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. Ovaland 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. r 
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 jth to the saoth 
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 IL., 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 IL., 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 ;i,th to the 
aioth of an inch in diameter (Plate L., 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- 
