1839.] 



Telegraphic Signals by induced electricity. 



m 



connected with the source of electrical excitement. As I am now writ- 

 ing for popular readers I may be pardoned by the adept for illustrating 

 this interesting fact by an explanatory diagram. 



In this diagram, 1 represents the voltaic couple; z zinc; and c 

 copper ; 2 shews the magnetic needle on its stand in the magnetic 

 meridian, with the surrounding coil of wire, with its terminations a 

 and b. In the first the wires cross, or that from z proceeds to b, that 

 from c to a, and the deflection accordingly is from north to west. In 

 the second the wire from z proceeds to a } that from c to b, and deflec- 

 tion of the needle is from north to east. 



Thus with two wires we can obtain two signals only, but one wire 

 may belong, or be common to any number of galvanometers, so that 

 from three wires we can obtain four signals ; from four wires six signals ; 

 from five wires eight signals ; from six wires ten signals ; eight wires 

 fourteen signals ; ten wires eighteen signals ; twelve wires twenty-two 

 signals ; fourteen wires twenty-six signals, or the alphabet. 



In the following diagram six galvanometers are represented connected 

 with seven wires, one being common to all. The six wires run any 

 distance in a bundle, and are best insulated by silk or resin from each 

 other. The ends of the wires then proceed to little cisterns of mercury, 

 disposed in a circle. From the centre of the circle a moveable wire 

 proceeds as a radius, which may be moved to any of the cisterns 1, 2, 

 3, 4, 5, 6. To this centre proceeds one of the poles (z) of the voltaic 

 couple-^and to the termination of the common wire, proceeds the 

 second pole of the couple c. 



