R. Riordan

“ The earth, reacting on the line wire suspended above it, induces in it what is called an extra current, both on closing and breaking the circuit. On first closing the circuit the extra current runs in the contrary direction to the primary, and retards and weakens its action, so that, if suffered to record itself, it would do so by a mark like this: the long after-part being caused partly by the accumulated electricity and partly by the second extra current which is in the same direction with the primary one. ”

“ But when the key is depressed the spring comes in contact with a screw, to which another circuit is connected, applying the full strength of the battery to the line. The circuit across the key is never broken, because the spring remains in contact with the arm of the key until it begins to press against the screw. This key works the magnet M, which has its retractile spring so adjusted as to be overcome only by the full intensity of the current when the key is down. ”

“ But, if a similar extra volume be at the same time sent from B, the pressure in that part of the circuit between W and X will overcome the opposing forces at each of the points, and both wheels will be worked, each virtually by the distant reservoir and not by its own.
If we substitute galvanic batteries for the reservoirs, wires for the water-courses, and electricity for the water, this gives us the principle of the duplex telegraph, and it is obvious that no currents passing one another in contrary directions are necessary to it. ”

“ In most of the plans so far made public, a fixed steel bar takes the place of the tuning-fork, and therefore of the armature as well. When attracted by the magnet, on making a signal, it is of course set vibrating; and, at every forward vibratory movement, it closes the circuit and transmits an electric impulse. ”

“ Where three holes come together, both wheels form a contact, and a dash is produced, because the second wheel touches the cylinder while the first passes over the paper between the upper holes.
The germ of the automatic system, as we have described it, was contained in the "Chemical Telegraph" invented by Alexander Bain, a Scotchman, in 1846. ”

“ This effect was found to be so marked that a person drawing a strip of metal along the paper—leaning rather heavily on it—finds his hand obliged to move in a succession of jerks when signals are sent by a current powerful enough to overcome the resistance of his body. On this principle, Mr. Edison has constructed a little instrument in which a style is kept pressed against the paper by springs so as to make a continuous indentation, except when the current is passing. ”

“ After the perforated slip of paper has been prepared, it is taken to the operator's table, where it is made to move forward rapidly between a metallic drum and a needle carrying two small steel wheels which rest upon it. Drum and wheels form part of the circuit, which is broken by the non-conducting paper interposed and closed when the holes permit of the wheels and the metallic cylinder beneath coming into contact. ”

“ If an additional volume of water come from A, being equally divided on each side of W, it will not move that wheel, but it will move the wheel X by destroying the balance which previously existed there. ”