576 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



c each of which may be put in contact with the corresponding screw 

 5 and d below it. 



In the position of rest, or while waiting, the spring / keeps the 

 screw c out of contact with d, and then the screw a touches I. Tins 

 is the position for receiving, for as soon as a current thrown into the 

 line reaches the station it passes from L into the lever of the manipu- 



FIG. H71. Morse's manipulator. 



lator and by a and b into the indicator. If on the contrary, a message 

 is to be despatched, that is, a series of discontinuous currents, the 

 clerk has only to press upon the wooden handle K of the lever, so as 

 to overcome its resistance to separate a from contact with b, and to 

 bring c on the contrary in contact with d. As soon as this last contact 

 is made a current passes from P into the manipulator and from thence 



FIG. 372. Another pattern of Morse's manipulator. 



into the line wire L. The current sent is interrupted when the contact 

 ceases. Nothing is more simple, as we see, than the Morse manipu- 

 lator of which Figs. 371 and 372 represent two patterns. 



The indicator is not much more complicated. It consists of an 

 electro-magnet whose magnetising coil forms on one side a continua- 

 tion of the line-wire, and on the other passes to earth. The series of 



