their reproduction is the wonderful feature of the whole performance.
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, stationed near the center. After the band had played a selection from some popular opera, we examined their power of reproduction 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 adjustment, the most of them 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 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 furnish 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 sounds 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-
