XI. APPLICATIONS. 365 



26. Differential galvanometer, constructed on the double shunt principle. 



27. Sounder telegraph instrument with split armature. 



28. Set of ink recording instruments for duplex telegraphy, according to 

 the differential system. 



29. Double current Morse key with automatic switch for sending and re- 

 ceiving position, to be used with a single battery. 



30. Morse key for testing purposes. 



31. Double current Morse key for testing purposes. 



32. Double current Morse key for signalling. 



33. Discharging key. 



34. Magneto induction bell with inductor of 6 magnets, for signalling on 

 railways, mines, inclines, &c. without the use of batteries. 



35. Magneto induction bell, similar to the above. 



36. Ditto ditto. 



37. Magneto inductor of 6 magnets, without bell. 



38. Dynamo-electric exploder for low tension (quantity) fuses, used for 

 blasting and torpedo firing purposes. 



This apparatus consists of an ordinary Siemens' armature, which is caused, 

 by the turning of a handle, to revolve between the poles of an electro- 

 magnet. The coils of the electro-magnet are in circuit with the wire of the 

 armature, and the residual magnetism of the electro-magnet cores excites at 

 first weak currents, which pass into the electro-magnet coils, increasing the 

 magnetism of the core and inducing still stronger currents in the armature 

 wire, to the limit of magnetic saturation of the iron cores of the electro- 

 magnets. 



The current thus generated in the machine is sent into the wire or cable 

 leading to the fuse by the opening of a shunt key. The fuse offers a great 

 increase in its resistance at some point, by the interposition of a badly-con- 

 ducting substance ; the consequent action is that the piece of bad conductor 

 is highly heated, causing ignition of the explosive substance contained in the 

 fuse. 



The coils, whether of armature or electro-magnets, of the quantity exploder 

 are wound with wire of large diameter to a total resistance of 8 to 10 units in 

 about 2,000 windings ; electric currents possessing great heating power, but of 

 low intensity, are therefore generated by this machine. 



39. Dynamo-electric exploder for high tension fuses, also called spark 

 fuses (intensity). 



The construction is similar to the above, but this exploder has its coils, 

 both of the armature and the electro-magnets, wound with fine wire to a total 

 resistance of 2,000 to 2,500 Siemens' units, in about 17,000 windings. Upon 

 c? using the armature to revolve, currents are generated of great intensity, 

 und passed by the automatic action of the machine into the wire or cable 

 leading to the fuse, when an electrical spark passing between the separated 

 conductors in the fuse inflames the explosive priming. 



40. Case of electric cable samples. 



41. Ditto ditto. 



42. Ditto ditto. 



1576ab. Wheat stone's Improved Automatic Telegraph 

 System. Receiver and transmitter. 



The British Telegraph Manufactory, Limited* 



Sounder. 



The British Telegraph Manufactory, Limited^ 



Wheatstone's Cryptograph. 



The British Telegraph Manufactory, Limited* 



