to madder, a more
concentrated extract containing the colouring-matter itself was largely
used by dyers and cotton printers under the name of "garancin." In 1868 we
were importing, in addition to the 15,000 to 16,000 tons of madder, about
2000 tons of this extract annually, at a cost of L150 per ton. By 1878 the
importation of garancin had sunk to about 140 tons, and the price had
been lowered to L65 per ton. The total value of the imports of madder and
garancin in 1868 was over one million pounds sterling; in ten years the
value of these same imports had been reduced to about L38,000.
Concurrently with this falling off in the demand for the natural
colouring-matter, the cultivation of the madder plant had to be abandoned,
and the vast tracts of land devoted to this purpose became available for
other crops. A change amounting to a revolution was produced in an
agricultural industry by a discovery in chemistry.

In the persons of two Frenchmen, Messrs. Robiquet and Colin, science laid
hands on the colouring-matter of the _Rubia_ in 1826. These chemists
isolated two compounds which they named alizarin and purpurin. It is now
known that there are at least six distinct colouring-matters in the madder
root, all of these being anthracene derivatives. It is known also that the
colouring-matters do not exist in the free state in the plant, but in the
form of compounds known as glucosides, _i.e._ compounds consisting of the
colouring-matter combined with the sugar known as glucose. It may be
mentioned incidentally that the colouring-matter of the indigo plant also
exists as a glucoside in the plant. During a period of more than forty
years from the date of its isolation, alizarin was from time to time
submitted to examination by chemists, but its composition was not
completely established till 1868, when Graebe and Liebermann, by heating
it with zinc-dust, obtained anthracene. This was the discovery which gave
the death-blow to the madder culture, and converted the last fraction of
the tar-oil from a waste product into a material of the greatest value.

The large quantity of madder consumed for tinctorial purposes is
indicative of the value of this dye-stuff. It produces shades of red,
purple, violet, black, or deep brown, according to the mordant with which
the fabric is impregnated. The colours obtained by the use of madder are
among the fastest of dyes, the brilliant "Turkey red" being one of the
most familiar shades. The dis