Discoveries and Inventions of the Nineteenth Century

a question of the reversal of currents sent from the same battery; the key merely enables the operator to send a current in one direction, so as to affect the distant electro-magnet whenever or so long as he depresses the key. We shall now examine the construction of the Morse receiving apparatus, one of the most complete forms of which is depicted in Fig. 286. In the present description we wish the reader to consider only the portion of the apparatus towards the left, and to suppose the absence of the electro-magnet at the right-hand side, with all the appliances immediately connected with it. He must regard the electro-magnet, A, as corresponding with M´ in Fig. 285, and remember that it is in the power of the distant operator at K to throw the current of his battery through the coils of A, by simply depressing his key. When the current passes the armature, B, it is attracted, and the lever, C, to which it is attached, turns on its bearings at D, and the end, E, of its longer arm is pressed upwards. At this end of the lever, in the earlier form of the instrument, was a blunt steel point which, while the armature was attracted to the electro-magnet, was 559pressed into a shallow groove in a metallic roller. Between the roller and the steel point a paper ribbon, half an inch wide, K, was unwound from the drum, L, by the two rollers, M and N, which grip the paper between them as they are turned by clockwork within the case, F. Fig. 286.—Morse Recording Telegraph. An important improvement was effected when, instead of steel points for embossing the message, the Morse instrument was provided with an arrangement for printing the signals in ink; since the pressure required for embossing the paper is considerably greater than that needed merely to bring it into contact with the edge of a little inked disc. In the inking arrangement the strip of paper travels just below the margin of a vertical disc, turned by the clockwork, and having its plane parallel to the length of the paper strip. The narrow edge of this disc is kept charged with printer’s ink, which it receives from a roller. The end of the lever connected with the armature of the electro-magnet is formed of a light strip of metal carrying a narrow projection at the end, over which the paper passes, just beneath, but not touching, the inking disc. When the current passes, the little projection is lifted up, and raises the paper into contact with the ink, printing either a dot or a dash according to the duration of the current. The amount of force required to raise an inch or two of the length of the paper ribbon through a space not greater than the twentieth of an inch is but small, and much less than would be required to emboss the paper; so that in a great many cases the part of the apparatus which is represented in Fig. 286, on the right, may be dispensed with. In other cases it is, however, necessary; as when, from the length of the line, the currents are too feeble to give clear indications with the printing lever; and we shall, therefore, presently describe its arrangement and purpose. The clockwork is actuated by a spring, wound by the handle G, but its 560action is suspended by a detent, which is released by touching the lever H. When the clockwork is in action and the current constantly circulating in the coils, a continuous line, parallel to the length of the ribbon, would be printed upon it, in consequence of the contact with the inking-disc, P, being maintained; but when a momentary current only rushes through the coils, the armature attracted but for an instant, gives rise to merely a dot on the passing paper, while a current of a little duration will cause the paper to be marked with a short line or dash. The dot and the dash are the elementary signs of the Morse code of signals, and these are producible according to the time the contact key is held down at the distant station. By employing various combinations of these two signs, the letters of the alphabet, numerals, &c., are indicated. In selecting the combinations Professor Morse had regard to the frequency with which the different letters recur in the English language. Thus, for the letter E, which is more frequently used than any other, the symbol chosen was a single dot; and for T, which is the next most frequently employed, the dash was plainly the most appropriate; then the four only possible combinations of the signs in pairs fell to the next most frequent letters, and so on. The following table gives the complete Morse code. The eye of the reader will doubtless detect a kind of symmetry in the arrangement of the signs for the first five and last five numerals: ALPHABET. Letter. Sign. A ·- Ä ·-·- B -··· C -·-· D -·· E · É ··-·· F ··-· G --· H ···· I ·· J ·--- K -·- L ·-·· M -- N -· O --- Ö ---· P ·--· Q --·- R ·-· S ··· T - U ··- Ü ··-- V ···- W ·-- X -··- Y -·-- Z --·· Ch ---- NUMERALS. Numeral. Sign. 1 ·---- 2 ··--- 3 ···-- 4 ····- 5 ····· 6 -···· 7 --··· 8 ---·· 9 ----· 0 ----- 561 PUNCTUATION, &c. Sign. Full stop ······ Colon ---··· Semicolon -·-·-· Comma ·-·-·- Interrogation ··--·· Exclamation --··-- Hyphen -····- Apostrophe ·----· [6]Fraction-line ------ [7]Inverted commas ·-··-· [7]Parenthesis -·--·- Italics or underlined ··--·- New line ·-·-·· 6. To be placed between the numerator and denominator of a vulgar fraction. 7. To be placed before and after the words to which they refer. OFFICIAL SIGNALS. Sign. Public message ··· Official Telegraph message ·- Private message ·--· Call -·-·-·- Correction, or rub out ···-· Interruption ········· Conclusion ·-·-·-· Wait ·-··· Receipt ·-··-··-· The length of a dot being taken as a unit, the length of a dash = 3 dots. The space between the signs composing a letter = 1 dot. The space between two letters of a word = 3 dots. The space between two following words = 6 dots. Fig. 287.