362 SEC. 10. -ELECTRICITY. 



and constructed by Fonrobert and Bruckner* By machines after 

 this model numerous subterranean lines in Germany and Russia 

 were constructed from 1847 to 1851, and submarine lines are now 

 made in the same manner. 



1615. Plate Lightning Conductor, employed first by Sie- 

 mens in 1848 between Eisenach and Frankfort. 



1616. Double Style Apparatus, with writer in relief 

 (Siemens). 



Constructed by Siemens in 1853. The lines made by Siemens and Halske, 

 the Warsaw-Petersburg, and other telegraph lines, were at first worked with 

 apparatus of this system. 



1617. Polarised Relay for the above. Oldest form without 

 a steel magnet. The magnetic induction of the core and armature 

 is effected by a branch current of the local battery. (Siemens, 

 1851.) 



1618. Key for the Polarised Belay. 



1619. Magneto-electric Current Generator, with 28 pairs 

 of magnets. 



1620. Dynamic Mine Exploder (Siemens, 1850). 



1621. Polarised Belay for Double-style Apparatus, 



with steel magnets (Siemens, 1852). 



1622. Hand-puncher for Self-acting Sender. 



1623. Transmitter for Self-acting Sender. 



1624. Receiver for Self-acting Sender (Morse with sus- 

 pended magnets). 



1625. Belay for Self-acting Sender (with suspended mag- 

 nets). 



Employed by Siemens in 1855 in the first experiments made to employ 

 short alternating currents of equal duration for production of Morse writing 

 with aid of a polarised relay. 



1626. Mile Resistance, with movable steel lever; Siemens, 

 1854. 



1626a. Mile Besistance. 



1627. Original Colour-writer of John, Prague, 1854. 



1628. Belay with suspended magnets and double coils for 

 conversation. JFrischenand Siemens, 1854. Patented in Prussia, 

 with resistance scale divided according to miles of copper wire, 

 1" diameter. As made by Siemens since 1848. 



