2 5 8 



TROPICAL AGRICULTURE 



CHAP. 



The refuse 

 plants. 



Noxious 

 odours. 



Beating. 



The forma- 

 tion of the 

 dye. 



Lime water 



Draining 

 off the 

 moisture. 



Cakes. 



is run off by the cock to the second cistern. The refuse 

 plants are then taken out of the first cistern, and either dried 

 in the sun for fuel, or at once placed on the land for manure. 

 They have a noxious odour, due to the putrefying vegetable 

 matter, and this accounts for the unhealthiness characteristic 

 of indigo manufacture. 



The liquor, now being in the second cistern, is to be con- 

 stantly agitated for a period of from one-and-a-half to three 

 hours. The agitation prevents further fermentation, and by- 

 exposing successive layers of the liquor to the air, it enables 

 the whole in time to become oxidised, and thus causes the 

 formation of the insoluble blue dye. The liquor may be 

 agitated by some mechanical contrivance, or by men going 

 into the cistern and beating and churning the fluid with 

 wooden paddles. As the agitation or beating goes on the 

 green liquor becomes of a deeper colour and then gradually 

 turns to a blue shade as the insoluble indigo forms in minute 

 particles called the grain. Then a small quantity of clear 

 lime water is added in order that it may combine with the 

 carbonic acid formed during the process of fermentation, 

 but this is not really necessary, and some planters prefer to 

 do without the lime water as it is said to harm the indigo. 

 The beating having been concluded, the colouring matter is 

 allowed to settle, and in two or three hours the indigo will 

 have subsided to the bottom, and an amber coloured fluid 

 will remain on top. This clear fluid is then to be drawn off 

 by means of the cocks, the highest one being opened first, 

 and after the liquid has ceased running from it, a lower one 

 is to be opened, and so on until nothing is left in the cistern 

 but the indigo which looks like a bluish black mud. This 

 mud-like stuff is then taken out and put into conical linen 

 bags which are hung up so as to allow the surplus moisture 

 to drain away. Afterwards the dye is taken out of the bags 

 and put into shallow trays to dry in the shade. Before it is 

 completely dry, however, it is cut into small cakes and 

 stamped with the plantation mark. 



