S/X WILLIAM SIEMENS, F.K.S. 7 



or the other could be heard at every point of the line. By this 

 arrangement collisions of trains were rendered almost impossible. 



Another instance worth notice was the town telegraph of 

 Berlin, which combined all the police and fire stations in such a 

 manner that the alarm of fire was spread in an instant through 

 the district ; so that the director might communicate from the 

 central office, at his pleasure, either to one station only or to a 

 whole group collectively ; all this was accomplished by one 

 circular line of wire. 



The printing instrument (or secretary) might or might not be 

 joined to the pointer instrument just described. Its function was 

 to print the messages given and received in common type upon 

 strips of paper, thus giving a duplicated record of the communica- 

 tions at both ends of the line, and avoiding all possibility of 

 error. 



It would at first sight appear doubtful whether it would be 

 practically possible to ensure the simultaneous movement of the 

 rotating hands, or pointers, besides working alarums, and printing 

 mechanism, all by the same wire and battery. These doubts 

 must, however, disappear on inquiring into the peculiar principle 

 of action which had been adopted. Unlike other telegraphs, 

 where the communicating instrument was worked by hand, or clock- 

 work, or where the receiving instrument was assisted by such, the 

 instruments in question were purely electrical machines, in which 

 reciprocating motion was produced by the independent action of 

 the instrument in alternately breaking and restoring the galvanic 

 circuit. Between the poles of a horse-shoe electro-magnet, an 

 armature was placed transversely upon a spindle parallel to the 

 shanks of the magnet, so that the attraction of the armature by 

 the electro-magnet produced an angular motion of the former. A 

 spring was attached to the armature, which caused it to fall into its 

 distant position whenever the magnetism ceased, by the break of 

 the circuit The armature carried with it a lever, to the end of 

 which a ratchet was attached, which moved a ratchet-wheel 

 through the breadth of one tooth for every oscillation of the 

 armature. The spindle of this ratchet-wheel carried the hand 

 or pointer en the dial face, and the number of its teeth corre 

 sponded with the number of keys around the dial. The working 

 lever carried, also, two insulated projections with which it struck, 



