58 SCIENCE PROGRESS 



moorhan crop — is gathered. The Java plant grows in Behar 

 to a height of about 3 or 4 feet, more or less according to the 

 soil conditions, and a bushy habit, with a high percentage of 

 leaf, calculated on total weight of the cut plant, is preferred 

 to a more erect woody type. In Assam, however, where the 

 rainfall is plentiful and the soil conditions exactly suit the 

 plant, a height of 8 to 10 feet is attained in the same time of 

 growth. If left in Assam for a whole season the plant grows 

 to a height of 12 to 15 feet. 



When cut only about 6 inches of stem is left, but under 

 favourable soil and climatic conditions growth is rapid, so 

 that in a month or six weeks a young plant, with a high per- 

 centage of leaf, is ready for a second cutting. This is called 

 the khoontie crop. Where the land is liable to be flooded it 

 has been found advantageous to sow as early as the rains 

 permit, in September if possible, and thus to obtain the 

 khoonties before they are destroyed by floods. The Sumatrana 

 plant is usually sown in February, after a period of fallow. 

 Before the seed is sown the ground is hoed and ploughed 

 several times in longitudinal and transverse directions. The 

 loose soil is then compacted by a roller. Correct preparation 

 of the land is a matter of much importance. 



The Manufacture of Indigo. — ^The plant is usually cut as 

 early in the day as is possible, and is carted to the factory. 

 It is then loaded into rectangular vats of about 1,000 cu. ft. 

 capacity, with a depth of about 3 ft. 9 in. to the level of the 

 cross-beams. The vats are brick, covered with Portland 

 cement. They are filled up to the cross-bars, which, when in 

 position, serve to retain the plant when it tends to rise during 

 the fermentation. 



It is usual to have six or more of these vats side by side. 

 Running along the ends of these steeping vats is a beating vat, 

 which is at a lower level. Down the middle of this vat runs a 

 brick wall about 3 feet high, but it is not continued to meet 

 the walls at either end. A paddle-wheel at one end throws 

 the liquid of the vat into the air in a fine spray and causes it 

 to circulate round the middle partition. 



The vats are loaded with cut indigo plant, the amount 

 used varying according to the species, being approximately 

 50 per cent, greater with Sumatrana than with Java indigo. 



Water from a river, stream, or reservoir is then run in so 

 as to cover the plant, and the latter is allowed to steep in it at 

 a temperature of about 90° F. Bergtheil drew up a table 

 showing the average optimum time of steeping for the two 

 varieties of plant. For Java indigo twelve and a half hours 

 at 90 ** F. is recommended, the time being decreased twenty 

 minutes for every degree rise in temperature, so that at 102° F. 



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