,_ Mr. Lake's second vessel, had the regular submarine look, except that she was equipped with two great, rough tread-wheels forward, and to the underside of her rudder was pivoted another. She was really an under-water tricycle, a diving-bell, a wrecking-craft, and a surface gasoline-boat all rolled into one. When floating on the surface she looked not unlike an ordinary sailing craft; two long spars, each about thirty feet above the deck, forming the letter A--these were the pipes that admitted fresh air and discharged the burnt gases of the gasoline motor and the vitiated air that had been breathed. A low deck gave a ship-shape appearance when floating, but below she was shaped like a very fat cigar. Under the deck and outside of the hull proper were placed her gasoline tanks, safe from any possible danger of ignition from the interior. From her nose protruded a spar that looked like a bowsprit but which was in reality a derrick; below the derrick-boom were several glazed openings that resembled eyes and a mouth: these were the lookout windows for the under-water observer and the submarine searchlight.

The _Argonaut_ was built to run on the surface or on the bottom; she was not designed to navigate half-way between. When in search of a wreck or made ready for a cruise along the bottom, the trap door or hatch in her turret-like pilot house was tightly closed; the water was let into her ballast tanks, and two heavy weights to which were attached strong cables that could be wound or unwound from the inside were lowered from their recesses in the fore and after part of the keel of the boat to the bottom; then the motor was started connected to the winding mechanism, and, the buoyancy of the boat being greatly reduced, she was drawn to the bottom by the winding of the anchor cables. As she sank, more and more water was taken into her tanks until she weighed slightly more than the water she displaced. When her wheels rested on the bottom her anchor-weights were pulled completely into their wells, so that they would not interfere with her movements.

Then the strange submarine vehicle began her voyage on the bottom of the bay or ocean. Since the pipes projected above the surface plenty of fresh air was admitted, and it was quite as easy to run the gasoline engine under water as on the surface. In the turrets, as far removed as possible from the magnetic influences of the steel hull, the compa.s.s was placed, and an ingeniously arranged mirror reflected its readings down below where the steersman could see it conveniently. Aft of the steering-wheel was the gasoline motor, connected with the propeller-shaft and also with the driving-wheels; it was so arranged that either could be thrown out of gear or both operated at once. She was equipped with depth-gauges showing the distance below the surface, and another device showing the trim of the vessel; compressed-air tanks, propelling and pumping machinery, an air-compressor and dynamo which supplied the current to light the ship and also for the searchlight which illuminated the under-water pathway--all this apparatus left but little room in the hold, but it was all so carefully planned that not an inch was wasted, and s.p.a.ce was still left for her crew of three or four to work, eat, and even sleep, below the waves.

Forward of the main s.p.a.ce of the boat were the diving and lookout compartments, which really were the most important parts of the boat, as far as her wrecking ability was concerned. By means of a trap door in the diving compartment through the bottom of the boat a man fitted with a diving-suit could go out and explore a wreck or examine the bottom almost as easily as a man goes out of his front door to call for an "extra." It will be thought at once, "But the water will rush in when the trap door is opened." This is prevented by filling the diving compartment, which is separated from the main part of the ship by steel walls, with compressed air of sufficient pressure to keep the water from coming in--that is, the pressure of water from without equals the pressure of air from within and neither element can pa.s.s into the other's domain.

An air-lock separates the diver's section from the main hold so that it is possible to pa.s.s from one to the other while the entrance to the sea is still open. A person entering the lock from the large room first closes the door between and then gradually admits the compressed air until the pressure is the same as in the diving compartment, when the door into it may be safely opened. When returning, this operation is simply reversed. The lookout stands forward of the diver's s.p.a.ce. When the _Argonaut_ rolls along the bottom, round openings protected with heavy gla.s.s permit the lookout to follow the beam of light thrown by the searchlight and see dimly any sizable obstruction. When the diving compartment is in use the man on lookout duty uses a portable telephone to tell his shipmates in the main room what is happening out in the wet, and by the same means the reports of the diver can be communicated without opening the air-lock.

This little ship (thirty-six feet long) has done wonderful things. She has cruised over the bottom of Chesapeake Bay, New York Bay, Hampton Roads, and the Atlantic Ocean, her driving-wheels propelling her when the bottom was hard, and her screw when the oozy condition of the submarine road made her spiked wheels useless except to steer with. Her pa.s.sengers have been able to examine the bottom under twenty feet of water (without wetting their feet), through the trap door, with the aid of an electric light let down into the clear depths. Telephone messages have been sent from the bottom of Baltimore Harbour to the top of the New York _World_ building, telling of the conditions there in contrast to the New York editor's aerial perch. Cables have been picked up and examined without dredging--a hook lowered through the trap door being all that was necessary. Wrecks have been examined and valuables recovered.

