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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 inftrument, 
however, are but feldom ufed, we are not fo well 
acquainted with the intervals in the higheft and 
loweft odtaves, 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 
any inftrument, we are confequently at a ftill greater 
lofs when we attempt to mark their notes in mufical 
chara&ers, which we can fo readily apply to fuch as 
we can diftinguifh with precifion. 
The third, however, and unfurmountable'diffi- 
culty is, that the intervals ufed by birds are com- 
monly fo minute, that we cannot judge at all of 
them from the more grofs intervals into which we 
divide our mufical o&ave. 
It lliould therefore be recolle&ed, by thofe who 
have contended that the Greeks and Romans were ac- 
quainted with fuch more minute intervals of the 
o&ave, that they muft infift the ancients had organs 
of fenfation, with which their degenerate pofterity 
are totally unprovided. 
Though we cannot attain the more delicate and 
imperceptible intervals in the fong of birds *, yet 
many of them are capable of whiftling tunes with 
our more grofs intervals, as is well known by the 
* There have been inttances indeed of per Tons who would 
whittle the notes of birds, but thefe are too rare to be argued 
.from. 
common 
