238 THE GROWTH OF COAL 



of mineral charcoal prepared in this way are often very beauti- 

 ful microscopic objects under high powers ; and this material of 

 the coal is nothing else than little blocks of rotten wood and 

 fibrous bark, broken up and scattered over the surface of the 

 forming coal bed. All these materials, it must be observed, have 

 been so compressed that the fragments of decayed wood have 

 been flattened into films, the vegetable mould consolidated into 

 a stony mass, and trunks of great trees converted by enormous 

 pressure into laminae of shining coal, a tenth of an inch in thick- 

 ness, so that the whole material has been reduced to perhaps 

 one-hundredth of its original volume. 



Restoring the mass in imagination to its original state, what 

 do we find ? A congeries of prostate trunks with their interstices 

 filled with vegetable muck or mould, and occasional surfaces 

 where rotten wood, disintegrated into fragments, was washed 

 about in local floods or rain storms, and thus thrown over the 

 surface. Lyell seems very nearly to have hit the mark when 

 he regarded the conditions of the great dismal swamp of 

 Virginia as representing those of a nascent coal field. We 

 have only to realize in the coal period the existence of a dense 

 vegetation very different from that of modern Virginia, of a 

 humid and mild climate, and of a vast extension of low 

 swampy plains, to restore the exact conditions of the coal 

 swamps. 



But how does this correspond with the facts observed in 

 mines and sections ? To the late Sir William Logan is due the 

 merit of observing that in South Wales the underclays or beds 

 of indurated clay and earth underlying the coal seams are 

 usually filled with the long cylindrical rootlets and branching 

 roots of a curious plant, very common in the coal formation, 

 the Stigmaria. He afterwards showed that the same fact 

 occurs in the very numerous coal beds exposed in the fine 

 section cut by the tides of the Bay of Fundy, in the coal rocks 

 of Nova Scotia. In that district I have myself followed up 



