THE MODE OF ORIGIN OF COAL^ 



EDWARD C. JEFFREY 



Harvard University 



The question of the manner of formation of coal has divided 

 geologists for over a hundred years and the problem is still disputed, 

 although at the present moment the weight of geological opinion 

 inclines in one direction. Where so much difference of opinion 

 has existed for so long a period, new evidence is obviously much 

 to be desired. The current views as to the origin of coal are based 

 mainly on a consideration of the stratigraphic evidence other than 

 that supplied by the coal alone. For example, much importance 

 has been attached to the presence of underclays beneath the coal 

 beds, as evidence of the existence of an ancient forest soil. Like- 

 wise a considerable amount of importance has been attached to 

 the existence of Stigmarian and other root or rootstock systems 

 in the substratum beneath the coal. Cornparatively little evidence 

 has been derived from the consideration of the coal itself. Where 

 such evidence has been available it has been of a contradictory 

 nature. For example, certain coals rich in bituminous matter, 

 such as cannels and the like, obviously present in their organiza- 

 tion strong resemblances to the muck formed in the bottoms of 

 modern lakes; that is, they consist, to a very large extent, of the 

 remains of spores and pollen. In other cases, much more rare, 

 concretions have been found in the coal, containing quantities 

 of often well-preserved vegetable remains. These remains are of 

 such a character and are related to one another in such a way, that 

 their clearest modern representative is the peat of existing peat 

 bogs. The two kinds of evidence derived from petrified coals on 

 the one hand or from the persistent structures in unmineralized 

 coals on the other appear to justify diametrically opposite views 

 as to the conditions of coal formation. Similar contradictions 



' ConirihiUions from the Plmnerogmnic Laboralorics of Harvard Univcrsily, No. 67. 



218 



