THE TORBANEHILL MINERAL, ETC. 187 



establish the entire absence of connexion between these sub- 

 stances and the Torbanehill mineral. 



In now endeavouring to place in a condensed form the 

 results of this extended investigation before the Society, I 

 propose, in the first place, to describe the facts, as they may 

 be easily demonstrated in the field of the microscope. 

 Secondly, to deduce from these facts the structural element 

 which distinguishes every kind of coal from the Torbanehill 

 mineral, and explain the cause of the differences which are 

 recorded in the proceedings of the recent trial. Lastly, to 

 offer a few speculations as to the nature of this mineral, as dis- 

 tinguished from various kinds of household and cannel coals. 



I. When we examine a piece of undoubted coal, such as of 

 the Zetland or Buccleuch coals, it presents to the naked eye a 

 fibrous structure, and has a black shining streak. It has been 

 found difficult to make thin sections of it, as in the grinding 

 process it readily crumbles down. But when a tolerably thin 

 slice, made 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 struc- 

 ture. 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 j^ellow 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 nuinber 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 resemble the transverse sections of tubes 

 running at right angles to the fibres of the coal. There may 

 also be observed larger masses of a reddish-brown transparent 

 material, varying in size from the |th to the g^Joth 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. 



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 New- 

 castle as well as in the Hamilton and some other coals, it may 



