( '72 ) 
tave coincides with the fundamental note 
only at every fecond vibration. 
But you will now afk, how it happens, 
as thefe vibrations gradually ceafe, that the 
tone continues the fame, till it is heard no 
more? It were natural to fuppofe, as the 
acutenefs of the found depends on the cele- 
rity of the vibrations, that as they become 
flower towards their decline, the tone would 
grow deeper, or more grave. If it were true 
that they vibrate gradually flower, the ob- 
jection would be unanfwerable. But the 
fact is otherwife. As a pendulum performs 
all its ofcillations in equal times; its greateft 
range in the fame time as its lead; fo a 
mufical firing makes its firft long vibration 
in the fame time as its Jaft fhort one; for 
this reafon, the tone is uniformly the fame 
from firft to laft. 
In proof of what I have faid concerning 
the length of firings, you obferve, that the 
firings, of this harpfichord, which make the 
high notes are the fhorteft, and that they 
gradually increafe in length as you defcend 
to the deepeft note of the inftrument. Now 
though there be black and white keys on 
this harpfichord, and each of thefe flrike a 
dif- 
