722 MORSE'S TELEGRAPH. 



a drum not shown in the figure, from which it is rolled 

 off as required. 



The paper being set in motion, and the current trans- 

 mitted through the electro-magnet, the armature s will 

 be attracted, and the point of the screw s is pressed 

 against the moving paper. The upper one of the two 

 rollers has a small groove around it, and as the point 

 presses the paper into this groove an indentation is 

 produced, the leogth of which depends on the time 

 during which the point is in contact with the paper. 

 If the current is interrupted an instant after it was 

 closed a dot (-) is produced, otherwise a dash ( ). 

 By varying the length of time during which the circuit 

 is open or closed, dots or dashes, or any required com- 

 bination of them may be produced at a distant station, 

 and it is only necessary to give definite meanings to 

 these combinations in order to be able to represent by 

 them the letters of the alphabet. The telegraphic 

 alphabet now universally used in connection with 

 Morse's printing telegraph is the following : 



The dots and dashes which together form the same 

 letter are separated by small intervals, the letters by 

 larger intervals, and the single words by still larger 

 ones. 



