198 SEC. 6. SOUND. 



780. Mono chord, which affords the means of measuring 

 the 200th part of an inch, with a view to ascertaining the number 

 of vibrations given by that length of string. 



781. Apparatus for producing musical sounds, mainly con- 

 sisting of notched wheels of different diameters, which, being 

 set in motion at a given speed, and duly prepared pieces of card- 

 board brought in contact with their teeth, produce the notes of 

 the common chord ; the number of notches in the wheels corre- 

 sponding with that of the vibrations required to produce those 

 notes. 



782. Apparatus for showing the relative positions of the 

 vibrations of two strings or tubes under the operation of altering 

 the ratios; the strings first tuned to coincidence as unisons, 

 the ratios then altered by lowering the pitch of one of the strings, 

 as from 81 lo 80, 82 to 80, or any other numbers within the 

 scale of the apparatus. 



783. Set of Flute Pipes, w T ith bellows attached, some of 

 which have too high sounds to be heard singly, but which together 

 give the resultant tone. 



784. Large Set of Coloured Diagrams for illustrating 

 lectures on sound. 



784a. Collection of Tuning Forks. 



One tuned to Handel pitch. 

 Two in a box. 

 Two normal diapason. 

 One tuned to Big Ben. 

 One C. 528. 



784b. Paper printed by J. H. Griesbach to Handel's 

 pitch, and one to the true diapason. 



785. Collection of Acoustic Apparatus. 



George Appunn and Sons, Hanau. 



785a. Three Acoustic Wind-Chest Tables. These three 

 tables are required for placing all the following apparatus : 



George Appunn and Sons. 



I Overtone Apparatus, consisting of 64 lingual tones, the first 64 part 



-2 



tones of the fundamental or key tone (primary sound) C =32 vibrations in 

 a second with reed pipes. 



