CARBONIFEROUS AGE. 361 



(e) resins and associated substances. The following is the composition 

 •of (1) dried wood in the mass ; (2) cork (the bark of Quercus suber) . 

 (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- 

 Jike 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 

 II. Coal Products. 



4. Authracite 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 33-0 2-0 



From this table, it appears that, in the change of woody fibre to 

 anthracite, the diminution in the amount of oxygen and hydrogen is 

 about ninety per cent., and that of the oxygen above ninety-five per 

 cent. ; in that to bituminous coal, the percentage of hydrogen is not 

 very much altered, but that of the oxygen is reduced over seventy per 

 cent. ; in that to brown coal, the percentage of the hydrogen is the 

 same nearly as in bituminous, but that of the oxygen is reduced only 

 forty to forty -five per cent. 



The relations of these woody materials and coals are still better 

 •exhibited in the following table, giving the atomic proportions of the 

 constituents, carbon being made one hundred ; 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 constitution. Resins, 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. 



The composition given above for dried wood is the mean of many analyses, by Pe- 

 tersen and Schodler (Liebig's Annalen, xvii. 141), as deduced by Bischof, corrected by 



