628 On the Method of judging by the Ear 
which, it was moved in the same right line 
sometimes two feet further from me, at other 
times two feet nearer to my person; and I could 
always distinguish distances thus varied, The 
range of the sound, or the distance at which it 
ceased to be audible, was 240 feet, or six times 
the interval made use of in the experiment. 
The sound which I employed was therefore of 
a moderate force, and perhaps the interval was 
a suitable one, being neither too great nor too 
little a part of the whole range. It appears 
then, that a good ear will discover a percep- 
tible difference in the forces of two equal 
sounds; the one of which moves through one 
sixth part of its whole range, and the other 
through a space which differs from the distance 
of the former only the 120th. part of the range 
common to them both.—The foregoing instance 
affords a remarkable proof of the ear’s accuracy 
in comparing, slight variations in the momenta 
of sounds; and I have reason to believe that 
the delicacy of my organs, in this respect, sur- 
passes the medium of sensibility ; for, some ears 
which were tried in the same manney, did not 
perceive the effect in question, until the instru- 
ment had been moved four feet, or the 6oth. 
part of my range. But either instance furnishes 
@ proof sufficient for the present purpose, and 
