162 



INDIGO. 



Chap. VIII. 



hour. At the end of this time the whole of the 

 surface of the tank is covered with a thick coating 

 of froth of the most brilliant colours, in which blue 

 predominates, particularly near the edges. 



At this stage, it being desirable to incorporate 

 the froth with the liquid below it, I witnessed a 

 most beautiful chemical operation which took me 

 completely by surprise, and showed how universally 

 must be the knowledge of the effect of throwing 

 " oil upon the waters." A very small portion of 

 cabbage-oil — only a few drops — was thrown on the 

 surface of the froth, the workmen then stirred and 

 beat it gently with their flat brooms for a second 

 or two, and the whole disa23peared as if by some 

 enchanter's wand. And so small a quantity of oil 

 was necessary for this purpose that even when the 

 cup had been emptied, and had only the oil that 

 was necessarily adhering to its edges, it was thrown 

 into another tank, and produced the desired effect. 



The liquid, which is now darker in colour, is 

 allowed to stand quiet for some hours, until the 

 colouring matter has sunk to the lower stratum, 

 when about two-thirds of the surface is drawn off 

 and thrown away. The remaining third part 

 is then drawn into a small square tank on a 

 lower level, which is thatched over with straw, 

 and here it remains for three or four days. By 

 this time the colouring matter has separated itself 

 from the water, which is now entirely drained 

 off — the dye occupying three or four inches of the 

 bottom in the form of a thick paste, and of a beau- 



