CHAP. III.] 



ELECTRIC TELEGRAPHY. 



549 



At first this illustrious electrician employed five galvanometers, 

 which required, including the return line, six wires. The five wires 

 were disposed in this way. They were ranged in front of and 

 along the central line of a lozenge-shaped frame, and the corresponding 

 galvanometers were placed behind the frame opposite, the ends of each 

 wire. When a current was made, by the manipulator, to pass through 

 two of the five galvanometers in an opposite direction, the two needles 

 deviated at the same time, placing themselves diagonally and pointing 

 to one of the letteis inscribed on the frame. For example, the needles 



FIG 349. Wheatstone's five-needle telegraph. 



1 and 4 (Fig. 349) have their upper ends directed towards the top of 

 the frame and indicate the letter B ; if the current passed through 

 the same galvanometers, but in opposite directions, the lower ends of 

 the needles would be directed towards the base of the frame and mark 

 the letter Y. When a needle moves alone it indicates one of the ten 

 figures written on the lower edge of the frame. Two similar dials 

 united by five wires give the same indications at the same time 

 when the sender of the message works the manipulator. By pressing 



