44 
ON CHEMISTRY. 
and abundance of carbonate (chalk) ? and yet these multifarious 
products, and several other substances, are discoverable in most of 
the residue of Vegetable combustion/ In a word, this process, which 
is generally considered a work of destruction, terminates in a new ar¬ 
rangement of the vegetable elements, and produces matters which 
much resemble the staple earths that have been described in the last 
chemical article. 
These facts irresistibly lead to the conclusion that, all manuring 
substances deposited in the ground, are eventually converted into 
earths, but in a way and proportion) varying according to the circum¬ 
stances under which they are exposed, to the decomposing energy of 
the agents which surround them. 
Before I enter upon the second subject of this article,—the Pre¬ 
paration of vegetable food—I must observe, for the information of 
those who cannot undertake an experiment, for the detection of the 
elements of fermentative substances, in close vessels, that any vege¬ 
table matter, if burnt, will afford satisfactory evidence of the earthy 
nature of the matters, left in the form of ashes. Let any quantity of 
dry potatoe or pea-haulm, fern-leaves, bean stalks, tree leaves, or 
even wood be burnt, and the ashes collected : a drachm, or 60 grains 
will suffice for an experiment. First, put the ashes into a cup, then 
pour a quantity of boiling rain-water upon them : stir them once or 
twice, and, when cool, strain the liquor through paper. The soluble 
salts are contained in this, and they frequently exhibit alkaline proper¬ 
ties, which are discoverable even by the taste. Fern yields potash 
in quantity sufficient to form a lye for washing. Upon the washed 
ashes in the cup, pour a little muriatic acid; a considerable hissing 
(effervescence) will take place. The solution will contain muriate of 
iron and muriate of lime : the effervescence is occasioned by the 
escape of carbonic acid gas. Prussiate of potassa will detect the 
iron ; and subsequently carbonate of potassa or soda, will precipitate 
the lime, in the form of a milk white powder. Second—The remains 
of the ashes, may now be washed till free from flavor, and tested by 
a few drops of diluted sulphuric acid; and if the vessel be subjected 
to a boiling heat for an hour or two, a little alumine will often be 
taken up, and more iron. Finally, the substance remaining, which 
cannot be acted upon by the two powerful acids, must be considered 
siliceous, or of the nature of sharp sand. I do not describe the me¬ 
thod of effecting these trials, having already done so in the last arti¬ 
cle upon the Analysis of soils . I have detected every one of these 
staple earths, in the ashes which collect by burning common cigars; 
also in those of a bread-oven, heated by furze and common faggots. 
