178 DR BENNETT ON THE STRUCTURE OF THE 
that any histologist who has made himself acquainted with the structure of coal 
on the one hand, and of the Torbanehill mineral on the other, could easily con- 
found the two together. 
There are two other modes of examination which also indicate the broad dis- 
tinction in structure between coal and the mineral. These are by reducing them 
to powder and to an ash. 
The powder of household coal contains numerous short black fibres, separated 
or aggregated together, mingled with mineral particles and fragments of cells. 
That ofthe Torbanehill mineral is composed of transparent yellowish masses, 
evidently the same as those seen in section, but more broken up, and without any 
trace of an envelope, mingled with fragments and the debris of the dark amorphous 
mineral matter. This mode of examination, though distinctive between the 
household coals and the mineral, is not so much so, when the brown Methil coal 
is chosen as the subject of comparison. 
An examination of the‘ash, however, is still more characteristic. In the brown 
or blackish ashes of coals will be found, 1sé, A greater or less number of mineral 
spicula, evidently the skeletons of the woody fibre ; 2d, Siliceous masses of various 
irregular forms, obtained from the interstices of the organic substance; 3d, Black 
fibres, separated or in masses, evidently the woody fibre carbonized; 4th, Flat 
carbonaceous plates, presenting round apertures corresponding in size to the 
woody cells which passed through them, and exhibiting at their margins sections 
of larger circles, which doubtless bounded the large resin cells in the recent wood. 
(Plate IL., fig. 3). None of these appearances are visible in the ash of the Torbane- 
hill mineral, when care is'taken to exclude such portions of it as are free from the 
stigmaria or other plants imbedded in it. Indeed I myself have never seen such 
appearances in the ash, even when no such precaution has been taken. Dr GrorGE 
Witson gave me a considerable quantity of it, which everywhere exhibited 
nothing but an amorphous material, such as might result from the incineration 
of clay or other earthy non-organic substance. (Plate IL. fig. 4). In all the 
cannel coals, traces of these forms, though not so numerous or abundant, can be 
seen. Mr Qurexerr has even applied this test to Welsh anthracite, in which 
substance no rings or fibrous structure can be made out in sections, yet where he 
says, the ash gives unmistakable evidence of the presence of woody tissue.* 
II. Such, then, are the facts which an investigation into the structure of coals 
the one hand, and of the Torbanehill mineral on the other, has elicited. If the 
account I have given of them be correct, it must be evident that the differences 
* Quarterly Journal of Microscopical Science, No. VI., p. 48. This number of the Journal for 
January 1854, was not published until February, after the present paper was written. I was enabled 
however, by the kindness of Mr Hicutey, the publisher, to peruse a proof of Mr Qurkerry’s valuable 
paper, before my own was read to the Society, and to interpolate the above passage. 
