656 Theory of Compound Sounds. 
term coalescence is used, in a physical sense; to sigs 
nify any intimate union of bodies or the powers 
of bodies ; and the introduction of the term into 
language proves the existence of the principle in 
nature, or more properly in the human mind. 
For, when a number of agents act in conjunc- 
tion upon one of the senses, we have two ways 
of conceiving their mode of operation. - If the 
sensible effects of each agent be distinctly per- 
ceived, we attribute a separate action to every 
member of the assemblage, and call the aggre- 
gate a mixture: this is the conclusion of a per- 
son who tastes an infusion of pepper in vinegar. 
On the other hand, when we know that certain 
agents are present without being able to recog~ 
nize their distinguishing powers, in the room of 
which we find qualities of a different description, 
we pronounce the aggregate to be ina state of 
coalescence. This is the situation of the che- 
mist, who tastes common salt, but cannot perceive 
the presence of soda and the muriatic acid. It 
is my business then to prove compound sounds 
to be mixtures, not aggregates by coalescence. 
This I shall endeavour to do, by shewing that 
they have properties which belong not to indi- 
viduals, such as a number of tones, a variety of 
directions, and several sets of pulses. 
First, the tones of a flute and violin are as dis- 
tinct to sense as any two things can be when they 
