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offer in the fairest point of view. I shall, therefore, in the first 

 place, describe these substances, and particularize the circumstances 

 attendant on their discovery, and then shall endeavour to point out 

 the nature of these various modifications of vegetable matter, and 

 the different processes on which they depend. 



But, previously to entering into a particular examination of the 

 changes which take place in vegetables, in the several processes to 

 which they are subjected, whilst passing into a state of mineraliza- 

 tion; it is necessary to give some slight account of the substances 

 of which they are composed, during their vegetable state ; and of 

 such chemical changes as appear to be subservient to the offices of 

 vegetation. 



Vegetables, besides containing oils, acids, alkalies, earths, and 

 metals, in common with substances of the animal and mineral king- 

 doms, do also contain the following substances, which are peculiar 

 to the subjects of the vegetable kingdom : Starch, gum, sugar, 

 extract, tannin, wax, resins, camphor, caoutchouc, wood, cork. 

 The analysis of these substances manifest, that oxygen, carbon, and 

 hydrogen, entering into a triple combination, constitute, with some 

 of the earths, the greatest part of their mass. In several of these 

 substances, nitrogen is also found to exist ; and in some, sulphur 

 has been found. Phosphates of lime, &c. have likewise been 

 found in the analysis of some vegetables: the phosphoric acid 

 having been, probably, derived from the phosphorus yielded by the 

 decomposition of animal matters, in the soil in which these vegeta- 

 bles grew. 



Water was once supposed to be the chief, if not the sole, food of 

 plants. This opinion has been long doubted; but the ingenious 

 experiments of Hassenfratz have furnished us with additional means 

 of solving this interesting question. It appears, that the water does 

 not add to the stock of carbon, so necessary to the growth of the 

 plants but only serves for the diffusion of that which the bulb origi- 