—Morse Transmitting Key. Fig. 288.—Morse Transmitting Plate. Fig. 287 is a view of the Morse transmitting key. A B is a brass lever, moving in bearings at C, and provided at the end of its longer arm with a large knob or button of some insulating material. Steel pins are screwed in at B and D, and they are so adjusted that while that at B is pressed against the 562projection, E, by the action of the spring, F, when the knob, K, is pressed, contact is broken at B, and established at D. D and E are each provided with a binding-screw, so that wires may be attached in the manner indicated in Fig. 285. When the key is in the position shown, a current arriving by the line-wire passes from the fulcrum, C, of the lever through the contacts into the apparatus. When the knob is pressed down the battery current enters the lever by the contact at D, and passes into the line from the fulcrum, C. The clerks who are called upon to transmit messages usually soon learn to time the contacts very accurately in accordance with the code of signals, so as to produce the dashes and lines with accuracy. However, with certain persons some difficulty was found in acquiring the requisite uniformity, and to obviate any objection on this score, Morse invented an arrangement for facilitating the signalling, which is represented in Fig. 288. This is a smooth tablet of a non-conducting substance, such as ivory, except the shaded portions, which are plates of metal having their surfaces even with that of the ivory, and all soldered to a plate of metal beneath the ivory, which places them all in communication with each other and with 563the binding-screw, C. The lengths of the strips of metal and those of the spaces between them correspond with the dots and dashes of the Morse alphabet as marked on the tablet. The battery wire is connected with the binding-screw, C, and the line-wire terminates in an elastic and flexible coil of insulated wire, which is attached to a short rod having an insulated handle and terminated by a blunt platinum point. This the transmitter takes in his hand and draws uniformly along the line of metal strips belonging to the letter which he wishes to telegraph. The circuit is closed while the point of the style is passing across the metallic strips. This arrangement appears to be but little used, but it is nevertheless admirable for its simplicity, and is described here as a good illustration of the mode in which the varied duration of the contacts is able to produce the signals of the Morse alphabet. With the ordinary transmitting key a clerk is able to telegraph, on the average, twenty or twenty-five words in a minute, but the receiving apparatus is capable of recording three times as many. Morse also invented a system of transmitting the messages automatically, by setting up the message in a kind of type, just as ordinary letters are arranged for printing. The type, if it may be so called, had simple projections like the slips of metal, corresponding with each letter in Fig. 288. The lines of the message were drawn under a contact-lever, which closed the circuit when lifted up by the projections. Thus the speed of transmission could be very greatly increased, and a single wire and apparatus had its capacity of conveying a great number of messages in a given time proportionately enlarged. We have now to ask the reader’s attention to the details of the apparatus in Fig. 286, the use of which has not already been pointed out. The electro-magnet, O O´, and the parts immediately connected with it, form what is called a relay. The object of this may be illustrated by supposing that the instrument is at one end of a long line, such as that between Edinburgh and London. Let us suppose it is at Edinburgh: the currents sent from London by a battery of convenient size might not be powerful enough to magnetize the soft iron of A with sufficient intensity to give clearness to the signals. They are, therefore, made to circulate in the electro-magnet, O, where they act by attracting the armature, W, which has the form of a split tube of soft iron, attached to a very light lever, Q, adjusted with great delicacy, and so that it moves by little magnetic force. The end of the lever works between two adjustable screws, R and S, which are electrically insulated, except that R is in communication with one extremity of the coils of the electro-magnet, A. Q is in metallic communication through the pillar, T, and the binding-screw, U, with the zinc end of a battery at Edinburgh, which is called the local battery, the other pole of which communicates with the other ends of the coils, A, through the screw, U´. When no current from London is passing through O, Q is held down by the spring, W´, and the circuit of the local battery is broken; but the instant the line-current passes, the armature, W, is attracted, and Q makes contact with R, the current from the local battery rushes through the coils, A, and the appropriate movements of the printing lever are effected by its action. X is a spring for drawing down the lever, and it is provided with a screw for adjusting its tension, and Y, Z, are screws for limiting the extent of motion of the lever; under P is the little projection by which the band of paper is pressed against the inking-disc; l and e are respectively the screws for the line and earth connections. An extremely ingenious system of signalling, by which the speed could 564be greatly increased, has been devised by Sir Charles Wheatstone, and is largely adopted by the British postal authorities. In this system the message is first translated into telegraphic language by a machine, which punches certain holes in a strip of stiff paper. The apparatus originally designed for this purpose by the inventor is thus described by him in the Juror’s Report, International Exhibition of 1862: “Long strips of paper are perforated