160 SEC. 6. SOUND. 



normal forms a moderate angle with the rotatory axis, is peculiarly adapted 

 to change the reflected image of the sonorous flame into a beautiful elliptical 

 crown. 



73 la. Barlow's Logograph, an instrument for recording 

 pneumatic effects of speech, being questions to consonants, as well 

 as records. W. H. Barlow, F.R.S. 



731b. Apparatus for Synthesis of Vowel Sounds. 



Prof. Clifton, F.R.S. 



732. Apparatus for the projection on the screen of the 

 curves produced by the combination of rectangular vibrations. 



Yeates $ Sons. 



IV. INTERFERENCE. 



733. Apparatus for demonstrating, by the aid of flames, the 

 interference of two musical sounds. 



The Director of the Physical Laboratory of the University 

 of Groningen. 



The apparatus consists of two curved movable cross tubes, narrowed at 

 one end ; their narrow openings, being near each other, are tightly fixed in a 

 longer tube, also ending in a narrow opening ; this is placed close to a strong 

 flame, and also a very small flame, which can be seen in a rotating mirror. A 

 little movable burner for this small flame is attached to the apparatus. When 

 a sound-wave proceeds from the opening of the instrument, the strong flame 

 diminishes abruptly in length and begins to roar, while the small flame rapidly 

 vibrates, its motion being visible in the rotating mirror. The open ends of the 

 two curved tubes can be placed before the mouths of two unisonant organ 

 pipes, or above two different segments of a vibrating plate. When only one 

 of the pipes is sounded, the flames show the vibrations, but, when both pipes 

 are sounded, there is no agitation of the flames, the two sound-waves counter- 

 acting each other. When the two openings are above segments of the plate, 

 which are in the same phase of vibration, the flame is agitated, but, when they 

 are above segments in the opposite phase, the flame remains at rest. 



734. Apparatus, of simple character, foi\ demonstrating by the 

 aid of flames the interference of two musical sounds. 



The Director of the Physical Laboratory of the University 

 of Groningen. 



This apparatus is designed for the same purpose us 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. 



The Director of the Physical Laboratory of the University 

 of Groningen. 



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. 



