86 Dr Colquhoun o?^ the Argillaceous Ore of Iron. 



tion to separate into rectangular fragments, and it is harder, 

 much more compact, and much more difficultly fra^.gible than 

 the cherry coal. 



The splint coal is in many cases considerably injured by 

 being very unequal and diversified ; so much so that the same 

 mass has frequently the appearance of being composed of a suc- 

 cession of distinct layers. Most of these layers are of a dull 

 earthy aspect, but they sometimes alternate with others which 

 possess the splendour that characterizes the cherry coal. The 

 splint coal frequently contains also thin, interrupted layers of 

 an incoherent shining substance resembling pounded wood char- 

 coal, which crumbles to a powder on the slightest pressure. It 

 is found to occur most frequently between the surfaces of any 

 two substrata of the coal, which, while they differ more or less 

 from each other in composition and appearance, are laid in 

 juxtaposition to each other in the general stratum. It is de- 

 posited along the' longitudinal fracture of the coal, in a layer 

 whose thickness in general does not exceed that of a common 

 wafer, or of writing paper, though it occasionally amounts to 

 the eighth part of an inch. The existence of this interposed 

 substance is always injurious to the coal in which it is present 

 to any extent, for it disturbs the cohesion and continuity of 

 those two surfaces of the mineral between which it lies, and of 

 course gives to the coal, especially after being coked, a ten- 

 dency to shiver and fall in pieces by splitting up in the direc- 

 tion in which it runs. 



The splint coal yields a coke which possesses in very great 

 perfection all those properties which are most essential to its 

 utility in the smelting of iron. Although it originally contains 

 a large quantity of bituminous and volatilizable matter, it is 

 much less subject to agglutination during the coking process, 

 than the cherry coal. The coke obtained from it is hard, dense, 

 heavy, and difficultly frangible. It emits a clear ringing sound 

 when struck. It is so compact in its graiir that, even when its 

 continuity is broken by wide and numerous rents, as is too often 

 the case, it remains still capable of enduring pretty rude treat- 

 ment without being thereby shivered or split. This is there- 

 fore the coal upon which the ironsmelters of Scotland at prew 

 sent place their chief reliance. . iiiri i jj . 



