17G Mr. Wheatstone on jResonance, 



flute*. The sound will be found greatly to decrease by closing or 

 opening another aperture ; for the alteration of the length of the 

 column of air in such case renders it no longer proper to reciprocate 

 perfectly the sound of the fork. This experiment may be easily 

 tried on a concert flute, with a C tuning-fork. To ensure success, 

 it is necessary to remark, that when a flute is blown into with the 

 mouth, the under lip partly covering the embouchure, renders the 

 sound about a semitone flatter than the sound when the embouchure 

 is entirely uncovered ; and as the latter must be unison to that of 

 the tuning-fork, it is necessary, in most cases, to finger the flute for 

 B when a C tuning-fork is employed. 



A similar effect may be produced by substituting, for the column 

 of air in the flute, the alterable volume of air contained within the 

 cavity of the mouth. I have found the sounds of tuning-forks reci- 

 procated most intensely by placing the tongue, &c. in the position 

 for the nasal continuous sound of ng (in song), and then altering 

 the aperture of the lips until the loudest sound is obtained. 



§ 2. A column of air may also reciprocate a sound originally 

 produced by a wind instrument, as the following experiment will 

 show. Place two concert flutes on a table, parallel to, and at a 

 short distance from each other ; on the one which is nearer, sound 

 C sharp (all the lateral apertures being open), and draw out the 

 tube of the second flute, so that it shall be about a semitone flatter, 

 to make it equivalent to the flattening of the first flute by the partial 

 closing of the embouchure by the lip ; a material difference will then 

 be distinguished in the intensity of the tone by alternately closing 

 and opening the first hole of the more distant instrument, thereby 

 rendering it incapable or capable of reciprocating the original 

 sound. That this effect is occasioned solely by the transmission of 

 the sonorous undulations, and not by any wind actually blown into 

 the second flute, is evident from the difference being in intensity and 

 not in pitchf. 



This experiment may be varied by placing the fipple of a flageolet 



* Dr. Savart has observed a similar effect by sounding a bell before a large tube 

 inclosing an unisonant column of air. Recherches sur les Ftbrations de I'Jtr. An- 

 nales de Chimie, torn. 24. 



t Lord Bacon may be said to have anticipated this experiment in the following 

 passage in his Sylva Sylvarum : — " The experiments of sympathy may perhaps be 

 transferred from stringed instruments to others; as, if there were two bells in unison 

 in one steeple, to try whether striking the one would move the other, more than if 

 it were a different chord ; and so in pipes, of equal bore and sound, to try whether a 

 light straw or feather would move in one pipe, when the other is blown in unison 

 with it," Art, Phonics, (Sec/, xxi. On the Sympathy or Antipathy of Sounds with 

 one another. 



