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Art. VIII . — On Peat By John MacCulloch, M. D. 
M. G. S. Lecturer on Chemistry to the Board of Ordnance, 
&c. Communicated by the Author. 
So much has already been written on this interesting sub- 
stance, that it is scarcely possible at the present day to add any 
thing to the history of its origin, or to the description of its va- 
rious appearances. The natural history of peat has perhaps, on 
the contrary, been occasionally rendered somewhat obscure by 
superfluity of discussion, while its chemical nature has either 
been misapprehended, or involved in mystery, from causes 
which need not here be noticed, but which will be sufficiently 
apparent to those who may be inclined to read all that has been 
written on this subject. It does not appear difficult to place the 
latter in a more intelligible light, by recurring to a few simple 
principles, in which some interesting analogies are also involved ; 
while the former may perhaps also be simplified by a condensa- 
tion and arrangement of the facts which are obvious to the exa- 
mination of all, and which have been more or less accurately 
described by numerous observers. A sketch of the natural 
history of this substance is at any rate an indispensable prelimi- 
nary to the few observations which it is here proposed to offer 
on its chemical nature. 
The concurrence of a certain degree of moisture, and of a 
moderate temperature, appears necessary to regulate the decom^ 
position of vegetables, so as to lead to the formation of peat. 
But the first condition admits of great latitude, as it is formed 
not only under water, but on drained declivities, in situations 
and climates that are subject to a very moderate proportion of 
rain. It is also produced under a great range of temperature ; 
but the observations hitherto recorded, have not enabled us to 
determine at what degree of heat it ceases to be generated. It 
is merely known, that in warm climates the decomposition of ve^ 
getables is so rapid, as to prevent its formation ; and that, in 
these, it is therefore found only at high elevations, while, in the 
cold and temperate climates, it abounds even at the level of the sea» 
