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. [Illustration: DIAGRAM OF TELEGRAPH SYSTEM.] 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.