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unfavourable to this practice founded upon the 
nature and composition of vegetable substances, 
there are many arguments and facts which show 
that it is prejudicial to the interests of the farmer* 
During the violent fermentation which is neces- 
sary for reducing farm-yard manure to the state in 
which it is called short muck, not only a large 
quantity of fluid, but likewise of gaseous matter 
is lost ; so much so, that the dung is reduced one 
half, or two- thirds in weight ; and the principal 
elastic matter disengaged, is carbonic acid with 
some ammonia ; and both these, if retained by the 
moisture in the soil, as has been stated before, 
are capable of becoming an useful nourishment of 
plants. 
In October, 1 808, I filled a large retort, capable 
of containing three pints of water, with some hot 
fermenting manure, consisting principally of the 
litter and dung of cattle ; I adapted a small re- 
ceiver to the retort, and connected the whole with 
a mercurial pneumatic apparatus, so as to collect 
the condensible and elastic fluids which might rise 
from the dung. The receiver soon became lined 
with dew, and drops began in a few hours to 
trickle down the sides of it. Elastic fluid likewise 
was generated ; in three days 35 cubical inches had 
been formed, which, when analysed, were found to 
contain 21 cubical inches of carbonic acid, the 
remainder was hydrocarbonate mixed with some 
azote, probably no more than existed in the com- 
mon air in the receiver. The fluid matter collected 
in the receiver at the same time amounted to 
