3io 
Dr. Wollaston on sounds 
tension thus produced, a corresponding deafness to low tones 
is occasioned, but, as I never have been in that situation, I 
have not had an opportunity of ascertaining this point by 
direct experiment. 
In the natural healthy state of the human ear, there does 
not seem to be any strict limit to our power of discerning 
low sounds. In listening to those pulsatory vibrations of the 
air of which sound consists, if they become less and less fre- 
quent, we may doubt at what point tones suited to produce 
any musical effect terminate ; yet all persons but those whose 
organs are palpably defective continue sensible of vibratory 
motion, until it becomes a mere tremor, which may be felt 
and even almost counted. 
On the contrary, if we turn our attention to the opposite 
extremity of the scale of audible sounds, and with a series of 
pipes exceeding each other in sharpness, if we examine the 
effects of them successively upon the ears of any consider- 
able number of persons, we shall find (even within the range 
of those tones which are produced for their musical effects) 
a very distinct and striking difference between the powders of 
different individuals, whose organs of hearing are in other 
respects perfect, and shall have reason to infer, that human 
hearing in general is more confined than has been supposed 
with regard to its perception of very acute sounds, and has 
probably, in every instance, some definite limit, at no great 
distance beyond the sounds ordinarily heard. 
It is now some years since I first had occasion to notice 
this species of partial deafness, which I at that time supposed 
to be peculiar to the individual in whom I observed it. While 
I was endeavouring to estimate the pitch of certain sharp 
