254 



PLEASANT WA YS IN SCIENCE. 



of this instrument is exceedingly simple. Its essential parts 

 are shown in Fig. 7 ; H is the handle, H b the lever of the 

 manipulator at the station A. The manipulator is shown in 

 the position for receiving a message from the station B along 

 the wire w. The handle H' of the manipulator at the station 

 B is shown depressed, making connection at a' with the wire 

 from the battery N' p'. Thus a current passes through the 

 handle to ^, along the wire to c and through b to the coil of 

 the temporary magnet M, after circling which it passes to the 

 earth at e and so by E' to the negative pole N'. The passage 

 of this current magnetizes M, which draws down the armature 

 vi. Thus the lever /, pulled down on this side, presses up- 



FIG. 7. 



wards the pointed style s against a strip of paper / which is 

 steadily rolled off from the wheel w so long as a message is 

 being received. (The mechanism for this purpose is not 

 indicated in Fig. 7.) Thus, so long as the operator at B 

 holds down the handle H', the style s marks the moving 

 strip of paper, the spring r, under the lever s /, drawing the 

 style away so soon as the current ceases to flow and the 

 magnet to act. If he simply depresses the handle for an 

 instant, a dot is marked ; if longer, a dash ; and by various 

 combinations of dots and dashes all the letters, numerals, etc., 

 are indicated. When the operator at B has completed his 

 message, the handle H' being raised by the spring under it 

 (to the position in which H is shown , a message can be 

 received at B- 



