TELEGRAPHIC STATIONS. 



Ashford, and Folkestone. The conducting wire passes tkrough 

 the telegraph offices at these three intermediate stations, but does 

 not enter any of those of inferior importance, such as Godstone, 

 Penshurst, Marden, Staplehurst, &c., to the service of which other 

 conducting wires and instruments are appropriated. 



125. Since, however, telegraphic communication must be pro- 

 vided between all the intermediate stations, and since the chief 

 wires passing the chief intermediate stations do not enter the 

 secondary ones, it follows that the wires of the secondary stations 

 must be carried not only to the terminal stations, but also through 

 all the chief secondary stations. Thus the wires, which pass through 

 the stations of Godstone and Penshurst, must also pass through 

 those of Tonbridge, Ashford, and Folkestone, since otherwise there 

 could be no communication between the latter and the former. 



From what has been already explained, it will be understood 

 that every two secondary stations along the line can communicate 

 at the same time with each other, no stations being compulsorily 

 silent, except such as may lie between two communicating ones. 

 To illustrate this, let us suppose the secondary stations from ter- 

 minus to terminus of the line to be expressed by the small letters, 

 and the chief stations, terminal and intermediate, by the capitals, 

 in the following order : 



A, b, c, (I, c, F, </, h, t, K, /, m, n, 0. 



Xow, by the secondary wires A and b, b and c, c and d, and so on, 

 may at the same moment hold communication. But if A and d 

 communicate, b and c can communicate neither with each other, 

 or with any other station. They are compulsorily silent. In like 

 manner, if A and m communicate, b, c, d, e, g, h, i and I are all 

 eompulsorily silent. 



Hence it will be apparent how necessary it is to put chief inter- 

 mediate stations like F and K on the primary wires, since if they 

 eould communicate with A and o only by the secondary wires, 

 frequent interruptions to the communications of all the secondary 

 stations with each other would take place. 



It will be also apparent that on lines of great intermediate 

 business, a third or even fourth system of wires would be necessary. 



This will render it easily understood why such a multiplicity of 

 wires are seen stretching along the parts of the lines near London. 



Lines of telegraph, like lines of railway, often have branches 

 which are connected either with the primary or secondary wires of 

 the main line, or with both, according to their importance. For 

 example, on the main line between London and Dover, there are 

 branches which go to Maidstone on the one side, and to Tonbridge 

 Wells on the other. Sometimes these branch wires are provided 

 with means of connection with the main line wires, so that the 



185 



