190 SEC. 6. SOUND. 



734, Apparatus, of simple character, for demonstrating by the 

 aid of flames the interference of two musical sounds. 



Prof. Dr. R. A. Mees, Director of the Physical Labora- 

 tory of the University of Groidngen. 



This apparatus is designed for the same purpose as that last described, but 

 is of more simple construction. 



735. Quincke's Interference Tube, to demonstrate by the 

 action of a flame the diminution and increase of sound by inter- 

 ference. 



Prof. Dr. R. A. Mees, Director of the Physical Labora- 

 tory of the University of Groningcn. 



This apparatus is furnished with a supplementary brass tube having a 

 narrow opening. It can be used with the same flames as those provided for 

 the instruments last described. 



735a. Interference Apparatus, by Jamin. 



M. J. Duboscq, Paris. 



735b. Interference Apparatus. Prof. W. F. Barrett. 



This is a circular modification of the usual trombone apparatus. When 

 used with a pitch pipe, the extinction of the sound is made evident to a large 

 audience, the two resonant columns being rendered in opposite phases by 

 adjustment of the movable circular tube Phil. Mag., Aug. 1874. 



V. ABSORPTION, REFLECTION, AND REFRACTION. 



736. Apparatus for showing Approach caused by 

 Vibration. Frederick Guthrie. 



A suspended card or mass of cotton wool, or an air ball floating in water, 

 approaches a resonant fork ; and the latter, when free to move, is also urged 

 towards neighbouring matter. 



737. Apparatus for showing the Expansion of Gases 

 by Sound. Frederick Guthrie. 



One prong of a tuning fork is enclosed, air-tight, in a glass tube provided 

 with a capillary exit tube, in which water stands at a certain height. On 

 bowing the free prong of the fork the water level is seen to fall about a quarter 

 of an inch. 



738. Apparatus for the Reflection of Sound by heated 

 air and vapours. Prof* Tyndall, F.R.S. 



Sound of high pitch from a vibrating reed is passed through a long rectan- 

 gular chamber, and caused to agitate a sensitive flame. Air, saturated with the 

 vapour of a volatile liquid, is gently driven through six narrow openings into 

 the chamber, at right angles to the direction of the sound. The atmosphere 

 within the chamber is thus immediately rendered heterogeneous, and the 

 sound waves being reflected, the agitated flame is rapidly stilled. The removal 

 of the heterogeneous medium instantly restores the flame to its former 

 agitation. 



