MurchisorCs Silurian System, 217 



ductive coal-fields, rising from beneath a cover of new red sandstone. 

 I do not throw ont such suggestions as an inducement to proprietors, 

 north of Shrewsbury, to endeavour to penetrate the thick and massive 

 deposits of which the overlying new red system is composed, although 

 it is by no means impossible that a coal-field may there lie hidden, 

 which when the more accessible coal strata in other tracts shall have 

 been exhausted, may prove of value to future generations. Such infer- 

 ence is rendered more probable by the observations in the next chapter, 

 which show, that a band of coal measures of the same" age, passing 

 similarly upwards into the new red sandstone, and containing a lime- 

 stone identical with this of the Shrewsbury plain, distinctly overlies the 

 edges of the most productive 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 appli- 

 cation 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 

 tiling for the geologist to show the natural position of the coal, and 

 another for the miner to determine where it has been locally accumu- 

 lated 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 con- 

 tinue to thin out in their extension beneath the red sandstone, then, 

 indeed, deep sinkings in the central parts of the basin north of Shrews- 

 bury 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 red sandstone, point to the 

 necessity of much circumspection in all such operations. 



Passing from these practical hints, I would conclude with a few gene- 

 ral 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 cha- 

 racter and high geological interest, in aiding the proofs of a descending 

 passage from the lower new red sandstone into the carboniferous sys- 

 tem. 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, it was the 



