East India
Company. In the Admiralty instructions given to Capt. Sir James C.
Ross, on his Antarctic voyage, a few years ago, his attention was
specially called to the search and enquiry for substitutes for the
_Rocella_, which is now becoming scarce. A prize medal was awarded, in
1851, to an exhibitor from the Elbe for specimens of the weed, and an
extract of red and violet orchil. Specimens of varieties of the
lichens used in the manufacture of cudbear, orchil and litmus, and of
the substance obtained, were also shown in the British department,
which were awarded prize medals.

The beauty of the dyes given by common materials, in the Highlands of
Scotland, to some of the cloths which were exhibited, should lead our
botanists and chemists to examine, more closely than they have
hitherto done, the dye-stuffs that might be extracted from British
plants. Woad (_Isatis tinctoria_) and the dyers' yellow woad (_Reseda
lutea_), are both well known. A piece of tweed, spun and woven in
Ross-shire, was dyed brown and black, by such cheap and common dyes as
moss and alder bark, and the colors were unexceptionable.

Sutherlandshire tweed and stockings, possessing a rich brown color,
were produced with no more valuable dye than soot; in another piece,
beautifully dyed, the yellow was obtained from stoney rag, brown from
the crops of young heather, and purple from the same, but subjecting
the yarn to a greater action of the dye than was necessary to produce
brown. There is very little doubt but that beautiful and permanent
dyes, from brown to a very rich purple, might be cheaply procured by
scientific preparations of the common heather (_Genista tinctoria_).
The inhabitants of Skye exhibited cloth with a peculiarly rich dye,
obtained from the "crobal" moss. In the Spanish department, specimens
of vegetable dyes from many cultivated and wild plants were furnished
by the Agricultural Board of Saragossa, and of several of these it
would be important to obtain descriptions and particulars.

Gums are of essential importance to the dyer, and the imports of
these, therefore, are large, averaging about 8,000 tons.

INDIGO.

The plants which afford this dye grow chiefly in the East and West
Indies, in the middle regions of America, in Africa and Europe. They
are all species of the genera _Indigofera_, _Isatis_ and _Nerium_.
_Indigofera tinctoria_ or _coerulea_, furnishes the chief indigo of
commerce, and affords in Bengal, Malabar, M