148 THE ELECTRIC TELEGRAPH. 



piece of platinum wire kept at a white heat by the passage of 

 a voltaic current, in place of the inking apparatus or style. 

 Messrs. Farmer and Batchelder of Boston constructed a 

 recording telegraph in which they only scorched the paper. 

 A platinum point was connected by a lever with the arma- 

 ture of an electro-magnet, and brought into contact with 

 tissue paper by opening and closing the circuit. The 

 platinum point was kept red hot by a spirit lamp under- 

 neath. 



90. Morse Apparatus worked by Closed Circuit. The method 

 adopted by Kramer, and also by Morse in an early telegraph 

 of his, of working by interruptions of a current instead of by 

 occasional currents, has been taken up by Frischen, and used 

 by him on the Hanoverian railway lines for working the 

 Morse instruments. 



" A great advantage of this arrangement/' says Frischen,* 

 " is that, on lines with several intermediate stations, only the 

 terminal station requires to be provided with a line battery, 

 whilst a local battery is necessary at each intermediate 

 station. By this the cost of batteries is considerably reduced ; 

 besides which, the relays, by reason of the uniform current, 

 do not require often to be adjusted; and the employe is 

 enabled to place confidence in the call signal without con- 

 tinually having the apparatus under his eye. The last point 

 is of particular importance when the employe entrusted with 

 the care of the apparatus has other business to attend to, 

 which is often the case on railway lines. 



In arranging a Morse line for closed circuit between two 

 stations the line current must traverse the galvanometer, 

 relays, and keys in such a way as to hold the tongues of the 

 relays on their reposing or insulated contacts, and the galva- 

 nometer needles permanently deflected. When a signal is 

 given by interrupting the circuit, the force of the adjusting 

 spring of the ordinary relay, or the superior attraction 

 of the nearer pole of the polarised relay, must be sufficient 

 to overcome any residuary magnetism which may be in 

 the cores of the electro-magnet, and by pulling it against 



* Brix. Journal, v. p. 214. 



