08 STEVENSON— FORMATION OF COAL BEDS. [April 21. 



Williamson,'" in discussing the characteristics of the great fossil 

 in the Owens college museum, remarked that that specimen had 

 removed finally all doubts respecting the relations of Stigmaria by 

 showing that plant to be the root of Sigillaria. The roots divide 

 only once and after division extend indefinitely. The stigmata are 

 lacking near the stem because the roots increased by exogenous 

 growth and the superficial portion with its rootlets was thrown ofif. 

 The trees grew in swampy ground as the swamp cypress does in 

 American swamps. The gymnospermous plants grew on drier 

 ground. The particular tree under consideration must have been 

 at least 100 feet high. When it died, decay continued downward to 

 the point shown and then was checked probably because the lower 

 portion was buried in sediment and protected from air. Thence 

 decay proceeded very slowly until the woody tissue of even the root 

 disappeared. Meanwhile, the surrounding rock had hardened and 

 had taken a cast of the stem and roots. The surface sank beneath 

 the water and soft sand filled the cavity; thus the roots have their 

 original form. 



Fayol, after si)ending man}' years in study of the basin of Com- 

 mentry, published his results in a remarkable work, which is un- 

 excelled as a record of detailed observation. This work presented 

 the grounds on which, several years before, its author had based bis 

 theory respecting the formation of coal beds. The positive posi- 

 tion taken in favor of the transport theory and the clearness, with 

 which the observations were ofi:'ered, caused a notable reaction in 

 favor of the doctrine that coal beds are formed of transported vege- 

 table matter. A year after publication of the work, Fayol gave a 

 summary of the delta theory, as he termed it, at the summer meeting 

 of the Geological Society, when several members of the society com- 

 mented on the theory. This resume, being the later presentation, is 

 the basis of the present svno])sis.'' 



The theory is based on the laws of sedimentation, as observed in 



'"W. C. Williain.soii, "On the Fossil Trees of the Coal Measures," 

 Trims. Manchester Gcol. Soc.. Vol. XIX., 1888, pp. 381-387. 



" II. F'ayol, " fitndes siir Ic terrain liouillc dc Commentry," F". partie. 

 " Lithologic et stratigrai)hie." lUiU. Soc. M in. Ind. St-Etiennc, 2'"" Ser., 

 XV., Liv., III., IV., 1RS7; "Resume de la theorie des deltas et histoire du 

 bassin dc Coninuntry," IhdI. Geol. Sue. France, 3"" Ser., XVI., pp. 968-978. 



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