236 TROPICAL VEGETABLE DYES 



steeping-trough, and there covered with water. The matter 

 begins to ferment, sooner or later, according to the warmth of 

 the weather, and the maturity of the plant ; sometimes in six 

 or eight hours, and sometimes in not less than twenty. The 

 liquor grows hot and throws up a plentiful copper-coloured 

 froth which passes into violet towards the end, but the pulp 

 and liquor remain green. At this time, without touching the 

 herb, the liquor impregnated with its tincture is let out by 

 cocks in the bottom into another vat, placed for that purpose 

 so as to be commanded by the first. The process must be 

 conducted with great caution and technical ability, for if the 

 fermenting liquor is abstracted too soon, part of the colouring 

 matter remains in the plant, while by a longer delay one runs 

 the risk of partly losing it through putrefaction. 



In the second vat, called the beating vat, the liquor is strongly 

 and incessantly beaten with a kind of buckets fastened to poles, 

 till the colouring matter, which during this process changes 

 from green to deep blue, is united into a body, and acquires a 

 tendency to precipitate. This operation, which generally lasts a 

 couple of hours, must also be conducted with great caution, for 

 by ceasing it too soon, colouring particles not sufficiently 

 saturated with oxygen remain in the liquid, while by continuing 

 it for too long a time, a new fermentation is brought on, 

 which changes and destroys the pigment. 



As soon as it is judged that the beating is sufficient, the mass 

 is left at rest for two hours, after which the clear liquor is 

 drawn off by cocks in the side of the vat, and the blue part is 

 discharged by another cock into a boiler, where, having been 

 brought to that degree of consistence, which is safely practicable, 

 it is conveyed into bags of cloth to strain off the remaining 

 moisture, and lastly exposed to the air in the shade, in shallow 

 wooden boxes, till it is thoroughly dry. 



Since the last forty years, great changes have taken place in 

 the indigo trade. Formerly that from Guatemala was consi- 

 dered the best, and very little was imported from the East 

 Indies, while now Bengal not only produces the finest indigo, 

 but also brings by far the largest quantity to the market. 

 This change is entirely owing to a few energetic and enlightened 

 men, who, by introducing improvements in the cultivation and 

 manufacture of indigo, have raised it to be the chief export 



