Geology of Coalhrook Dale. 453 



Conclusion. 



In the foregoing pages I have confined my observations solely to the geo- 

 logical description of the coal-field and the accompanying formations, with- 

 out reference to any hypothesis deducible from the details. I now propose 

 briefly to restate those facts, and afterwards to draw such conclusions as they 

 may appear to warrant. 



I intend, in the first place, to investigate the mode of deposition, and to 

 endeavour to ascertain the age of the coal formation ; secondly, to review 

 the nature and effects of those disturbances which have so powerfully affected 

 the several formations ; and, thirdly, to examine the nature of the agents, 

 which have since acted upon and modified the surface. 



'The first point involves the disputed question, whether the coal was formed 

 from vegetables which grew upon the spot now occupied by it, or from vege- 

 tables transported from a distance. 



It has been shown that each stratum of ironstone and several of the beds 

 of shale and sandstone are characterised by peculiar organic remains ; and 

 in some cases of a most decided nature. Thus the " v/hite flats" are distin- 

 guished by several new and peculiar species of Trilobites, and the Penney- 

 stone measures by Orthocera, Spirifers, and Nautili. From observations 

 upon those beds which admit of ready and extensive examination, it has been 

 ascertained, that the northern division of the coal-measures can be divided 

 into deposits alternately characterised by marine with some fluviatile and ter- 

 restrial remains, or by solely freshwater and land exuviae ; and it is not impro- 

 bable that a further inspection of the less exposed strata will enable future 

 observers to establish a greater number. At present I know of five decided 

 alternations, and of two which are doubtful, as only fishes have been found in 

 them. 



Terrestrial detritus .... Such at present appears to be the character of the thick and unproductive 

 strata lying above the Chance Penneystone. 



1 . Marine and Fluviatile. Chance Penneystone. 



Terrestrial and Fluviatile. Downwards from the Chance Penneystone to the fungus coal inclusive. 



2. Manne and Fluviatile. Bas above the blackstone coal. 

 Terrestrial Blackstone coal. 



3. Marine, Terrestrial, j j^j^^j^^^^^^^ i^^^^^^^^^^ 

 and Fluviatile J 



Terrestrial To the hailstone inclusive. 



4. Marine'', or Fluviatile. Bas over top coal. 

 Terrestrial, Fluviatile . . To the blue flats inclusive. 



