Mr. Wheatstone on Resonancet 177 



at a short distance from the embouchure of a flute, provided, of 

 course, that the columns of air, both in the flageolet and the flutQ> 

 be capable of producing the sam^ note, ff 



§ 3. A cylindric or prismatic column of air, in a tube open at 

 both ends, may vibrate not only in its entire length, but also in any 

 number of aliquot parts, and in all cases the number of vibrations 

 is inversely as the length of a single vibrating part. As a column 

 of air is capable of reciprocating every sound which, according to 

 its different modes of vibration, it is itself capable of producing ; 

 supposing l=:;Ci to represent the lowest sound of the tube, it will, 

 without any change in its length, reciprocate sounds whose relations 

 _^^ 1 2 3 4 5 6 7 8 

 "® Ci, C^, G2, C^ E3, G3, BbS C*, &c. 



The harmonic subdivisions of a column of air in a tube closed at 

 one end are different ; a semi-vibrating part always exists near the 

 closed end, but between two nodes, or a node and the open end, 

 complete vibrating parts, as in an open tube, exist. The funda- 

 mental sound above mentioned, of an open tube, is given by. a tube 

 closed at one end, of one-half its length ; the series, corresponding 

 with the subdivisions, compared with the above, is ^^ ^, g. 



7 Q 



g, 3 Jj4 ^^ and these sounds it can consequently reciprocate. 



§ 4. Any one among several simultaneous sounds may be ren- 

 dered separately audible. Thus, if two vibrating tuning-forks, dif- 

 fering in pitch, be held over a closed tube, furnished with a move- 

 able piston, either sound may be made to predominate by altering 

 the piston, so as to enable the column of air to reciprocate the 

 sound required. The same result may be obtained by selecting 

 two bottles (which may be tuned with water), each corresponding 

 to the sound of a different timing-fork ; on bringing both tuning- 

 forks to the mouth of each bottle alternately, in each case that 

 sound only will be heard which is reciprocated by the unisonant 

 bottle.* 



• Had Sir Isaac Newton been acquainted with these, or with any similar facta* 

 he might have illustrated his theory of the reflection of colours by an experimental, 

 instead of a suppositious analogy with the reciprocation of sounds. As the passage 

 in which this comparison is made, is remarkable, I will quote it. " If light be con- 

 ** sidered without respect to any hypothesis, I can as easily conceive that the several 

 " parts of a shining body may emit rays of ditferent colours, and other qualities, of 

 " all which light is constituted, as that the several pipes of an organ inspired all at 

 " once, or all the variety of sounding bodies in the world together, should produce 

 " sounds of several tones, and propagate them through the air, confusedly inter- 

 " mixed. And, if there were any natural bodies that would reflect sounds of one 

 " tone, and stifle or transmit those of another, then, as the echo of a confused aggre- 

 ** gate of all tones would be that particular tone, which the echoiog body is di6pose4 



JAN.^MARCH, 1828. N 



