PALEOZOIC TIME — CARBONIC. 713 



bark of Quercus sicber) ; (3) the spores of Lycopods ; (4, 5, 6) the common 

 kinds of mineral coal; and (7) peat or vegetable material, partly altered 

 to the coal-like condition. 



I. Woody ingredients Carbon Hydrogen Oxygen Nitrogen 



1. Wood 49-66 6-21 43-03 1-10 



2. Cork ..65-73 8-33 24-44 1-50 = 100 



3. Lycopod spores 64-80 8-73 20-29 6-18 = 100 



n. Coal products 



4. Anthracite 95-0 2-5 2-5 



5. Bituminous coal 81-2 5-5 12-5 0-8 



6. Brown coal 68-7 5-5 25-0 0-8 



7. Peat 59-5 5-5 330 2-0 



The relations of these woody materials and coals are still better exhibited 

 in the following table, giving the atomic proportions of the constituents, car- 

 bon being made 100 ; the atomic equivalents of carbon, hydrogen, and oxygen 

 being respectively 12, 1, 16. 



Carbon Hydrogen Oxygen 



1. Wood 100 150 65 



2. Cork 100 150 30 



3. Lycopod spores 100 166 24 



4. Anthracite 100 33 2 



5. Bituminous coal 100 83 12 



6. Brown coal 100 96 27 



7. Peat 100 112-5 40 



There was little ordinary bark in the beds of vegetable debris, since the 

 cortical part of Lycopods, Ferns, and Calamites is not of this nature ; although 

 nearer coal in constitution than true wood, bark resists alteration longer, and 

 is less easily converted into coal. The spores of Lycopods often retain their 

 amber-yellow color in the coal, although undoubtedly changed in constitu- 

 tion. Eesins, which are still nearer coal in the amount of carbon, but hold 

 less oxygen, are found mostly as resins in coal, especially when they are in 

 lumps or grains, but of somewhat altered composition. It is probable that, 

 in the making of bituminous coal, at least three fifths of the material of the 

 wood were lost ; and in the making of anthracite, about three fourths. Besides 

 this reduction to two fifths and one fourth by decomposition, there is a reduc- 

 tion in bulk by compression ; which, if only to one half, would make the 

 whole reduction of bulk to one fifth and one eighth. On this estimate, it 

 would take five feet in depth of compact vegetable debris to make one foot 

 of bituminous coal, and eight feet to make one of anthracite. For a bed of 

 pure anthracite 30 feet thick (like that at Wilkesbarre), the bed of vegeta- 

 tion should have been at least 240 feet thick. 



Anthracite coal is a result, according to most writers on the subject, of 

 the action of heat on bituminous coal, under pressure, attending an upturn- 

 ing of the rocks, the heat driving off nearly all volatile matters it could 

 develop, and so leaving a coke (the anthracite) behind. Made in this way, 



