of the Position of Sonorous Bodies. 691 
they borrow mutually one from another, Op-« 
ticians have demonstrated, that vision would 
prove but of little use, were not its natural im- 
pérfections corrected by touch: hearing also 
forms its judgment in one class of phenomena, 
from a kind of secondary knowledge afforded 
by the hands and eyes. Two sounds moving 
through unequal spaces may be equal in force, 
nay the remoter may prove the more powerful 
of the two: Joudness, therefore, is not a sure 
indication of proximity; but every man has re- 
marked, at an age when his memory was too 
weak to record incidents, that sounds lose more 
and more of their asperities the farther they 
move: every man, therefore, in his riper years, 
considers roughness to be a proof of proximity, 
and smoothness to be the criterion of remote- 
ness. _ That this faculty is acquired, appears 
‘evident from the errors into which it leads 
the judgment under certain circumstances. I 
have known a person mistake the mellow tone, 
which is produced by rubbing the brim of a 
glass vessel with a wet finger, for the blast of 
a distant horn, though there was but the breadth 
of a table between him and the piace of the 
sound, and almost every one falls into a similar 
deception the first time he hears the soft notes 
of an olian harp. If then the ear correct its 
VOL. Vy RR 
