178 



SECTION 6. SOUND. 



WEST GALLERY, UPPER FLOOR, ROOM ,' 



I.SOURCES. 



688. Apparatus used by M. Rijke to cause a tube to emit 

 sounds when wire gauze placed in its interior is heated. 



Prof. Dr. P. L. Rijke, Ley den. 



689. Whistles for .producing shrill notes, within and beyond 

 the limits of ordinary audition. Francis Galton, F.R.S. 



These whistles were designed for testing the limits of the power of men and 

 animals of hearing very shrill notes. The plugs that close the whistles can 

 be screwed up and down, and the length of the whistle can be ascertained 

 by the attached graduations, whence the number of vibrations per second 

 may be calculated. The whistles are of three forms : (1) a small cylindrical 

 tube, which gives a pure note, but of small power ; (2) a flat, wide and narrow 

 whistle, of which the plug is a broad thin plate of metal ; (3) an instrument 

 which is externally a cjdinder of 2 inches in diameter, but of which the 

 effective part is merely an annulus ; the plug of this is a cylindrical sheet of 

 brass ; it gives a powerful note, but not a pure one. 



690. Brass Tube to sound the constant proper tone of the 

 mouth, characterising the vocal sound. 



Prof. Donders, Utrecht. 



This consists of a brass tube terminating in a broad slit at one end and at 

 the other end in an india-rubber tube to be placed, on a blower (" souffleur "). 

 (Bonders.) The blast, directed by the slit on the borders of the lips, sounds 

 during the time a vocal sound is sung in different tones, the constant 

 proper tone of the mouth characterising the vocal sound. (Compare Bonders, 

 Uber die Natur der Vocale,.Holl. Beit, zur Nat. u. Heilk. 1846.) 



691. Set of Vowel Forks and Resonance Globes. 



Frederick Guthrie. 



692. Set of Organ Pipes. Frederick Guthrie. 



693. Set of Tuning Porks. Frederick Guthrie. 



926o. Acoustical Instrument, illustrating harmony and 

 discord. S. F. Pichler. 



This instrument is constructed to demonstrate the relations between 

 musical sounds. By its means, harmony and discord, gravity and acuteness 

 of pitch, beats, waves, and amplitude of notes, may be rendered visible as well 

 as audible. 



