1913-] STEVENSON— FORMATION OF COAL BEDS. 151 



as are modern plants, the same organic materials being common to 

 them both. 



The vast extent of some coal fields is urged as a vital objection 

 to autochthony, because there are no delta-plains so great as the 

 larger coal fields of America or China. But this is not correct. 

 The Ganges-Indus flood plain area, like that of the Yang-tse-kiang, 

 is as great as the Appalachian basin and each has, in a considerable 

 part of its extent, conditions favoring accumulation of peat. Too 

 many writers commit the error of confounding extent of coal field 

 with extent of coal bed, and they refuse to believe that peat could 

 accumulate synchronously throughout the vast areas. Though in 

 no wise enamoured with modern causes, they appeal to them quickly 

 and cite the limited extent of modern peat bogs, none of which 

 resembles the Appalachian coal basin. But these writers forget or 

 do not know that coal was never accumulating at any one time 

 throughout a great field. Even at the time of the Pittsburgh coal 

 bed, with its probable area of more than 12,000 square miles, there 

 was not synchronous accumulation. During the earlier part of that 

 bed's history, as shown on an earlier page, coal was forming in less 

 than one third of the area; and during the later portion there was 

 no accumulation in perhaps half the area. So with other beds; 

 coal accumulated at separated localities, a few square miles or 

 hundreds of square miles in extent, sometimes near together but at 

 others far apart. During most of the time, conditions were un- 

 favorable to coal accumulation in probably by far the greater part 

 of the more extensive basins. One has to consider not vast sheets 

 of coal, but local deposits. The condition, most probably, was that 

 now seen in Holland, Belgium, northern France and northern Ger- 

 many, where the peat deposits are in separated areas, large and 

 small ; but they are contemporaneous and mark a definite horizon. 

 The important continuous area of Holland, Belgium and northern 

 France, now largely buried, is nearly as large as that on which any 

 bench of the Pittsburgh seems to have accumulated ; and the thick- 

 ness in some places is important. The Everglades of Florida is 

 almost as extensive and is only one of the many swamps in Florida, 

 where the distribution is very like that at some coal horizons in the 