[Ill.u.s.tration: SINGING INTO THE TELEPHONE Part of the entertainment furnished by the telephone newspaper at Buda-Pest.]

Although the _Argonaut_ travelled over 2,000 miles under water and on the surface, propelled by her own power, her inventor was not satisfied with her. He cut her in two, therefore, and added a section to her, making her sixty-six feet long; this allowed more comfortable quarters for her crew, s.p.a.ce for larger engines, compressors, etc.

It was off Bridgeport, Connecticut, that the new _Argonaut_ did her first practical wrecking. A barge loaded with coal had sunk in a gale and could not be located with the ordinary means. The _Argonaut_, however, with the aid of a device called the "wreck-detector," also invented by Mr. Lake, speedily found it, sank near it, and also submerged a new kind of freight-boat built for the purpose by the inventor. A diver quickly explored the hulk, opened the hatches of the freight-boat, which was cigar-shaped like the _Argonaut_ and supplied with wheels so it could be drawn over the bottom, and placed the suction-tube in position. Seven minutes later eight tons of coal had been transferred from the wreck to the submarine freight-boat. The hatches were then closed and compressed air admitted, forcing out the water, and five minutes later the freight-boat was floating on the surface with eight tons of coal from a wreck which could not even be located by the ordinary means.

It is possible that in the future these modern "argonauts" will be seeking the golden fleeces of the sea in wrecks, in golden sands like the beaches of Nome, and that these amphibious boats will be ready along all the dangerous coasts to rush to the rescue of n.o.ble ships and wrest them from the clutches of the cruel sea.

Mr. Lake has also designed and built a submarine torpedo-boat that will travel on the surface, under the waves, or on the bottom; provided with both gasoline and electric power, and, fitted with torpedo discharge tubes, she will be able to throw a submarine torpedo; her diver could attach a charge of dynamite to the keel of an anch.o.r.ed warship, or she could do great damage by hooking up cables through her diver's trap door and cutting them, and by setting adrift anch.o.r.ed torpedoes and submarine mines.

Thus have Jules Verne's imaginings come true, and the dream _Nautilus,_ whose adventures so many of us have breathlessly followed, has been succeeded by actual "Hollands" and practical "Argonauts" designed by American inventors and manned by American crews.

LONG-DISTANCE TELEPHONY

What Happens When You Talk into a Telephone Receiver

In Omaha, Nebraska, half-way across the continent and about forty hours from Boston by fast train, a man sits comfortably in his office chair and, with no more exertion than is required to lift a portable receiver off his desk, talks every day to his representative in the chief New England city. The man in Boston hears his chief's voice and can recognise the peculiarities in it just as if he stood in the same room with him. The man in Nebraska, speaking in an ordinary conversational tone, can be heard perfectly well in Boston, 1,400 miles away.

This is the longest talk on record--that is, it is the longest continuous telephone line in steady and constant use, though the human voice has been carried even greater distances with the aid of this wonderful instrument.

The telephone is so common that no one stops to consider the wonder of it, and not one person in a hundred can tell how it works.

At this time, when the telephone is as necessary as pen and ink, it is hard to realise a time when men could not speak to one another from a distance, yet a little more than a quarter of a century ago the genius who invented it first conceived the great idea.

Sometimes an inventor is a prophet: he sees in advance how his idea, perfected and in universal use, will change things, establish new manners and customs, new laws and new methods. Alexander Graham Bell was one of these prophetic inventors--the telephone was his invention, not his discovery. He first got the idea and then sought a way to make it practical. If you put yourself in his place, forget what has been accomplished, and put out of mind how the voice is transmitted from place to place by the slender wire, it would be impossible even then to realise how much in the dark Professor Bell was in 1874.

The human speaking voice is full of changes; unlike the notes from a musical instrument, there is no uniformity in it; the rise and fall of inflection, the varying sound of the vowels and consonants, the combinations of words and syllables--each produces a different vibration and different tone. To devise an instrument that would receive all these varying tones and inflections and change them into some other form of energy so that they could be pa.s.sed over a wire, and then change them back to their original form, reproducing each sound and every peculiarity of the voice of the speaker in the ear of the hearer, was the task that Professor Bell set for himself. Just as you would sit down to add up a big column of figures, knowing that sooner or later you would get the correct answer, so he set himself to work out this problem in invention. The result of his study and determination is the telephones we use to-day. Many improvements have been invented by other men--Berliner, Edison, Blake, and others--but the idea and the working out of the principle is due to Professor Bell.

[Ill.u.s.tration: "CENTRAL" TELEPHONE OPERATORS AT WORK Since tiny lights have taken the place of bells to indicate the calls of subscribers the central stations are quiet except for the low hum of carefully modulated voices. The women standing behind the seated operators are inspectors. They watch for mistakes and disturbances of any kind.]

