98 



ORIGIN OF THE UPPER COAL MEASURES. 



great marine bay were formed near Manchester, its western margin being marked by 

 the zone of -carboniferous limestone which bounds the coal-fields of Oswestry, Chirk, 

 and Ruabon. An inspection of a general geological map of England will indicate the 

 extent of the area, which now appears as a vast trough of New Red Sandstone encircled 

 by carbonaceous deposits. (See wood-cut 4. p. 25.) Further observations upon the 

 origin of these coal-fields occur in the ensuing pages, particularly in the concluding part 

 of the eleventh chapter, where a small map will be found, explanatory of the probable 

 physical geography of this region during the accumulation of the carboniferous de- 

 posits. 



the Scotch deposit, the Salopian and Lancastrian strata afford proofs which do not exist in Scotland of their 

 geological place in the order of formations. In England they have been shown to constitute the youngest 

 carboniferous zone, because they graduate upwards into the New Red System. Now, if we are to be guided by 

 the nature of the fossils, we might be disposed also to infer that the beds at Burdie House, where no such strati- 

 graphical proofs exist, and which were once supposed to be of great antiquity, represent after all one of the 

 youngest accumulations of the carboniferous system. At all events, if we look at the question on a broad scale, 

 it is manifest from the position in which the Burdie House fossils have been discovered, not only in Lan- 

 cashire and Shropshire, but also in Staffordshire, that they appertain to those coal measures which overlie the 

 Millstone grit. (See chapter on the Dudley coal-field.) 



Mr. Leonard Horner has shown (Edin. New Phil. Journ., April, 1836,) that the mixed nature of the organic 

 remains at Burdie House compel us to suppose, that the carbonaceous strata at that place were accumulated in 

 an estuary and not exclusively in fresh water, although their contents had doubtless been poured forth by 

 streams. This subject will be beter understood after perusing the following pages, particularly the conclusion 

 of the eleventh chapter. 



