82 



UPPER COAL MEASURES OF SHREWSBURY. 



no geologist could doubt, that the red rock immediately overlies the carboniferous strata; 

 and this conclusion has recently been established by sinkings, which having passed 

 through variegated shale of the Lower New Red Sandstone containing impressions of 

 plants, reached coal-bearing measures 1 . At Coedway, west of Alberbury, the opposite 

 extremity of the trough, the coal strata dip to the north-east, again passing beneath 

 red shale and sandstone, but the seams are of little value and have not been followed 

 upon the dip. (PL 29. fig. 9.) In most other portions of this trough there is no pos- 

 sibility of observing the precise relations of the coal measures to the overlying strata, 

 owing to an enormous accumulation of coarse detritus which overspreads the country. 

 The following account, therefore, of this tract is derived from observations made at 

 points where the coal has been worked along the tortuous line above indicated, and also 

 in the several bays and recesses of the older rocks to the south-east of Shrewsbury. 

 (See Map and view.) 



Where most developed, this formation contains three seams of coal, which, in de- 

 scending order, consist of half-yard, yard, and two-foot coals. The quality, thickness, 

 and even the number of these beds vary in different places, but it may be stated as a 

 general rule, that the lowest or two-foot coal is the best, the middle and upper seams 

 being for the most part pyritous and of inferior quality, particularly the yard coal, usually 

 termed " Stinkers." These coal beds are separated from each other by red, green, and 

 black shale, and clod, some portions of which have a saponaceous feel, as if charged 

 with magnesia, and thus they bear some resemblance to the variegated shale or marl 

 of the overlying New Red System. The intervening argillaceous beds, containing 

 occasionally a bed of sandstone, are of unequal thickness in distant parts of the trough, 

 but at Pontesbury they amount to about fifty yards. Owing to the unequal thicknesses 

 of the overlying strata, and also to numerous dislocations, the coal seams are neces- 

 sarily reached at various levels, the depths of the shafts increasing with the distance 

 from the natural outcrop of the coal. The deepest pits, or those furthest from the 

 edge of the field, are about ninety- five yards, whilst the shallowest or those nearest to 

 the hilly sides of the older rocks are not more than ten or twenty. Wherever the 

 measures have been examined between Pontesbury and Westbury, the three beds of 

 coal have been found ; but to the westward of the latter place one of them appears to 

 thin out. There is, however, a considerable space along which no trials have been 

 made, and the old works at Woolaston have been so long abandoned, that no correct 

 information is to be obtained respecting them. At Braggington and Coedway, the 

 western termination of the field, there are only two beds of coal worth working, the 



1 The trials alluded to were made by Mr. Hughes of Wellbatch, and the fragments of plants in the varie- 

 gated shale were recognised by Professor Lindley as being similar to those found in other coal-fields ; but un- 

 fortunately the specimens have been mislaid, and I am now unable to state their specific names. (See an ac- 

 count of plants found in red shale or marl above the coal measures of this age at Ardwick, near Manchester, 

 p. 88, note 1.) 



