A blue colouring matter, extracted from the leaves and stalks of the indigofera tincteria, or anil plant. The ancients were acquainted with this dye under the name of Indicum. It is found both in the East and West Indies, is spontaneous in China and Cochin China, and is cultivated all over those vast empires. The seed is sown in little furrows two or three inches deep, and about twelve inches distance from each other. Though it may be sown at all seasons, the moisture of the spring causes the plant to shoot up in three or four days, and it is at maturity at the end of two months. When gathered it is thrown into a large cistern, called the steeping vat, containing sufficient water just to cover the vegetable. The matter begins to ferment, sooner or later, according to the warmth of the weather, and the maturity of the plant, generally occupying from six to twenty hours. When the liquor is in a proper state of fermentation (which is known by its heat, its thickening, an abundant froth that it throws up, and its blue colour, inclining to violet), it is let out by cocks in the bottom, into another vat placed for that purpose.

In this second vat, called the beating vat, the liquor is strongly and incessantly beaten with a kind of buckets full of holes, fastened to poles.

This part of the process requires the greatest precaution. If the beating is ceased too soon, a part of the colouring matter remains dissolved in the liquor; if continued a little too long, a part of that which is separated is dissolved afresh. The exact time for discontinuing the process is determined by taking up some of the liquor occasionally in a little cup, and observing whether the blue fecula is disposed to separate and subside. The whole being now suffered to rest till the blue matter has settled, the clear water is let off by cocks in the sides, at different heights, and the blue matter at the bottom is discharged by another cock into a third vat, where it is suffered to settle for some time longer, then conveyed, in a half fluid state, into bags of cloth, to strain off more of its moisture; and, lastly, exposed to the air in the shade, in shallow wooden boxes, till it is thoroughly dry.