The molecules composing the string are disturbed in the string's
vibrating length by the means used to excite the sound, and run off into
sections, the comparative length and number of which depend partly upon
the place in the string the excitement starts from; partly upon the
force and the form of force that is employed; and partly upon the
length, thickness, weight, strain, and elasticity of the string, with
some small allowance for gravitation. The vibrating sections are of
wave-like contour; the nodes or points of apparent rest being really
knots of the greatest pressure from crossing streams of molecules. Where
the pressure slackens, the sections rise into loops, the curves of which
show the points of least pressure. Now, if the string be struck upon a
loop, less energy is communicated to the string, and the carrying power
of the sound proportionately fails. If the string be struck upon a node,
greater energy ensues, and the carrying power proportionately gains.
By this we recognize the importance of the place of contact, or
striking-place of the hammer against the string; and the necessity, in
order to obtain good fundamental tone, which shall carry, of the note
being started from a node.
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