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



erosions and the mighty erect trees. The sand may have been 

 derived possibly from dunes such as those on the Rhine or Elbe. 



Lesquereux knows of no peat composed of fucoids and marine 

 plants. 



Jukes's'*" contribution to the discussion is not less important 

 than those by Rogers and Goeppert, as it is the first presentation of 

 the transport theory based on careful observation in an extended 

 area. It covered the ground so thoroughly that little aside from 

 detail or local coloring has been added since its publication. 



Two opinions exist respecting the origin of coal beds ; the first 

 is that trees and plants were drifted into lakes, estuaries and shallow 

 seas, where, becoming waterlogged, they sank to the bottom and 

 became covered by the other accunudations ; the second is that the 

 plants were not drifted but grew and perished on the spot where 

 they have formed the coal, just as our peat bogs would form coal 

 if long buried under a great mass of earthy matters. While he does 

 not purpose to range himself as an advocate of either opinion, he 

 finds difficulties in the way of the latter which make him hesitate 

 to accept it exclusively. These, observed in the South Staffordshire 

 coal-field, he gives in detail. 



1. The "rolls," "swells" or "horsebacks," which are ridge-like 

 accumulations of clay rising sometimes eight feet above the floor, 

 cannot be explained if the coal were formed at or above the level 

 of the water; but if coal and " ^well " alike were formed under 

 water no difficulty exists. 



2. The " rock faults " in the Thick coal. These are of two 

 kinds. One, which he has not seen, is due to erosion of the coal 

 after deposit, the hollow being filled with the material deposited on 

 the coal. The other comes from contemporaneous deposition of silt 

 or sand with the coal, so that they alternate at short intervals. The 

 coal encloses cakes, layers or masses of sandstone, more or less inter- 

 mingled with it. One such " fault " seen by Jukes, was 286 yards 

 wide and it had been followed 400 yards without reaching the end. 

 The upper part of the coal Ijed passes over the sandstone. At the 



■■'J. B. Jukes, Memoirs. Geol. Survey of Great Britain. "The South 

 Staffordshire Coal-tiekl,"' _'d cd., London, 1859, pp. 34-42, 44-49, 201-206. 

 The writer has not seen the first edition, published at least ten years earlier. 



34 



