314 Wollaston on sounds inaudible by certain ears. 
dred fold more frequent than those which constitute the 
gravest audible sound. 
Since there is nothing in the constitution of the atmos- 
phere to prevent the existence of vibrations incomparably 
more frequent than any of which we are conscious, we may 
imagine that animals like the grylli, whose powers appear to 
commence nearly where ours terminate, may have the fa- 
culty of hearing still sharper sounds, which at present we do 
not know to exist, and that there may be other insects hear- 
ing nothing in common with us, but endued with a power of 
exciting, and a sense that perceives vibrations of the same 
nature indeed as those which constitute our ordinary sounds, 
but so remote, that the animals who perceive them may be 
said to possess another sense, agreeing with our own solely 
in the medium by which it is excited, and possibly wholly 
unaffected by those slower vibrations of which we are 
sensible. 
I should be always most unwilling to occupy the time of 
this Society with idle speculations on mere possible modes of 
existence, and should not have called its attention to this 
subject, had I not observed several curious facts which I 
thought might prove interesting, and may serve to justify 
some latitude of conjecture beyond the strict evidence of our 
sefises. 
