SANDSTONES OF THE COAL MEASURES. 



471 



succession of very different strata 1 . It is difficult at this day for any geologist to deter- 

 mine the precise relations of all the upper strata in every part of the coal-field which 

 has been long worked, so much is the surface obscured, and so frequently have all 

 records perished. It is, however, sufficient to state generally, that in most parts the 

 upper measures consist of shale or clunch, with occasional courses of sandstone ; the 

 former being in much the greatest abundance, though the latter rises to the surface in 

 some places, as near Wednesbury and Bilston. The Wednesbury rock is one of the 

 highest in the series, occurring about 30 yards above the main coal, and being about 8 

 or 9 feet thick. That of Bilston lies immediately above the main coal, is 10 yards thick, 

 and occurs in both thick and thin beds, the former variety being used for building pur- 

 poses, the latter being a grit for whet and grindstones, &c. None of these sandstones 

 have any considerable horizontal extension. 



Without further explanation of the nature of the superjacent rocks, I at once refer 

 the reader to the shaft sections, p. 477, by comparing which he will perceive that great 

 variations in the lithological characters of the strata take place, even in very short hori- 

 zontal distances. Examining, for example, the order of the beds at the Bare Moor and 

 Corngreaves Collieries, distant from each other only half a mile, among other marked 

 discrepances between the various seams of coal, ironstone and measures, it will be per- 

 ceived, that the white sandstone rock, which immediately overlies the thick coaly is at 

 one pit 35 yards thick, at the other only 4 yards. (See table, Nos. 2 and 3.) 



Before we quit the consideration of the 10 yard coal-field, it should be stated, that 

 other masses of carbonaceous sandstone and grit, which rising up at intervals, throw 

 off on their flanks the coal measures, must be considered the inferior carboniferous strata, 

 properly so called, of this portion of the tract. 



The fine-grained, thickly bedded, light-coloured sandstone (an excellent building-stone) , 

 of which there are such splendid open quarries near Darlaston, north of Wednesbury, 

 clearly rises from beneath the 10 yard coal and immediately overlies the new mine coal 

 (the uppermost coal met with at Darlaston), the superior measures being absent. 

 These beds, about 70 feet thick, are very rich in fossil plants, the forms of which, as 

 marked by black carbonaceous matter, are beautifully contrasted with the light-coloured 

 sandstone in which they are imbedded 2 . The lowest of these sandstones is probably the 

 yellowish gritty rock of Gornals, between Dudley and Sedgley, which rises as a dome 



1 These shaft sections are selected from a multitude of documents, because they describe the structure of 

 those parts of the district which have been most recently opened out, and therefore most clearly indicate the 

 differences between the strata now developed and those formerly known. 



2 I made no collection of the plants of this coal-field, and am therefore unprepared to give a list. Many 

 of them, however, from both the sandstone and the shale, are already published in Lindley and Hutton's Fossil 

 Flora, and I have no doubt that in so rich a fossil herbarium some new species will be detected. A few splendid 

 examples, from the sandstone near Tipton, may be seen in the vestibules of the British Museum. The cabinets 

 of the Geological Society also contain specimens. 



3 n 2 



