enes, of the
natural system. Professor Burnett, in his Outline of Botany, informs
us, that "Roccella, a corruption of the Portuguese Rocha, is a name
given to several species of lichen, in allusion to the situation in
which they are found; delighting to grow on otherwise barren seaward
rocks, that thus produce a profitable harvest. Tournefort considers
that one species at least (R. tinctoria) was known to the ancients,
and that it was the especial lichen (Greek: leichaen) of Dioscorides,
which was collected on the rocky islands of the Archipelago, from one
of which it received the name of the 'purple of Amorgus.'"

Of all the known varieties of orchilla, that which is grown in the
Canary Islands stands the highest in estimation, and brings the
greatest price. In the collection of the weed, which is always
performed by the natives, the risk is imminent: they are obliged to be
suspended by ropes over the cliffs, many of which are of stupendous
height, and loss of life frequently occurs in these perilous efforts to
contribute to the luxury of man. Such is the esteem in which the
orchilla of the Canaries is held, that it has recently reached the
enormous value of 400l. per ton. That from the Cape de Verds is next in
quality, but of much greater importance, in reference to the quantity
produced. Madeira and the Azores produce the next qualities. The same
plant, though of a very inferior character, is found in great abundance
in Sardinia, in some parts of Italy, and also on the south coast of
England, Portland Island, Guernsey, &c. but of so poor a kind that it
would not reward the expense of collection.

The original mode of preparing orchilla, that which was practised by
the ancients, is said to have been lost, and many chemical experiments
exhausted in vain for its recovery. In 1300, however, it was
rediscovered by a Florentine merchant, and from that period preserved
as a profound secret, by the Florentines and the Dutch. It appears that
the Florentines were not satisfied with keeping the preparation of
orchilla a mystery from the rest of the world, but that they
endeavoured to lead all inquiry into a false channel, by calling it
tincture of turnsole, desiring it to be believed, that it was an
extract from the heliotropium or turnsole: the Dutch also disguised it
in the form of a paste, which they called _lacmus_ or _litmus_. The
process is now, however, generally known, and simply consists of
cleaning, drying, and powd