312 Dr. Wollaston on sounds 
seems not very rare, as I have met witli several instances of 
persons not aware of such a sound. The chirping, which I 
suppose to be that of the gryllus campestris, appears to be 
rather higher than that of the bat, and accordingly will ap- 
proach the limit of a greater number of ears ; for, as far as 
I am yet able to estimate, human hearing in general extends 
but a few notes above this pitch. I cannot, however, mea- 
sure these sounds with precision ; for it is difficult to make a 
pipe to sound such notes, and still more difficult to appreciate 
the degree of their acuteness. 
The chirping of the sparrow will vary somewhat in its 
pitch, but seems to be about four octaves above E in the 
middle of the piano-forte. 
The note of the bat may be stated at a full octave higher 
than the sparrow, and I believe that some insects may reach 
as far as one octave more ; for there are sounds decidedly 
higher than that of a small pipe one-fourth of an inch in 
length, which cannot be far from six octaves above the 
middle E. But since this pipe is at the limit of my own hear- 
ing, I cannot judge how much the note to which I allude 
might exceed it in acuteness, as my knowledge of the exis- 
tence of this sound is derived wholly from some young 
friends who were present, and heard a chirping, when I was 
not aware of any sound. I suppose it to have been the cry 
of some species of gryllus, and I imagine it to differ from the 
gryllus campestris, because I have often heard the cry of 
that insect perfectly. 
From the numerous instances in which I have now wit- 
nessed the limit to acuteness of hearing, and from the dis- 
tinct succession of steps that I might enumerate in the 
