Dr MacCulloch on Peat 
211 
of this change, since they contain a portion of bituminous mat- 
ter soluble in naphtha, and it is undoubted that they owe this 
change to the action of water. 
If peat which has undergone a commencement of bituminiza- 
tion be distilled, so as to separate the oil, it will be found that this 
is partially soluble in naphtha. Submerged wood, according to 
its condition, gives similar results, the specimens sometimes 
yielding ordinary tar, at others a mixture of tar and petroleum. 
In peat, the process stops thus at the outset ; but, in submer- 
ged wood, it proceeds indefinitely. Thus Bovey (brown) coal 
gives out a mixture of these two products, in which the petro- 
leum bears a conspicuous proportion. The surturbrand of Sus- 
sex produces similar results ; but in both these cases, different 
proportions of petroleum seem to be procured from different 
specimens, according to the varying degree to which the process 
of bituminization has advanced. In jet, it is difficult to ascer- 
tain whether the products differ ftom those which are obtained 
from asphaltura or from coal ; but in the few trials made with 
this view, the proportion of acid appeared to be greater in the 
former than in the latter case. Should this be the fact, the 
bituminization, even of jet, must be considered as incomplete, 
and it will probably be found to yield a small proportion of tar, 
or of the oil of wood. 
From a consideration of all these circumstances, there seems 
no reason to doubt that peat is a substance intermediate between 
common vegetable matter and bituminous lignite, and that it is 
capable of undergoing the ultimate change, when all the requi- 
site conditions are present. It equally follows, that as the action 
of water is capable of producing the incipient change, there is 
no reason to doubt that it may effect the ultimate one. This is 
indeed confirmed by the geological situation of brown coal, of 
surturbrand, and of jet, all of which occur in alluvial soils. In 
peat, time alone seems wanting to complete the process. The 
history of its formation, already given, proves that it is rarely 
of a distant origin ; and, in those cases in which it shews marks 
of bituminization, it will probably be found that its antiquity is 
the highest. The bituminous lignites are always found buried 
under alluvial soil, sometimes of considerable depth ; a circum- 
stance generally sufficient to indicate a longer period of expo- 
