INDIGO.

449

the plant and gathered, but in most cases the entire plant is cut down close tothe ground about the months of June or July, when the few flower buds left beginto open. The roots left in the soil soon sprout again, producing a second andeven in some instances a third and fourth crop of the shrub, but in each casethe quality of the product becomes weaker both in quantity and quality. Theplants when cut down are colleded in bundles and brought to the fadory beforeevening, so that they may be operated upon at once.

M. Kcechlin-Schwartz* has published an interesting account of the manu-fadure of indigo as carried on in Lower Bengal. The following is an abstractof that paper:—Lower Bengal is renowned for the excellent quality of itsindigo, and the fadories are among the best which exist as regard all arrange-ments, containing filters, presses, cauldrons, and boilers; drying rooms, largewater tanks, and, lastly, the very essential tanks for the extradion of theleaves by means of water. These tanks are placed in two rows, containingfrom 15 to 20 each, one row being placed higher than the other. The tanksare built firmly of brickwork, lined inside with a strong cement; their shapeis redangular, about 6 metres by 6-5, and from 0*9 to i*o metre in depth ; theuppermost row of tanks is placed about o*g metre higher than the lowerrange. The tanks of the upper range serve for the purpose of the fermen-tation of the plant.

Pure water in large and almost unlimited quantity is an absolute requisiteof an indigo fadory, and in this resped the situation on or near the Ganges isof great importance; the water of that river is relatively very pure, and inorder to cause the deposition of suspended matter it is brought by conduitsinto large ponds, and, after having become clarified, is conduded to largetanks, which are on the same level with the masonry tanks just described.The plant being cut down in the forenoon is delivered in neatly made-upbundles at the fadory in the afternoon. The bundles are placed neatly in thetanks, each containing 100 thereof, and care is taken to pack them tightly,while they are prevented from floating by the placing of stout pieces of timberacross the tank tightly wedged. It is essential that there should be left aslittle open space as possible to ensure the proper progress of the fermentation.As soon as the tanks are filled with bundles a sluice valve is opened, whichcauses the water to run in, and so to fill them that the bundles are entirely sub-merged. The process of fermentation goes on more or less slowly, accordingto the prevailing temperature, but it lasts on an average from nine to fourteenhours. The progress of the operation is considered good when a smallquantity of the liquid from the fermenting tanks, run off into the tanks of thelower row, exhibits a straw colour; for although the quantity of the produdwill in that case be rather less abundant, the quality will be better than if thecolour of the liquor be golden-yellow, and a turbidity be apparent at the sametime. When the liquor is run off from the fermenting tanks its colour is moreor less yellow ; after having been left at rest for a few moments twelve nakedmen descend into the tanks and begin to stir the water very vigorously,while at the same time the fermenting tanks are emptied, cleaned, and madeready for another operation. The operation of stirring and beating the wateris continued for several hours, there being seventeen workpeople, viz., twelvemen and five women, employed to each tank. While this operation is going

* “ Bulletin de la Socide Industrielle de Mulhouse,” vol. xxviii., p. 307.