of the Position of Sonorous Bodies. 639 
by their sensibility. The same apparatus may 
be used to shew, that all parts of the head are 
not equally alive to the impulses of sounds: for 
a stick, which is of a proper length to impress) 
the beats of a watch very faintly on the ear and 
‘parts adjacent, will prove too long to produce 
the same effect on the forehead, which is never= 
theless much more exquisite in its feelings than 
the back part of the head. 
_ The phenomena of oblique hearing remain 
to be explained; which case occurs as often as 
the sounding body is situated in the horizontal 
plane, but not in the right line that bisects the 
axis of hearing at right angles. Let M be the 
place of the sounding body, and draw MO to 
the centre of the circle: also let OC bisect 
the arc ECF, and take OG in it equal to 
OM: also draw WM, MR, PG, GI tan- 
gents to the circle. Now suppose a sound 
equal to that at M, to proceed from G,.then 
the latter would haye the same effect on the 
arc TCP that the former has on WDR, be- 
cause the arcs are manifestly equal, and alike 
situated relative to the points M and G. But 
the sound proceeding from G is a case of di- 
_rect hearing, consequently the ears placed at E 
and F receive equal impressions from it, which 
is not the case with the pulses that flow from M, 
VOL, V. Ss 
‘ 
