CELERITY OF HOUSE'S TELEGRAPH. 



239. Although the distance to which the dispatch has to be 

 sent cannot be said directly to affect the celerity of transmission, 

 there are circumstances nevertheless which in practice render the 

 transmission to great, slower than to lesser distances. In Europe, 

 for example, stations separated by great distances, are generally 

 in different countries, and the telegraphic line which connects 

 them often passes through several different states in which 

 different telegraphic systems are used, and where it is not practi- 

 cable to put the wires proceeding from one direction in immediate 

 connection with those which proceed in another. In such cases 

 the messages which arrive must be taken down and retransmitted 

 in the direction in which they are intended to be forwarded, and 

 on this account alone, the time of transmission is augmented, at 

 least in the ratio of the number of such repetitions which are 

 necessary. But besides this, it rarely happens that a message 

 on arriving at such intermediate station can be at once for- 

 warded. It must wait its turn unless the wires happen to be 

 unoccupied. 



And even though it may be practicable to establish a direct 

 communication between two distant stations by putting the wires 

 in immediate connection, more or less delay must necessarily take 

 place. The telegraphist who transmits, must first send a message 

 along the line to all the intermediate stations to require the wires 

 to be united for direct communication. At these intermediate 

 stations, the wires may be employed, and the message must wait 

 until they are free. 



Thus, although it be true that so far as the electric fluid and the 

 ^apparatus by which it is transmitted are concerned, they are 

 capable of sending a message from pole to pole in an inappreciable 

 interval, yet the machinery of telegraphy as practically constructed 

 presents causes of delay which prevent in many cases this vast 

 oelerity from being called into action. 



Until very recently, a message transmitted from Milan to Paris, 

 being necessarily sent round by Trieste, Vienna, Berlin, and Brussels, 

 was more than twenty-four hours in reaching its destination. 



Besides these causes of delay, there are, however, others. It 

 has been stated that the intensity of the current is diminished, 

 ceteris paribus, as the distance is augmented. When transmission 

 therefore to great distances is required, various expedients, at 

 intermediate stations, such as relay batteries or relay magnets, or 

 both, are required, and notice must be given to apply these even 

 when they are provided. 



The chances of interruption by reason of defective insulation or 

 accidents to the wires, are also increased in proportion to the 

 distance. 



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