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GEOLOGY chosen as the base of the upper sub-division. The unequal rate of deposition of the Coal-measures is accentuated in the Pottery Coalfield, where the strata between the Bassey Mine and Winpenny Coals approxi- mate to 1,200 yards at Shelton, whereas at Apedale, 4 miles to the west, they are under 800 yards thick, from which the rate of diminu- tion can be calculated to be about i in 17, equivalent to a gradient of over 3 degrees. Below the Winpenny the coal seams are of small value, but one called the Crabtree Coal, a few yards above the First Grit, is well known from its shale roof, yielding in all four areas abundant specimens of Goniatites, Pterinopecten and Lingula. The strata below the Winpenny occur in all the four areas, while they constitute the entire measures of the small basin of Shaffalong and a considerable portion of that of Cheadle and Goldsitch Moss. The strata enclosing the coals and ironstones consist of clays, marls, fireclays and shales with an occasional band of sandstone very impersistent and of no great thickness. The colour is generally a dull grey excepting a few bands of intensely black shales or an occasional impersistent stratum of a red colour. The absence of any great mass of hard rocks is reflected in the scenery, which is tame and uninteresting, but whenever a ridge breaks the monotony it is almost certainly found to consist of one of the bands of sandstone, and inasmuch as the sandy material is more prevalent in the north so the ridgy character of the coalfield, as in the Norton district, becomes more pronounced. The numerous coal seams between the Ash and Winpenny Coals constitute the chief seams of the Pottery Coalfield. They include varieties suitable for house purposes, for making gas and coke, for raising steam, or for use in the arts and manufactures of the district. The only ironstone at present raised is the Burnwood Stone of the variety known as semi- blackband. In the adjacent Cheadle Coalfield there are also several valuable coal seams, but they have not been satisfactorily identified with those of the Pottery Coalfield. A peculiarity in the distribution of the coals in the Pottery area is the fact that certain easily recognized seams, which are gas or coking coals in the western area, rapidly lose a large quantity of their bituminous matter when traced eastward, until they become house or steam coals. The commonest fossils are molluscs, of which the most abundant belong to the genus Carbonicola (Anthracosia)^ regarded as a freshwater, mud-loving animal. They occur in great profusion in the ironstones and shales overlying the Cockshead, Ten-feet and other coals, forming the so-called ' mussel or cockle bands ' of the miner. In comparison with the Middle Coal-measures, fish remains may be said to be rare ; of great interest are fragments of various parts of the skeleton of the amphibian Loxomma, met with in the shale overlying the Cockshead Coal at Adderley Green. Within recent years a number of thin bands of shales and cal- careous nodules containing marine organisms have been brought to light at no less than seven widely separated horizons ; the lowest, as previ- 13