MADDER. 351 



scriptions of root are kept separate in the drying- 

 house, where they are left for four or five days, being 

 turned once or twice during that time, in order that 

 they may dry equably, and that the earth adhering 

 to them may be rubbed off. They are then con- 

 veyed to kilns constructed for the purpose, where 

 they are still farther dried. When the roots are 

 sufficiently dried outwardly they are removed to a 

 floor made as clean as possible, and the outer skin is 

 then separated by means of thrashing. 



This skin is pulverized by itself and packed up in 

 separate casks. It is known in commerce by the 

 name of mull, and being extremely inferior to the 

 other part, is sold at a comparatively very low price. 



After the outer skin is thus separated, the roots 

 are again conveyed to the kiln and subjected to a 

 greater degree of heat than before. That this heat 

 may not be injurious to the roots, they are frequently 

 turned and a current of fresh air is blown through 

 the kiln, to carry off the noxious exhalations of the 

 plant, which would otherwise injure the colour. 

 When the roots are sufficiently dried, they are con- 

 veyed to the pounding-house to be reduced to 

 powder. 



In warm climates madder is prepared without the 

 application of artificial heat. It results from this 

 difference of preparation, and perhaps also from the 

 variety of the plant, that two kinds of madder are dis- 

 tinguished, which differ in their dyeing properties *. 



The roots are ground either between mill-stones 

 or under knives similar to those of a tan-bark-mill. 

 After the first milling the impurities are separated 

 by means of boulters or fanners. In this state it is 

 so partially cleansed that the French call it non-robee, 

 the residuum consists of earthy matter, epidermis, 

 and bark. 



* Berthollet. 



