I9II-] STEVEXSOX— FORMATION OF COAL BEDS. 19 



dance and fermentation necessarily followed under the covering of 

 water and sediment. It is unimportant to determine whether the 

 water was fresh or salt. 



In this wav, he sees no ditificulty in accounting for accumula- 

 tion of stone coal deposits, even those of Saint-Etienne. which are 

 60 fathoms thick. He emphasizes the fact that the particular vege- 

 tation of the stone coal period produced colossal stems. 



Link-® was the first to study the texture relations of coals. He 

 observes that two theories had been offered to account for the origin 

 of coal beds ; that of driftage does not commend itself to him, but 

 that referring the coal beds to ancient peat bogs appears more rea- 

 sonable. After summarizing the opinions of v. Beroldingen, de 

 Luc, Steft'ens, Hutton and Leonhardt, he presents the results of his 

 own investigations. \'on Buch, feeling perplexed by some recent 

 publications, had given him some specimens of coal from Bogota 

 and had asked that he study them microscopically. The composition 

 of one of those coals so resembled that of peat that he was led to a 

 wide study of coals and peats from several horizons and regions. 



In all peats, whether loose or compact, cell tissues form the 

 body of the mass ; the dift'erence in ciuality of the peats being due 

 probably to dift'erence in the plants ; the stone coals resemble peat 

 in structure, some recalling the comparatively loose LiniDii peat 

 used as fuel in Berlin, while others are more like the dense, almost 

 wood-like peat from Pomerania; the Mesozoic coals vary, one from 

 the ]\Iuschelkalk closely resembles peat, but the Liassic coals appear 

 to be composed largely of woody fiber; the brown coal of Green- 

 land is like the LiniDii peat, while that of ^leissner in Saxony is 

 similar to the dense Pomeranian material. 



Link observes two quarto plates illustrating the vegetable struc- 

 tures observed in each of the peats and coals examined. 



Logan's-^ notable memoir on underclays appeared in 1841. He 



^ H. Link, " Uber den Ursprung der Steinkohlen und Braunkolilcn nach 

 mikroskopischen Untersuchungen,"' Abliandlnngen d. k. Akad. d. Hiss. 

 Berlin. 1838, pp. 33-44- 



^W. E. Logan, "On the Character of the Beds of Clay Lyhig Immedi- 

 ately below the Coal Seams of South Wales," Proc. Geol. Soc. London, 

 Vol. III., pp. 275, 276. 



19 



