AGRICULTURE AND PLANTING. 23 



On the component Principles of Vegetables. 



X. Concerning Alkalis. 



The alkaline principle of vegetables is of three kinds, namely, ammoniac, 

 soda, and potash. The former resides in volatile or ethereal oils, and most nas- 

 turcine plants ; for it is obtained during distillation by the addition of tlie car- 

 bonate of potash or fxed alkali. Soda is present in the ashes of all maritime 

 plants; and potash is obtained frorh the ashes of plants not maritime. 



The neutral salts from the vegetable kingdom, are various. The hyosciamus, 

 borago, nicotiana, helianthus annuus, mesembryanthemum crystallinum, millefoli- 

 um, and fumaria, afford nitrate of potash. The tamarindus gallica, th6 sulphat of 

 soda. The muriate of soda is obtained from the salicornea herbacea, from the 

 leaves of the american tree called cerciba, which abounds so much with it, that 

 one leaf is sufficient to salt a sallad. There- are also plants of this nature grow- 

 ing in the province of Jago, which is far distant from the sea; and what is 

 tv^onderful, not a particle of salt can be obtained from the soil, in which they 

 grow. The cinders' of many vegetables afford the sulphat of potash* 

 XI. Concerning the Colcturing Principles. 



The object of the art of dying consists in depriving one body of its colour- 

 ing principle, to fix it upon another in a durable manner; and the series of ma- 

 nipulations necessary to produce this effect, constitutes the art itself. This art 

 is one of the most useful and wonderful of any we are acquainted with ; and if 

 there be any one of the arts which is capable of inspiring a noble pride, it is 

 this. It not only affords the means of imitating nature in the riches and bril- 

 liancy of her vegetable colours ; but it appears to have surpassed her, in giving 

 a greater degree of brilliancy, fixity, and solidity to the fugacious and transient 

 colours with which she has clothed the productions around us. 



All vegetables afford the colouring principle ; it therefore must be very 

 various. The art of dying depends upon the knowledge of tliis principle. If the 

 stalk of the indigofera tinctoria, or indigo plant, be macerated in water, it af- 

 fords, by precipitating the fseculum, a beautiful blue colour, called indjgo. It 



