. 
TORBANEHILL MINERAL AND OF VARIOUS KINDS OF COAL. 183 
of simple ducts, more or less carbonized and condensed together. The deeper the 
peat is taken from the bog, the more condensed, broken up, and altered these 
textures are; still, however, sufficiently retaining their characters to be readily 
distinguishable. The peat of Scotland between this and Glasgow, and that of the 
north of Ireland, of which I have examined numerous specimens, taken from 
mountain bog, as well as the flow bog, are identical in structure. One specimen 
of peat, however, given to me by Dr Trait, which he obtained in Lancashire, 
and which answers in description to what is called Pitch Peat, is blacker in 
colour, the carbonizing process is more complete, and the vegetable tissues less dis- 
tinct. But here and there, in a thin section of this peat, there exist rounded 
masses of the same bituminoid character as are found in the cannel coals and in 
the Torbanehill mineral. This fact confirms the theory formerly advanced, that 
these bodies are not cells, but a concrete bituminoid substance, probably derived 
from the beds of coal in Lancashire, in the immediate neighbourhood of the peat. 
We may therefore conclude that every kind of coal has a distinctly woody 
basis, which is easily demonstrated by its longitudinal and transverse sections ; 
that the cannel coals have, in addition to this woody structure, a greater or less 
‘number of the bituminoid masses imbedded in it; and that the Torbanehill mi- 
neral has no such woody texture, but is essentially composed of the bituminoid 
masses imbedded in clay. 
Ill. In the third place, the theory which I am disposed to put forward as 
' most in harmony with the various facts and arguments previously stated, is as 
follows :—1s?, That-the various organic appearances found in the sections and 
ashes of coal, are explicable by the supposition that coal is wood chemically 
altered, and for the most part coniferous wood, or wood allied to it in structure, 
because, from a careful comparison of recent fir wood with the various kinds of 
coal, I find the structural appearances of the cellular tissue, resin cells, and ducts, 
to be very similar. Further, no fir wood growing in this country contains spiral 
ducts; and it is remarkable that no traces of such ducts are to be found in any 
of the coals I have examined. Further, the assumption that coal is formed from 
fir or allied woods, not only explains its structure, but accounts for the large 
amount of bitumen, resin, or inflammable matter it contains, resin being a well- 
known abundant product of the coniferous tribe of plants.* 
2d, The Torbanehill mineral, although it presents essentially no traces of ve- 
* In the above passage, I have carefully avoided any expression which would suggest the notion 
that in my opinion the wood from which coal is formed, is exclusively coniferous wood. I believe, 
that with regard to the varicties and even genera of the plants of the coal-formation, there is still 
much to be discovered. But so far as my examinations have gone, the appearances observed warrant 
the general inference stated in the text, one which has also been arrived at by Mr Quexetr. (Mic, 
Journal, No. vi, p. 42.) The important fact to be kept in remembrance is, that coal is fossil or 
transformed wood, whilst the Torbanehill mineral, and all the shales which I have examined, are not. 
