138 Dr. Young's Experiments and Inquiries 



tinguished during any part of the continuance of the sound. 

 This demonstrates, that the secondary notes do not depend 

 upon any interference of the vibrations of the air with each 

 other, nor upon any sympathetic agitation of auditory fibres, 

 nor upon any effect of reflected sound upon the chord, but 

 merely upon its initial figure and motion. If it were supposed 

 that the chord, when inflected into right lines, resolved itself 

 necessarily into a number of secondary vibrations, according to 

 some curves which, when properly combined, would approxi- 

 mate to the figure given, the supposition would indeed in some 

 respects correspond with the phasnomenon related; as the coef- 

 ficients of all the curves supposed to end at the angle of inflec- 

 tion would vanish. But, whether we trace the constituent curves 

 of such a figure through the various stages of their vibrations, 

 or whether we follow the more compendious method of Euler 

 to the same purpose, the figures resulting from this series of 

 vibrations are in fact so simple, that it seems inconceivable how 

 the ear should deduce the complicated idea of a number of 

 heterogeneous vibrations, from a motion of the particles of air 

 which must be extremely regular, and almost uniform ; an uni- 

 formity which, when proper precautions are taken, is not con- 

 tradicted by examining the motion of the chord with the assist- 

 ance of a powerful magnifier. This difficulty occurred very 

 strongly to Euler ; and De la Grange even suspects some 

 fallacy in the experiment, and that a musical ear judges from 

 previous association. But, besides that these sounds are disco- 

 verable to an ear destitute of such associations, and, when the 

 sound is produced by two strings in imperfect unison, may be 

 verified by counting the number of their beats, the experi'- 

 ment already related is an undeniable proof that no fallacy 



