TORBANEHILL MINERAL AND OF VARIOUS KINDS OF COAL. 175 



in the direction of the fibres, is with great pains obtained, and examined with a 

 magnifying power of 200 diameters linear, it is then also seen to possess a fibrous 

 structure. (Plate I., fig. 3.) These fibres may be observed to be composed of a 

 reddish-brown coloured substance, in the centre of which is sometimes a dark 

 streak. Oval and elongated transparent masses of a light yellow or reddish-brown 

 colour may also be seen running parallel with the fibres, and here and there are 

 colourless spaces, which strongly reflect light, and which are evidently filled with 

 a crystalline mineral substance. 



On examining a section horizontal to the former one, parallel with the plane 

 of stratification, a bistre-brown or blackish opaque mass is seen, containing a num- 

 ber of rings of a transparent yellowish or reddish colour, with an opaque centre. 

 These rings are from the 1000th to the 1500th of an inch in diameter, and re- 

 semble the transverse sections of tubes running at right angles to the fibres of the 

 coal. (Plate I., figs. 1 and 2.) There may also be observed larger masses of a 

 reddish-brown transparent material, varying in size from the gth to the 250th 

 of an inch in diameter. There are also visible, circles or rings of a rich golden 

 yellow matter, much larger, and varying in size from the 50th to the 6th of an 

 inch, which have been described by some as seeds or spore cases. (Plate I., fig. 1. 

 Plate II., figs. 13 and 14.) 



Similar appearances may be observed in the Wallsend, Newcastle, and all the 

 other household coals I have examined, although in some of them, especially 

 Newcastle coal, this structure is more obscured than in the Scotch coal, by dense 

 black opaque matter. Here and there, however, in the Newcastle as well as in 

 the Hamilton and some other coals, it may be found to present a highly fibrous 

 fracture, minute chips of which exhibit at their edges distinctly dotted or porous 

 ducts. (Plate II., figs. 5, 6, 7, 8, and 9.) 



On examining the Torbanehill mineral with the naked eye, it is destitute of a 

 fibrous structure, and presents a homogeneous appearance in whatever way it is 

 fractured or cut. It is tough and hard to break, when compared with coal, has a 

 dull brown streak, and is readily ground down into thin slices of any degree of 

 tenuity. Some specimens are of a dark, and others of a light brown colour. The 

 section of a dark specimen seen under a magnifying power of 200 diameters, pre- 

 sents, first, a number of yellowish and reddish-brown transparent masses, of a 

 rounded form with an irregular outline, varying in size, from the ^gth to the 

 ^ D th of an inch in diameter (Plate I., fig. 10). These are surrounded by a dark 

 opaque substance, in which they appear to be imbedded, and in which no trace of 

 structure can be detected. These light and dark substances vary in relative 

 amount in different specimens of the mineral, and according to the thickness of 

 the section. In some specimens, the rounded transparent masses are more widely 

 separated, by the opaque substance, but in others, they are often so close, that a 

 very thin section presents a homogeneous appearance of yellowish or reddish- 



