1881.] on Indigo, and its Artificial Production. 581 



woad ; and severe enactments were i^romulgated against the introduc- 

 tion of the foreign colouring matter, an edict condemning to deatli 

 persons " who used that pernicious drug called devil's food" being 

 issued by Henry the Fourth of France. The chief source of Indian 

 indigo is the Indiijofcra tindoria, an herbaceous plant raised from 

 seed which is sown in either spring or autumn. The jilant gi'ows 

 with a single stalk to a height of about three feet six inches, and 

 about the thickness of a finger. It is usually cut for the first time in 

 Juno or July, and a second or even a third cutting obtained later in 

 the year. The value of the croj) depends on the number of leaves 

 which the plant puts forth, as it is in the leaves that the colouring 

 principle is chiefly contained. Both the prejiaration of the colouring 

 matter from the plant, and its emi)loyment as a dye or as a jmint, aro 

 carried on at the present day exactly as they have been for ages past. 

 The description of the processes given by Dioscorides and Pliny 

 tally exactly wdth the crude mode of manufacture carried on in 

 Bengal at the present day as follows : — 



" The Bengal indigo factories usually contain two rows of vats, 

 the bottom of one row being level with the top of the other. Each 

 series numbers from fifteen to twenty, and each vat is about 7 yards 

 square and 3 feet deep ; they are built of brickwork lined with stono 

 or cement. About a hundred bundles of the cut indigo j^lants aro 

 placed in each vat in rows, and pressed down with heavy i)ieces of 

 wood ; this is essential to the success of the operation. Water is 

 then run in so as to completely submerge the plants, when a fer- 

 mentation quickly ensues, which lasts from nine to fourteen hours, 

 according to the temperature of the atmosj^here. From time to time 

 a small quantity of the liquor is taken from the bottom of the vat to 

 see how the operation is proceeding. If the liquor has a pale-yellow 

 hue the product obtained from it will be far richer in quality, but not 

 so abundant as if it had a golden-yellow appearance. The liquor is 

 then run off into the lower vats, into which men enter and agitate it 

 by means of bats or oars, or else mechanically by means of a dash- 

 wheel, each vat requiring seventeen or eighteen workpeople, who aro 

 kept employed for three or four hours. During the operation, the 

 yellow liquor assumes a greenish hue, and the indigo separates in 

 flakes. The liquor is then allowed to stand for an hour, and the blue 

 pulpy indigo is run into a separate vessel, after which it is pumped 

 up into a pan and boiled, in order to prevent a second fermentation, 

 which would spoil the product by giving rise to a brown matter. 

 The whole is then left to stand for twenty hours, when it is again 

 boiled for three or four hours, after which it is run on to large filters, 

 which are placed over vats of stonework about 7 yards long, 2 yards 

 wide, and 1 yard deep. The filters are made by placing bamboo 

 canes across the vats, covering these with bass mats, and over all 

 stretching strong canvas. The greater part of the indigo remains 

 under the form of a dark blue or nearly black paste, which is intro- 

 duced into small wooden frames having holes at the bottom and 



