96 PRACTICAL HINTS CONCERNING THE SHREWSBURY COAL-FIELD. 



of all the Salopian coal-fields ; and hence it is no strained inference that carbonaceous 

 masses equally thick may also be found expanding beneath this upper coal of Shrewsbury, 

 though most probably at some distance from the outcrop, and if so, necessarily at vast 

 depths under the New Red Sandstone of the plain of Shrewsbury. Observations leading 

 to similar inferences, and extending their application to other extensive tracts in the 

 central counties, will be found in subsequent chapters. Again, however, I would repeat 

 that much caution and many preliminary trials towards the edges of this great basin are 

 required before such speculations are attempted, since it is one thing for the geologist 

 to show the natural position of the coal , and another for the miner to determine where 

 it has been locally accumulated in any quantity worthy of the industry of man. This 

 latter point may be most safely ascertained by following the coal seams upon their dip 

 from the points where they are now known, and if they continue to thin out in their 

 extension beneath the red sandstone, then, indeed, deep sinkings in the central parts 

 of the basin north of Shrewsbury would be absurd. The proofs which will be adduced 

 in the eleventh chapter, of the thinning out of the coal seams of the Oswestry field where 

 they dip under the Lower New Red Sandstone, point to the necessity of much circum- 

 spection in all such operations. 



Passing from these practical hints, I would conclude with a few general theoretical 

 reflections. These poor and thin stripes of coal measures have been dwelt upon in some 

 detail, and similar patches will again be adverted to in the following chapter, on account 

 of their peculiar character and high geological interest, in aiding the proofs of a de- 

 scending passage from the Lower New Red Sandstone into the Carboniferous System. 

 Constituting the youngest member of that system, they fill up an interval in geological 

 chronology, precisely in that portion of the series in which much obscurity previously 

 existed ; for, with the exceptions in the North of England pointed out by Professor 

 Sedgwick 1 , it was the prevalent belief of geologists when my researches commenced 

 (1831), that in all other parts of England a great break existed between the New Red 

 System and the coal measures, the phenomena of disruption in the environs of Bristol 

 being assumed as the true types or patterns of the general order. These upper coal 

 measures of Shropshire are further remarkable in bringing to light, for the first time in 

 Great Britain, a peculiar limestone interstratified with coal seams, and which from its 

 prevalent organic remains and mineral composition I have referred to freshwater origin. 

 Though never exceeding eight or nine feet in thickness, and sometimes dwindling away 

 to two feet, this band is so remarkably persistent, that when followed along all its 

 sinuosities the length of its course is about forty miles ; and even in a straight line from 

 Coedway, near the Breidden Hills, to Tasley and Coughley, near Bridgenorth, where it 

 will presently be described, the distance is not less than twenty-five miles ; and yet 

 throughout such a space this little stratum preserves the same structure, and contains 



1 See Geological Transactions, vol. iii. part I. 



