Art; but, as a Science, he ought not to be 
unacquainted with its foundation, its ef- 
fence, its conftitution. 
All mufical founds, whether of bells, of 
organ-pipes, of flutes, harpfichords, violins, 
&c. are produced by vibrations in the parts 
of thefe inftruments, excited by fome ex- 
ternal caufe. Thefe vibrations caufe fimilar 
undulations in the air, which ftriking on 
our organs of hearing, brings, from the in- 
ftrument, that vibration which excites in us 
the idea of the tone produced. Thefe in- 
vifible undulations in the air, have, not un- 
aptly, been compared to the waves fuddenly 
produced on a fmooth body of water, by a 
jftone thrown into it: thefe waves are feen 
to expand, in all directions, in concentric 
circles from the fpot where the Hone fell. 
Sound, in like manner, expands in every di- 
rection, and the extent of its progrefs is in 
proportion to the impulfe on the vibrating 
cord or bell. 
Admitting this theory, if every identical 
tone excite a peculiar undulation in the air, 
how happens it, that the various undula- 
tions produced by a rapid fucceffion of tones, 
do not perplex and deftroy each other? 
If you throw a flone into a fifh-pond, and, 
imme- 
