19II-] STEVEXSOX— FORMATION OF COAL BEDS. 37 



Measures, coals included, were deposited by one connected operation 

 of the same forces acting in obedience to the same physical laws on 

 similar but slightly differing materials, through an indefinite but 

 immensely long period of time." 



Dawson spent many years in investigation of the Acadian coal 

 fields, but devoted his attention especially to the South Joggins 

 region where exposures are almost complete in a section of more 

 than ii.ooo feet thickness. He visited that locality with Lyell in 

 1852 and 1853 and afterwards made detailed study of each coal bed 

 as well as of each ancient soil, subjecting samples from all to careful 

 macroscopic and microscopic examination. The results of his 

 studies were given in several memoirs and the details were pub- 

 lished in the second edition of " Acadian Geology." In his first 

 elaborate memoir'*^ he called attention to the gradual passage from 

 coal to the roof shales through laminae composed of coaled leaves 

 and flattened trunks, separated by clay. He expresses the opinion 

 that erect forests explain to some extent the accumulation in situ. 

 The sandstone casts of Sigillaricc are enclosed in bark converted 

 into caking bituminous coal, while remains of the woody matter 

 remain as mineral charcoal at the bottom of the cast. A series of 

 such stumps with flattened bark and prostrate trunks may consti- 

 tute a rudimentary bed of coal, of which many occur in the South 

 Joggins section. He is convinced that the structure of the coal 

 accords with the view that it accumulated by growth and not by 

 driftage and that accumulation was very slow. He regards Sigil- 

 laria and Calaiiiitcs as the chief contributors to the formation of 

 coal. The woody matter remains mostly as mineral charcoal, while 

 the cortex and such other portions as were submerged gave the 

 compact coal. This memoir is concerned, for the most part, with 

 the origin of coal. 



In a later memoir,''- he considered especially the subject of accu- 

 mulation. After describing the formations and the physical condi- 



" J. \\'. Dawson. " On the Vegetable Structures in Coal,"' O. J. G. S., 

 Vol. XV., 1859. pp. 638. 640. 



^' '■ On Conditions of the Deposition of Coal, more Especially as Illus- 

 trated by the Coal Formations of Nova Scotia and New Brunswick," Q. J. 

 G. S., Vol. XXII., 1866, pp. 95-104. 



37 



