304 CllYMISTRY APPLIED TO AGRICULTURE. 



At this time, nothing more is necessary than to make 

 known those simple and advantageous methods by which 

 this branch of manufacturing industry may be conducted. 

 I shall however observe, that it is more profitable to the 

 proprietor to extract the indigo from woad, than to convert 

 the leaves of the plant into cakes. 



Plellot assures us that it had been proved in his time, 

 that four pounds of good Guatimala indigo yielded as much 

 coloring matter as a package of Albigense woad cakes 

 weighing two hundred and ten pounds. 



At Quiers, in Piedmont, where the dyers are very skilful, 

 it is calculated that three hundred pounds of the cakes 

 afford as much coloring matter as six pounds of the best 

 indigo.* 



According to the experiments of M. Giobert, there is no 

 doubt that it is more profitable to extract indigo from the 

 woad leaves, than it is to convert them into cakes. 



The indigo which is obtained in America from the anil^ in 

 Indostan from the nuricum, and in Europe from the isatis, 

 does not differ sensibly in character : the care which is 

 taken in the manufacturing of it, and the state of the 

 plants, which many circumstances may cause to vary dur- 

 ing vegetation, can alone produce some changes in its 

 color, and cause its value in commerce to vary. 



This difference in the quality and price of indigo, may 

 arise in some degree from the different methods adopted 

 for extracting it. In America it is made to ferment cold ; 

 in Java in the form of a decoction; and generally in India, 

 since the discoveries of the learned Roxburgh, by infusion. 



Prior to the year 1810, a great number of processes had 

 been employed in France, Germany, Italy, and England, 

 for obtaining indigo from the isatis, without any general 

 method having been established. It was at this period that 

 the French government, urged by the necessity of obtaining 

 a coloring substance which the state of the country would 

 not allow them to import but at a great expense, formed 

 establishments for the extraction of indigo from woad, and 

 offered encouragement to those who would undertake the 

 business. 



I shall not describe all the methods that were practised 

 during the three years following 1810. I shall confine 



These results appear to me exaggerated. I place dependence 

 only on those of the experiments which have been made under my 

 own inspection. 



