INDIGO. Indigofera. A vegetable dye, embracing a large industry in the East and West Indies, and Central America, from whence the indigo of commerce is obtained. The varieties cultivated in Hindostan are principally I. nerium tinetorium and L tinetoria argentea. In the West Indies and Central America the variety I. anil is mostly planted. In Georgia, and other Gulf States this variety has run wild. Baptista tine toriet is atso indigenous in the South. In the last century indigo was extensively cultivated in the South. In 1731, 100,000 pounds were exported from Charleston, S. C. This was yearly increased up to the time of the Revolutionary war the yearly export reached 107.660 pounds. In 1794, 1,550,880 pounds were exported from the United States. The introduction of the cot ton gin, and the profits arising from the cultiva tion of cotton, is undoubtedly one of the prim causes of the decline of indigo-raising in thc United States. Near Orangeburg, S. C., then are six indigo farms carried on. Indigo requires rich but sandy land. It sprouts annually from the roots, requiring to be sown but once in seven or eight years. With capital and careful manage ment there is no doubt but that the cultivation of indigo might again be made a paying indus try upon suitable lands in the Gulf States. In regard to the culture and manufacture of indigo in this country, Porcher, in his work on the Resources of Southern Fields• and Forests, (18690 says, that the soils best adapted are the rich, sandy loams, though it grows on most lands moderately well, provided they are not wet. The ground should be well broken, and kept light and free from grass by the plow. Thc nature of the manure exerts a great influence upon the quantity and quality of the coloring principles. Those substances which act as stimulants to vegetation, such as lime, pou drette, ashes, etc., favor the growth of the plant without injuring the coloring matter Where barn-yard manure has been largely used crop of grain should first be raised on the land. The seed should be noixed with ashes or sand and sown in drills fourteen inches apart, four quarts of seeds to the acre. In the climate of middle Georgia the seed should be sown the 1st of April. When it first comes up it should have the grass picked out with the hand. When an inch or two high the grass between the rows should be cut out by the hoe or scraper and the soil loosened about the roots. These weedings are enough before the first cutting, which should commence as soon as the plant throws out the bloom. It is so easily injured by the sun after being cut that the operation should be commenced and end in the afternoon. After cutting with the reap hook it is put under the shed until it can be put in the vats. In Georgia, two cuttings yielded sixty pounds of indigo to an acre, provided the roots were not injured in the first cutting, which, at three acres to the hand, would be one hun dred and eighty pounds. It is said that among the Arab cultivators in Egypt and Morocco the seed is sown only once in seven years, and that two crops a year are obtained. Among these people the process of rnanufacturing or extri cating the coloring raatter from the plant is given as follows: Three wooden vats are pro vided and so placed at different levels as that the contents of the first can be readily transferred to the second, and again from that to the third.
The upper vessel is called the steeping vat, and in this the plants are loosely laid, in sufficient quantity to cover the bottom, and water poured over them to the depth of two or three inches. In about eighteen hours fermentation begins and the plants swell and give off large quantities of e:a which tinges the water with a lively green colcr. After all the coloring rnatter, or grain, as it is technically called, is extracted, the turbid liquor is drawn off into the second vat where it is violently agitated and beaten in order to separate the grain from the water. A great quantity of air-bubbles are driven off by this beating, and the color of the contents of the vat changes from green to deep blue. 'When the grain has subsided to the bottom of the, vat the supernatant liquor is drawn off and the grain is discharged into the third vat, where a further subsidence and drawing off ensue, and the grain is n,2xt transferred to sacks and hung up to drain. It is then placed in wooden boxes and exposed to the air and sun until all the moisture is evap orated, when the process is completed and the indigo is packed in chests ready for shipment. In the great indigo-factories of Bengal some part of the drying is effected by the agency of fire. The following process of manufacturing indigo in small quantities for domestic use is given by the Southern Agriculturist: Cut the indigo when the under leaves begin to dry, and while the dew is on them in the marning; put them in a barrel and fill this with rain-water, and place weights on to keep it under water; when bubbles begin to form on the top and the water begins to look of a reddish color, it is soaked enough and must be taken out, taking care to wring and squeeze the leaves well, so as to obtain all the strength of the plant; it must then be churned (which may be done by means of a tolerably open basket with a handle to raise it up and down) until the liquid is quite in a foam. To ascertain whether it is done enough, take out a spoonful in a plate and put a small quantity of very strong lye to it. If it curdles, the indigo is churned enough, and you must proceed to break the liquor in the barrel in the same way, by putting in the lye (which must be as strong as possible) by small quantities, and continuing to churn until it is all sufficiently curdled; care must be taken not to put in too much lye, as that will spoil it. When it curdles freely with the lye, it must be sprinkled well over the top with oil, which immediately causes the foam to subside, after which it must stand till the indigo settles to the bottom of the barrel. This may be discovered by the appearance of the water, which must be let off gradually by boring holes, first near the top and afterward lower, as it continues to settle; when the water is all let off and nothing remains but the weed, take that and put it in a hag (flan nel is the best) and hang it up,to dry, afterward spreading it to dry on large dishes. Take care that none of the foam, which is the strength of the weed, escapes; but if it rises too high, sprinkle it with oil.