I9II.] STEVENSON— FOR.AIATION OF COAL BEDS. 7 



last of five letters describing the peat deposits of northern Europe. 

 During his journey across Germany and the Baltic he had made 

 many exact observations on bogs ; he had followed the great level 

 marshes of the shores up the Weser river to the inland moors and 

 had found the same general features throughout. He describes the 

 slipping of the swamp into the river where, by swelling, it formed 

 a hard dry rampart which prevented all further ingress of water to 

 the swamp. He notes the great flood of Jutland, due to subsidence 

 of the boggy area, which is covered at low tide. On the island of 

 Bornholm in the Baltic is a swamp, surrounded by dunes, which 

 shows many prostrate firs, pointing toward the center of the bog. 

 These trees were overthrown by wind when the peat was soft. He 

 observed that dry peat produces very fine trees, those growing on 

 the peat ramparts of Oldenburg being beautiful. His observations 

 led him to assert that 



"The peat is the origin of the pit-coals or charbons de terre." He 

 states in a footnote that he had been anticipated by v. Beroldingen, 

 but that he had arrived at this conclusion independently while study- 

 ing the immense peat bogs of Bremen. He recalls that islands 

 had sunk below the ocean surface ; some of them might contain peat 

 as Bornholm. The waters would deposit matter on the peat giving 

 the shaly roof mingled with leaves of vegetables which covered the 

 peat at time of submergence. New sea deposits accumulated and the 

 peat, compressed, enclosed as in a laboratory, underwent further 

 change. He acknowledges that there may be difficulties in explain- 

 ing the transmutation of peat and the arrangement of some coal 

 beds, but he is confident that he is on the true road to the proper 

 explanation of the origin of coal and of its occurrence in beds. 



An anonymous writer,- in 1781, sums up the peatbog theory as 

 presented at that time. 



It is a received opinion amongst many naturalists, that coal was originally 

 peat moss, this fossil having been found in every intermediate state, nay, 

 sometimes with wood in it, and often with the marks of leaves, roots, 

 branches, and fruits of different plants, shrubs and trees, on the sides of 

 broken fragments. To this doctrine we were made proselyte's, being pre- 



* " A Tour to the Caves in the Environs of Ingleborough and Settle in 

 the West-Riding of Yorkshire," London, 1781, p. 68. 



7 



