FKENCH EAILWAY TELEGRAPH. 



189. The telegraph which is represented in fig. 74 is a portable 

 telegraph constructed for the French railways by M. Breguet. 

 This instrument, in size and arrangement, is adapted to be carried 

 in the guard's van upon the train, so that, in case of accident, it 

 may be immediately put in connection with the line-wires, and 

 notice of the circumstance may be instantly transmitted to the two 

 stations between which the accident has taken place. 



Portable instruments for a like purpose have been constructed 

 in England and elsewhere. 



The apparatus consists of a stout oaken case, containing in the 

 lower part, B B, a Daniel's battery of 18 pairs, a commutator, M, 

 and an indicating apparatus, E. A small galvanometer is placed 

 at G, to show the existence and force of the current, and a small 

 electro-jnagnet, L T. 



The dimensions of the instrument are indicated on the figure. 

 "When not in use the top, c c, attached by hinges to the case, can 

 be turned down over the commutator and indicator, so as to close 

 the entire apparatus. 



A long rod of metal terminated in a copper hook, is provided, 

 by which the end of the coil L can be put in connection with the 

 line-wire ; the end of the coil T being put in connection with the 

 earth by means of a wire terminating in a small iron wedge, 

 which is driven with a hammer into the joint between two of the 

 rails. 



.To explain the manner of applying this apparatus, let us 

 suppose an accident to happen between the stations s and s', and 

 consequently the train to be stopped. The guard takes out the 

 portable telegraph, and raising its cover c c, he puts the wire of 

 L in connection with the line-wire, and that of T within a joint of 

 the rails, in the manner described above. He then makes one or 

 two complete turns of the handle M of his commutator, observing 

 whether the galvanometric needle G is deflected. If it is, he 

 knows that he has transmitted a current to the line wires. This 

 current divides itself at the hook, and a part goes to each of the 

 stations s and s', at each of which it rings the alarum. After a 

 short interval a current is transmitted back from one or other of 

 the stations, the arrival of which is indicated by the deflection of 

 the galvanometric needle, G. The guard then informs the stations, 

 one or both, of the accident, its place, the nature of the aid he 

 requires, &c. 



In comparing this with the state telegraph, it must not be 

 forgotten that while this requires only one conducting wire, the 

 state telegraph requires two. In fact, the French state telegraph, 

 like the English double-needle telegraph, is in reality two inde- 

 pendent telegraphs, whose signals are combined for the purpose of 



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