Yet not a single feature of the invention of Morse, as formulated in his caveat and described in his original patent, is to be found among the essentials of modern telegraphy. They had mostly been abandoned before the first line had been completed, and the arrangements of his associate, Vail, were substituted. Professor Joseph Henry had, in 1832, constructed an electromagnetic telegraph whose signals were made by sound, as all signals now are in the so-called Morse system. He hung a bar-magnet on a pivot in its center as a compass-needle is hung. He wound a U-shaped piece of soft iron with insulated wire, and made it an electro-magnet, and placed the north end of the magnetized bar between the two legs of this electro-magnet. When the latter was made a magnet by the current the end of the bar thus placed was attracted by one leg of the magnet and repelled by the other, and was thus caused to swing in a horizontal plane so that the opposite end of it struck a bell. Thus was an electric telegraph made as an experimental toy, and fulfilling all the conditions of such an one giving the signals by sound, as the modern telegraph does. It lacked one thing--the essential. [[23]]
[23.] The details of the construction of the modern telegraph line are not here stated. There are none that change, in principle, the outline above given.
The Vail telegraphic alphabet had not been thought of. Had such an idea been conceived previously a message could have been read as it is read now, and with the toy of Professor Henry which he abandoned without an idea of its utility or of the possibilities of any telegraph as we have long known them. Morse knew these possibilities. He was one of the innumerable eccentrics who have been right, one of the prophets who have been in the beginning without honor, not only in respect to their own country, but in respect to their times.
[CHAPTER II.]
THE OCEAN CABLE.--The remaining department of Telegraphy is embodied in the startling departure from ancient ideas of the possible which we know as cable telegraphy, the messages by such means being cablegrams. About these ocean systems there are many features not applying to lines on land, though they are intended to perform the same functions in the same way, with the same object of conveying intelligence in language, instantly and certainly, but under the sea.
The marine cables are not simple wires. There is in the center a strand of usually seven small copper wires, intended as the conductor of the current. These, twisted loosely into a small cable, are surrounded by repeated layers of gutta-percha, which is, in turn, covered with jute. Outside of all there is an armor of wires, and the entire cable appears much like any other of the wire cables now in common use with elevators, bridges, and for many purposes. In the shallow waters of bays and harbors, where anchors drag and the like occurrences take place, the armor of a submarine cable is sometimes so heavy as to weigh more than twenty tons to the mile.
There are peculiar difficulties encountered in sending messages by an ocean cable, and some of these grow out of the same induction whose laws are indispensable in other cases. The inner copper core sets up induction in the strands of the outer armor, and that again with the surrounding water. There is, again, a species of re-induction affecting the core, so that faint impulses may be received at the terminals that were never sent by the operators. All of these difficulties combined result in what electricians term "retardation." It is one of the departments of telegraphy that, like the unavoidable difficulties in all machines and devices, educates men to their special care, and keeps them thinking. It is one of the natural features of all the mechanical sciences that results in the continual making of improvements.
The first impression in regard to ocean cables would be that very strong currents are used in sending impulses so far. The opposite is true. The receiving instrument is not the noisy "sounder" of the land lines. There was, until recently, a delicate needle which swung to and fro with the impulses, and reflected beams of light which, according to their number and the space between them spelled out the message according to the Vail dot-and-dash alphabet. Now, however, a means still more delicate has been devised, resulting in a faint wavy ink-line on a long, unwinding slip of paper, made by a fountain pen. This strange manuscript may be regarded as the latest system of writing in the world, having no relationship to the art of Cadmus, and requiring an expert and a special education to decipher it. Those faint pulsations, from a hand three thousand miles away across the sea, are the realization of a magic incredible. The necromancy and black art of all antiquity are childish by comparison. They give but faint indications of what they often are--the messages of love and death; the dictations of statesmanship; the heralds of peace or war; the orders for the disposition of millions of dollars.