most difficult of all to dye perfectly. Thus, if a piece
of linen cloth be dipped into a solution of madder, it will come out
just tinged with the colour; but if a piece of the same be previously
dipped into a solution of alum or copperas, and dried previously to
being dipped in the madder, the alum will become so far impregnated with
the colouring principle, that the cloth will receive a perfect dye, and
be so fixed that it cannot be separated by any common means. Thus it
will be observed, that the art of dyeing permanent colours depends on
this intermediate principle, which is termed a mordant. These mordants
are very numerous; and on a knowledge of them appears to rest the
principal secret of dyeing. The following mode is, however, a very
convenient one for makig experiments on fixing the colouring principles
of any vegetable extract: To have several pieces of cloth, woollen,
cotton, silk, and linen, dipped in the different mordants, and by
keeping a small vessel filled with the colouring solution on a fire in a
state a little below boiling, by cutting small pieces of each, and
immersing them in the colour, and examining and comparing with each
other. Experiments of this kind are well worth the attention of persons;
for, when we refer to this department, we shall find very few plants
which are either now, or ever have been, cultivated for this purpose,
although it is well known that so many contain this principle. I have
inserted the following, as being known to contain the different colours
mentioned; but there are many other plants equally productive of this
principle that remain quite unnoticed at present.

539. ACANTHUS mollis. BEAR'S-BREECH.--This gives a fine yellow, which
was in use among the ancients.

540. ACTAEA spicata. BANEBERRY.--The juice of the berries affords a deep
black, and is fixed with alum.

541. ANCHUSA officinalis. YELLOW ANCHUSA, or BLUE-FLOWERED BUGLOSS.--The
juice of the corolla gives out to acids a beautiful green.

542. ANTHEMIS tinctoria.--The flowers afford a shining yellow.

543. ANTHYLLIS vulneraria. KIDNEY-VETCH.--The whole plant gives out a
yellow, which is in use for colouring the garments of the country-
people.--Linn.

544. ARBUTUS uva-ursi. BEAR'S-BERRY.--The leaves boiled in an acid will
dye a brown.

545. ASPERULA tinctoria. WOODROOF.--The roots give a red similar to
madder.

546. ANEMONE Pulsatilla. PASQUE-FLOWER.--The corolla, a gree