90 



01^ THE PHYSIOLOGICAL CAUSES OF 



violin bow, plucking it with the finger, or striking it with a 

 pianoforte hammer. The bell-like harmonics or flageolet-tones 

 of strings, so much used in violin playing, are thus produced. 



No'.v suppose that a string has been excited, and after its tone 

 has been allowed to continue for a moment, it is touched gently 

 at its middle point /3, Fig. 11 b, or ?2> Fig. 11 d. The vibra- 

 tional forms a and c, for which this point is in motion, will be 

 immediately checked and destroyed ; but the vibrational forms 

 b and d, for which this point is at rest, will not be disturbed, 

 and the tones due to them will continue to be heard. In 



Fig. 11. 



this way we can readily discover whether certain members of 

 the series of simple tones are contained in the compound tone of 

 a string when excited in any given way, and the ear can be ren- 

 dered sensible of their existence. 



When once these simple tones in the sound of a string have 

 been thus rendered audible, the ear will readily be able to 

 observe them in the untouched string, after a little accurate 

 attention. 



The series of tones which are thus made to combine with a 