Every telephone receiver and transmitter has a mouth-and ear-piece to receive or throw out the sound, a thin round sheet of lacquered metal--called a diaphragm, and an electromagnet; together they reproduce human speech. An electric current from a battery or from the central station flows continuously through the wires wound round the electromagnet in receiving and transmitting instruments, so when you speak into the black mouthpiece of the wall or desk receiver the vibrations strike against the thin sheet-iron diaphragm at the small end of the mouthpiece; the sound waves of the voice make it vibrate to a greater or less degree; the diaphragm is placed so that the core of the electromagnet is close to it, and as it vibrates the iron in it produces undulations (by induction) in the current which is flowing through the wires wound round the soft iron centre of the magnet. The wires of the coil are connected with the lines that go to the receiving telephone, so that this undulating current, coiling round the core of the magnet in the receiver, attracts and repels the iron of the diaphragm in it, and it vibrates just as the transmitter diaphragm did when spoken into; the undulating current is translated by it into words and sentences that have all the peculiarities of the original. And so when speaking into a telephone your voice is converted into undulations or waves in an electric current conveyed with incredible swiftness to the receiving instrument, and these are translated back into the vibrations that produce speech. This is really what takes place when you talk over a toy telephone made by a string stretched between the two tin mouth-pieces held at opposite sides of the room, with the difference that in the telephone the vibrations are carried electrically, while the toy carries them mechanically and not nearly so perfectly.

For once the world realised immediately the importance of a revolutionising invention, and telephone stations soon began to be established in the large cities. Quicker than the telegraph, for there was no need of an operator to translate the message, and more accurate, for if spoken clearly the words could be as clearly understood, the telephone service spread rapidly. Lines stretched farther and farther out from the central stations in the cities as improvements were invented, until the outlying wires of one town reached the outstretched lines of another, and then communication between town and town was established. Then two distant cities talked to each other through an intermediate town, and long-distance telephony was established. To-day special lines are built to carry long-distance messages from one great city to another, and these direct lines are used entirely except when storms break through or the rush of business makes the roundabout route through intermediate cities necessary.

As the nerves reaching from your finger-tips, from your ears, your eyes, and every portion of your body come to a focus in your brain and carry information to it about the things you taste, see, hear, feel, and smell, so the wires of a telephone system come together at the central station. And as it is necessary for your right hand to communicate with your left through your brain, so it is necessary for one telephone subscriber to connect through the central station with another subscriber.

The telephone has become a necessity of modern life, so that if through some means all the systems were destroyed business would be, for a time at least, paralysed. It is the perfection of the devices for connecting one subscriber with another, and for despatching the vast number of messages and calls at "central," that make modern telephony possible.

To handle the great number of spoken messages that are sent over the telephone wires of a great city it is necessary to divide the territory into districts, which vary in size according to the number of subscribers in them. Where the telephones are thickly installed the districts are smaller than in sections that are more spa.r.s.ely settled.

Then all the telephone wires of a certain district converge at a central station, and each pair of wires is connected with its own particular switch at the switchboard of the station. That is simple enough; but when you come to consider that every subscriber must be so connected that he can be put into communication with every other subscriber, not only in his own section but also with every subscriber throughout the city, it will be seen that the switchboard at central is as marvellous as it is complicated. Some of the busy stations in New York have to take care of 6,000 or more subscribers and 10,000 telephone instruments, while the city proper is criss-crossed with more than 60,000 lines bearing messages from more than 100,000 "'phones." Just think of the babel entering the branch centrals that has to be straightened out and each separate series of voice undulations sent on its proper way, to be translated into speech again and poured into the proper ear. It is no wonder, then, that it has been found necessary to establish a school for telephone girls where they can be taught how to untangle the snarl and handle the vast, complicated system. In these schools the operators go through a regular course lasting a month. They listen to lectures and work out the instructions given them at a practice switchboard that is exactly like the service switchboard, except that the wires do not go outside of the building, but connect with the instructor's desk; the instructor calls up the pupils and sends messages in just the same way that the subscribers call "central" in the regular service.

At the terminal station of a great railroad, in the midst of a network of shining rails, stands the switchman's tower. By means of steel levers the man in his tower can throw his different switches and open one track to a train and close another; by means of various signals the switchman can tell if any given line is clear or if his levers do their work properly.

A telephone system may be likened, in a measure, to a complicated railroad line: the trunk wires to subscribers are like the tracks of the railroad, and the central station may be compared to the switch tower, while the central operators are like the switchmen. It is the central girls' business to see that connections are made quickly and correctly, that no lines are tied up unnecessarily, that messages are properly charged to the right persons, that in case of a break in a line the messages are switched round the trouble, and above all that there shall be no delay.

