320 VEGETABLE SUBSTANCES. 



hility of the indigo to the far greater evil of charring 

 is much augmented. If a better arrangement were 

 provided for this purpose, the process would be ma- 

 terially simplified, and might be carried farther than 

 is now consistent with prudence. 



When the indigo is brought by this means to that 

 degree of consistence which is safely practicable, the 

 thickened fecula is transferred to large cloths wherein 

 the evaporation is further continued by exposure to 

 atmospheric influence. 



This intermediate operation of boiling is considered 

 to be beneficial in arresting a second fermentation of 

 the fecula, to which it is sometimes liable during the 

 process of draining, while the farther advantage is 

 obtained of holding in solution the gummy and 

 other matter unavoidably extracted with the colouring 

 matter. This extraneous part thus passes off with 

 the water, and leaves the indigo in a purer state. 

 The superior quality of the Bengal indigo is attri- 

 buted to this method of preparation. 



If dried hastily in the sun it is apt to become 

 brittle. When all moisture is expelled, and the sub- 

 stance is quite solid, it is cut into square cakes. The 

 process is not yet, however, completed. If exported 

 in this state it would speedily become mouldy ; a 

 second fermentation is therefore necessary. To pro- 

 duce this the cakes are heaped in a cask and simply 

 suffered to remain there for about three weeks. 

 During this time they undergo a degree of fermen- 

 tation ; they become heated, moisture exudes from 

 the surface, a most disagreeable odour is emitted, 

 and finally the cakes are covered with a fine white 

 meal. They are then taken out and dried in the 

 shade for five or six days, when they are in a fit state 

 to be packed for exportation. 



The second method by scalding, instead of fermen- 

 tation, was first proposed for adoption by Dr. Rox- 



