ACOUSTICAL INSTRUMENTS. 



SOUND, from a physical point of view, may be defined as vibra- 

 tion appreciable to the ear. It appears, at its lower limit, to be 

 continuous with vibration as detectable by common tactile sensa- 

 tion ; hence its exact musical commencement is rather indefinite. 

 It is usually given at thirty-two single or sixteen double vibrations 

 per second. Apparatus for the demonstration of this fact will be 

 noted farther on. Its higher limit is even more variable, owing to 

 physiological differences between different ears ; but 73,000 single 

 or 36,500 double vibrations per second probably represent the 

 highest note ever heard. Two organ pipes are exhibited, the 

 individual sound of which is, for this reason, inaudible, but whose 

 resultant tone is within the limits of hearing. 



The line of demarcation between mere noise and musical sound 

 seems similarly vague. Dr. Haughton has ingeniously shown that 

 the rattling of vehicles over equal-sized stones becomes musical at 

 a definite velocity ; from the confused rattle of a railway train 

 in a tunnel the practised ear can disentangle and, as it were, men- 

 tally sift out grand organ-harmonies ; and a falling plank in the 

 Crystal Palace gives musical notes by periodic re-percussion at 

 equal intervals. On the other side, castanets, tomtoms, side-drums, 

 triangles, cymbals, all instruments of music proper, only give 

 noise similar to the guns added in Russia to Italian music, or the 

 hundred anvils "played on" at the Boston Celebration. Even 



