THE MODE OF ORIGIN OF COAL 



227 



as of terrestrial origin. The reasons for this beHef are drawn mainly 

 from the strata related to the coal beds, but it is somewhat generally 

 admitted that the character of the underclay or seatearth of a coal 

 bed is no more final proof of its condition of origin than the cover 

 of a book is necessarily convincing evidence as to the age and nature 

 of its contents. It becomes clear, as a result of the microscopic 

 examination of coals at large, that they cannot in general be derived 

 from ordinary peat, as they do not show the structure of coals 

 which by inclosed petrifications are known to be of peaty deriva- 



FiG. 13 



Fig. 14 



tion. The paralic or old seaboard coals of Great Britain and parts 

 of Continental Europe have a homogeneous structure, as has been 

 shown above in the case of Westphalian coals. This homogeneity 

 is not at all due to opacity of the thin sections, because even when 

 quite translucent, as when prepared by the improved methods 

 devised for the sectioning of coal, preliminarily described in the 

 article on "Supposed Algal Coals," cited earlier in the present 

 communication, they show no clear evidence of structure, except 

 so far as they contain fragments of carbonized wood, a condition 

 not uncommon in the paralic coals of British origin. 



Since it is generally admitted that coals containing large 

 quantities of spores are of aquatic origin, that is, are deposited in 

 open water, the question arises naturally, in view of the conditions 

 described above for ordinary bituminous coals, whether they are 



