Part 29

Nearly fifty years ago Maxwell (1831-1878) professor of physics at Cambridge University, England, conceived the idea that light is electricity of a very short wave length.

Nearly twenty-five years ago Heinrich Hertz (1857-1894), in Germany, proved by experiments the existence of electric waves, and measured their length and velocity, determining their various characteristics as compared with light.

About fifteen years ago Marconi developed a wireless telegraph apparatus, which made it possible to use electric waves for purposes of communication.

Thirteen years ago (1897) the first wireless telegraph company was formed. Eleven years ago (1899) the international yacht races in New York Harbour were reported by wireless telegraph, and bulletin boards in New York City announced to waiting crowds the details of the race while it was in progress. Nearly ten years ago (1901) wireless despatches were first sent across the Atlantic Ocean. Wireless telegraphy was opened for public use in 1905, and very soon the company began to coöperate with the regular telegraph companies. Nearly all coastwise and trans-Atlantic steamers are now equipped with wireless telegraph outfits, and a law has passed both houses of Congress making it obligatory on the part of steamers which carry fifty or more passengers to have such equipment. On several disabled steamers, notably the Republic, loss of life has been averted by the wireless emergency call for help, to which the captains of all steamers feel obliged to respond. If you desire to communicate with a friend who left for Europe several days ago, you simply write him a telegram, addressing it to his ship, and deliver it at your nearest telegraph office. Each telegraph office has a record of the location of every ship having a wireless telegraph outfit. It despatches your message to the wireless station along the coast which is nearest to your friend's steamer, and from this station it is sent on the ether to the ship. Or in some cases it may be repeated from one ship to another along the Atlantic highway until it reaches the desired one. Thus also news of important events on either continent is distributed daily on board ships which are crossing the ocean. There are said to be more than 50,000 amateur wireless stations in the United States, and already Congress is taking steps to regulate the use of the wireless telegraph in order to prevent interference with Government and other important messages.

More than three dozen books and countless magazine articles have already been written upon wireless or ether wave telegraphy. Hundreds have and thousands are contributing to our knowledge of ether wave phenomena. If the names of all who have said or done something to render stable the foundations of this idea of a universal ether, whose undulations account for the phenomena of heat, light, and electricity, were to be mentioned, the list would contain nearly all the important workers in the field of physics for the last century.

XXVI

ELECTRIC CURRENTS CANNOT BE CONFINED TO WIRES

Harold said that if electricity was so much like light that it could go without wires he thought light ought to be enough like electricity to be conducted by wires on occasions. I told him that I had no hope of being able to confine light to a wire; indeed, if the Science Club would give me an opportunity I would show them that even when electricity follows the general direction of a wire its influence is not confined to the wire. As a result of this bid I received an invitation to address an open meeting of the Science Club.

In my first experiment on that occasion I took a one-pound spool of No. 24 cotton-covered copper wire and crowded the hole in the spool full of wire nails A (Fig. 198). I disconnected the wires from an electric drop lamp and connected them to b and c, the ends of the wire from the spool. Our electric lighting circuit was what is called the alternating current. I also had a second spool, B, precisely like the first. The wires from this were connected to a miniature lamp, L, such as is used at the switchboard of a telephone exchange. We then screwed the drop-light plug into the chandelier and turned on the electric current. I brought spool B with the miniature lamp near to spool A, as shown in Fig. 199, and when it was within a distance of about two inches the little lamp lighted up to full brilliancy, thus showing that while the electric current is passing in the wire of spool A its influence is not confined to the wire, but exhibits itself in the region outside of the wire. To illustrate still further this fact we substituted an electric bell in the place of the lamp L, and when the spool B was brought near to A the bell rang. But the most striking illustration was obtained when a telephone receiver was put in the place of L. With this held to the ear while the spool B was brought toward A a humming sound could be heard when B was about a foot distant from A. This sound grew rapidly louder as B approached A, until, when the spool B rested upon the spool A, a sound like the peal of a pipe organ was heard all over the apartment. The tone was very nearly that of the key on the piano which is two octaves below middle C. I unscrewed the cap on the large end of the telephone receiver, took it off, and moved the thin iron diaphragm to one side, when it began to dance about at great speed. It was keeping time with the dynamo, five miles away, which generated the electric current. The dynamo changed the direction of the electric current sixty times per second, and this made sixty vibrations per second. The dynamo sent out ether waves which affected the telephone receiver, although the receiver was not connected to the dynamo by wires.

