BRITISH WARBLERS 
produce similar results. The song of the Wren is a good 
example, since the variation is so considerable, and yet so 
strikingly similar at the extreme westerly and south-westerly 
points mentioned. In Worcestershire the song is commenced 
with some peculiarly high notes, but the impression left upon 
my mind after listening to it in Donegal or Sark is that these 
notes are missing. Whether this is really the case requires 
the testimony of more than one person, but the whole song 
is undoubtedly pitched lower. 
Returning once again to our starting-point, we will pro- 
ceed in an easterly direction to Holland, Belgium, or even 
as far as Hungary, and make a similar series of comparisons. 
What do we find? Why this, that the character of the song 
of many species, such as the Whitethroat, Garden Warbler, 
or Willow Warbler, is altered, in some cases to such an extent 
as to be almost beyond recognition, but that in the majority 
of cases there is no lowering of the pitch. 
From these comparisons it will be seen that, speaking 
generally, the tendency is for the pitch to become gradually 
lower as we advance into a climate more and more dominated 
by the Atlantic; and this result is what we should anticipate, 
for the damp air would cause a decrease in the tension of 
the vibratory muscles with a corresponding decrease in the 
number of vibrations and a consequent lowering of the pitch. 
Therefore it seems to me that we need have little hesitation 
in attributing this effect to climatic influence, the more so 
since, on turning our thoughts to the human voice, we find 
corroborative evidence, in that the vocal ligaments are simi- 
larly affected by a damp atmosphere. And if it be thus true 
that a damp air decreases the tension, it must be equally true 
that a-drier atmosphere will tend to increase it with a con- 
sequent raising of the pitch; and this is all that is really 
required to cause unlimited variation. Certain notes may 
be lost, new ones may be added according to the range of 
vibration permitted by any one particular climate, and coinci- 
dently the tone may be-changed, with the result that the song 
may become completely transformed. 
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