ORGANIC REMAINS. 



103 



most part in the former condition, and the various courses of it are known under these names : New 

 Mine (peculiar to Madeley) Crawstone, and Penny stone, occurringgenerally : White and Blue Flats, 

 in the north and middle districts ; Chance Stone and Yellow /Stone, in the middle tract ; Ball stone, 

 B?*ick stone, and Blachstone, in the northern district. The Ragged Robins and Chance Penny stone 

 are of irregular occurrence. Of these twelve courses of ironstone more than seven are never 

 found in one locality. In taking a general survey, it may be said, that both the coal and iron are 

 much more abundant in the northern than in the southern part of the field. Mr. Prestwich has 

 indeed remarked the difficulty of identifying any particular stratum of the upper portion over a con- 

 siderable area, whilst he has found the lower measures stronger and more persistent. Among the 

 various rocks which alternate with the coal and iron, the stone of the Willey or Shirlot obelisk is an 

 example of a coarse variety, while the sandstone occurring immediately above the u flint coal is of 

 remarkably fine quality for architectural purposes, the monument erected to the late Duke of Suther- 

 land on Lilleshall Hill being built of it. Some of the grits associated with the lower coals pass 

 into coarse conglomerates containing fragments of quartz rock, trap, Silurian and Cambrian rocks ; 

 and in the lower measures some of the beds of shale afford excellent fire clay, long celebrated in 

 the manufacture of pipes and pottery. 



The ores of iron are peroxides in the sandstone, argillaceous carbonates in the shale, and sulphurets 

 in the coal. The sulphuret of iron is the most abundant mineral, and next to it the sulphuret of 

 zinc or blende, which appears in the ironstone nodules of the Pennystone measures both in granular 

 and crystalline form. Petroleum is of constant occurrence in the upper as well as lower measures ', the 

 chief source of this mineral at Coal Port, which formerly afforded one hogshead per diem, being in 

 a thick-bedded sandstone of the upper measures. This supply has, however, much decreased with 

 the opening of the new coal works. Other tar wells have been discovered in the lower coals at 

 Prior's Lee. In some pits, as at Dawley and the Dingle, the petroleum exudes in such quantities 

 that the works are necessarily boarded up or "plated" to prevent its infiltration upon the workmen. 

 Besides these minerals titanium exists in the iron ore, crystals of it having been detected in the refuse 

 slags. 



The general relations of the carboniferous deposits to the contiguous formations are 

 explained in PL 29. figs. 11 and 16. 



Organic Remains. 



To the zeal of Mr. Anstice, of Madeley, in collecting the varied and curious or- 

 ganic remains of this coal-field, geologists are signally indebted. Although acquainted 

 with the riches of his stores, the use of which he liberally offered to me as far back as 

 the year 1832, 1 felt that these numerous and beautiful specimens merited the attention 

 of a separate historian. Shortly after, the district falling under the notice of Mr. Prest- 

 wich, the desired object was attained, and all the most characteristic of the unpublished 

 fossils will, I trust, shortly appear in his memoir in the Geological Transactions. 



The collection formed by Mr. Prestwich, both by his own exertions and the contributions of 

 Mr. Anstice and others, is very numerous. The terrestrial plants alone amount to between forty 

 and fifty species, composed of Euphorbiacece, Dy cotyledons of doubtful affinity, Palmce, Monocoty- 



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