of the Position of Sonorous Bodies. 643 
The experiment was tried in an open plain, to 
prevent the intrusion of reflected sounds as much 
as possible. The instrument made use of was 
that which has been already described, as consist~ 
ing of a bolt driven by a spring against a metal 
button ; and the distance from my person to this 
sounding body was kept equal to forty feet, in 
the different parts of the experiment. I also 
discovered, by the assistance of the same appa- 
ratus, that the least sensible angle of elevation 
above the horizontal plane, was not more than 
ten degrees at the last mentioned, distance; the 
sounding body being placed in the vertical plane, 
to which the axis of hearing is perpendicular. 
But the foregoing observations are not to be 
adopted and used as fixed rules, for much 
depends on the comparative sensibility of the 
auditory organ in different persons; and an alter- 
ation in the force of a sound will, without doubt, 
make a considerable change in the result of the 
experiment on elevation : because I have ob- 
served, that the feeble sound of a distant watch 
though sufficient to shew whether it came from 
my right or left hand, was too weak to point 
gut its situation, relative to the horizontal plane 
passing through my head. This imperfection in 
the sense of hearing, if it may be called one, is 
in all probability owing to the want of sensibility 
in the upper part of the head and lower part of 
