Mr. Wheatstone has recently so modified his telegraph as to use two needles, or galvanometers, and two extended wires, with the ground as half the circuit for the two wires. He has thus adopted Prof. Morse’s plan of using the ground as a common conductor for two or more wires. He, however, still requires two wires for one independent line of communication; one station only being able to communicate at a same time. He has no mode of recording his message, but depends upon the watchful eye of the attendant. His code of signals are based upon Schilling’s plan, heretofore described, page 155, and also Gauss and Weber’s, page 156, from whom he seems to have obtained his idea.
The two needles, or galvanometers, stand side by side, one of which is called the left needle and the other the right needle. These two needles are placed directly in front of the person who transmits. There are, also, in front, two handles, one for each hand, with which the operator transmits a message, closing and breaking the circuit of the two wires. His signals are made thus: The upper half of the left hand needle moving to the left twice, gives, a; three times, b; once to the right and once to the left, c; once to the left and once to the right, d; and, in like manner, for the other letters of the alphabet, as shown in the table which follows.
| Left Hand Needle. | Right Hand Needle. | ||||||
| ll, | A. | r, | E. | l, | H. | lr, | M. |
| lll, | B. | rr, | F. | ll, | I. | r, | N. |
| rl, | C. | rrr, | G. | lll, | K. | rr, | O. |
| lr, | D. | rl, | L. | rrr, | P. | ||
| Joint Action of Both Needles. | |||||||
| l, | l, | R. | |||||
| ll, | ll, | S. | |||||
| lll, | lll, | T. | |||||
| rl, | rl, | U. | |||||
| r, | r, | W. | |||||
| rr, | rr, | X. | |||||
| rrr, | rrr, | Y. | |||||
| r, | completed. | ||||||
| ll, | rr, | I understand, or yes. | |||||
| rl, | rl, | I do not understand, or no. | |||||
| rl, | rl, | 1. | |||||
| lr, | lr, | 2. | |||||
| r, | r, | 3. | |||||
| l, | l, | 4. | |||||
| rl, | rl, | 5. | |||||
| lr, | lr, | 6. | |||||
| r, | r, | 7. | |||||
| l, | l, | l, | l, | 8. | |||
| ll, | ll, | ll, | ll, | 9. | |||
| r, | r, | r, | r, | 0. | |||
Mr. Wheatstone does not appear to be aware of all the advantages of this, his latest plan of using two needles and two wires, since some of his signals for the numerals, are repetitions of his letter signals, and require four deflections of a single needle, with a pause between the two first deflections, and the two last, and for some other signals he requires as many as three deflections of a signal needle. He has likewise, apparently, for want of simple signals, omitted the letters, J, Q, V, Z. He could with perfect ease, obtain from his two wires and two needles, sixty-four different signals, requiring the time of only two deflections, each, and using but one hand for manipulating four keys, instead of both hands, as in his present plan. The author has demonstrated it by actual experiment.
Footnotes:
[1] These are made at the American Pottery, in Jersey City, opposite New York.
[2] The term magnet, here, is synonymously used with the iron for the magnet, as the simple iron is not a magnet, except when subjected to the action of the battery through the helices of wire around it. It would confuse the reader, if this distinction be not kept in view. Permanent magnets are those which retain their magnetism when once they are charged. They are always made of steel, and usually bent in the form of a horse-shoe. Sometimes they are of a single plate of that form, and others are constructed with many plates, side by side, fastened together so as to present a compact magnet of the same form. They are distinguished from Electro Magnets from the fact, that the soft iron of the latter depends upon the influence of the galvanic fluid for its magnetism, and retains it only so long as the soft iron is under its influence, while the former, when once submitted to the influence of the galvanic fluid, retain their magnetism permanently.
[3] One marking point will suffice.
[4] The paper used for telegraphic writing is first manufactured by the paper making machine in one long continuous sheet, of any length, about three feet and a half in width, and is compactly rolled up as it is made, upon a wooden cylinder. It is then put into a lathe and marked off in equal divisions of one and a half inches in width; a knife is applied to one division at a time, and as the roll of paper revolves, the knife cuts through the entire coil until it reaches the wooden centre. This furnishes a coil ready for the register, and is about fifteen inches in diameter. The whole roll of paper furnishes, in this way, about twenty-eight small rolls prepared for use.