I9I3-] STEVENSON— FORMATION OF COAL BEDS. 107 



forms belonging to those types, which show for lycopodium ashes 

 22 to 57 per cent, of alumina and lo to 14 per cent, of silica; for 

 Eqnisetum, no alumina but 41 to 70 per cent, of silica. The ash 

 of lycopods is 3.2 to 6 per cent, of the dried plant; of ferns, 2.75 

 to 7.56; of equiseta, 18.71 to 26.75. Stainier cites Wolff, Czapele 

 and Violette; lycopods have 4.70 to 6.10 per cent, of ash; conifers 

 contain very little ash in the wood but their bark and leaves have 

 much more, the former from i to 2 and the latter, from 5 to 7 per 

 cent. Coville^^^ has given a table of analyses, showing the quantity 

 of lime in leaves of trees, the percentage of the dried leaf varying 

 from 1.73 in the red oak to 4.38 in the ginkgo, the modern repre- 

 sentative of the Cordaites. 



Lycopods compose the greater part of most coals, other plants 

 giving the less part — though there are beds consisting very largely 

 of Cordaites. Dana has calculated that if the original ash were 

 1.66 of aluminium silicate and if the plant material lost three-fifths 

 of its mass during transformation into coal, there should remain 4.15 

 of silica and alumina, the total ash being 4.75 per cent, of the coal; 

 and this without introduction of any inorganic matter from without 

 by either wind or water, the whole being derived from the soil in 

 which the plants grew. Coal is known to consist very largely of 

 flattened stems, the cuticle alone remaining; the other parts of plants 

 have been almost wholly decomposed into a structureless pulp, of 

 which not a little may have been removed by solution. Bark and 

 leaves make up a very great part of the coal. One should expect 

 to find in ordinary coal not much less than 6 per cent, of ash, or 

 even more, in which silica and alumina should predominate greatly. 



Yet there is the all-important fact that some coal beds in areas of 

 several thousands of square miles have not merely less but even very 

 much less than the normal quantity of ash. The fact that many coal 

 beds have more is unimportant ; no one, be he allochthonist or 

 autochthonist, finds any difficulty in explaining the excess of in- 

 organic matter. But the Pittsburgh, Campbell's Creek, to make no 

 reference to some other beds, have less and the condition in those 



"^ F. V. Coville, " The Formation of Leafmold," Jotirn. Wash. Acad. Sci., 

 Vol. Ill, 1913, p. 80. 



