CARBONIFEROUS AGE. 365 



5. Potash is present in all terrestrial vegetation, and soda more 

 sparingly ; but, as the salts of these alkalies are soluble, they would 

 mainly disappear in the course of the decomposition. 



6. Traces of sulphur occur in wood, as well as in animal matters, 

 which therefore would be present in the accumulating beds. This 

 sulphur, by combination with iron, would have formed pyrite, — a 

 common impurity in coal-beds. But it seems also to exist in coal in 

 a resin or some other organic compound. Nitrogen is present in 

 coals, but under what condition is not known. 



Impurities were also introduced, as earth or clay, by waters, as the 

 occasional intercalations of shale show. Even the winds transport 

 dust, and may have contributed to the earthy ingredients of the coal. 



Waters may also have carried in other ingredients in solution, as 

 oxyd of iron, in combination with either carbonic acid, sulphuric acid, 

 or some organic acid; for iron is carried in these ways (mainly the 

 last) into all marshy or low regions, from the hills around, being 

 derived from the decomposition of iron-bearing minerals. Sulphate 

 of iron would lose its oxygen from contact with decomposing vegeta- 

 tion, and become sulphid of iron ; and this is another source of 

 pyrite. In the change, the oxygen takes carbon from the coal or de- 

 composing plants, and forms carbonic acid, which escapes, and leaves 

 only sulphur and iron, to make sulphid of iron, or pyrite. The 

 carbonic acid made in the change of wood to coal was in part utilized 

 by its combination with iron in the protoxyd state, making carbonate 

 of iron, the ordinary constituent of the iron ore of coal regions. 

 Sesquioxyd of iron, in contact with decomposing vegetation, becomes 

 protoxyd, which then unites with the escaping carbonic acid. 



The following are analyses of the ash of Lycopods (1, 2), Ferns (3 to 6), Equiseta 

 (7, 8), Conifer (9), Moss of the genus Sphagnum (10), and Chara (11). 





KO 



NaO 



CaO 



MgO 



Fe 2 03 



Mn30* 



AP03 



P05 



S03 



Si02 



CI 



1. Lye. clavatum 



. 3190 



2-68 



413 



5-89 



600 



- 



22-20 



7-30 



3-55 



1301 



- 



2. Lye. clavatum 



. 25-69 



174 



7-96 



651 



230 



253 



26-65 



536 



4-90 



13-94 



313 



3. Aspl. filix . 



. 45-5 



5-2 



?9 



74 



1-5 



- 



- 



20-0 



6-8 



22 



4-6 



4. Aspid. filix . 



39-80 



5 31 



18.74 



8-28 



0-97 



- 



- 



2-56 



5-40 



4-38 



14-72 



5. Osm. spicant 



. 23-65 



3-33 



409 



6-47 



117 



- 



- 



1-76 



1-29 



53 00 



5-82 



6. Pteria aquilina 



1935 



4-78 



12-55 



2-30 



3-94 



- 



- 



515 



1-77 



43 65 



6-20 



7. Eq. arvense . 



. 1916 



0-48 



17 20 



2-84 



0-72 



- 



- 



2-79 



10 18 



4173 



6-26 



8 Eq. Telmateia 



. 8-01 



0-63 



8-63 



1-81 



1-42 



- 



- 



1-37 



283 



70-64 



5-59 



9. Pinus abiea . 



. 12-84 



5-64 



58-27 



2-81 



160 



tr. 



tr. 



260 



1-60 



12-55 



2-06 



10 Sphafr commune 802 



12-40 



317 



4 92 



6 35 



tr. 



689 



106 



4-33 



41-69 



1209 



11. Chara foetida 



. 0-85 



0-44 



95 35 



0-99 



0-67 



- 



- 



0.54 



0-42 



1-22 



016 



Analysis 1, is by Ritthnusen : 2, Aderholt; 3, A. Weinhold; 4, Struckmann; 5, 6, 9, 

 Malaguti & Durocher; 7, 8, E. Wittig; 10, H. Vohl.; 11, Schulz-Fleet. 



In the analyses that have been made of Lycopods, the amount of ash is 3-2 to 6 per 

 cent, in weight of the dried plant; of Ferns, 2-75 to 7-56 per cent. : of Equisetum airense, 

 18-71 per cent.; of Eq. Telmateia, 2675 per cent. ; of Conifers, mostly less than 2 per 

 cent. ; of Chara foztida, 31-33 per cent. ; of Fungi, 3-10 to 9-5 per cent. ; of Lichens, 



