818 COAL 



shales or " roof " of the coal, ferns and trunks of trees abound, without any stigmaria, 

 and are flattened and compressed, those singular plants of the underclay (the stigmarue) 

 very often retain their natural forms of brandling freely, sending out their slender 

 leaf-like rootlets, formerly thought to be leaves, through the mud in all directions.' 

 This plant is singularly indicative of the class of plants from which coal has been 

 derived. 



M. Adolph Brongniart states that the number of species of carboniferous plants 

 amounts to about 500. Lindloy informs us that no less than 250 ferns have been ob- 

 tained from the coal-strata. Forty species of fossil plants of the coal period have been 

 referred to the Lepidodendrons. These with Equisetacea, Catamites, Asterophyllites, 

 SigiUaria, of which about thirty -five species are known with their roots, Stiginarite, 

 and Conifera make up the remarkable flora which have been preserved to us in our 

 coal series. 



Trees and humbler plants in great variety are found in the carboniferous sand- 

 stones and shales, and in the coal itself; but it does not appear that we have any one 

 evidence of the actual conversion of the woody fibre of these plants into coal ; that is, 

 there is no evidence of the direct conversion of wood into bituminous coal. The 

 trees are almost invariably silicified, or converted into columns of sandstone ; the 

 carbon which constituted the original woody fibre being substituted by silica, or 

 sometimes by carbonate of lime, and sometimes by iron. Sir Charles Lyell has care- 

 fully examined the phenomena, now in progress, of the great Delta of the Mississippi, 

 and he perceives in them many facts which fully explain, to his mind, the progress 

 of coal deposit. It cannot, however, be disguised that even while he refers the 

 coal to the supposed submerged forests, he does not venture to explain any of those 

 changes, which he evidently believes depend upon some peculiar conditions of climate. 



Professor John Phillips, who has devoted much study to this subject, says, ' There 

 is no necessity to enlarge upon the proofs of the origin of coal from vegetables, drawn 

 from an examination of its chemical constitution, as compared with the vegetable pro- 

 ducts, and the composition of the ligneous parts of the plants, and from the unanswerable 

 identity of the carbonaceous substance, into which a vast multitude of fossil plants have 

 been converted. The chemical constitution of this carbonaceous product of the indivi- 

 dual vegetables, is exactly analogous to the chemical constitution of coal ; and it is 

 quite probiible that hereafter the reason of the variations to which both are subject, 

 whether dependent on the original nature of the plant or produced by unequal expo- 

 sure to decay after inhumation, or metamorphic subsequent operations, will be as 

 apparent as that of the general argument arising from a common vegetable origin.' 

 Manual of Geology. 



Mr. Jukes says, 'If therefore, we suppose wood (or vegetable matter) buried 

 under accumulations of more or less porous rock, such as sandstone and shale, so 

 that it might rot and decompose, and some of its elements enter into new combinations, 

 always using up a greater quantity of oxygen and nitrogen than of carbon and hydrogen, 

 or of oxygen and hydrogen than of carbon, we should have the exact conditions for 

 the transformation of vegetable matter into coal.' Thf. Student's Manual of Geology. 



Much stress has been laid upon the fact that we have brown coal still retaining 

 all the unmistakable characters of wood, and the apparent passage of this into true 

 coal. 



' Goppert states that the timber in the coal-mines of Charlottenbrunn is sometimes 

 converted into brown coal. The same conversion was many years ago found in an 

 old gallery of an iron-mine at Turrach in Styria. A. Schrotter explains, according to 

 the analysis made by him, this conversion, by the separation of marsh gas and car- 

 bonic acid from the ligneous fibre of oak wood.' JBischof. 



The same authority says, ' This conversion of wood into coal may take place in four 

 different ways, namely : 



' 1. By the separation of carbonic acid and carburetted hydrogen. 



2. carbonic acid and water. 



3. carburetted hydrogen and water. 



4. carbonic acid, carburettod hydrogen and water.' 



Quoting the information accumulated by Bischof for the purpose of showing the 

 chemical changes which take place, the following analyses (see Table at top of next 

 page) are given. 



Such is, in the main, the evidence brought forward in support of the view that coal 

 is the result of the decomposition, upon the place where it is found, of woody fibre. 

 The following remarks by Professor Henry Kogors on the structure of the Appalachian 

 coal exhibits some of the difficulties which surround this view : 



'Each bed is made up of innumerable very thin laminae of glossy coal, alternating 



