346 
THE EAR AND HEARING. 
the free action of the tympanum arrested, the sense of 
externality was quite lost, and the feelings of sound regarded 
as subjective. 
The sense of direction is by no means very delicate, 
even after being educated to the full. We can readily 
recognise whether a voice at about the level of our ears is 
before or behind, to the right or left, up or down ; but if we 
were to stand opposite a row of persons at a distance of, say, 
ten feet, we should not be able to say, unassisted by sight, &c., 
which one uttered a sound, as schoolmasters well know. 
So it is almost impossible to find out a skylark in the air 
from the sound of its song. A simple experiment illustrating 
the uncertainty of our sense of direction of sounds may be 
performed by blindfolding a person seated in a chair, and 
clicking two coins opposite various parts of his body within 
leach of his arms, requiring him to point to the exact locality 
whence the sound proceeds. Some people will be found to 
eer greatly in their estimates. In his opening address, at the 
recent meeting of the British Association, Lord Bayleigh 
remarked upon the imperfect state of our knowledge of the 
means whereby we recognise the direction of sounds, and 
stated that it has been proved that, when proper precautions 
are taken, we are unable to distinguish whether a pure tone, 
as from a vibrating tuning-fork held over a suitable resonator, 
comes from before or behind, as might have been expected 
from an a priori point of view, but, what would not have been 
expected is, that with almost any other sort of sound, from a 
clap of the hands to the clearest vowel sound, the discrimi¬ 
nation is not only possible, but easy and instinctive. In 
these cases it does not appear how the possession of two ears 
helps, though there is some evidence that it does; and even 
when the sound comes to us from the right or left the 
explanation of the ready discrimination which is then 
possible with pure tones is not so easy as it first seems. 
We should be inclined to think that the sound is heard 
much more loudly with the ear turned towards it than with 
the ear turned from it, and that in this way direction is 
recognised ; but if we try the experiment we find that, at any 
rate with notes near the middle of the musical scale, the 
difference of loudness is by no means so very great. The 
wave-lengths of such notes are long enough in relation to 
the dimensions of the head to forbid the formation of anything 
like a shadow in which the averted ear may be sheltered. 
In such cases I should myself be inclined to look for the 
power of discrimination rather in slight qualitative differences 
in the effect of given stimuli according as they affect more 
