4 PROCEEDINGS OF THE AMERICAN ACADEMY 



could hear the unison of the note produced by the rheotome. The 

 intensity of the sound was much increased by placing a wrouglit-iron 

 nail inside the helix. In both these cases, a crackling effect accompa- 

 nied the sound. When the nail was held in the fingers so that no 

 portion of it touched the helix, the crackling effect disappeared, and a 

 pure musical note resulted. 



When the nail was placed inside the helix, between two cylindrical 

 pieces of iron, a loud sound resulted that could be heard all over a large 

 room. The nail seemed to vibrate bodily, striking the cylindrical pieces 

 of metal alternately, and the iron cylinders themselves were violently 

 agitated. 



4. Loud sounds are emitted by pieces of iron and steel when sub- 

 jected to the attraction of an electro-magnet which is placed in cir- 

 cuit with a rheotome. Under such circumstances, the armatures of 

 Morse-sounders and Eelays produce sonorous effects. I have 

 succeeded in rendering the sounds audible to large audiences by 

 interposing a tense membrane between the electro-magnet and its 

 armature. The armature in this case consisted of a piece of clock- 

 spring glued to the membrane. This form of apparatus I have found 

 invaluable in all my experiments. The instrument was connected 

 with a parlor organ, the reeds of which weie so arranged as to open 

 and close the circuit during their vibration. When the organ was 

 played the music was loudly reproduced by the telephonic i-eceiver 

 in a distant room. When chords were played upon the organ, the 

 various notes composing the chords were emitted simultaneously by 

 the armature of the receiver. 



5. rhe simultaneous production of musical notes of different pitch 

 by tlie electric current, was foreseen by me as early as 1870, and 

 demonstrated during the year 1873. Elisha Gray,* of Chicago, and 

 Paul La .Cour,t of Copenhagen, lay claim to the same discovery. 

 The fact that sounds of different pitch can be simultaneously produced 

 upon any part of a telegraphic circuit is of great practical importance ; 

 for the duration of a musical note can be made to signify the dot or 

 dash of the Morse alphabet, and thus a number of telegraphic mes- 

 sages may be sent simultaneously over the same wire without confusion 

 by making signals of a definite pitch for each message. 



6. If the armature of an electro-magnet has a definite rate of oscil- 

 lation of its own, it is thrown bodily into vibration when the interrup- 



* ElUha Gray. Eng. Pat. Spec, No. 974. See " Engineer," March 26, 1876. 

 t Paul la Cour. Telegraphic Journal, Nov. 1, 1875. 



