596 THE A P PLICA T10NS OF PH YSICA L FORCES. [BOOK v. 



By reason of capillary attraction the ink is prevented from passing 

 through those apertures. Two electro-magnetic coils, one on either 

 side of the ink-reservoir, actuate two needles, adjusted so as to be 

 depressed by the action of the current, and dipping into the reservoir 

 pass into the holes and carry a sniali quantity of ink with them, 

 which is transferred to the paper ; thus the action of the current 

 in depressing either needle is printed as a "dot" or "dash" ac- 

 cording as the respective needle is depressed, without friction or 

 mechanical resistance. The electro-magnetic coils are so adjusted 

 that only the respective needles are acted upon by the currents as 

 they How from the positive or negative poles -of the battery. The 

 automatic printing in the dot and dash character is shown at Fig. 

 389. Capillary attraction is here again made use of, only in a 

 different manner. A small inking disc of metal mounted upon a 

 delicately poised axle, capable of a slight angular oscillation in 

 a lateral direction, according as it is influenced by the to-and-fro 



,*""' "E" "o" "G" "E"E"S""S" "o" "F"' 

 T"H"E T"E"L""E " "E" T "" "H" 



FIG. 889. Automatic " dot" and "dash " message, piinted from the perforated paper ribbon. 



motion of a permanent magnetic armature when acted upon by the 

 alternate currents passed into the line from the " transmitter," is 

 caused to rotate rapidly by the same mechanical means that ad- 

 vances the paper ribbon forward. This little rotating inking disc 

 is placed close to the surface of the paper ribbon, so that on 

 receiving a lateral motion in one direction, its edge is pressed 

 against the paper and removed from it by an opposite motion ; in 

 its normal position it is free from contact with the paper ribbon. 

 Thus dots gr dashes are marked on the paper, according to the 

 length of time, either momentary or of a sensible duration, of 

 the inking contact, the reverse movement of the disc producing 

 the spacing between the printed marks ; as the spacings between the 

 signals are automatically regular, the " dash " is the result of the 

 retention of the inking disc upon the paper for double the time of 

 the " dot," by reason of the grouping of the perforations to form 

 the " dash " giving a longer duration without a reversal of the 



