ight. From the boiler the mixture is run, after two or three
hours, into a general receiver called the _dripping vat_, or table,
which, for a factory of twelve pairs of preparation vats, is twenty
feet long, ten feet wide, and three feet deep, having a false bottom
two feet under the top edge. This cistern stands in a basin of
masonry (made water-tight with Chunam, hydraulic cement), the bottom
of which slopes to one end, in order to facilitate the drainage. A
thick woollen web is stretched along the bottom of the inner vessel,
to act as a filter. As long as the liquor passes through turbid, it
is pumped back into the receiver; whenever it runs clear, the
receiver is covered with another piece of cloth to exclude the dust,
and allowed to drain at its leisure. Next morning the drained magma
is put into a strong bag, and squeezed in a press. The indigo is
then carefully taken out of the bag, and cut with a brass wire into
bits, about three inches cube, which are dried in an airy house,
upon shelves of wicker work. During the drying a whitish
effloresence comes upon the pieces, which must be carefully removed
with a brush. In some places, particularly on the coast of
Coromandel, the dried indigo lumps are allowed to effloresce in a
cask for some time, and when they become hard they are wiped and
packed for exportation.

2. _Indigo from dried leaves._--The ripe plant being cropped, is to
be dried in sunshine from nine o'clock in the morning till four in
the afternoon, during two days, and threshed to separate the stems
from the leaves, which are then stored up in magazines till a
sufficient quantity he collected for manufacturing operations. The
newly dried leaves must be free from spots, and friable between the
fingers. When kept dry, the leaves undergo, in the course of four
weeks, a material change, their beautiful green tint turning into a
pale blue-grey, previous to which the leaves afford no indigo by
maceration in water, but subsequently a large quantity. Afterwards
the product becomes less considerable.

The following process is pursued to extract indigo from the dried
leaves:--They are infused in the steeping vat with six times their
bulk of water, and allowed to macerate for two hours, with continual
stirring, till all the floating leaves sink. The fine green liquor
is th