THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



NOVEMBER 1872. 



XXXIX. On a Method of detecting the Phases of Vibration in the 

 Air surrounding a Sounding Body^ and thereby measuring di- 

 rectly in the vibrating air the lengths of its Waves and exploring 

 the form of its Wave-surface. By Alfred M. Mayer, Ph.D., 

 Member of the National Academy of Sciences, Professor of 

 Physics in the Stevens Institute of Technology, Hoboken, N. /., 

 United States'^. 



Preliminary Considerations. 



THE curve A, B^, B''', &c. is the well-known symbolic repre- 

 sentation of the dynamic condition of the air^ at a given 

 instant, when traversed by simple sonorous vibrations. The 

 portions of the curve above the axis X represent the lengths 

 and manner of the aerial condensations, while the flexures below 



the axis represent the rarefactions ; therefore similar points in 

 the flexures above the axis, or similar points in the flexures below 

 the axis, represent like phases of vibratory motion. Imagine 

 these conditions of the air produced by a body vibrating at A ; 



* Communicated by the Author. 

 Phil Mag, S. 4. Vol. 44. No. 294. Nov. 1872. Y 



