! 



350 MUSICAL NOTES. 



vibration as those indicated above would constitute 

 another musical scale for example, the ' scale of f ' 01 

 scale of g.' 



The relative rates of vibration of the successive note,^ 

 of every scale being the same, it is convenient, whei 

 discussing characters which depend only on these ratios 

 to have some means of indicating the various note; 

 which is equally applicable to all scales. For this pur 

 pose it is usual to speak of the place which any givei 

 note occupies in the scale : thus the notes in the exampl 

 previously given, or the corresponding notes of air 

 other scale, may be indicated generally as follows : 



d d! e' f g r a! V c" 

 1st 2nd 3rd 4th 5th 6th 7th 8th or octave. 



The first note of any scale is commonly called th 

 key-note or tonic of that scale. 



To determine by means of the siren the relatio 

 which exists between the number of vibrations an 

 the pitch of notes, we keep the disc rotating with 

 constant velocity, and direct the jet of air upon two ( 

 more of the circular rows of holes, either successive] 

 or at the same time, using in the latter case two < 

 more tubes. If the disc is made to rotate 5^ times : 

 each second, which requires nearly j-^ths of a revolutic 

 of the handle in our apparatus, the four notes produce 

 will in our notation be the following : 



9' ?' 



By sounding different notes simultaneously, we shi 

 find that some combinations produce a much me 



