The Origin and Rslations of the Carljon Minerah. 271 



[Note. — In this diagram, the vertical line connecting the 

 names of the residual products (and of the derivatives of petro- 

 leum) indicates that each succeeding one is produced by farther 

 alteration from that which precedes it, and not independently. 

 Also, the arrangement of the braces is designed to show that 

 any or all of the evolved products are given ofl: at each stage of 

 alteration.] 



The theory here propo-ed has not been evolved from my in- 

 ner consciousness, but has grown from careful study, through 

 many years, of facts in the field. A brief sketch of the evidence 

 in favor of it is all that we have space for here. 



Residcal Products. 



Peat. — Dry plant-tissue consists of about 50 per cent, of car- 

 bon, 44 per cent, of oxygen, with a little nitrogen, and 6 per 

 cent, of hydrogen. In a peat-bog, Ave find the uj^per part of the 

 scale represented above very Avell shown ; plants are growing on 

 the surface with the normal composition of cellulose. The 

 first stratum of peat consists of browned and partially decom- 

 posed plant-tissue, Avhich is found to have lost perhaps 20 per 

 cent, of the components of wood, and to have acquired an in- 

 creasing ]~iercentage of carbon. As we descend in the peat, it 

 becomes more homogeneous and darker, until at the bottom of 

 the marsh, ten or twenty feet from the surface, we have a black 

 carbonaceous paste which, when dried, resembles some varieties 

 of coal, and a])proaclies them in composition. It has lost half 

 the substance of the original plant, and shows a marked increase 

 in the relative proportion of carbon. 



Lignite. — Each inch in vertical thickness of the peat-bog re- 

 presents a phase in the progressive change from wood-tissue to 

 lignite, using this term with its common signification, to indi- 

 cate, not necessarily carbonized ligneous tissue, but plant-tissue 

 that belongs to a j)ast though modern geological age ; i. e., Ter- 

 tiary, Cretaceous, Jurassic, or Triassic. These lignites or mod- 

 ern coals ai'e only peat-beds which have been buried for a longer 

 or shorter time under clay, sand or solidified rock, and have pro- 

 gressed farther or less far on the road to coal. As with peats, so 



