APPENDIX. 679 



the rapidity is often fo great, and it is alio fo un- 

 certain when they may (lop, that we cannot reduce 

 the pafTages to form a mufical bar, in any time 

 whatfoever. 



The fecond is, that the pitch of mod birds is con- 

 fiderably higher* than the mod fhrill notes ofthofe 

 inftruments, which contain even the greateft com- 

 pafs. 



I have before faid, that our ideas of a voice, 

 or inftrument, being perfectly in tune or not, arife 

 from comparing it with the mufical intervals to 

 which we are moft accuftomed. 



As the upper and lower parts of every inftru- 

 ment, however, are butfeldom ufed, we are not fo 

 well acquainted with the intervals in the higher! 

 and lowed: octaves, as we are with thofe which are 

 more central •, and for this reafon the harpfichord- 

 tuners find it more difficult to tune thefe extreme 

 parts. 



As a bird's pitch, therefore, is higher than that 

 of an inftrument, we are confequently at a ftil! 



* Dr. Wallis. is miflaken in part of what he fuppofes to be 

 the caufe of ihrillnefs in the voice, " Nam ut tubus, fie tra- 

 ?' chea longior, & ftri&ior, fonum emcit magis acutum." 

 Grammar, p. 3. 



The narrower the pipe is, the more fharp the pitch as he 

 rightly obferves ; but the length of the tube hath juil the con- 

 trary effect, becaufe players on the flute always infert a lon^ 

 ger middle-piece, when they want to make the inftrument more 

 flat, 



Y y 3 greater 



