RECENT ADVANCES IN TELEGRAPHY. 79 



least confusion ensued from the crowding together, for a considerable 

 distance, of the multitude of intricately-related vibrations in a rod 

 having a section of but one square inch. 



Prof. Helmholtz's apparatus consisted of a number of electro-mag- 

 nets acting on tuning-forks pitched to particular notes. His object 

 was so to combine those notes as to demonstrate the formation of 

 certain harmonious sounds ; but the object of the telegraph-inventors 

 is the reverse of that, namely, to transmit them in the form of electric 

 vibrations to a distance, and then as in Wheatstone's experiment 

 to sift them out again to separate instruments. In most of the plans 

 so far made public, a fixed steel bar takes the place of the tuning-fork, 

 and therefore of the armature as well. When attracted by the mag- 

 net, on making a signal, it is of course set vibrating ; and, at every 

 forward vibratory movement, it closes the circuit and transmits an 

 electric impulse. A number of such magnets, their sonorous arma- 

 tures sending each a different number of pulsations in a second, may 

 be working away at once, and the corresponding instruments at the 

 other end of the line will be acted on only by those which suit their 

 times of vibration. In other words, of the total number of electric 

 charges sent into the line, only those will act on any particular mag- 

 net at the receiving end which suffice to cause in its armature the 

 number of vibrations per second to which it was set. This, of course, 

 is the same number which was sent by the transmitting instrument 

 of the same pair. Practically, the different tones are not reproduced 

 quite unmixed, every armature being capable of responding though 

 in a less degree, to other notes than its own ; so that the effect on 

 the ear, at one of the receiving magnets, is like that of a number of 

 persons talking together in different keys : some quite loudly ; some 

 in a lower tone ; others in a whisper. To remedy this, different forms 

 of resonators are being tried, adapted to swell the special sounds that 

 should be heard. 



The " electromotograph," described in connection with chemical 

 telegraphs, is intended, by its inventor, to be used with some form of" 

 this acoustic system. Mr. Gray, of Chicago, another well-known tele- 

 graph-inventor, is also understood to have made considerable prog- 

 ress in this direction. 



It is matter of reasonable pride to find, at the commencement of 

 our second century, the names of Americans so prominently connected 

 with all the great improvements in the art which owes so much to 

 the labors of Morse and Henry. 



