pecially in the winter time. The differences of human hair and hairs
generally, from the higher to the lower forms of mammalia, consist only
in variations of size and arrangement as regards the cells composing the
different parts of the fibre, as well as in a greater or less
development of the scales on the covering or external hair surface.
Thus, under the microscope, the wool and hairs of various animals, as
also even hairs from different parts of the same animal, show a great
variety of structure, development, and appearance.

[Illustration: FIG. 5.]

[Illustration: FIG. 6.]

[Illustration: FIG. 7.]

[Illustration: FIG. 8.]

[Illustration: FIG. 9.]

[Illustration:

Finest merino wool fibre.
Typical wool fibre.
Fibre of wool from Chinese sheep.

FIG. 10.]

[Illustration: FIG. 11.]

[Illustration: FIG. 12.]

We have already observed that hair, if needed for felting, is all the
better--provided, of course, no injury is done to the fibre itself--for
some treatment, by which the scales otherwise lying flatter on the
hair-shafts than in the case of the hairs of wool, are made to stand up
somewhat, extending outwards their free edges. This brings me to the
consideration of a practice pursued by furriers for this purpose, and
known as the _secretage_ or "carrotting" process; it consists in a
treatment with a solution of mercuric nitrate in nitric acid, in order
to improve the felting qualities of the fur. This acid mixture is
brushed on to the fur, which is cut from the skin by a suitable sharp
cutting or shearing machine. A Manchester furrier, who gave me specimens
of some fur untreated by the process, and also some of the same fur that
had been treated, informed me that others of his line of business use
more mercury than he does, _i.e._ leave less free nitric acid in their
mixture; but he prefers his own method, and thinks it answers best for
the promotion of felting. The treated fur he gave me was turned yellow
with the nitric acid, in parts brown, and here and there the hairs were
slightly matted with the acid. In my opinion the fur must suffer from
such unequal treatment with such strong acid, and in the final process
of finishing I should not be surprised if difficulty were found in
getting a high degree of lustre and finish upon hairs thus roughened or
partially disintegrated. Figs. 11 and 12 respectively illustrate fur
fibres from different parts of the same hare before and after the
tre