ACOUSTICAL INSTRUMENTS. 99 



metres, was traversed in 9-25 seconds, giving 1,435 metres per 

 second as the velocity in water at 8 C. 



In an Iron Pipe it was found by Biot to be 3,250 metres per 

 second. 



In Wood its transmission was ingeniously demonstrated by 

 Wheatstone. His telephone consisted of long rods of light pine 

 affixed in a lower room to various instruments. On a resonant 

 body being attached to the upper end of the rods in an upper 

 chamber, not only the pitch, but even the quality, of the various 

 tones was distinctly reproduced. 



The transmitting power of wood is daily used in the stethoscope 

 for medical purposes. 



Under this heading may be named the reinforcement produced 

 by bells, or trumpet-like expansions seen at the lower end of many 

 instruments \ by the speaking trumpet on the voice ; the effects of 

 consonance in soundboards ; in the bamboo harmonicon already 

 named; and in the hollow vessels said to have been used in 

 Greek theatres to increase the resonance of the actor's voice. In 

 the measured and monotonic recitation of Greek tragedy, no 

 doubt the result may have been favourable; though in the 

 inflected diversities of modern speaking it would have had rather 

 an opposite effect. The importance of consonance in securing 

 greater audibility can, however, be traced in the practice of 

 intoning as used in our large cathedrals. 



The Bamboo Harmonicon, termed a Marimba, or Balafo, is 

 furnished with a dried calabash or gourd beneath each resonating 

 plate. A small hole is pierced into the cavity of the gourd and 

 turned upwards towards the under surface of the plate. Around 

 this hole is cemented a smaller gourd, with the two extremities 

 removed, so as to form a cornet or receiver, evidently intended 

 to direct a larger number of vibrations into the consonant 

 cavity. 



The determination and measurement of musical sound has, from 

 the earliest times, been studied with success. Indeed, in the 



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