384 COMPOUND PRODUCTS. CHAP. I. 



ferent plans. Rouelle founded his arrangement 

 upon the manner of analysis, according as the in- 

 gredients were obtained by means of fire, water, 

 oils, or alcohol. But this circumstance is of too 

 little importance to sanction its application. Bucquet 

 founded his arrangement upon the situation of the 

 several ingredients, as obtained from the root, bark, 

 fruit, or seed. But this plan is liable to the same 

 objection with the former, as presenting no com- 

 parative view of the properties of the substances ar- 

 ranged. To remedy this defect the medical or 

 dietetical properties of the ingredients obtained 

 were then adopted as the ground of arrangement ; 

 which plan, though it has its utility no doubt with 

 respect to its application to science, is not itself 

 sufficiently scientific. A better method is that by 

 which they are arranged according to their chemi- 

 cal properties, as consisting of oils, acids, alkalies, 

 &c. ; or according to some essential characteristic, 

 distinguishing them from one another, and consist- 

 ing either in the colour, taste, or odour ; or in the 

 texture of the parts, as constituting fluids or solids. 

 But the best and most philosophical method of all, 

 and that which supposes the greatest degree of ad- 

 vancement in the science, is that by which they are 

 arranged in the order of their formation or deve* 

 lopement in the plant itself. This is to follow the 

 order of nature ; though it would no doubt require 

 a greater degree of knowledge in vegetable chemis- 

 try, than chemists at present'possess, to render the 