To emphasize the fact that the dynamo had lighted the lamp, rung the bell and made the telephone receiver hum without being connected with them, I repeated all these experiments in a different way. Spool A, connected as before with the electric lighting circuit, was concealed beneath the table. For spool B I substituted spool C (Fig. 199), on which the wire was wound so as to appear like a candlestick. On the top of this was placed the miniature electric lamp screwed into a miniature socket and connected to the wires of the spool. This "Witches' Candle," as we called it, was sitting unlighted upon the table when I called attention to the fact that if I moved it to a certain spot upon the table it flashed into full light. (Of course this spot was directly over spool A.) I moved it slowly away from that spot and its light slowly grew dim and disappeared.

On the table was also sitting a cream pitcher in which I had placed spool B with a buzzer attached to it. Remarking that this pitcher groaned for more cream whenever it was empty, and thus of its own accord called the waiter, I moved it to the spot on the table directly over spool A, when the buzzer gave forth a sound like a husky bumble-bee shut up in a resounding bottle. At this signal my assistant came in and took up the pitcher and placed my silk hat upon the table, when it instantly boomed forth a base note two octaves below middle C of the piano. Out of the hat I took a coil and the telephone receiver and the mystery was solved.

In 1819 Hans Christian Oersted in Denmark (1777-1851) first noted that the region about a wire carrying an electric current has an influence upon a magnet. I will show this fact by a simple experiment. I magnetize a stout sewing needle by drawing it from end to end across the pole of a steel magnet, and by means of a triangular piece of paper and a fine thread I suspend it a few inches above the table (Fig. 200). I then lay upon the table a piece of wire parallel with the needle and fasten one end of it to one binding post of a dry cell. Whenever I touch the other end of the wire to the other binding post of the cell, thus sending an electric current through the wire, the magnetized needle is deflected at right angles.

This experiment, performed by Oersted, seems to have started Faraday upon that wonderful series of researches which has resulted in giving us the dynamo.

XXVII

WIRELESS TELEGRAPHY IN EARNEST

We had decided to let Harold make a trip to Europe alone. The first message from him after his departure was a brief note to his mother saying that they had had a turbulent voyage, but all had landed safely upon the other side, none the worse for their experiences.

The next day a number of letters came to me from total strangers. One of these ran as follows:

My Dear Sir:

Prompted by my own impulses, and urged to do so by the passengers under my charge, I improve this first opportunity to express to you our high appreciation for your noble but very modest son, to whom more than to any one else we owe the lives of all on board our fated ship.

I am sending this direct to you both, because I understand a father's heart and because the young man escaped as soon as we came to land, without any of us learning his address. I beg you will communicate to him the desire of the president of our company to meet him and personally to thank him for his gallant conduct. I am also instructed to say that whenever Harold desires to cross the ocean the best which any ship I may command can afford will be his without charge.

Very respectfully yours, -------- Captain. S. S.

Another letter was the following:

My Dear Sir:

Permit me to congratulate you on having such a heroic and self-possessed son. We, his fellow passengers, are, if possible, as proud of him as you must be.

I fear that his account of the affair will not do himself full justice, and so, with your permission, I will give you the full details as I have gathered them from the passengers, from the crew, and from my own observation.

During the last night of our voyage a thick fog closed about us. The constant blowing of the fog whistle made the night dismal. Few persons slept at all. About two o'clock in the morning the ship struck a reef, and instantly it seemed as though every person on that ship reached the decks at the same time. The water poured in and put out the fires. The ship heeled badly, and it seemed that any minute she might slip off the reef on which she was resting into deep water and go down. To add to our horror fire broke out. It seems to have started in the wireless operator's room.

Very much damage was done to the wireless outfit itself, and the operator was badly burned, so much so that he was taken to the ship's hospital suffering with many painful and dangerous wounds.

Meanwhile the flames spread rapidly and we were unable to summon help. The crew and many of the passengers fought the flames, but with little success.