76 THE POPULAR SCIENCE MONTHLY. 



their reproduction is the wonderful feature of the whole per- 

 formance. 



I was once present by invitation of Mr. Edison to witness a. 

 phonograph test in his laboratory at Orange, N. J., and by way of 

 illustrating the power of reproduction of that instrument will 

 state the result as witnessed by me. Some fifteen or twenty 

 phonographs were placed in a semicircle in the room, all their 

 cylinders running, and a band of music, including a piano, sta- 

 tioned near the center. After the band had played a selection 

 from some popular opera, we examined their power of reproduc- 

 tion by putting on the ear tubes, and, beginning at one end of the- 

 row in company with Mr. Edison, tried each phonograph. 



It was found that while some reproduced the music not as 

 loud or as clearly as desired, owing probably to imperfect adjust- 

 ment, the most of them t were remarkable for their loudness of 

 sound, and so clear and perfect that the sound of each instrument 

 such as the piano, cornet, etc., could be distinguished separately. 

 These cylinders were taken off and, after being labeled, filed away 

 for future use. In the phonograph Mr. Edison has given the- 

 world a most useful and valuable invention ; for, beyond the fact 

 of its commercial value, it is a most important educator in the 

 science of acoustics, as we have attempted to point out. 



Many illustrations may be found in electrical inventions where- 

 the vibrating construction of sound is taken advantage of for 

 instance, the musical telephones of Prof. Gray and Edison, and 

 such ingenious inventions as the harmonic telegraph of Gray r 

 and the railway induction telegraph of Phelps and Edison. All 

 these and many others employ the vibrating effect of sound to- 

 accomplish the desired results. 



If we look for more common illustrations we may easily find 

 them about us, such as the circuit breaker in the medical battery. 

 By manipulating the adjusting screw, changing the number of 

 vibrations per second, a variety of notes can be produced, from a, 

 a low rattle to a high, fine tone. The ordinary " buzzer " now 

 common in business houses, which is largely taking the place of 

 the electric bell, gives forth a note more or less musical according- 

 to the number of vibrations per second to which it is adjusted. 

 The wings of the humming bird as well as those of insects fur- 

 nish further examples of musical notes (not always welcome) by 

 the rapid action of their wings against the air. 



It will be observed, as this question is studied, that sound 

 vibrations to be musical must be regular, otherwise they become 

 simply noise. Prof. Tyndall, in his admirable work on sound,, 

 referring to this part of the subject, says that " a musical sound 

 flows smoothly and without irregularity, and this is secured by 

 rendering the impulses received by the tympanic membrane per- 