When you take your receiver off the hook a tiny electric bulb glows opposite the bra.s.s-lined hole that is marked with your number on the switchboard of your central, and the telephone girl knows that you are ready to send in a call--the flash of the little light is a signal to her that you want to be connected with some other subscriber. Whereupon, she inserts in your connection a bra.s.s plug to which a flexible wire is attached, and then opens a little lever which connects her with your circuit. Then she speaks into a kind of inverted horn which projects from a transmitter that hangs round her neck and asks: "Number, please?"

You answer with the number, which she hears through the receiver strapped to her head and ear. After repeating the number the "h.e.l.lo"

girl proceeds to make the connection. If the number required is in the same section of the city she simply reaches for the hole or connection which corresponds with it, with another bra.s.s plug, the twin of the one that is already inserted in your connection, and touches the bra.s.s lining with the plug. All the connections to each central station are so arranged and duplicated that they are within the reach of each operator.

If the line is already "busy" a slight buzz is heard, not only by "central," but by the subscriber also if he listens; "central" notifies and then disconnects you. If the line is clear the twin plug is thrust into the opening, and at the same time "central" presses a b.u.t.ton, which either rings a bell or causes a drop to fall in the private exchange station of the party you wish to talk to. The moment the new connection is made and the party you wish to talk to takes off the receiver from his hook, a second light glows beside yours, and continues to glow as long as the receiver remains off. The two little lamps are a signal to "central" that the connection is properly made and she can then attend to some other call. When your conversation is finished and your receivers are hung up the little lights go out. That signals "central"

again, and she withdraws the plug from both holes and pushes another b.u.t.ton, which connects with a meter made like a bicycle cyclometer. This little instrument records your call (a meter is provided for each subscriber) and at the same time lights the two tiny lamps again--a signal to the inspector, if one happens to be watching, that the call is properly recorded. All this takes long to read, but it is done in the twinkling of an eye. "Central's" hands are both free, and by long practice and close attention she is able to make and break connections with marvellous rapidity, it being quite an ordinary thing for an operator in a busy section to make ten connections a minute, while in an emergency this rate is greatly increased.

[Ill.u.s.tration: "CENTRAL" MAKING CONNECTIONS The front of a small section of a central-station switchboard. Each dot on the face of the blackboard is a subscriber's connection. The cords connect one subscriber with another. The switches throwing in the operator's "phone", and the pilot lamps showing when a subscriber wishes a connection, are set in the table or shelf before her.]

The call of one subscriber for another number in the same section, as described above--for instance, the call of 4341 Eighteenth Street for 2165 Eighteenth Street--is the easiest connection that "central" has to make.

As it is impossible for each branch exchange to be connected with every individual line in a great city, when a subscriber of one exchange wishes to talk with a subscriber of another, two central operators are required to make the connection. If No. 4341 Eighteenth Street wants to talk to 1748 Cortlandt Street, for instance, the Eighteenth Street central who gets the 4341 call makes a connection with the operator at Cortlandt Street and asks for No. 1748. The Cortlandt Street operator goes through the operation of testing to see if 1748 is busy, and if not she a.s.signs a wire connecting the two exchanges, whereupon in Eighteenth Street one plug is put in 4341 switch hole; the twin plug is put into the switch hole connecting with the wire to Cortlandt Street; at Cortlandt Street the same thing is done with No. 1748 pair of plugs. The lights glow in both exchanges, notifying the operators when the conversation is begun and ended, and the operator of Eighteenth Street "central" makes the record in the same way as she does when both numbers are in her own district.

Besides the calls for numbers within the cities there are the out-of-town calls. In this case central simply makes connection with "Long Distance," which is a separate company, though allied with the city companies. "Long Distance" makes the connection in much the same way as the branch city exchanges. As the charges for long-distance calls depend on the length of the conversation, so the connection is made by an operator whose business it is to make a record of the length in minutes of the conversation and the place with which the city subscriber is connected. An automatic time stamp accomplishes this without possibility of error.

Sometimes the calls come from a pay station, in which case a record must be kept of the time occupied. This kind of call is indicated by the glow of a red light instead of a white one, and so "central" is warned to keep track, and the supervisors or monitors who constantly pa.s.s to and fro can note the kind of calls that come in, and so keep tab on the operators.

Other coloured lights indicate that the chief operator wishes to send out a general order and wishes all operators to listen. Another indicates that there is trouble somewhere on the line which needs the attention of the wire chief and repair department.

[Ill.u.s.tration: THE BACK OF A TELEPHONE SWITCHBOARD A section of one of several central station switchboards necessary to carry the telephone traffic of a great city.]