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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 vege- 
tables 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 
