have pleasure in acknowledging the
services of Mr. W. Reid, a former student, who superintended the
exposure of the patterns, and from time to time took notes of the rate
at which individual patterns faded.

These diagrams contain, perhaps, the most complete series of both old
and new dyes, on the three fibers, which have been simultaneously
exposed to sunlight, and they form an instructive object lesson.

Let me first direct your attention to the diagram containing the
_natural coloring matters_--those dyestuffs which were in use previous
to 1856. Broadly speaking, they are of two kinds; those which dye
textile materials "direct," and those which give no useful color
without the aid of certain metallic salts, called "mordants."

Now, among the natural coloring matters, these "mordant dyes," as they
may be conveniently termed, are much more numerous than the "direct
dyes;" but be it observed, we have fast and fugitive colors in both
classes.

Referring first to the wool patterns and to the "direct dyes," we find
that the only really fast colors are Prussian blue and Vat indigo
blue. Turmeric, orchil, catechu, and indigo carmine are all extremely
fugitive.

As to the "mordant dyes," some yield fast colors with all the usual
mordants, e.g., madder, cochineal, lac dye, kermes, viz., reds with
tin and aluminum, claret browns with copper and chromium, and dull
violets with iron.

Other dyestuffs, like camwood, brazilwood, and their allies, also
young fustic, give always fugitive colors whatever mordant be
employed; others again, e.g., weld, old fustic, quercitron bark,
flavin, and Persian berries, give fast colors with some mordants and
fugitive colors with others; compare, for example, the fast olives of
the chromium, copper, and iron mordants with the fugitive yellows
given by aluminum and tin. A still more striking case is presented by
logwood, which gives a fast greenish-black with copper and very
fugitive colors with aluminum and tin. Other experiments have shown
that the chromium and iron logwood blacks hold an intermediate
position. Abnormal properties are found to be exhibited by camwood and
its allies, with aluminum and tin, the colors at first becoming
darker, and only afterward fading in the normal manner.

When we examine the silk patterns, we find, generally speaking, a
similar degree of fastness among the various natural dyes, as with
wool; in some instances the colors appear even faster, notice, for