commotion, apparently boiling, innumerable bubbles mount to the
surface, and a copper colored dense scum covers the whole. As long
as the liquor is agitated, the fermentation must not be disturbed,
but when it becomes more tranquil, the liquor is to be drawn off
into the lower cistern. It is of the utmost consequence not to push
the fermentation too far, because the quality of the whole indigo is
deteriorated; but rather to cut it short, in which case there is,
indeed, a loss of weight, but the article is better. The liquor
possesses now a glistening yellow color, which, when the indigo
precipitates, changes to green. The average temperature of the
liquor is commonly 85 deg. Fahr.; its specific gravity at the
surface is 1.0015; and at the bottom 1.003.

As soon as the liquor has been run into the lower cistern, ten men
are set to work to beat it with oars, or shovels four feet long,
called _busquets_. Paddle wheels have also been employed for the
same purpose. Meanwhile two other laborers clear away the
compressing beams and bamboos from the surface of the upper vat,
remove the exhausted plant, set it to dry for fuel, clean out the
vessel, and stratify fresh plants in it. The fermented plant appears
still green, but it has lost three-fourths of its bulk in the
process, or from twelve to fourteen per cent. of its weight, chiefly
water and extractive matter.

The liquor in the lower vat must be strongly beaten for an hour and
a half, when the indigo begins to agglomerate in flocks, and to
precipitate. This is the moment for judging whether there has been
any error committed in the fermentation, which must be corrected by
the operation of beating. If the fermentation has been defective,
much froth rises in the beating, which must be allayed with a little
oil, and then a reddish tinge appears. If large round granulations
are formed, the beating is continued, in order to see if they will
grow smaller. If they become as small as fine sand, and if the water
clears up, the indigo is allowed quietly to subside. Should the vat
have been over-fermented, a thick fat-looking crust covers the
liquor, which does not disappear by the introduction of a flask of
oil. In such a case the beating must be moderated. Whenever the
granulations become round, and begin to subside, and the liquor
clears