118 DR. EEDFERN, ON THE TORBANEHILL 



The appearance of the sections to which heat has been 

 applied is quite sufficient to determine the fact that the gas- 

 giving power of this coal depends upon the yellow matter, the 

 amount of which is indicated generally by the light colour of 

 the coal. No coal is so yellow as this in thin sections, and 

 there is none which approaches it in gas-giving power. 

 Torbanehill coal produces 15,000 cubic feet of gas per ton, 

 and the best of the other known coals will not yield more than 

 12,000 cubic feet per ton. It may be suggested, that the dark 

 boundaries of the spaces from which the yellow matter has 

 been driven off by heat consist of earthy matter ; but I think 

 no one would arrive at that conclusion who had tested their 

 strength by pressure and friction between two glasses when 

 the preparation was immersed in viscid balsam. I do not 

 doubt that the earthy matter has been left by the heat with 

 the free carbon of the texture, and I think the absence of all 

 crystalline or other obvious earthy particles in the middle 

 and lower portions of the seam sufficient proof that the 

 18 per cent, of earthy matter which chemistry proves to be 

 present in the coal has got there in a state of solution, or of 

 fine molecular subdivision. 



Now, what conclusions can be drawn from these facts as to 

 the nature of the yellow spots ? They are more or less circular, 

 flattened, solid bodies, containing a large portion of the gas- 

 giving substance of the coal, and bounded by vegetable fibres 

 and membranes often in a fragmentary state. Heat drives off 

 their yellow matter in the shape of gas, and shows in their 

 very substance polygonal cavities with definite walls, where, 

 without heat, such cavities and septa could not have been 

 supposed to exist. I cannot explain the nature of these bodies 

 otherwise than by supposing them to have had their origin in 

 a mass of vegetable cells and tissues which have been disin- 

 tegrated and otherwise changed by maceration, pressure, and 

 chemical action, and subsequently solidified. Moreover, 

 exactly similar bodies make up a large portion of cannel 

 coals generally. I would especially refer to the Wemyss, 

 Methill,Capledrae, andRochsoles coals. Of these the Wemyss 

 coal is especially remarkable in showing the radiate striation 

 of the yellow masses of the Torbanehill coal ; and, if I am 

 not greatly mistaken, it demonstrates a clear relation between 

 the yellow bodies just named, and the dark rings of horizontal 

 sections of Lesmahago, Kinneil, Lochgelly, Wigan, and other 

 cannels, which have been described as transverse sections of 

 vessels or fibres. 



But there are smaller and more regular yellow spaces, 

 having far more definite walls, sometimes double (Plate VIL, 



