Besides these signals there are a number of others for

diphthongs, punc

tuation marks, and directions. Similar signs to these are actually marked on a strip of travelling paper by the Morse receiver, or "inkwriter." This is done by the device shown in Fig. 18, where L is the line

I

M

FIG. 18.

E

wire connected to

an electro-magnet м, which is in its turn connected to the earth-plate. H is a pivoted metal lever, carrying at the

end, over the pole of the electro-magnet, a soft iron "armature," and at the other a thin brass disc, which dips into an ink-box (1) and smears its edge with ink. Above the disc runs a ribbon of paper E which is pulled along by clockwork in the direction of the arrows, and passes under the roller c. Now, when the circuit is broken by the operator working his key at the sending station, no current will flow from the line through the electro-magnet м, and consequently the spring p attached to the lever will hold the armature back, and the marking-disc will keep within the ink-box. But when the sending clerk closes the circuit a current will excite the magnet, attract the armature, and tilt up the disc against the paper, thereby making a mark, which will be a "dot" or a "dash," according as the current is short or long.

the electro-magnet, н the armature and lever, E the travelling paper, and I the ink-box, as before. The other parts indicated, such as the drawer A, the screws S, and e, are merely accessories, and the lever (K) is a Morse key, such as we have already described for sending signals. It is fitted on the same base as the receiver for convenience sake.

The Morse ink-writer has the advantage of giving a permanent record of the message, but with skilful receiving-clerks this is not essential, and hence a simpler apparatus on the same principle is gradually superseding it. This is the "Sounder," which, instead of marking the message down, beats it out with a small hammer on an anvil. Fig. 20 represents the post

office pattern of this little instrument. It consists of a powerful electro-magnet м, a hammer, H which is attracted to the magnet when the current passes, and a regulating screw s for controlling the play of the hammer. This hammer, it will be seen, is merely

the pivoted lever and armature of the Morse printer divested of the ink-marker. Now, when the dot-dash currents pass from the telegraph line through the magnet, the hammer is attracted, and hits the anvil with a succession of ringing taps, which the trained ear of the clerk soon learns to interpret as a message. The effect is transient, and there is no record of the signals to refer to in case of doubt, but it is easier to write down a message from the ear than copy it from written signals.

This fact was recognised some thirty years ago by Sir Charles Bright, when he first introduced his "Acoustical Telegraph," known and still used as Bright's Bell Instrument. In this apparatus there were two clappers which hit upon two bells or metal plates of different pitch. One clapper was actuated by a positive current sent into the line, and the other by a negative current. The American "sounder" has to a great extent superseded the Bell Instrument; but Sir C. Bright has recently introduced a new "sounder " which imports some of the merits of his bell instrument. For example, the hard metal stops of the sounder above described are replaced by tubes of Muntz's metal, which give out a musical clink when struck by the hammer, and are not only pleasanter to the ear but more easily distinguished from the ordinary sounds of a telegraph office or a railway signal box.

II.-DUPLEX AND OTHER SYSTEMS.

So far we have considered those instruments which are worked by the interruptions of a current from one

pole of the battery; but there is a class of apparatus which operates with the currents from both poles of the battery. In these the "dot" signal is made with a "positive" current, or current from the positive pole of the battery, and the "dash" signal by a negative current. Thus time is to a certain extent saved, for both signals may be short, or, in other words, "dots," only they are indicated in the receiver by opposite effects. The Single Needle instrument, shown in Fig. 21, works on this principle, and consists of a

hollow coil of wire, through which the current passes, just as it passes in the electro-magnet of the Morse receiver. In the hollow of the coil, which is inside the case, is pivoted a magnetic needle, seen in front, which moves to the left when the "dot," or positive, currents