of the Position of Sonorous Bodies, 629 
shews the human ear to be a very delicate judge 
of comparative loudness, 
The nice faculty of discriminating sounds, 
nearly equal in force amongst themselves, being 
established by the preceding experiment, it is 
to be applied in the next place to explain the 
phznomenon we are treating of. When we 
find that successive parts of the same sound 
preserve their force or loudness unaltered, 
we are taught by experience to conclude, that 
the sounding body also preserves its distance 
from us unchanged: on the “contrary, when 
successive parts of the same sound grow stronger 
or weaker, we know with equal certainty, that 
the space interposed between our ears and the 
vibrating object is, for the most part, shortened 
and lengthened accordingly, by changing the 
place of the hearer or of the sounding bedy. Ex- 
perience also teaches mento use the same nicety 
of perception, in ascertaining the positions of so- 
norous objects with respect to their own persons. 
In order to illustrate this question, it will be 
proper to begin with a simple example. Suppose 
then a sounding body, situated towards the 
front of the hearer, to lie in the horizontal 
plane, mentioned in the beginning of this essay, 
and to be placed on one side of the right line, 
which bisects the axis of hearing at right angles :— 
for instance, let it be to the right hand of it. 
