Theory of Compound Sounds. 659 
double motion is also accomplished in the time 
of a single vibration. 
Proposition II. Both the absolute and re- 
lative motions are greatest amongst those parti- 
cles which are nearest the sounding body, and 
they diminish as the distance from that body in- 
creases; but, in all cases, the change of place is 
too small to be perceived by the ear, on which 
account every particle preserves a fixed position 
in respect of this organ and its connections, 
For each corpuscle is confined within the cir- 
cumference ofa physical right line, the diameter of 
which is determined by its own absolute motion, 
Proposition III. If two sounding bodies, 
_ affording different notes, act in conjunction upon 
the same particle, through the media of two right 
lines of similar particles connecting them with it, 
this particle will be urged at the same instant in 
the direction of these lines, by two forces having 
an inconstant ratio. 
For, let the particle A be urged, by the acuter 
sound, in the line SA, and by the graver, in the 
the line TA; (vede fig. 2, plate 9, page 636.); 
then the contiguous particle V, placed in SA, 
will approach to, and recede from A more fre~ 
quently than W, similarly placed in TA, by 
Prop. I.: consequently the force of V upon 
A will vary in a quicker manner than the force 
ef W upon-A; but this variation of ratio is 
