THE TORBANE HILL MINERAL. 



371 



they grew ; always over them an over-clay or roof, or a stratum of 

 sand 01 sandstone — some kind of stratum or other to show they 

 have been covered in. If we bear in mind Mr. Salter's teachings of 

 their origin, we see at once how necessarily these conditions must 

 be associated with true coal-beds. Now the accompanying section 

 will show that while every bed of coal has an under- and an over- 

 stratum, the Torbane hill mineral has neither. No subsoil for the 

 vegetation that formed it to grow in ; no roof of shale or sand 

 to cover in any mass of decaying leaves and tree-stems. 



We well remember the question being discussed at the Geological 

 Society, and the witty reply of poor Edward Forbes, then president, 

 when asked What in his opinion was coal ? " That is a question for 

 my Lord Coke to answer," was far nearer the truth than most people 

 at that moment supposed. In the ash — coke or cinder — of coal 

 there are traces of vegetable structure — the proofs of its origin. In 

 the residue of bituminous shales and petroleums after burning there 

 is no vegetable structure to be seen — a proof that the origin and 

 constitution is not the same. In geology at least the proof of every- 

 thing is in itself, and had coal and all other bituminous subtances a 

 common origin, they would all give the same results. It is interest- 

 ing, then, to consider whether there are not beds of other mineral 

 bituminous substances than coal, the history of which may be not 

 Only entertaining but instructive. For the question naturally arises, 

 If the Torbanehill mineral is not coal, what is it ? Anthracite is 

 fossil coke. It is not coal because it is often called Welsh " coal," 

 any more than coke from the coke-oven is coal. It was coal once, 

 but it has lost its gas, and is not coal now. The Torbane Hill 

 mineral is not anthracite, neither is it culm nor lignite. It may be 

 a shale (we do not even think it is in the proper sense of that word) 

 but shale, however bituminous it may be, is not coal. Shale is a bed 

 of laminated clav, and a bed of clay is not a deposit of vegetable matter^ 

 Kimmeridge shale, highly bituminous as it is, is not coal. Neither 

 can any shale, however impregnated with bitumen, be coal. Are the 

 Caithness flags coal ? " Of course not." And yet they are so highly 

 impregnated with bitumen that they are used for distillation in the 

 same way as the Torbane Hill mineral. Some geologists say the 

 bitumen in the Caithness flags is derived from fossil fish ! True it 



