5IO 



NATURE 



{April 29. 1875] 



THE PROGRESS OF THE TELEGRAPH * 

 IV. 



IT will only be necessary to describe generally the con- 

 struction of the Syphon or Recording Galvanometer. It 

 consists essentially of two parts ; first, that portion of the 

 machine which, being influenced by the received current, 

 oscillates or moves, thus becoming the motor or mecha- 

 nical power ; and, second, the arrangement for perma- 

 nently recording or registering this motion. The motor 

 or mechanical power is obtained by the employment of a 

 very light suspended coil consisting of a small number of 

 turns of fine insulated wire, placed in a very powerful 

 magnetic field produced by permanent magnets or 

 electro-magnets ; these act with great exciting force 

 upon the .suspended insulated wire coil, causing it to 

 deflect or vibrate when the current passes through it. 



This deflection of a vibratory coil through which a cur- 

 rent is passed, over the poles of a magnet, was the subject 

 matter of a patent in 1847, by Mr. William Sykes Ward, 

 of Leeds, in which it is stated, " Signals are indicated by 

 the defleciion of electro-dynamic coils, free to vibrate over 

 the poles of a permanent magnet ;" the deflection of the 

 coil to right or left indicating either the dot or dash of 

 the Morse alphabet, or the beats of the old double-needle 

 instrument. 



This apparatus is represented in Fig. iS. Two per- 

 manent m.-i^nets are altached to a suitable frame, over 

 the poles of which the oscillating coils are placed, the 

 lateral motions of which, to the right or left, according to 

 the direction of the current, are regulated by the stop 

 pins dii. 



In connection with each permanent magnet an adjust- 

 able permanent magnetic bar a is placed, which, acting 

 upon a soft iron exponent l> attached to the upper e.\tre- 

 mity of the oscillating coils, regulaies the sensitiveness of 

 their movement to the required degree, according as the 

 magnetic bar a is advanced or withdrawn from proximity 

 to tlie so.''t iron medium b. The completion of the circuit 

 ihroLigh the coils is indicated by the arrows and metallic 

 contacts in the illustration. 



In the Syphon Recording Apparatus, to produce the 

 maximum amount of deflection of the coil with the mini- 

 mum amount of current force, this delicate recording 

 helix is suspended so as to vibrate over a soft iron core 

 placed between the two poles of a powerful electro- 

 magnet, so that the most delicate current traversing the 

 coil receives the maximumamount of magnetic sympa.hy; 

 the space between the iron core and the poles of ihe 

 magnet being as narrow as is consistent with freedom of 

 oscillation of the coil. 



In tracing the history of the various step-by-step develop- 



* Continued from p. 472. 



ments of tlie telegraph, which will be done subsequently, 

 we shall show that a very beautiful scientific application 01 

 electrical statics, obsolete as regards practical results, was 

 developed by Henry Highton in 1846, where the voltaic 

 current was passed through a narrow strip of gold leaf 

 enclosed in a glass tube and placed in a vertical direction 

 before the poles of a powerful magnet. In this arrange- 

 ment similar results were obtained to that of the oscil- 

 lating coil over the poles of the magnet, the gold leaf 

 filament being deflected in a curve to the right or the left, 

 according as the current is passed in the one or other 

 direction from the voltaic battery through the gold leaf 

 strip. 



Having thus briefly described the motor, the second 

 part or recording mechanism of the apparatus comes 

 under notice. The function of this is to impart the motion 

 of the receiving coil to a light capillary tube or syphon of 

 glass, suspended and adjusted to the coil by means of the 

 torsional elasticity of a helical wire. The long leg of 

 this syphon acts as the marker ; the short end dips into a 

 reservoir of ink or other marking fluid which is con- 

 tinuously caused to be spurted or ejected from the end of the 

 syphon, by means of electric agency, onto a moving ribbon 

 of papermechanically drawn overametalplateelectrified in 

 an opposite direction to that of the syphon. Thus a power- 

 ful difference of potential or electrical equilibrium is con- 

 stantly maintained between the tube and the metal plate, 

 the tendency to produce equilibrium resulting in a succes- 

 sion of sparks between the syphon and the metal plate, 

 producing a fine stream of ink or a succession of minute 

 dots on to the surface of the moving paper ribbon. A very 

 fine hair-pencil maybe attached to the syphon as a capillary 

 marker, and so dispense with the electrical arrangement. 

 If the syphon remains in a neutral position, a continuous 

 line will be drawn over the paper, but when by reason of 

 the motion of the receiving coil the syphon is drawn either 

 to the right or left, a corresponding deviation from the 

 straight line will be indicated ; thus a record is maintained 

 on paper of the movements of the coil, without that move- 

 ment being in the least degree impeded by friction or 

 any other mechanical defects. To develop fully the effec- 

 tive results of this most delicate recording apparatus, it is 

 evident that some means must be employed more accurate 

 than the human hand for the transmission of the several 

 electric groups and sequences of currents passing through 

 the wire which severally and collectively compose the 

 message. From facts that have been already stated re- 

 garding the rapid transmission of electric currents through 

 extended submarine cable circuits, it will be remembered 

 that with a view to obtain a maximum amount of speed, 

 the electric throbs transmitted by the cable should be of 

 equal duration and at equal intervals of time, so as to 

 allow mechanically for the regular difference of tension in 

 the current at the distant end, as well as for the charge 

 and discharge of the circuit. An automatic transmitter for 

 passing the several currents and groups of currents into 

 the circuit is therefore employed. The details of con- 

 struction of this essential piece of mechanism will 

 be given in the following description of Sir Charles 

 Wheatstone's automatic high-speed printing instru- 

 ment. It is only natural 10 suppose that there are 

 several automatic transmitters scheduled in the Patent 

 Office : the reader does not, however, require to become a 

 dictionary upon patent lore or mechanical variations of 

 electrical apparatus, but simply to acquire a general 

 knowledge of the progress of the telegraph up to the year 

 1875. 



In years long since passed, the invention and introduc- 

 tion of the Jacquard Loom produced a vast revolution in 

 the processes of weaving ; by its means an automatic 

 recoid of the groups and sequence of the threads neces- 

 sary to produce the pattern by being raised to the surface 

 of the cloth was maintained, and a simple mechanical 

 arrangement performed simultaneously with the succes- 



