682 Dynamic Theory. 



CHAPTER LXV. 



THE INTERNAL SENSES. 



By the Harmonic process of Telegraphy, invented by Elisha Gray of 

 Chicago, 1873, at least eight communications can be sent at once. "The 

 transmitting apparatus consists of a number of steel reeds, each tuned 

 to vibrate at a different rate, corresponding to some one note of the mu- 

 sical scale. One end of each reed is rigidly fixed, while the other is 

 left free to vibrate by the alternate action of two electro-magnets, a lo- 

 cal battery, and an automatic device for alternating the current of the 

 battery between the two magnets at each vibration, so that the move- 

 ment of the reed is rendered continuous as long as the current passes ; 

 but the rate of vibration of each individual reed must correspond rig- 

 idly with the note to which it is tuned. If a line is to be equipped for 

 eight simultaneous transmissions, the main battery is divided into eight 

 equal sections, which are so arranged as to be thrown alternately on and 

 off the line at each vibration of the reed connected with that section. 

 If, then, the first reed be tuned on fundamental C, it will make 128 vi- 

 brations per second, and by depressing the corresponding transmitting 

 key, the particular section of the battery will be thrown in and out of 

 the main circuit 128 times per second, and a corresponding number of 

 electric waves will pass through the linje. The next reed may be tuned 

 on D, which, in like manner, will produce 144 waves per second, and 

 so of the remaining six. At the receiving station a series of eight an- 

 alyzers are placed in the circuit, the current passing through them all in 

 succession. Each analyzer consists of an electro-magnet, whose arma- 

 ture is fixed at one end and free at the other, and so arranged as to form 

 a vibrating tongue or reed, which is tuned to the same note as the trans- 

 mitting reed to which it is intended that it shall respond. When the 

 transmitted vibrations pass through a series of analyzers, each arma- 

 ture takes up its own set of vibrations, rejecting all the others, and con- 

 sequently gives forth its own musical notes. The sound is greatly in- 

 creased and intensified by mounting each analyzer upon a sounding box, 

 or resonator, adjusted to its own note. The several transmitting keys 

 break up the continuous tone into the dots and dashes of the telegraphic 

 alphabet, which may be read from the sound of the analyzer as readily 

 as from an ordinary sounder. Indeed, by the addition of a secondary 

 spring attached to the analyzer, having a slower rate of vibration, it 

 may be readily made to operate the usual Morse sounder by opening and 

 closing the circuit. No difficulty is found in transmitting eight simul- 

 taneous communications over one wire to a distance of several hundred 



