On the Method of judging by the Ear, Sc. 629 
terms, perceives, whether it comes from before 
‘or behind him, from his right hand or his left. 
His powers of discrimination in this respect 
are not confined to the general limits or points, 
which I have here mentioned by way of illus. 
tration; for, he can in most instances divide 
these principal angles, not indeed into degrees 
and> minutes, but with so much accuracy as to 
know whether the sounding object lies ina line 
making a less angle with that imaginary right 
line, which may be supposed to join his ears; 
or with. another right line, which, passing from 
the front to the back part of his head, bisects 
the former at right angles. This sort of per- 
ception is not confined to what passes upon the 
horizon; for, place the same person on a tower, 
or other steep eminence, and he will perceive 
whether a certain sound comes from a part 
below or above him: besides which, he imme- 
diately combines this sensation with the preced- 
ing, so as to form a judgment respecting 
the true situation of the sounding body, which 
is of great practical use in the common affairs’ 
of life. 
The nature of the present essay seems to 
require, that the reader should -conceive the 
human head to be divided by two fixed mathe- 
VOL, V. 29 
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