The sharpened, jagged edges enable these scales
more easily to get under the opposing scales, and to penetrate inwards
and downwards according to the pressure exerted. The free edges of the
scales of wool are much longer and deeper than in the case of hair. In
hair the overlapping scales are attached to the under layer up to the
edges of those scales, and at this extremity can only be detached by
the use of certain reagents. But this is not so with wool, for here the
ends of the scales are, for nearly two-thirds of their length, free, and
are, moreover, partially turned outwards. One of the fibres shown in
Fig. 10 is that of the merino sheep, and is one of the most valuable and
beautiful wools grown. There you have the type of a fibre best suited
for textile purposes, and the more closely different hairs approach
this, the more suitable and valuable they become for those purposes, and
_vice versa_. With regard to the curly structure of wool, which
increases the matting tendency, though the true cause of this curl is
not known, there appears to be a close relationship between the tendency
to curl, the fineness of the fibre, and the number of scales per linear
inch upon the surface.
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