Dr MacCulloch on Peat 
m 
bable that, where tan is held in solution, a portion of gallic acid 
may also occasionally be dissolved ; but it is nearly impossible 
to put these subjects to the test of direct experiment, from the 
difficulty of procuring solutions of peat in a state fit for such ac- 
curate examination. The acid which may be extracted from 
peat, by decoction in water, is small in quantity, and appears ra- 
ther to be generated by the same process which converts the ve- 
getable fibre into peat. It will hereafter be seen, that when ve- 
getable matter is exposed to heat, the carbon and hydrogen en- 
ter, together with portions of the other vegetable elements, in- 
to new compounds, some of which are partially soluble in water. 
A familiar instance of this occurs in the roasting of coffee. Du- 
ring this process a portion of acid is also generated, which, on 
pushing the process to extremity, forms a conspicuous part of 
the result of the destructive distillation of vegetable matter. 
The action of water on vegetables, in the case of peat, as in that 
of manure, produces hydro-carbonaceous compounds of an ana- 
logous nature, some of which are similarly soluble in water, 
while others form insoluble peat ; and it appears a necessary con- 
sequence that, in this process also, acetic acid should be generat- 
ed. The acid extracted from peat is in fact acetic acid, but the 
time required to conduct a direct experiment of this nature, so 
as to produce a decided result, is such as to prevent the possi- 
bility of instituting any for that purpose. 
The soluble hydro-carbonaceous compound which communi- 
cates the brown colour to peat water, resembles, when obtained 
in a state of purity, that which is generated by the decomposi- 
tion of manure, (abstracting the salts which abound in this,) as 
well as that which is produced by roasting coffee, or by the ap- 
plication of a regulated heat to other vegetable matters. It is 
like that also which, in highly terrified malt, or in sugar, com- 
municates the brown colour to malt liquors. It is probable that, 
in all these cases, this compound is subject to considerable varia- 
tions ; but chemistry as yet offers no certain methods of accurate- 
ly distinguishing these. Distillation, which separates the hydrogen 
and other volatile matters from the carbon, proves differences, the 
exact degree of which it does not enable us easily to appreciate. 
This compound, as it is deposited naturally from peat waters, 
is sometimes found in bogs in such quantity as to admit of ready 
