Now, though I have gone so far into this mode of
classification, because it does afford some information and light, yet I
can go no farther without getting into a territory that presupposes a
knowledge and acquaintance with the chemical structure of the colouring
matters as organic substances, which would be, at present, beyond us. I
shall now turn to another mode of classification, which, if not so
far-reaching as the other, is at least an exceedingly useful one. The
two methods may be combined to a considerable extent. By the latter plan
the colours may be conveniently divided into three groups: I.,
substantive colours; II., adjective colours; III., mineral and pigment
colours.
_Substantive Dyestuffs._--The substantive colours fix themselves readily
and directly on animal fibres and substances, but only a few amongst
them will dye vegetable fibres like cotton and linen directly. Almost
all substantive colours may, however, be fixed on cotton and linen by
first preparing or mordanting those vegetable fibres.
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