178 Mr. Wheatstone on Resonance. 



The phenomenon of a third sound, produced by the coincidences 

 of the vibrations of two consonant sounds, is well known. From 

 what has been premised, it is reasonable to suppose that if a 

 column of air be caused to reciprocate this third sound, or grave 

 harmonic as it is called, and not the two sounds which generate it, 

 it might be heard, uncombined with the two other sounds. But on 

 attempting" this experiment, I was unable, on the following account, 

 to succeed. The third sound is always unity when the ratio of the 

 lowest sounds is reduced to its lowest terms ; thus, with respect to 

 a perfect fifth, 2 : 3, the third sound 1, is an octave below the lower 

 sound, and the grave harmonic .1, of a major third, 4 : 5, is two 

 octaves below the lower sound ; we will suppose this fundamental 

 sound, represented by unity, to be the C, corresponding with the 

 sound of an open tube of four feet, or of a closed tube of two feet : 

 in the first case, the column of air being capable, as explained in § 3, 

 of vibrating in any number of aliquot . parts, not only, the grave 

 harmonic = 1, but the sounds represented by 2 : 3 and 4 ; 5, will 

 also be reciprocated ; and in the latter case, where the subdivisions 

 are as the arithmetical progression 1, 3, 5, 7, 9, 11, &c., one sound 

 of each consonance will be reciprocated, besides the grave sound. 

 The expected result may probably still be obtained by employing 

 columns or volumes of air, whose subdivisions are less regular. 



§ 5. Among the Javanese musical instruments brought to 

 England by the late Sir Stamford Raffles, there is one called the 

 Gender, in which the resonances of unisonant columns of air are 

 employed to augment, I may almost say to render audible, the 

 sounds of vibrating metallic plates. Of these plates there are 

 eleven ; their sounds correspond with the notes of the diatonic 

 scale, deprived of its fourth and seventh, and extend through two 

 octaves. The mode of vibration of the plates is that with two 

 transversal nodal lines ; and they are suspended horizontally by two 

 strings, one passed through two holes in the one nodal line, and 

 the other through similar holes in the other nodal line of each plate. 

 Under each plate is placed an upright bamboo, containing a column 

 of air, of the proper length to reciprocate the lowest sound of the 

 plate. If the aperture of the bamboo be covered with pasteboard, 

 and its corresponding plate be struck, a number of acute sounds 

 only (depending on the more numerous subdivisions of the plate) 



" to reilect ; so, since there are bodies apt to reflect rays of one colour, and stifle or 

 " transmit thoFe of another,! can as easily conceive that those bodies, when illuminated 

 " by a mixture of all colours, must appear of that colour only which they reflect." 

 Pfiilosophical Transactivns, No. 88. 



