ELECTRIC TELEGRAPH. 



MAGNETIC NEEDLE TELEGRAPH. 



220. The Magnetic Telegraph Company, retaining the needle 

 indicators generally used in England, have rejected the galvanic 

 "battery, and substituted the magneto-electric for the voltaic 

 current. The instruments they have adopted are those which 



Fig. 90. 



were patented by Messrs. Henley and Forster, with some modi- 

 iications. 



This form of telegraph, enclosed in its case, is shown in fig. 91 

 (p. 97), and divested of its case in fig. 90. 



The current is produced by electro-magnets, whose poles are 

 moved in close proximity with those of strong compound per- 

 manent magnets. These latter are represented at A (fig. 90). At 

 their poles a straight piece of soft iron is placed, by the inductive 

 influence of which the magnetism of the several bars composing 

 the compound magnet is collected and combined. The electro- 

 magnets are formed in the usual way, and are mounted on 

 centres on which they are turned by levers, which project from 

 either side of the case, so that the agent can work one with 

 each hand. "When they have been pressed down by the hand 

 they are raised to their former position by springs which are 

 fixed on their axle. 



When these levers are pressed down, the electro-magnets are 

 reversed in the relation of their poles to those of the permanent 

 magnets, and momentary currents are transmitted on the con- 

 ducting wires, and when the levers are observed to rise to their 

 former position, momentary currents are again transmitted, but 

 in a contrary direction. 



The currents thus transmitted on the line-wires are received at 



the station to which the dispatch is transmitted upon the coils of; 



electro -magnets, which are placed under the desk upon which the 



indicating needles are placed, and they impart temporary 



58 



