In [Fig. 13B] is shown the diagram of circuits. The letters d d indicate the spheres of the transmitter, which are connected, one to the vertical wire w, the other to earth, and both by wires c′ c′, to the terminals of the secondary winding of induction coil, c. In the primary circuit is the key b. The coherer j has two metal pole pieces, j1 j2, separated by silver and nickel filings. One end of the tube is connected to earth, the other to the vertical wire w, and the coherer itself forms part of a circuit containing the local cell g, and a sensitive telegraph relay actuating another circuit, which circuit works a trembler p, of which o is the decohering tapper, or hammer. When the electric waves pass from w to j1 j2 the resistance falls, and the current from g actuates the relay n, the choking coils k k′, lying between the coherer and the relay, compelling the electric waves to traverse the coherer instead of flowing through the relay. The relay n in its turn causes the more powerful battery r to pass a current through the tapper, and also through the electro-magnet of the recording instrument h.
The alternate cohering by the waves and decohering by the tapper continue uninterruptedly as long as the transmitting key at the distant station is depressed. The armature of the recording instrument, however, because of its inertia, cannot rise and fall in unison with the rapid coherence and decoherence of the receiver, and hence it remains down and makes a stroke upon the tape as long as the sending key is depressed.
The principal applications of wireless telegraphy so far have been at sea, where the absence of intervening obstacles gives a free path to the electrical oscillations. The system is also applicable on land, however, and no one can doubt that if the Ministers of the Legations shut up in Pekin had been supplied with a wireless telegraphy outfit, neither the walls of Pekin nor the strongest cordon of its Chinese hordes could have prevented the long sought communication. The full story of mystery and massacre would have been promptly made known, and the civilized world have been spared its anxiety, and earlier and effective measures of relief supplied.
As the art of telegraphy grows apace toward the end of the Nineteenth Century, individuality of invention becomes lost in the great maze of modifications, ramifications, and combinations. Inventions become merged into systems, and systems become swallowed up by companies. In the promises of living inventors the wish is too often father to the thought, and the conservative man sees the child of promise rise in great expectation, flourish for a few years, and then subside to quiet rest in the dusty archives of the Patent Office. They all contribute their quota of value, but it is so difficult to single out as pre-eminent any one of those which as yet are on probation, that we must leave to the coming generation the task of making meritorious selection.
To-day the telegraph is the great nerve system of the nation’s body, and it ramifies and vitalizes every part with sensitive force. In 1899 the Western Union Telegraph Company alone had 22,285 offices, 904,633 miles of wire, sent 61,398,157 messages, received in money $23,954,312, and enjoyed a profit of $5,868,733. Add to this the business of the Postal Telegraph Company and other companies, and it becomes well nigh impossible to grasp the magnitude of this tremendous factor of Nineteenth Century progress. Figures fail to become impressive after they reach the higher denominations, and it may not add much to either the reader’s conception or his knowledge to say that the statistics for the whole world for the year 1898 show: 103,832 telegraph offices, 2,989,803 miles of wire, and 365,453,526 messages sent during that year. This wire would extend around the earth about 120 times, and the messages amounted to one million a day for every day in that year. This is for land telegraphs only, and does not include cable messages.
What saving has accrued to the world in the matter of time, and what development in values in the various departments of life, and what contributions to human comfort and happiness the telegraph has brought about, is beyond human estimate, and is too impressive a thought for speculation.
[CHAPTER IV.]
The Atlantic Cable.
[Difficulties of Laying]—[Congratulatory Messages Between Queen Victoria and President Buchanan]—[The Siphon Recorder]—[Statistics].