MAGNETIC TELEGRAPH. 49 



riety of applications to the arts, and the purposes 

 of man. 



Come with me now into a telegraph office, and 

 let us see what we find there. If the line be a 

 short one say thirty or forty miles you will see 

 but one of Henry's spools, fixed to a table, 

 having a piece of iron called an "armature," 

 capable of vibrating in front of its poles, and so 

 arranged that when the "spool-magnet" attracts 

 it, it will vibrate and strike a sounding-bar of 

 sonorous metal, which gives out distinctly the 

 sound of the tap. The "spool" is wound spirally 

 in layers with several hundred feet of fine copper 

 wire, covered with silk, in the manner specified 

 by Henry in " Sillimaris Journal." At the 

 other end of the line is a battery, composed of a 

 number of cells in series, called by Henry for 

 distinction an "intensity battery; " and the wire 

 circuit is supplied with a simple device, so that it 

 may be opened or closed by the operator's finger. 

 When he closes it, a current of electricity 

 flows from the "intensity battery" along the 

 wire, and around the coil of the ' ' intensity mag- 

 net," and the armature strikes the sounder and 

 gives the signal. The listener hears it; and as the 

 order of the taps progresses in accordance with 

 a pre-arranged artificial code, to express the let- 

 ters of the alphabet by combinations of succes- 

 sive taps just as the old visible signals were ar- 



