90^ Dr MacCulloch oii Peat. 
nites ; since, through this latter stage, it must pass in its tran- 
sition from the vegetable to the mineral class of substances. 
This question is more or less remotely connected with a very in- 
teresting train of geological inquiries. Peat has in fact been 
confounded with the bituminated vegetables, and has been sup- 
posed to derive its inflammable quality from the formation of 
bitumen during the process by which it has been generated. It 
will, however, be found, on a more strict investigation, that 
fliere is an essential distinction between common peat and bitu- 
minized wood, and that even when it does show some of the cha- 
racteristic marks of the bitumens, the degree in which it has un- 
dergone this change is very limited. The Ince peat of Lanca- 
shire appears unquestionably to be accidentally penetrated by 
petroleum, derived from the usual source of a bituminous 
spring. 
Although in a practical view, therefore, peat may be consi- 
dered as an indefinite substance, and in a state of transition to 
bituminized vegetable matter, it is convenient for the present 
purpose to divide the process from the death of the vegetable 
to its bituminization, into two stages. The first of these com- 
prises the change into mere peat, in which no traces of bitumen 
can be discovered, and the last may be conceived to extend 
from the time at which it first gives tra^s of this substance, to 
that in which the characters of peat have been replaced by those 
of bituminized wood. It will shortly be seen, that we are in 
possession of chemical means, by which pure bitumen can be 
distinguished from pure peat, or from that substance which 
constitutes its essence ; and the application of the same powers 
enables us, although less perfectly, to distinguish that state to 
which alone the name of Peat should, for the sake of accuracy, 
be applied, from that in which the process of bituminization has 
commenced. 
The powers of chemical analysis are as yet so limited, that 
we have no means of examining directly the differences of the 
various substances which are found throughout the whole of 
these changes, from the simple vegetable matter downwards ; or, 
at least, the results which are obtained from the application of 
these means, are imperfect and unsatisfactory. But considerable 
light may be thrown on the subject, by that operation former- 
