196 DR. BENNETT, ON THE STRUCTURE OF 



bundles of simple ducts, more or less carbonized and con- 

 densed 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. Traill, which 

 he obtained in Lancashire, and which answers in description 

 to what is called Pitch Peat, is blacker in colour, the carbo- 

 nizing process is more complete, and the vegetable tissues less 

 distinct. 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, pro- 

 bably 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 mineral has no such woody texture, but is essen- 

 tially composed of the bituminoid masses imbedded in clay. 



in. 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 : — 1st, That the 

 various organic appearances found in the sections and ashes 

 of coal ai'e 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 compa- 

 rison 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 inflamma- 

 ble matter it contains, resin being a well-known abundant 

 product of the coniferous tribe of plants.* 



* In the above passage, I have carefully avoided any expression which 

 would s\iggest the notion that in my opinion the wood from which coal is 

 formed, is exclusively coniferous wood. I believe that., with regard to the 



